Dark Matter Spin Research Articles

PAMELA and dark matter

Assuming that the positron excess in PAMELA satellite data is a consequence of annihilations of cold dark matter, we consider from a model-independent perspective if the data show a preference for the spin of dark matter, and find that they do not. We then perform a general analysis of annihilations into two-body states to determine what weighted combination of channels best describes the data.

QCD radiative correction to pair annihilation of spin-1 bosonic dark matter

The next-to-leading order QCD corrections are calculated for the pair annihilation of spin-1 dark matter (DM) by dimensionally regularizing both ultraviolet and infrared singularities in the nonrelativistic (v<<1) limit. The complete O({alpha}{sub s}) correction is about 8% due to the massless gluon contribution. An extra 5% will be added if there is a new interaction from a massive gluon of approximately the same mass as the DM particle. The next-to-leading order QCD correction could result in a sizable shift to the DM mass constrained by relic density measurements.

Shape, Spin, and Baryon Fraction of Clusters in the MareNostrum Universe

The MareNostrum Universe is one of the largest cosmological smoothed particle hydrodynamics simulations done so far. It consists of 10243 dark and 10243 gas particles in a box of 500 h-1 Mpc on a side. Here we study the shapes and spins of the dark matter and gas components of the 10,000 most massive objects extracted from the simulation as well as the gas fraction in those objects. We find that the shapes of objects tend to be prolate both in the dark matter and gas. There is a clear dependence of shape on halo mass, the more massive ones being less spherical than the less massive objects. The gas distribution is nevertheless much more spherical than the dark matter, although the triaxiality parameters of gas and dark matter differ only by a few percent, and it increases with cluster mass. The spin parameters of gas and dark matter can be well fitted by a lognormal distribution function. On average, the spin of gas is 1.4 times larger than the spin of dark matter. We find a similar behavior for the spins at higher redshifts, with a slight decrease of the spin ratios to 1.16 at z = 1. The cosmic normalized baryon fraction in the entire cluster sample ranges from Yb = 0.94 at z = 1 to Yb = 0.92 at z = 0. At both redshifts we find a slight, but statistically significant, decrease of Yb with cluster mass.

Dark matter andBs→μ+μ−with minimal SO10soft SUSY breaking II

We update and extend to larger masses our previous analysis of the MSSM with minimal $SO_{10}$ [MSO$_{10}$SM] soft SUSY breaking boundary conditions. We find a well--defined, narrow region of parameter space which provides the observed relic density of dark matter, in a domain selected to fit precision electroweak data, including top, bottom and tau masses. The model is highly constrained which allows us to make several predictions. We find the light Higgs mass $m_h \leq 121 \pm 3$ GeV and also upper bounds on the mass of the gluino $\mgluino\lsim3.1$ TeV and lightest neutralino $\mchi\lsim450$ GeV. As the CP odd Higgs mass $m_A$ increases, the region of parameter space consistent with WMAP data is forced to larger values of $M_{1/2}$ and smaller values of $m_h$. Hence, we find an upper bound $m_A \lsim 1.3$ TeV. This in turn leads to lower bounds on ${\rm BR}(B_s\to \mu^+ \mu^-) > 10^{-8}$ (assuming minimal flavor violation) and on the dark matter spin independent detection cross section $\sigsip > 10^{-9}$ pb. Finally, we extend our previous analysis to include WIMP signals in indirect detection and find prospects for WIMP detection generally much less promising than in direct WIMP searches.

Hydrodynamics and correlation functions in ordered systems: Nematic liquid crystals: Dieter Forster. The James Franck Institute and The Department of Physics, The University of Chicago, Chicago, Illinois 60637

We consider scenarios in which the annihilation of self-conjugate spin-1 dark matter to a Standard Model fermion–antifermion final state is chirality suppressed, but where this suppression can be lifted by the emission of an additional photon via internal bremsstrahlung. We find that this scenario can only arise if the initial dark matter state is polarized, which can occur in the context of self-interacting dark matter. In particular, this is possible if the dark matter pair forms a bound state that decays to its ground state before the constituents annihilate. We show that the shape of the resulting photon spectrum is the same as for self-conjugate spin-0 and spin-1/2 dark matter, but the normalization is less heavily suppressed in the limit of heavy mediators.