1,721,026 research outputs found
Interplay between Generation Mechanisms and Detection of Supersymmetric Dark Matter in the LHC Era
Get PDFThe object of this thesis is the study of several, possibly complementary, aspects of generation mechanism and detection of the two dark matter (DM) candidates provided by the Minimal Supersymmetric extension of the Standard Model (MSSM), i.e. the gravitino and the neutralino. We have first of all focused on the generation mechanism of neutralino dark matter, examining the possible consequences of relaxing some of the hypothesis on which the typically adopted thermal WIMP paradigm relies. We have, indeed, considered non-thermal dark matter production scenarios motivated, in the context of Supersymmetric theories, in supergravity and superstring frameworks. These classes of theories often feature the presence of long-lived states capable of dominating the energy budget of the Universe at early stages before possibly decaying into dark matter particles. Non thermal production have been studied in a systematic way by mean of a numerical code developed for this purpose. In particular the impact in selecting a preferred mass scale for the Dark matter and, consequently, the impact on the interpretation of new physics discovered or excluded at LHC have been discussed.
The second aspect of neutralino dark matter generation which has been investigated
is the assumption of kinetic equilibrium during the whole phase of dark matter
generation and the validity of the factorization usually implemented to rewrite the
system of coupled Boltzmann equation for each coannihilating species as a single
equation for the sum of all the number densities. To this purpose has been developed
and numerically implemented a formalism for the computation of the kinetic
decoupling temperature in the case of coannhilating particles. This formalism has
been applied to a definite scenario referred as G2-MSSM. The next topic discussed in this thesis, remaining in the context of neutralino DM, is the capability of current and next generation direct detection experiments of probing the MSSM parameter space. Focusing on some definite setups, satisfying the cosmological bounds on the DM relic density and the current particle physics constraints, the possibility for them of producing direct detection signals has been inspected through Montecarlo Simulations. The final purpose of this analysis is to show as indications about the DM properties, as provided by an experimental detection, can influence some features of the underlying Supersymmetric model which can be probed in the next future by LHC. We have finally moved the focus to the other dark matter candidate within the MSSM, i.e. the gravitino. Remarkably it is a viable dark matter candidate also in presence of R-parity violation. Gravitino dark matter have been studied in the context of a class of Supersymmetric models referred as Tree-Level Gauge Mediation (TGM). These models provide rather definite predictions for the mass of the dark matter being it related to the mechanism of mediation of SUSY breaking. In particular has been investigated a realization of TGM predicting a gravitino mass in the range 10-100 GeV. Cosmological bounds have been investigated both in presence and in absence of R-parity. The model results disfavored in case the R-parity holds, being in severe tension with Big Bang Nucleosynthesis; on the contrary is naturally feasible in presence of a small amount of R-parity violation
Axion dark matter and additional BSM aspects in an extended 2HDM setup
No full textWe illustrate and discuss the phenomenology of a model featuring a two-Higgs doublet sector augmented by two S U ( 2 ) singlet scalars. The gauge symmetry group is extended as well with a U ( 1 ) L μ − L τ component whose spontaneous breaking leads to the gauge boson which has an important effect in the muon ( g − 2 ). A global PQ symmetry is introduced upon its breaking; we have the axion particle which is also dark matter (DM) in our work. In particular, we have focused on type-X and type-II 2HDM models and found out that ( g − 2 ) cannot be explained only by the scalar sector for type-II 2HDM mainly due to stringent constraint from b → s γ resulted in M H ± > 800 GeV . For type-II 2HDM, we can have axion coupling with the gluons which generates the axion potential and possible explanation for the strong C P problem. The proposed model accommodates neutrino masses via the type-I seesaw mechanism with an upper bound on the right-handed neutrino mass 1 GeV (1 TeV) for type-II (type-X) 2HDM due to the presence of Planck scale suppressed operators. Moreover, we also have additional scalars which affect the oblique parameters and hence the W-boson mass which leads us to explain the W-boson mass observed at the CDF-II detector. The most stringent constraints on the masses and quartic couplings come from the perturbativity and potential bound from the below conditions which leads to fine-tuning among the parameters in part of the parameter space. Finally, we discuss the possible detection prospects of the axion DM and the additional gauge boson. Published by the American Physical Society 202
Thermal effects in neutrino dark matter production
Get PDFThe origin of the dark matter of the Universe and the mechanism generating light neutrino masses could be tightly linked. In this talk, based on arXiv:2308.01341, we consider the possibility to simultaneously explain oscillation data and dark matter in the form of a keV-sterile neutrino. We thoroughly study the DM production through freeze-in two-body decays, accounting for thermal effects modifying the neutrino mixing and thus the production rates. Our study shows that the freeze-in dark matter production can be efficient and thus further study is necessary to identify interesting regions of parameter space that simultaneously account for DM and neutrino masses
Minimal decaying Dark Matter and the LHC
No full textWe consider a minimal Dark Matter model with just two additional states, a Dark Matter Majorana fermion and a colored or electroweakly charged scalar, without introducing any symmetry to stabilize the DM state. We identify the parameter region where an indirect DM signal would be within the reach of future observations and the DM relic density generated fits the observations. We find in this way two possible regions in the parameter space, corresponding to a FIMP/SuperWIMP or a WIMP DM. We point out the different collider signals of this scenario and how it will be possible to measure the different couplings in case of a combined detection. © 2013 IOP Publishing Ltd and Sissa Medialab srl
Out-of-equilibrium baryogenesis and superweakly interacting massive particle dark matter
No full textThe experimental fact that the energy density in dark matter (DM) and in baryons is of the same order is one of the most puzzling in cosmology. In this work we suggest a new mechanism able to explain this coincidence in the context of out-of-equilibrium baryogenesis with DM production á la SuperWIMP starting from the same initial particle. Two simple implementations of this scenario within supersymmetric models with gravitino DM are discussed. © 2014 American Physical Society
LHC prospects for minimal decaying dark matter
No full textWe study the possible signals at LHC of the minimal models of decaying dark matter. Those models are characterized by the fact that DM interacts with SM particles through renormalizable coupling with an additional heavier charged state. Such interaction allows to produce a substantial abundance of DM in the early Universe via the decay of the charged heavy state, either in- or out-of-equilibrium. Moreover additional couplings of the charged particle open up decay channels for the DM, which can nevertheless be sufficiently long-lived to be a good DM candidate and within reach of future Indirect Detection observations. We compare the cosmologically favored parameter regions to the LHC discovery reach and discuss the possibility of simultaneous detection of DM decay in Indirect Detection
3.55 keV line in minimal decaying dark matter scenarios
No full textWe investigate the possibility of reproducing the recently reported 3.55 keV line in some simple decaying dark matter scenarios. In all cases a keV scale decaying DM is coupled with a scalar field charged under SM gauge interactions and thus capable of pair production at the LHC. We will investigate how the demand of a DM lifetime compatible with the observed signal, combined with the requirement of the correct DM relic density through the freeze-in mechanism, impacts the prospects of observation at the LHC of the decays of the scalar field. © 2015 IOP Publishing Ltd and Sissa Medialab srl
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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