98 research outputs found
Next-to-Leading Order QCD Corrections to the Polarized Photoproduction of Heavy Flavors
We present a calculation of the next-to-leading order (O(alpha_s^2 alpha))
QCD corrections to heavy flavor photoproduction with longitudinally polarized
beams. We apply our results to study the longitudinal spin asymmetry for the
total charm quark production cross section which will be utilized by the
forthcoming COMPASS experiment at CERN to obtain first direct information on
the polarized gluon density Delta g. We also briefly discuss the main
theoretical uncertainties inherent in this calculation. In particular we
demonstrate that the factorization scale dependence is considerably reduced in
next-to-leading order.Comment: 18 pages, LaTeX, 4 figures, uses epsfig and amssymb style
Small x resummations confronted with F_2(x,Q^2) data
It has been observed recently that a consistent LO BFKL gluon evolution leads
to a steep growth of F_2(x,Q^2) for x -> 0 almost independently of Q^2. We show
that current data from the DESY HERA collider are precise enough to finally
rule out a pure BFKL behaviour in the accessible small x region. Several
attempts have been made by other groups to treat the BFKL type small x
resummations instead as additions to the conventional anomalous dimensions of
the successful renormalization group ``Altarelli-Parisi'' equations. We
demonstrate that all presently available F_2 data, in particular at lower
values of Q^2, can not be described using the presently known NLO (two-loop
consistent) small x resummations. Finally we comment on the common reason for
the failure of these BFKL inspired methods which result, in general, in too
steep x-dependencies as x -> 0.Comment: Revised, to be published in Phys. Lett. B., 18 pages, LaTeX2e, 3
figures, uses amssymb and epsfig style
Prospects of Open Charm Production at GSI-FAIR and J-PARC
We present a detailed phenomenological study of the prospects of open charm
physics at the future and facilities GSI-FAIR and J-PARC,
respectively. In particular, we concentrate on differential cross sections and
the charge and longitudinal double-spin asymmetries at next-to-leading order
accuracy. Theoretical uncertainties for the proposed observables are estimated
by varying the charm quark mass and the renormalization and factorization
scales.Comment: 11 pages, 13 figure
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Cortical hot spots and labyrinths: Why cortical neuromodulation for episodic migraine with aura should be personalized
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Next-to-leading order QCD corrections to the polarized hadroproduction of heavy flavors
We present the complete next-to-leading order QCD corrections to the polarized hadroproduction of heavy flavors which soon will be studied experimentally in polarized pp collisions at the BNL Relativistic Heavy Ion Collider (RHIC) in order to constrain the polarized gluon density Δg. It is demonstrated that the dependence on unphysical renormalization and factorization scales is strongly reduced beyond the leading order. The sensitivity of the charm quark spin asymmetry to Δg is analyzed in some detail, including the limited detector acceptance for leptons from charm quark decays at the BNL RHIC.Ingo Bojak and Marco Stratman
Everything you wanted to ask about EEG but were afraid to get the right answer
We answer several important questions concerning EEG. We also shortly discuss importance of nonlinear methods of contemporary physics in EEG analysis. Basic definitions and explanation of fundamental concepts may be found in my previous publications in NBP
Heavy quark production as sensitive test for an improved description of high energy hadron collisions
QCD dynamics at small quark and gluon momentum fractions or large total
energy, which plays a major role for HERA, the Tevatron, RHIC and LHC physics,
is still poorly understood. For one of the simplest processes, namely
bottom-antibottom production, next-to-leading-order perturbation theory fails.
We show that the combination of two recently developed theoretical concepts,
the k_perp-factorization and the next-to-leading-logarithmic-approximation BFKL
vertex, gives perfect agreement with data. One can therefore hope that these
concepts provide a valuable foundation for the description of other high energy
processes.Comment: RevTeX, 4 pages, 7 figures titel and abstract changed, several
formulations modified in the text, 1 figure droppe
Collinear Subtractions in Hadroproduction of Heavy Quarks
We present a detailed discussion of the collinear subtraction terms needed to
establish a massive variable-flavour-number scheme for the one-particle
inclusive production of heavy quarks in hadronic collisions. The subtraction
terms are computed by convoluting appropriate partonic cross sections with
perturbative parton distribution and fragmentation functions relying on the
method of mass factorization. We find (with one minor exception) complete
agreement with the subtraction terms obtained in a previous publication by
comparing the zero-mass limit of a fixed-order calculation with the genuine
massles results in the MSbar scheme. This presentation will be useful for
extending the massive variable-flavour-number scheme to other processes.Comment: 29 pages, 17 figures include
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