Flavor Physics in the Quark Sector
ArXiv 0907.5386 (2009)
Abstract:
One of the major challenges of particle physics has been to gain an in-depth understanding of the role of quark flavor and measurements and theoretical interpretations of their results have advanced tremendously: apart from masses and quantum numbers of flavor particles, there now exist detailed measurements of the characteristics of their interactions allowing stringent tests of Standard Model predictions. Among the most interesting phenomena of flavor physics is the violation of the CP symmetry that has been subtle and difficult to explore. Till early 1990s observations of CP violation were confined to neutral $K$ mesons, but since then a large number of CP-violating processes have been studied in detail in neutral $B$ mesons. In parallel, measurements of the couplings of the heavy quarks and the dynamics for their decays in large samples of $K, D$, and $B$ mesons have been greatly improved in accuracy and the results are being used as probes in the search for deviations from the Standard Model. In the near future, there will be a transition from the current to a new generation of experiments, thus a review of the status of quark flavor physics is timely. This report summarizes the results of the current generation of experiments that is about to be completed and it confronts these results with the theoretical understanding of the field.Search for excited quarks in ep collisions at HERA
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 678:4 (2009) 335-343
Abstract:
A search for excited quarks is performed using the full e ± p data sample collected by the H1 experiment at HERA, corresponding to a total integrated luminosity of 475 pb - 1. The electroweak decays of excited quarks q * → q γ, q * → q Z and q * → q W with subsequent hadronic or leptonic decays of the W and Z bosons are considered. No evidence for first generation excited quark production is found. Mass dependent exclusion limits on q * production cross sections and on the ratio f / Λ of the coupling to the compositeness scale are derived within gauge mediated models. These limits extend the excluded region compared to previous excited quark searches. © 2009 Elsevier B.V.Search for the production of narrow tb[over] resonances in 1.9 fb;{-1} of pp[over] collisions at sqrt[s] = 1.96 TeV.
Phys Rev Lett 103:4 (2009) 041801
Abstract:
We present new limits on resonant tb[over] production in pp[over] collisions at sqrt[s] = 1.96 TeV, using 1.9 fb;{-1} of data recorded with the CDF II detector at the Fermilab Tevatron. We reconstruct a candidate tb[over] mass in events with a lepton, neutrino candidate, and two or three jets, and search for anomalous tb[over] production as modeled by W;{'} --> tb[over]. We set a new limit on a right-handed W;{'} with standard model-like coupling, excluding any mass below 800 GeV/c;{2} at 95% C.L. The cross section for any narrow, resonant tb[over] production between 750 and 950 GeV/c;{2} is found to be less than 0.28 pb at 95% C.L. We also present an exclusion of the W;{'} coupling strength versus W;{'} mass over the range 300-950 GeV/c;{2}.Observation of new charmless decays of bottom hadrons.
Phys Rev Lett 103:3 (2009) 031801
Abstract:
We search for new charmless decays of neutral b hadrons to pairs of charged hadrons, using 1 fb(-1) of data collected by the CDF II detector at the Fermilab Tevatron. We report the first observation of the Bs0-->K-pi+ decay and measure B(Bs0-->K-pi+)=(5.0+/-0.7(stat)+/-0.8(syst))x10(-6). We also report the first observation of charmless b-baryon decays, and measure B(Lambdab0-->ppi-)=(3.5+/-0.6(stat)+/-0.9(syst))x10(-6) and B(Lambdab0-->pK-)=(5.6+/-0.8(stat)+/-1.5(syst))x10(-6). No evidence is found for other modes, and we set the limit B(Bs0-->pi+pi;-)<1.2x10(-6) at 90% C.L.Search for long-lived massive charged particles in 1.96 TeV pp collisions.
Phys Rev Lett 103:2 (2009) 021802