5,209 research outputs found
Effects of QCD Resummation on and Production at the Tevatron
The resummation of multiple soft gluon emission affects the production rate
and kinematic distributions of (where h is a Higgs boson) and
pairs at the Tevatron with TeV. Using the Collins-Soper-Sterman
resummation formalism, the production rate is enhanced over the
next-to-leading-order (NLO) prediction by 2-3% for the process, for
Higgs boson masses between 80-120 GeV, and over 3% for the process
for GeV. After resummation, the rate changes by 12-13% when
is varied by GeV. Various kinematic distributions are presented
for the individual final state particles and for the pair. The explicit
radiation of hard gluons in NLO QCD is included also for the final
state.Comment: 9 pages, 12 Postscript figures, in RevTeX format, uses epsf.te
Detecting a Light Stop from Top Decays at the Tevatron
We study the possibility of discovering or excluding a light top squark
(stop) based on top quark decays in the t-tbar events produced at the Fermilab
Tevatron. In particular, we consider the Minimal Supersymmetric Standard Model
with the sparticle spectrum m_{chi^+_1}+m_b, M_W+m_{chi^0_1}+m_b > m_{stop} >
m_{chi^0_1}+m_c, where chi^0_1 is the lightest neutralino and chi^+_1 is the
lightest chargino, so that t -> stop chi^0_1 and stop -> c chi^0_1. All other
sparticle masses are assumed to be heavier than m_t. Such a spectrum seeks to
explain the experimental values of alpha_s(M_Z^2), R_b and A_{LR} obtained from
LEP/SLC data. We find that the prospect to observe a light stop via this
channel at the Tevatron is very promising.Comment: 12 pages with 1 Postscript figure using psfig.sty. Postscript file
available at http://sgi2.hep.anl.gov:8001/index.htm
Matching parton showers to NLO computations
We give a prescription for attaching parton showers to next-to-leading order
(NLO) partonic jet cross sections in electron-positron annihilation. Our method
effectively extends to NLO the scheme of Catani, Krauss, Kuhn, and Webber for
matching between m hard jets and (m+1) hard jets. The matching between parton
splitting as part of a shower and parton splitting as part of NLO matrix
elements is based on the Catani-Seymour dipole subtraction method that is
commonly used for removing the singularities from the NLO matrix elements.}Comment: 45 pages, new introduction, more detailed discussion of the Sudakov
reweightin
K0s-K0s correlations in 7 TeV pp collisions from the ALICE experiment at the LHC
Identical neutral kaon pair correlations are measured in 7 TeV pp collisions
in the ALICE experiment. K0s-K0s correlation functions are formed in 3
multiplicity X 4 kT bins. The femtoscopic kaon source parameters Rinv and
lambda are extracted from these correlation functions by fitting a (femtoscopy)
X (PYTHIA) model to them, PYTHIA accounting for the non-flat baseline found in
pp collisions. Source parameters are obtained from a fit which includes quantum
statistics and final-state interactions of the a0/f0 resonance. K0s-K0s
correlations show a systematic increase in Rinv for increasing multiplicity bin
and decreasing Rinv for increasing kT bin as seen in pi-pi correlations in the
pp system, as well as seen in heavy-ion collisions. Also, K0s-K0s correlations
are observed to smoothly extend this pi-pi Rinv behavior for the pp system up
to about three times higher kT than the kT range measured in pi-pi
correlations.Comment: Proceedings of the Quark Matter 2011 Conference, 4 pages, 5 figure
Recommended from our members
Practical algorithms for multivariate rational approximation
17 USC 105 interim-entered record; under review.The article of record as published may be found at https://doi.org/10.1016/j.cpc.2020.107663We present two approaches for computing rational approximations to multivariate functions, motivated by their effectiveness as surrogate models for high-energy physics (HEP) applications. Our first
approach builds on the Stieltjes process to efficiently and robustly compute the coefficients of the
rational approximation. Our second approach is based on an optimization formulation that allows us
to include structural constraints on the rational approximation (in particular, constraints demanding
the absence of singularities), resulting in a semi-infinite optimization problem that we solve using an
outer approximation approach. We present results for synthetic and real-life HEP data, and we compare
the approximation quality of our approaches with that of traditional polynomial approximations.This work was supported by the U.S. Department of Energy, Office of Science, Advanced Scientific Computing Research, under Contract DE-AC02-06CH11357. Support for this work was provided through the SciDAC program funded by U.S. Department of Energy, Office of Science, Advanced Scientific Computing Re search. This work was also supported by the U.S. Department of Energy through grant DE-FG02-05ER25694, and by Fermi Re search Alliance, LLC, United States of America under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Advanced Scientific Computing Research and Office of Nuclear Physics, Scientific Discovery through Advanced Computing (SciDAC) program through the FASTMath Institute under Contract No. DE-AC02-05CH11231 at Lawrence Berkeley National Laboratory
Matching matrix elements and shower evolution for top-quark production in hadronic collisions
We study the matching of multijet matrix elements and shower evolution in the
case of top production in hadronic collisions at the Tevatron and at the LHC.
We present the results of the matching algorithm implemented in the ALPGEN
Monte Carlo generator, and compare them with results obtained at the parton
level, and with the predictions of the MC@NLO approach. We highlight the
consistency of the matching algorithm when applied to these final states, and
the excellent agreement obtained with MC@NLO for most inclusive quantities. We
nevertheless identify also a remarkable difference in the rapidity spectrum of
the leading jet accompanying the top quark pair, and comment on the likely
origin of this discrepancy.Comment: 22 pages, 13 figures, 5 tables. JHEP styl
- …