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12,582 Matching Results
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$W$ boson polarization measurement in the $t\bar{t}$ dilepton channel using the CDF II Detector
We present a measurement of W boson polarization in top-quark decays in t{bar t} events with decays to dilepton final states using 5.1 fb{sup -1} integrated luminosity in p{bar p} collisions collected by the CDF II detector at the Tevatron. A simultaneous measurement of the fractions of longitudinal (f{sub 0}) and right-handed (f{sub +}) W bosons yields the results f{sub 0} = 0.71{sub -0.17}{sup +0.18}(stat) {+-} 0.06(syst) and f{sub +} = -0.07 {+-} 0.09(stat) {+-} 0.03(syst). Combining this measurement with our previous result based on single lepton final states, we obtain f{sub 0} = 0.84 {+-} 0.09(stat) {+-} 0.05(syst) and f{sub +} = -0.16 {+-} 0.05(stat) {+-} 0.04(syst). The results are consistent with standard model expectation.
Date:
May 1, 2012
Creator:
Aaltonen, T.; Alvarez Gonzalez, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A. et al.
Object Type:
Article
System:
The UNT Digital Library
Search for a low mass Standard Model Higgs boson in the $\tau-\tau$ decay channel in $p\bar{p}$ collisions at $\sqrt{s}$ = 1.96 TeV
We report on a search for the standard model Higgs boson decaying into pairs of {tau} leptons in p{bar p} collisions produced by the Tevatron at {radical}s = 1.96 TeV. The analyzed data sample was recorded by the CDFII detector and corresponds to an integrated luminosity of 6.0 fb{sup -1}. The search is performed in the final state with one {tau} decaying leptonically and the second one identified through its semi-hadronic decay. Since no significant excess is observed, a 95% credibility level upper limit on the production cross section times branching ratio to the {tau}{tau} final state is set for hypothetical Higgs boson masses between 100 and 150 GeV/c{sup 2}. For a Higgs boson of 120 GeV/c{sup 2} the observed (expected) limit is 14.6 (15.3) the predicted value.
Date:
January 1, 2012
Creator:
Aaltonen, T.; Phys., /Helsinki Inst. of; Alvarez Gonzalez, B.; Phys., /Oviedo U. /Cantabria Inst. of; Amerio, S.; /INFN, Padua et al.
Object Type:
Article
System:
The UNT Digital Library
Measurement of angular correlations of jets at sqrt(s)=1.96 TeV and determination of the strong coupling at high momentum transfers
None
Date:
July 1, 2012
Creator:
Abazov, V. M.
Object Type:
Article
System:
The UNT Digital Library
Search for the Higgs boson in lepton, tau and jets final states
None
Date:
November 1, 2012
Creator:
Abazov, V. M.
Object Type:
Article
System:
The UNT Digital Library
Measurement of the differential cross section $d\sigma/dt$ in elastic $p\bar{p}$ scattering at $\sqrt{s}=1.96$ TeV
We present a measurement of the elastic differential cross section differential cross section d{sigma}(p{bar p}{yields}p{bar p})/dt as a function of the four-momentum-transfer squared t. The data sample corresponds to an integrated luminosity of {approx}31 nb{sup -1} collected with the D0 detector using dedicated Tevatron p{bar p} Collider operating conditions at {radical}s = 1.96 TeV and covers the range 0.26 < |t| < 1.2 GeV{sup 2}. For |t| < 0.6 GeV{sup 2}, d{sigma}/dt is described by an exponential function of the form Ae{sup -b|t|} with a slope parameter b = 16.86 {+-} 0.10 (stat) {+-} 0.20 (syst) GeV{sup -2}. A change in slope is observed at |t| {approx} 0.6 GeV{sup 2}, followed by a more gradual |t| dependence with increasing values of |t|.
Date:
June 1, 2012
Creator:
Abazov, V. M.; Abbott, B.; Acharya, B. S.; Adams, M.; Adams, T.; Alexeev, G. D. et al.
Object Type:
Article
System:
The UNT Digital Library
Measurement of the $\Lambda_b^0$ lifetime in the exclusive decay $\Lambda_b^0 \to J/\psi \Lambda^0$ in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV
We measure the {Lambda}{sub b}{sup 0} lifetime in the fully reconstructed decay {Lambda}{sub b}{sup 0} {yields} J/{psi} {Lambda}{sup 0} using 10.4 fb{sup -1} of p{bar p} collisions collected with the D0 detector at {radical}s = 1.96 TeV. The lifetime of the topologically similar decay channel B{sup 0} {yields} J/{psi} K{sub S}{sup 0} is also measured. We obtain {tau} ({Lambda}{sub b}{sup 0}) = 1.303 {+-} 0.075 (stat.) {+-} 0.035 (syst.) ps and {tau} (B{sup 0}) = 1.508 {+-} 0.025 (stat.) {+-} 0.043 (syst.) ps. Using these measurements, we determine the lifetime ratio of {tau} ({Lambda}{sub b}{sup 0})/{tau} (B{sup 0}) = 0.864 {+-} 0.052 (stat.) {+-} 0.033 (syst.).
Date:
April 1, 2012
Creator:
Abazov, Victor Mukhamedovich & al., et
Object Type:
Article
System:
The UNT Digital Library
Observation of a narrow mass state decaying into $\Upsilon(1S) + \gamma$ in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV
Using data corresponding to an integrated luminosity of 1.3 fb{sup -1}, we observe a narrow mass state decaying into {Upsilon}(1S) + {gamma}, where the {Upsilon}(1S) meson is detected by its decay into a pair of oppositely charged muons, and the photon is identified through its conversion into an electron-positron pair. The significance of this observation is 5.6 standard deviations. The mass of the state is centered at 10.551 {+-} 0.014(stat.) {+-} 0.017(syst.) GeV/c{sup 2}, which is consistent with that of the state recently observed by the ATLAS Collaboration.
Date:
March 1, 2012
Creator:
Abazov, Victor Mukhamedovich & al., et
Object Type:
Article
System:
The UNT Digital Library
Search for the standard model Higgs boson in tau lepton pair final states
We present a search for the standard model Higgs boson in final states with an electron or muon and a hadronically decaying tau lepton in association with zero, one, or two or more jets using data corresponding to an integrated luminosity of up to 7.3 fb{sup -1} collected with the D0 detector at the Fermilab Tevatron collider. The analysis is sensitive to Higgs boson production via gluon gluon fusion, associated vector boson production, and vector boson fusion, and to Higgs boson decays to tau lepton pairs or W boson pairs. Observed (expected) limits are set on the ratio of 95% C.L. upper limits on the cross section times branching ratio, relative to those predicted by the Standard Model, of 14 (22) at a Higgs boson mass of 115 GeV and 7.7 (6.8) at 165 GeV.
Date:
March 1, 2012
Creator:
Abazov, Victor Mukhamedovich & al., et
Object Type:
Article
System:
The UNT Digital Library
Measurement of the top quark mass in $p \bar{p}$ collisions using events with two leptons
We present a measurement of the top quark mass (m{sub t}) in p{bar p} collisions at {radical}s = 1.96 TeV using t{bar t} events with two leptons (ee, e{mu} or {mu}{mu}) in the final state in 4.3 fb{sup -1} of data collected with the D0 detector at the Fermilab Tevatron collider. We analyze the kinematically underconstrained dilepton events by integrating over the neutrino rapidity distributions. We reduce the dominant systematic uncertainties from jet energy calibration using a correction obtained from t{bar t} {yields} {ell} + jets events. We also correct jets in simulated events to replicate the quark flavor dependence of the jet response in data. In combination with our previous analysis, we measure m{sub t} = 174.0 {+-} 2.4(stat) {+-} 1.4(syst) GeV.
Date:
January 1, 2012
Creator:
Abazov, Victor Mukhamedovich; /Dubna, JINR; Abbott, Braden Keim; U., /Oklahoma; Acharya, Bannanje Sripath; Inst., /Tata et al.
Object Type:
Article
System:
The UNT Digital Library
An Improved determination of the width of the top quark
We present an improved determination of the total width of the top quark, {Lambda}{sub t}, using 5.4 fb{sup -1} of integrated luminosity collected by the D0 Collaboration at the Tevatron p{bar p} Collider. The total width {Lambda}{sub t} is extracted from the partial decay width {Lambda}(t {yields} Wb) and the branching fraction {Beta}(t {yields} Wb). {Lambda}(t {yields} Wb) is obtained from the t-channel single top quark production cross section and {Beta}(t {yields} Wb) is measured in t{bar t} events. For a top mass of 172.5 GeV, the resulting width is {Lambda}{sub t} = 2.00{sub -0.43}{sup +0.47} GeV. This translates to a top-quark lifetime of {tau}{sub t} = (3.29{sub -0.63}{sup +0.90}) x 10{sup -25} s. We also extract an improved direct limit on the CKM matrix element 0.81 < |V{sub tb}| {le} 1 at 95% C.L. and a limit of |V{sub tb'}| < 0.59 for a high mass fourth generation bottom quark assuming unitarity of the fourth generation quark mixing matrix.
Date:
January 1, 2012
Creator:
Abazov, Victor Mukhamedovich; Abbott, Braden Keim; Acharya, Bannanje Sripath; Adams, Mark Raymond; Adams, Todd; Alexeev, Guennadi D. et al.
Object Type:
Article
System:
The UNT Digital Library
A measurement of the WZ and ZZ production cross sections using leptonic final states in 8.6 fb^{-1} of p\bar{p} collisions
We study the processes p{bar p} {yields} WZ {yields} {ell}{nu}{ell}{sup +}{ell}{sup -} and p{bar p} {yields} ZZ {yields} {ell}{sup +}{ell}{sup -}{nu}{bar {nu}}, where {ell} = e or {mu}. Using 8.6 fb{sup -1} of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron collider, we measure the WZ production cross section to be 4.50{sub -0.66}{sup +0.63} pb which is consistent with, but slightly above a prediction of the standard model. The ZZ cross section is measured to be 1.64 {+-} 0.46 pb, in agreement with a prediction of the standard model. Combination with an earlier analysis of the ZZ {yields} {ell}{sup +}{ell}{sup -}{ell}{sup +}{ell}{sup -} channel yields a ZZ cross section of 1.44{sub -0.34}{sup +0.35} pb.
Date:
January 1, 2012
Creator:
Abazov, Victor Mukhamedovich; Abbott, Braden Keim; Acharya, Bannanje Sripath; Adams, Mark Raymond; Adams, Todd; Alexeev, Guennadi D. et al.
Object Type:
Article
System:
The UNT Digital Library
Search for $WH$ associated production in $p \bar{p}$ collisions at $\sqrt{s}=1.96\,{\rm TeV}$
This report describes a search for associated production of W and Higgs bosons based on data corresponding to an integrated luminosity of L {approx} 5.3 fb{sup -1} collected with the D0 detector at the Fermilab Tevatron p{bar p} Collider. Events containing a W {yields} {ell}{nu} candidate (with {ell} corresponding to e or {mu}) are selected in association with two or three reconstructed jets. One or two of the jets are required to be consistent with having evolved from a b quark. A multivariate discriminant technique is used to improve the separation of signal and backgrounds. Expected and observed upper limits are obtained for the product of the WH production cross section and branching ratios and reported in terms of ratios relative to the prediction of the standard model as a function of the mass of the Higgs boson (M{sub H}). The observed and expected 95% C.L. upper limits obtained for an assumed M{sub H} = 115 GeV are, respectively, factors of 4.5 and 4.8 larger than the value predicted by the standard model.
Date:
March 1, 2012
Creator:
Abazov, Victor Mukhamedovich; Abbott, Braden Keim; Acharya, Bannanje Sripath; Adams, Mark Raymond; Adams, Todd; Alexeev, Guennadi D. et al.
Object Type:
Article
System:
The UNT Digital Library
AGR-2 Data Qualification Report for ATR Cycles 149B, 150A, 150B, 151A, and 151B
This report provides the data qualification status of AGR-2 fuel irradiation experimental data from Advanced Test Reactor (ATR) cycles 149B, 150A, 150B, 151A, and 151B), as recorded in the Nuclear Data Management and Analysis System (NDMAS). The AGR-2 data streams addressed include thermocouple temperatures, sweep gas data (flow rate, pressure, and moisture content), and fission product monitoring system (FPMS) data for each of the six capsules in the experiment. A total of 3,307,500 5-minute thermocouple and sweep gas data records were received and processed by NDMAS for this period. There are no AGR-2 data for cycle 150A because the experiment was removed from the reactor. Of these data, 82.2% were determined to be Qualified based on NDMAS accuracy testing and data validity assessment. There were 450,557 Failed temperature records due to thermocouple failures, and 138,528 Failed gas flow records due to gas flow cross-talk and leakage problems that occurred in the capsules after cycle 150A. For FPMS data, NDMAS received and processed preliminary release rate and release-to-birth rate ratio (R/B) data for the first three reactor cycles (cycles 149B, 150B, and 151B). This data consists of 45,983 release rate records and 45,235 R/B records for the 12 radionuclides reported. The …
Date:
June 1, 2012
Creator:
Abbott, Michael L. & Pham, Binh T.
Object Type:
Report
System:
The UNT Digital Library
The Dark Energy Spectrometer (DESpec): A Multi-Fiber Spectroscopic Upgrade of the Dark Energy Camera and Survey for the Blanco Telescope
None
Date:
September 1, 2012
Creator:
Abdalla, F.; Annis, J.; Bacon, D.; Bridle, S.; Castander, F.; Colless, M. et al.
Object Type:
Report
System:
The UNT Digital Library
Boosted Objects: A Probe of Beyond the Standard Model Physics
We present the report of the hadronic working group of the BOOST2010 workshop held at the University of Oxford in June 2010. The first part contains a review of the potential of hadronic decays of highly boosted particles as an aid for discovery at the LHC and a discussion of the status of tools developed to meet the challenge of reconstructing and isolating these topologies. In the second part, we present new results comparing the performance of jet grooming techniques and top tagging algorithms on a common set of benchmark channels. We also study the sensitivity of jet substructure observables to the uncertainties in Monte Carlo predictions.
Date:
June 12, 2012
Creator:
Abdesselam, A.; U., /Oxford; Kuutmann, E.Bergeaas; /DESY; Bitenc, U.; U., /Freiburg et al.
Object Type:
Article
System:
The UNT Digital Library
Fermi Large Area Telescope Observations of the Cosmic-Ray Induced
We report on measurements of the cosmic-ray induced {gamma}-ray emission of Earth's atmosphere by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. The LAT has observed the Earth during its commissioning phase and with a dedicated Earth-limb following observation in September 2008. These measurements yielded {approx} 6.4 x 10{sup 6} photons with energies > 100 MeV and {approx} 250 hours total livetime for the highest quality data selection. This allows the study of the spatial and spectral distributions of these photons with unprecedented detail. The spectrum of the emission - often referred to as Earth albedo gamma-ray emission - has a power-law shape up to 500 GeV with spectral index {Lambda} = 2.79 {+-} 0.06.
Date:
February 29, 2012
Creator:
Abdo, A. A.
Object Type:
Report
System:
The UNT Digital Library
Observation of Supernova Remnant IC 443 with the Fermi Large Area Telescope
None
Date:
December 14, 2012
Creator:
Abdo, A. A.
Object Type:
Report
System:
The UNT Digital Library
Fermi Large Area Telescope Gamma-Ray Detection of the Radio Galaxy M87
None
Date:
March 29, 2012
Creator:
Abdo, A. A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. et al.
Object Type:
Article
System:
The UNT Digital Library
Fermi LAT Observation of Diffuse Gamma-Rays Produced through Interactions Between Local Interstellar Matter and High Energy Cosmic Rays
Observations by the Large Area Telescope (LAT) on the Fermi mission of diffuse {gamma}-rays in a mid-latitude region in the third quadrant (Galactic longitude l from 200{sup o} to 260{sup o} and latitude |b| from 22{sup o} to 60{sup o}) are reported. The region contains no known large molecular cloud and most of the atomic hydrogen is within 1 kpc of the solar system. The contributions of {gamma}-ray point sources and inverse Compton scattering are estimated and subtracted. The residual {gamma}-ray intensity exhibits a linear correlation with the atomic gas column density in energy from 100 MeV to 10 GeV. The measured integrated {gamma}-ray emissivity is (1.63 {+-} 0.05) x 10{sup -26} photons s{sup -1}sr{sup -1} H-atom{sup -1} and (0.66 {+-} 0.02) x 10{sup -26} photons s{sup -1}sr{sup -1} H-atom{sup -1} above 100 MeV and above 300 MeV, respectively, with an additional systematic error of {approx}10%. The differential emissivity from 100 MeV to 10 GeV agrees with calculations based on cosmic ray spectra consistent with those directly measured, at the 10% level. The results obtained indicate that cosmic ray nuclei spectra within 1 kpc from the solar system in regions studied are close to the local interstellar spectra inferred from …
Date:
March 30, 2012
Creator:
Abdo, A. A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. et al.
Object Type:
Article
System:
The UNT Digital Library
Fermi Observations of TeV-Selected AGN
None
Date:
March 29, 2012
Creator:
Abdo, A. A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. et al.
Object Type:
Article
System:
The UNT Digital Library
Insights Into the High-Energy Gamma-Ray Emission of Markarian 501 From Extensive Multifrequency Observations in the Fermi Era
None
Date:
June 14, 2012
Creator:
Abdo, A. A.; Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J. et al.
Object Type:
Article
System:
The UNT Digital Library
Fermi Large Area Telescope Measurements of the Diffuse Gamma-Ray Emission at Intermediate Galactic Latitudes
The diffuse galactic {gamma}-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess {gamma}-ray emission {ge}1 GeV relative to diffuse galactic {gamma}-ray emission models consistent with directly measured CR spectra (the so-called 'EGRET GeV excess'). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse {gamma}-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10{sup o} {le} |b| {le} 20{sup o}. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic {gamma}-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.
Date:
April 11, 2012
Creator:
Abdo, A. A.; Ackermann, M.; Ajello, M.; Anderson, B.; Atwood, W. B.; Axelsson, M. et al.
Object Type:
Article
System:
The UNT Digital Library
Fermi Observations of GRB 090902B: A Distinct Spectral Component in the Prompt and Delayed Emission
None
Date:
March 30, 2012
Creator:
Abdo, A. A.; Ackermann, M.; Ajello, M.; Asano, K.; Atwood, W. B.; Axelsson, M. et al.
Object Type:
Article
System:
The UNT Digital Library
Fermi Large Area Telescope Observations of the Crab Pulsar and Nebula
None
Date:
March 29, 2012
Creator:
Abdo, A. A.; Ackermann, M.; Ajello, M.; Atwood, W. B.; Axelsson, M.; Baldini, L. et al.
Object Type:
Article
System:
The UNT Digital Library