Monday, May 27, 2013

1305.5677 (M. Brandt et al.)

Parton densities from LHC vector boson production at small and large
transverse momenta

M. Brandt, M. Klasen
The parton densities of the proton are of fundamental importance not only for our description of hadronic and nuclear structure, but also for reliable predictions for new heavy particle searches at colliders. At the large partonic momentum fractions required for the production of these particles, the parton distribution functions, in particular the one of the gluon, are unfortunately still badly constrained. In this paper, we investigate the possibility to improve on their determination with new data coming from electroweak vector boson production at large transverse momenta at the LHC with center-of-mass energies of 7, 8 or 14 TeV. We demonstrate that this process is dominated by quark-gluon scattering, that theoretical predictions can be reliably made on the basis of next-to-leading order perturbation theory and its resummation, and that these data should thus be used in global fits. We also point out that the non-perturbative parameters determined from Tevatron run-1 Z-boson data at low p_T describe very well the new LHC data at \sqrt{s}=7 TeV.
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