201 research outputs found
Probing Form Factors in Top Quark Pair Production at Colliders
We describe how to probe new physics through large CP violation effects and
non--standard Z-t-t couplings via the scattering process e^-e^+ -> t tbar.
[Talk presented at the Workshop on Physics and Experiments with Linear
Colliders, Waikoloa, Hawaii, 26-30 April 1993.]Comment: 4 pages, TeXsis, MSUTH 93/0
Production of Two Photons and a Jet Through Gluon Fusion
We have computed the cross-section and distributions for the production of two photons and a jet via the process . In the Standard Model, this process occurs at the one-loop level through pentagon and box diagrams. We show that at the LHC this is a significant mechanism for the production of the two photons and a jet. This process is also an important background to the Higgs boson production, when the Higgs boson decays into two photons. We also explorethis process at the Tevatron
Studying Anomalous and Couplings with Polarized Collisions
We calculate tree-level cross-sections for and
production in proton-antiproton collisions, with one decaying to leptons,
with anomalous electroweak triple-boson coupling parameters and
. We compare the unpolarized cross-sections to those for a polarized
proton beam, to study how a polarized proton beam would improve experimental
tests of anomalous couplings.Comment: 36 pages, 14 postscript figure
Tracing CP violation in the production of top quark pairs by multiple TeV proton-proton collisions
We investigate the possibilities of searching for non-standard CP violation
in at multiple TeV collision energies. A general kinematic
analysis of the underlying partonic production processes and
in terms of their density matrices is given. We evaluate
the CP-violating parts of these matrices in two-Higgs doublet extensions of the
standard model (SM) and give results for CP asymmetries at the parton level. We
show that these asymmetries can be traced by measuring suitable observables
constructed from energies and momenta of the decay products of and . We find CP-violating effects to be of the order of and show that
possible contaminations induced by SM interactions are savely below the
expected signals.Comment: 24 pages, SLAC-PUB-6403, PITHA 93/43, 9 Figs. available upon request.
Written in LaTe
A Probe of New Physics in Top Quark Pair Production at Colliders
We describe how to probe new physics through examination of the form factors
describing the Ztt couplings via the scattering process e^-e^+->t+tbar. We
focus on experimental methods on how the top quark momentum can be determined
and show how this can be applied to select polarized samples of
pairs through the angular correlations in the final state leptons. We also
study the dependence on the energy and luminosity of an \ee\ collider to probe
a CP violating asymmetry at the level.}Comment: 24 pages in TeXsis (figures available upon request) (revised July
1993
Non-perturbative effects and the resummed Higgs transverse momentum distribution at the LHC
We investigate the form of the non-perturbative parameterization in both the
impact parameter (b) space and transverse momentum (p_T) space resummation
formalisms for the transverse momentum distribution of single massive bosons
produced at hadron colliders. We propose to analyse data on Upsilon
hadroproduction as a means of studying the non-perturbative contribution in
processes with two gluons in the initial state. We also discuss the theoretical
errors on the resummed Higgs transverse momentum distribution at the LHC
arising from the non-perturbative contribution.Comment: 22 pages, 10 figure
Electroweak Gauge-Boson Production at Small q_T: Infrared Safety from the Collinear Anomaly
Using methods from effective field theory, we develop a novel, systematic
framework for the calculation of the cross sections for electroweak gauge-boson
production at small and very small transverse momentum q_T, in which large
logarithms of the scale ratio M_V/q_T are resummed to all orders. These cross
sections receive logarithmically enhanced corrections from two sources: the
running of the hard matching coefficient and the collinear factorization
anomaly. The anomaly leads to the dynamical generation of a non-perturbative
scale q_* ~ M_V e^{-const/\alpha_s(M_V)}, which protects the processes from
receiving large long-distance hadronic contributions. Expanding the cross
sections in either \alpha_s or q_T generates strongly divergent series, which
must be resummed. As a by-product, we obtain an explicit non-perturbative
expression for the intercept of the cross sections at q_T=0, including the
normalization and first-order \alpha_s(q_*) correction. We perform a detailed
numerical comparison of our predictions with the available data on the
transverse-momentum distribution in Z-boson production at the Tevatron and LHC.Comment: 34 pages, 9 figure
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