251,313 research outputs found
Partonic State and Single Transverse Spin Asymmetry in Drell-Yan Process
Single transverse-spin asymmetries have been studied intensively both in
experiment and theory. Theoretically, two factorization approaches have been
proposed. One is by using transverse-momentum-dependent factorization and the
asymmetry comes from the so called Sivers function. Another is by using
collinear factorization where the nonperturbative effect is parameterized by a
twist-3 hadronic matrix element. However, the factorized formulas for the
asymmetries in the two approaches are derived at hadron level formally by
diagram expansion, where one works with various parton density matrices of
hadrons. If the two factorizations hold, they should also hold at parton level.
We examine this for Drell-Yan processes by replacing hadrons with partons. By
calculating the asymmetry, Sivers function and the twist-3 matrix element at
nontrivial leading order of , we find that we can reproduce the
result of the transverse-momentum-dependent factorization. But we can only
verify the result of the collinear factorization partly. Two formally derived
relations between Sivers function and the twist-3 matrix element are also
examined with negative results.Comment: 15 pages, 6 figure
Numerical analysis of a downsized 2-stroke uniflow engine
In order to optimize the 2-stroke uniflow engine performance on vehicle applications, numerical analysis has been introduced, 3D CFD model has been built for the optimization of intake charge organization. The scavenging process was investigated and the intake port design details were improved. Then the output data from 3D CFD calculation were applied to a 1D engine model to process the analysis on engine performance. The boost system optimization of the engine has been carried out also. Furthermore, a vehicle model was also set up to investigate the engine in-vehicle performance
The evolution-dominated hydrodynamic model and the pseudorapidity distributions in high energy physics
By taking into account the effects of leading particles, we discuss the
pseudorapidity distributions of the charged particles produced in high energy
heavy ion collisions in the context of evolution-dominated hydrodynamic model.
The leading particles are supposed to have a Gaussian rapidity distribution
normalized to the number of participants. A comparison is made between the
theoretical results and the experimental measurements performed by BRAHMS and
PHOBOS Collaboration at BNL-RHIC in Au-Au and Cu-Cu collisions at sqrt(s_NN)
=200 GeV and by ALICE Collaboration at CERN-LHC in Pb-Pb collisions at
sqrt(s_NN) =2.76 TeV.Comment: 17 pages,4 figures, 2 table
Baryon and Lepton Number Violation with Scalar Bilinears
We consider all possible scalar bilinears, which couple to two fermions of
the standard model. The various baryon and lepton number violating couplings
allowed by these exotic scalars are studied. We then discuss which ones are
constrained by limits on proton decay (to a lepton and a meson as well as to
three leptons), neutron-antineutron oscillations, and neutrinoless double beta
decay.Comment: 11 pages latex fil
Criticality and Continuity of Explosive Site Percolation in Random Networks
This Letter studies the critical point as well as the discontinuity of a
class of explosive site percolation in Erd\"{o}s and R\'{e}nyi (ER) random
network. The class of the percolation is implemented by introducing a best-of-m
rule. Two major results are found: i). For any specific , the critical
percolation point scales with the average degree of the network while its
exponent associated with is bounded by -1 and . ii).
Discontinuous percolation could occur on sparse networks if and only if
approaches infinite. These results not only generalize some conclusions of
ordinary percolation but also provide new insights to the network robustness.Comment: 5 pages, 5 figure
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