8142176
Gluino NLSP, dark matter via gluino coannihilation, and LHC signatures
The possibility that the gluino is the next to the lightest supersymmetric particle (NLSP) is discussed and it is shown that this situation arises in nonuniversal supergravity models within a significant part of the parameter space compatible with all known experimental bounds. It is then shown that the gluino NLSP (GNLSP) models lead to a compressed sfermion spectrum with the sleptons often heavier than the squarks at least for the first two generations. The relic density here is governed by gluino coannihilation which is responsible for a relatively small mass splitting between the gluino and the neutralino masses. Thus the GNLSP class of models is very predictive first because the supersymmetry (SUSY) production cross sections at the CERN LHC are dominated by gluino production and second because the gluino production itself proceeds dominantly through a single channel which allows for a direct determination of the gluino mass and an indirect determination of the neutralino mass due to a linear relation between these two masses which is highly constrained by coannihilation. A detailed analysis of these models shows that the jet production and tagged b jets from the gluino production can be discriminated from the standard model background with appropriate cuts.more » It is found that the GNLSP models can be tested with just 10 fb{sup -1} of integrated luminosity and may therefore be checked with low luminosity runs in the first data at the LHC. Thus if a GNLSP model is realized, the LHC will turn into a gluino factory through a profuse production of gluinos with typically only a small fraction < or approx. 5% of total SUSY events arising from other production modes over the allowed GNLSP model parameter space.« less
118669821
LHC constraints on dark matter with (130 GeV) gamma ray lines
Dark matter annihilation into photons in our galaxy would constitute an exciting indirect signal of its existence, as underscored by tentative evidence for 130 GeV dark matter in Fermi/LAT data. Models that give a large annihilation cross section into photons typically require the dark matter to couple to, or be composed of, new charged particles, that can be produced in colliders. We consider the LHC constraints on some representative models of these types, including the signals of same-sign dileptons, opposite-sign dileptons, events mimicking the production and decay of excited leptons, four-photon events, resonant production of composite vectors decaying into two photons, and monophoton events.
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.
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.
15277907
The Stueckelberg Extension and Milli Weak and Milli Charged Dark Matter
A overview is given of the recent developments in the U(1)X Stueckelberg extensions of the Standard Model and of MSSM where all the Standard Model particles are neutral under the U(1)X, but an axion which is absorbed is charged under both U(1)X and U(1)Y and acts as the connector field coupling the Standard Model sector with the Stueckelberg sector. Coupled with the usual Higgs mechanism that breaks the SU(2)L×U(1)Y gauge symmetry, this scenario produces mixings in the neutral gauge boson sector generating an extra Z′ boson. The couplings of the extra Z′ to the Standard Model particles are milli weak but its couplings to the hidden sector matter, defined as matter that couples only to the gauge field of U(1)X, can be of normal electro‐weak strength. It is shown that such extensions, aside from the possibility of leading to a sharp Z′ resonance, lead to two new types of dark matter: milli weak (or extra weak) and milli charged. An analysis of the relic density shows that the WMAP‐3 constraints can be satis...
53509420
Explaining PAMELA and WMAP data through coannihilations in extended SUGRA with collider implications
The PAMELA positron excess is analyzed within the framework of nonuniversal supergravity (SUGRA) models with an extended $U(1{)}^{n}$ gauge symmetry in the hidden sector leading to neutralino dark matter with either a mixed Higgsino-wino lightest $R$-parity odd supersymmetric particle (LSP) or an essentially pure wino-dominated LSP. The Higgsino-wino LSP can produce the observed PAMELA positron excess and satisfy relic density constraints in the extended class of models due to a near degeneracy of the mass spectrum of the extended neutralino sector with the LSP mass. The simultaneous satisfaction of the WMAP relic density data and the PAMELA data is accomplished through a coannihilation mechanism (${B}_{\mathrm{Co}}\ensuremath{-}\mathrm{\text{mechanism}}$), and leads to predictions of a neutralino and a chargino in the mass range (180--200) GeV as well as low-lying sparticles accessible at colliders. We show that the models are consistent with the antiproton constraints from PAMELA as well as the photon flux data from EGRET and FERMI-LAT. Predictions for the scalar neutralino-proton cross section relevant for the direct detection of dark matter are also discussed and signatures at the LHC for these PAMELA inspired models are analyzed. It is shown that the mixed Higgsino-wino LSP model will be discoverable with as little as $1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data and is thus a prime candidate for discovery in the low luminosity runs at the LHC.
120858051
Parafermion Fields Constructed by Current Algebra
In this letter, the parafermion fields constructed by current algebra are considered. It is proved that there must be a parafermion field with respect to each form of current algebra. We also obtain the corresponding representation and unitary relation of the parafermion field from any current algebra.
124427740
ALICE Technical Design Report on Forward Detectors : FMD, T0 and V0
118380500
Simplified Models for LHC New Physics Searches
This document proposes a collection of simplified models relevant to the design of new-physics searches at the Large Hadron Collider (LHC) and the characterization of their results. Both ATLAS and CMS have already presented some results in terms of simplified models, and we encourage them to continue and expand this effort, which supplements both signature-based results and benchmark model interpretations. A simplified model is defined by an effective Lagrangian describing the interactions of a small number of new particles. Simplified models can equally well be described by a small number of masses and cross-sections. These parameters are directly related to collider physics observables, making simplified models a particularly effective framework for evaluating searches and a useful starting point for characterizing positive signals of new physics. This document serves as an official summary of the results from the 'Topologies for Early LHC Searches' workshop, held at SLAC in September of 2010, the purpose of which was to develop a set of representative models that can be used to cover all relevant phase space in experimental searches. Particular emphasis is placed on searches relevant for the first similar to 50-500 pb(-1) of data and those motivated by supersymmetric models. This note largely summarizes material posted at http://lhcnewphysics.org/, which includes simplified model definitions, Monte Carlo material, and supporting contacts within the theory community. We also comment on future developments that may be useful as more data is gathered and analyzed by the experiments.
125712067
Measurement of the Lepton Forward-Backward Asymmetry in Inclusive $B \rightarrow X_s \ell^+ \ell^-$ Decays
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.