17633401
Light Higgses at the Tevatron and at the LHC and Observable Dark Matter in SUGRA and D Branes
Abstract Sparticle landscapes in mSUGRA, in SUGRA models with nonuniversalities (NUSUGRA), and in D-brane models are analyzed. The analysis exhibits the existence of Higgs Mass Patterns (HPs) (for μ > 0 ) where the CP odd Higgs could be the next heavier particle beyond the LSP and sometimes even lighter than the LSP. It is shown that the Higgs production cross sections from the HPs are typically the largest enhancing the prospects for their detection at the LHC. Indeed it is seen that the recent Higgs production limits from CDF/DO are beginning to put constraints on the HPs. It is also seen that the B s → μ + μ − limits constrain the HPs more stringently. Predictions of the Higgs production cross sections for these patterns at the LHC are made. We compute the neutralino–proton cross sections σ ( χ ˜ 1 0 p ) for dark matter experiments and show that the largest σ ( χ ˜ 1 0 p ) also arise from the HPs and further that the HPs and some of the other patterns are beginning to be constrained by the most recent data from CDMS and from Xenon10 experiments. Finally, it is shown that the prospects are bright for the discovery of dark matter with σ ( χ ˜ 1 0 p ) in the range 10 − 44 ± 0.5 cm 2 due to a “Wall” consisting of a copious number of parameter points in the Chargino Patterns (CPs) where the chargino is the NLSP. The Wall, which appears in all models considered (mSUGRA, NUSUGRA and D-branes) and runs up to about a TeV in LSP mass, significantly enhances the chances for the observation of dark matter by SuperCDMS, ZEPLIN-MAX, or LUX experiments which are expected to achieve a sensitivity of 10 −45 cm 2 or more.
118496619
Scattering properties of dark atoms and molecules
There has been renewed interest in the possibility that dark matter exists in the form of atoms, analogous to those of the visible world. An important input for understanding the cosmological consequences of dark atoms is their self-scattering. Making use of results from atomic physics for the potentials between hydrogen atoms, we compute the low-energy elastic scattering cross sections for dark atoms. We find an intricate dependence upon the ratio of the dark proton to electron mass, allowing for the possibility to "design" low-energy features in the cross section. Dependences upon other parameters, namely the gauge coupling and reduced mass, scale out of the problem by using atomic units. We derive constraints on the parameter space of dark atoms by demanding that their scattering cross section does not exceed bounds from dark matter halo shapes. We discuss the formation of molecular dark hydrogen in the universe, and determine the analogous constraints on the model when the dark matter is predominantly in molecular form.
59576387
Multicomponent Dark Matter in Supersymmetric Hidden Sector Extensions
Most analyses of dark matter within supersymmetry assume the entire cold dark matter arising only from weakly interacting neutralinos. We study a new class of models consisting of U(1){sup n} hidden sector extensions of the minimal supersymmetric standard model that includes several stable particles, both fermionic and bosonic, which can be interpreted as constituents of dark matter. In one such class of models, dark matter is made up of both a Majorana dark matter particle, i.e., a neutralino, and a Dirac fermion with the current relic density of dark matter as given by WMAP being composed of the relic density of the two species. These models can explain the PAMELA positron data and are consistent with the antiproton flux data, as well as the photon data from FERMI-LAT. Further, it is shown that such models can also simultaneously produce spin-independent cross sections which can be probed in CDMS-II, XENON-100, and other ongoing dark matter experiments. The implications of the models at the LHC and at the next linear collider (NLC) are also briefly discussed.
54185957
Colored resonant signals at the LHC: largest rate and simplest topology
We study the colored resonance production at the LHC in a most general approach. We classify the possible colored resonances based on group theory decomposition, and construct their effective interactions with light partons. The production cross section from annihilation of valence quarks or gluons may be on the order of 400–1000 pb at LHC energies for a mass of 1 TeV with nominal couplings, leading to the largest production rates for new physics at the TeV scale, and simplest event topology with dijet final states. We apply the new dijet data from the LHC experiments to put bounds on various possible colored resonant states. The current bounds range from 0.9 to 2.7 TeV. The formulation is readily applicable for future searches including other decay modes.
209856078
Measurement of the Matrix Element for the Decay $\eta^{\prime} \to \eta \pi^+\pi^-$
119279570
Dark matter and Higgs bosons in the MSSM
A bstractWe investigate dark matter (DM) in the context of the minimal supersymmetric extension of the standard model (MSSM). We scan through the MSSM parameter space and search for solutions that (a) are consistent with the Higgs discovery and other collider searches; (b) satisfy the flavor constraints from B physics; (c) give a DM candidate with the correct thermal relic density; and (d) are allowed by the DM direct detection experiments. For the surviving models with our parameter scan, we find the following features: (1) The DM candidate is largely a Bino-like neutralino with non-zero but less than 20% Wino and Higgsino fractions; (2) The relic density requirement clearly pins down the solutions from the Z and Higgs resonances (Z, h, H, A funnels) and co-annihilations; (3) Future direct search experiments will likely fully cover the Z, h funnel regions, and H, A funnel regions as well except for the “blind spots”; (4) Future indirect search experiments will be more sensitive to the CP-odd Higgs exchange due to its s-wave nature; (5) The branching fraction for the SM-like Higgs decay to DM can be as high as 10%, while those from heavier Higgs decays to neutralinos and charginos can be as high as 20%. We show that collider searches provide valuable information complementary to what may be obtained from direct detections and astroparticle observations. In particular, the Z- and h-funnels with a predicted low LSP mass should be accessible at future colliders. Overall, the Higgs bosons may play an essential role as the portal to the dark sector.
121114134
Measurement of the running of the electromagnetic coupling at large momentum-transfer at LEP
The evolution of the electromagnetic coupling, α, in the momentum-transfer range 1800 GeV2 < -Q2 < 21600 GeV2 is studied with about 40 000 Bhabha-scattering events collected with the L3 detector at LEP at centre-of-mass energies √s = 189-209 GeV. The running of α is parametrised as: α(Q2) = α0/1 - C Δα(Q2), where α ≡ α(Q2 = 0) is the fine-structure constant and C = 1 corresponds to the evolution expected in QED. A fit to the differential cross section of the e+e- → e+e- process for scattering angles in the range |cos θ| < 0.9 excludes the hypothesis of a constant value of α, C = 0, and validates the QED prediction with the result: C = 1.05±0.07±0.14, where the first uncertainty is statistical and the second systematic. © 2005 Elsevier B.V. All rights reserved.
124921771
Search for neutral Higgs boson production through the process e+ e- --> Z* H0
Abstract The results of the searches for neutral Higgs boson production in the process e + e − → Z ∗ H 0 are reported, focusing on Higgs boson masses below 70 GeV. The data sample consists of three million hadronic Z 0 decays collected by the L3 experiment at LEP from 1991 through 1994. No signal is found leading to a lower limit on the mass of the Standard Model Higgs boson of 60.2 GeV at 95% C.L. These results are also interpreted in the framework of the General Two Doublet Model and limits on the nonstandard Higgs boson production through the process e + e − → Z ∗ h 0 are set. A lower limit of 66.7 GeV at 95% C.L. is obtained for the case where the Higgs decays into an invisible final state.