3,836 research outputs found
Direct detection and solar capture of dark matter with momentum and velocity dependent elastic scattering
We explore the momentum and velocity dependent elastic scattering between the
dark matter (DM) particles and the nuclei in detectors and the Sun. In terms of
the non-relativistic effective theory, we phenomenologically discuss ten kinds
of momentum and velocity dependent DM-nucleus interactions and recalculate the
corresponding upper limits on the spin-independent DM-nucleon scattering cross
section from the current direct detection experiments. The DM solar capture
rate is calculated for each interaction. Our numerical results show that the
momentum and velocity dependent cases can give larger solar capture rate than
the usual contact interaction case for almost the whole parameter space. On the
other hand, we deduce the Super-Kamiokande's constraints on the solar capture
rate for eight typical DM annihilation channels. In contrast to the usual
contact interaction, the Super-Kamiokande and IceCube experiments can give more
stringent limits on the DM-nucleon elastic scattering cross section than the
current direct detection experiments for several momentum and velocity
dependent DM-nucleus interactions. In addition, we investigate the mediator
mass's effect on the DM elastic scattering cross section and solar capture
rate.Comment: 18 pages, 4 figures, 2 tables. minor changes and a reference added,
published in Nuclear Physics
Enhancement of Dark Matter Annihilation via Breit-Wigner Resonance
The Breit-Wigner enhancement of the thermally averaged annihilation cross
section is shown to provide a large boost factor when the dark
matter annihilation process nears a narrow resonance. We explicitly demonstrate
the evolution behavior of the Breit-Wigner enhanced as the function
of universe temperature for both the physical and unphysical pole cases. It is
found that both of the cases can lead an enough large boost factor to explain
the recent PAMELA, ATIC and PPB-BETS anomalies. We also calculate the coupling
of annihilation process, which is useful for an appropriate model building to
give the desired dark matter relic density.Comment: 4 pages, 4 figures, references added, accepted for publication in
Physical Review
A Deep Architecture for Semantic Matching with Multiple Positional Sentence Representations
Matching natural language sentences is central for many applications such as
information retrieval and question answering. Existing deep models rely on a
single sentence representation or multiple granularity representations for
matching. However, such methods cannot well capture the contextualized local
information in the matching process. To tackle this problem, we present a new
deep architecture to match two sentences with multiple positional sentence
representations. Specifically, each positional sentence representation is a
sentence representation at this position, generated by a bidirectional long
short term memory (Bi-LSTM). The matching score is finally produced by
aggregating interactions between these different positional sentence
representations, through -Max pooling and a multi-layer perceptron. Our
model has several advantages: (1) By using Bi-LSTM, rich context of the whole
sentence is leveraged to capture the contextualized local information in each
positional sentence representation; (2) By matching with multiple positional
sentence representations, it is flexible to aggregate different important
contextualized local information in a sentence to support the matching; (3)
Experiments on different tasks such as question answering and sentence
completion demonstrate the superiority of our model.Comment: Accepted by AAAI-201
Searching for Dark Matter Signals in the Left-Right Symmetric Gauge Model with CP Symmetry
We investigate singlet scalar dark matter (DM) candidate in a left-right
symmetric gauge model with two Higgs bidoublets (2HBDM) in which the
stabilization of the DM particle is induced by the discrete symmetries P and
CP. According to the observed DM abundance, we predict the DM direct and
indirect detection cross sections for the DM mass range from 10 GeV to 500 GeV.
We show that the DM indirect detection cross section is not sensitive to the
light Higgs mixing and Yukawa couplings except the resonance regions. The
predicted spin-independent DM-nucleon elastic scattering cross section is found
to be significantly dependent on the above two factors. Our results show that
the future DM direct search experiments can cover the most parts of the allowed
parameter space. The PAMELA antiproton data can only exclude two very narrow
regions in the 2HBDM. It is very difficult to detect the DM direct or indirect
signals in the resonance regions due to the Breit-Wigner resonance effect.Comment: 24 pages, 8 figures. minor changes and a reference added, published
in Phys. Rev.
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