338 research outputs found
Near Future Perpectives of QCD Spin Studies
We consider the physics motivations and perspectives for the study of spin
phenomena at the future high energies accelerators. The possibilities to use
the already operating machines are also discussed. It is emphasized that the
present status of QCD spin studies necessarily requires a wide range of spin
measurementsComment: 44 pages with 8 figures available by request from authors, IHEP
93-39, LaTe
Heavy-quark parton distribution functions and their uncertainties
We investigate the uncertainties of the heavy-quark parton distribution functions in the variable flavor number scheme. Because the charm- and bottom-quark parton distribution functions (PDFs) are constructed predominantly from the gluon PDF, it is a common practice to assume that the heavy-quark and gluon uncertainties are the same. We show that this approximation is a reasonable first guess, but it is better for bottom quarks than charm quarks. We calculate the PDF uncertainty for t-channel single-top-quark production using the Hessian matrix method, and predict a cross section of 2.12+0.32-0.29 pb at run II of the Tevatron
q_T Uncertainties for W and Z Production
Analysis of semi-inclusive DIS hadroproduction suggests broadening of
transverse momentum distributions at small x below 1E-3 ~ 1E-2 which can be
modeled in the Collins-Soper-Sterman formalism by a modification of impact
parameter dependent parton densities. We investigate these consequences for the
production of electroweak bosons at the Tevatron and the LHC. If substantial
small-x broadening is observed in forward Z boson production in the Tevatron
Run-2, it will strongly affect the predicted q_T distributions for W and Z
boson production at the LHC.Comment: 4 pages, 2 figures; contribution to the XIII International Workshop
on Deep Inelastic Scattering (DIS 2005
Electroweak gauge boson production at hadron colliders through O(alpha_s^2)
We describe a calculation of the O(alpha_s^2) QCD corrections to the fully
differential cross section for W and Z boson production in hadronic collisions.
The result is fully realistic in that it includes spin correlations, finite
width effects, gamma-Z interference and allows for the application of arbitrary
cuts on the leptonic decay products of the W and Z. We have implemented this
calculation into a numerical program. We demonstrate the use of this code by
presenting phenomenological results for several future LHC analyses and recent
Tevatron measurements, including the W cross section in the forward rapidity
region and the central over forward cross section ratio.Comment: 11 pages, 4 figure
Collider Inclusive Jet Data and the Gluon Distribution
Inclusive jet production data are important for constraining the gluon
distribution in the global QCD analysis of parton distribution functions. With
the addition of recent CDF and D0 Run II jet data, we study a number of issues
that play a role in determining the up-to-date gluon distribution and its
uncertainty, and produce a new set of parton distributions that make use of
that data. We present in detail the general procedures used to study the
compatibility between new data sets and the previous body of data used in a
global fit. We introduce a new method in which the Hessian matrix for
uncertainties is ``rediagonalized'' to obtain eigenvector sets that
conveniently characterize the uncertainty of a particular observable.Comment: Published versio
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