119 research outputs found
Wigner Distributions Using Light-Front Wave Functions
We report on some recent advances in calculating the Wigner distributions for
quarks and gluons, using overlaps of light-front wave functions.Comment: Talk given at the QCD Evolution Workshop, May 22-26, 2017, Jefferson
Lab, US
Diffraction Patterns in Deeply Virtual Compton Scattering
We report on a calculation to show that the Fourier transform of the Deeply
Virtual Compton Scattering (DVCS) amplitude with respect to the skewness
variable \zeta at fixed invariant momentum transfer squared t gives results
that are analogous to the diffractive scattering of a wave in optics. As a
specific example, we utilize the quantum fluctuations of a fermion state at one
loop in QED to obtain the behavior of the DVCS amplitude for electron-photon
scattering. We then simulate the wavefunctions for a hadron by differentiating
the above LFWFs with respect to M^2 and study the corresponding DVCS amplitudes
in light-front longitudinal space.Comment: Presented at the 17 th International Spin Physics Symposium, Kyoto,
Japan, October 2-7, 200
Jet Production in Collisions: Dependence on Jet Algorithm
We report on a recent calculation of single-inclusive high- jet
production in unpolarized and longitudinally polarized collisions at RHIC,
investigating the effect of the algorithm adopted to define the jets on the
numerical results for cross sections and spin asymmetries.Comment: Prepared for the Third Workshop on the QCD Structure of the Nucleon :
QCD N'12, 22-26 October, 2012, Bilbao, Spai
Linearly polarized gluons in charmonium and bottomonium production in color octet model
We study the possibility to probe the unpolarized and linearly polarized
transverse momentum- dependent gluon distributions in unpolarized pp collision
in charmonium and bottomonium produc- tion, employing non-relativistic QCD
(NRQCD) based color octet model within transverse momentum dependent (TMD)
factorization framework. The transverse momentum (p T ) and rapidity
distributions of J/{\psi} and {\Upsilon}(1S) at LHCb, RHIC and AFTER energies
are estimated. Significant modulations in transverse momentum spectrum of
quarkonium in the low p T region is obtained when contributions of linearly
polarized gluons inside an unpolarized proton are taken into account. The
results of quarko- nium production in color octet model and color evaporation
model are compared.Comment: Replaced with the revised version, to appear in PR
Production in Polarized and Unpolarized Collision and Sivers and Asymmetries
We calculate the Sivers and azimuthal asymmetries in
production in polarized and unpolarized semi-inclusive collision
respectively, using the formalism based on transverse momentum dependent parton
distributions (TMDs). Non-relativistic QCD based color octet model is employed
for calculating the production rate. The Sivers asymmetry in this
process directly probes the gluon Sivers function. The estimated Sivers
asymmetry at is negative which is in good agreement with COMPASS data. We
also investigate the effect of TMD evolution on the Sivers asymmetry. The
asymmetry is sizable and probes the linearly polarized gluon
distribution in an unpolarized proton.Comment: 29 pages, 11 figures. Details of calculation adde
Jet production in (un)polarized pp collisions: dependence on jet algorithm
We investigate single-inclusive high-pT jet production in longitudinally
polarized pp collisions at RHIC, with particular focus on the algorithm adopted
to define the jets. Following and extending earlier work in the literature, we
treat the jets in the approximation that they are rather narrow, in which case
analytical results for the corresponding next-to-leading order partonic cross
sections can be obtained. This approximation is demonstrated to be very
accurate for practically all relevant situations, even at Tevatron and LHC
energies. We confront results for cross sections and spin-asymmetries based on
using cone- and kt-type jet algorithms. We find that jet cross sections at RHIC
can differ significantly depending on the algorithm chosen, but that the spin
asymmetries are rather robust. Our results are also useful for matching
threshold-resummed calculations of jet cross sections to fixed-order ones.Comment: 11 pages, 7 figure
Accessing Linearly Polarized Gluon Distribution in Production at the Electron-Ion Collider
We calculate the asymmetry in production in
electron-proton collision for the kinematics of the planned electron-ion
collider (EIC). This directly probes the Weisz\"acker-Williams (WW) type
linearly polarized gluon distribution. Assuming generalized factorization, we
calculate the asymmetry at next-to-leading-order (NLO) when the energy fraction
of the satisfies and the dominating subprocess is . We use non-relativistic QCD based color singlet
model for production. We investigate the small region which will
be accessible at the EIC. We present the upper bound of the asymmetry, as well
as estimate it using a (i) Gaussian type parametrization for the TMDs and (ii)
McLerran-Venugopalan model at small . We find small but sizable asymmetry in
all the three cases.Comment: Version to appear in Phys. Rev.
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