A systematic halo-independent analysis of direct detection data within the framework of Inelastic Dark Matter

We present a systematic halo-independent analysis of available Weakly Interacting Massive Particles (WIMP) direct detection data within the framework of Inelastic Dark Matter (IDM). We show that, when the smallest number of assumptions is made on the WIMP velocity distribution in the halo of our Galaxy, it is possible to find values of the WIMP mass and the IDM mass splitting for which compatibility between present constraints and any of the three experiments claiming to see a WIMP excess among DAMA, CDMS-Si and CRESST can be achieved.Comment: 33 pages, 15 figures. Discussion extended with one additional figure. References added. Updated to published versio

On the sbottom resonance in dark matter scattering

A resonance in the neutralino-nucleus elastic scattering cross section is usually purported when the neutralino-sbottom mass difference m_sbottom-m_chi is equal to the bottom quark mass m_b ~ 4 GeV. Such a scenario has been discussed as a viable model for light (~ 10 GeV) neutralino dark matter as explanation of possible DAMA and CoGeNT direct detection signals. Here we give physical and analytical arguments showing that the sbottom resonance may actually not be there. In particular, we show analytically that the one-loop gluon-neutralino scattering amplitude has no pole at m_sbottom=m_chi+m_b, while by analytic continuation to the regime m_sbottom<m_chi, it develops a pole at m_sbottom=m_chi-m_b. In the limit of vanishing gluon momenta, this pole corresponds to the only cut of the neutralino self-energy diagram with a quark and a squark running in the loop, when the decay process chi->squark+quark becomes kinematically allowed. The pole can be interpreted as the formation of a sbottom-antibottom-qqq or antisbottom-bottom qqq resonant state (where qqq are the nucleon valence quarks), which is kinematically not accessible if the neutralino is the LSP. Our analysis shows that the common practice of estimating the neutralino-nucleon cross section by introducing an ad-hoc pole at m_sbottom=m_chi+m_b into the effective four-fermion interaction (including higher-twist effects) should be discouraged, since it corresponds to adding a spurious pole to the scattering process at the center-of-mass energy sqrt(s) m_chi m_sbottom-m_b. Our considerations can be extended from the specific case of supersymmetry to other cases in which the dark matter particle scatters off nucleons through the exchange of a b-flavored state almost degenerate to its mass, such as in theories with extra dimensions and in other mass-degenerate dark matter scenarios recently discussed in the literature.Comment: 31 pages, 14 figure

Lightest Higgs Boson and Relic Neutralino in the MSSM with CP Violation

We discuss the lower bound to the lightest Higgs boson H_1 in the minimal supersymmetric extension of the standard model (MSSM) with explicit CP violation, and the phenomenology of the lightest relic neutralino in the same scenario. In particular, adopting the CPX benchmark scenario, we find that the combination of experimental constraints coming from LEP, Thallium Electric Dipole Moment (EDM) measurements, quorkonium decays, and B_s -> mu mu decay favours a region of the parameter space where the mass of H_1 is in the range 7 GeV < M_{H_1} < 10 GeV, while 3 < tan(beta) < 5. Assuming a departure from the usual GUT relation among gaugino masses (|M_1| << |M_2|), we find that through resonant annihilation to H_1 a neutralino as light as 2.9 GeV can be a viable dark matter candidate in this scenario. We call this the CPX light neutralino scenario, and discuss its phenomenology showing that indirect Dark Matter searches are compatible with the present experimental constraints, as long as m_\chi M_{H_1}/2 which is allowed by cosmology is excluded by antiproton fluxes.Comment: 16 pages, 6 figure

Effective scalar four-fermion interaction for Ge-phobic exothermic dark matter and the CDMS-II Silicon excess

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 $\chi$ and the lowest-mass one $\chi^{\prime}$ 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 $\chi$ to $\chi^{\prime}$. 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.Comment: 19 pages, 7 figures. References added, updated to published versio

Probing DAMA/LIBRA in the full parameter space of WIMP effective models of inelastic scattering

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 $m_{\chi}\simeq$ 10 GeV and mass splitting $\delta\gtrsim$ 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 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.Comment: 15 pages, 11 figures, 5 tables. Updated to published versio

Generalized spin-dependent WIMP-nucleus interactions and the DAMA modulation effect

Guided by non-relativistic Effective Field Theory (EFT) we classify the most general spin-dependent interactions between a fermionic Weakly Interacting Massive Particle (WIMP) and nuclei, and within this class of models we discuss the viability of an interpretation of the DAMA modulation result in terms of a signal from WIMP elastic scatterings using a halo-independent approach. We find that, although several relativistic EFT's can lead to a spin-dependent cross section, in some cases with an explicit, non-negligible dependence on the WIMP incoming velocity, three main scenarios can be singled out in the non-relativistic limit which approximately encompass them all, and that only differ by their dependence on the transferred momentum. For two of them compatibility between DAMA and other constraints is possible for a WIMP mass below 30 GeV, but only for a WIMP velocity distribution in the halo of our Galaxy which departs from a Maxwellian. This is achieved by combining a suppression of the WIMP effective coupling to neutrons (to evade constraints from xenon and germanium detectors) to an explicit quadratic or quartic dependence of the cross section on the transferred momentum (that leads to a relative enhancement of the expected rate off sodium in DAMA compared to that off fluorine in droplet detectors and bubble chambers). For larger WIMP masses the same scenarios are excluded by scatterings off iodine in COUPP.Comment: 24 pages, 4 figure

New approaches in the analysis of Dark Matter direct detection data: scratching below the surface of the most general WIMP parameter space

We show that compatibility between the DAMA modulation result (as well as less statistically significant excesses such as the CDMS Silicon effect and the excess claimed by CRESST) with constraints from other experiments can be achieved by extending the analysis of direct detection data beyond the standard elastic scattering of a WIMP off nuclei with a spin--dependent or a spin--independent cross section and with a velocity distribution as predicted by the Isothermal Sphere model. To do so we discuss several new approaches for the analysis of Dark Matter direct detection data, with the goal to remove or reduce its dependence on specific theoretical assumptions, and to extend its scope: the factorization approach of astrophysics uncertainties, the classification and study of WIMP-nucleon interactions within non--relativistic field theory, inelastic scattering and isovector-coupling cancellations including subdominant two-nucleon NLO effects. Typically, combining two or more of these ingredients can lead to conclusions which are very different to what usually claimed in the literature. This shows that we are only starting now to scratch the surface of the most general WIMP direct detection parameter space.Comment: 6 pages, 3 figures, to appear in the proceedings of the 14th Marcel Grossmann meeting, Roma, July 201

Non-perturbative Effect and PAMELA Limit on Electro-Weak Dark Matter

We discuss the non-perturbative effects on the annihilation cross section of an Electro-Weak Dark Matter (EWDM) particle belonging to an electroweak multiplet when the splittings between the masses of the DM component and the other charged or neutral component(s) of the multiplet are treated as free parameters. Our analysis shows that EWDM exhibits not only the usual Sommerfeld enhancement with resonance peaks but also dips where the cross section is suppressed. Moreover, we have shown that the non-perturbative effects become important even when the EWDM mass is below the TeV scale, provided that some of the mass splitting are reduced to the order of a few MeV. This extends the possibility of observing sizeable non-perturbative effects in the dark matter annihilation to values of the dark matter mass significantly smaller than previously considered, since only electroweak--induced mass splittings larger than 100 MeV have been discussed in the literature so far. We have then used the available experimental data on the cosmic antiproton flux to constrain the EWDM parameter space. In our calculation of the expected signal we have included the effect of the convolution of the cross section with the velocity distribution of the dark matter particles in the Galaxy, showing that it can alter the non--perturbative effects significantly. In the case of EWDM with non-zero hypercharge, we have shown that the mass splitting in the Dirac dark matter fermion can be chosen so that the inelastic cross section of the EWDM off nuclei is allowed by present direct detection constraints and at the same time is within the reach of future experiments.Comment: 19 pages, 12 figure

Non-standard scaling laws of WIMP-nucleus interactions in WIMP direct detection

Guided by the non-relativistic effective field theory of interactions between Weakly Interacting Massive Particles (WIMPs) of spin 1/2 and nuclei we study direct detection exclusion plots for an example of non-standard spin-dependent interaction and compare it to the standard one. We analyze an extensive list of 15 existing experiments including the effects of momentum dependence and isospin violation. In our analysis, we fixed the dark matter velocity distribution to a Maxwellian.Comment: Proceeding for ICHEP 2018, International Conference on High Energy Physics, 4-11 July 2018, Seoul, Kore

On the sensitivity of present direct detection experiments to WIMP-quark and WIMP-gluon effective interactions: a systematic assessment and new model-independent approaches

Assuming for Weakly Interacting Massive Particles (WIMPs) a Maxwellian velocity distribution in the Galaxy we provide an assessment of the sensitivity of existing Dark Matter (DM) direct detection (DD) experiments to operators up to dimension 7 of the relativistic effective field theory describing dark matter interactions with quarks and gluons . In particular we focus on a systematic approach, including an extensive set of experiments and large number of couplings, both exceeding for completeness similar analyses in the literature. The relativistic effective theory requires to fix one coupling for each quark flavor, so in principle for each different combination the bounds should be recalculated starting from direct detection experimental data. To address this problem we propose an approximate model-independent procedure that allows to directly calculate the bounds for any combination of couplings in terms of model-independent limits on the Wilson coefficients of the non-relativistic theory expressed in terms of the WIMP mass and of the neutron-to-proton coupling ratio $c^n/c^p$. We test the result of the approximate procedure against that of a full calculation, and discuss its possible pitfalls and limitations. We also provide a simple interpolating interface in Python that allows to apply our method quantitatively.Comment: 23 pages, 11 figures, 2 tables. Updated to published version. The companion code can be downloaded from https://github.com/NRDD-constraints/NRD