180,895 research outputs found
QCD Factorization for Quarkonium Production in Hadron Collions at Low Transverse Momentum
Inclusive production of a quarkonium in hadron collisions at low
transverse momentum can be used to extract various
Transverse-Momentum-Dependent(TMD) gluon distributions of hadrons, provided the
TMD factorization for the process holds. The factorization involving
unpolarized TMD gluon distributions of unpolarized hadrons has been examined
with on-shell gluons at one-loop level. In this work we study the factorization
at one-loop level with diagram approach in the most general case, where all TMD
gluon distributions at leading twist are involved. We find that the
factorization holds and the perturbative effects are represented by one
perturbative coefficient. Since the initial gluons from hadrons are off-shell
in general, there exists the so-called super-leading region found recently. We
find that the contributions from this region can come from individual diagrams
at one-loop level, but they are cancelled in the sum. Our factorized result for
the differential cross-section is explicitly gauge-invariant.Comment: discussions and references are added. Published version on Phys. Rev.
Quantum sensing of rotation velocity based on transverse field Ising model
We study a transverse-field Ising model (TFIM) in a rotational reference
frame. We find that the effective Hamiltonian of the TFIM of this system
depends on the system's rotation velocity. Since the rotation contributes an
additional transverse field, the dynamics of TFIM sensitively responses to the
rotation velocity at the critical point of quantum phase transition. This
observation means that the TFIM can be used for quantum sensing of rotation
velocity that can sensitively detect rotation velocity of the total system at
the critical point. It is found that the resolution of the quantum sensing
scheme we proposed is characterized by the half-width of Loschmidt echo of the
dynamics of TFIM when it couples to a quantum system S. And the resolution of
this quantum sensing scheme is proportional to the coupling strength \delta
between the quantum system S and the TFIM, and to the square root of the number
of spins N belonging the TFIM.Comment: 6 pages,6 figure
A Study of Gluon Propagator on Coarse Lattice
We study gluon propagator in Landau gauge with lattice QCD, where we use an
improved lattice action. The calculation of gluon propagator is performed on
lattices with the lattice spacing from 0.40 fm to 0.24 fm and with the lattice
volume from to . We try to fit our results by two
different ways, in the first one we interpret the calculated gluon propagators
as a function of the continuum momentum, while in the second we interpret the
propagators as a function of the lattice momentum. In the both we use models
which are the same in continuum limit. A qualitative agreement between two
fittings is found.Comment: Revtex 14pages, 11 figure
Transverse-Momentum Dependent Factorization for gamma^* pi^0 to gamma
With a consistent definition of transverse-momentum dependent (TMD)
light-cone wave function, we show that the amplitude for the process can be factorized when the virtuality of the initial photon is
large. In contrast to the collinear factorization in which the amplitude is
factorized as a convolution of the standard light-cone wave function and a hard
part, the TMD factorization yields a convolution of a TMD light-cone wave
function, a soft factor and a hard part. We explicitly show that the TMD
factorization holds at one loop level. It is expected that the factorization
holds beyond one-loop level because the cancelation of soft divergences is on a
diagram-by-diagram basis. We also show that the TMD factorization helps to
resum large logarithms of type .Comment: Published version in Phys.Rev.D75:014014,200
Gluon GPDs and Exclusive Photoproduction of a Quarkonium in Forward Region
Forward photoproduction of can be used to extract Generalized Parton
Distributions(GPD's) of gluons. We analyze the process at twist-3 level and
study relevant classifications of twist-3 gluon GPD's. At leading power or
twist-2 level the produced is transversely polarized. We find that at
twist-3 the produced is longitudinally polarized. Our study shows that
in high energy limit the twist-3 amplitude is only suppressed by the inverse
power of the heavy quark mass relatively to the twist-2 amplitude. This
indicates that the power correction to the cross-section of unpolarized
can have a sizeable effect. We have also derived the amplitude of the
production of at twist-3, but the result contains end-point
singularities. The production of other quarkonia has been briefly discussed.Comment: Discussions of results are adde
Shifting with
Precision measurements at the resonance agree well with the standard
model. However, there is still a hint of a discrepancy, not so much in by
itself (which has received a great deal of attention in the past several years)
but in the forward-backward asymmetry together with . The two
are of course correlated. We explore the possibilty that these and other
effects are due to the mixing of and with one or more heavy quarks.Comment: 11 pages, 1 Figure, LaTex fil
Mark 3 interactive data analysis system
The interactive data analysis system, a major subset of the total Mark 3 very long baseline interferometry (VLBI) software system is described. The system consists of two major and a number of small programs. These programs provide for the scientific analysis of the observed values of delay and delay rate generated by the VLBI data reduction programs and product the geophysical and astrometric parameters which are among the ultimate products of VLBI. The two major programs are CALC and SOLVE. CALC generates the theoretical values of VLBI delay rate as well as partial derivatives based on apriori values of the geophysical and astronometric parameters. SOLVE is a least squares parameters estimation program which yields the geophysical and astrometric parameters using the observed values by the data processing system and theoretical values and partial derivatives provided by CALC. SOLVE is a highly interactive program in which the user selects the exact form of the recovered parameters and the data to be accepted into the solution
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