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

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 $W \to \mu \nu$ channel and almost negligible in the $W \to e \nu$ 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

Strategy towards Mirror-fermion Signatures

The existence of mirror fermions interacting strongly under a new gauge group and having masses near the electroweak scale has been recently proposed as a viable alternative to the standard-model Higgs mechanism. The main purpose of this work is to investigate which specific experimental signals are needed to clearly differentiate the mirror-fermion model from other new-physics models. In particular, the case is made for a future large lepton collider with c.o.m. energies of roughly 4 TeV or higher.Comment: 30 Latex pages, 2 postscript figure

Quartic Gauge Couplings and the Radiation Zero in pp to l nu gamma gamma events at the LHC

We report a study of the process pp to l nu gamma gamma at CERN's Large Hadron Collider, using a leading order partonic-level event generator interfaced to the Pythia program for showering and hadronisation and a with a generic detector simulation. The process is sensitive to possible anomalous quartic gauge boson couplings of the form W W gamma gamma. It is shown how unitarity-safe limits may be placed on these anomalous couplings by applying a binned maximum likelihood fit to the distribution of the two-photon invariant mass, M(gamma gamma), below a cutoff of 1TeV. Assuming 30fb-1 of integrated luminosity, the expected limits are two orders of magnitude tighter than those available from LEP. It is also demonstrated how the Standard Model radiation zero feature of the qq to W gamma gamma process may be observed in the difference between the two-photon and charged lepton pseudo-rapidities.Comment: 9 pages, 7 figure