59,845 research outputs found
Measurement of the differential γ +2b-jet cross section and the ratio σ(γ +2b-jets)/σ(γ +b-jet) in p¯p collisions at √ s = 1.96 TeV
No full textWe present the first measurements of the differential cross section dσ/dpγ T for the production of an isolated photon in association with at least two b-quark jets. The measurements consider photons with rapiditie
Measurement of the W +b-jet and W +c-jet differential production cross sections in p¯p collisions at √s = 1.96 TeV
No full textWe present a measurement of the cross sections for the associated production of a W boson with at least one heavy quark jet, b or c , in proton–antiproton collisions. Data corresponding to an integrated luminosity of 8.7 fb−18.7 fb−1 recorded with the D0 detector at the Fermilab Tevatron View the MathML sourcepp¯ Collider at View the MathML sources=1.96 TeV are used to measure the cross sections differentially as a function of the jet transverse momenta in the range 20 to 150 GeV. These results are compared to calculations of perturbative QCD theory as well as predictions from Monte Carlo generators
Erratum: Tests of General Relativity with GW150914 [Phys. Rev. Lett. 116, 221101 (2016)]
No full textThis Erratum reports an error found in the implementation of the code of the LIGO Scientific and Virgo Collaborations (LVC) as used in gravitational-wave-based estimations of possible deviations from the post-Newtonian (PN) terms expected in general relativity (GR). The error concerned the 0.5 PN term and affected the results previously published for GW150914 [1] in Ref. [2], for GW151226 [3] in Ref. [4], and for GW170104 in Ref. [5]. We corrected the bug and present the reproduced results in this Erratum, as well as in the related Errata [6,7]. The main conclusion, that the results are consistent with general relativity, remains. In Ref. [2], the test for the parameterized post-Newtonian [8] deviations from the expected GR values relied on creating non-GR waveforms [9-13] and using them as potential matches for the observed waveforms [14-17]. In these waveforms, implemented in the frequency domain, freedom was introduced by allowing the phase coefficients describing different powers of the post-Newtonian parameter (equivalently, powers of the frequency) to assume a range of values, not only the particular values prescribed by GR. However, a coding bug was introduced, identically zeroing the deviations at 0.5 PN in the inspiral regime (as in GR). The 0.5 PN deviations were hence absent in the phasing formula, though not in the junction conditions that relate the inspiral regime to the intermediate regime. Any constraints obtained in [2,4,5] only resulted from the latter. This error affected the results of the non-GR parameter estimation (PE) [14] pipeline tests performed for finding bounds on possible PN deviations from GR. In particular, they affect the bounds on the single deviations in the 0.5 PN term and on the tests with multiple deviations together. These erroneous results appeared in Figs. 6 and 7 and Table I of [2], in Figs. 7 and 8 of [4], and in Fig. 9 of the Supplemental Material of [5]. The corrected versions of all of these have been produced. The corrections for Figs. 6 and 7 and Table I of [2] appear below, while the others are available in [6,7]. All these results are consistent with GR. (Figure Presented). The error, introduced by erroneous caching during the optimization of the waveform generation for efficient PE, has been corrected in commit [18] of the lalsuite [19] code. No subsequent LVC papers have been affected. Note that, while this error also affected the analysis of GW170608 [20], the reported results require no changes: with the corrected analysis, the GR-predicted PN coefficient values continue to be consistent with the data. No change is required regarding the preliminary reported results for GW170814 [21] either
Measurement of the differential cross-section of B+ meson production in pp collisions at root s=7 TeV at ATLAS
No full textThe production cross-section of B+ mesons is measured as a function of transverse momentum p T and rapidity y in proton-proton collisions at centre-of-mass energy root s = 7 TeV, using 2.4 fb(-1) of data recorded with the ATLAS detector at the Large Hadron Collider. The differential production cross-sections, determined in the range 9 GeV < p(T) < 120 GeV and vertical bar y vertical bar < 2.25, are compared to next-to-leading-order theoretical predictions
Study of the decay mechanism for B+ -> p(p)over-barK(+) and B+ -> p(p)over-bar pi(+)
No full textWe study the characteristics of the low mass p (p) over bar enhancements near threshold in the three-body decays B+ -> p (p) over barK(+) and B+ -> p (p) over bar pi(+). We observe that the proton polar angle distributions in the p (p) over bar helicity frame in the two decays have the opposite polarity, and measure the forward-backward asymmetries as a function of the p mass for the p (p) over barK(+) mode. We also search for the intermediate two-body decays, B+ -> (p) over bar Delta(++) and B+ -> p (Delta) over bar (0), and set upper limits on their branching fractions. These results are obtained from a 414 fb(-1) data sample that contains 449 x 10(6) B (B) over bar events collected near the Gamma(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. (c) 2007 Elsevier B.V. All rights reserved.IPE
Search for electroweak production of single top quarks in p¯p collisions
No full textWe present a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use ≈90pb−1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DØ detector between 1992 and 1995. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process p¯p→tb+X of 39 pb. The upper limit for the t-channel process p¯p→tqb+X is 58 pb
Measurement of W and Z boson production cross sections in p¯p collisions at √s=1.8 TeV
No full textDØ has measured the inclusive production cross section of W and Z bosons in a sample of 13 pb−1 of data collected at the Fermilab Tevatron. The cross sections, multiplied by their leptonic branching fractions, for production in p¯p collisions at √s=1.8 TeV are σWB(−→Weν)=2.36±0.02±0.08±0.13nb, σWB(−→Wμν)=2.09±0.06±0.22±0.11nb, σZB(→Ze+e−)=0.218±0.008±0.008±0.012nb, and σZB(→Zμ+μ−)=0.178±0.022±0.021±0.009nb, where the first uncertainty is statistical and the second systematic; the third reflects the uncertainty in the integrated luminosity. For the combined electron and muon analyses, we find σWB(−→Wlν)/σZB(→Zl+l−)=10.90±0.52. Assuming standard model couplings, we use this result to determine the width of the W boson, and obtain Γ(W)=2.044±0.097GeV
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at √<span style="text-decoration:overline">s</span>=7 TeV with the ATLAS detector
No full textThe inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton–proton collisions at a centre-of-mass energy of √s=7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb−1. The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20<p T<400 GeV and rapidity in the range |y|<2.1. The bb− -dijet cross-section is measured as a function of the dijet invariant mass in the range 110<m jj<760 GeV, the azimuthal angle difference between the two jets and the angular variable χ in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured bb− -dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta
Measurement of the ratio of three-jet to two-jet cross sections in p¯p collisions at √ s = 1.96 TeV
No full textWe present a measurement of the ratio of multijet cross sections in p¯p collisions at √ s = 1.96 TeV at the Fermilab Tevatron Collider. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb−1 collected with the D0 detector. The ratio of the inclusive three-jet to two-jet cross sections, R3/2, has been measured as a function of the jet transverse momenta. The data are compared to QCD predictions in different approximations. Popular tunes of the pythia event generator do not agree with the data, while sherpa provides a reasonable description of the data. A perturbative QCD prediction in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects, gives a good description of the data
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