Teses / dissertações sobre o tema "Baryons"
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1
Urlichs, Konrad. "Baryons and baryonic matter in four-fermion interaction models". [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=983572755.
2
Ouared, Mohamed Rafik. "Étude des propriétés de production et de désintégration du baryon charme lambda C dans les interactions PP à 400 GeV/c". Paris 11, 1987. http://www.theses.fr/1987PA112191.
3
Haupt, Christian. "Electromagnetic properties of baryons". [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980373271.
4
Drach, Vincent. "Fermions twistés dynamiques et spectroscopie des baryons". Phd thesis, Grenoble, 2010. http://www.theses.fr/2010GRENY015.
Resumo:
Ce travail s'intéresse au calcul de la masse des baryons à partir de la théorie décrivant l'interaction forte : la chromodynamique quantique (QCD). Cette théorie régit l'interaction entre les quarks et l es gluons et a pu durant ces dernières décennies être vérifiée à haute énergie grâce à l'une de ses propriétés : la liberté asymptoti que. Celle-ci prédit que les calculs perturbatifs sont valides à haute énergie car la constante de couplage tend vers zéro. Les quantités physiques régissant la physique à basse énergie nécessitent quant à elles un traitement non pertubatif et font l'objet de ce travail. La seule approche con nue permettant de calculer ces observables en contrôlant tous les effets systématiques est la QCD sur réseau. Le C hapitre 1 est une introduction au formalisme de la QCD et à sa formulation discrétisée. Le second chapitre est dédié à la discréti sation particulière utilisée au sein de la collaboration Europan Twisted Mass (ETM). Le Chapitre 3 met en place la technologie nécessaire au calcul des masses des hadrons. L'estimation des intégrales fonctionnelles en utilisant le calcul massi vement parallèle sur des Super Calculateurs est décrite dans le Chapitre 4. La production de configurations de jauge sur ce type d'architecture constitue une part importante du travail effectué durant cette thèse. Le Chapitre 5 est dédié à la formulation des théories effectives dites de pertubations chirales. Les Chapitres 6 et 7 sont consacrés aux baryons légers et étranges. Les eff ets systématiques ainsi que les extrapolations chirales sont largement discutésThe aim of this work is an ab initio computation of the baryon masses starting from quantum chromodynamics (QCD). This theory describe the interaction betw een quarks and gluons and has been established at high energy thanks to one of its fundamental properties : the asymptotic freedom. This property predicts th at the running coupling constant tends to zero at high energy and thus that perturbative expansions in the coupling constant are justified in this regime. On the contrary the low energy dynamics can only be understood in terms of a non perturbative approach. To date, the only known method that allows the computat ion of observables in this regime together with a control of its systematic effects is called lattice QCD. It consists in formulating the theory on an Eucl idean space-time and to evaluating numerically suitable functional integrals. The chapter 1 and 2 are an introduction to the QCD in the continuum and on a discrete space time. The chapter 3 deals with the techniques needed to build hadronic correlator starting from gauge configuration. We then discuss how we determine hadron masses and their statistical errors. The numerical estimation of functional integral is explained in chapter 4. It is stressed that it requires sophisticated algorithm and massive parallel computating on BlueGene type architecture. Gauge configuration production is an important part of the work realized during my Ph. D. Chapter 5 is a critical review on chiral perturbation theory in the baryon sector. Th e chapters 6 and 7 are devoted to the analyze in the light and strange baryon sector. Systematics and chiral extrapolation are extensively discussed
5
Drach, Vincent. "Fermions twistés dynamiques et spectroscopie des baryons". Phd thesis, Université de Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00633497.
Resumo:
Ce travail s'intéresse au calcul de la masse des baryons à partir de la théorie décrivant l'interaction forte : la chromodynamique quantique (QCD). Cette théorie régit l'interaction entre les quarks et l es gluons et a pu durant ces dernières décennies être vérifiée à haute énergie grâce à l'une de ses propriétés : la liberté asymptoti que. Celle-ci prédit que les calculs perturbatifs sont valides à haute énergie car la constante de couplage tend vers zéro. Les quantités physiques régissant la physique à basse énergie nécessitent quant à elles un traitement non pertubatif et font l'objet de ce travail. La seule approche con nue permettant de calculer ces observables en contrôlant tous les effets systématiques est la QCD sur réseau. Le C hapitre 1 est une introduction au formalisme de la QCD et à sa formulation discrétisée. Le second chapitre est dédié à la discréti sation particulière utilisée au sein de la collaboration Europan Twisted Mass (ETM). Le Chapitre 3 met en place la technologie nécessaire au calcul des masses des hadrons. L'estimation des intégrales fonctionnelles en utilisant le calcul massi vement parallèle sur des Super Calculateurs est décrite dans le Chapitre 4. La production de configurations de jauge sur ce type d'architecture constitue une part importante du travail effectué durant cette thèse. Le Chapitre 5 est dédié à la formulation des théories effectives dites de pertubations chirales. Les Chapitres 6 et 7 sont consacrés aux baryons légers et étranges. Les eff ets systématiques ainsi que les extrapolations chirales sont largement discutés.
6
Habibi, Farhang. "Searching for missing baryons through scintillation". Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00625486.
Resumo:
Cool molecular hydrogen H2 may be the ultimate possible constituent to the Milky-Way missing baryon. We describe a new way to search for such transparent matter in the Galactic disc and halo, through the diffractive and refractive effects on the light of background stars. By simulating the phase delay induced by a turbulent medium, we computed the corresponding illumination pattern on the earth for an extended source and a given passband. We show that in favorable cases, the light of a background star can be subjected to stochastic fluctuations of the order of a few percent at a characteristic time scale of a few minutes. We have searched for scintillation induced by molecular gas in visible dark nebulae as well as by hypothetical halo clumpuscules of cool molecular hydrogen (H2_He) during two nights, using the NTT telescope and the IR SOFI detector. Amongst a few thousands of monitored stars, we found one light-curve that is compatible with a strong scintillation effect through a turbulent structure in the B68 nebula. Because no candidate were found toward the SMC, we are able to establish upper limits on the contribution of gas clumpuscules to the Galactic halo mass. We show that the short time-scale monitoring of a few 10^6 star _ hour in the visible band with a >4 m telescope and a fast readout camera should allow one to interestingly quantify or constrain the contribution of turbulent molecular gas to the Galactic halo.
7
Avenarius, Christoph. "The spin structure of the baryons". Thesis, University of Oxford, 1992. http://ora.ox.ac.uk/objects/uuid:448e060b-085d-449f-b33a-dd3913093d6d.
Resumo:
Baryons are considered in the Nonrelativistic Quark Model (NQM) to be bound states of three valence quarks. Each quark has two possible spin eigenstates in the restframe of the baryon whose spin is fully carried by quarks. The baryon wavefunctions are connected through SU(6) symmetry rotations. For a long time, the measured magnetic moments of the baryons appeared to be in agreement with the NQM predictions. However, recent experiments which are examining the spin structure of the baryons show the failure of several NQM predictions. The so-called 'spin crisis' arose from the interpretation of the EMC deep inelastic scattering measurement of ∫ gp1 that the quark spins in the proton appeared to sum up to (almost) zero. In this thesis it will be demonstrated that the spin problem is not a phenomenon restricted to quasi-massless current quarks in the high energy limit. Symmetry arguments are used to examine the baryon magnetic moments and reveal that we can observe massive but pointhke constituent quarks, with a characteristic mass ratio mu = md ≃ 2andfrasl;3ms. Surprisingly they do not contribute much to the baryon spin either. This analysis is free of the ambiguity arising from the UA(1} gluon anomaly which makes it impossible to calculate precisely the spin sum of the current quarks. One important finding in our analysis is the observation that the effects of SU(6) breaking hyperfine spin-spin interactions (which cause well-known splittings in the baryon masses) can be seen in the environment dependence of the constituent quark masses. The effective mass of a quark cannot be independent of its surrounding energy since the mass of the baryon is distributed amongst its constituents. Consistent with the hypothesis that different quark masses do not impose SU(3) breaking on the baryon wavefunctions is the observation of induced 'second class' form factors. The way in which SU(3) breaking alters the gAandfrasl;gV ratios in semileptonic hyperon decays will be discussed and strong evidence for a new value of F/D is given, which is close to its SU(6) value. This value is derived independently from the baryon β-decays and from their magnetic moments. Dynamical models are discussed which might explain the observed polarised strangeness 'inside' the proton, and the almost vanishing quark spin sum.
8
MERLI, ANDREA. "SEARCH FOR CP VIOLATION IN BARYONS". Doctoral thesis, Università degli Studi di Milano, 2019. http://hdl.handle.net/2434/656029.
Resumo:
In the past, flavour physics has driven indirect discoveries of new particles through precision measurements of other processes before the actual particles could be produced directly.
For example the discovery of the differences in the behaviour of matter and antimatter, CP violation (CPV), has led to the explanation of flavour mixing with three families of quarks; the absence of the decay{KL}{mumu} decay drove the prediction of the cquark quark trough the GIM mechanism; the measurement of the Bd mixing allowed for the prediction of high mass of the quark quark.
The asymmetry between matter and antimatter behaviour is related to the violation of the CP symmetry, where $C$ and $P$ are the charge-conjugation and parity operators. CPV is accommodated in the Standard Model (SM) of particle physics by the Cabibbo-Kobayashi-Maskawa (CKM) mechanism that describes the transitions between up- and down-type quarks, in which quark decays proceed by the emission of a virtual W boson and where the phases of the couplings change sign between quarks and antiquarks.
A significant excess of CPV with respect to the theoretical predictions would represent a proof of new physics beyond the SM (BSM).
The experiments BaBar and Belle have systematically studied the Bd and Bpm mesons. The heavy baryon sector (ie containing the quark quark) still remains largely unexplored.
Given the large production of heavy baryons at lhcb, precision measurements have become possible in this field. Moreover, the interest of the scientific community is growing on heavy baryons: the last measurement on $lvertVub
vert$ in the channel decay{Lb}{protonmun
eub} and the discovery of the pentaquark in the channel decay{Lb}{jpsiprotonKm} are only few relevant examples.
Actually the theory describes very well, within the experimental error, the CPV mechanism so far observed in meson decays. Since in the mesons and baryons decays the quark transitions are the same, the CKM theory predicts CPV also in the baryon sector, which has never been observed so far. It is important to measure CPV also in baryons to check if the mechanisms through which it is generated is the same as mesons.
We know that CPV is a key ingredient for baryogenesis, but the CKM mechanism cannot explain it quantitatively. New sources of CPV are necessary to explain baryogenesis.
The search for electric dipole moment (EDM) of baryons represents a powerful probe for new sources of CPV and new physics beyond the Standard Model. In particular, it is sensitive to flavour diagonal CPV contributions that are predicted to be minuscule in the SM.
The existence of permanent EDMs requires
the violation of parity ($P$) and time reversal ($T$) symmetries and thus, relying on the validity of the CPT theorem,
the violation of CP symmetry.
These measurements are not foreseen in the physics program of the lhcb experiment dedicated to the study of the CP violation of heavy hadron via flavour-changing observables, and require new instrumentation.
9
Niemiec, Anna. "Influence of the environment on galaxy formation". Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0260/document.
Resumo:
Dans le modèle de formation hiérarchique des structures, les amas de galaxies se forment et grandissent par l'accrétion de groupes plus petits ou de galaxies isolées. Dans ce scenario, comprendre comment les galaxies accrétées interagissent avec cet environnement très dense est une étape importante pour comprendre le schéma global de l'évolution des galaxies et de la formation des structures. En effet, pendant leur chute au coeur de l'amas, les galaxies sont sujettes à diverses interactions avec l'amas hôte, au niveau de leur composante baryonique aussi bien que matière noire, et ces interactions vont modifier les propriétés de la galaxie. Au niveau de la matière noire, les simulations numériques suggèrent que la friction dynamique fait plonger les galaxies vers le centre de l'amas, et que les forces de marée exercées par l'hôte peuvent arracher une partie de la matière de la galaxie, et même détruire celle-ci. Ce processus, au cours duquel une partie de la matière noire de la galaxie est arrachée, est appelé stripping. La détection du stripping de matière noire contient d'importantes informations sur l'évolution des groupes et des amas. Le travail principal de cette thèse se concentre sur l'étude des galaxies dans les amas, et en particulier sur l'étude du stripping des galaxies par les forces de marées des amas. Les profils de densité des halos sont mesurés à l’aide de l’effet de lentille gravitationnelle faible, en utilisant les catalogues de formes de galaxies des relevés CFHTLenS, CFHT Stripe 82 et DES-SV, alliés au catalogue d’amas redMaPPerGalaxy clusters are large structures in the Universe, composed of tens or hundreds of galaxies bound by gravity. In the hierarchical formation model, they are formed and grow by accretion of smaller groups or isolated galaxies. In this scenario, understanding how these accreted galaxies interact with the very dense cluster environnement is an important step towards explaining the global picture of galaxy evolution and structure formation. Indeed, during infall, galaxies are subject to numerous interactions with the host cluster, both at the level of the baryonic and dark matter component, and these interactions influence the properties of the infalling galaxy. At the level of dark matter, numerical simulations suggest that dynamical friction sinks galaxies towards the center of clusters, and tidal forces of the host can strip part of the satellite's matter away, and even disrupt it. The detection of this stripping contains important informations on the evolution of groups and clusters: what quantity of dark matter is associated to the cluster galaxies as a function of the distance to the centre of the cluster ? How does this depend on the redshift and dynamical state of the cluster ? Does stripping depend on the morphological type of cluster galaxies ? The main work of this thesis is focused on studying galaxies in clusters, in particular tidal stripping of their dark matter haloes. The dark matter halo profiles are measured with weak gravitational lensing, using galaxy shape catalogues from the CFHTLenS, CFHT Stripe 82 and DES-SV surveys, combined with the redMaPPer cluster catalogue
10
Knippschild, Bastian [Verfasser]. "Baryons in the chiral regime / Bastian Knippschild". Mainz : Universitätsbibliothek Mainz, 2012. http://d-nb.info/1020765712/34.
11
Yamato, Shinichiro. "Static properties of baryons in holographic QCD". 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124420.
12
Elliot-Ripley, Matthew Kevin Ian David. "Baryons, salt and popcorn in holographic QCD". Thesis, Durham University, 2017. http://etheses.dur.ac.uk/12156/.
Resumo:
The Sakai-Sugimoto model is the leading model of holographic QCD. It has an effective five-dimensional description in which baryons correspond to the bulk topological solitons of a Yang-Mills-Chern-Simons theory. However, the large dimensionality of the model means studying soliton solutions either analytically or numerically is difficult. Sakai-Sugimoto solitons in the high density limit should provide an analogue of cold, dense QCD. Two competing theories for high-density solutions are the dyon salt model, in which the appropriate crystal is a salt-like arrangement of dyons, and the baryonic popcorn model in which a series of transitions occurs where the three-dimensional soliton crystal develops extra layers in the holographic direction. In this thesis we consider a range of low-dimensional analogues and approximations to the Sakai-Sugimoto model. We first investigate an O(3) sigma model stabilised by vector mesons, and a baby Skyrme model in pure AdS spacetime, before moving on to consider homogeneous ansätze in both the holographic baby Skyrme and full Sakai- Sugimoto models. In each case we look for analogues of the dyon salt and baryonic popcorn configurations, and find evidence for new features in the high-density regime of holographic QCD.
13
Rasera, Yann. "L'histoire cosmique des baryons dans un univers hierarchique". Phd thesis, Université Paris-Diderot - Paris VII, 2005. http://tel.archives-ouvertes.fr/tel-00070844.
Resumo:
Durant cette these, j'ai etudie la formation des galaxies grace a des simulations cosmologiques et a un nouveau modele analytique. Dans le cadre du modele standard de formation hierachique des grandes structures, les petites fluctuations primordiales de densite observees sur le fond diffus cosmologique sont amplifiees par la gravite pour donner des halos de matiere noire de plus en plus gros. C'est au sein de ces halos que le gaz s'effondre et se refroidit pour former des disques de gaz froid a support centrifuge. Ces disques sont ensuite convertis en disques stellaires : les galaxies. Le probleme dans ce scenario est celui du sur-refroidissement : une trop grande part du gaz finit sous forme d'etoiles comparativement aux observations. J'ai donc realise une etude de l'evolution des baryons (un gaz d'hydrogene et d'helium) dans l'Univers grace a des simulations numeriques hydrodynamiques haute-resolution. Cependant, ces simulations sont affectees par des effets de resolution finie. J'ai ainsi developpe un modele analytique simple qui possede l'avantage de ne pas etre affecte par de tels effets. Celui-ci predit la quantite de baryons dans chacune des 4 phases suivantes : etoiles, gaz froid dans les disques galactiques, gaz chaud dans les amas et gaz diffus dans le milieu intergalactique. La comparaison des resultats aux observations a montre que la cosmologie controle le taux de formation d'etoiles dans l'Univers. Ce modele a aussi mis en lumiere le role essentiel des vents galactiques qui, ejectant le gaz froid des disques jusque dans les halos de gaz chaud, permettent d'eviter le probleme du sur-refroidissement. Enfin, en une ouverture vers l'astroparticule, j'ai etudie les implications de la physique du gaz sur le fond diffus gamma produit dans l'hypothese de matiere noire legere.
14
Ohlsson, Tommy. "Properties of baryons in the chiral quark model". Licentiate thesis, KTH, Fysik, 1997. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-756.
Resumo:
In this thesis, several properties of baryons are studied using the chiral quark model. The chiral quark model is a theory which can be used to describe low energy phenomena of baryons. In Paper 1, the chiral quark model is studied using wave functions with configuration mixing. This study is motivated by the fact that the chiral quark model cannot otherwise break the Coleman–Glashow sum-rule for the magnetic moments of the octet baryons, which is xperimentally broken by about ten standard deviations. Configuration mixing with quark-diquark components is also able to reproduce the octet baryon magnetic moments very accurately. In Paper 2, the chiral quark model is used to calculate the decuplet baryon magnetic moments. The values for the magnetic moments of the ++and− are in good agreement with the experimental results. The total quark spin polarizations are also calculated and are found to be significantly smaller than the non-relativistic quark model results. In Paper 3, the weak form factors for semileptonic octet baryon decays are studied in the chiral quark model. The “weak magnetism” form factors are found to be consistent with the conserved vector current (CVC) results and the induced pseudotensor form factors, which seem to be model independent, are small. The results obtained are in general agreement with experiments and are also compared with other model calculations.QC 20100618
15
Powell, Leila Catherine. "Baryons in hierarchical structure formation : substructure and accretion". Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532005.
16
Cahill, Mark D. "An extension of the Skyrme model of baryons". Thesis, University of Kent, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329094.
17
McGovern, J. A. "Strange baryons in a chiral quark-meson model". Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233064.
18
Blanckenberg, Jacobus Petrus. "Skyrme model description of heavy baryons with strangeness". Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96953.
19
McEwen, Joseph Eugene McEwen. "The Hidden Universe: Dark Energy, Dark Matter, Baryons". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471877488.
20
Rasera, Yann. "L'histoire cosmique des baryons dans un univers hiérarchique". Paris 7, 2005. https://tel.archives-ouvertes.fr/tel-00070844.
21
Helminen, Christina. "Aspects of the quark model for the baryons". Helsinki : University of Helsinki, 2000. http://ethesis.helsinki.fi/julkaisut/mat/fysii/vk/helminen/.
22
Oettel, Martin. "Baryons as relativistic bound states of quark and diquark". [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=96321604X.
23
Lindebaum, R. J. "The anomalous magnetic moment of baryons in cavity QCD". Master's thesis, University of Cape Town, 1992. http://hdl.handle.net/11427/17387.
Resumo:
Bibliography: pages 86-87.Using a generalised form of the Gell-Mann and Low theorem, all the diagrams in cavity QCD to order as that contribute to the magnetic moment are calculated. The calculations are performed for massive quarks so a mass renormalisation scheme has been developed to cope with the new divergences this brings into the self-energy insert diagrams. The results of this work show that no improvement on the simple SU(3) model is made by including these corrections. These calculations point to a smaller value of αs than that which is usually used.
24
Ogilvy, Stephen. "Branching ratios of charmed baryons in the LHCb experiment". Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6463/.
Resumo:
LHCb is the dedicated heavy flavour experiment on the LHC accelerator ring. An analysis measuring the relative branching fractions of Lc->phh decays is presented using 1 inverse femtobarn of proton - proton collisions gathered by LHCb during 2011. Independent measurements are made using samples of Lc produced from the primary interaction and from those produced in semileptonic decays of Lb baryons. The measured relative branching ratios in the prompt analysis are B(Lc->pK-K+)/B(Lc->pK-pi+) = (2.03 ± 0.07 (stat) ± 0.10 (syst)) × 10−2, and B(Lc->ppi-pi+)/B(Lc->pK-pi+) = (7.04±0.19(stat)±0.34(syst))×10−2, while in the semileptonic analysis they are measured to be B(Lc->pK-K+)/B(Lc->pK-pi+) = (1.68 ± 0.03 (stat) ± 0.04 (syst)) × 10−2, and B(Lc->ppi-pi+)/B(Lc->pK-pi+) = (7.45±0.06(stat)±0.24(syst))×10−2. In the semileptonic analysis we make the first observation of the decay mode Lc->pK+pi- with a significance of 11.1 sigma. We measure the ratio: B(Lc->pK+pi-)/B(Lc->pK-pi+) = (1.62±0.15(stat)±0.05(syst))×10−3. Charged hadron discrimination in LHCb is provided by two ring imaging Cherenkov detectors. A data-driven study on the performance of the aerogel Cherenkov radiator is presented. Particle identification information is used to construct variables describing the likelihood of hadronic particle hypotheses of reconstructed tracks, on which cuts are placed in typical physics analyses. The preparation of new data samples allowing for the data-driven efficiency correction of particle identification cuts on proton tracks is described.
25
Wicker, Raphaël. "Baryons in galaxy clusters : astrophysical effects and cosmological constraints". Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASP114.
Resumo:
Les amas de galaxies sont les objets gravitationnellement liés les plus massifs de l'univers, et l'histoire de leur formation est une conséquence directe de l'évolution des structures dans l'univers. Ainsi, leur étude permet de poser des contraintes cosmologiques. L'utilisation des amas en tant que sondes cosmologiques repose sur l'observation de leur contenu en matière, en particulier ordinaire, ou baryons. Ces derniers sont présents sous forme d'étoiles contenues dans les galaxies, et de gaz au sein du milieu intra-amas. Toutefois, les baryons dans les amas de galaxies sont sujets à des effets astrophysiques qui affecteront leurs propriétés. Ces effets doivent être étudiés en détail afin d'obtenir une bonne compréhension des amas et contraindre correctement les conditions ayant dicté leur formation, jusqu'à leurs propriétés actuelles.Je propose ainsi dans cette thèse une étude approfondie des baryons et de leurs effets dans les amas, des galaxies au gaz, à partir d'observations en millimétrique, optique, et rayons X.Une première partie de mon étude se concentre sur les galaxies et l'analyse de leurs propriétés à partir de données de spectroscopie optique, dans deux systèmes triples d'amas découverts par le satellite Planck. Je montre que ces deux systèmes n'apparaissent triples que suite à des effets de projection sur la ligne de visée, et sont en réalité constitués de plusieurs amas isolés se trouvant à plusieurs centaines de megaparsecs les uns des autres, exceptée une paire d'amas.De plus je montre que dans l'amas le plus distant, certaines galaxies forment encore des étoiles, contrairement aux galaxies dans les amas à plus bas redshift. Il est possible que cela marque la transition entre un régime d'intense formation stellaire dans les amas à haut redshift, et le régime de faible formation stellaire observé dans les amas à bas redshift.La suite de mon étude est dédiée à la fraction de gaz au sein des amas, en particulier afin de contraindre le biais découlant de l'hypothèse d'équilibre hydrostatique lors de la mesure de leur masse. Mal contraint, ce "biais hydrostatique", est responsable de contraintes cosmologiques biaisées à partir des amas. En utilisant des masses de gaz et des masses totales mesurées en rayons X sous l'hypothèse de l'équilibre hydrostatique, j'ai calculé la fraction de gaz de 120 amas, et ai étudié la valeur du biais hydrostatique et son évolution avec la masse et le redshift. Je montre que l'évolution du biais est dégénérée avec les paramètres cosmologiques, menant à des contraintes cosmologiques aberrantes en cas de mauvaise prise en compte de l'évolution du biais. Cependant, je montre que mes résultats dépendent de l'échantillon choisi, avec une évolution du biais différente suivant la sélection en masse et en redshift. Je montre toutefois que quelque soit la sélection de l'échantillon, mes résultats sont en accord avec un ensemble de mesures directes par d'autres méthodes, ainsi qu'avec les prédictions de simulations hydrodynamiques. Ces résultats sont néanmoins en désaccord avec la valeur de biais favorisée par des observations du fond diffus cosmologique combinées à des comptages d'amas.Enfin, j'ai combiné des données de fraction de gaz d'amas de galaxies avec des comptages réalisés à partir d'observations en ondes millimétriques. Cela m'a permis d'étudier les contraintes cosmologiques rendues possibles par cette combinaison, ainsi que les contraintes sur le biais hydrostatique. Je montre que l'ajout de données de fraction de gaz aux comptages d'amas permet de briser des dégénérescences existantes entre le biais hydrostatique et certains paramètres cosmologiques, sans a priori sur le biais.Mon travail a donc permis d'améliorer notre compréhension d'ensemble des propriétés astrophysiques des baryons dans les amas. J'ai notamment mis en évidence certains des liens entre effets astrophysiques et contraintes cosmologiques par les amas, permettant leur description fidèle et robusteGalaxy clusters are the most massive gravitationally bound structures of the universe, and the history of their formation is a direct consequence of the evolution of the large scale structure of the universe. As a result, studying these objects allows to constrain cosmological parameters, which are at the core of the models describing the evolution of our universe. The use of galaxy clusters as cosmological probes relies on the observation of their matter content, and in particular their content in ordinary matter, or "baryons". Baryonic matter is mainly present under the form of stars in galaxies and of gas inside the intra-cluster medium. However, baryons in galaxy clusters are subject to astrophysical effects which will impact their properties. These effects need to be analysed in detail in order to obtain an in depth understanding of these objects and to properly constrain the conditions that dictated their formation, their assembly, and their current properties.I propose in this thesis a thorough analysis of baryons and of their effects in clusters, from galaxies to the gas, using observations in optical, X-ray, and millimeter wavelengths. A first part of my study is focused on galaxies and the analysis of their properties from optical spectroscopy, inside two triple-cluster systems discovered by the Planck satellite. I show that these two systems appear as triple only due to projection effects on the line of sight, and that they are actually constituted of isolated clusters lying at several hundreds of megaparsecs from each other, except for a cluster pair. I show in addition that inside the most distant cluster, several galaxies are still star-forming, contrary to the galaxies in lower redshift systems. This may be the sign of a transition between a regime of high star formation in high redshift systems and the low star formation regime which is observed in low redshift clusters.The remainder of my work is dedicated to the gas fraction in galaxy clusters, in particular to constrain the bias which appears following the assumption of hydrostatic equilibrium when measuring cluster masses. This "hydrostatic bias", if poorly understood, is responsible for biased cosmological constraints from galaxy clusters. By using gas masses and total masses computed under the assumption of hydrostatic equilibrium in X-ray observations, I computed the gas fraction of 120 galaxy clusters, and constrained the value of the hydrostatic bias, as well as its evolution with mass and redshift. I show that the evolution of the bias is degenerate with cosmological parameters, leading to aberrant cosmological constraints when assuming the wrong evolution for the bias. I however show that these results are dependent on the considered sample, with trends of the bias changing depending on the mass and redshift selection of the sample. In any case, whatever the sample selection I find that my results are in agreement with a collection of other measurements of the bias using other methods, as well as with predictions from hydrodynamical simulations. These results are nevertheless in tension with the value of the bias preferred by the combination of cosmic microwave background observations with galaxy cluster number counts.Finally I combined gas fraction data of clusters with cluster number counts from millimeter wavelengths observations. This allowed me to study the constraints on cosmological parameters that this combination allowed, as well as the constraints on the hydrostatic bias. I show that adding gas fraction to cluster counts allows to break degeneracies that exist between the hydrostatic bias and cosmological parameters, without any prior on the bias.My work thus allowed to improve the understanding of the astrophysical properties of baryons in galaxy clusters. I notably highlighted some of the links and correlations between astrophysical effects and cluster cosmology, allowing for an accurate and robust description of these objects
26
Benson, Kevin E. C. "Aspects of the electroweak phase transition and baryogenesis". Thesis, University of Oxford, 1993. http://ora.ox.ac.uk/objects/uuid:27c64513-bbb7-4f94-b385-4e691354a7b5.
Resumo:
In this thesis we study aspects of the cosmological electroweak phase transition which are relevant to the possibility of baryogenesis at this epoch. We focus on two issues: first, requiring that the observed baryon number be of electroweak origin places strong constraints on electroweak physics, and second, baryogenesis at the electroweak scale may be driven by an asymmetry generated at the GUT scale. We use the effective potential at finite temperature as a means of analyzing phase transitions associated with spontaneous symmetry breaking. We develop the theory with two basic examples: the scalar and Abelian Higgs models. Infrared divergences near the phase transition make the one-loop description unreliable, and indeed invalidate conventional perturbation theory. Borrowing a method from studies of QCD at high temperatures, we demonstrate that the summation of ring diagrams cures the leading infrared divergences and achieves a more reliable perturbative expansion. We then apply this formalism to the minimal Standard Model, following previous work, and confirm weak first-order behavior at the phase transition. We show that requiring the baryon number not be erased by sphaleron processes after the phase transition places a stringent bound on the Higgs mass, which is incompatible with experiment. This cosmological bound, however, may be relaxed by extending the scalar sector of the Standard Model. We consider the two simplest such extensions, the addition of a gauge singlet and of a second doublet. We demonstrate that ring-improvement in the singlet extension alters previous arguments at the one-loop level and yields a more restrictive bound on the Higgs mass. While ring-improvement in the two-doublet model, in principle, also reduces the Higgs mass bound found earlier at one loop, the multitude of new couplings in this model does not permit a definitive statement. We then investigate a mechanism for generating the observed baryon asymmetry (nB/S~ 10-10) at the electroweak phase transition from a pre-existing leptonic asymmetry (LT/s~ 10-5) produced at the GUT scale. This mechanism works by charge transport in a strongly first-order phase transition and avoids the need for large CP-violation at the electroweak scale.
27
Plaszczynski, Stéphane. "Etude de la production des hyperons a lep (delphi) et recherche de baryons beaux etranges". Paris 7, 1994. http://www.theses.fr/1994PA077178.
Resumo:
A partir de l'analyse des donnees enregistrees a lep avec le detecteur delphi en 1991-1992-1993, un signal de baryons beaux etranges est obtenu par l'etude des correlations de charge entre un hyperon xi et un lepton d'un meme jet. Les diverses sources conduisant a cet etat final sont etudiees. La probabilite que ce signal soit issu de fluctuations d'autres sources que des baryons beaux est estimee a 10#-#4. Une evaluation de la duree de vie des baryons beaux etranges est effectuee. Les taux de production inclusifs de plusieurs hyperons sont egalement mesures
28
Yip, Matthew Wing Yu. "Rare decays of heavy baryons using soft collinear effective theory". Thesis, Durham University, 2013. http://etheses.dur.ac.uk/7758/.
Resumo:
In the era of high-luminosity hadronic colliders, the rare heavy-to-light decay Lambda_b to Lambda l+ l- receives increasing research attention in both experimental and theoretical particle phenomenology. This flavour-changing neutral-current decay is a potential window for the discovery of new Physics beyond the Standard Model through its helicity-sensitive nature, complementing past and ongoing searches and calculations related to the B meson. In this work the universal soft form factor in the heavy-quark and large-recoil limits is calculated using light-cone sum rules in the framework of soft-collinear effective theory, as is the O(alpha_s) correction from hard-collinear gluon exchange. Numerical estimates on form-factor ratios and experimental observables are presented. Related issues, including baryonic transition form factors and in particular light-cone distribution amplitudes for the heavy baryon Lambda_b, are also discussed.
29
Ferlito, Fulvio. "Structure formation simulations with scattering between dark energy and baryons". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23855/.
Resumo:
Our Universe is full of unknowns, among them one of the most mysterious is, no doubt, dark energy (DE), the entity responsible for cosmic acceleration. We still do not even know its intrinsic nature, and in investigating its properties we can not exclude the possibility of an interaction between DE and the other components of the Universe.
In recent times, a new class of interacting DE models have been proposed in the literature. These assume that the interaction between DE and matter could be well approximated by a pure momentum exchange. The efficiency of the process is then described by the interaction cross section.
These models have been investigated via N-body simulations in the case of scattering between DE and dark matter, discovering that the nonlinear effects can be stronger than the linear ones. More recently such scenario has been extended to a scattering between DE and baryons, asking whether it would be possible to detect its effects through cosmological observations. A linear analysis lead to the conclusion that, even for extremely large values of the cross section, the impact of DE-baryon scattering on the CMB power spectrum and the matter power spectrum would be undetectable.
Therefore, the only yet unexplored field that leaves an opportunity to put cosmological constraints on such interaction is the nonlinear regime of structure formation, which can be properly studied only through N-body simulations. In this work we modify the GADGET3 code in order to perform, for the first time in the literature, structure formation simulations which implement DE-baryon scattering.
We focus on the effects of such interaction on major cosmological observables: the power spectrum, the mass function, the halo density profiles and the halo baryon fraction profiles. We find that the nonlinear effects of DE-baryon scattering can significantly affect these observables, thus paving the way to the future constraining of this interaction with cosmological observations.
30
Chai, Xuedong. "Exclusive B decays into final states with two charmed baryons". Diss., University of Iowa, 2007. http://ir.uiowa.edu/etd/126.
31
Holmberg, Måns. "Detemining low-energy constants in PTfrom decays of decuplet baryons". Thesis, Uppsala universitet, Kärnfysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-397766.
32
Zanotti, James Michael. "Baryon spectroscopy with FLIC fermions". Title page, abstract and table of contents only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phz33.pdf.
Resumo:
"October 2002" Bibliography: p. 129-136. 1. Introduction -- 2. QCD and the standard model -- 3. The Lattice -- 4. Symanzik improvement in the Static Quark Potential -- 5. Scale determination for an improved Gluon Action -- 6. Fat-link Irrelevant Clover Fermion actions -- 7. Excited Baryons in Lattice QCD -- 8. Spin 3/2 Baryons -- 9. Conclusion. This thesis reports work done in conducting numerical simulations of Lattice QCD.
33
Mattson, Mark Edward. "Inclusive hadron production in electron-positron collisions with center-of-mass energies from 50 to 61.4 GeV". Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-09192008-063028/.
34
Vargas, Magana Mariana. "Large Scale Structure with SDSS III- BOSS". Paris 7, 2012. http://www.theses.fr/2012PA077043.
Resumo:
Le travail de ma thèse s'est concentré sur l'extraction du signal laissé par les BAO dans la distribution des galaxies. Celui se présente sous forme d'un pic autour de 150 Mpc dans la fonction de corrélation à deux point de la matière. Cette échelle correspond à la distance parcourue par l'onde acoustique dans le fluide matière-radiation entre la période d'égalité matière-radiation et leur découplage à z-1100. Il en résulte une sur-densité à cette échelle autour de chaque perturbation primordiale. Le but de mon travail était d'effectuer une analyse complète sur les données prises par la collaboration SDSS III/BOSS jusqu'à l'été 2011 afin ; d'apporter des contraintes sur les paramètres caractérisant l'énergie noire, WO et Wa. On veut \ savoir si ces observations sont consistantes avec la fameuse constante cosmologique (W0=1 et Wa=0) ou si l'équation d'état de l'énergie noire évolue avec le temps (Wa diff 0) impliquant alors des scénarios bien plus complexes pour cette composante. Pour y arriver, j'ai étudié et testé les j outils d'analyse avec des simulations log-normal ainsi qu'avec les données publiques du DR7 de ; SDSS. J'ai étudié les effets de distorsion des redshifts dans le régime linéaire avec des simulations et j'ai développé une méthode d'optimisation d'estimateur de fonction de corrélation. Dans un second temps j'ai réalisé l'analyse complète des données BOSS-CMASS, qui utilise les galaxies elliptiques très lumineuses (LRGs), depuis la construction du catalogue jusqu'à l'obtention des contraintes cosmologique en passant par la correction des effets systématiquesMy research focuses on the extraction of the signal imprinted by the BAO on the galaxy distribution. The BAO feature is a bump at -150Mpcin the two-points correlation function of the matter in the Universe. This corresponds to maximum distance travelled by acoustic waves in the matter-radiation fluid during the period from matter/radiation equality to their decoupling at z-1100. An excess density at a radius of 150 Mpc was left after decoupling around each dark-matter density peak. The final goal of my work is to perform a complete analysis of the data available up to summer 2011 in SDSS III/BOSS in order to give constraints on isotropised distance DV and constraint the dark energy equation of state parameters wo and Wa. With such observations, one wants to check if the data is consistent with the so-called cosmological constant (corresponding to wo= -1 and wa= 0) or if the dark energy equation of state shows a time evolution (wa= 0) pointing to more complex dark energy scenarios. I studied and tested data analysis tools with log normal simulations and the public DR7 to achieve this goal. I studied the redshift distortions with simulations in the linear regime and I developed a optimization method for the correlation function estimator. The second part of my my work was focused in the analysis of BOSS data. There are to main programs in the SDSS III/BOSS project: the Luminous Red Galaxies catalogue and a new technique based on quasars using the Lyman-alpha forest. I have focused my research on the LRG science. I performed a complete analysis of BOSS-CMASS sample from catalog construction, systematic corrections and cosmological constrains
35
Dentin, Serge. "Contribution à l'étude du secteur baryonique dans la théorie des perturbations chirales". Aix-Marseille 2, 1990. http://www.theses.fr/1990AIX22077.
Resumo:
Le lagrangien fondamental des interactions fortes (chromodynamique quantique, ou qcd) est invariant, quand les masses des quarks sont nulles, sous l'action d'un groupe de symetrie su(3)su(3) (groupe chiral) agissant dans l'espace des saveurs. Cette symetrie est spontanement brisee, laissant place a huit bosons de nambu-goldstone sans masse: les mesons pseudoscalaires de l'octet de su(3). La theorie des perturbations chirales (cpt) offre la possibilite d'une description a basses energies des etats hadroniques les plus legers: par rapport aux echelles typiques d'energie mises en jeu dans ces processus, les masses des quarks peuvent etre traitees comme de petites perturbations. Nous avons considere dans cet ouvrage l'application de ces techniques a la description du secteur des baryons les plus legers. En particulier, nous avons etudie sur quelques exemples precis (masses, terme sigma, facteurs de forme electromagnetiques) la structure a une boucle des amplitudes (corrections non-analytiques, etc. . . ). Enfin, nous montrons que les baryons ne contribuent que tres faiblement aux constantes de couplage effectives du secteur mesonique, utilisant pour cela les techniques modernes d'evaluation des determinants d'operateurs elliptiques
36
Conte, Eric. "Recherche de la violation des symétries CP et T dans les réactions Lambda0_b -> Lambda 0 + un méson vecteur. Validation de l'architecture de lecture des canaux du détecteur de pied de gerbe de l'expérience LHCb". Clermont-Ferrand 2, 2007. http://www.theses.fr/2007CLF21785.
Resumo:
Cette thèse explore la physique des baryons beaux dans le cadre de l'expérience LHCb. L'axe de recherche considéré porte sur les désintégrations lambda0b en lambda0 V avec V un méson vecteur tel que J/psi (µ+ µ-), phi (K+K-), oméga (pi+pi-pi0) ou encore le mélange rhô0 _ oméga0 (pi+pi-). Ces processus offrent la possibilité de tester la symétrie CP, dans un secteur (celui des baryons) où aucune violation n'a été observée, et la symétrie T, dont les preuves de sa violation sont limitées. Parmi les autres perspectives envisageables, une mesure précise du temps de vie du lambda0b pourrait contribuer à la résolution du puzzle théorico-expérimental aujourd'hui observé. Un modèle phénoménologique des désintégrations lambda0b en lamda0 V a été développé, à partir duquel les rapports d'embrachement et les distributions angulaires ont été estimés. Une étude approfondie de la reconstruction et de la sélection de ces réactions par le détecteur LHCb montre que le canal lambda0b en lambda J/psi est le canal phare sur le plan statistique et pureté du signal. La mesure du temps de vie du lambda0b est le résultat le plus rapidement accessible ; les contraintes sur les asymétries dues à la violation de CP et la violation de T nécessitent plusieurs années de prise de données, avant d'obtenir un résultat significatif. En outre, un travail instrumental a été mené sur l'électronique de lecture, dite Front-End, des canaux du détecteur de pied de gerbe de l'expérience. Cette contribution comprend la validation des cartes électroniques prototypes et la mise en place des outils requis pour la qualification des 100 cartes de production
37
Ohlsson, Tommy. "Dynamics of quarks and leptons : theoretical Studies of Baryons and Neutrinos". Doctoral thesis, KTH, Fysik, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2991.
Resumo:
The Standard Model of Elementary Particle Physics (SM) is the present theoryfor the elementary particles and their interactions and is a well-established theorywithin the physics community. The SM is a combination of Quantum Chromodynamics(QCD) and the Glashow{Weinberg{Salam (GWS) electroweak model. QCDis a theory for the strong force, whereas the GWS electroweak model is a theoryfor the weak and electromagnetic forces. This means that the SM describes allfundamental forces in Nature, except for the gravitational force. However, the SMis not a nal theory and some of its problems will be discussed in this thesis.In the rst part of this thesis, several properties of baryons are studied suchas spin structure, spin polarizations, magnetic moments, weak form factors, andnucleon quark sea isospin asymmetries, using the chiral quark model (QM). TheQM is an eective chiral eld theory developed to describe low energy phenomena of baryons, since perturbative QCD is not applicable at low energies. The resultsof the QM are in good agreement with experimental data.The second part of the thesis is devoted to the concept of quantum mechanicalneutrino oscillations. Neutrino oscillations can, however, not occur within the GWSelectroweak model. Thus, this model has to be extended in some way. All studiesincluding neutrino oscillation are done within three avor neutrino oscillationmodels. Both vacuum and matter neutrino oscillations are considered. Especially,global ts to all data of candidates for neutrino oscillations are presented and alsoan analytical formalism for matter enhanced three avor neutrino oscillations usingtime evolution operators is derived. Furthermore, investigations of matter eectswhen neutrinos traverse the Earth are included.The thesis begins with an introductory review of the QM and neutrino oscillationsand ends with the research results, which are given in the nine accompanyingscientic articles.QC 20100616
38
Berntzon, Lisa. "Studies of Heavy Baryons in DELPHI and Radiation Monitoring in DØ". Doctoral thesis, Stockholm : Fysikum, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-173.
39
Sintes, Benjamin. "Etude des baryons avec le modèle de Nambu et Jona-Lasinio". Nantes, 2014. http://archive.bu.univ-nantes.fr/pollux/show.action?id=f4575fbb-7004-4427-85e7-a7bc179c76aa.
Resumo:
Durant cette thèse nous avons étudié la transition de phase entre la matière hadronique et le plasma de quark et de gluon en utilisant le modèle de Nambu et Jona-Lasinio. Ce modèle permet une description à basse énergie du processus d'hadronisation ayant lieu durant le refroidissement du plasma. Le lagrangien est basé sur les mêmes symétries que celui de QCD et a déjà montré de bons résultats pour les mésons. On souhaite ajouter les baryons afin de compléter cette description. Nous avons étudié les mésons et les diquarks en faisant appel au même formalisme, dans un premier temps à température nulle, puis pour des températures et potentiels finis. Ensuite nous avons étendu ces résultats aux baryons, en les décrivant comme des paires de quarks et diquarks. Cette thèse inclue la description de l'octet et du décuplet de baryonDuring this thesis we have studied the phase transition between hadronic matter and quark gluon plasma using the Nambu and Jona Lasinio model. This model allows a low energy description especially for hadronization process occurring during the cooling. The Lagrangian is based on the same symmetries that the QCD Lagrangian and has already shown good results for mesons. We want to add baryons in order to complete the description. We have studied the formalism for mesons and diquarks where descriptions are the same, in a first time at zero temperature and then at finite temperature and chemical potential. Then we have extended those results for baryons, describing them like a pair made of a quark and a diquark. This thesis includes the description of both the octet and decuplet of baryon
40
Nawa, Kanabu. "Non-perturbative aspects of quantum chromodynamics for quarks, diquarks, and baryons". 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136762.
41
Gastineau, Fabrice. "La thermodynamique et la dynamique de la version étendue du modèle de Nambu-Jona-Lasinio". Nantes, 2002. http://www.theses.fr/2002NANT2041.
Resumo:
Dans le cadre de cette thèse une étude détaillée des propriétés thermodynamique et dynamique du modèle de Nambu-Jona-Lasinio (NJL) a été élaborée. Ce modèle est une bonne approximation de la physique hadronique de basse énergie, autorisant l'étude de tous les phénomènes reliés à la transition de phase chirale. Il a en plus l'avantage d'être simple à manipuler permettant ainsi son extension à température et densité finies. Une premiȩ̀re partie concerne l'étude du diagramme des phases du modèle NJL, ainsi il est montré que la transition de phase chirale y est décrite de façon correcte. Une attention particulière est ensuite faite à la phase supraconductivité de couleur, état possible de la matière à haute densité baryonique. La suite de la thèse est consacrée à la description des hadrons dans la matière dense et chaude dans le cadre de NJL. Plus particulièrement, les diquarks y sont étudiés avec une grande attention afin de les inclure dans un formalisme pour traiter les baryons. Ces derniers ont ainsi pu être décrits comme des états liés d'un quark et d'un diquark. Il a été également possible d'étudier leur comportement dans un système à température et densité finies, comme attendu une diminution de la masse de ces baryons a été observée. .
42
Rubin, Douglas Seth. "Properties of Dark Matter Halos and Novel Signatures of Baryons in Them". Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11329.
Resumo:
This thesis investigates the properties of dark matter halos and places constraints on the baryons within them by utilizing observational data. In Chapter 2, we use spherical collapse dynamics to calculate the non-linear over-density of a dark matter halo at virialization given realistic initial and final density profiles in an Einstein-de Sitter cosmology and cosmologies with matter, dark energy and possible curvature. We find that the non-linear over-density at virialization can be reduced by as much as a factor of 10 as compared to the standard value.Physics
43
Schaller, Matthieu. "Effects of baryons on the dark matter distribution in cosmological hydrodynamical simulations". Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11275/.
Resumo:
Simulations including solely dark matter performed over the last three decades have delivered an accurate and robust description of the cosmic web and dark matter structures. With the advent of more precise cosmological probes, planned and ongoing, and dark matter detection experiments, this numerical modelling has to be improved to incorporate the complex non-linear and energetic processes taking place during galaxy formation. We use the ``Evolution and Assembly of GaLaxies and their Environment'' (EAGLE) suite of cosmological simulations to investigate the effects of baryons and astrophysical processes on the underlying dark matter distribution. Many effects are expected and we investigate (i): the modification of the profile of halos from the Navarro-Frenk-White profile shape found in collisionless simulations, including the changes in the dark matter profiles themselves, (ii) the changes of the inner density profiles of rich clusters, where observations have suggested a deviation from the standard cold dark matter paradigm, (iii) the offset created by astrophysical process between the centre of galaxies and the centre of the dark matter halo in which they reside and, (iv) the changes in the shape of the dark matter profile due to baryons in the centre of Milky Way halos and the impact these changes have on the morphology of the annihilation signal that could be observed as an indirect proof of the existence of dark matter. In all cases we find that the baryons play a significant role and change the results found in collisionless simulations dramatically. This highlights the need for more simulations like EAGLE to better understand and analyse future cosmology surveys. We also conduct a thorough study of the hydrodynamics solver parameters used in these simulations, assess their impact on the simulated galaxy population and show how robust some of the EAGLE results are against such variations.
44
Guillet, Thomas. "Effets des baryons sur les propriétés statistiques des grandes structures de l’Univers". Paris 11, 2010. http://www.theses.fr/2010PA112123.
Resumo:
Les observations de lentilles faibles gravitationnelles sont en mesure de fournir des pistes quant à la nature de l'énergie noire et ses propriétés. Leur interprétation est rendue plus difficile par la physique des baryons qui modifie la distribution totale de matière à petite échelle. Mon travail s'est axé sur la détermination et la modélisation des effets des baryons sur les statistiques de la distribution de matière dans l'Univers. En mettant en oeuvre des simulations numériques, j'ai mesuré l'effet des baryons prédit par ces simulations sur le spectre en puissance, la variance et le troisième moment de la distribution de matière. J'ai montré qu'un modèle de halo, incluant la présence de baryons sous la forme d'une concentration centrale de matière dans les halos, reproduit avec précision la variance et le troisième moment du champ de densité. En raison des problèmes connus relatifs aux baryons observés dans les simulations cosmologiques actuelles, j'ai développé le modèle afin d'inclure des ingrédients connus par des observations. J'ai appliqué ce modèle à la détermination des paramètres d'énergie noire à partir de l'expérience Euclid, qui verra le jour dans un futur proche. Au cours de ce travail, j'ai également travaillé au développement et à l'extension du code RAMSES, notamment en développant un solveur d'autogravité parallèle, qui apporte des gains de performance significatifs, en particulier pour la simulation de certaines configurations astrophysiques comme les galaxies isolées et les amasObservations of weak gravitational lensing will provide strong constraints on the cosmic expansion history and the growth rate of large scale structure, yielding clues to the properties and nature of dark energy. Their interpretation is impacted by baryonic physics, which are expected to modify the total matter distribution at small scales. My work has focused on determining and modeling the impact of baryons on the statistics of the large scale matter distribution in the Universe. Using numerical simulations, I have extracted the effect of baryons on the power spectrum, variance and skewness of the total density field as predicted by these simulations. I have shown that a model based on the halo model construction, featuring a concentrated central component to account for cool condensed baryons, is able to reproduce accurately, and down to very small scales, the measured amplifications of both the variance and skewness of the density field. Because of well-known issues with baryons in current cosmological simulations, I have extended the central component model to rely on as many observation-based ingredients as possible. As an application, I have studied the effect of baryons on the predictions of the upcoming Euclid weak lensing survey. During the course of this work, I have also worked at developing and extending the RAMSES code, in particular by developing a parallel self-gravity solver, which offers significant performance gains, in particular for the simulation of some astrophysical setups such as isolated galaxy or cluster simulations
45
Fleck, Sonia. "Baryons à double charme et quelques autres aspects de la spectroscopie hadronique". Grenoble 1, 1988. http://www.theses.fr/1988GRE10102.
46
Fleck, Sonia. "Baryons à double charme et quelques autres aspects de la spectroscopie hadronique". Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376136390.
47
Azizi, Kazem. "Properties Of Light And Heavy Baryons In Light Cone Qcd Sum Rules Formalism". Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610468/index.pdf.
Resumo:
In this thesis, we investigate the masses, form factors and magnetic dipole moments of some light octet, decuplet and heavy baryons containing a single heavy quark in the framework of the light cone QCD sum rules. The magnetic dipole moments can be measured considering radiative transitions within a multiplet or between multiplets.
Analyzing the transitions among the baryons and calculating the above mentioned parameters can give us insight into the structure of those baryons. In analyzing the aforementioned processes, the transition form factors play a crucial role. In this thesis, the form factors for these transitions are calculated using the light cone QCD sum rules approach.
In the limit when the light quark masses are equal, mu = md = ms, QCD has an SU(3) flavour symmetry which can be used to classify the light baryons. This classification results in the light decuplet, octet and singlet baryons. The baryons containing single heavy quark, on the other hand, can be classified according to the spin of the light degrees of freedom in the heavy quark limit, mQ ->infinity. QCD at low energies, when the baryons are formed, is a non-perturbative theory. Hence, for phenomenology of the baryons, the QCD sum rules as a more powerful non-perturbative approach is used. Understanding the properties of nucleons is one of the main objectives of QCD. To investigate the properties of the nucleons, the axial N-Delta(1232) transition form factors are calculated within the light cone QCD sum rules method. A comparison of our results on those form factors with the predictions of lattice QCD and quark model is presented. The nucleon electromagnetic form factors are also calculated in the same framework using the most general form of the nucleon interpolating current. Using two forms of the distribution amplitudes (DA&rsquo
s), predictions for the form factors are presented and compared with existing experimental data. It is shown that our results describe the existing experimental data remarkably well. Another important property of the baryons is their magnetic moments. The magnetic moments of the heavy Xi_Q (Q = b or c) baryons containing a single charm or bottom quark are calculated within the light cone QCD sum rules approach. A comparison of our results with the predictions of other approaches, such as relativistic and nonrelativistic quark models, hyper central model, Chiral perturbation theory, soliton and skyrmion models is presented. Moreover, inspired by the results of recent experimental discoveries for charm and bottom baryons, the masses and magnetic moments of the heavy baryons with J^2P = 3/2^+ containing a single heavy quark are studied also within the light cone QCD sum rules method. Our results on the masses of heavy baryons are in good agreement with predictions of other approaches, as well as with the existing experimental values. Our predictions on the masses of the states, which are not experimentally discovered yet, can be tested in the future experiments. A comparison of our results on the magnetic moments of these baryons and the hyper central model predictions is also presented.
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Ronniger, Michael [Verfasser]. "Spin and Flavour dependent Interactions within a Quark Model for Baryons / Michael Ronniger". Bonn : Universitäts- und Landesbibliothek Bonn, 2013. http://d-nb.info/104497110X/34.
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Mummery, B. O. "The role of baryons and neutrinos in the evolution of large-scale structure". Thesis, Liverpool John Moores University, 2018. http://researchonline.ljmu.ac.uk/9429/.
Resumo:
Galaxy groups and clusters (GGCs) hold a privileged position within the cosmological hierarchy. As the most recent structures to have formed, their abundances, spatial distribution and individual properties bear the indelible imprint of the background cosmology, initial conditions and their formation history, making them valuable probes of both cosmology and astrophysics. It has, however, become increasingly clear over the past decade that making use of these probes for precision cluster cosmology requires detailed, realistic predictions for the observed properties of GGCs. Producing these necessitates the use of large cosmological hydrodynamical simulations with realistic ‘sub-grid’ prescriptions for baryonic physics. One mechanism in need of addressing is the effect of the cosmic background of massive neutrinos. As these remain relativistic to relatively late times, they will free-stream out of overdensities, altering the formation of large-scale structure (LSS). If this effect can be accurately modelled, it presents an independent method of constraining the value of the neutrino mass by means of LSS observations. This thesis makes use of the cosmo-OWLS and BAHAMAS cosmological hydrodynamical simulation suites to explore the separate and combined effects of baryon physics (particularly feedback from active galactic nuclei, AGN) and the free-streaming of massive neutrinos on large-scale structure. I focus on five diagnostics: i) the halo mass function; ii) halo mass density profiles; iii) the halo mass concentration relation; iv) the clustering of haloes; and v) the clustering of matter; and I explore the extent to which the effects of baryon physics and neutrino free-streaming can be treated independently. In comparing to the GAMA observations, I find that these data provide insufficient statistical power to constrain the value of the summed neutrino mass. This is primarily due to the intrinsic scatter in the stellar mass - halo mass relation, and the strong dependence of the sensitivity on precise mass binning. As a consequence, more precise estimations of the halo mass will be required in future work seeking to utilise this metric. Finally, I find that the clustering of simulated BAHAMAS groups is remarkably consistent with that of observed GAMA groups. This lends additional weight to the argument that BAHAMAS accurately reproduces the properties of the GGC population, and supports its use as a cosmological tool.
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Edwards, Adam Jacob. "A study of double-charm and charm-strange baryons in electron-positron annihilations /". May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.