Measurements of the top-quark mass using charged particle tracking
Physical Review D - Particles, Fields, Gravitation and Cosmology 81:3 (2010)
Abstract:
We present three measurements of the top-quark mass in the lepton plus jets channel with approximately 1.9fb-1 of integrated luminosity collected with the CDF II detector using quantities with minimal dependence on the jet energy scale. One measurement exploits the transverse decay length of b-tagged jets to determine a top-quark mass of 166.9-8.5+9.5(stat)±2. 9(syst)GeV/c2, and another the transverse momentum of electrons and muons from W-boson decays to determine a top-quark mass of 173.5-8.9+8.8(stat)±3. 8(syst)GeV/c2. These quantities are combined in a third, simultaneous mass measurement to determine a top-quark mass of 170.7±6.3(stat)±2. 6(syst)GeV/c2. © 2010 The American Physical Society.Search for supersymmetry with gauge-mediated breaking in diphoton events with missing transverse energy at CDF II.
Phys Rev Lett 104:1 (2010) 011801
Abstract:
We present the results of a search for supersymmetry with gauge-mediated breaking and chi(1)(0) --> gammaG in the gammagamma + missing transverse energy final state. In 2.6+/-0.2 fb(-1) of pp collisions at square root(s) = 1.96 TeV recorded by the CDF II detector we observe no candidate events, consistent with a standard model background expectation of 1.4+/-0.4 events. We set limits on the cross section at the 95% C.L. and place the world's best limit of 149 GeV/c2 on the chi(1)(0) mass at tau(chi(1)(0)) << 1 ns. We also exclude regions in the chi(1)(0) mass-lifetime plane for tau(chi(1)(0)) approximately < 2 ns.Aligning the CMS muon chambers with the muon alignment system during an extended cosmic ray run
Journal of Instrumentation 5:3 (2010)
Abstract:
The alignment system for the muon spectrometer of the CMS detector comprises three independent subsystems of optical and analog position sensors. It aligns muon chambers with respect to each other and to the central silicon tracker. System commissioning at full magnetic field began in 2008 during an extended cosmic ray run. The system succeeded in tracking muon detector movements of up to 18 mm and rotations of several milliradians under magnetic forces. Depending on coordinate and subsystem, the system achieved chamber alignment precisions of 140-350 μm and 30-200 μrad, close to the precision requirements of the experiment. Systematic errors on absolute positions are estimated to be 340-590 μm based on comparisons with independent photogrammetry measurements. © 2010 IOP Publishing Ltd and SISSA.Alignment of the CMS muon system with cosmic-ray and beam-halo muons
Journal of Instrumentation 5:3 (2010)
Abstract:
The CMS muon system has been aligned using cosmic-ray muons collected in 2008 and beam-halo muons from the 2008 LHC circulating beam tests. After alignment, the resolution of the most sensitive coordinate is 80 microns for the relative positions of superlayers in the same barrel chamber and 270 microns for the relative positions of endcap chambers in the same ring structure. The resolution on the position of the central barrel chambers relative to the tracker is comprised between two extreme estimates, 200 and 700 microns, provided by two complementary studies. With minor modifications, the alignment procedures can be applied using muons from LHC collisions, leading to additional significant improvements. © 2010 IOP Publishing Ltd and SISSA.Alignment of the CMS silicon tracker during commissioning with cosmic rays
Journal of Instrumentation 5:3 (2010)