23,769 research outputs found
A Consistent Calculation of Heavy Meson Decay Constants and Transition Wave Functions in the Complete HQEFT
Within the complete heavy quark effective field theory (HQEFT), the QCD sum
rule approach is used to evaluate the decay constants including 1/m_Q
corrections and the Isgur-Wise function and other additional important wave
functions concerned at 1/m_Q for the heavy-light mesons. The 1/m_Q corrections
to the scaling law f_M \sim F/\sqrt{m_M} are found to be small in HQEFT, which
demonstrates again the validity of 1/m_Q expansion in HQEFT. It is also shown
that the residual momentum v.k of heavy quark within hadrons does be around the
binding energy \bar{\Lambda} of the heavy hadrons. The calculations presented
in this paper provide a consistent check on the HQEFT and shows that the HQEFT
is more reliable than the usual HQET for describing a slightly off-mass shell
heavy quark within hadron as the usual HQET seems to lead to the breakdown of
1/m_Q expansion in evaluating the meson decay constants. It is emphasized that
the introduction of the `dressed heavy quark' mass is useful for the
heavy-light mesons (Qq) with m_Q >> \bar{\Lambda} >> m_q, while for heavy-heavy
bound states (\psi_1\psi_2) with masses m_1, m_2 >> \bar{\Lambda}, like
bottom-charm hadrons or similarly for muonium in QED, one needs to treat both
particles as heavy effective particles via 1/m_1 and 1/m_2 expansions and
redefine the effective bound states and modified `dressed heavy quark' masses
within the HQEFT.Comment: 20 pages, revtex, 22 figures, axodraw.sty, two irrelevant figures are
moved awa
Thermopower as a Possible Probe of Non-Abelian Quasiparticle Statistics in Fractional Quantum Hall Liquids
We show in this paper that thermopower is enhanced in non-Abelian quantum
Hall liquids under appropriate conditions. This is because thermopower measures
entropy per electron in the clean limit, while the degeneracy and entropy
associated with non-Abelian quasiparticles enhance entropy when they are
present. Thus thermopower can potentially probe non-Abelian nature of the
quasiparticles, and measure their quantum dimension.Comment: 5 pages. Minor revisions in response to referee comments. Published
versio
Contribution of Twist-3 Multi-Gluon Correlation Functions to Single Spin Asymmetry in Semi-Inclusive Deep Inelastic Scattering
As a possible source of the single transverse spin asymmetry, we study the
contribution from purely gluonic correlation represented by the twist-3
``three-gluon correlation" functions in the transversely polarized nucleon. We
first define a complete set of the relevant three-gluon correlation functions,
and then derive its contribution to the twist-3 single-spin-dependent cross
section for the -meson production in semi-inclusive deep inelastic
scattering, which is relevant to determine the three-gluon correlations. Our
cross-section formula differs from the corresponding result in the literature,
and the origin of the discrepancy is clarified.Comment: 29 pages, 3 figures minor corrections; version to appear in Phys.
Rev.
Modeling the Parker instability in a rotating plasma screw pinch
We analytically and numerically study the analogue of the Parker (magnetic
buoyancy) instability in a uniformly rotating plasma screw pinch confined in a
cylinder. Uniform plasma rotation is imposed to create a centrifugal
acceleration, which mimics the gravity required for the classical Parker
instability. The goal of this study is to determine how the Parker instability
could be unambiguously identified in a weakly magnetized, rapidly rotating
screw pinch, in which the rotation provides an effective gravity and a radially
varying azimuthal field is controlled to give conditions for which the plasma
is magnetically buoyant to inward motion. We show that an axial magnetic field
is also required to circumvent conventional current driven magnetohydrodynamic
(MHD) instabilities such as the sausage and kink modes that would obscure the
Parker instability. These conditions can be realized in the Madison Plasma
Couette Experiment (MPCX). Simulations are performed using the extended MHD
code NIMROD for an isothermal compressible plasma model. Both linear and
nonlinear regimes of the instability are studied, and the results obtained for
the linear regime are compared with analytical results from a slab geometry.
Based on this comparison, it is found that in a cylindrical pinch the magnetic
buoyancy mechanism dominates at relatively large Mach numbers (M>5), while at
low Mach numbers (M<1) the instability is due to the curvature of magnetic
field lines. At intermediate values of Mach number (1<M<5) the Coriolis force
has a strong stabilizing effect on the plasma. A possible scenario for
experimental demonstration of the Parker instability in MPCX is discussed
Strong Color Field Baryonic Remnants in Nucleus-Nucleus Collisions at 200A GeV
The effects of strong color electric fields (SCF) on the baryon production at
RHIC are studied in the framework of HIJING/B\=B (v2.0) model. The particle
species dependence of nuclear modification factors (NMF) are analyzed for Au+Au
collisions at 200A GeV. A doubling of the string tension leading to a
modification of the strangeness suppression according to Schwinger mechanism is
shown to provide an alternate explanation to coalescence models for the
interpretation of the observed baryon and meson production at moderate
and results in a predicted enhancement in the (multi)strange (anti)hyperon
production.Comment: 6 pages, Latex(Revtex), 4 figures;Added new references, one figure,
text slightly modified. final version accepted for publication in Pnys. Rev.
C (october,05
Elastic and scattering in the models of unitarized pomeron
Elastic scattering amplitudes dominated by the Pomeron singularity which obey
the principal unitarity bounds at high energies are constructed and analyzed.
Confronting the models of double and triple (at ) Pomeron pole
(supplemented by some terms responsible for the low energy behaviour) with
existing experimental data on and total and differential cross
sections at GeV and GeV we are able to tune
the form of the Pomeron singularity. Actually the good agreement with those
data is received for both models though the behaviour given by the dipole model
is more preferable in some aspects. The predictions made for the LHC energy
values display, however, the quite noticeable difference between the
predictions of models at GeV. Apparently the future
results of TOTEM will be more conclusive to make a true choice.Comment: Revtex4, 8 pages, 5 figures. Text is improved, no changes in figures
and conclusions. Version to be published in Phys. Rev.
Modeling the tensile strains of non-uniform fibers
The maximum strain experienced by the thinnest segment of a non-uniform fiber governs fiber breakage, yet this maximum strain can not be obtained from a normal single fiber test. Only the average strain of the whole fiber specimen can be obtained from a normal single fiber tensile test. This study has examined the relationship between the average strain, the maximum strain and the degree of fiber non-uniformity, expressed in coefficient of variation (CV) of fiber diameters along fiber length. The tensile strain of irregular fibers has been simulated using the finite element method (FEM). Using this method, average and maximum tensile strains of non-uniform fibers were calculated. The results indicate that for irregular fibers such as wool, there is an exponential relationship (i.e.É› ave É› max=ae −b CV ) between the ratio of average breaking strain and maximum breaking strain (É› ave É› max) and the along-fiber diameter variation (CV). The strain ratio decreases with the increase of the along-fiber diameter variation. <br /
Evaporative CO2 cooling using microchannels etched in silicon for the future LHCb vertex detector
The extreme radiation dose received by vertex detectors at the Large Hadron
Collider dictates stringent requirements on their cooling systems. To be robust
against radiation damage, sensors should be maintained below -20 degree C and
at the same time, the considerable heat load generated in the readout chips and
the sensors must be removed. Evaporative CO2 cooling using microchannels etched
in a silicon plane in thermal contact with the readout chips is an attractive
option. In this paper, we present the first results of microchannel prototypes
with circulating, two-phase CO2 and compare them to simulations. We also
discuss a practical design of upgraded VELO detector for the LHCb experiment
employing this approach.Comment: 12 page
Implementing the Five-A Model of technical refinement: Key roles of the sport psychologist
There is increasing evidence for the significant contribution provided by sport psychologists within applied coaching environments. However, this rarely considers their skills/knowledge being applied when refining athletes’ already learned and well-established motor skills. Therefore, this paper focuses on how a sport psychologist might assist a coach and athlete to implement long-term permanent and pressure proof refinements. It highlights key contributions at each stage of the Five-A Model—designed to deliver these important outcomes—providing both psychomotor and psychosocial input to the support delivery. By employing these recommendations, sport psychologists can make multiple positive contributions to completion of this challenging task
Collinear Factorization for Single Transverse-Spin Asymmetry in Drell-Yan Processes
We study the scattering of a single parton state with a multi-parton state to
derive the complete results of perturbative coefficient functions at leading
order, which appear in the collinear factorization for Single transverse-Spin
Asymmetry(SSA) in Drell-Yan processes with a transversely polarized hadron in
the initial state. We find that the factorization formula of SSA contains
hard-pole-, soft-quark-pole- and soft-gluon-pole contributions. It is
interesting to note that the leading order perturbative coefficient functions
of soft-quark-pole- and soft-gluon-pole contributions are extracted from parton
scattering amplitudes at one-loop, while the functions of hard-pole
contributions are extracted from the tree level amplitudes at tree-level. Our
method to derive the factorization of SSA is different than the existing one in
literature. A comparison of our results with those obtained by other method is
made.Comment: 27 pages, 14 figures, text improved, to appear in Phys. Rev.
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