1,721,020 research outputs found
Inverse Compton constraints on the Dark Matter e± excesses
Full text linkRecent results from experiments like PAMELA have pointed to excesses of e± in cosmic rays. If interpreted in terms of Dark Matter annihilations, they imply the existence of an abundant population of e± in the galactic halo at large. We consider the high energy gamma ray fluxes produced by Inverse Compton Scattering of interstellar photons on such e±, and compare them with the available data from EGRET and some preliminary data from FERMI. We consider different observation regions of the sky and a range of DM masses, annihilation channels and DM profiles. We find that large portions of the parameter space are excluded, in particular for DM masses larger than 1 TeV, for leptonic annihilation channels and for benchmark Einasto or NFW profiles. © 2009 Elsevier B.V. All rights reserved
You can hide but you have to run: direct detection with vector mediators
Full text linkWe study direct detection in simplified models of Dark Matter (DM) in which interactions with Standard Model (SM) fermions are mediated by a heavy vector boson. We consider fully general, gauge-invariant couplings between the SM, the mediator and both scalar and fermion DM. We account for the evolution of the couplings between the energy scale of the mediator mass and the nuclear energy scale. This running arises from virtual effects of SM particles and its inclusion is not optional. We compare bounds on the mediator mass from direct detection experiments with and without accounting for the running. In some cases the inclusion of these effects changes the bounds by several orders of magnitude, as a consequence of operator mixing which generates new interactions at low energy. We also highlight the importance of these effects when translating LHC limits on the mediator mass into bounds on the direct detection cross section. For an axial-vector mediator, the running can alter the derived bounds on the spin-dependent DM-nucleon cross section by a factor of two or more. Finally, we provide tools to facilitate the inclusion of these effects in future studies: general approximate expressions for the low energy couplings and a public code runDM to evolve the couplings between arbitrary energy scales
Helioseismology with long-range dark matter-baryon interactions
Full text linkAssuming the existence of a primordial asymmetry in the dark sector, we study how long-range dark matter (DM)-baryon interactions, induced by the kinetic mixing of a new U(1) gauge boson and a photon, affect the evolution of the Sun and, in turn, the sound speed the profile obtained from helioseismology. Thanks to the explicit dependence on the exchanged momenta in the differential cross section (Rutherford-like scattering), we find that DM particles with a mass of ∼10 GeV, kinetic mixing parameter of the order of 10-9, and a mediator with a mass smaller than a few MeV improve the agreement between the best solar model and the helioseismic data without being excluded by direct detection experiments. In particular, the LUX detector will soon be able to either constrain or confirm our best-fit solar model in the presence of a dark sector with long-range interactions that reconcile helioseismology with thermal neutrino results
Dark Matter's secret liaisons: Phenomenology of a dark U(1) sector with bound states
Full text linkDark matter (DM) charged under a dark U(1) force appears in many extensions of the Standard Model, and has been invoked to explain anomalies in cosmic-ray data, as well as a self-interacting DM candidate. In this paper, we perform a comprehensive phenomenological analysis of such a model, assuming that the DM abundance arises from the thermal freeze-out of the dark interactions. We include, for the first time, bound-state effects both in the DM production and in the indirect detection signals, and quantify their importance for Fermi, Ams-02, and CMB experiments. We find that DM in the mass range 1 GeV to 100TeV, annihilating into dark photons of MeV to GeV mass, is in conict with observations. Instead, DM annihilation into heavier dark photons is viable. We point out that the late decays of multi-GeV dark photons can produce significant entropy and thus dilute the DM density. This can lower considerably the dark coupling needed to obtain the DM abundance, and in turn relax the existing constraints
Gamma ray tests of Minimal Dark Matter
Full text linkWe reconsider the model of Minimal Dark Matter (a fermionic, hypercharge-less quintuplet of the EW interactions) and compute its gamma ray signatures. We compare them with a number of gamma ray probes: the galactic halo diffuse measurements, the galactic center line searches and recent dwarf galaxies observations. We find that the original minimal model, whose mass is fixed at 9.4 TeV by the relic abundance requirement, is constrained by the line searches from the Galactic Center: it is ruled out if the Milky Way possesses a cuspy profile such as NFW but it is still allowed if it has a cored one. Observations of dwarf spheroidal galaxies are also relevant (in particular searches for lines), and ongoing astrophysical progresses on these systems have the potential to eventually rule out the model. We also explore a wider mass range, which applies to the case in which the relic abundance requirement is relaxed. Most of our results can be safely extended to the larger class of multi-TeV WIMP DM annihilating into massive gauge bosons
Faint Light from Dark Matter: Classifying and Constraining Dark Matter-Photon Effective Operators
Full text linkEven if Dark Matter (DM) is neutral under electromagnetism, it can still interact with the Standard Model (SM) via photon exchange from higher-dimensional operators. Here we classify the general effective operators coupling DM to photons, distinguishing between Dirac/Majorana fermion and complex/real scalar DM. We provide model-independent constraints on these operators from direct and indirect detection. We also constrain various DM-lepton operators, which induce DM-photon interactions via RG running or which typically arise in sensible UV-completions. This provides a simple way to quickly assess constraints on any DM model that interacts mainly via photon exchange or couples to SM leptons
Long-Range Forces in Direct Dark Matter Searches
Full text linkWe discuss the positive indications of a possible dark matter signal in direct detection experiments in terms of a mechanism of interaction between the dark matter particle and the nuclei occurring via the exchange of a light mediator, resulting in a long-range interaction. We analyze the annual modulation results observed by the DAMA and CoGeNT experiments and the observed excess of events of CRESST. In our analysis, we discuss the relevance of uncertainties related to the velocity distribution of galactic dark matter and to the channeling effect in NaI. We find that a long-range force is a viable mechanism, which can provide full agreement between the reconstructed dark matter properties from the various experimental data sets, especially for masses of the light mediator in the 10-30 MeV range and a light dark matter with a mass around 10 GeV. The relevant bounds on the light mediator mass and scattering cross section are then derived, should the annual modulation effects be due to this class of long-range forces
Annual modulations from secular variations: relaxing DAMA?
Full text linkThe DAMA collaboration reported an annually modulated rate with a phase compatible with a Dark Matter induced signal. We point out that a slowly varying rate can bias or even simulate an annual modulation if data are analyzed in terms of residuals computed by subtracting approximately yearly averages starting from a fixed date, rather than a background continuous in time. In the most extreme case, the amplitude and phase of the annual modulation reported by DAMA could be alternatively interpreted as a decennial growth of the rate. This possibility appears mildly disfavoured by a detailed study of the available data, but cannot be safely excluded. In general, a decreasing or increasing rate could partially reduce or enhance a true annual modulation, respectively. The issue could be clarified by looking at the full time-dependence of the DAMA total rate, not explicitly published so far
Looking for ultralight dark matter near supermassive black holes
Full text linkMeasurements of the dynamical environment of supermassive black holes (SMBHs) are becoming abundant and precise. We use such measurements to look for ultralight dark matter (ULDM), which is predicted to form dense cores ("solitons") in the centre of galactic halos. We search for the gravitational imprint of an ULDM soliton on stellar orbits near Sgr A∗ and by combining stellar velocity measurements with Event Horizon Telescope imaging of M87∗. Finding no positive evidence, we set limits on the soliton mass for different values of the ULDM particle mass m. The constraints we derive exclude the solitons predicted by a naive extrapolation of the soliton-halo relation, found in DM-only numerical simulations, for 2×10-20 eV≲ m≲8×10-19 eV (from Sgr A∗) and m≲4×10-22 eV (from M87∗). However, we present theoretical arguments suggesting that an extrapolation of the soliton-halo relation may not be adequate: in some regions of the parameter space, the dynamical effect of the SMBH could cause this extrapolation to over-predict the soliton mass by orders of magnitude
Prospects for annihilating dark matter in the inner galactic halo by the Cherenkov Telescope Array
Full text linkWe compute the sensitivity to dark matter annihilations for the forthcoming large Cherenkov Telescope Array (CTA) in several primary channels and over a range of dark matter masses from 50 GeV up to 80 TeV. For all channels, we include inverse Compton scattering of e± by dark matter annihilations on the ambient photon background, which yields substantial contributions to the overall γ-ray flux. We improve the analysis over previous work by: (i) implementing a spectral and morphological analysis of the γ-ray emission; (ii) taking into account the most up-to-date cosmic ray background obtained from a full CTA Monte Carlo simulation and a description of the diffuse astrophysical emission; and (iii) including the systematic uncertainties in the rich observational CTA data sets. We find that our spectral and morphological analysis improves the CTA sensitivity by roughly a factor 2. For the hadronic channels, CTA will be able to probe thermal dark matter candidates over a broad range of masses if the systematic uncertainties in the data sets will be controlled better than the percent level. For the leptonic modes, the CTA sensitivity will be well below the thermal value of the annihilation cross-section. In this case, even with larger systematics, thermal dark matter candidates up to masses of a few TeV will be easily studied
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