Search

We discuss within the framework of effective four-fermion scalar interaction the phenomenology of a weakly interacting massive particle (WIMP) Dirac dark matter candidate which is exothermic (i.e., is metastable and interacts with nuclear targets down-scattering to a lower-mass state) and Ge-phobic (i.e., whose couplings to quarks violate isospin symmetry leading to a suppression of its cross section off Germanium targets). We discuss the specific example of the CDMS-II Silicon three-candidate effect showing that a region of the parameter space of the model exists where WIMP scatterings can explain the excess in compliance with other experimental constraints, while at the same time the dark matter particle can have a thermal relic density compatible with observation. In this scenario the metastable state Χ and the lowest-mass one Χ' have approximately the same density in the present Universe and in our Galaxy, but direct detection experiments are only sensitive to the down-scatters of Χ to Χ'. We include a discussion of the recently calculated next-to-leading order corrections to dark matter-nucleus scattering, showing that their impact on the phenomenology is typically small, but can become sizable in the same parameter space where the thermal relic density is compatible to observation. [ABSTRACT FROM AUTHOR]

We analyze the phenomenological consequences of assuming that the 125 GeV boson measured at the LHC coincides with one of the two CP-even Higgs bosons of an effective minimal supersymmetric extension of the Standard Model at the electroweak scale. We consider the two ensuing scenarios and discuss critically the role of the various experimental data (mainly obtained at colliders and at B factories) which provide actual or potential constraints to supersymmetric properties. Within these scenarios, properties of neutralinos as dark matter particles are analyzed from the point of view of their cosmological abundance and rates for direct and indirect detections. [ABSTRACT FROM AUTHOR]

We address the problem of a search at the LHC for a neutralino whose mass is around 10 GeV, i.e. in the range of interest for present data of direct search for dark matter particles in the galactic halo. This light neutralino is here implemented in an effective Minimal Supersymmetric extension of the Standard Model at the electroweak scale without requirement of a gaugino mass unification at a grand unification scale. In this model, light neutralinos that have the right cosmological properties and are able to explain current results of direct dark matter detection naturally arise. Within this model we identify a specific benchmark which maximizes chances of detection at the LHC, and we determine its prospects of reconstructing the main features of the light neutralino framework at different stages of the LHC runs. Our main result is that the LHC will hardly properly reconstruct the mass of such a light neutralino, due to the intrinsic difficulty in reconstructing the mass of light stable particles in relativistic events. However, the associated measurement of the mass of the heavier neutralinos allows us to point toward the right pattern of gaugino nonuniversality. Other relevant parameters of this model, like slepton and squark masses, can be reconstructed to a good level of precision. [ABSTRACT FROM AUTHOR]

We discuss the impact for light neutralinos in an effective minimal supersymmetric extension of the standard model of the recent results presented by the CMS and ATLAS Collaborations at the CERN Large Hadron Collider for a search of supersymmetry in proton-proton collisions at a center-of-mass energy of 7 TeV with an integrated luminosity of 35 pb-1. We find that, in the specific case of light neutralinos, efficiencies for the specific signature searched by ATLAS (jets+ missing transverse energy and an isolated lepton) imply a lower sensitivity compared to CMS (which searches for jets+ missing transverse energy). Focusing on the CMS bound, if squark soft masses of the three families are assumed to be degenerate, the combination of the ensuing constraint on squark and gluino masses with the experimental limit on the b→s+γ decay imply a lower bound on the neutralino mass mχ that can reach the value of 11.9 GeV, depending on the gluino mass. On the other hand, when the universality condition among squark soft parameters is relaxed, the lower bound on mχ is not constrained by the CMS measurement and then remains at the value 7.5 GeV derived in previous papers. [ABSTRACT FROM AUTHOR]

We examine the status of light neutralinos in an effective minimal supersymmetric extension of the standard model at the electroweak scale which was considered in the past and discussed in terms of the available data of direct searches for dark matter particles. Our reanalysis is prompted by new measurements at the Tevatron and B factories which might potentially provide significant constraints on the minimal supersymmetric extension of the standard model. Here we examine in detail all these new data and show that the present published results from the Tevatron and B factories have only a mild effect on the original light-neutralino population. This population, which fits quite well the DAMA/LIBRA annual modulation data, would also agree with the preliminary results of CDMS, CoGeNT, and CRESST, should these data, which are at present only hints of excesses of events over the expected backgrounds, be interpreted as authentic signals of dark matter. For the neutralino mass we find a lower bound of 7-8 GeV. Our results differ from some recent conclusions by other authors because of a few crucial points which we try to single out and elucidate. [ABSTRACT FROM AUTHOR]

We discuss the compatibility of the combined annual modulation effect measured by DAMA/LIBRA-phase1 and DAMA/LIBRA-phase2 with an explanation in terms of inelastic scattering events induced by the most general Galilean-invariant effective contact interaction of a weakly interacting massive particle (WIMP) dark matter particle of spin 0, 1/2 or 1. We take into account all the possible interferences among operators by studying the intersections among the ellipsoidal surfaces of constant signal of DAMA and other experiments in the space of the coupling constants of the effective theory. In our analysis we assume a standard Maxwellian velocity distribution in the Galaxy. We find that, compared to the elastic case, inelastic scattering partially relieves but does not eliminate the existing tension between the DAMA effect and the constraints from the null results of other experiments. Such tension is very large in all the parameter space with the exception of a small region for WIMP mass mχ≃10 GeV and mass splitting δ≳20 keV, where it is partially, but not completely relieved. In such region the bounds from fluorine targets are evaded in a kinematic way because the minimal WIMP incoming speed required to trigger upscatters off fluorine exceeds the maximal WIMP velocity in the Galaxy, or is very close to it. As a consequence, we also find that the residual tension between DAMA and other results is considerably more sensitive on the astrophysical parameters compared to the elastic case. We find that the configurations with the smallest tension can produce enough yearly modulation in some of the DAMA bins in compliance with the constraints from other experiments, but the ensuing shape of the modulation spectrum is too steep compared to the measured one. For such configurations the recent COSINE-100 bound is evaded in a natural way due to their large expected modulation fractions. [ABSTRACT FROM AUTHOR]

We show that the weakly interacting massive particle scenario of proton-philic spin-dependent inelastic dark matter (pSIDM) can still provide a viable explanation of the observed DAMA modulation amplitude in compliance with the constraints from other experiments after the release of the DAMA/LIBRA-phase2 data and including the recent bound from COSINE-100, that uses the same NaI target of DAMA. The pSIDM scenario provided a viable explanation of DAMA/LIBRA-phase1 both for a Maxwellian WIMP velocity distribution and in a halo-independent approach. At variance with DAMA/LIBRA-phase1, for which the modulation amplitudes showed an isolated maximum at low energy, the DAMA/LIBRA-phase2 spectrum is compatible to a monotonically decreasing one. Moreover, due to its lower threshold, it is sensitive to WIMP-iodine interactions at low WIMP masses. Due to the combination of these two effects pSIDM can now explain the yearly modulation observed by DAMA/LIBRA only when the WIMP velocity distribution departs from a standard Maxwellian. In this case the WIMP mass mχ and mass splitting δ fall in the approximate ranges 7 GeV≲mχ≲17 GeV and 18 keV≲δ≲29 keV. The recent COSINE-100 bound is naturally evaded in the pSDIM scenario due to its large expected modulation fractions. [ABSTRACT FROM AUTHOR]

We analyze the phenomenological consequences of assuming that the 125 GeV boson measured at the LHC coincides with one of the two CP-even Higgs bosons of an effective minimal supersymmetric extension of the Standard Model at the electroweak scale. We consider the two ensuing scenarios and discuss critically the role of the various experimental data (mainly obtained at colliders and at B factories) which provide actual or potential constraints to supersymmetric properties. Within these scenarios, properties of neutralinos as dark matter particles are analyzed from the point of view of their cosmological abundance and rates for direct and indirect detections. [ABSTRACT FROM AUTHOR]

We review the status of the phenomenology of light neutralinos in an effective minimal supersymmetric extension of the standard model at the electroweak scale, in light of new results obtained at the CERN Large Hadron Collider. First, we consider the impact of the new data obtained by the CMS Collaboration on the search for the Higgs-boson decay into a tau pair, and by the CMS and LHCb Collaborations on the branching ratio for the decay Bs → &mgr;+ + &mgr;-. Then, we examine the possible implications of the excess of events found by the ATLAS and CMS Collaborations in a search for a standard-model (SM)-lik;e Higgs boson around a mass of 126 GeV, with a most likely mass region (95% C.L.) restricted to 115.5-131 GeV (global statistical significance about 2.3&sgr;). From the first set of data, we update the lower bound of the neutralino mass to be about 18 GeV. From the second set of measurements, we derive that the excess around mSMH = 126 GeV, which however needs a confirmation by further runs at the LHC, would imply a neutralino in the mass range 18 GeV ≲ mx ≲ 38 GeV, with neutraUno-nucleon elastic cross sections fitting well the results of the dark matter direct search experiments DAMA/LIBRA and CRESST. [ABSTRACT FROM AUTHOR]

The long-standing model-independent annual modulation effect measured by the DAMA Collaboration, which fulfills all the requirements of a dark matter annual modulation signature, and the new result by the CoGeNT experiment that shows a similar behavior are comparatively examined under the hypothesis of a dark matter candidate particle interacting with the detectors' nuclei by a coherent elastic process. The ensuing physical regions in the plane of the dark matter-particle mass versus the dark matter-particle nucleon cross-section are derived for various galactic halo models and by taking into account the impact of various experimental uncertainties. It is shown that the DAMA and the CoGeNT regions agree well between each other and are well fitted by a supersymmetric model with light neutralinos which satisfies all available experimental constraints, including the most recent results from CMS and ATLAS at the CERN Large Hadron Collider. [ABSTRACT FROM AUTHOR]