Leszek Roszkowski

Axinos as Cold Dark Matter

The connection of Dark Matter (DM) to our particle physics model is still one of the open cosmological questions. In these proceedings I will argue that axinos can be successful Cold Dark Matter candidates in models with Supersymmetry and the Peccei‐Quinn solution of the strong CP problem. If they are the Lightest Supersymmetric Particle (LSP), they can be produced in the right abundance by thermal scatterings and out of equilibrium decays of the Next‐to‐Lightest Supersymmetric Particles (NLSPs). Moreover if the NLSPs are charged, their decay could help us understand which is the LSP, e.g. between axino and gravitino.

Exact Cross Sections for the Neutralino-Slepton Coannihilation

Coannihilation processes provide an important additional mechanism for reducing the density of stable relics in the Universe. In the case of the stable lightest neutralino of the MSSM, and in particular the Constrained MSSM (CMSSM), the coannihilation with sleptons plays a major role in opening up otherwise cosmologically excluded ranges of supersymmetric parameters. In this paper, we derive a full set of exact, analytic expressions for the coannihilation of the lightest neutralino with the sleptons into all two-body tree-level final states in the framework of minimal supersymmetry. We make no simplifying assumptions about the neutralino nor about sfermion masses and mixings other than the absence of explicit CP-violating terms and inter-family mixings. The expressions should be particularly useful in computing the neutralino WIMP relic abundance without the approximation of partial wave expansion. We illustrate the effect of our analytic results with numerical examples and demonstrate a sizeable difference with approximate expressions available in the literature.

A New model independent method for extracting spin dependent (cross-section) limits from dark matter searches

Abstract A new method is proposed for extracting limits on spin-dependent WIMP-nucleon interaction cross sections from direct detection dark matter experiments. The new method has the advantage that the limits on individual WIMP-proton and WIMP-neutron cross sections for a given WIMP mass can be combined in a simple way to give a model-independent limit on the properties of WIMPs scattering from both protons and neutrons in the target nucleus. Extension of the technique to the case of a target material consisting of several different species of nuclei is discussed.

Upper and Lower Limits on Neutralino WIMP Mass and Spin–Independent Scattering Cross Section, and Impact of New (g−2)μ Measurement

We derive the allowed ranges of the spin-independent interaction cross section ?SIp for the elastic scattering of neutralinos on proton for wide ranges of parameters of the general Minimal Supersymmetric Standard Model. We investigate the effects of the lower limits on Higgs and superpartner masses from colliders, as well as the impact of constraints from b? s? and the new measurement of (g?2)? on the upper and lower limits on ?SIp. We further explore the impact of the neutralino relic density, including coannihilation, and of theoretical assumptions about the largest allowed values of the supersymmetric parameters. For 0

Effects of Squark Processes on the Axino CDM Abundance

>?>0, requiring the latter to lie below 1?TeV leads to ?SIp10?11?pb at m? ~ 100?GeV and ?SIp10?8?pb at m? ~ 1?TeV. When the supersymmetric parameters are allowed above 1?TeV, for 440?GeVm?1020?GeV we derive a parameter-independent lower limit of ?SIp2 ? 10?12?pb. (No similar lower limits can be set for ? ?>0. The largest allowed values of ?SIp have already become accessible to recent experimental searches.

Exact Cross Sections for the Neutralino WIMP Pair-Annihilation

We investigate the role of an effective dimension-4 axino-quark-squark coupling in the thermal processes producing stable cold axino relics in the early Universe. We find that, while the induced squark and quark scattering processes are always negligible, squark decays become important in the case of low reheat temperature and large gluino mass. The effect can tighten the bounds on the scenario from the requirement that cold dark matter axinos do not overclose the Universe.

Constraints from inflation and reheating on superpartner masses

We derive a full set of exact, analytic expressions for the annihilation of the lightest neutralino pairs into all two-body tree-level final states in the framework of minimal supersymmetry. We make no simplifying assumptions about the neutralino nor about sfermion masses and mixings other than the absence of explicit CP-violating terms. The expressions should be particularly useful in computing the neutralino WIMP relic abundance without the usual approximation of partial wave expansion.

WIMP VELOCITY IMPACT ON DIRECT DARK MATTER SEARCHES

Abstract Flat directions in the Minimal Supersymmetric Standard Model (MSSM) can become unstable due to radiative corrections, and the global minimum of the (zero temperature) potential can lie at large values of the squark and/or slepton fields. Here we show that, in inflationary models of early cosmology, the universe is very likely to be in the domain of attraction of this global minimum at the end of inflation. While the minimum at the origin of field space is global at sufficiently high temperatures, depending on details of the model, the universe may be trapped in the non-zero minimum until it becomes the global minimum at low temperatures. Parameter values leading to this scenario are therefore ruled out.

Observational constraints on an inflation model with a running mass

Abstract We examine the effect of some uncertainties in the input astrophysical parameters on direct detection searches for WIMPs in the Galactic halo. We concentrate on the possible WIMP annual modulation signal recently reported by the DAMA Collaboration. We find that allowing for a reasonable uncertainty in a WIMP Maxwellian velocity distribution leads to significantly relaxed constraints on the WIMP mass as compared to the original DAMA analysis.

Supersymmetry and dark matter

We explore a model of inflation where the inflaton mass-squared is generated at a high scale by gravity-mediated soft supersymmetry breaking, and runs at lower scales to the small value required for slow-roll inflation. The running is supposed to come from the coupling of the inflaton to a non-Abelian gauge field. In contrast with earlier work, we do not constrain the magnitude of the supersymmetry breaking scale, and we find that the model might work even if squark and slepton masses come from gauge-mediated supersymmetry breaking. With the inflaton and gaugino masses in the expected range, and