118864268
Constraints on light WIMP candidates from the isotropic diffuse gamma-ray emission
Motivated by the measurements reported by direct detection experiments, most notably DAMA, CDMS-II, CoGeNT and Xenon10/100, we study further the constraints that might be set on some light dark matter candidates, MDM ~ few GeV, using the Fermi-LAT data on the isotropic gamma-ray diffuse emission. In particular, we consider a Dirac fermion singlet interacting through a new Z' gauge boson, and a scalar singlet S interacting through the Higgs portal. Both candidates are WIMP (Weakly Interacting Massive Particles), i.e. they have an annihilation cross-section in the pbarn range. Also they may both have a spin-independent elastic cross section on nucleons in the range required by direct detection experiments. Although being generic WIMP candidates, because they have different interactions with Standard Model particles, their phenomenology regarding the isotropic diffuse gamma-ray emission is quite distinct. In the case of the scalar singlet, the one-to-one correspondence between its annihilation cross-section and its spin-independent elastic scattering cross-section permits to express the constraints from the Fermi-LAT data in the direct detection exclusion plot, σn0−MDM. Depending on the astrophysics, we argue that it is possible to exclude the singlet scalar dark matter candidate at 95% confidence level. The constraints on the Dirac singlet interacting through a Z' are comparatively weaker.
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.
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.
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.
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.
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
125736234
Recent HERMES Results on Inclusive Scattering and Exclusive Reactions
125760852
Diffractive vector meson production at intermediate energies.
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.
13891794
Vector meson production at HERMES.
Diiractive production of , , ! and J== mesons is observed at the Hermes experiment at DESY. Hermes scatters the 27.5 GeV longitudinally polarised positrons of the HERA storage ring oo an internal gas storage cell target. Polarised and unpolarised gas targets of diierent types are used. The exclusive production from diierent nuclear targets (H, D, 3 He and 14 N) shows coherent and incoherent contributions that depend on the atomic mass A and Q 2. For 3 He the incoherent contribution is smaller than for H and D. The nuclear transparency T has been extracted as a function of Q 2 and and shows no signiicant signal of color transparency eeects. The polari-sation of beam and target at Hermes will allow for the world's rst measurement of double-spin asymmetries in combination with decay angle information. This will allow a nearly complete characterization of the angular momentum structure of the reaction. First results for the longitudinal and linear polarisation of-mesons and for the ratio of the longitudinal versus transverse cross section of-mesons as a function of Q 2 are presented. J== mesons are observed at Hermes in the muonic and the electronic decay channel. As they are produced by photon-gluon fusion processes, the observed spin asymmetry from polarised target data contains information about the gluon spin distribution in the nucleon. As the available statistics is marginal for a determination of G, Hermes currently performs an upgrade of the spectrometer. A ring image Cerenkov detector, a muon detector and a small angle spectrometer will be installed in 1998 and an additional vertex detector in 1999. The upgrade will improve the identiication of charmed and strange mesons, the detection of heavy decaying and slow recoil particles and the detection of the scattered positron in low-Q 2 (photoproduction) events.
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.