166163535
RESULTS FROM DAMA/LIBRA
118080735
Atmospheric Cherenkov telescope.
118074881
Search for TeV Gamma Ray Bursts from Evaporating Primordial Black Holes
Data taken with ACT2 and ACT3 between 1995 and 1997 are used to search for 0.1 s bursts of TeV gamma ray from evaporating primordial black holes (PBHs). There is no evidence for such bursts in the dataset. Using the result, the upper limit of 3×108pc-3yr-1 on the rate-density of evaporating PBHs is set in the vicinity of the solar system at a 99% confidence level.
118902201
A Telescope to Detect VHE Gamma Ray Sources
11786208
Universal non-oblique corrections in Higgsless models and beyond
Abstract Recently Barbieri et al. have introduced a formalism to express the deviations of electroweak interactions from their Standard Model forms in “universal” theories, i.e., theories in which the corrections due to new physics can be expressed solely by modifications to the two-point correlation function of electroweak gauge currents of fermions. The parameters introduced by these authors are defined by the properties of the correlation functions at zero momentum, and differ from the quantities calculated by examining the on-shell properties of the electroweak gauge bosons. In this Letter we discuss the relationship between the zero-momentum and on-shell parameters. In addition, we present the results of a calculation of these zero-momentum parameters in an arbitrary Higgsless model in which the low-energy ρ parameter is one and which can be deconstructed to a linear chain of SU ( 2 ) groups adjacent to a chain of U ( 1 ) groups. Our results demonstrate the importance of the universal “non-oblique” corrections which are present and elucidate the relationships among various calculations of electroweak quantities in these models. Our expressions for these zero-momentum parameters depend only on the spectrum of heavy vector-boson masses; therefore, the minimum size of the deviations present in these models is related to the upper bound on the heavy vector-boson masses derived from unitarity. We find that these models are disfavored by precision electroweak data, independent of any assumptions about the background metric or the behavior of the bulk coupling.
11320645
Single charged Higgs boson production in polarized photon collisions and the probe of new physics
We study single charged Higgs boson production in photon-photon collisions as a probe of the new dynamics of Higgs interactions. This is particularly important when the mass ${(M}_{{H}^{\ifmmode\pm\else\textpm\fi{}}})$ of charged Higgs bosons ${(H}^{\ifmmode\pm\else\textpm\fi{}})$ is relatively heavy and above the kinematic limit of the pair production ${(M}_{{H}^{\ifmmode\pm\else\textpm\fi{}}}g\sqrt{s}/2).$ We analyze the cross sections of single charged Higgs boson production from the photon-photon fusion processes $\ensuremath{\gamma}\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}{\ensuremath{\tau}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}{H}^{+}$ and $\ensuremath{\gamma}\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}b\overline{c}{H}^{+},$ as motivated by the minimal supersymmetric standard model and the dynamical top-color model. We find that the cross sections at such a $\ensuremath{\gamma}\ensuremath{\gamma}$ collider can be sufficiently large even for ${M}_{{H}^{\ifmmode\pm\else\textpm\fi{}}}g\sqrt{s}/2,$ and is typically one to two orders of magnitude higher than that at its parent ${e}^{\ensuremath{-}}{e}^{+}$ collider. We further demonstrate that the polarized photon beams can provide an important means to determine the chirality structure of Higgs Yukawa interactions with the fermions.
888469
Ideal fermion delocalization in five dimensional gauge theories
We discuss ideal delocalization of fermions in a bulk $SU(2)\ifmmode\times\else\texttimes\fi{}SU(2)\ifmmode\times\else\texttimes\fi{}U(1)$ Higgsless model with a flat or warped extra dimension. So as to make an extra dimensional interpretation possible, both the weak and hypercharge properties of the fermions are delocalized, with the $U(1{)}_{Y}$ current of left-handed fermions being correlated with the $SU(2{)}_{W}$ current. We find that (to subleading order) ideal fermion delocalization yields vanishing precision electroweak corrections in this continuum model, as found in corresponding theory-space models based on deconstruction. In addition to explicit calculations, we present an intuitive argument for our results based on Georgi's spring analogy. We also discuss the conditions under which the essential features of an $SU(2)\ifmmode\times\else\texttimes\fi{}SU(2)\ifmmode\times\else\texttimes\fi{}U(1)$ bulk gauge theory can be captured by a simpler $SU(2)\ifmmode\times\else\texttimes\fi{}SU(2)$ model.
6985151
The Structure of electroweak corrections due to extended gauge symmetries
This paper studies models with extended electroweak gauge sectors of the form SU(2) x SU(2) x U(1) x [SU(2) or U(1)]. We establish the general behavior of corrections to precision electroweak observables in this class of theories and connect our results to previous work on specific models whose electroweak sectors are special cases of our extended group.
119072370
LHC signatures of two-Higgs-doublets with fourth family
A bstractOn-going Higgs searches in the light mass window are of vital importance for testing the Higgs mechanism and probing new physics beyond the standard model (SM). The latest ATLAS and CMS searches for the SM Higgs boson at the LHC (7 TeV) found some intriguing excesses of events in the γγ/VV* channels (V = Z, W) around the mass-range of 124–126 GeV. We explore a possible explanation of the γγ and VV* signals from the light CP-odd Higgs A0 or CP-even Higgs h0 from the general two-Higgs-doublet model with fourth-family fermions. We demonstrate that by including invisible decays of the Higgs boson A0or h0to fourth-family neutrinos, the predicted γγ and VV* signals can explain the observed new signatures at the LHC, and will be further probed by the forthcoming LHC runs in 2012.