424 research outputs found
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Search for Lepton Flavor Violating Decays tau--->l-Ks0 with the BABAR Experiment
A search for the lepton flavor violating decays tau--->l-KS0 (l=e or mu) has been performed using a data sample corresponding to an integrated luminosity of 469¿¿fb[superscript -1], collected with the BABAR detector at the SLAC PEP-II e+e- asymmetric energy collider. No statistically significant signal has been observed in either channel and the estimated upper limits on branching fractions are B(tau--->e-KS0)mu-KS0)<4.0×10[superscript -8] at 90% confidence level
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Measurement of the tau(-)-> K-pi(0)nu(tau) branching fraction
A measurement of the tau(-)-> K-pi(0)nu(tau) branching fraction has been made using 230.2 fb(-1) of data recorded by the BABAR detector at the PEP-II e(+)e(-) collider, located at the Stanford Linear Accelerator Center (SLAC), at a center-of-mass energy root s close to 10.58 GeV. We measure B(tau(-)-> K-pi(0)nu(tau))=(0.416 +/- 0.003(stat)+/- 0.018(syst))%
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Search for supersymmetry with jets, missing transverse momentum and at least one hadronically decaying t lepton in proton–proton collisions at vs = 7 TeV with the ATLAS detector
A search for production of supersymmetric particles in final states containing jets, missing transverse momentum, and at least one hadronically decaying t lepton is presented. The data were recorded by the ATLAS experiment in v s = 7 TeV proton–proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 2.05 fb-1 of data. The results are interpreted in the context of gauge mediated supersymmetry breaking models with Mmess = 250 TeV, N5 = 3, µ > 0, and Cgrav = 1. The production of supersymmetric particles is excluded at 95% C.L. up to a supersymmetry breaking scale ? = 30 TeV, independent of tanß, and up to ? = 43 TeV for large tanß
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Search for supersymmetric particles in events with lepton pairs and large missing transverse momentum in vs = 7 TeV proton-proton collisions with the ATLAS experiment
Results are presented of searches for the production of supersymmetric particles decaying into final states with missing transverse momentum and exactly two isolated leptons in vs = 7 TeV proton–proton collisions at the Large Hadron Collider. Search strategies requiring lepton pairs with identical-sign or opposite-sign electric charges are described. In a data sample corresponding to an integrated luminosity of 35 pb(-1) collected with the ATLAS detector, no significant excesses are observed. Based on specific benchmark models, limits are placed on the squark mass between 450 and 690 GeV for squarks approximately degenerate in mass with gluinos, depending on the supersymmetric mass hierarchy considered
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Measurement of the t-??p-p+p-?t branching fraction and a search for a second-class current in the t-??'(958)p-?t decay
The t-??p-p+p-?t decay with the ???? mode is studied using 384??fb-1 of data collected by the BABAR detector. The branching fraction is measured to be (1.60±0.05±0.11)×10-4. It is found that t-?f1(1285)p-?t??p-p+p-?t is the dominant decay mode with a branching fraction of (1.11±0.06±0.05)×10-4. The first error on the branching fractions is statistical and the second systematic. Note that no particle identification algorithm is applied to the charged tracks to distinguish pions from kaons. In addition, a 90% confidence level upper limit on the branching fraction of the t-??'(958)p-?t decay is measured to be 7.2×10-6. This last decay proceeds through a second-class current and is expected to be forbidden in the limit of isospin symmetry
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Measurement of time-dependent CP asymmetries in B-0 -> D-(*)+/-pi(-/+) decays and constraints on sin(2 beta+gamma)
We present a measurement of CP-violating asymmetries in fully reconstructed B-0-->D((*)+/-)pi(-/+) decays in approximately 88x10(6) Y(4S)-->B (B) over bar decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. From a time-dependent maximum-likelihood fit we obtain the following for the CP-violating parameters: a=-0.022+/-0.038 (stat)+/-0.020 (syst), a(*)=-0.068+/-0.038 (stat)+/-0.020 (syst), c(lep)=+0.025+/-0.068 (stat)+/-0.033 (syst), and c(lep)(*)=+0.031+/-0.070 (stat)+/-0.033 (syst). Using other measurements and theoretical assumptions we interpret the results in terms of the angles of the Cabibbo-Kobayashi-Maskawa unitarity triangle, and find parallel tosin(2beta+gamma)parallel to>0.69 at 68% confidence level. We exclude the hypothesis of no CP violation [sin(2beta+gamma)=0] at 83% confidence level
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Search for lepton flavor violation in the decay tau(+/-)-> e(+/-)gamma
A search for the nonconservation of lepton flavor in the decay tau(+/-)-> e(+/-)gamma has been performed with 2.07x10(8) e(+)e(-)->tau(+)tau(-) events collected by the BABAR detector at the SLAC PEP II storage ring at a center-of-mass energy near 10.58 GeV. We find no evidence for a signal and set an upper limit on the branching ratio of B(tau(+/-)-> e(+/-)gamma)< 1.1x10(-7) at 90% confidence level
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Measurement of the B-0 meson lifetime with partial reconstruction of B-0 -> D*(-)pi(+) and B-0 -> D*(-)rho(+) decays
The neutral B meson lifetime is measured with the data collected by the BABAR detector at the PEP-II storage ring during the years 1999 and 2000, with a total integrated luminosity of 20.7 fb(-1). The decays B-0 --> D*- pi(+) and B-0 --> D*- rho(+) are selected with a partial-reconstruction technique, yielding samples of 6970 6240 and 55206250 signal events, respectively. With these events, the B-0 lifetime is measured to be 1.533 +/-0.034 (stat) +/-0.038 (syst) ps. This measurement serves as a test and validation of procedures required to measure the CP violation parameter sin(2beta+gamma) with partial reconstruction of these modes
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Readiness of the ATLAS liquid argon calorimeter for LHC collisions
The ATLAS liquid argon calorimeter has been operating continuously since August 2006. At this time, only part of the calorimeter was readout, but since the beginning of 2008, all calorimeter cells have been connected to the ATLAS readout system in preparation for LHC collisions. This paper gives an overview of the liquid argon calorimeter performance measured in situ with random triggers, calibration data, cosmic muons, and LHC beam splash events. Results on the detector operation, timing performance, electronics noise, and gain stability are presented. High energy deposits from radiative cosmic muons and beam splash events allow to check the intrinsic constant term of the energy resolution. The uniformity of the electromagnetic barrel calorimeter response along eta (averaged over phi) is measured at the percent level using minimum ionizing cosmic muons. Finally, studies of electromagnetic showers from radiative muons have been used to cross-check the Monte Carlo simulation. The performance results obtained using the ATLAS readout, data acquisition, and reconstruction software indicate that the liquid argon calorimeter is well-prepared for collisions at the dawn of the LHC era
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Commissioning of the ATLAS Muon Spectrometer with cosmic rays
The ATLAS detector at the Large Hadron Collider has collected several hundred million cosmic ray events during 2008 and 2009. These data were used to commission the Muon Spectrometer and to study the performance of the trigger and tracking chambers, their alignment, the detector control system, the data acquisition and the analysis programs. We present the performance in the relevant parameters that determine the quality of the muon measurement. We discuss the single element efficiency, resolution and noise rates, the calibration method of the detector response and of the alignment system, the track reconstruction efficiency and the momentum measurement. The results show that the detector is close to the design performance and that the Muon Spectrometer is ready to detect muons produced in high energy proton-proton collisions
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