125107038
The effect of dead-timeless silicon strip readout at CDF II
The Run IIa CDF Silicon Upgrade has recently finished installation. The detector uses revision D of the SVX3 readout IC. This final revision incorporated new features in order to improve the potential of dead-timeless operation. This paper describes measurements of dead-timeless effects on silicon strip readout on the test bench. This paper also describes tests of the dynamic pedestal subtraction circuitry, which is shown to improve greatly the dead-timeless performance of the silicon systems.
40497104
Performance of CMS muon reconstruction in $pp$ collision events at $\sqrt{s}=7$ TeV
The performance of muon reconstruction, identification, and triggering in CMS has been studied using 40 inverse picobarns of data collected in pp collisions at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection criteria covering a wide range of physics analysis needs have been examined. For all considered selections, the efficiency to reconstruct and identify a muon with a transverse momentum pT larger than a few GeV is above 95% over the whole region of pseudorapidity covered by the CMS muon system, abs(eta)<2.4, while the probability to misidentify a hadron as a muon is well below 1%. The efficiency to trigger on single muons with pT above a few GeV is higher than 90% over the full eta range, and typically substantially better. The overall momentum scale is measured to a precision of 0.2% with muons from Z decays. The transverse momentum resolution varies from 1% to 6% depending on pseudorapidity for muons with pT below 100 GeV and, using cosmic rays, it is shown to be better than 10% in the central region up to pT = 1 TeV. Observed distributions of all quantities are well reproduced by the Monte Carlo simulation.
45263794
Top quark mass measurement using the template method in the lepton + jets channel at CDF II
This article presents a measurement of the top quark mass using the CDF II detector at Fermilab. Colliding beams of protons and antiprotons at Fermilab's Tevatron ({radical}(s)=1.96 TeV) produce top/antitop pairs, which decay to W{sup +}W{sup -}bb; events are selected where one W decays to hadrons and the other W decays to either e or {mu} plus a neutrino. The data sample corresponds to an integrated luminosity of approximately 318 pb{sup -1}. A total of 165 tt events are separated into four subsamples based on jet transverse energy thresholds and the number of b jets identified by reconstructing a displaced vertex. In each event, the reconstructed top quark invariant mass is determined by minimizing a {chi}{sup 2} for the overconstrained kinematic system. At the same time, the mass of the hadronically decaying W boson is measured in the same event sample. The observed W boson mass provides an in situ improvement in the determination of the hadronic jet energy scale. A simultaneous likelihood fit of the reconstructed top quark masses and the W boson invariant masses in the data sample to distributions from simulated signal and background events gives a top quark mass of 173.5{sub -3.8}{sup +3.9} GeV/c{sup 2}.
108512063
Status report of the intermediate silicon layers detector at CDFII
The Intermediate Silicon Layers detector (ISL) is a large radius silicon tracker, installed in the CDF detector for the RUN II of the Tevatron Collider. With almost 4 m 2 of double-sided silicon sensors and 300,000 electronic channels it represents the biggest system of this kind ever built. The construction and installation phases, the performed quality assurance tests as well as the problems encountered are reviewed. RUN II of the Tevatron officially started on March 1st, 2001. Although the CDF silicon system is still being commissioned, results on the performance of the ISL detector obtained using the first data are presented. r 2002 Elsevier Science B.V. All rights reserved.
122731585
Search for $B^0_s \to \mu^+ \mu^-$ and $B^0 \to \mu^+ \mu^-$ decays
A search for the rare decays B_s to mu+ mu- and B^0 to mu^+ mu^- is performed in pp collisions at sqrt(s) = 7 TeV, with a data sample corresponding to an integrated luminosity of 5 inverse femtobarns collected by the CMS experiment at the LHC. In both decays, the number of events observed after all selection requirements is consistent with the expectation from background plus standard model signal predictions. The resulting upper limits on the branching fractions are Br(B_s to mu^+ mu^-) < 7.7E-9 and Br(B^0 to mu^+ mu^-) < 1.8E-9 at 95% confidence level.
121196052
First results of the ISIS1 beam test
Abstract The in situ storage image sensor (ISIS) is a monolithic active pixel sensor with memory cells in each pixel. The memory cells are implemented as a CCD register. This and other features of the sensor make the ISIS an excellent device for detectors that will be used at the International linear collider (ILC), an electron-positron accelerator with a proposed centre-of-mass energy of around 500 GeV. The sensor can be made very thin while retaining a high signal-to-noise ratio. The memory cells can be read out between bunch trains at a relatively low clock speed, hence limiting power consumption. The actual signal charge is stored in potential wells and not on capacitors, minimizing the sensitivity to electromagnetic interference. This paper presents the results of the first beam test of the first ISIS prototype. The measurements made include the signal-to-noise ratio, position resolution and efficiency.
17494605
Improved Measurements of the CMB Power Spectrum with ACBAR
We report improved measurements of temperature anisotropies in the cosmic microwave background (CMB) radiation made with the Arcminute Cosmology Bolometer Array Receiver (ACBAR). In this paper, we use a new analysis technique and include 30% more data from the 2001 and 2002 observing seasons than the first release to derive a new set of band-power measurements with significantly smaller uncertainties. The planet-based calibration used previously has been replaced by comparing the flux of RCW 38 as measured by ACBAR and BOOMERANG to transfer the WMAP-based BOOMERANG calibration to ACBAR. The resulting power spectrum is consistent with the theoretical predictions for a spatially flat, dark energy-dominated ΛCDM cosmology, including the effects of gravitational lensing. Despite the exponential damping on small angular scales, the primary CMB fluctuations are detected with a signal-to-noise ratio of greater than 4, up to multipoles of l = 2000. This increase in the precision of the fine-scale CMB power spectrum leads to only a modest decrease in the uncertainties on the parameters of the standard cosmological model. At high angular resolution, secondary anisotropies are predicted to be a significant contribution to the measured anisotropy. A joint analysis of the ACBAR results at 150 GHz and the CBI results at 30 GHz in the multipole range 2000 < l < 3000 shows that the power, reported by CBI in excess of the predicted primary anisotropy, has a frequency spectrum consistent with the thermal Sunyaev-Zel'dovich effect and inconsistent with primary CMB. The results reported here are derived from a subset of the total ACBAR data set; the final ACBAR power spectrum at 150 GHz will include 3.7 times more effective integration time and 6.5 times more sky coverage than is used here.
15115110
First Results From an X-Ray, Weak Lensing and Sunyaev-Zeldovich Effect Survey of Nearby Clusters: Abell 3266.
As part of a combined Sunyaev-Zeldovich Effect (SZE), X-ray and weak lensing survey of low redshift (z<0.1) X-ray clusters, we present SZE images of the z=0.059 X-ray cluster Abell 3266 at three observing frequencies (150, 220, 275 GHz) and after the spectral subtraction of primary Cosmic Microwave Background (CMB) anisotropies. These images were generated using the ACBAR bolometer array operated on the Viper telescope at the South Pole. The multi-frequency data from ACBAR should allow us to overcome one of the main obstacles facing the analysis of SZE observations of nearby clusters, i.e. contamination from primary Cosmic Microwave Background (CMB) anisotropies.