1,080 research outputs found
Major Facilitator Superfamily Domain-Containing Protein 2a (MFSD2A) Has Roles in Body Growth, Motor Function, and Lipid Metabolism
10.1371/journal.pone.0050629PLoS ONE711
STRATAGEM, A personal computer-based management training game on energy-environment interactions
STRATAGEM, A personal computer-based management training game on energy-environment interactions
STRATAGEM, A personal computer-based management training game on energy-environment interactions
Production of -pairs at HERA-
The production of -pairs as a possible measure of the polarized gluon
distribution is studied for proton--nucleon collisions at
\sqrt{s} =40\;\mbox{GeV}^2 (HERA-). Possibilities of
reconstructing the helicity state of at least one of the 's are
critically reviewed. The observation of production asymmetries in the single
polarized mode of HERA- is found to be not feasible.Comment: 8 pages, LATeX, 3 figures availabe as .uu-fil
MHV Rules for Higgs Plus Multi-Gluon Amplitudes
We use tree-level perturbation theory to show how non-supersymmetric one-loop
scattering amplitudes for a Higgs boson plus an arbitrary number of partons can
be constructed, in the limit of a heavy top quark, from a generalization of the
scalar graph approach of Cachazo, Svrcek and Witten. The Higgs boson couples to
gluons through a top quark loop which generates, for large top mass, a
dimension-5 operator H tr G^2. This effective interaction leads to amplitudes
which cannot be described by the standard MHV rules; for example, amplitudes
where all of the gluons have positive helicity. We split the effective
interaction into the sum of two terms, one holomorphic (selfdual) and one
anti-holomorphic (anti-selfdual). The holomorphic interactions give a new set
of MHV vertices -- identical in form to those of pure gauge theory, except for
momentum conservation -- that can be combined with pure gauge theory MHV
vertices to produce a tower of amplitudes with more than two negative
helicities. Similarly, the anti-holomorphic interactions give anti-MHV vertices
that can be combined with pure gauge theory anti-MHV vertices to produce a
tower of amplitudes with more than two positive helicities. A Higgs boson
amplitude is the sum of one MHV-tower amplitude and one anti-MHV-tower
amplitude. We present all MHV-tower amplitudes with up to four
negative-helicity gluons and any number of positive-helicity gluons (NNMHV).
These rules reproduce all of the available analytic formulae for Higgs +
n-gluon scattering (n<=5) at tree level, in some cases yielding considerably
shorter expressions.Comment: 34 pages, 8 figures; v2, references correcte
Superconducting gap in the presence of bilayer splitting in underdoped Bi(Pb)2212
The clearly resolved bilayer splitting in ARPES spectra of the underdoped
Pb-Bi2212 compound rises the question of how the bonding and antibonding sheets
of the Fermi surface are gapped in the superconducting state. Here we compare
the superconducting gaps for both split components and show that within the
experimental uncertainties they are identical. By tuning the relative intensity
of the bonding and antibonding bands using different excitation conditions we
determine the precise {\bf k}-dependence of the leading edge gap. Significant
deviations from the simple cos()-cos() gap function for the
studied doping level are detected.Comment: 5 pages, 4 figures (revtex4
Investigating the origins of transverse spin asymmetries at RHIC
We discuss possible origins of transverse spin asymmetries in hadron-hadron
collisions and propose an explanation in terms of a chiral-odd T-odd
distribution function with intrinsic transverse momentum dependence, which
would signal a correlation between the transverse spin and the transverse
momentum of quarks inside an unpolarized hadron. We will argue that despite its
conceptual problems, it can account for single spin asymmetries, for example in
p + p(transversely polarized) -> pion + X, and at the same time for the large
cos(2 phi) asymmetry in the unpolarized Drell-Yan cross section, which still
lacks understanding. We use the latter asymmetry to arrive at a crude model for
this function and show explicitly how it relates unpolarized and polarized
observables in the Drell-Yan process, as could be measured with the
proton-proton collisions at RHIC. Moreover, it would provide an alternative
method of accessing the transversity distribution function h_1. For future
reference we also list the complete set of azimuthal asymmetries in the
unpolarized and polarized Drell-Yan process at leading order involving T-odd
distribution functions with intrinsic transverse momentum dependence.Comment: 14 pages, Revtex, 4 Postscript figures, uses aps.sty, epsf.sty, Minor
mistakes in cross sections corrected, Conclusions are unaffecte
Azimuthal asymmetries in lepton-pair production at a fixed-target experiment using the LHC beams (AFTER)
A multi-purpose fixed-target experiment using the proton and lead-ion beams
of the LHC was recently proposed by Brodsky, Fleuret, Hadjidakis and Lansberg,
and here we concentrate our study on some issues related to the spin physics
part of this project (referred to as AFTER). We study the nucleon spin
structure through and processes with a fixed-target experiment using
the LHC proton beams, for the kinematical region with 7 TeV proton beams at the
energy in center-of-mass frame of two nucleons GeV. We calculate
and estimate the azimuthal asymmetries of unpolarized and
dilepton production processes in the Drell--Yan continuum region and at the
-pole. We also calculate the , and
azimuthal asymmetries of and dilepton production
processes with the target proton and deuteron longitudinally or transversally
polarized in the Drell--Yan continuum region and around resonances region.
We conclude that it is feasible to measure these azimuthal asymmetries,
consequently the three-dimensional or transverse momentum dependent parton
distribution functions (3dPDFs or TMDs), at this new AFTER facility.Comment: 15 pages, 40 figures. Version accepted for publication in EPJ
Improved description of charged Higgs boson production at hadron colliders
We present a new method for matching the two twin-processes gb->H+/-t and
gg->H+/-tb in Monte Carlo event generators. The matching is done by defining a
double-counting term, which is used to generate events that are subtracted from
the sum of these two twin-processes. In this way we get a smooth transition
between the collinear region of phase space, which is best described by
gb->H+/-t, and the hard region, which requires the use of the gg->H+/-tb
process. The resulting differential distributions show large differences
compared to both the gb-> H+/-t and gg->H+/-tb processes illustrating the
necessity to use matching when tagging the accompanying b-jet.Comment: 21 pages, 9 figures. Revised with updated discussion and reference
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