135 research outputs found
Final measurement of mixing phase in the full CDF Run II data set
We report the final CDF measurement of the mixing phase, mean
lifetime, and decay-width difference through the fit of the time evolution of
flavor-tagged decays. The measurement is based
on the full data set of 1.96 TeV collisions collected between
February 2002 and September 2011 by the CDF experiment. The results are
consistent with the standard model and other experimental determinations and
are amongst the most precise to date.Comment: 3 pages, 2 figures, conference IFAE 201
On the resolution in a measurement of dijet invariant mass when searching for associated WZ production with CDF
We report on a number of simulation studies on how to improve the invariant mass resolution of a particle decaying into two large energy hadron jets. This is a preliminary step of an effort to observe associated WZ production. This process is extremely rare and competes with a large background, and any minor improvement in resolution deserves great attention.
These tools would be of interest in the study of many rare multi-jet processes. They are implemented here in a simulated measurement of decay (aiming eventually at a decay), in associated WZ (WH) production in \proton \antiproton\ collisions at \ecm = 1.96 TeV recorded by the CDF II experiment at the Fermilab Tevatron Collider.
We generate WZ events with an identified charged lepton, a large imbalance in transverse momentum, and at least two large transverse energy jets. We determine the sample selection cuts by studying jet energy dependence of signal and background. The main backgrounds, noticeably W+jets production, are modeled based on experimental data whenever possible. We first try to optimize the sensitivity to a jet-jet invariant mass peak by complementing the information provided by the CDF calorimeter with that of the tracker. For mis-measured calorimeter jets, and for jets fragmenting with a large charged-to-neutral ratio, the jet axis could be better measured in the tracker. As a consequence the dijet invariant mass could be better measured. The study starts by checking the best ever achievable improvement by adopting the primary parton direction as jet axis. This study is performed on a PHYTIA Monte Carlo in the simpler case of light decay quarks. Improvements in dijet mass resolution of the order of a few \% are obtained in a number of cases. Next we try to develop event-specific energy corrections for calorimeter jets. Again, improvements of the order of a few \% are obtained in a number of cases. The combination of these two methods indicates possible improvements in dijet mass resolution up to 5\%.,
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When the study is extended to using, rather than primary quark directions, tracker jet axes which are experimental observables, no real progress is predicted. However, the study is extended to event specific corrections to calorimeter jets based on information carried by observables in the event, including tracking. This study gives very interesting and promising indications: Resolution improves by . Criteria by which we select and merge jets due to final state radiation (FSR) are discussed, and the impact on dijet mass resolution of merging three jets to reconstruct W or Z in decay is studied
Measurement of the (eta c)(1S) production cross-section in proton-proton collisions via the decay (eta c)(1S) -> p(p)over-bar
The production of the state in proton-proton collisions is probed via its decay to the final state with the LHCb detector, in the rapidity range GeV/c. The cross-section for prompt production of mesons relative to the prompt cross-section is measured, for the first time, to be at a centre-of-mass energy TeV using data corresponding to an integrated luminosity of 0.7 fb, and at TeV using 2.0 fb. The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the and decays to the final state. In addition, the inclusive branching fraction of -hadron decays into mesons is measured, for the first time, to be , where the third uncertainty includes also the uncertainty on the inclusive branching fraction from -hadron decays. The difference between the and meson masses is determined to be MeV/c.The production of the state in proton-proton collisions is probed via its decay to the final state with the LHCb detector, in the rapidity range . The cross-section for prompt production of mesons relative to the prompt cross-section is measured, for the first time, to be at a centre-of-mass energy using data corresponding to an integrated luminosity of 0.7 fb , and at using 2.0 fb . The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the and decays to the final state. In addition, the inclusive branching fraction of -hadron decays into mesons is measured, for the first time, to be , where the third uncertainty includes also the uncertainty on the inclusive branching fraction from -hadron decays. The difference between the and meson masses is determined to be .The production of the state in proton-proton collisions is probed via its decay to the final state with the LHCb detector, in the rapidity range GeV/c. The cross-section for prompt production of mesons relative to the prompt cross-section is measured, for the first time, to be at a centre-of-mass energy TeV using data corresponding to an integrated luminosity of 0.7 fb, and at TeV using 2.0 fb. The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the and decays to the final state. In addition, the inclusive branching fraction of -hadron decays into mesons is measured, for the first time, to be , where the third uncertainty includes also the uncertainty on the inclusive branching fraction from -hadron decays. The difference between the and meson masses is determined to be MeV/c
A study of CP violation in B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays with D -> (KSK +/-)-K-0 pi(-/+) final states
A first study of CP violation in the decay modes and , where labels a or meson and labels a or meson, is performed. The analysis uses the LHCb data set collected in collisions, corresponding to an integrated luminosity of 3 fb. The analysis is sensitive to the CP-violating CKM phase through seven observables: one charge asymmetry in each of the four modes and three ratios of the charge-integrated yields. The results are consistent with measurements of using other decay modes
Measurement of Upsilon production in collisions at root s=2.76 TeV
The production of , and mesons decaying into the dimuon final state is studied with the LHCb detector using a data sample corresponding to an integrated luminosity of 3.3 collected in proton-proton collisions at a centre-of-mass energy of TeV. The differential production cross-sections times dimuon branching fractions are measured as functions of the transverse momentum and rapidity, over the ranges $p_{\rm T} Upsilon(1S) X) x B(Upsilon(1S) -> mu+mu-) = 1.111 +/- 0.043 +/- 0.044 nb, sigma(pp -> Upsilon(2S) X) x B(Upsilon(2S) -> mu+mu-) = 0.264 +/- 0.023 +/- 0.011 nb, sigma(pp -> Upsilon(3S) X) x B(Upsilon(3S) -> mu+mu-) = 0.159 +/- 0.020 +/- 0.007 nb, where the first uncertainty is statistical and the second systematic
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