20,073 research outputs found
The electromagnetic decays of the charmed and bottom baryons in chiral perturbation theory
We have investigated the electromagnetic decays of the antitriplet and sextet
charmed baryon systems with in the
framework of the heavy baryon chiral perturbation theory. We first construct
the chiral Lagrangians at and . Then we calculate the
electromagnetic (EM) decay amplitudes of the charmed baryon systems up to
. With the help of the quark model, we estimate the low energy
constants. The numerical results of the EM decay widths show good convergence
of the chiral expansion. We notice that the two neutral EM decay processes
and
are strongly suppressed by the SU(3) U-spin flavor symmetry. With the same
formalism, we also estimate the EM decay widths of the bottomed baryons. The EM
decay widths of the heavy baryons may be measured at facilities such as LHCb
and JPARC. The explicit chiral structures of the heavy baryon decay amplitudes
derived in this work may be useful to the possible chiral extrapolations of the
future lattice simulations of these EM decay amplitudes
General stationary charged black holes as charged particle accelerators
We study the possibility of getting infinite energy in the center of mass
frame of colliding charged particles in a general stationary charged black
hole. For black holes with two-fold degenerate horizon, it is found that
arbitrary high center-of-mass energy can be attained, provided that one of the
particle has critical angular momentum or critical charge, and the remained
parameters of particles and black holes satisfy certain restriction. For black
holes with multiple-fold degenerate event horizons, the restriction is
released. For non-degenerate black holes, the ultra-high center-of-mass is
possible to be reached by invoking the multiple scattering mechanism. We obtain
a condition for the existence of innermost stable circular orbit with critical
angular momentum or charge on any-fold degenerate horizons, which is essential
to get ultra-high center-of-mass energy without fine-tuning problem. We also
discuss the proper time spending by the particle to reach the horizon and the
duality between frame dragging effect and electromagnetic interaction. Some of
these general results are applied to braneworld small black holes.Comment: 23 pages, no figures, revised version accepted for publication in
Phys. Rev.
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