Scalar Dark Matter Models with Significant Internal Bremsstrahlung

There has been interest recently on particle physics models that may give rise to sharp gamma ray spectral features from dark matter annihilation. Because dark matter is supposed to be electrically neutral, it is challenging to build weakly interacting massive particle models that may accommodate both a large cross section into gamma rays at, say, the Galactic center, and the right dark matter abundance. In this work, we consider the gamma ray signatures of a class of scalar dark matter models that interact with Standard Model dominantly through heavy vector-like fermions (the vector-like portal). We focus on a real scalar singlet S annihilating into lepton-antilepton pairs. Because this two-body final-state annihilation channel is d-wave suppressed in the chiral limit, we show that virtual internal bremsstrahlung emission of a gamma ray gives a large correction, both today and at the time of freeze-out. For the sake of comparison, we confront this scenario to the familiar case of a Majorana singlet annihilating into light lepton-antilepton pairs, and show that the virtual internal bremsstrahlung signal may be enhanced by a factor of (up to) two orders of magnitude. We discuss the scope and possible generalizations of the model.Comment: 25 pages, 10 figures, typos corrected, added references, matching version accepted by JCA

Signatures from Scalar Dark Matter with a Vector-like Quark Mediator

We present a comprehensive study of a model where the dark matter is composed of a singlet real scalar that couples to the Standard Model predominantly via a Yukawa interaction with a light quark and a colored vector-like fermion. A distinctive feature of this scenario is that thermal freeze-out in the early universe may be driven by annihilation both into gluon pairs at one-loop ($gg$) and by virtual internal Bremsstrahlung of a gluon ($q \bar{q} g$). Such a dark matter candidate may also be tested through direct and indirect detection and at the LHC; viable candidates have either a mass nearly degenerate with that of the fermionic mediator or a mass above about 2 TeV.Comment: 30 pages, 10 figures. Matches published versio

Top-philic Vector-Like Portal to Scalar Dark Matter

We investigate the phenomenology of scalar singlet dark matter candidates that couple dominantly to the Standard Model via a Yukawa interaction with the top quark and a colored vector-like fermion. We estimate the viability of this vector-like portal scenario with respect to the most recent bounds from dark matter direct and indirect detection, as well as to dark matter and vector-like mediator searches at colliders. Moreover, we take QCD radiative corrections into account in all our theoretical calculations. This work complements analyses related both to models featuring a scalar singlet coupled through a vector-like portal to light quarks, and to scenarios in which the dark matter is a Majorana singlet coupled to the Standard Model through scalar colored particles (akin to simplified models inspired by supersymmetry). Our study puts especially forward the complementarity of different search strategies from different contexts, and we show that current experiments allow for testing dark matter masses ranging up to 700 GeV and mediator masses ranging up to 6 TeV.Comment: 15 pages, 11 figures; version accepted by PR

Radiative corrections to vectorlike portal dark matter

A massive real scalar dark matter particle $S$ can couple to Standard Model leptons or quarks through a vector-like fermionic mediator $\psi$, a scenario known as the Vector-like portal. Due to helicity suppression of the annihilation cross section into a pair of SM fermions, it has been shown in previous works that radiative corrections, either at one-loop or through radiation of gauge bosons, may play a significant role both in determining the relic abundance and for indirect detection. All previous works considered the limit of massless final state quarks or leptons. In this work, we focus on a technical issue, which is to reliably determine the annihilation cross sections taking into account finite fermion masses. Following previous works in the framework of simplified supersymmetric dark matter scenarios, and building on an analogy with Higgs decay into fermions, we address the issue of infrared and collinear divergences that plagues the cross section by adopting an effective operator description, which captures most of the relevant physics and give explicit expressions for the annihilation cross sections. We then develop several approximations for the differential and total cross sections, which simplify greatly their expressions, and which can then be used in various phenomenological studies of similar models. Finally, we describe our method to compute the final gamma-ray spectrum, including hadronisation of the heavy fermions, and provide some illustrative spectra for specific dark matter candidates.Comment: 25 pages, 12 figures. One extra figure. Conclusions unchanged. Version published in PR

The Third Fermi Large Area Telescope Catalog of Gamma-ray Pulsars

We present 294 pulsars found in GeV data from the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope. Another 33 millisecond pulsars (MSPs) discovered in deep radio searches of LAT sources will likely reveal pulsations once phase-connected rotation ephemerides are achieved. A further dozen optical and/or X-ray binary systems co-located with LAT sources also likely harbor gamma-ray MSPs. This catalog thus reports roughly 340 gamma-ray pulsars and candidates, 10% of all known pulsars, compared to $\leq 11$ known before Fermi. Half of the gamma-ray pulsars are young. Of these, the half that are undetected in radio have a broader Galactic latitude distribution than the young radio-loud pulsars. The others are MSPs, with 6 undetected in radio. Overall, >235 are bright enough above 50 MeV to fit the pulse profile, the energy spectrum, or both. For the common two-peaked profiles, the gamma-ray peak closest to the magnetic pole crossing generally has a softer spectrum. The spectral energy distributions tend to narrow as the spindown power $\dot E$ decreases to its observed minimum near $10^{33}$ erg s$^{-1}$, approaching the shape for synchrotron radiation from monoenergetic electrons. We calculate gamma-ray luminosities when distances are available. Our all-sky gamma-ray sensitivity map is useful for population syntheses. The electronic catalog version provides gamma-ray pulsar ephemerides, properties and fit results to guide and be compared with modeling results.Comment: 142 pages. Accepted by the Astrophysical Journal Supplemen

Associations between depressive symptoms and disease progression in older patients with chronic kidney disease: results of the EQUAL study

Background Depressive symptoms are associated with adverse clinical outcomes in patients with end-stage kidney disease; however, few small studies have examined this association in patients with earlier phases of chronic kidney disease (CKD). We studied associations between baseline depressive symptoms and clinical outcomes in older patients with advanced CKD and examined whether these associations differed depending on sex. Methods CKD patients (>= 65 years; estimated glomerular filtration rate <= 20 mL/min/1.73 m(2)) were included from a European multicentre prospective cohort between 2012 and 2019. Depressive symptoms were measured by the five-item Mental Health Inventory (cut-off <= 70; 0-100 scale). Cox proportional hazard analysis was used to study associations between depressive symptoms and time to dialysis initiation, all-cause mortality and these outcomes combined. A joint model was used to study the association between depressive symptoms and kidney function over time. Analyses were adjusted for potential baseline confounders. Results Overall kidney function decline in 1326 patients was -0.12 mL/min/1.73 m(2)/month. A total of 515 patients showed depressive symptoms. No significant association was found between depressive symptoms and kidney function over time (P = 0.08). Unlike women, men with depressive symptoms had an increased mortality rate compared with those without symptoms [adjusted hazard ratio 1.41 (95% confidence interval 1.03-1.93)]. Depressive symptoms were not significantly associated with a higher hazard of dialysis initiation, or with the combined outcome (i.e. dialysis initiation and all-cause mortality). Conclusions There was no significant association between depressive symptoms at baseline and decline in kidney function over time in older patients with advanced CKD. Depressive symptoms at baseline were associated with a higher mortality rate in men

A Dark Matter through the Vector-like Portal

Although about a century has passed since its discovery, and despite the scientific and technological progress of our society has gone through, the nature of the Dark Matter (DM) is a mystery not yet solved. It is a big challenge for the scientific community, its identification would mean the understanding of what seemingly makes up 84% of the matter content in the Universe. We say “seemingly” because so far all evidences for DM are purely gravitational. This implies that what we call dark matter could be either a manifestation of our incomplete understanding of gravity on large scales, or a new form of matter, in particular a new kind of elementary particle. Among the plethora of possible DM candidates, this work will consider the Weakly Interactive Massive Particle (WIMP). Up to know the observed value for the relic abundance is the only solid parameter which we can count on, and the WIMP is the candidate that, through a fashionable mechanism of production, gives a result for the relic abundance in agreement with the cosmological observations. In order to demonstrate that this is indeed the valid explanation to the DM problem, a non-gravitational signal and also a model to interpret a possible Dark Matter message are needed. This may be expressed in various ways, and our approach is based on so-called simplified model. We have built a new t-channel simplified model which promotes a real scalar particle as DM and a vector-like fermion as mediator, dubbed the Vector-like Portal. In our framework, there are very few free parameters, the DM mass, the mass of the mediator and at least one Yukawa coupling. We have discovered an intriguing feature in the annihilation cross-section, a d-wave suppression in the limit of light final state fermions (compared to the DM mass). This seemingly innocuous observation will turn out to be crucial both for thermal freeze-out and for indirect searches for DM, for which higher order effects become relevant. In particular, we have performed a comprehensive analysis of the impact of next-to-leading order corrections to the annihilation cross-section, including coannihilation, as well as on elastic scattering processes. We have exploited the complementarity of direct, indirect and collider searches to set constraints on the parameter space of some simple vector-like portal scenarios, including coupling to Standard Model leptons, light quarks and the top quark. In addition, we have studied the phenomenological consequences of electroweak corrections and the detectability ofour candidate.Bien que presque un siècle ait passé depuis sa découverte, et malgré les progrès scientifiques et technologiques de notre société, la nature de la matière noire (MN) est un mystère irrésolu. C’est un grand challenge pour la communauté scientique, car sa découverte signifierait la compréhension de ce qui semble constituer 80 % du contenu en matière de l’univers. Nous disons “semble” car jusqu’à présent toutes les évidences de MN sont purement gravitationnelles. Cela implique que ce que nous appelons matière noire pourrait être soit une manifestation de notre compréhension incomplète de la gravité à grandes échelles, soit une nouvelle forme de matière, en particulier un nouveau type de particule élémentaire. Parmi la pléthore de candidats de MN possibles, ce travail considèrera la Weakly Interactive Massive Particle (WIMP). A ce jour, la valeur observée de l’abondance relique est le seul paramètre solide sur lequel nous pouvons compter, et la WIMP est le candidat qui, par un élégant mécanisme de production, donne un résultat pour l’abondance relique en accord avec les observations cosmologiques. Pour démontrer que cela est en effet l’explication valide du problème de la MN, un signal non gravitationnel ainsi qu’un modèle pour interpréter un possible message de MN sont requis. Cela peut s’exprimer de plusieurs façons, et notre approche est basée sur les modèles dits simplifiés. Nous avons construit un nouveau modèle simplifié avec le canal t qui promeut une particule scalaire réel comme MN et un fermion de type vector-like comme médiateur, et communément appelé le portail vector-like. Dans notre cadre, il y a très peu de paramètres libres, la masse de la MN, la masse du médiateur et au moins un couplage de Yukawa. Nous avons découvert une caractéristique intrigante dans la section efficace d’annihilation, une suppression de type d-wave dans la limite de fermions légers dans l’état final (en comparaison avec la masse de la MN). Il se trouve que cette observation, qui semble anodine au premier abord, est cruciale pour le freeze-out et pour les recherches indirectes de MN, pour lesquelles les effets aux ordres supérieurs deviennent relevants. En particulier, nous avons réalisé une analyse compréhensive de l’impact des corrections après l’ordre dominant de la section efficace d’annihilation, ainsi que des processus de diffusion élastique. Nous avons exploité la complémentarité des recherches directes, indirectes et aux collisionneurs afin de contraindre l’espace des paramètres de quelques scénarios simples de portails vector-like, dont le couplage au leptons du Modèle Standard et au quark top. De plus, nous avons étudié les conséquences phénoménologiques des corrections électrofaibles, et la détectabilité de notre candidat.Option Physique du Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Overview of feebly interacting particle in indirect detection searches

Axion-like particles (ALPs) as feebly interacting particles (FIPs) candidate have generated a lot of interest in the recent years. Stars are good FIPs factories and consequently those particle can be de- tected through their interaction with the interstellar medium or decay in standard particles. Brielly, I will illustrate how high-energy astro- physics observations can be exploited to set constraints to ALPs model and to the ASTRO-MeV gap problem