469,048 research outputs found
Can Polarised Drell-Yan Shed More Light On The Proton Spin?
We analyse polarised Drell-Yan process using the factorisation method and
derive operator definitions for polarised parton distribution functions. We
demonstrate that a factorisation analogous to that in the unpolarised Drell-Yan
case holds in this process. We study the leading order gluonic contribution to
the first moment of polarised Drell-Yan function and show that it is consistent
with results obtained from polarised deep inelastic scattering.Comment: 12 page
A study on the feasibility of a precise measurement of the -dependence of the cross sections for Drell-Yan experiments at moderate energies
Recently, a reconsideration of Drell-Yan cross sections at moderate energies
and masses has suggested the possibility of relevant enhancements of the cross
sections in some kinematical regions. If confirmed, these predictions could
largely affect the planning of Drell-Yan experiments aimed at transverse spin
measurements after 2010. More in general, the problem is present of a precision
measurement of the dependence of Drell-Yan cross sections. Here we
discuss the feasibility of such a measurement within short time at the COMPASS
apparatus, and its relevance for the PANDA experiment.Comment: 4 pages, 4 figures, in print on Physical Review
Ground state correlations in Deep Inelastic Scattering and the Drell-Yan process
Non-perturbative corrections to the LO cross section formulae for DIS and the
Drell-Yan process were calculated. The interaction of partons was taken into
account via dressing the incoming quark lines with spectral functions. We found
the effect of ground state correlation in DIS to be large in the region of
small Bjorken x and low momentum transfer Q. For a quark width of the order of
200 MeV, the deviation from parton model cross section reaches as much as 50%
for Q^2=10 GeV^2. On the other hand, for the values of Q well above the
resonance region, the effect of ISI turned out to be small in DIS, but still
substantial for the triple differential Drell-Yan cross section. Our
calculations show that the shape of the high mass Drell-Yan pair transverse
momentum distribution is fully determined by quark off-shellness. From
comparison to the resent data on the Drell-Yan cross section from NuSea
collaboration, we obtained for the quark width in the nucleon the value about
200 MeV.Comment: Talk presented on "IV international conference on Perspectives in
Hadronic Physics", to be published in the proceedings, 6 pages, 5 figures,
uses EPJ styl
Double Transverse-Spin Asymmetries in Drell-Yan Processes with Antiprotons
We present next-to-leading order predictions for double transverse-spin
asymmetries in Drell--Yan dilepton production initiated by proton--antiproton
scattering. The kinematic region of the proposed PAX experiment at GSI:
30\lesssim{s}\lesssim200\GeV^2 and 2\lesssim{M}\lesssim7\GeV is examined.
The Drell--Yan asymmetries turn out to be large, in the range 20--40%.
Measuring these asymmetries would provide the cleanest determination of the
quark transversity distributions.Comment: 11 pages, 7 figures, uses elsart and feynmp (included); one new
reference adde
Frame-Independence of Exclusive Amplitudes in the Light-Front Quantization
While the particle-number-conserving convolution formalism established in the
Drell-Yan-West reference frame is frequently used to compute exclusive
amplitudes in the light-front quantization, this formalism is limited to only
those frames where the light-front helicities are not changed and the good
(plus) component of the current remains unmixed. For an explicit demonstration
of such criteria, we present the relations between the current matrix elements
in the two typical reference frames used for calculations of the exclusive
amplitudes, i.e. the Drell-Yan-West and Breit frames and investigate both
pseudoscalar and vector electromagnetic currents in detail. We find that the
light-front helicities are unchanged and the good component of the current does
not mix with the other components of the current under the transformation
between these two frames. Thus, the pseudoscalar and vector form factors
obtained by the diagonal convolution formalism in both frames must indeed be
identical. However, such coincidence between the Drell-Yan-West and Breit
frames does not hold in general. We give an explicit example in which the
light-front helicities are changed and the plus component of the current is
mixed with other components under the change of reference frame. In such a
case, the relationship between the frames should be carefully analyzed before
the established convolution formalism in the Drell-Yan-West frame is used.Comment: 14 pages, 4 figure
The LHC can probe small x PDFs; the treatment of the infrared region
First, we show how to reduce the sensitivity of the NLO predictions of the
Drell-Yan production of low-mass, lepton-pairs, at high rapidity, to the choice
of factorization scale. In this way, observations of this process at the LHC
can make direct measurements of parton distribution functions in the low x
domain; x < 10^{-4}. Second, we find an inconsistency in the conventional NLO
treatment of the infrared region. We illustrate the problem using the NLO
coefficient function of Drell-Yan production.Comment: 5 pages, 1 figure, contribution to the Proceedings of
"Diffraction2012", Puerto del Carmen, Lanzarote, Spain, Sept. 10-15th, 201
Inclusive and differential W and Z at CMS and ATLAS
Several electroweak precision measurements are performed by the ATLAS and CMS
collaborations at the LHC. The main ones are carried out using Drell-Yan
production of single W and Z boson. They regard the measurement of the
production cross sections of W and Z bosons, the mass of the W boson, and
. The results of the measurements have an
accuracy of approximately twice that reached at LEP and SLD. Other measurements
reported are about the Drell-Yan differential production cross section.Comment: Contribution to the 2019 QCD session of the 54th Rencontres de
Morion
Energy Loss in Nuclear Drell-Yan Process
By means of the nuclear parton distributions which can be used to provide a
good explanation for the EMC effect in the whole x range, we investigate the
energy loss effect in nuclear Drell-Yan process. When the cross section of
lepton pair production is considered varying with the center-of-mass energy of
the nucleon-nucleon collision, we find that the nuclear Drell-Yan(DY) ratio is
suppressed due to the energy loss, which balances the overestimate of the DY
ratio only in consideration of the effect of nuclear parton distributions.Comment: 10 pages, LaTeX, 1 ps figures, To appear in Eur. Phys. J.
- …