4,455 research outputs found
Determinations of form factors for semileptonic decays and leptoquark constraints
By analyzing all existing measurements for ( ) decays, we find that the determinations of both the vector
form factor and scalar form factor for semileptonic
decays from these measurements are feasible. By taking the
parameterization of the one order series expansion of the and
, is determined to be , and the
shape parameters of and are
and , respectively. Combining with the average
of and lattice calculaltion, the is extracted
to be where the first error is experimental and the
second theoretical. Alternatively, the is extracted to be
by taking the as the value from the global
fit with the unitarity constraint of the CKM matrix. Moreover, using the
obtained form factors by lattice QCD, we re-analyze these
measurements in the context of new physics. Constraints on scalar leptoquarks
are obtained for different final states of semileptonic
decays
Systematic analysis of the incoming quark energy loss in cold nuclear matter
The investigation into the fast parton energy loss in cold nuclear matter is
crucial for a good understanding of the parton propagation in hot-dense medium.
By means of four typical sets of nuclear parton distributions and three
parametrizations of quark energy loss, the parameter values in quark energy
loss expressions are determined from a leading order statistical analysis of
the existing experimental data on nuclear Drell-Yan differential cross section
ratio as a function of the quark momentum fraction. It is found that with
independence on the nuclear modification of parton distributions, the available
experimental data from lower incident beam energy rule out the incident-parton
momentum fraction quark energy loss. Whether the quark energy loss is linear or
quadratic with the path length is not discriminated. The global fit of all
selected data gives the quark energy loss per unit path length {\alpha} =
1.21\pm0.09 GeV/fm by using nuclear parton distribution functions determined
only by means of the world data on nuclear structure function. Our result does
not support the theoretical prediction: the energy loss of an outgoing quark is
three times larger than that of an incoming quark approaching the nuclear
medium. It is desirable that the present work can provide useful reference for
the Fermilab E906/SeaQuest experiment
Clapeyron equation and phase equilibrium properties in higher dimensional charged topological dilaton AdS black holes with a nonlinear source
Using Maxwell's equal area law, we discuss the phase transition of higher
dimensional charged topological dilaton AdS black holes with a nonlinear
source. The coexisting region of the two phases is found and we depict the
coexistence region in diagrams. The two-phase equilibrium curves in
diagrams are plotted, and we take the first order approximation of volume
in the calculation. To better compare with a general thermodynamic system, the
Clapeyron equation is derived for higher dimensional charged topological black
hole with a nonlinear source. The latent heat of isothermal phase transition is
investigated. We also study the effect of the parameters of the black hole on
the region of two-phases coexistence. The results show that the black hole may
go through a small-large phase transition similar to those of usual non-gravity
thermodynamic systems.Comment: 21 pages,25 figures. published version in EPJC. arXiv admin note:
substantial text overlap with arXiv:1411.7202; text overlap with
arXiv:1506.01786, arXiv:hep-th/0605042 by other author
Thermodynamics of phase transition in higher dimensional Reissner-Nordstr\"{o}m-de Sitter black hole
It is well known that there are black hole and the cosmological horizons for
the Reissner-Nordstr\"{o}m-de Sitter spacetime. Although the thermodynamic
quantities on the horizons are not irrelevant, they satisfy the laws of black
hole thermodynamics respectively. In this paper by considering the relations
between the two horizons we give the effective thermodynamic quantities in
-dimensional Reissner-Nordstr\"{o}m-de Sitter spacetime. The
thermodynamic properties of these effective quantities are analyzed, moreover,
the critical temperature, critical pressure and critical volume are obtained.
We carry out an analytical check of Ehrenfest equations and prove that both
Ehrenfest equations are satisfied. So the spacetime undergoes a second order
phase transition at the critical point. This result is consistent with the
nature of liquid--gas phase transition at the critical point, hence deepening
the understanding of the analogy of charged dS spacetime and liquid--gas
systems.Comment: 18 pages, 7 figures, 1 tabl
Nuclear geometry effect and transport coefficient in semi-inclusive lepton-production of hadrons off nuclei
Hadron production in semi-inclusive deep-inelastic scattering of leptons from
nuclei is an ideal tool to determine and constrain the transport coefficient in
cold nuclear matter. The leading-order computations for hadron multiplicity
ratios are performed by means of the SW quenching weights and the analytic
parameterizations of quenching weights based on BDMPS formalism. The
theoretical results are compared to the HERMES positively charged pions
production data with the quarks hadronization occurring outside the nucleus.
With considering the nuclear geometry effect on hadron production, our
predictions are in good agreement with the experimental measurements. The
extracted transport parameter from the global fit is shown to be for the SW quenching weight without the finite energy
corrections. As for the analytic parameterization of BDMPS quenching weight
without the quark energy E dependence, the computed transport coefficient is
. It is found that the nuclear geometry effect
has a significant impact on the transport coefficient in cold nuclear matter.
It is necessary to consider the detailed nuclear geometry in studying the
semi-inclusive hadron production in deep inelastic scattering on nuclear
targets.Comment: 14 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1310.569
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