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.
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.
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}.
841502
Observation of the diphoton decay of the Higgs boson and measurement of its properties
Observation of the diphoton decay mode of the recently discovered Higgs boson and measurement of some of its properties are reported. The analysis uses the entire dataset collected by the CMS experiment in proton-proton collisions during the 2011 and 2012 LHC running periods. The data samples correspond to integrated luminosities of 5.1$$\,\text {fb}^\text {-1}$$fb-1at $$\sqrt{s}=7\,\text {TeV}\,$$s=7TeV and 19.7$$\,\text {fb}^\text {-1}$$fb-1at 8$$\,\text {TeV}$$TeV . A clear signal is observed in the diphoton channel at a mass close to 125$$\,\text {GeV}$$GeV with a local significance of $$5.7\,\sigma $$5.7σ, where a significance of $$5.2\,\sigma $$5.2σ is expected for the standard model Higgs boson. The mass is measured to be $$124.70\pm 0.34\,\text {GeV} \,=124.70\pm 0.31\,\text {(stat)}\,\pm 0.15\,\text {(syst)}\,\,\text {GeV} \,$$124.70±0.34GeV=124.70±0.31(stat)±0.15(syst)GeV , and the best-fit signal strength relative to the standard model prediction is $$1.14^\mathrm{+0.26}_{-0.23}=1.14\pm 0.21\,\text {(stat)}\,$$1.14-0.23+0.26=1.14±0.21(stat)$$^\mathrm{+0.09}_{-0.05}\,\text {(syst)}\,$$-0.05+0.09(syst)$$^\mathrm{+0.13}_{-0.09}\,\text {(theo)}\,$$-0.09+0.13(theo). Additional measurements include the signal strength modifiers associated with different production mechanisms, and hypothesis tests between spin-0 and spin-2 models.
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.
2976215
Imaging the Sunyaev Zel'dovich Effect using ACBAR on Viper
During 2001 and 2002, observations of several X-ray bright clusters of galaxies were conducted using the ACBAR Bolometer Array on the South Pole Viper telescope. A multi-frequency analysis of these clusters is currently underway. This multi-frequency analysis includes 150, 220 and 275 GHz data from ACBAR, X-ray imaging and spectroscopy from Chandra and XMM-Newton, and weak lensing data from the CTIO 4m Blanco telescope. We describe here how ACBAR can be used to create fully sampled cluster images and present such images for four of the clusters in our sample; Abell 3266, Abell 3827, Abell S1063 and 1E0657-56. In these images, the Sunyaev-Zel'dovich Effect is clearly detected.
14900939
The Arecibo Legacy Fast ALFA survey III: H I source catalog of the northern Virgo cluster region
We present the first installment of H I sources extracted from the Arecibo Legacy Fast ALFA (ALFALFA) extragalactic survey, initiated in 2005. Sources have been extracted from three-dimensional spectral data cubes exploiting a matched filtering technique and then examined interactively to yield global H I parameters. A total of 730 H I detections are cataloged within the solid angle 11h44m 6.5, (2) high-velocity clouds in the Milky Way or its periphery, and (3) signals of lower S/N (to ~4.5) which coincide spatially with an optical object of known similar redshift. Although this region of the sky has been heavily surveyed by previous targeted observations based on optical flux- or size-limited samples, 69% of the extracted sources are newly reported H I detections. The resulting positional accuracy of H I sources is dependent on S/N: it averages 24'' (20'' median) for all sources with S/N > 6.5 and is of order ~17'' (14'' median) for signals with S/N > 12. The median redshift of the sample is ~7000 km s-1, and its distribution reflects the known local large-scale structure including the Virgo Cluster and the void behind it, the A1367-Coma supercluster at cz ~ 7000 km s-1, and a third, more distant overdensity at cz ~ 13,000 km s-1. Distance uncertainties in and around the Virgo Cluster perturb the derived H I mass distribution. Specifically, an apparent deficiency of the lowest H I mass objects can be attributed, at least in part, to the incorrect assignment of some foreground objects to the cluster distance. Several extended H I features are found in the vicinity of the Virgo Cluster. A small percentage (6%) of H I detections have no identifiable optical counterpart, more than half of which are high-velocity clouds in the Milky Way vicinity; the remaining 17 objects do not appear connected to or associated with any known galaxy. Based on these initial results, ALFALFA is expected to fulfill, and even exceed, its predicted performance objectives in terms of the number and quality of H I detections.