7,121 research outputs found
Probing the Higgs self-coupling at hadron colliders using rare decays
We investigate Higgs boson pair production at hadron colliders for Higgs
boson masses m_H\leq 140 GeV and rare decay of one of the two Higgs bosons.
While in the Standard Model the number of events is quite low at the LHC, a
first, albeit not very precise, measurement of the Higgs self-coupling is
possible in the gg -> HH -> b\bar{b}\gamma\gamma channel. A luminosity-upgraded
LHC could improve this measurement considerably. A 200 TeV VLHC could make a
measurement of the Higgs self-coupling competitive with a next-generation
linear collider. In the MSSM we find a significant region with observable Higgs
pair production in the small \tan\beta regime, where resonant production of two
light Higgs bosons might be the only hint at the LHC of an MSSM Higgs sector.Comment: Revtex, 23 pages, 4 tables, 7 figure
Logarithmic electroweak corrections to gauge-boson pair production at the LHC
We have studied the effects of the complete logarithmic electroweak O(alpha)
corrections on the production of vector-boson pairs WZ, ZZ, and WW at the LHC.
These corrections are implemented into a Monte Carlo program for pp -> 4f
(+\gamma) with final states involving four or two leptons using the double-pole
approximation. We numerically investigate purely leptonic final states and find
that electroweak corrections lower the predictions by 5-30% in the physically
interesting region of large di-boson invariant mass and large angle of the
produced vector bosons.Comment: 47 pages, LaTeX, 18 eps figure
Mixed top-bottom squark production at the LHC
We calculate cross sections for mixed stop-sbottom pair production at the
LHC, analogous to single-top production, a weak process involving the
W-t(i)-b(j) vertex. While coupling-suppressed relative to QCD same-flavor
squark pair production, the signal is distinctive due to heavy-flavor tagging
along with a possible same-sign lepton pair in the final state. SUSY
backgrounds can often be suppressed many orders of magnitude by taking
advantage of distinct kinematic differences from the signal. Measuring the rate
of this process would add significant additional information to that gathered
from other SUSY processes. If the stop and sbottom mixings can be determined
elsewhere, stop-sbottom production would provide for a measurement of the weak
squark gauge coupling and super-CKM vertex factor.Comment: typo corrected, comment on W-associated channel added, version to
appear in PR
Higher-order QED corrections to W-boson mass determination at hadron colliders
The impact of higher-order final-state photonic corrections on the precise
determination of the W-boson mass at the Tevatron and LHC colliders is
evaluated. In the presence of realistic selection criteria, the shift in the W
mass from a fit to the transverse mass distribution is found to be about 10 MeV
in the channel and almost negligible in the
channel. The calculation, which is implemented in a Monte Carlo event generator
for data analysis, can contribute to reduce the uncertainty associated to the W
mass measurement at future hadron collider experiments.Comment: 9 pages, 2 figures, 1 table, RevTe
Race and Affirmative Action in “Post-Racial” Democratic Brazil
This thesis examines the ways that Brazilians are evaluated for their privileges in qualification for the affirmative action program. It critically examines the existing policies, how they function, and how they affect ideas of race in Brazil for both black and non-black Brazilians. Additionally, it proposes that the policies prioritize phenotype as a primary condition for qualifying for a quota in order to accomplish their initial objectives of fighting racial inequalities, compensating for historical injustices, contributing to the diversity of experiences and perspectives on campuses and in federal offices, and raising understanding of what it means to be black in Brazil
Two Photon Radiation in W and Z Boson Production at the Tevatron Collider
We present a calculation of two photon radiation in W and Z boson production
in hadronic collisions, based on the complete matrix elements for the processes
q\bar q'\to\ell^\pm\nu\gamma\gamma and q\bar q\to\ell^+\ell^-\gamma\gamma,
including finite charged lepton masses. In order to achieve stable numerical
results over the full phase space, multiconfiguration Monte Carlo techniques
are used to map the peaks in the differential cross section. Numerical results
are presented for the Fermilab Tevatron.Comment: Revtex, 28 pages, 3 figure
Direct Measurement of the Top Quark Charge at Hadron Colliders
We consider photon radiation in tbar-t events at the upgraded Fermilab
Tevatron and the CERN Large Hadron Collider (LHC) as a tool to measure the
electric charge of the top quark. We analyze the contributions of tbar-t-gamma
production and radiative top quark decays to p-p, pbar-p -> gamma l^+/- nu
bbar-b jj, assuming that both b-quarks are tagged. With 20~fb^{-1} at the
Tevatron, the possibility that the ``top quark'' discovered in Run I is
actually an exotic charge -4/3 quark can be ruled out at the 95% confidence
level. At the LHC, it will be possible to determine the charge of the top quark
with an accuracy of about 10%.Comment: Revtex, 24 pages, 2 tables, 9 figure
Region of hadron-quark mixed phase in hybrid stars
Hadron--quark mixed phase is expected in a wide region of the inner structure
of hybrid stars. However, we show that the hadron--quark mixed phase should be
restricted to a narrower region to because of the charge screening effect. The
narrow region of the mixed phase seems to explain physical phenomena of neutron
stars such as the strong magnetic field and glitch phenomena, and it would give
a new cooling curve for the neutron star.Comment: to be published in Physical Review
Comment on 's and the H1 and ZEUS High Anomalies
We investigate the effects of extra neutral gauge bosons on the high
region of the cross section at GeV. We found
that the only models with electroweak strength coupling, typical of extended
gauge theories, that give a better fit to the H1 and ZEUS high data than
the standard model, are ruled out by existing data from the Tevatron. From
general scaling arguments, using the allowed contact interactions, the only
allowed models with 's would be those with strong couplings although even
in this case the statistical evidence is not compelling.Comment: Latex file uses revtex version 3, epsfig, 1 postscript figure is
attache
- …