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Добірка наукової літератури з теми "Courants neutres changeant la saveur"
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Дисертації з теми "Courants neutres changeant la saveur"
Plakias, Ioannis. "Probes of the Flavor Problem through Effective Theories." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP067.
Повний текст джерелаIn this thesis, we study the possibility of probing yet unknown heavy New Physics (NP) degrees of freedom through Flavor-Changing Neutral-Current (FCNC) processes at low energies. We analyze them within the framework of Effective Field Theories (EFTs) to exploit the separation of the energy scales involved. We focus on Standard Model (SM) processes which have already been observed and which are particularly sensitive to NP effects (b → s γ), or forbidden processes in the SM whose observation would be an unambiguous sign of NP (Lepton Flavor Violation or LFV). Regarding b → s γ, we study angular observables of B_s → φ ee at low ee invariant mass, where the photon pole dominates, within the framework of the Low-energy EFT (LEFT). In particular, we compute the effects of meson-antimeson (B_s) mixing on the angular observables, and study how the additional observables induce projected NP constraints on the effective coefficients C_7 and C_7p describing the b → s γ transition. Regarding LFV, we study Renormalization Group Equation (RGE) effects in the Standard Model EFT (SMEFT) and the LEFT, and we show that they can induce stringent constraints on semileptonic third-generation-quark operators from the most constraining LFV processes, such as μ N → e N, l → l_p γ, l → 3 l_p and l → l_p M where M is a vector or pseudoscalar meson. In addition, we illustrate the complementarity between low- and high-energy LFV processes, and, in particular, we show that indirect upper bounds on LFV B-meson decays through LHC constraints on LFV Drell-Yan processes pp → l l_p can be competitive with direct measurements
Kochebina, Olga. "Study of Rare Charm Decays with the LHCb Detector at CERN." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112208/document.
Повний текст джерелаRare charm decays proceed mostly through the c -> u Flavor Changing Neutral Current (FCNC), which is possible only at loop level in the Standard Model (SM). In charmed decays, FCNCs are subject to a very efficient GIM suppression, leading to very rare processes. Consequently, rare charm decays are good tools to probe to New Physics (NP) beyond the SM. NP particles could become detectable by causing observables such as branching ratios and CP or angular asymmetries to deviate from the SM predictions. The main subject of this thesis is the measurement of the branching ratio of the D0 -> K-π+ ρ/ω (->µ+µ-) mode. It will be precious in the future, in particular as a normalization mode in the study of all: D0 -> h-h’+ µ+µ- decays D0 -> K-π+µ+µ-, D0 -> π+π-µ+µ-, D0 -> K+K-µ+µ- and D0 -> K+π-µ+µ-. Using 2/fb of 2012 LHCb data we find: B(D0 -> K-π+ ρ/ω (->µ+µ-)) = (4.37± 0.12(stat.) ±0.53(syst.)) ×10^-6. This is the first measurement of this mode. We also determined sensitivities to total and partial branching fractions and asymmetries in D0 -> h-h’+ µ+µ- decays with future LHCb datasets. In addition, the systematic uncertainties affecting the searches for the 3-body decays, D+(s) -> π+µ+µ- and D+(s) -> π-µ+µ+, carried out by LHCb based on the data collected in 2011 (1/fb). Finally, the results of the tests of front-end electronic board for the Upgrade of LHCb are presented
Quintana, Boris. "Search for radiative B decays to orbitally excited mesons at LHCb." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC060.
Повний текст джерелаThis document presents studies of radiative decays of B0 and Bs mesons to orbitally excited states, produced in proton collisions at the Large Hadron Collider (LHC) of CERN (European Council for Nuclear Research). It takes place in the context of the search for new physics processes beyond the standard model of particle physics. The work is based on the data collected at the LHCb experiment during the Run 1(2011-2012) and the Run 2 (2015-2018) of the LHC, which corresponds to an integrated luminosity of about 8.7 fb−1. First, an optimised selection of the final states comprising of two charged tracks and a high energy photon is put in place, regrouping a large samples of B hadron radiative decays. Then, a mass model is fit to the data distribution, allowing to statistically subtract the background contributions in the data set.A first amplitude analysis is then developed to study the hadronic structure in the Bs → K+K−γ decay mode. Resulting from this analysis is the first observation of the Bs → f2j (1525)γ mode together with a relative branching ratio measurement:B(Bs → f2j γ) = (24.1 ± 0.9 (stat) +1.6 (syst) ± 0.6 (br)) × 10−2B(Bs → φγ) −0.8It is the second radiative decay mode observed for the Bs meson. A similar analysis is performed on the B0 → K±π∓γ mode, allowing a preliminary measurement of the relative branching ratio of B0 → K2∗(1430)γ:(B0 K∗0(1430)γ)B(B0 → K∗0(892)γ) = (36.4 ± 0.4 (stat) ± 1.3(BR))%However, a detailed systematics study is needed to assess its competitivity with previous measurements of this decay mode. Making use of a similar selection strategy, a preliminary study of B K0hhγ modes is also set up during the thesis to estimate the available statistics for these modes at LHCb, which are particularly interesting to measure the photon polarisation in the b sγ transition. This work will be the starting point of an analysis comprising the future data that will be collected during the Run 3 of the LHC
Nicol, Michelle. "Analyse de la désintégration rare B->K*ee dans l'expérience LHCb." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00815968.
Повний текст джерелаNicol, M. "Analyse de la désintégration rare B0 ->K*0 e+e- dans l'expérience LHCb." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00788992.
Повний текст джерелаNicol, Michelle. "Analysis of the rare decay B->K*ee at LHCb." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112354/document.
Повний текст джерелаThe high bb cross section produced by the LHC offers an excellent opportunity for thestudy of flavour changing neutral current B decays, where the effects of new physics can be probed. This thesis presents an analysis of the rare decay B->K*ee which can be used to measure the polarisation of the photon in the b -> s transition. When the dilepton mass is low, the ee pair comes predominantly from a virtual photon, and the polarisation can be accessed via an angular analysis. It is predicted to be predominantly left handed in the Standard Model, and therefore an enhanced right handed amplitude would be a sign of new physics. A first step is to measure the branching fraction in the dilepton mass range, 30 MeV to 1 GeV. This decay has not yet been observed in this region, due to its small branching ratio. The analysis involves electrons with low transverse momentum, and is thus experimentally complex in the hadronic environment at the LHC. The branching ratio is measured relative to that of B->J/Psi(ee)K*, which eliminates both certain experimental effects, and the need to determine absolute effciencies. The result is obtained with an integrated luminosity of 1 fb-1 of pp collisions, collected by LHCb during 2011 and is found to be:B(B->K*ee)30-1000MeV = (3:19+0:75-0:68(stat) +/- 0:21(syst) =/-0.15(PDG) x10-7 when using the PDG value for the B->J/Psi(ee)K* branching ratio. The last part of the thesis presents Monte Carlo studies, showing that with the inclusion of the 2012 data sample, the expected sensitivity on the fraction of right handed polarisation is approximately 0.1, which is comparable with the world average obtained with different methods
Méaux, Cédric. "A phenomenological study of D+ → π+ I+ I− and the search for B(s) → τ+ τ− at LHCb". Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0370.
Повний текст джерелаOne of the main portals towards physics Beyond the Standard Model (BSM) are the heavy flavor meson decays to leptons as they proceed entirely through loop effects and are additionally suppressed by the chiral nature of the weak interactions. Thus their sensitivity to possible BSM virtual effects could be enhanced. b->sll transitions provide some of the strongest constraints on BSM physics. Interestingly, a number of anomalies of various significances have shown up in the first LHCb data for some of these modes. These anomalies seem to suggest the possibility of BSM physics with a hierarchy of the generations in the coupling to BSM particles, where the tau leptons should couple most strongly. Less studied because more challenging from a theoretical point of view, the charmed transition c->ull might also exhibit similar anomalies. This kind of searches, often qualified as indirect, relies on two ingredients: precision measurements and accurate predictions; this thesis is devoted to both aspects. At first, I focus on how to improve the predictions for the less studied charmed decay D+ -> pi+ ll; then, I present the experimental measurement of the B(s) -> tau tau decay
Pagé, Véronique. "Utilisation de la violation CP dans la désintégration [B en rhô pi] pour la recherche de nouvelle physique." Thèse, 2004. http://hdl.handle.net/1866/17331.
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