11914733
Search for invisible decays of Higgs bosons in the vector boson fusion and associated ZH production modes
A search for invisible decays of Higgs bosons is performed using the vector boson fusion and associated ZH production modes. In the ZH mode, the Z boson is required to decay to a pair of charged leptons or a $$\mathrm {b}\overline{\mathrm {b}}$$bb¯ quark pair. The searches use the 8┬á$$\text {TeV}$$TeV pp collision dataset collected by the CMS detector at the LHC, corresponding to an integrated luminosity of up to 19.7┬á$$\text {fb}^{-1}$$fb-1. Certain channels include data from 7┬á$$\text {TeV}$$TeV collisions corresponding to an integrated luminosity of 4.9┬á$$\text {fb}^{-1}$$fb-1. The searches are sensitive to non-standard-model invisible decays of the recently observed Higgs boson, as well as additional Higgs bosons with similar production modes and large invisible branching fractions. In all channels, the observed data are consistent with the expected standard model backgrounds. Limits are set on the production cross section times invisible branching fraction, as a function of the Higgs boson mass, for the vector boson fusion and ZH production modes. By combining all channels, and assuming standard model Higgs boson cross sections and acceptances, the observed (expected) upper limit on the invisible branching fraction at $$m_\mathrm {H}=125$$mH=125┬á$$\text {GeV}$$GeV is found to be 0.58┬á(0.44) at 95┬á% confidence level. We interpret this limit in terms of a Higgs-portal model of dark matter interactions.
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.
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.
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.
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}.
189846889
The CDF intermediate silicon layers detector
SummaryThe Intermediate Silicon Layers detector (ISL) was proposed as a part of the upgraded CDF detector at the RUN-II of the Tevatron pp Collider at Fermilab, scheduled to start in year 2000. The ISL is a large-radius (20–30 cm) silicon tracker with a total active area of about 3.5 m2. Locatedin the region between the Silicon Vertex Detector (SVX II) andthe Central Outer Tracker, the ISL will allow tracking in the forwardregion andsignificantly improve it in the central area. Together with the SVX II the ISL forms a standalone, 3D silicon tracker. The challenge is to build a low-cost device which provides precise 3D tracking in a = 2 m long area with a minimal amount of material for the supporting structure. The conceptual design and the status of the project are reviewed.
9604492
High-resolution CMB power spectrum from the complete ACBAR data set
In this paper, we present results from the complete set of cosmic microwave background (CMB) radiation temperature anisotropy observations made with the Arcminute Cosmology Bolometer Array Receiver (ACBAR) operating at 150 GHz. We include new data from the final 2005 observing season, expanding the number of detector hours by 210% and the sky coverage by 490% over that used for the previous ACBAR release. As a result, the band-power uncertainties have been reduced by more than a factor of two on angular scales encompassing the third to fifth acoustic peaks as well as the damping tail of the CMB power spectrum. The calibration uncertainty has been reduced from 6% to 2.1% in temperature through a direct comparison of the CMB anisotropy measured by ACBAR with that of the dipole-calibrated WMAP5 experiment. The measured power spectrum is consistent with a spatially flat, ΛCDM cosmological model. We include the effects of weak lensing in the power spectrum model computations and find that this significantly improves the fits of the models to the combined ACBAR+WMAP5 power spectrum. The preferred strength of the lensing is consistent with theoretical expectations. On fine angular scales, there is weak evidence (1.1σ) for excess power above the level expected from primary anisotropies. We expect any excess power to be dominated by the combination of emission from dusty protogalaxies and the Sunyaev-Zel'dovich effect (SZE). However, the excess observed by ACBAR is significantly smaller than the excess power at l > 2000 reported by the CBI experiment operating at 30 GHz. Therefore, while it is unlikely that the CBI excess has a primordial origin; the combined ACBAR and CBI results are consistent with the source of the CBI excess being either the SZE or radio source contamination.
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.
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.
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.
16229687
Sunyaev-Zeldovich Observations of Massive Clusters of Galaxies
We present detections of the Sunyaev‐Zeldovich Effect (SZE) at 150GHz and 275GHz for the X‐ray luminous z=0.299 cluster 1E0657‐67. These observations were obtained as part of an X‐ray, weak lensing, and SZE survey of nearby X‐ray bright clusters. The SZE maps were made with the ACBAR (150, 210, 275 GHz) bolometer array installed at the Viper telescope located at the South Pole. We also present preliminary results from a blind SZE cluster survey.