1,916 research outputs found
Dutch agricultural development and its importance to China; case study : agriculture in Wujiang - an overview
Two-mediator dark matter models and cosmic electron excess
The cosmic electron energy spectrum recently observed by the DAMPE experiment
exhibits two interesting features, including a break around 0.9 TeV and a sharp
resonance near 1.4 TeV. In this analysis, we propose a dark matter explanation
to both exotic features seen by DAMPE. In our model, dark matter annihilates in
the galaxy via two different channels that lead to both a narrow resonance
spectrum near 1.4 TeV and electron excess events over an extended energy range
thus generating the break structure around TeV. The two annihilation channels
are mediated by two gauge bosons that interact both with dark matter and with
the standard model fermions. Dark matter annihilations through the s-channel
process mediated by the heavier boson produce monoenergetic electron-positron
pairs leading to the resonance excess. The lighter boson has a mass smaller
than the dark matter such that they can be on-shell produced in dark matter
annihilations in the galaxy; the lighter bosons in the final state subsequently
decay to generate the extended excess events due to the smeared electron energy
spectrum in this process. We further analyze constraints from various
experiments, including HESS, Fermi, AMS, and LHC, to the parameter space of the
model where both excess events can be accounted for. In order to interpret the
two new features in the DAMPE data, dark matter annihilation cross sections in
the current galaxy are typically much larger than the canonical thermal cross
section needed for the correct dark matter relic abundance. This discrepancy,
however, is remedied by the nonperturbative Sommerfeld enhancement because of
the existence of a lighter mediator in the model.Comment: 23 pages, 21 figure
Photoproduction of Pentaquark and Chiral Symmetry Restoration in Hot and Dense Medium
The photoproduction rate of pentaquark is calculated in a hot and
dense medium. At high temperature and density, due to the restoration of chiral
symmetry, photoproduction energy threshold is increased. Above the thresold the
production cross section is strongly enhanced.Comment: 5 pages, 3 figure
Harish-Chandra modules over the \Q Heisenberg-Virasoro Algebra
In this paper, it is proved that all irreducible Harish-Chandra modules over
the \Q Heisenberg-Virasoro algebra are of intermediate series (all weight
spaces are 1-dimensional)
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