15,698 research outputs found
Baseline Cold Matter Effects on J/psi Production in AA Collisions
We present baseline calculations of initial-state shadowing and final-state
absorption effects on J/psi production in nucleus-nucleus collisions at the
Relativistic Heavy Ion Collider. We show predictions for Au+Au and Cu+Cu
collisions at \sqrt{S_{NN}}=200 GeV and Cu+Cu collisions at \sqrt{S_{NN}} = 62
GeV as a function of the rapidity, y, and the number of binary nucleon-nucleon
collisions, N_{\rm coll}.Comment: 7 pages, 4 figures, uses hiph-art.sty, one figure replaced, some
corrections to tex
Systematics of Heavy Quark Production at RHIC
We discuss a program for systematic studies of heavy quark production in
, and interactions. The production cross sections
themselves cannot be accurately predicted to better than 50% at RHIC. For
studies of deviations in production such as those by nuclear
shadowing and heavy quark energy loss, the cross section thus needs to be
measured. We then show that the ratio of to dilepton mass
distributions can provide a measurement of the nuclear gluon distribution. With
total rates and nuclear shadowing under control it is easier to study energy
loss and to use as a normalization of production.Comment: 10 pages, uses special included style file, 4 eps figures, for
proceedings of the 18th Winter Workshop on Nuclear Dynamics, Jan. 200
What is the Real K Factor?
The theoretical K factor, describing the difference between the leading and
higher order cross sections, has no precise definition. The definition is
sensitive to the order of the fit to the parton densities and the number of
loops at which alpha_s is evaluated. We describe alternate ways to define the K
factor and show how the definition affects its magnitude and shape for examples
of hadroproduction of W^+ bosons, Drell-Yan lepton pairs, and heavy quarks. We
discuss which definition is appropriate under certain circumstances.Comment: 25 pages, uses special included style file, 14 eps figures, submitted
to Heavy Ion Physic
The total charm cross section
We assess the theoretical uncertainties on the total charm cross section. We
discuss the importance of the quark mass, the scale choice and the parton
densities on the estimate of the uncertainty. We conclude that due to the small
charm quark mass, which amplifies the effect of the other parameters in the
calculation, the uncertainty on the total charm cross section is difficult to
quantify.Comment: 11 pages, 4 figures, for Zimanyi memorial conferenc
Phenomenology of Charm and Bottom Production
We discuss the renormalization and factorization scale dependence of charm
and bottom production both at fixed-target energies and at present and future
colliders. We investigate whether distributions calculable at leading order can
be extrapolated to next-to-leading order by a constant multiplicative factor.Comment: 18 pages, 10 Postscript figures, compressed and uuencoded, included
in a separate file or available from the author. To be published in Z. Phys.
Iterated Monoidal Categories
We develop a notion of iterated monoidal category and show that this notion
corresponds in a precise way to the notion of iterated loop space. Specifically
the group completion of the nerve of such a category is an iterated loop space
and free iterated monoidal categories give rise to finite simplicial operads of
the same homotopy type as the classical little cubes operads used to
parametrize the higher H-space structure of iterated loop spaces. Iterated
monoidal categories encompass, as a special case, the notion of braided tensor
categories, as used in the theory of quantum groups.Comment: 55 pages, 3 PostScript figure
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