20,411 research outputs found
A Collider for the 750 GeV Resonant State
Recent data collected by ATLAS and CMS at 13 TeV collision energy of the LHC
indicate the existence of a new resonant state with a mass of 750 GeV
decaying into two photons . The properties of should be
studied further at the LHC and also future colliders. Since only decay channel has been measured, one of the best ways to extract
more information about is to use a collider to produce
at the resonant energy. In this work we show how a
collider helps to verify the existence of and to provide some of the
most important information about the properties of , such as branching
fractions of . Here can be , , or . We
also show that by studying angular distributions of the final 's in
, one can obtain crucial information
about whether this state is a spin-0 or a spin-2 state.Comment: ReTex, 12 page with 6 figures. Expanded discussion on distinguishing
spin-0 and spin-2 cases. Several figures adde
Heavy Quarkonium Dissociation by Thermal Gluons at Next-to-leading Order in the Quark-Gluon Plasma
Using the chromo-electric dipole coupling Hamiltonian from QCD multipole
expansion, we derive the dissociation cross sections of heavy quarkonia by
thermal gluons at next-to-leading order (NLO, also known as inelastic parton
scattering dissociation) in the Quark-Gluon Plasma (QGP) in the framework of
second order quantum mechanical perturbation theory. While suffering divergence
(infrared and soft-collinear divergences) in vacuum, the cross sections thus
derived become finite in the QGP as rendered by the finite thermal gluon
masses. In contrast to the leading order (LO, also known as gluo-dissociation)
counterparts rapidly dropping off with increasing incident gluon energy, the
NLO cross sections exhibits finite value toward high energies because of new
phase space being opened up. We then carry out a full calculation of the
dissociation rates for various charmonia and bottomonia within a
non-relativistic in-medium potential model. The NLO process is shown to
dominate the dissociation rate toward high temperatures when the binding
energies of heavy quarkonia become smaller relative to the Debye screening
mass.Comment: 11 pages, 6 figures; version accepted for publication in Phys. Lett.
Some Predictions of Diquark Model for Hidden Charm Pentaquark Discovered at the LHCb
The LHCb has discovered two new states with preferred quantum numbers
and from decays. These new states can be
interpreted as hidden charm pentaquarks. It has been argued that the main
features of these pentaquarks can be described by diquark model. The diquark
model predicts that the and are in two separate octet
multiplets of flavor and there is also an additional decuplet
pentaquark multiplet. Finding the states in these multiplets can provide
crucial evidence for this model. The weak decays of b-baryon to a light meson
and a pentaquark can have Cabibbo allowed and suppressed decay channels. We
find that in the limit, for -spin related decay modes the ratio of
the decay rates of Cabibbo suppressed to Cabibbo allowed decay channels is
given by . There are also other testable relations for
b-baryon weak decays into a pentaquark and a light pseudoscalar. These
relations can be used as tests for the diquark model for pentaquark.Comment: revtex, 19 pages, 3 figures. one reference added and some typos
correcte
Statistical computation of Boltzmann entropy and estimation of the optimal probability density function from statistical sample
In this work, we investigate the statistical computation of the Boltzmann
entropy of statistical samples. For this purpose, we use both histogram and
kernel function to estimate the probability density function of statistical
samples. We find that, due to coarse-graining, the entropy is a monotonic
increasing function of the bin width for histogram or bandwidth for kernel
estimation, which seems to be difficult to select an optimal bin
width/bandwidth for computing the entropy. Fortunately, we notice that there
exists a minimum of the first derivative of entropy for both histogram and
kernel estimation, and this minimum point of the first derivative
asymptotically points to the optimal bin width or bandwidth. We have verified
these findings by large amounts of numerical experiments. Hence, we suggest
that the minimum of the first derivative of entropy be used as a selector for
the optimal bin width or bandwidth of density estimation. Moreover, the optimal
bandwidth selected by the minimum of the first derivative of entropy is purely
data-based, independent of the unknown underlying probability density
distribution, which is obviously superior to the existing estimators. Our
results are not restricted to one-dimensional, but can also be extended to
multivariate cases. It should be emphasized, however, that we do not provide a
robust mathematical proof of these findings, and we leave these issues with
those who are interested in them.Comment: 8 pages, 6 figures, MNRAS, in the pres
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