269 research outputs found
Implication of the HyperCP boson (214 MeV) in the flavour changing neutral current processes
We analyze the inclusive and the exclusive
flavour changing neutral current decays in
the light of HyperCP boson of mass 214 MeV recently observed in the
hyperon decay . Using the branching ratio data of
the above inclusive and exclusive decays, we obtain constraints on
and , the scalar and pseudo-scalar coupling constants of the
vertices.Comment: 18 pages, 10 eps figure
Constraints on light Dark Matter fermions from relic density consideration and Tsallis statistics
The cold dark matter fermions with mass MeV scale, pair produced inside the
supernova SN1987A core, can freely stream away from the supernovae and hence
contributes to its energy loss rate. Similar type of DM fermions(having similar
kind of coupling to the standard model photon), produced from some other
sources earlier, could have contributed to the relic density of the Universe.
Working in a theory with an effective dark matter-photon coupling (inversely
proportional to the scale ) in the formalism of Tsallis statistics, we
find the dark matter contribution to the relic density and obtain a upper bound
on using the experimental bound on the relic density for cold
non-baryonic matter i.e. . The upper bound
obtained from the relic density is shown with the lower bound obtained from the
Raffelt's criterion on the emissibity rate of the supernovae SN1987A energy
loss and the optical depth criteria on the free
streaming of the dark matter fermion (produced inside the supernovae core). As
the deformation parameter changes from (undeformed scenario) to
(deformed scenario), the relic density bound on is found to vary
from TeV to TeV for a fermion dark
matter() of mass , which is almost times more
than the lower bound obtained from the SN1987A energy loss rate and the optical
depth criteria.
\noindent {{\bf Keywords}: Dark matter, Relic density, Supernova cooling,
Tsallis statistics, free-streaming, } }Comment: 18 Pages, 10 figure
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