Letteratura scientifica selezionata sul tema "Theoretical astroparticles physics"

AbstractThe data we are receiving from galactic cosmic rays are reaching an unprecedented precision, over very wide energy ranges. Nevertheless, many problems are still open, while new ones seem to appear when data happen to be redundant. We will discuss some paths to possible progress in the theoretical modeling and experimental exploration of the galactic cosmic radiation.

Abstract This year the Journal of Cosmology and Astroparticle Physics (JCAP) celebrates its 20th anniversary. “A journal by scientists for scientists” is the motto that has driven JCAP since its inception, which epitomises its philosophy of being an innovative and community-driven journal. Over the past two decades, JCAP has become one of the premier outlets for high-quality research, now publishing circa 800 papers per year, almost all of which are Open Access (either green or gold route), and with submissions originating from more than 60 countries around the world. JCAP encompasses theoretical, observational, and experimental areas as well as computation and simulation, and this special issue represents a testament to the role of the journal and its impact within the fields of cosmology and astroparticle physics. Over the years, JCAP has published influential papers on topics ranging from the early universe and dark matter to large-scale structure, gravitational waves and high-energy astrophysics, all of which are presented in this celebratory collection of the journal’s 20th year of publication.

It is well known that a fundamental theorem of Quantum Field Theory (QFT) set in flat spacetime ensures the CPT invariance of the theory. This symmetry is strictly connected to the Lorentz covariance, and consequently to the fundamental structure of spacetime. Therefore it may be interesting to investigate the possibility of departure from this fundamental symmetry, since it can furnish a window to observe possible effects of a more fundamental quantum gravity theory in a “lower energy limit”. Moreover, in the past, the inquiry of symmetry violations provided a starting point for new physics discoveries. A useful physical framework for this kind of search is provided by astroparticle physics, thanks to the high energy involved and to the long path travelled by particles accelerated by an astrophysical object and then revealed on Earth. Astrophysical messengers are therefore very important probes for investigating this sector, involving high energy photons, charged particles, and neutrinos of cosmic origin. In addition, one can also study artificial neutrino beams, investigated at accelerator experiments. Here we discuss the state of art for all these topics and some interesting new proposals, both from a theoretical and phenomenological point of view.

The THDMa is a new physics model that extends the scalar sector of the Standard Model by an additional doublet as well as a pseudoscalar singlet and allows for mixing between all possible scalar states. In the gauge-eigenbasis, the additional pseudoscalar serves as a portal to the dark sector, with a priori any dark matter spins states. The option where dark matter is fermionic is currently one of the standard benchmarks for the experimental collaborations, and several searches at the LHC constrain the corresponding parameter space. However, most current studies constrain regions in parameter space by setting all but 2 of the 12 free parameters to fixed values. In this work, we performed a generic scan on this model, allowing all parameters to float. We applied all current theoretical and experimental constraints, including bounds from current searches, recent results from B-physics, in particular Bs→Xsγ, as well as bounds from astroparticle physics. We identify regions in the parameter space which are still allowed after these were applied and which might be interesting for an investigation of current and future collider machines.

Walter Greiner (29 October 1935 - 6 October 2016) was a German theoretical physicist. His scientific research interests include the thematic areas of atomic physics, heavy ion physics, nuclear physics, elementary particle physics (particularly quantum electrodynamics and quantum chromodynamics). He is most known in Germany for his series of books in theoretical physics, but he is also well known around the world. Greiner was born on October 29, 1935, in Neuenbau, Sonnenberg, Germany. He studied physics at the University of Frankfurt (Goethe University in Frankfurt Am Main), receiving in this institution a BSci in physics and a Master’s degree in 1960 with a thesis on plasma-reactors, and a PhD in 1961 at the University of Freiburg under Hans Marshal, with a thesis on the nuclear polarization in [Formula: see text]-mesic atoms. During the period of 1962 to 1964 he was assistant professor at the University of Maryland, followed by a position as research associate at the University of Freiburg, in 1964. Starting in 1965, he became a full professor at the Institute for Theoretical Physics at Goethe University until 2003. Greiner has been a visiting professor to many universities and laboratories, including Florida State University, the University of Virginia, the University of California, the University of Melbourne, Vanderbilt University, Yale University, Oak Ridge National Laboratory and Los Alamos National Laboratory. In 2003, with Wolf Singer, he was the founding Director of the Frankfurt Institute for Advanced Studies (FIAS), and gave lectures and seminars in elementary particle physics. He died on October 6, 2016 at the age of 80. Walter Greiner was an excellent teacher, researcher, friend. And he was a great supporter of the series of events known by the acronyms IWARA - International Workshop on Astronomy and Relativistic Astrophysics, STARS - Caribbean Symposium on Cosmology, Gravitation, Nuclear and Astroparticle Physics, and SMFNS - International Symposium on Strong Electromagnetic Fields and Neutron Stars. Walter Greiner left us. But his memory will remain always alive among us who have had the privilege of knowing him and enjoy his wisdom and joy of living.

In the lecture, I first review the basic problems of the ΔCDM model at small (galactic) scales, also known as “small-scale Cosmology crisis”, namely discrepancies between theoretical simulations and observations. I then argue how systems of righthanded neutrinos (RHN) with masses of order 50 keV in the galaxies can tackle these problems, provided appropriately strong RHN self-interactions are included. Such models may constitute interesting minimal extensions of the Standard Model. Combining galactic phenomenology with other astroparticle physics considerations of such models, one arrives at a narrow range 47 keVc-2 ≤ m ≤ 50 keVc-2 for the allowed mass m of RHN, thereby pointing towards the rôle of such particles as interesteding warm dark matter components.

The authors use new aesthetic criteria concerning structures and properties to explain parallel concepts within theoretical astroparticle physics and contemporary form/compositional research. These aesthetic criteria stem from complex curvature models developed both in string theory and in artistic perceptual research on transitional surfaces and concavities. The authors compare the complex curvatures of the mathematically derived Calabi-Yau manifold with one of Akner Koler's sculptures, which explores an organic interpretation of the looping curvature of a Möbius strip. A goal of the collaboration is to gain experience and insight into the twisting paradoxical forces in the 3D world and to explore the properties of transparency as applied to the Calabi-Yau manifold and a point cloud translation of Akner Koler's sculpture.

The study of solar neutrinos has given a fundamental contribution both to astroparticle and to elementary particle physics, offering an ideal test of solar models and offering at the same time relevant indications on the fundamental interactions among particles. After reviewing the striking results of the last two decades, which were determinant to solve the long standing solar neutrino puzzle and refine the Standard Solar Model, we focus our attention on the more recent results in this field and on the experiments presently running or planned for the near future. The main focus at the moment is to improve the knowledge of the mass and mixing pattern and especially to study in detail the lowest energy part of the spectrum, which represents most of the solar neutrino spectrum but is still a partially unexplored realm. We discuss this research project and the way in which present and future experiments could contribute to make the theoretical framework more complete and stable, understanding the origin of some “anomalies” that seem to emerge from the data and contributing to answer some present questions, like the exact mechanism of the vacuum to matter transition and the solution of the so-called solar metallicity problem.

In this work, a review of recent studies concerning rare nuclear processes in Hf isotopes is presented. In particular, the investigations using HP-Ge spectrometry and Hf-based crystal scintillators are focused; the potentiality and the results of the “source = detector” approach are underlined. In addition, a short introduction concerning the impact of such kind of research in the context of astroparticle and nuclear physics is pointed out. In particular, the study of α decay and double beta decay of 174Hf, 176Hf, 177Hf, 178Hf, 179Hf, 180Hf isotopes either to the ground state or to the lower bounded levels have been discussed. The observation of α decay of 174Hf isotope to the ground state with a T1/2=7.0(1.2)×1016 y is reported and discussed. No decay was detected for α decay of 174Hf isotope at the first excited level of daughter and of 176Hf, 177Hf, 178Hf, 179Hf, 180Hf isotopes either to the ground state or to the lower bounded levels. The T1/2 lower limits for these decays are at the level of 1016–1020 y. Nevertheless, the T1/2 lower limits for the transitions of 176Hf→172Yb (0+→0+) and 177Hf→173Yb (7/2−→5/2−) are near to the theoretical predictions, giving hope to their observation in the near future. All the other experimental limits (∼1016–1020 y) are absolutely far from the theoretical expectations. The experiments investigating the 2ϵ and ϵβ+ processes in 174Hf are also reported; the obtained half-life limits are set at the level of 1016–1018 y. Moreover, we estimate the T1/2 of 2ν2ϵ of 174Hf decay at the level of (0.3–6) × 1021 y (at now the related measured lower limit is 7.1×1016 y).

The main objective of the Cosmic-Ray Extremely Distributed Observatory (CREDO) is the detection and analysis of extended cosmic ray phenomena, so-called super-preshowers (SPS), using existing as well as new infrastructure (cosmic-ray observatories, educational detectors, single detectors etc.). The search for ensembles of cosmic ray events initiated by SPS is yet an untouched ground, in contrast to the current state-of-the-art analysis, which is focused on the detection of single cosmic ray events. Theoretical explanation of SPS could be given either within classical (e.g., photon-photon interaction) or exotic (e.g., Super Heavy Dark Matter decay or annihilation) scenarios, thus detection of SPS would provide a better understanding of particle physics, high energy astrophysics and cosmology. The ensembles of cosmic rays can be classified based on the spatial and temporal extent of particles constituting the ensemble. Some classes of SPS are predicted to have huge spatial distribution, a unique signature detectable only with a facility of the global size. Since development and commissioning of a completely new facility with such requirements is economically unwarranted and time-consuming, the global analysis goals are achievable when all types of existing detectors are merged into a worldwide network. The idea to use the instruments in operation is based on a novel trigger algorithm: in parallel to looking for neighbour surface detectors receiving the signal simultaneously, one should also look for spatially isolated stations clustered in a small time window. On the other hand, CREDO strategy is also aimed at an active engagement of a large number of participants, who will contribute to the project by using common electronic devices (e.g., smartphones), capable of detecting cosmic rays. It will help not only in expanding the geographical spread of CREDO, but also in managing a large manpower necessary for a more efficient crowd-sourced pattern recognition scheme to identify and classify SPS. A worldwide network of cosmic-ray detectors could not only become a unique tool to study fundamental physics, it will also provide a number of other opportunities, including space-weather or geophysics studies. Among the latter one has to list the potential to predict earthquakes by monitoring the rate of low energy cosmic-ray events. The diversity of goals motivates us to advertise this concept across the astroparticle physics community.

Parmi les problèmes ouverts de la physique moderne, la matière noire (MN) est l'un des plus fascinants. Elle explique plusieurs anomalies gravitationnelles présentes dans des systèmes à différentes échelles : la platitude des courbes de rotation des galaxies spirales, la dynamique des amas de galaxies, la distribution des structures à grande échelle dans l'Univers et les anisotropies de la température du fond diffus cosmologique. Des mesures précises de ces dernières, éventuellement combinées à d'autres techniques, montrent que la MN constitue environ un quart de l'énergie totale de l'Univers. Bien que nous ayons des preuves observationnelles fiables de l'existence de la MN, sa nature reste un mystère, car à ce jour, aucune observation n'a pu montrer que la MN peut interagir avec la matière ordinaire autrement que gravitationnellement. De nombreuses hypothèses sur sa nature subsistent. La MN pourrait exister sous la forme de particules élémentaires qui ne font pas partie du Modèle Standard de la physique des particules, ou sous forme d'objets macroscopiques compacts tels que les trous noirs primordiaux (TNP). Pour révéler la nature de la MN, ou à défaut, pour écarter des hypothèses la concernant, plusieurs techniques d'observation existent. Dans cette thèse, nous nous concentrons sur la méthode de détection indirecte, qui consiste à rechercher des signaux d'annihilation ou de désintégration de la MN sous forme de rayons cosmiques chargés, de photons ou de neutrinos. Chaque produit porte différents types d'informations. Les photons et les neutrinos, étant des particules neutres, peuvent se propager sans être déviés par les champs magnétiques environnants, ce qui facilite la localisation de leur source d'émission. Les rayons cosmiques chargés, en revanche, peuvent être constitués d'antimatière, qui est très peu produite par des processus astrophysiques et peut donc être détectée avec un faible signal de fond. Dans cette thèse, nous étudions l'émission de photons secondaires par l'interaction des produits issus de la MN avec le milieu galactique. En particulier, dans le cas où la MN est une particule de masse inférieure à un GeV, les électrons et positrons produits pourraient interagir avec des photons ambiants de la galaxie, produisant des rayons X par effet Compton inverse. La prédiction du spectre de ce rayonnement, comparée aux données des observatoires à rayons X, permet d'obtenir de fortes contraintes sur ce type de MN. De même, nous appliquons ce même principe au cas de l'évaporation des TNP afin de leur imposer de fortes contraintes
Among the open problems of modern physics, dark matter (DM) is one of the most fascinating. It explains several gravitational anomalies observed at different scales: the flatness of rotation curves of spiral galaxies, the dynamics of galaxy clusters, the distribution of large-scale structures in the Universe, and the anisotropies in the temperature of the cosmic microwave background. Precise measurements of the latter, possibly combined with other techniques, show that DM constitutes about a quarter of the Universe's energy budget. Although we have reliable observational evidence of DM's existence, its nature remains a mystery, as no observation has yet shown that DM can interact with ordinary matter other than gravitationally. Numerous hypotheses about its nature remain. DM could exist as elementary particles not included in the Standard Model of particle physics, or as macroscopic compact objects such as primordial black holes (PBH). To reveal the nature of DM, or to rule out hypotheses concerning it, several observational techniques are available. In this thesis, we focus on the method of indirect detection, which involves looking for signals of the annihilation or decay of DM in the form of charged cosmic rays, photons or neutrinos. Each product carries different types of information. Photons and neutrinos, being neutral particles, can propagate without being deflected by the surrounding magnetic fields, making it easier to trace their source of emission. Charged cosmic rays, on the other hand, may consist of antimatter, which is less likely produced by astrophysical processes and can therefore be detected with a low background. In this thesis, we study the emission of secondary photons by the interaction of DM products with the galactic environment. Specifically, we consider the case in which DM is a particle with a mass below a GeV. The electrons and positrons produced could interact with ambient photons in the galaxy, producing X-rays through inverse Compton scattering. The prediction of the spectrum of this radiation, compared with data from X-ray observatories, provides strong constraints on this type of DM. Similarly, we apply this same principle to the case of PBH evaporation in order to impose strong constraints on them

The striking evidence for the existence of dark matter in the Universe implies that there is new physics to be discovered beyond the Standard Model. To identify the nature of this dark matter is a key task for modern astroparticle physics, and a large number of experiments pursuing a range of different search strategies have been developed to solve it. The topic of this thesis is the complementarity of these different experiments and the issue of how to combine the information from different searches independently of experimental and theoretical uncertainties. The first part focuses on the direct detection of dark matter scattering in nuclear recoil detectors, with a special emphasis on the impact of the assumed velocity distribution of Galactic dark matter particles. By converting experimental data to variables that make the astrophysical unknowns explicit, different experiments can be compared without implicit assumptions concerning the dark matter halo. We extend this framework to include annual modulation signals and apply it to recent experimental hints for dark matter, showing that the tension between these results and constraints from other experiments is independent of astrophysical uncertainties. We explore possible ways of ameliorating this tension by changing our assumptions on the properties of dark matter interactions. In this context, we propose a new approach for inferring the properties of the dark matter particle, which does not require any assumptions about the structure of the dark matter halo. A particularly interesting option is to study dark matter particles that couple differently to protons and neutrons (so-called isospin-violating dark matter). Such isospin-violation arises naturally in models where the vector mediator is the gauge boson of a new U(1) that mixes with the Standard Model gauge bosons. In the second part, we first discuss the case where both the Z' and the dark matter particle have a mass of a few GeV and then turn to the case where the Z' is significantly heavier. While the former case is most strongly constrained by precision measurements from LEP and B-factories, the latter scenario can be probed with great sensitivity at the LHC using monojet and monophoton searches, as well as searches for resonances in dijet, dilepton and diboson final states. Finally, we study models of dark matter where loop contributions are important for a comparison of LHC searches and direct detection experiments. This is the case for dark matter interactions with Yukawa-like couplings to quarks and for interactions that lead to spin-dependent or momentum suppressed scattering cross sections at tree level. We find that including the contribution from heavy-quark loops can significantly alter the conclusions obtained from a tree-level analysis.

The SM model of particle physics reigned for almost four decades showing excellent consistency of the Higgs Boson at the LHC bestow the last missing piece of the model. Noetheless, the SM is incomplete as a description of nature for it suffers from some serious drawbacks such as it cannot provide a valid dark matter candidate, it has no piece of neutrino mass. In this thesis, we consider some simple BSM extensions that can alleviate these problems
Research was carried out under the supervision of Prof. Dilip Kumar Ghosh of the Theoretical Physics division under SPS [School of Physical Sciences]

In spite of its enormous success, the Standard Model (SM) of particle physics suffers from a few drawbacks. For example, the SM cannot account for the observations of neutrino mass and mixing and the existence of dark matter (DM). Supersymmetry (SUSY) is capable of addressing these issues in an elegant manner. Nevertheless, the non-observations of the superpartners to date has put stringent constraints on their masses. In the light of this, in this thesis, we consider a U(1)R symmetric model where the R-charges are identified with lepton numbers in such a way that one of the leftchiral sneutrinos can acquire a large vacuum expectation value (vev) and can play the role of a down type Higgs field. Models with U(1)R symmetry and Dirac gauginos are well motivated since they can address the issues relating to the Higgs boson mass, DM and neutrino mass generation. Most importantly, the presence of Dirac gluinos can relax the bound on superpartner masses. We augment the model with a right handed neutrino superfield to have a small Dirac neutrino mass at the tree level with an order one neutrino Yukawa coupling f. We observe, that the Higgs boson mass receives an additional contribution at the tree level, proportional to f, which can ameliorate the Higgs naturalness problem when f ∼ O(1). In the context of a locally supersymmetric theory, R-symmetry is mildly broken by a non-zero gravitino mass. In such a scenario, neutrino Majorana masses can be generated at the tree level as well as at the one loop level. In addition, for an order one f, we also obtain a very light bino-like neutralino with mass around a few hundred MeV. Such a light neutralino has important implications at the LHC as well as in the cosmological sector. On the other hand, the small f(∼ 10−4) case is also interesting as we obtain a sterile neutrino with mass around a few keV which can be an excellent warm dark matter candidate. The model also fares very well when studied in conjunction with the latest LHC results pertaining to different decay modes of the Higgs boson. Finally, an added advantage of this model is that it can conceive light top squarks. We also study some interesting and distinct signatures of these top squarks at the LHC.
The research was conducted under the supervision of Prof. Sourov Ray of Theoretical Physics division under the SPS [School of Physical Sciences]
The research was carried out under CSIR fellowship