23 research outputs found
Revisiting the -Meson Production at the Hadronic Colliders
The production of heavy-flavored hadron at the hadronic colliders provides a
challenging opportunity to test the validity of pQCD predictions. There are two
mechanisms for the hadroproduction, i.e. the gluon-gluon fusion
mechanism via the subprocess and the
extrinsic heavy quark mechanism via the subprocesses and , both of which shall have sizable
contributions in proper kinematic region. Different from the
fixed-flavor-number scheme (FFNS) previously adopted in the literature, we
study the hadroproduction under the general-mass
variable-flavor-number scheme (GM-VFNS), in which we can consistently deal with
the double counting problem from the above two mechanisms. Properties for the
hadroproduction are discussed. To be useful reference, a
comparative study of FFNS and GM-VFNS is presented. Both of which can provide
reasonable estimations for the hadroproduction. At the Tevatron,
the difference between these two schemes is small, however such difference is
obvious at the LHC. The forthcoming more precise data on LHC shall provide a
good chance to check which scheme is more appropriate to deal with the
-meson production and to further study the heavy quark components in
hadrons.Comment: 18 pages, 8 figures, 4 tables. To match the published version. To be
published in Eur.Phys.J.
Neutralino Dark Matter beyond CMSSM Universality
We study the effect of departures from SUSY GUT universality on the
neutralino relic density and both its direct detection and indirect detection,
especially by neutrino telescopes. We find that the most interesting models are
those with a value of lower than the universal case.Comment: 20 pages, 12 figures, JHEP format. Figures improved for B&W,
references added, typos and english correcte
Photoproduction in Scattering
We investigate the + c + photoproduction in
collision at the LEP II energy. The physical motivations for this study are: 1)
such next-to-leading order(NLO) process was not considered in previous
investigations of photoproduction in interaction, and it is
worthwhile to do so in order to make sound predictions for experimental
comparison; 2) from recent Belle experiment results, the process with same
final states at the factory has a theoretically yet unexplainable large
fraction; hence it is interesting to see what may happen at other colliders; 3)
the existing LEP data are marginal in observing such process, and at the planed
Linear Colliders(LCs) this process can be measured with high accuracy; 4) it is
necessary to take this process into consideration in the aim of elucidating the
quarkonium production mechanism, especially in testing the universality of
NRQCD nonperturbative matrix elements via photoproduction in
electron-position collisions.Comment: 15 pages, 3 figure
On the mechanisms of heavy-quarkonium hadroproduction
We discuss the various mechanisms potentially at work in hadroproduction of
heavy quarkonia in the light of computations of higher-order QCD corrections
both in the Colour-Singlet (CS) and Colour-Octet (CO) channels and the
inclusion of the contribution arising from the s-channel cut in the CS channel.
We also discuss new observables meant to better discriminate between these
different mechanisms.Comment: Invited review talk at 3rd International Conference On Hard And
Electromagnetic Probes Of High-Energy Nuclear Collisions (HP2008), 8-14 June
2008, Illa da Toxa, Galicia, Spain. 11 pages, 21 figures, LaTeX, uses
svjour.cls and svepj.clo (included
Reconciling Neutralino Relic Density with Yukawa Unified Supersymmetric Models
Supersymmetric grand unified models based on the gauge group SO(10) are
especially attractive in light of recent data on neutrino masses. The simplest
SO(10) SUSY GUT models predict unification of third generation Yukawa couplings
in addition to the usual gauge coupling unification. Recent surveys of Yukawa
unified SUSY GUT models predict an inverted scalar mass hierarchy in the
spectrum of sparticle masses if the superpotential mu term is positive. In
general, such models tend to predict an overabundance of dark matter in the
universe. We survey several solutions to the dark matter problem in Yukawa
unified supersymmetric models. One solution-- lowering the GUT scale mass value
of first and second generation scalars-- leads to u_R and c_R squark masses in
the 90-120 GeV regime, which should be accessible to Fermilab Tevatron
experiments. We also examine relaxing gaugino mass universality which may solve
the relic density problem by having neutralino annihilations via the Z or h
resonances, or by having a wino-like LSP.Comment: 21 page file plus 9 figures; updated version to coincide with
published versio
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
SURVIVAL OF SALMONELLAE AND Escherichia coli DURING THE SPRAY DRYING OF VARIOUS FOOD PRODUCTS
Report of the Supersymmetry Theory Subgroup
We provide a mini-guide to some of the possible manifestations of weak scale supersymmetry. For each of six scenarios we provide ffl a brief description of the theoretical underpinnings, ffl the adjustable parameters, ffl a qualitative description of the associated phenomenology at future colliders, ffl comments on how to simulate each scenario with existing event generators. I. INTRODUCTION The Standard Model (SM) is a theory of spin- 1 2 matter fermions which interact via the exchange of spin-1 gauge bosons, where the bosons and fermions live in independent representations of the gauge symmetries. Supersymmetry (SUSY) is a symmetry which establishes a one-to-one correspondence between bosonic and fermionic degrees of freedom, and provides a relation between their couplings[1]. Relativistic quantum field theory is formulated to be consistent with the symmetries of the Lorentz/Poincare group-- a non-compact Lie algebra. Mathematically, supersymmetry is formulated as a generaliza..