Particle identification with the LHCb RICH system
NUCL INSTRUM METH A 563:2 (2006) 326-332
Abstract:
The LHCb experiment uses a Ring Imaging Cherenkov (RICH) system to provide particle identification over the momentum range 2-10OGeV/c. Two RICH detectors are employed. The upstream detector, RICH 1, utilizes both aerogel and C4F10 gas radiators whilst the downstream RICH 2 uses a CF4 gas radiator. The RICH 2 detector has been fabricated and is installed in the LHCb interaction region; RICH 1 has a programme of phased design and construction. Novel Hybrid Photon Detectors (HPDs) have been developed in collaboration with industry to detect the Cherenkov photons in the wavelength range 200-600 nm. The HPDs are enclosed in iron shielding and Mumetal cylinders to allow operation in magnetic fields up to 50 mT. The performance of pre-series HPDs and the results obtained from a particle test beam using the full LHCb readout chain is presented. The production of a total of 484 HPDs required for the two RICH detectors has recently commenced. The expected performance of the LHCb RICH system, obtained from realistic simulation, is described. (c) 2006 Elsevier B.V. All rights reserved.Measurement of the Bc+ meson lifetime using the decay mode Bc+ --> J/Psie+nue.
Phys Rev Lett 97:1 (2006) 012002
Abstract:
We present a measurement of the Bc+ meson lifetime in the decay mode Bc+ --> J/Psie+nue using the Collider Detector at Fermilab II detector at the Fermilab Tevatron Collider. From a sample of about of 360 pb(-1) of pp collisions at square root of s = 1.96 TeV, we reconstruct J/Psie+ pairs with invariant mass in the kinematically allowed range 4< M(J/Psie) < 6 GeV/c2. A fit to the decay-length distribution of 238 signal events yields a measured Bc+ meson lifetime of 0.463(-0.065)(+0.073)(stat) +/- 0.036(syst) ps.Measurement of the top quark mass using template methods on dilepton events in pp̄ collisions at s=1.96TeV
Physical Review D Particles Fields Gravitation and Cosmology 73:11 (2006)
Abstract:
We describe a measurement of the top quark mass from events produced in pp̄ collisions at a center-of-mass energy of 1.96 TeV, using the Collider Detector at Fermilab. We identify tt̄ candidates where both W bosons from the top quarks decay into leptons (eν, μν, or τν) from a data sample of 360pb-1. The top quark mass is reconstructed in each event separately by three different methods, which draw upon simulated distributions of the neutrino pseudorapidity, tt̄ longitudinal momentum, or neutrino azimuthal angle in order to extract probability distributions for the top quark mass. For each method, representative mass distributions, or templates, are constructed from simulated samples of signal and background events, and parametrized to form continuous probability density functions. A likelihood fit incorporating these parametrized templates is then performed on the data sample masses in order to derive a final top quark mass. Combining the three template methods, taking into account correlations in their statistical and systematic uncertainties, results in a top quark mass measurement of 170.1±6.0(stat.)±4.1(syst.) GeV/c2. © 2006 The American Physical Society.Observation of Bs0→ψ(2S) and measurement of the ratio of branching fractions B(Bs0→ψ(2S) /B(Bs0→J/ψ)
Physical Review Letters 96:23 (2006)
Abstract:
We report the first observation of Bs0→ψ(2S) decay in pp̄ collisions at s= 1.96 TeV using 360 pb-1 of data collected by the CDF II detector at the Fermilab Tevatron. We observe 20.2±5.0 and 12.3±4.1 Bs0→ψ(2S) candidates, in ψ(2S)→μ+μ- and ψ(2S)→J/ψπ+π- decay modes, respectively. We present a measurement of the relative branching fraction B(Bs0→ψ(2S) /B(Bs0→J/ψ)=0.52±0.13(stat)±0.04(syst)±0.06(BR) using the ψ(2S)→μ+μ- decay mode. © 2006 The American Physical Society.Observation of B(0)(s)-->Psi(2S)Phi and measurement of the ratio of branching fractions Beta(B(0)(s)-->Psi(2S)Phi)/Beta(B(0)(s)-->J/PsiPhi).
Phys Rev Lett 96:23 (2006) 231801