京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20914号 / 理博第4366号 / 新制||理||1626(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 國廣 悌二, 教授 川合 光, 教授 永江 知文 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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The lack of direct evidence for physics beyond the SM at the LHC has led some to reevaluate the need for such physics to solve the hierarchy problem. Instead, the notion that the SM, or something like it, is valid up to the Planck scale and that technical naturalness is sufficient for solving the hierarchy problem has been suggested. This thesis examines minimal extensions of the SM that address its phenomenological and theoretical shortcomings while avoiding new physics between the electroweak and Planck scales that introduces a hierarchy problem. This thesis first studies two issues with the vMSM - an extension of the SM by three right-handed neutrinos - and their possible solutions. The first issue is the tension between dark matter production in the nuMSM and constraints from the Lyman-alpha forest data. To avoid this tension, the vMSM is extended by a Higgs singlet Φ and neutrino dark matter is produced through the decays of Φ rather than through left-right neutrino mixing. It is shown that the hierarchical parameters of this model can arise from symmetries broken at or near the Planck scale for two specific examples: one in which Φ stabilizes the electroweak vacuum and one in which Φ is a light inflaton. The second issue pertains to Higgs ξ-inflation. In the vMSM, a large non-minimal coupling ξ of the Higgs to gravity gives inflation but leads to a possible violation of perturbative unitarity below the inflationary scale. A study of Higgs ξ-inflation with M_h ≃ 125-126 GeV, for which the Higgs self-coupling λ runs to small values near the Planck scale, is carried out. It is shown that small λ can significantly reduce ξ required for inflation, but ξ cannot be small enough to address the possible unitarity issue. For small λ, a new region of Higgs ξ-inflation with a large tensor-to-scalar ratio r that is consistent with BICEP2 is discovered. This thesis then studies the technical naturalness and cosmology of a model that addresses the strong CP problem. It is shown that a classically scale invariant DFSZ invisible aξon model with a Peccei-Quinn scalar S, whose couplings to the SM are ultra-weak, can solve the strong CP problem and generate electroweak symmetry breaking via the Coleman-Weinberg mechanism. The ultra-weak couplings of S are natural due to an underlying approξmate shift symmetry. The model contains a light pseudo-Goldstone dilaton that can be consistent with cosmological bounds while the aξon can be the dark matter of the universe. Finally, a summary of the thesis is presented and future research topics are suggested.

Les collisions d'ions lourds ultra-relativistes offrent la possibilité de créer des conditions de température et de densité suffisantes pour conduire la matière nucléaire à un état de partons déconfinés appelé le plasma de quarks et de gluons. <br />La production des baryons étranges est l'une des observables essentielles pour la compréhension des mécanismes opérant dans le milieu. <br />De plus, certaines prédictions théoriques envisagent la possibilité de production de dibaryons étranges, particules encore hypothétiques, dont la preuve de l'existence aurait des conséquences importantes en physique nucléaire et en astrophysique. <br />Les expériences STAR et, bientôt, ALICE, installées respectivement auprès des collisionneurs RHIC et LHC, rendent accessible la recherche des baryons et des dibaryons étranges.<br /><br />Une simulation consacrée au dibaryon métastable $\rm {H^0}$ dans son mode de désintégration $\Lambda p \pi^-$ a permis de calculer la sensibilité de STAR à une telle particule. La recherche de ce $\rm {H^0}$ ainsi que celle de la résonance $\Xi^-p$ ont été menées dans les données Au+Au de STAR aux énergies de $\sqrt{s_{NN}}=62.4$ et $200~GeV$.<br /><br />Dans le cadre de la préparation aux premières données Pb+Pb de l'expé-rience ALICE, plusieurs simulations ont permis d'estimer les performances du détecteur quant à l'identification des baryons étranges $\Lambda$, $\Xi$ et $\Omega$. Afin de favoriser leur efficacité de reconstruction dans une large gamme d'impulsion transverse tout en gardant un rapport S/B raisonnable, l'influence des sélections géométriques et de la taille de la zone de reconstruction a été soulignée. Par ailleurs, la sensibilité d'ALICE à l'identification des dibaryons étranges métastables ${\rm H^0}$ et $(\Xi^0p)_b$, ainsi que celle de la résonance $\Lambda\Lambda$, a été calculée.

Big Bang Nucleosynthesis (BBN), together with the analyses of the Cosmic Microwave Background (CMB) anisotropies, confirm what our day to day experience of life attests : antimatter is far less present than matter in the Universe. In addition, these observables also permit to evaluate that there exists about one proton for every 10^{10} photons present in the Universe. This is in contradiction with expectations coming from the standard hot big bang, where no distinction between matter and antimatter is made, and where subsequent annihilations would lead to equal matter and antimatter contents, at a level 10^{−10} smaller than the observed one. The Standard Model of fundamental interactions fails to explain this result, leading us to search for ‘Beyond the Standard Model’ physics. Among the possible mechanism which could be responsible for the creation of such a matter asymmetry, leptogenesis is particularly attractive because it only relies on the same ingredients previously introduced to generate neutrino masses. Unfortunatelly, this elegant proposal suffers from a major difficulty : it resists to any tentative of being probed by our low energy observables. In this thesis, we tackle the problem the other way around and propose a way to falsify this mechanism. Considering the type-I leptogenesis mechanism, i.e. a mechanism based on the asymmetric decay of right-handed neutrinos, in a left-right symmetric framework, we show that the observation of a right-handed gauge boson W_R at future colliders would rule out any possibility for such mechanism to be responsible of the matter asymmetry present in our Universe. Another intriguing question that analyses of the anisotropies of the CMB confirmed is the presence of a non-baryonic component of matter in our Universe, i.e. the dark matter. As hinted by observations of galactic rotation curves, it should copiously be present in our galactic halo, but is notoriously difficult to detect directly. We can take advantage on the fact that antimatter almost disappeared from our surroundings to detect the contamination of cosmic rays from standard sources the annihilation products of dark matter would produce. The second subject tackled in this work is the study of the imprints the Inert Doublet Modem (IDM) could leave in (charged) cosmic rays, namely positrons, antprotons and antideuterons. This model, first proposed to allow the Bout-Englert-Higgs particle to evade the Electroweak Precision Test (EWPT) measurements, introduces an additional scalar doublet which is inert in the sense that it does not couple directly to fermions. This latter property brings an additional virtue to this additional doublet : since it interacts weakly with particles, it can play the role of dark matter. This study will be done in the light of the data recently released by the PAMELA, ATIC and Fermi-GLAST collaborations, which reported e^± excesses in two different energy ranges.

We have released maps and data for five years of observation of the cosmic microwave background with the Wilkinson Microwave Anisotropy Probe (WMAP) and I will review the main results in this talk. A simple 6 parameter cosmological model continues to be an excellent fit to the CMB data and to our data in conjunction with other astrophysical measurements. In particular a running spectral index is not supported by the data, and constraints that the Universe is spatially flat have increased in precision. Increased sensitivity and improvements in our understanding of the instrumental beam shape have allowed us to measure for the first time a cosmic neutrino background. Neutrinos de-coupled from other matter earlier than photons did. While they are expected to have a 2 Kelvin thermal distribution today, they comprised 10% of the energy density of the Universe at the epoch of photon de-coupling. The data also allow tighter constraints on the shape of the inflationary potential via the amplitude of a gravitational wave background new constraints on features of cosmic axions. Recorded at TRIUMF on Thursday April 17, 2008.

Title: Study of strange particle production in jets with the ALICE experiment at the LHC Author: Vít Kučera Institute: Institute of Particle and Nuclear Physics Supervisors: RNDr. Jana Bielčíková, Ph.D., Nuclear Physics Institute of the CAS; Dr. Christian Kuhn, Institut Pluridisciplinaire Hubert CURIEN Abstract: Quark-gluon plasma is a state of matter existing under extreme energy densities and temperatures where quarks and gluons are deconfined. Complex phenomena occurring in the plasma emerge from the strong interaction of its constituents. This hot and dense strongly interacting matter can be created in ultra-relativistic heavy-ion collisions and its properties can be studied by measuring particles produced in the collisions. Partons produced in hard scatterings interact with the medium which modifies the production of particles in jets. Measurements of spectra of identified particles produced in jets represent an important tool for understanding the interplay of various hadronization mechanisms which contribute to the particle production in the medium created in heavy-ion collisions. In this thesis, we present the measurement of the pT spectra of Λ baryons and K0 S mesons produced in charged jets in central Pb-Pb collisions at the energy √ sNN = 2.76 TeV, measured in the ALICE experiment at the LHC. The...

The first-time measurement of the angular dependence of the beam-helicity asymmetry for $\gamma p \rightarrow pK^{+}K^{-}$ is shown and compared to $\gamma p \rightarrow p\pi^{+}\pi^{-}$. The data obtained were from the CLAS g12 experiment at Jefferson Lab. The experiment utilized a beam of circularly polarized photons with energies between 1.1 and 5.4 GeV incident on an unpolarized liquid hydrogen target, which produced an unprecedented number of strange hadrons in photoproduction. The production mechanism for strange hadrons is not well understood. The beam-helicity asymmetry is a polarization observable that provides information on interfering production mechanisms in the reaction. It is shown that the asymmetry is sensitive to several kinematic variables that are key in modeling the reaction dynamics. Furthermore, the comparison of the beam-helicity asymmetry between the kaon and pion channels serves as a platform for the investigation of flavor dependence. A partial wave analysis on the $pK^{-}$ system is also performed in a search for missing hyperon excitations.

Orientador: Pedro Cunha de Holanda / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-31T06:55:32Z (GMT). No. of bitstreams: 1 Sato_EduardoAkio_M.pdf: 2319995 bytes, checksum: fc82384c799d5812bf14a71fe2723e2d (MD5) Previous issue date: 2016 / Resumo: Nesta dissertação analiso como uma classe de modelos sugeridos para acomodar neutrinos massivos no modelo padrão, os assim chamados mecanismos seesaw, podem também resolver o problema de assimetria bariônica no universo. Os requisitos mínimos para uma geração dinâmica bem sucedida de assimetria bariônica, conhecidos como condições de Sakharov, são: não conservação de número bariônico, violação de simetria CP e ausência de equilíbrio térmico. Para mostrar que mecanismos seesaw respeitam estas regras, reviso alguns tópicos como: a violação de número bariônico através do processo de sphalerons, a teoria de violação de CP através de invariantes de base fraca e a mecânica estatística de não equilíbrio através da equação de Boltzmann. Como exemplo considero um cenário de mecanismo seesaw tipo I (3+3) com massas de neutrinos estéreis altamente hierárquicas. A assimetria observada impõe um limite inferior na massa dos neutrinos estéreis ($M_1 \geq 8.4 \times 10^{8} \; \text{GeV}$) e um limite superior na massa dos neutrinos ativos ($m_1 < 0.11 \; \text{eV}$), consistente com limites previamente obtidos na literatura / Abstract: In this dissertation I analyse how a class of models suggested to accommodate massive neutrinos in the standard model, the so-called seesaw mechanisms, can also solve the baryon asymmetry of the universe problem. The minimal requisites to a successful dynamical generation of baryon asymmetry, known as Sakharov's conditions, are: Non-conservation of baryon number, violation of CP symmetry and absence of thermal equilibrium. To show that seesaw mechanisms respect those rules, I review some topics such as: the standard model baryon non-conservation via sphalerons process, the theory of CP violation via weak-basis invariants and non-equilibrium statistical physics via Boltzmann equation. As a example I consider a type I (3+3) seesaw mechanism scenario with highly hierarchical sterile neutrino masses and the observed asymmetry impose a lower bound in the sterile neutrino masses ($M_1 \geq 8.4 \times 10^{8} \; \text{GeV}$) and a upper bound in the active neutrino masses ($m_1 < 0.11 \; \text{eV}$), consistent with limits previously obtained in the literature / Mestrado / Física / Mestre em Física / 1370441/2014 / CAPES

Le modèle ΛCDM de la cosmologie repose sur l’existence d’une composante exotique, appelée énergie noire, pour expliquer l’accélération tardive de l’expansion de l’univers à z < 0.7. Des alternatives à cette constante cosmologique proposent de modifier la théorie de la gravitation basée sur la relativité générale aux échelles cosmologiques. Depuis l’automne 2014, le multi-spectrographe SDSS-eBOSS effectue un relevé de quasars dans un domaine en redshift peu exploré entre 0.8 ≤ z ≤ 2.2 dont l’un des objectifs majeurs est d’étendre les contraintes sur la nature de l’énergie noire et de tester la validité de la théorie de la relativité générale à plus haut redshift en utilisant les quasars comme traceurs de la matière.Dans cette thèse, nous mesurons et analysons la fonction de corrélation à deux points de l’échantillon de quasars obtenu après deux ans d'observation de eBOSS pour contraindre les distances cosmiques, à savoir la distance angulaire DA et le taux d'expansion H, ainsi que le taux de croissance des structures fσ8 à un redshift effectif Zeff = 1.52. Nous commençons par construire des catalogues des grandes structures qui prennent en compte la géométrie angulaire et radiale du relevé. Puis pour obtenir des contraintes robustes, nous identifions plusieurs sources d’effets systématiques, en particulier ceux liés à la modélisation et aux observations sont étudiées avec des « mock catalogues » dédiés qui correspondent à des réalisations fictives de l’échantillon de quasars eBOSS. Les paramètres cosmologiques de ces catalogues fictifs étant connus, ils sont utilisés comme référence pour tester notre procédure d’analyse. Les résultats de ce travail sur l’évolution des distances cosmiques sont compatibles avec les prédictions du modèle ΛCDM utilisant les paramètres de Planck et basé sur l’existence d’une constante cosmologique. La mesure du taux de croissance des structures est compatible avec la prédiction de ce modèle basé sur la relativité générale, ce qui étend ainsi la validité de la théorie aux échelles cosmologiques à grand redshift. Nous utilisons également notre mesure pour mettre à jour les contraintes sur les modèles d'extensions à ΛCDM et sur les scénarios de gravité modifiée. Ce travail de thèse constitue une première étude menée avec les données de quasars eBOSS et sera utilisée pour l’analyse de l’échantillon final à la fin 2019 ou l’on attend une amélioration de la précision statistique d’un facteur 2. Associé à BOSS, eBOSS ouvrira la voie pour les futurs programmes d’observation, comme le télescope au sol DESI et le satellite Euclid. Ces deux programmes sonderont intensivement l’époque de l’univers entre 1 < z < 2 en observant plusieurs millions de spectres, ce qui permettra d'améliorer d'un ordre de grandeur au moins les contraintes actuelles sur les paramètres cosmologiques. / The ΛCDM model of cosmology assumes the existence of an exotic component, called dark energy, to explain the late-time acceleration of the expansion of the universe at redshift z < 0.7. Alternative scenarios to this cosmological constant suggest to modify the theory of gravitation based on general relativity at cosmological scales. Since fall 2014, the SDSS-IV eBOSS multi-object spectrograph has undertaken a survey of quasars in the almost unexplored redshift range 0.8 ≤ z ≤ 2.2 with the key science goal to complement the constraints on dark energy and extend the test of general relativity at higher redshifts by using quasars as direct tracers of the matter field.In this thesis work, we measure and analyse the two-point correlation function of the two-year data taking of eBOSS quasar sample to constrain the cosmic distances, i.e. the angular diameter distance DA and the expansion rate H, and the growth rate of structure fσ8 at an effective redshift Zeff = 1.52. First, we build large-scale structure catalogues that account for the angular and radial incompleteness of the survey. Then to obtain robust results, we investigate several potential systematics, in particular modeling and observational systematics are studied using dedicated mock catalogs which are fictional realizations of the data sample. These mocks are created with known cosmological parameters such that they are used as a benchmark to test the analysis pipeline. The results on the evolution of distances are consistent with the predictions for ΛCDM with Planck parameters assuming a cosmological constant. The measurement of the growth of structure is consistent with general relativity and hence extends its validity to higher redshift. We also provide updated constraints on extensions of ΛCDM and models of modified gravity. This study is a first use of eBOSS quasars as tracers of the matter field and will be included in the analysis of the final eBOSS sample at the end of 2019 with an expected improvement on the statistical precision of a factor 2. Together with BOSS, eBOSS will pave the way for future programs such as the ground-based Dark Energy Spectroscopic Instrument (DESI) and the space-based mission Euclid. Both programs will extensively probe the intermediate redshift range 1 < z < 2 with millions of spectra, improving the cosmological constraints by an order of magnitude with respect to current measurements.