Effective role of unpolarized nonvalence partons in Drell-Yan single spin asymmetries

We perform numerical simulations of the Sivers effect from single spin asymmetries in Drell-Yan processes on transversely polarized protons. We consider colliding antiprotons and pions at different kinematic conditions of interest for the future planned experiments. We conventionally name "framework I" the results obtained when properly accounting for the various flavor dependent polarized valence contributions in the numerator of the asymmetry, and for the unpolarized nonvalence contribution in its denominator. We name "framework II" the results obtained when taking a suitable flavor average of the valence contributions and neglecting the nonvalence ones. We compare the two methods, also with respect to the input parametrization of the Sivers function which is extracted from data with approximations sometimes intermediate between frameworks I and II. Deviations between the two approaches are found to be small except for dilepton masses below 3 GeV. The Sivers effect is used as a test case; the arguments can be generalized to other interesting azimuthal asymmetries in Drell-Yan processes, such as the Boer-Mulders effect.Comment: 13 pages, 9 figures in eps forma

Exploring the Partonic Structure of Hadrons through the Drell-Yan Process

The Drell-Yan process is a standard tool for probing the partonic structure of hadrons. Since the process proceeds through a quark-antiquark annihilation, Drell-Yan scattering possesses a unique ability to selectively probe sea distributions. This review examines the application of Drell-Yan scattering to elucidating the flavor asymmetry of the nucleon's sea and nuclear modifications to the sea quark distributions in unpolarized scattering. Polarized beams and targets add an exciting new dimension to Drell-Yan scattering. In particular, the two initial-state hadrons give Drell-Yan sensitivity to chirally-odd transversity distributions.Comment: 23 pages, 9 figures, to appear in J. Phys. G, resubmission corrects typographical error

Re-evaluation of the LHC potential for the measurement of Mw

We present a study of the LHC sensitivity to the W boson mass based on simulation studies. We find that both experimental and phenomenological sources of systematic uncertainties can be strongly constrained with Z measurements: the lineshape is robustly predicted, and its analysis provides an accurate measurement of the detector resolution and absolute scale, while the differential cross-section analysis absorbs most of the strong interaction uncertainties. A sensitivity \delta Mw \sim 7 \MeV for each decay channel (W --> e nu, W --> mu nu), and for an integrated luminosity of 10 fb-1, appears as a reasonable goal

Measurement of the light quark flavor asymmetry in the nucleon sea.

Fermilab experiment E866 has performed a precision measurement of the ratio of Drell-Yan yields from 800 GeV/c protons incident on deuterium and hydrogen targets. The measurement is used to determine the ratio of down antiquarks({bar d}) to up antiquarks({bar u}) in the proton over a broad range in the fraction of the proton momentum carried by the antiquark, 0.02 < x < 0.345. For x < 0.15, the data is in reasonable agreement with pre-existing parton distributions while for x > 0.20 the data is much closer to unity than these parton functions had indicated. The light quark asymmetry provides valuable information on the relative role perturbative and non-perturbative mechanisms play in generating the nucleon sea. A proposal to extend the Drell-Yan measurement to higher values of x using 120 GeV protons from the Fermilab main injector will be discussed