630 research outputs found
Inclusive b and b anti-b production with quasi-multi-Regge kinematics at the Tevatron
We consider b-jet hadroproduction in the quasi-multi-Regge-kinematics
approach based on the hypothesis of gluon and quark Reggeization in t-channel
exchanges at high energies. The preliminary data on inclusive b-jet and b
anti-b-dijet production taken by the CDF Collaboration at the Fermilab Tevatron
are well described without adjusting parameters. We find the main contribution
to inclusive b-jet production to be the scattering of a Reggeized gluon and a
Reggeized b-quark to a b quark, which is described by the effective
Reggeon-Reggeon-quark vertex. The main contribution to b anti-b-pair production
arises from the scattering of two Reggeized gluons to a b anti-b pair, which is
described by the effective Reggeon-Reggeon-quark-quark vertex. Our anaysis is
based on the Kimber-Martin-Ryskin prescription for unintegrated gluon and quark
distribution functions using as input the Martin-Roberts-Stirling-Thorne
collinear parton distribution functions of the proton.Comment: 14 pages, 4 figures; formulas for effective vertices included,
discussion of errors somewhat expanded; accepted for publication in Phys.
Rev.
Dependence of Electroweak Parameters on the Definition of the Top-Quark Mass
The QCD corrections to electroweak parameters depend on the renormalization
scheme and scales used to define the top-quark mass. We analyze these
dependences for the W-boson mass predicted via Delta r to O(alpha alpha_s) and
O(alpha alpha_s^2) in the on-shell and MS-bar schemes. These variations provide
us with a hint on the magnitude of the unknown higher-order QCD effects and
contribute to the theoretical error of the prediction.Comment: 27 pages (Latex), 6 figures (uuencoded compressed tarred Postscript).
Extended and updated version, which incorporates the recently calculated
next-to-leading-order QCD corrections to Delta rho and Delta
Virtual Top-Quark Effects on the H->bb-bar Decay at Next-to-Leading Order in QCD
By means of a heavy-top-quark effective Lagrangian, we calculate the
three-loop corrections of O(alpha_s^2 G_F M_t^2) to the H->bb-bar partial decay
width of the standard-model Higgs boson with intermediate mass M_H<<2M_t. We
take advantage of a soft-Higgs theorem to construct the relevant coefficient
functions. We present our result both in the MS-bar and on-shell schemes of
mass renormalization. The MS-bar formulation turns out to be favourable with
regard to the convergence behaviour. We also test a recent idea concerning the
naive non-abelianization of QCD.Comment: 8 pages (Latex), 5 figures (Postscript
D-meson production in the GM-VFN scheme
We study the inclusive hadrodroduction of D^0, D^+, D^{*+}, and D_s^+ mesons
at next-to-leading order in the parton model of quantum chromodynamics endowed
with universal non-perturbative fragmentation functions (FFs) fitted to e^+e^-
annihilation data from CERN LEP1. Working in the general-mass
variable-flavor-number scheme, we resum the large logarithms through the
evolution of the FFs and, at the same time, retain the full dependence on the
charm-quark mass without additional theoretical assumptions. In this way, the
cross section distributions in transverse momentum recently measured by the CDF
Collaboration in run II at the Fermilab Tevatron are described within errors.Comment: 4 pages, 4 figures, to appear in the Proceedings of the XIV
International Workshop on Deep Inelastic Scattering (DIS 2006), 20-24 April
2006, Tsukuba City, Japa
Quark-Loop Amplitudes for W^+- H^-+ Associated Hadroproduction
In this addendum to our paper entitled "W^+- H^-+ Associated Production at
the Large Hadron Collider" [Phys. Rev. D 59, 015009 (1999)], we list analytic
results for the helicity amplitudes of the partonic subprocess gg -> W^-H^+
induced by virtual quarks.Comment: 6 pages (Latex
Open charm hadroproduction and the charm content of the proton
We advocate charmed-hadron inclusive hadroproduction as a laboratory to probe
intrinsic charm (IC) inside the colliding hadrons. Working at next-to-leading
order in the general-mass variable-flavor-number scheme endowed with
non-perturbative fragmentation functions recently extracted from a global fit
to e^+e^- annihilation data from KEKB, CESR, and LEP1, we first assess the
sensitivity of Tevatron data of D^0, D^+, and D^{*+} inclusive production to
the IC parameterizations provided by Pumplin et al. We then argue that similar
data from pp collisions at RHIC would have the potential to discriminate
between different IC models provided they reach out to sufficiently large
values of transverse momentum.Comment: 22 pages, 7 figures; discussion of large-p_T range at the Tevatron
and high-energy mode of RHIC included, 2 figures added; accepted for
publication in Phys. Rev.
Ultrasoft Effects in Heavy-Quarkonium Physics
In the framework of nonrelativistic QCD, we consider a new class of radiative
corrections, which are generated at next-to-next-to-next-to-leading order
through the chromoelectric dipole interaction of heavy quarkonium with
ultrasoft virtual gluons. We provide analytical formulae from which the
resulting shifts in the quarkonium energy levels and the wave functions at the
origin may be calculated. We discuss the phenomenological implications for the
top-antitop and Upsilon systems and point out some limitations of describing
charmonium using a Coulomb potential.Comment: 14 pages (Latex), 5 figures (Axodraw), one reference added, accepted
for publication in Nuclear Physics
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