3.5 keV x rays as the “21 cm line” of dark atoms, and a link to light sterile neutrinos
The recently discovered 3.5 keV X-ray line from extragalactic sources may be evidence of dark matter scatterings or decays. We show that dark atoms can be the source of the emission, through their hyperfine transitions, which would be the analog of 21 cm radiation from a dark sector. We identify two families of dark atom models that match the X-ray observations and are consistent with other constraints. In the first, the hyperfine excited state is long-lived compared to the age of the universe, and the dark atom mass is relatively unconstrained; dark atoms could be strongly self-interacting in this case. In the second, the excited state is short-lived and viable models are parameterized by the value of the dark proton-to-electron mass ratio $R$: for $R = 10^2-10^4$, the dark atom mass is predicted be in the range $350-1300$ GeV, with fine structure constant $\alpha'\cong 0.1-0.6$. In either class of models, the dark photon must be massive with $m_{\gamma'} \gtrsim$ 1 MeV and decay into $e^+ e^-$. Evidence for the model could come from direct detection of the dark atoms. In a natural extension of this framework, the dark photon could decay predominantly into invisible particles, for example $\sim 0.5$ eV sterile neutrinos, explaining the extra radiation degree of freedom recently suggested by data from BICEP2, while remaining compatible with BBN.

title: The Stueckelberg Extension and Milli Weak and Milli Charged Dark Matter
abstract: 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...

title: Explaining PAMELA and WMAP data through coannihilations in extended SUGRA with collider implications
abstract: 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.

title: LHC constraints on dark matter with (130 GeV) gamma ray lines
abstract: 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.

title: 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.

title: Scattering properties of dark atoms and molecules
abstract: 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.

title: Light neutralino dark matter: direct/indirect detection and collider searches
abstract: A bstractWe study the neutralino being the Lightest Supersymmetric Particle (LSP) as a cold Dark Matter (DM) candidate with a mass less than 40 GeV in the framework of the Next-to-Minimal-Supersymmetric-Standard-Model (NMSSM). We find that with the current collider constraints from LEP, the Tevatron and the LHC, there are three types of light DM solutions consistent with the direct/indirect searches as well as the relic abundance considerations: (i) A1, H1-funnels, (ii) stau coannihilation and (iii) sbottom coannihilation. Type-(i) may take place in any theory with a light scalar (or pseudo-scalar) near the LSP pair threshold; while Type-(ii) and (iii) could occur in the framework of Minimal-Supersymmetric-Standard-Model (MSSM) as well. We present a comprehensive study on the properties of these solutions and point out their immediate relevance to the experiments of the underground direct detection such as superCDMS and LUX/LZ, and the astro-physical indirect search such as Fermi-LAT. We also find that the decays of the SM-like Higgs boson may be modified appreciably and the new decay channels to the light SUSY particles may be sizable. The new light CP-even and CP-odd Higgs bosons will decay to a pair of LSPs as well as other observable final states, leading to interesting new Higgs phenomenology at colliders. For the light sfermion searches, the signals would be very challenging to observe at the LHC given the current bounds. However, a high energy and high luminosity lepton collider, such as the ILC, would be able to fully cover these scenarios by searching for events with large missing energy plus charged tracks or displaced vertices.

title: Bose-Einstein correlations of neutral and charged pions in hadronic Z decays
abstract: Bose–Einstein correlations of both neutral and like-sign charged pion pairs are measured in a sample of 2 million hadronic Z decays collected with the L3 detector at LEP. The analysis is performed in the four-momentum difference range 300 MeV Q

title: Measurement of genuine three-particle Bose-Einstein correlations in hadronic Z decay
abstract: We measure three-particle Bose-Einstein correlations in hadronic Z decay with the L3 detector at LEP. Genuine three-particle Bose-Einstein correlations are observed. By comparing two- and three-particle correlations we find that the data are consistent with fully incoherent pion production.

title: Measurement of the Photon Structure Function at High Q 2 at LEP
abstract: The structure functions of real and virtual photons are derivedfrom cross section measurements of the reaction$\rm e^+e^-\rightarrow e^+e^- + \hbox{hadrons}$ at LEP.The reaction is studied at $\sqrt{\rm {s}} \simeq 91$ GeV with the L3detector. One of the final state electrons is detected at a large angle relative to the beam direction, leading to $Q^2$ values between40 GeV$^2$ and 500 GeV$^2$.The other final state electron is either undetected or it is detected ata four-momentum transfer squared $P^2$ between 1 GeV$^2$ and 8 GeV$^2$.These measurements are compared with predictions of the Quark PartonModel and other QCD based models.

title: Dark matter and Higgs bosons in the MSSM
abstract: 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.