118917259
Relating leptogenesis and dark matter
A scenario that relates the abundance of dark matter to the baryon asymmetry of the Universe is presented. In this scenario, based on a left-right extension of the Standard Model, dark matter is made of light, ~ 1 GeV, right-handed Majorana neutrinos.
54812047
Light scalar WIMP through the Higgs portal and CoGeNT
If dark matter (DM) simply consists in a scalar particle interacting dominantly with the Higgs boson, the ratio of its annihilation cross section--which is relevant both for the relic abundance and indirect detection--and its spin-independent scattering cross section on nuclei depends only on the DM mass. It is an intriguing result that, fixing the mass and direct detection rate to fit the annual modulation observed by the DAMA experiment, one obtains a relic density in perfect agreement with its observed value. In this article we update this result and confront the model to the recent CoGeNT data, tentatively interpreting the excess of events in the recoil energy spectrum as being due to DM. CoGeNT, as DAMA, points toward a light DM candidate, with somewhat different (but not necessarily incompatible) masses and cross sections. For the CoGeNT region too, we find an intriguing agreement between the scalar DM relic density and direct detection constraints. We give the 1{sigma} region favored by the CDMS-II events, and our exclusion limits for the Xenon10 (2009) and Xenon100 data, which, depending on the scintillation efficiency, may exclude CoGeNT and DAMA. Assuming CoGeNT and/or DAMA to be due to scalar singlet DM leads to definite predictionsmore » regarding indirect detection and at colliders. We specifically emphasize the limit on the model that might be set by the current Fermi-LAT data on dwarf galaxies, and the implications for the search for the Higgs at the LHC.« less
119198386
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, σfv∝v4, 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.
119185262
Complementarity of Galactic radio and collider data in constraining WIMP dark matter models
In this work we confront dark matter models to constraints that may be derived from radio synchrotron radiation from the Galaxy, taking into account the astrophysical uncertainties and we compare these to bounds set by accelerator and complementary indirect dark matter searches. Specifically we apply our analysis to three popular particle physics models. First, a generic effective operator approach, in which case we set bounds on the corresponding mass scale, and then, two specific UV completions, the Z' and Higgs portals. We show that for many candidates, the radio synchrotron limits are competitive with the other searches, and could even give the strongest constraints (as of today) with some reasonable assumptions regarding the astrophysical uncertainties.
31124116
Spontaneous baryogenesis with observable CP violation.
Using a left-right symmetric model with spontaneous [ital CP] violation and the hypothesis of a weakly first-order electroweak phase transition we derive a relation between the produced baryon asymmetry and the observed parameter [var epsilon], describing [ital CP] violation in the [ital K] system.
119212974
The inert doublet model: a new archetype of WIMP dark matter?
The Inert Doublet Model (IDM) is a two doublet extension of the Higgs-Brout-Englert sector of the Standard Model with a Z2 symmetry in order to prevent FCNC. If the Z2 symmetry is not spontaneously broken, the lightest neutral extra scalar is a dark matter candidate. We briefly review the phenomenology of the model, emphasizing its relevance for the issue of Electroweak Symmetry Breaking (EWSB) and the prospects for detection of dark matter.
55047377
Optical characterization of n = 1.03 silica aerogel used as radiator in the RICH of HERMES
The optical properties of silica aerogel tiles with a refractive index of 1.03 and dimensions 11]11] 1c m 3, produced by the Matsushita Electric Works (Japan), have been measured in the wavelength range from 200 to 900 nm. The tiles are used as one of the two radiators of the ring imaging Cherenkov counter of the HERMES experiment at DESY-HERA. The transmittance of light has been measured on 200 tiles by means of a double beam spectrophotometer. The light trans#ectance and re#ectance have been measured on one tile by means of a single-beam spectrophotometer and an integrating re#ecting sphere. Typical values of the measured transmittances at a wavelength j"400 nm are around 0.67. The measured trans#ectance increases almost linearly from 0.4 to 0.96 in the interval 200}300 nm, and remains nearly constant at the value 0.95 in the complementary j-range. The measured re#ectance, mostly con"ned below 400 nm, is completely interpretable as backscattering from inside the aerogel, revealing an absence of light re#ection at the aerogel surfaces. The transmittance data have been "tted with the Hunt formula, whose parameters have been used to evaluate the number of unscattered and scattered Cherenkov photons produced by aerogel. For stacks of 5 tiles and quantum
125760852
Diffractive vector meson production at intermediate energies.
119748220
New results from hermes
202096488
Particle identification with the HERMES RICH
Abstract In early 1998 a dual-radiator RICH detector was installed into the HERMES spectrometer. It is designed to allow hadron identification over the HERMES kinematic range (2–20 GeV) using both an aerogel and C 4 F 10 gas radiator. Three different approaches that are currently pursued for particle identification are presented.
15360804
SUSY Searches in All-Hadronic States with Large MET at the LHC
The CMS and ATLAS search strategy for SUSY in inclusive multijet plus high missing transverse energy final states is reviewed. This canonical SUSY signature may be a viable discovery channel for low mass SUSY in the early phase of the LHC. Methods for Standard Model background estimates, MET studies and filters for instrumental background are presented.