12,149 research outputs found
Signals of a Light Dark Force in the Galactic Center
Recent evidence for an excess of gamma rays in the GeV energy range about the
Galactic Center have refocused attention on models of dark matter in the low
mass regime (). Because this is an experimentally
well-trod energy range, it can be a challenge to develop simple models that
explain this excess, consistent with other experimental constraints. We
reconsider models where the dark matter couples to dark photon, which has a
weak kinetic mixing to the Standard Model photon, or scalars with a weak mixing
with the Higgs boson. We focus on the light () dark mediator
mass regime. Annihilations into the dark mediators can produce observable gamma
rays through decays to , through radiative processes when decaying to
charged particles (), and subsequent interactions of
high energy with gas and light. However, these models have no signals
of production, which is kinematically forbidden. We find that in these
models, the shape of resulting gamma-ray spectrum can provide a good fit to the
excess at Galactic Center. We discuss further constraints from AMS-02, and find
regions of compatibility.Comment: 39 pages, 14 figures, references updated and discussion of CMB
constraints include
Re-Study on the wave functions of states in LFQM and the radiative decays of
The Light-front quark model (LFQM) has been applied to calculate the
transition matrix elements of heavy hadron decays. However, it is noted that
using the traditional wave functions of the LFQM given in literature, the
theoretically determined decay constants of the obviously
contradict to the data. It implies that the wave functions must be modified.
Keeping the orthogonality among the states and fitting their decay
constants we obtain a series of the wave functions for . Based on
these wave functions and by analogy to the hydrogen atom, we suggest a modified
analytical form for the wave functions. By use of the modified
wave functions, the obtained decay constants are close to the experimental
data. Then we calculate the rates of radiative decays of . Our predictions are consistent with the experimental data on
decays within the theoretical and experimental
errors.Comment: 10 pages, 2 figures, 1 table. Typos corrected and more discussions
added. accepted for publication in Physical Review
Exploring open-charm decay mode of charmonium-like state
The newly observed exotic states are definitely not in the standard
structures, thus their existence composes a challenge to our
understanding on the fundamental principles of hadron physics. Therefore the
studies on their decay patterns which are determined by the non-perturbative
QCD will definitely shed light on the concerned physics. Generally the
four-quark states might be in a molecular state or tetraquark or their mixture.
In this work, we adopt the suggestion that is a charmonium-like
tetraquark made of a diquark and an anti-diquark. If it is true, its favorable
decay mode should be decaying into an open-charm baryon pair, since
such a transition occurs via strong interaction and is super-OZI-allowed. In
this work, we calculate the decay width of
in the framework of the quark pair creation (QPC) model. Our numerical results
on the partial width computed in the tetraquark configuration coincide with the
Belle data within a certain error tolerance.Comment: 8 pages, 4 figures, 1 table. Accepted by Eur. Phys. J.
An optimistic CoGeNT analysis
Inspired by a recently proposed model of millicharged atomic dark matter
(MADM), we analyze several classes of light dark matter models with respect to
CoGeNT modulated and unmodulated data, and constraints from CDMS, XENON10 and
XENON100. After removing the surface contaminated events from the original
CoGeNT data set, we find an acceptable fit to all these data (but with the
modulating part of the signal making a statistically small contribution), using
somewhat relaxed assumptions about the response of the null experiments at low
recoil energies, and postulating an unknown modulating background in the CoGeNT
data at recoil energies above 1.5 keVee. We compare the fits of MADM---an
example of inelastic magnetic dark matter---to those of standard elastically
and inelastically scattering light WIMPs (eDM and iDM). The iDM model gives the
best fit, with MADM close behind. The dark matter interpretation of the DAMA
annual modulation cannot be made compatible with these results however. We find
that the inclusion of a tidal debris component in the dark matter phase space
distribution improves the fits or helps to relieve tension with XENON
constraints.Comment: 16 pages, 11 figures; v2: added discussion of dipole-dipole
scattering and details of matrix elements; also implications of XENON100 2012
limits. Qualitative conclusions unchanged. Published versio
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