We constrain the possibility of a new pseudoscalar coupling between the muon and proton using a recent measurement of the 2S hyperfine splitting in muonic hydrogen.
We describe a characteristic signature of dark matter (DM) annihilation or decay into gamma-rays. We show that if the total angular momentum of the initial DM particle(s) vanishes, and helicity suppression operates to prevent annihilation/decay into
light fermion pairs, then the amplitude for the dominant 3-body final state f^+f^-gamma has a unique form dictated by gauge invariance. This amplitude and the corresponding energy spectra hold for annihilation of DM Majorana fermions or self-conjugate scalars, and for decay of DM scalars, thus encompassing a variety of possibilities. Within this scenario, we analyze Fermi LAT, PAMELA and HESS data, and predict a hint in future Fermi gamma-ray data that portends a striking signal at atmospheric Cherenkov telescopes (ACTs).
We analyze new diffuse gamma-ray data from the Fermi Gamma-ray Space Telescope, which do not confirm an excess in the EGRET data at galactic mid-latitudes, in combination with measurements of electron and positron fuxes from PAMELA, Fermi and HESS wi
thin the context of three possible sources: dark matter (DM) annihilation or decay into charged leptons, and a continuum distribution of pulsars. We allow for variations in the backgrounds, consider several DM halo profiles, and account for systematic uncertainties in data where possible. We find that all three scenarios represent the data well. The pulsar description holds for a wide range of injection energy spectra. We compare with ATIC data and the WMAP haze where appropriate, but do not fit these data since the former are discrepant with Fermi data and the latter are subject to large systematic uncertainties. We show that for cusped halo profiles, Fermi could observe a spectacular gamma-ray signal of DM annihilation from the galactic center while seeing no excess at mid-latitudes.
Assuming that the positron excess in PAMELA satellite data is a consequence of annihilations of cold dark matter, we consider from a model-independent perspective if the data show a preference for the spin of dark matter. We then perform a general an
alysis of annihilations into two-body final states to determine what weighted combination of channels best describes the data.
If sneutrinos are the lightest supersymmetry partners and $R$-parity is not conserved, the process $e^+e^- to tilde {bar u} tilde { u}$ can have striking signatures due to the decay modes $tilde{ u}toell^+ell^-$ or $tilde{ u}to q bar q$. We present c
ross section formulas and discuss event rates and detection at the upgraded $e^+e^-$ collider LEP. Four-lepton signals should be detectable up to sneutrino mass $tilde {m}_ u = 80$ GeV and maybe beyond; four-jet signals should be detectable up to $tilde {m}_ u = 70$ GeV, but would probably be obscured thereafter by $WW$ background.
The asymmetries ${cal A}_k equiv [Gamma(twddec) -Gamma(tbwddec)] /[Gamma(twddec) + Gamma(tbwddec)]$ in the partial widths of the top quark decays are discussed within the Standard Model (SM), the Two-Higgs-Doublet Model (2HDM) and supersymmetric exte
nsions of the SM (SSM). The leading contributions to these asymmetries in the SM and in the 2HDM are induced by the up-type quark self-energy diagrams and are found to be very small. However, in the SSM, the asymmetry ${cal A}_b$ can be substantial, ${cal O}(alpha_{QCD})$, provided the CP-violating phase of gluino-top-stop couplings is not suppressed. Within the SSM ${cal A}_b$ is generated by the vertex corrections.
