Search for W H associated production in 5.3 fb(-1) of p(p)over-bar collisions at the Fermilab Tevatron

We present a search for associated production of Higgs and W bosons in pp̄ collisions at a center of mass energy of s=1.96 TeV in 5.3 fb-1 of integrated luminosity recorded by the D0 experiment. Multivariate analysis techniques are applied to events containing one lepton, an imbalance in transverse energy, and one or two b-tagged jets to discriminate a potential WH signal from Standard Model backgrounds. We observe good agreement between data and expected backgrounds, and set an upper limit of 4.5 (at 95% confidence level and for mH=115 GeV) on the ratio of the WH cross section multiplied by the branching fraction of H→bb̄ to its Standard Model prediction, which is consistent with an expected limit of 4.8. © 2011 Elsevier B.V.

Measurement of the W boson mass with the D0 detector

We present a measurement of the W boson mass using data corresponding to 4.3fb -1 of integrated luminosity collected with the D0 detector during Run II at the Fermilab Tevatron pp̄ collider. With a sample of 1677394 W→eν candidate events, we measure M W=80.367±0. 026GeV. This result is combined with an earlier D0 result determined using an independent Run II data sample, corresponding to 1fb -1 of integrated luminosity, to yield M W=80.375±0.023GeV. © 2012 American Physical Society.

Studies of nucleon resonance structure in exclusive meson electroproduction

Studies of the structure of excited baryons are key factors to the N* program at Jefferson Lab (JLab). Within the first year of data taking with the Hall B CLAS12 detector following the 12 GeV upgrade, a dedicated experiment will aim to extract the N* electrocouplings at high photon virtualities Q 2. This experiment will allow exploration of the structure of N* resonances at the highest photon virtualities ever achieved, with a kinematic reach up to Q2 = 12 GeV2. This high-Q 2 reach will make it possible to probe the excited nucleon structures at distance scales ranging from where effective degrees of freedom, such as constituent quarks, are dominant through the transition to where nearly massless bare-quark degrees of freedom are relevant. In this document, we present a detailed description of the physics that can be addressed through N* structure studies in exclusive meson electroproduction. The discussion includes recent advances in reaction theory for extracting N* electrocouplings from meson electroproduction off protons, along with Quantum Chromodynamics (QCD)-based approaches to the theoretical interpretation of these fundamental quantities. This program will afford access to the dynamics of the nonperturbative strong interaction responsible for resonance formation, and will be crucial in understanding the nature of confinement and dynamical chiral symmetry breaking in baryons, and how excited nucleons emerge from QCD. © 2013 World Scientific Publishing Company.

Measurement of the p(p)over-bar -> W plus b plus X production cross section at root s=1.96 TeV D0 Collaboration

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)