The lifetime of the tau lepton is measured using data collected in 1994 by the L3 detector at LEP. The precise track position information of the Silicon Microvertex Detector is exploited. The tau ...lepton lifetime is determined from the signed impact parameter distribution for 30 322 tau decays into one charged particle and from the decay length distribution for 3891 tau decays into three charged particles. Combining the two methods we obtain $\tau_{\tau}$ = 290.1 $\pm$ 4.0 fs.
Beam spot position measurement at the LEP collider Bourilkov, D; Brigljevic, V; Filthaut, F ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/1997, Letnik:
394, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A precise knowledge of the beam spot position is required for many physics topics at LEP2. The movement of the beam spot is studied at LEP1 using beam orbit monitors close to the interaction points ...and compared with measurements from tracks produced in e
+e
− collisions. The beam orbit monitors are found to follow the beam spot position well, particularly when corrected for movements of nearby quadrupole magnets. Data from the LEP high energy run of November 1995 are also analysed, and projections made for the prospects at LEP2.
A search for pair-production of first generation scalar leptoquarks is performed in the final state containing an electron, a neutrino, and at least two jets using proton-proton collision data at ...inline image. The data were collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 36 pb super(-1. The number of observed events is in good agreement with the predictions for standard model processes. Prior CMS results in the dielectron channel are combined with this electron + neutrino search. A 95% confidence level combined lower limit is set on the mass of a first generation scalar leptoquark at 339 GeV for beta=0.5, where beta is the branching fraction of the leptoquark to an electron and a quark. These results represent the most stringent direct limits to date for values of beta greater than 0.05.)
A measurement of the ratio of the inclusive 3-jet to 2-jet cross sections as a function of the total jet transverse momentum, H sub(T), in the range 0.2<H sub(T)<2.5 TeV is presented. The data have ...been collected at a proton-proton centre-of-mass energy of 7 TeV with the CMS detector at the LHC, and correspond to an integrated luminosity of 36 pb super(-1). Comparisons are made between the data and the predictions of different QCD-based Monte Carlo models for multijet production. All models considered in this study are consistent with the data for H sub(T)>0.5 TeV. This measurement extends to an H sub(T) range that has not been explored before.
A measurement of W gamma and Z gamma production in proton-proton collisions at inline imageinline image is presented. Results are based on a data sample recorded by the CMS experiment at the LHC, ...corresponding to an integrated luminosity of 36 pb super(-1. The electron and muon decay channels of the W and Z are used. The total cross sections are measured for photon transverse energy inline imageinline image and spatial separation from charged leptons in the plane of pseudorapidity and azimuthal angle Delta R(l, gamma )0.7, and with an additional dilepton invariant mass requirement of M) sub(l)l50 GeV for the Z gamma process. The following cross section times branching fraction values are found: inline imageinline image and inline imageinline image. These measurements are in agreement with standard model predictions. The first limits on anomalous WW gamma , ZZ gamma , and Z gamma gamma trilinear gauge couplings at inline imageinline image are set.
Performances of RPCs in the BaBar experiment Anulli, F.; Baldini, R.; Band, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2003, Letnik:
515, Številka:
1
Journal Article
Recenzirano
The BaBar experiment uses a big system based on RPC detectors to discriminate muons from pions and to identify neutral hadrons. About
2000
m
2
of RPC chambers have been working at SLAC since the end ...of 1998. We report on the performances of the RPC chambers focusing on new problems discovered in the RPC behaviour. These problems started very soon after the installation of the chambers on the detector when the high-ambient temperature triggered an increase of dark currents inside the chambers and a reduction of the efficiency. Careful analysis of the BaBar data and dedicated R&D efforts in the laboratory have helped to identify the main source of the trouble in the linseed oil varnish on the bakelite electrodes.
The BaBar instrumented flux return performance: lessons learned Anulli, F; Bagnasco, S; Baldini, R ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2002, Letnik:
494, Številka:
1
Journal Article
Recenzirano
The BaBar Collaboration has operated an instrumented flux return (IFR) system covering over
2000
m
2
with resistive plate chambers (RPCs) for nearly 3 years. The chambers are constructed of bakelite ...sheets separated by
2
mm
. The inner surfaces are coated with linseed oil. This system provides muon and neutral hadron detection for BaBar. Installation and commissioning were completed in 1998, and operation began mid-year 1999. While initial performance of the system reached design, over time, a significant fraction of the RPCs demonstrated significant degradation, marked by increased currents and reduced efficiency. A coordinated effort of investigations have identified many of the elements responsible for the degradation. This article presents our current understanding of the aging process of the BaBar RPCs along with the action plan to combat performance degradation of the IFR system.
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