118458330
A Model Independent Method to Study Dark Matter Induced Leptons and Gamma Rays
By using recent data, we directly determine the dark matter (DM)-induced e± spectrum at the source from experimental measurements at the earth, without reference to specific particle physics models. The DM-induced gamma rays emitted via inverse Compton scattering are then obtained in a model-independent way. However, the results depend on the choice of the astrophysical e± background, which is not reliably known. Nevertheless, we calculate, as an illustration, the fluxes of gamma rays from the Fornax cluster in the decaying DM scenario with various astrophysical e± backgrounds. Without any assumptions on details of the DM model, the predictions turn out to be either in disagreement with or only marginally below the upper limits measured recently by the Fermi-LAT Collaboration. In addition, these DM-induced ICS gamma rays in the GeV range are shown to be almost independent of choices of cosmic ray propagation model and of DM density profile, when a given astrophysical e± background is assumed. This provide...
119089054
Leading-order actions of Goldstino fields
This paper starts with a self-contained discussion of the so-called Akulov–Volkov action $\mathcal{S}_{\mathrm{AV}}$, which is traditionally taken to be the leading-order action of the Goldstino field. Explicit expressions for $\mathcal{S}_{\mathrm{AV}}$ and its chiral version $\mathcal{S}_{\mathrm{AV}}^{\mathrm{ch}}$ are presented. We then turn to the issue on how these actions are related to the leading-order action $\mathcal{S}_{\mathrm{NL}}$ proposed in the newly proposed constrained superfield formalism. We show that $\mathcal{S}_{\mathrm{NL}}$ may yield $\mathcal{S}_{\mathrm {AV}}/\mathcal{S}_{\mathrm{AV}}^{\mathrm{ch}}$ or a totally different action $\mathcal{S}_{\mathrm{KS}}$, depending on how the auxiliary field in the former is integrated out. However, $\mathcal{S}_{\mathrm{KS}}$ and $\mathcal{S}_{\mathrm {AV}}/\mathcal{S}_{\mathrm{AV}}^{\mathrm{ch}}$ always yield the same S-matrix elements, as one would have expected from general considerations in quantum field theory.
73712405
Decaying dark matter in supersymmetric SU(5) models
Abstract Motivated by recent observations from PAMELA, Fermi and H.E.S.S., we consider dark matter decays in the framework of supersymmetric SU(5) grand unification theories. An SU(5) singlet S is assumed to be the main component of dark matters, which decays into visible particles through dimension six operators suppressed by the grand unification scale. Under certain conditions, S decays dominantly into a pair of sleptons with universal coupling for all generations. Subsequently, electrons and positrons are produced from cascade decays of these sleptons. These cascade decay chains smooth the e + + e − spectrum, which permit naturally a good fit to the Fermi-LAT data. The observed positron fraction upturn by PAMELA can be reproduced simultaneously. We have also calculated diffuse gamma-ray spectra due to the e ± excesses and compared them with the preliminary Fermi-LAT data from 0.1 GeV to 10 GeV in the region 0 ° ⩽ l ⩽ 360 ° , 10 ° ⩽ | b | ⩽ 20 ° . The photon spectrum of energy above 100 GeV, mainly from final state radiations, may be checked in the near future.
119224770
Gamma-rays from nearby clusters: Constraints on selected decaying dark matter models
Abstract Recently, the Fermi-LAT Collaboration reported upper limits on the GeV gamma-ray flux from nearby clusters of galaxies. Motivated by these limits, we study corresponding constraints on gamma-ray emissions from two specific decaying dark matter models, one via grand unification scale suppressed operators and the other via R-parity violating operators. Both can account for the PAMELA and Fermi-LAT excesses of e ± . For GUT decaying dark matter, the gamma-rays from the M49 and Fornax clusters, with energy in the range of 1 to 10 GeV, lead to the most stringent constraints to date. As a result, this dark matter is disfavored with conventional model of e ± background. In addition, it is likely that some tension exists between the Fermi-LAT e ± excess and the gamma-ray constraints for any decaying dark matter model, provided conventional model of e ± background is adopted. Nevertheless, the GUT decaying dark matter can still solely account for the PAMELA positron fraction excess without violating the gamma-ray constraints. For the gravitino dark matter model with R-parity violation, cluster observations do not give tight constraints. This is because a different e ± background has been adopted which leads to relatively light dark matter mass around 200 GeV.
119285074
Light top squark in precision top quark sample
The uncertainty of $t\bar{t}$ production cross section measurement at LHC is at a-few-percent level which still allows the stop pair production $\tilde{t}\tilde{t}^{*}$ with identical final states $2b+\ell+nj+{E}_{T}$. In this paper, we attempt to use the existing measurement of $W$-polarization in top quark decay to improve the distinction between stop and top quark states. We apply the ATLAS $\chi^2$ method of $W$-polarization measurement in semi-leptonic $t\bar{t}$ final state to semi-leptonic stop pair samples and study its prediction. We find that the faked top events from stop mostly contribute to the left-handed polarized $W$ due to the reconstruction. The benchmark point with maximal contribution to top events only changes $F_{L}$ by 1%. After comparing with the current experiments, we conclude that the current measurement of $W$-polarization in $t$ decay cannot exclude the light stop scenario.
119298883
Is polarization effect visible in leptonic SUSY searches?
X iv :1 31 2. 15 27 v1 [ he pph ] 5 D ec 2 01 3 Is polarization effect visible in leptonic SUSY searches? Kai Wang, Liucheng Wang, Tao Xu , and Liangliang Zhang a Zhejiang Institute of Modern Physics and Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, CHINA b Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA c School of Physics, Nankai University, Tianjin 300071, CHINA
125590985
Experimental study of f0(975) in J / psi decays
14698730
Independent measurement of the neutrino mixing angle theta(13) via neutron capture on hydrogen at Daya Bay
A new measurement of the θ_(13) mixing angle has been obtained at the Daya Bay Reactor Neutrino Experiment via the detection of inverse beta decays tagged by neutron capture on hydrogen. The antineutrino events for hydrogen capture are distinct from those for gadolinium capture with largely different systematic uncertainties, allowing a determination independent of the gadolinium-capture result and an improvement on the precision of the θ_(13) measurement. With a 217-day antineutrino data set obtained with six antineutrino detectors and from six 2.9 GW_(th) reactors, the rate deficit observed at the far hall is interpreted as sin^2 2θ_(13) = 0.083±0.018 in the three-flavor oscillation model. When combined with the gadolinium-capture result from Daya Bay, we obtain sin^2 2θ_(13) = 0.089±0.008 as the final result for the six-antineutrino-detector configuration of the Daya Bay experiment.
118448708
Dark matter constraints on the left-right symmetric model with Z(2) symmetry
In the framework of the left-right symmetric model, we investigate an interesting scenario, in which the so-called vacuum expectation value (VEV)-seesaw problem can be naturally solved with Z(2) symmetry. In such a scenario, we find a pair of stable weakly interacting massive particles (WIMPs), which may be the cold dark matter candidates. However, the WIMP-nucleon cross section is 3-5 orders of magnitude above the present upper bounds from the direct dark matter detection experiments for m similar to 10(2)-10(4) GeV. As a result, the relic number density of two stable particles has to be strongly suppressed to a very small level. Nevertheless, our analysis shows that this scenario cannot provide very large annihilation cross sections so as to give the desired relic abundance except for the resonance case. Only for the case if the rotation curves of disk galaxies are explained by the modified Newtonian dynamics (MOND), the stable WIMPs could be as the candidates of cold dark matter.
7332532
Spectral measurement of electron antineutrino oscillation amplitude and frequency at Daya Bay.
A measurement of the energy dependence of antineutrino disappearance at the Daya Bay reactor neutrino experiment is reported. Electron antineutrinos (ν¯(e)) from six 2.9  GW(th) reactors were detected with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls. Using 217 days of data, 41 589 (203 809 and 92 912) antineutrino candidates were detected in the far hall (near halls). An improved measurement of the oscillation amplitude sin(2)2θ(13)=0.090(-0.009)(+0.008) and the first direct measurement of the ν¯(e) mass-squared difference |Δm(ee)2|=(2.59(-0.20)(+0.19))×10(-3)  eV2 is obtained using the observed ν¯(e) rates and energy spectra in a three-neutrino framework. This value of |Δm(ee)2| is consistent with |Δm(μμ)2| measured by muon neutrino disappearance, supporting the three-flavor oscillation model.
118438822
Dark matter and Higgs phenomenology predicted by left-right twin Higgs model in light of CDMS II results
The left-right twin Higgs model predicts a light stable scalar Ŝ, which is a candidate for WIMP dark matter. We study its scattering on nucleon and find that the cross section is below the CDMS II upper bound but can reach the SuperCDMS sensitivity. Then we study the Higgs phenomenology by paying special attention to the decay h → ŜŜ which is strongly correlated with the dark matter scattering on nucleon. We find that such an invisible decay can be sizable, which can severely suppress the conventional decay modes like h → VV (V = W, Z) and $ h \to b\bar b $. On the other hand, compared to the SM prediction, the rates of Higgs boson productions at the LHC via gluon-gluon fusion, weak boson fusion or in association with top quark pairs are all reduced significantly, e.g., the gluon-gluon fusion channel can be suppressed by about 30%.