23,174 research outputs found
Present status on experimental search for pentaquarks
It has been ten years since the first report for a positive strangeness
pentaquark-like baryon state. However the existence of the pentaquark state is
still controversial. Some contradictions between the experiments are unsolved.
In this paper we review the experimental search for the pentaquark candidates
, , , and in details. We
review the experiments with positive results and compare the experiments with
similar conditions but opposite results.Comment: 20 latex pages, 2 figures, to appear in IJMPA as a revie
Transverse single-spin asymmetries of pion production in semi-inclusive DIS at subleading twist
We study the single-spin asymmetries with the and angular dependences for charged and neutral pions produced in
semi-inclusive deep inelastic scattering on the transversely polarized proton
target. The theoretical interpretations of the two asymmetries are presented in
terms of the convolution of the twist-3 quark transverse momentum dependent
distributions and twist-2 fragmentation functions. Specifically, we investigate
the role of the distributions , and in the
asymmetry, as well as the role of the distributions , and
in the asymmetry. We calculate these
distributions in a spectator-diquark model and predict the corresponding
asymmetries for the first time, considering the kinematics at HERMES, JLab and
COMPASS. The numerical estimates show that the asymmetries are sizable, and the
dominant contribution to the asymmetry comes from the T-odd
distribution , while gives the main contribution to the
asymmetry. The future measurements on these asymmetries
can shed light on the information of twist-3 transverse momentum dependent
distributions.Comment: 11 pages, 12 figures, version published in PR
On Optimal Service Differentiation in Congested Network Markets
As Internet applications have become more diverse in recent years, users
having heavy demand for online video services are more willing to pay higher
prices for better services than light users that mainly use e-mails and instant
messages. This encourages the Internet Service Providers (ISPs) to explore
service differentiations so as to optimize their profits and allocation of
network resources. Much prior work has focused on the viability of network
service differentiation by comparing with the case of a single-class service.
However, the optimal service differentiation for an ISP subject to resource
constraints has remained unsolved. In this work, we establish an optimal
control framework to derive the analytical solution to an ISP's optimal service
differentiation, i.e. the optimal service qualities and associated prices. By
analyzing the structures of the solution, we reveal how an ISP should adjust
the service qualities and prices in order to meet varying capacity constraints
and users' characteristics. We also obtain the conditions under which ISPs have
strong incentives to implement service differentiation and whether regulators
should encourage such practices
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