Reanalysis of nuclear spin matrix elements for dark matter spin-dependent scattering

We show how to include in the existing calculations for nuclei other than $^{129}$Xe, $^{131}$Xe, the corrections to the isovector coupling arising in chiral effective field theory recently found in Ref. \cite{Menendez1}. The dominant, momentum independent, 2-body currents effect can be taken into account by formally redefining the static spin matrix elements $< \mathbf{S}_{p,n} >$. By further using the normalized form factor at $q\neq 0$ built with the 1-body level structure functions, we show that the WIMP-nucleus cross section and the upper limits on the WIMP-nucleon cross sections coincide with the ones derived using the exact functions at the 2-body level. We explicitly show it in the case of XENON100 limits on the WIMP-neutron cross section and we recalculate the limits on the WIMP-proton spin dependent cross section set by COUPP. We also give practical formulas to obtain $< \mathbf{S}_{p,n} >$ given the structure functions in the various formalisms/notations existing in literature. We argue that the standard treatment of the spin-dependent cross section in terms of three independent isospin functions, $S_{00}(q)$, $S_{11}(q)$, $S_{01}(q)$, is redundant in the sense that the interference function $S_{01}(q)$ is the double product $|S_{01}(q)|=2\sqrt{S_{00}(q)}\sqrt{S_{11}(q)}$ even when including the new effective field theory corrections.Comment: 8 pages, 6 figures: extended and revised, accepted in Physical Review

Probability distribution for the relative velocity of colliding particles in a relativistic classical gas

We find the probability density function $\mathcal{P}(V_{\texttt{r}})$ of the relativistic relative velocity for two colliding particles in a non-degenerate relativistic gas. The distribution reduces to Maxwell distribution for the relative velocity in the non-relativistic limit. We find an exact formula for the mean value $\langle V_{\texttt{r}}\rangle$. The mean velocity tends to the Maxwell's value in the non-relativistic limit and to the velocity of light in the ultra-relativistic limit. At a given temperature $T$, when at least for one of the two particles the ratio of the rest energy over the thermal energy $m c^2/k_B T$ is smaller than 40 the Maxwell distribution is inadequate.Comment: 5 pages, 2 figures. V2: text revised. Part of this material is published in Phys. Rev. D 89, 103533 (2014) in a merged version with arXiv:1311.450

Higgs sector of the MSSM: lepton flavor violation at colliders and neutralino dark matter

We examine the prospects for the detection of Higgs mediated lepton flavor violation at LHC and at a photon collider in the minimal supersymmetric standard model with large lepton flavor violating mass insertions in the $\mu-\tau$ sector constraining the parameter space with several experimental bounds. We find rates probably too small to be observed at future experiments if models have to accommodate for a neutralino relic density as measured by WMAP and explain the $(g-2)_{\mu}$ anomaly: better prospects are found if these two constraints are applied only as upper bounds. The spin-independent neutralino-nucleon cross section in the studied constrained parameter space is just below the present CDMS limit while gamma rates from neutralino annihilation in the halo are strongly suppressed.Comment: 6 pages, 2 figures, Prepared for the proceedings of the workshop: "LC09: $e^+ e^-$ Physics at the TeV Scale and the Dark Matter Connection", 21-24 September 2009, Perugia, Ital

Testing SUSY models of lepton flavor violation at a photon collider

The loop level lepton flavor violating signals $\gamma \gamma \to \ell \ell' (\ell=e,\mu,\tau, \ell \neq \ell^\prime)$ are studied in a scenario of low-energy, R-parity conserving, supersymmetric seesaw mechanism within the context of a high energy photon collider. Lepton flavor violation is due to off diagonal elements in the left s-lepton mass matrix induced by renormalization group equations. The average slepton masses ${\widetilde{m}}$ and the off diagonal matrix elements $\Delta m$ are treated as model independent free phenomenological parameters in order to discover regions in the parameter space where the signal cross section may be observable. At the energies of the $\gamma \gamma$ option of the future high-energy linear collider the signal has a potentially large standard model background, and therefore particular attention is paid to the study of kinematical cuts in order to reduce the latter at an acceptable level. We find, for the ($e\tau$) channel, non-negligible fractions of the parameter space ($\delta_{LL}=\Delta m^2/\widetilde{m}^2 \gtrsim 10^{-1}$) where the statistical significance ($SS$) is $SS \gtrsim 3$.Comment: 26 pages, 12 figures, Revtex

Impact of internal bremsstrahlung on the detection of gamma-rays from neutralinos

We present a detailed study of the effect of internal bremsstrahlung photons in the context of the minimal supersymmetric standard models and their impact on gamma-ray dark matter annihilation searches. We find that although this effect has to be included for the correct evaluation of fluxes of high energy photons from neutralino annihilation, its contribution is relevant only in models and at energies where the lines contribution is dominant over the secondary photons. Therefore, we find that the most optimistic supersymmetric scenarios for dark matter detection do not change significantly when including the internal bremsstrahlung. As an example, we review the gamma-ray dark matter detection prospects of the Draco dwarf spheroidal galaxy for the MAGIC stereoscopic system and the CTA project. Though the flux of high energy photons is enhanced by an order of magnitude in some regions of the parameter space, the expected fluxes are still much below the sensitivity of the instruments.Comment: 5 pages, twocolumn format, 3 figures:3 references added, accepted as Brief Report in PR

Supersymmetry Searches in GUT Models with Non-Universal Scalar Masses

We study SO(10), SU(5) and flipped SU(5) GUT models with non-universal soft supersymmetry-breaking scalar masses, exploring how they are constrained by LHC supersymmetry searches and cold dark matter experiments, and how they can be probed and distinguished in future experiments. We find characteristic differences between the various GUT scenarios, particularly in the coannihilation region, which is very sensitive to changes of parameters. For example, the flipped SU(5) GUT predict the possibility of $\tilde{t}_1-\chi$ coannihilation, which is absent in the regions of the SO(10) and SU(5) GUT parameter spaces that we study. We use the relic density predictions in different models to determine upper bounds for the neutralino masses, and we find large differences between different GUT models in the sparticle spectra for the same LSP mass, leading to direct connections of distinctive possible experimental measurements with the structure of the GUT group. We find that future LHC searches for generic missing $E_T$, charginos and stops will be able to constrain the different GUT models in complementary ways, as will the Xenon 1 ton and Darwin dark matter scattering experiments and future FERMI or CTA $\gamma$-ray searches.Comment: 21 pages, 10 Figures. V3: some comments and 1 reference added, published version. JCAP03(2016)04

A scheme for the extraction of WIMP-nucleon scattering cross sections from total event rates

We propose a scheme that allows to analytically determine the three elementary cross sections and connect the solutions to the relative sign between the proton and the neutron spin scattering amplitudes once the measurements of total event rate from three appropriate targets become available. In this way it is thus possible to extract the maximum information on the supersymmetric parameter space obtainable from direct detection experiments, in the case that the dark matter particle is the lightest neutralino. Our scheme is based on suitably normalized form of the isospin momentum dependent structure functions entering in the spin-dependent elastic neutralino-nucleus cross section. We compare these functions with the commonly used ones and discuss their advantages: in particular, these allow in the spin-dependent cross section to factorize the particle physics degrees of freedom from the momentum transfer dependent nuclear structure functions as it happens in the spin-independent cross section with the nuclear form factor.Comment: 8 pages, 4 figures. Title, text and references revised and expanded. Added an Appendix explaining the advantages of the normalized spin structure functions. Accepted in PR

The SUSY seesaw model and lepton-flavor violation at a future electron-positron linear collider

We study lepton-flavor violating slepton production and decay at a future e^+e^- linear collider in context with the seesaw mechanism in mSUGRA post-LEP benchmark scenarios. The present knowledge in the neutrino sector as well as improved future measurements are taken into account. We calculate the signal cross-sections \sigma(e^{+/-}e^- -> l_{\beta}^{+/-} l_{\alpha}^- \tilde{\chi}_b^0 \tilde{\chi}_a^0); l_{\delta}=e, \mu, \tau; \alpha =|= \beta and estimate the main background processes. Furthermore, we investigate the correlations of these signals with the corresponding lepton-flavor violating rare decays l_{\alpha} -> l_{\beta} \gamma. It is shown that these correlations are relatively weakly affected by uncertainties in the neutrino data, but very sensitive to the model parameters. Hence, they are particularly suited for probing the origin of lepton-flavor violation.Comment: 31 pages, 10 figures, version published in Phys. Rev.