7,760 research outputs found
Under Egyptian Skies : Intermezzo March Two - Step
https://digitalcommons.library.umaine.edu/mmb-ps/1968/thumbnail.jp
Top Pair Production Beyond Double-Pole Approximation: pp, pp~ --> 6 Fermions and 0, 1 or 2 Additional Partons
Hadron collider cross sections for tt~ production and di-lepton,
single-lepton and all-jet decays with up to 2 additional jets are calculated
using complete LO matrix elements with 6-, 7- and 8-particle final states. The
fixed-width, complex-mass and overall-factor schemes (FWS, CMS & OFS) are
employed and the quality of narrow-width and double-pole approximations (NWA &
DPA) is investigated for inclusive production and suppressed backgrounds to new
particle searches. NWA and DPA cross sections differ by 1% or less. The
inclusion of sub- and non-resonant amplitudes effects a cross section increase
of 5-8% at pp supercolliders, but only minor changes at the Tevatron. On-shell
tt~/Wtb backgrounds for the H --> WW decay in weak boson fusion, the hadronic
\tau decay of a heavy H^\pm and the \phi --> hh --> \tau\tau bb~ radion decay
at the LHC are updated, with corrections ranging from 3% to 30%. FWS and CMS
cross sections are uniformly consistent, but OFS cross sections are up to 6%
smaller for some backgrounds.Comment: 20 pages, 6 tables, 1 figur
QCD Working Group Report
This is the report of the QCD working group at WHEPP 6. Discussions and work
on heavy ion collisions, polarised scattering, and collider phenomenology are
reported.Comment: Report of the QCD group at WHEPP-6, Chennai, January 2000. 7 page
Higgs and SUSY Searches at LHC
I start with a brief introduction to Higgs mechanism and supersymmetry. Then
I discuss the theoretical expectations, current limits and search strategies
for Higgs boson(s) at LHC --- first in the SM and then in the MSSM. Finally I
discuss the signatures and search strategies for the superparticles.Comment: Typos and figure styles corrected; LaTeX (28 pages) including 13 ps
files containing 11 figures; Invited talk at the 5th Workshop on High Energy
Physics Phenomenology (WHEPP-5), Pune, India, 12 - 25 January 199
Electroweak radiative corrections to W-boson production at hadron colliders
The complete set of electroweak O(alpha) corrections to the Drell--Yan-like
production of W bosons is calculated and compared to an approximation provided
by the leading term of an expansion about the W-resonance pole. All relevant
formulae are listed explicitly, and particular attention is paid to issues of
gauge invariance and the instability of the W bosons. A detailed discussion of
numerical results underlines the phenomenological importance of the electroweak
corrections to W-boson production at the Tevatron and at the LHC. While the
pole expansion yields a good description of resonance observables, it is not
sufficient for the high-energy tail of transverse-momentum distributions,
relevant for new-physics searches.Comment: 29 pages, latex, 17 postscript files, revised version that is to
appear in Phys.Rev.D, some explanations added and results extended by a
discussion of the QED factorization scale dependenc
New Fermions at ee Colliders: I. Production and Decay
We analyze the production in collisions of new heavy fermions
stemming from extensions of the Standard Model. We write down the most general
expression for the production of two heavy fermions and their subsequent
decays, allowing for the polarization of the ee initial state and
taking into account the final polarization of the fermions. We then discuss the
various decay modes including cascade and three body decays, and the production
mechanisms, both pair production and single production in association with
ordinary fermions.Comment: 21 pages (no figures), Preprint UdeM-LPN-TH-93-15
EPS09 - a New Generation of NLO and LO Nuclear Parton Distribution Functions
We present a next-to-leading order (NLO) global DGLAP analysis of nuclear
parton distribution functions (nPDFs) and their uncertainties. Carrying out an
NLO nPDF analysis for the first time with three different types of experimental
input -- deep inelastic +A scattering, Drell-Yan dilepton production in
p+ collisions, and inclusive pion production in d+Au and p+p collisions at
RHIC -- we find that these data can well be described in a conventional
collinear factorization framework. Although the pion production has not been
traditionally included in the global analyses, we find that the shape of the
nuclear modification factor of the pion -spectrum at
midrapidity retains sensitivity to the gluon distributions, providing evidence
for shadowing and EMC-effect in the nuclear gluons. We use the Hessian method
to quantify the nPDF uncertainties which originate from the uncertainties in
the data. In this method the sensitivity of to the variations of the
fitting parameters is mapped out to orthogonal error sets which provide a
user-friendly way to calculate how the nPDF uncertainties propagate to any
factorizable nuclear cross-section. The obtained NLO and LO nPDFs and the
corresponding error sets are collected in our new release called {\ttfamily
EPS09}. These results should find applications in precision analyses of the
signatures and properties of QCD matter at the LHC and RHIC.Comment: 34 pages, 16 figures. The version accepted for publicatio
Finite-Width Effects in Top Quark Production at Hadron Colliders
Production cross sections for t\bar{t} and t\bar{t}j events at hadron
colliders are calculated, including finite width effects and off resonance
contributions for the entire decay chain, t --> bW --> b\ell\nu, for both top
quarks. Resulting background rates to Higgs search at the CERN LHC are updated
for inclusive H --> WW studies and for H --> \tau\tau and H --> WW decays in
weak boson fusion events. Finite width effects are large, increasing
t\bar{t}(j) rates by 20% or more, after typical cuts which are employed for
top-background rejection.Comment: 32 pages, 11 figures, 7 tables; minor changes, reference added, to be
published in Phys. Rev.
Vector Boson Pair Production in Hadronic Collisions at Order : Lepton Correlations and Anomalous Couplings
We present cross sections for production of electroweak vector boson pairs,
, and , in and collisions, at next-to-leading
order in . We treat the leptonic decays of the bosons in the
narrow-width approximation, but retain all spin information via decay angle
correlations. We also include the effects of and anomalous
couplings.Comment: 23 pages, 8 figures, 3 table
Extending the Higgs Boson Reach at the Upgraded Fermilab Tevatron
We study the observability for a Standard Model-like Higgs boson at an
upgraded Tevatron via the modes p \bar p \to gg \to h \to \ww \to \ljj and
. We find that with c. m. energy of 2 TeV and an integrated luminosity of
30 fb the signal may be observable for the mass range of 135 {\gev}
\lsim \mh \lsim 180 GeV at a statistical level. We conclude that
the upgraded Tevatron may have the potential to detect a SM-like Higgs boson in
the mass range from the LEP2 reach to 180 GeV.Comment: revised version, to appear in PR
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