Higgs funnel region of SUSY dark matter for small tan⁡β\tan\beta and renormalization group effects on pseudoscalar Higgs boson with scalar mass non-universality

A non-universal scalar mass supergravity type of model is explored where the first two generation of scalars and the third generation of sleptons may be very massive. Lighter or vanishing third generation of squarks as well as Higgs scalars at the unification scale cause the radiative electroweak symmetry breaking constraint to be less prohibitive. Thus, both FCNC/CP-violation problems as well as the naturalness problem are within control. We identify a large slepton mass effect in the RGE of $m_{H_D}^2$ (for the down type of Higgs) that may turn the later negative at the electroweak scale even for a small $\tan\beta$. A hyperbolic branch/focus point like effect is found for $m_A^2$ that may result in very light Higgs spectra. The lightest stable particle is dominantly a bino that pair annihilates via Higgs exchange, giving rise to a WMAP satisfied relic density region for all $\tan\beta$. Detection prospects of such LSPs in the upcoming dark matter experiments both of direct and indirect types (photon flux) are interesting. The Higgs bosons and the third generation of squarks are light in this scenario and these may be easily probed besides charginos and neutralinos in the early runs of LHC.Comment: 36 pages and 7 Postscript files. Minor changes in the text. Version accepted for publication in Phys. Rev.

Potentially Large One-loop Corrections to WIMP Annihilation

We compute one-loop corrections to the annihilation of non--relativistic particles $\chi$ due to the exchange of a (gauge or Higgs) boson $\phi$ with mass $\mu$ in the initial state. In the limit $m_\chi \gg \mu$ this leads to the "Sommerfeld enhancement" of the annihilation cross section. However, here we are interested in the case \mu \lsim m_\chi, where the one--loop corrections are well--behaved, but can still be sizable. We find simple and accurate expressions for annihilation from both $S-$ and $P-$wave initial states; they differ from each other if $\mu \neq 0$. In order to apply our results to the calculation of the relic density of Weakly Interacting Massive Particles (WIMPs), we describe how to compute the thermal average of the corrected cross sections. We apply this formalism to scalar and Dirac fermion singlet WIMPs, and show that the corrections are always very small in the former case, but can be very large in the latter. Moreover, in the context of the Minimal Supersymmetric Standard Model, these corrections can decrease the relic density of neutralinos by more than 1%, if the lightest neutralino is a strongly mixed state.Comment: 25 pages, 8 figures. Added an appendix showing that the approximation works well in a scalar toy model. To be published in PRD

Virtual Photon Strucutre Functions and the Parton Content of the Electron

We point out that in processes involving the parton content of the photon the usual effective photon approximation should be modified. The reason is that the parton content of virtual photons is logarithmically suppressed compared to real photons. We describe this suppression using several simple, physically motivated ans\"atze. Although the parton content of the electron in general no longer factorizes into an electron flux function and a photon structure function, it can still be expressed as a single integral. Numerical examples are given for the \eplem\ collider TRISTAN as well as the $ep$ collider HERA.Comment: 16 pages and 3 figures (available from DREES@WSICPHEN as topdraw or PS files); LaTeX with equation.sty; MAD/PH/819, BU 94-0

Loop induced Higgs and Z boson couplings to Neutralinos and implications for collider and Dark Matter searches

We calculate the one-loop induced couplings of two gaugino-like neutralinos to the $Z$ and Higgs bosons in the Minimal Supersymmetric Standard Model. These couplings, which vanish at the tree level, can be generated through loops involving fermions and sfermions. We show that, while the neutralino contribution to the invisible $Z$ boson decay width remains small, the loop induced couplings to the lightest Higgs boson might be sufficiently large to yield a rate of invisible decays of this Higgs boson that should be detectable at future $e^+e^-$ colliders. We also study the implications of these couplings for direct searches of Dark Matter and show that they can modify appreciably the neutralino-nucleon elastic cross section for some parameter range.Comment: LaTeX with 6 (e)ps and 2 axodraw figures, 25 pages in total; axodraw.sty is included v.2: Added one figure and some discussions; version to appear in PR

Neutralino Dark Matter Elastic Scattering in a Flat and Accelerating Universe

In SUGRA inspired supersymmetric models with universal boundary conditions for the soft masses, the scalar cross section $\sigma_{scalar}$ for the elastic neutralino--nucleon scattering is in general several orders of magnitude below the sensitivity of current experiments. For large $\tan \beta$ and low $M_{1/2}, m_0$ values, the theoretically predicted $\sigma_{scalar}$ can approach the sensitivity of these experiments ($\approx 10^{-6} pb$) being at the same time in agreement with recent cosmological data, which impose severe restrictions on the CDM relic density, and with accelerator experiments which put lower bounds on sparticle and Higgs boson masses. Further improvement of the sensitivity of DAMA and CDMS experiments will probe the large $\tan \beta$ region of the parameter space in the vicinity of the boundaries of the parameter space allowed by chargino and Higgs searches.Comment: 15 pages, 9 figures. A note added; version to appear in MPL

SUSY Dark Matter in the Universe- Theoretical Direct Detection Rates

Exotic dark matter together with the vacuum energy or cosmological constant seem to dominate in the Universe. An even higher density of such matter seems to be gravitationally trapped in the Galaxy. Thus its direct detection is central to particle physics and cosmology. Current supersymmetric models provide a natural dark matter candidate which is the lightest supersymmetric particle (LSP). Such models combined with fairly well understood physics like the quark substructure of the nucleon and the nuclear structure (form factor and/or spin response function), permit the evaluation of the event rate for LSP-nucleus elastic scattering. The thus obtained event rates are, however, very low or even undetectable. So it is imperative to exploit the modulation effect, i.e. the dependence of the event rate on the earth's annual motion. Also it is useful to consider the directional rate, i.e its dependence on the direction of the recoiling nucleus. In this paper we study such a modulation effect both in non directional and directional experiments. We calculate both the differential and the total rates using both isothermal, symmetric as well as only axially asymmetric, and non isothermal, due to caustic rings, velocity distributions. We find that in the symmetric case the modulation amplitude is small. The same is true for the case of caustic rings. The inclusion of asymmetry, with a realistic enhanced velocity dispersion in the galactocentric direction, yields an enhanced modulation effect, especially in directional experiments.Comment: 17 LATEX pages, 1 table and 6 ps figures include

Scrutinizing LSP Dark Matter at the LHC

We show that LHC experiments might well be able to determine all the parameters required for a prediction of the present density of thermal LSP relics from the Big Bang era. If the LSP is an almost pure bino we usually only need to determine its mass and the mass of the SU(2) singlet sleptons. This information can be obtained by reconstructing the cascade $\tilde{q}_L \to \tilde{\chi}_2^0 q \to \tilde{\ell}_R \ell q \to \tilde{\chi}_1^0 \ell^+ \ell^- q$. The only requirement is that $m_{\tilde{\ell}_R} < m_{\tilde{\chi}_2^0}$, which is true for most of the cosmologically interesting parameter space. If the LSP has a significant higgsino component, its predicted thermal relic density is smaller than for an equal--mass bino. We show that in this case squark decays also produce significant numbers of $\tilde{\chi}_4^0$ and $\tilde{\chi}_2^\pm$. Reconstructing the corresponding decay cascades then allows to determine the higgsino component of the LSP

Effects of Residue Background Events in Direct Dark Matter Detection Experiments on the Determination of the WIMP Mass

In the earlier work on the development of a model-independent data analysis method for determining the mass of Weakly Interacting Massive Particles (WIMPs) by using measured recoil energies from direct Dark Matter detection experiments directly, it was assumed that the analyzed data sets are background-free, i.e., all events are WIMP signals. In this article, as a more realistic study, we take into account a fraction of possible residue background events, which pass all discrimination criteria and then mix with other real WIMP-induced events in our data sets. Our simulations show that, for the determination of the WIMP mass, the maximal acceptable fraction of residue background events in the analyzed data sets of O(50) total events is ~20%, for background windows of the entire experimental possible energy ranges, or in low energy ranges; while, for background windows in relatively higher energy ranges, this maximal acceptable fraction of residue background events can not be larger than ~10%. For a WIMP mass of 100 GeV with 20% background events in the windows of the entire experimental possible energy ranges, the reconstructed WIMP mass and the 1-sigma statistical uncertainty are ~97 GeV^{+61%}_{-35%} (~94 GeV^{+55%}_{-33%} for background-free data sets).Comment: 27 pages, 22 eps figures; v2: revised version for publication, references added and update

Neutralino-neutralino annihilation to gammaZ in MSSM

The 1-loop computation of the processes \tchi_i \tchi_j \to \gamma Z has been performed at an arbitrary c.m. energy for any pair of MSSM neutralinos. As an application suitable for Dark Matter (DM) searches, the neutralino-neutralino annihilation is studied at the limiting case of vanishing relative velocity, describing the present DM distribution in the galactic halo; and at a relative velocity of about 0.5, determining the neutralino relic density contributions. The most useful situation is obviously for $i=j=1$, but the case of non-identical neutralinos may also be useful in some corners of the parameter space. Our results are contained in the FORTRAN code PLATONdmgZ, applying to any set of real MSSM parameters. Numerical results are also presented for a sample of 6 MSSM models, describing the various possible neutralino properties. A comparison with other existing works is also made.Comment: 14 pages, 7 figures, Version to appear in Physical Review