12,178 research outputs found
Photoproduction of in NRQCD
We present a calculation for the photoproduction of under the
framework of NRQCD factorization formalism. We find a quite unique feature that
the color-singlet contribution to this process vanishes at not only the leading
order but also the next to leading order perturbative QCD calculations and that
the dominant contribution comes from the color-octet
subprocess. The nonperturbative color-octet matrix element of
of is related to that of of by the heavy
quark spin symmetry, and the latter can be determined from the direct
production of at large transverse momentum at the Fermilib Tevatron.
We then conclude that the measurement of this process may clarify the existing
conflict between the color-octet prediction and the experimental result on the
photoprodution.Comment: 11 pages, revtex, 4 ps figure
Discovery and Identification of W' and Z' in SU(2) x SU(2) x U(1) Models at the LHC
We explore the discovery potential of W' and Z' boson searches for various
SU(2) x SU(2) x U(1) models at the Large Hadron Collider (LHC), after taking
into account the constraints from low energy precision measurements and direct
searches at both the Tevatron (1.96 TeV) and the LHC (7 TeV). In such models,
the W' and Z' bosons emerge after the electroweak symmetry is spontaneously
broken. Two patterns of the symmetry breaking are considered in this work: one
is SU(2)_L x SU(2)_2 x U(1)_X to SU(2)_L x U(1)_Y (BP-I), another is SU(2)_1 x
SU(2)_2 x U(1)_Y to SU(2)_L x U(1)_Y (BP-II). Examining the single production
channel of W' and Z' with their subsequent leptonic decays, we find that the
probability of detecting W' and Z' bosons in the considered models at the LHC
(with 14 TeV) is highly limited by the low energy precision data constraints.
We show that observing Z' alone, without seeing a W', does not rule out new
physics models with non-Abelian gauge extension, such as the phobic models in
BP-I. Models in BP-II would predict the discovery of degenerate W' and Z'
bosons at the LHC.Comment: 29 pages, including 11 figures, 3 tables, added references for
introductio
Why some online product reviews have no usefulness rating?
Combining econometric analysis with text mining techniques, this study attempts to explore why some online product reviews have no usefulness rating through examining review posting time and text features. Later posting time may reduce the probability of some online reviews being seen and thus lead to their being not rated for usefulness. Besides, the neutral diagnosticity of reviews reflected from the text features may cause difficulty for readers to judge and evaluate the usefulness of these reviews. Our study finds that, though not being seen due to later posting time obviously explains no usefulness rating for some online reviews, the neutral diagnosticity of these reviews is also an important and non-neglectable cause for their having no usefulness rating. Further, we identify the text features which may lead to the neutral diagnosticity of the review. Our study has implications for online product reviews website managers in identifying and dismissing the reviews with no usefulness rating to improve readers’ information retrieving efficiency and also for reviewers in improving the diagnosticity of their reviews
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