1,515 research outputs found

    Dosimetric review of cardiac implantable electronic device patients receiving radiotherapy

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135218/1/acm20254-sup-0002.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135218/2/acm20254.pd

    Measurement of forward J/ψ production cross-sections in pp collisions at √s=13 TeV

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    The production of J/ψ mesons in proton-proton collisions at a centre-of-mass energy of √s=13 TeV is studied with the LHCb detector. Cross-section measurements are performed as a function of the transverse momentum p T and the rapidity y of the J/ψ meson in the region p T < 14 GeV/c and 2.0 < y < 4.5, for both prompt J/ψ mesons and J/ψ mesons from b-hadron decays. The production cross-sections integrated over the kinematic coverage are 15.30 ± 0.03 ± 0.86 ÎŒb for prompt J/ψ and 2.34 ± 0.01 ± 0.13 ÎŒb for J/ψ from b-hadron decays, assuming zero polarization of the J/ψ meson. The first uncertainties are statistical and the second systematic. The cross-section reported for J/ψ mesons from b-hadron decays is used to extrapolate to a total bb cross-section. The ratios of the cross-sections with respect to √s=8 TeV are also determinedS

    Measurement of ϒ production in pp collisions at √s=13 TeV

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    The production cross-sections of ϒ(1S), ϒ(2S) and ϒ(3S) mesons in proton-proton collisions at √s=13 TeV are measured with a data sample corresponding to an integrated luminosity of 277 ± 11 pb−1 recorded by the LHCb experiment in 2015. The ϒ mesons are reconstructed in the decay mode ϒ → ÎŒ+Ό−. The differential production cross-sections times the dimuon branching fractions are measured as a function of the ϒ transverse momentum, pT, and rapidity, y, over the range 0 < pT < 30 GeV/c and 2.0 < y < 4.5. The ratios of the cross-sections with respect to the LHCb measurement at s√=8 TeV are also determined. The measurements are compared with theoretical predictions based on NRQCD.S

    Measurement of the CKM angle Îł using B± → DK± with D → K0Sπ+π−, K0SK+K− decays

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    A binned Dalitz plot analysis of B± → DK± decays, with D → K 0Sπ+π− and D → K 0SK+K−, is used to perform a measurement of the CP-violating observables x± and y±, which are sensitive to the Cabibbo-Kobayashi-Maskawa angle Îł. The analysis is performed without assuming any D decay model, through the use of information on the strong-phase variation over the Dalitz plot from the CLEO collaboration. Using a sample of proton-proton collision data collected with the LHCb experiment in 2015 and 2016, and corresponding to an integrated luminosity of 2.0 fb−1, the values of the CP violation parameters are found to be x− = (9.0 ± 1.7 ± 0.7 ± 0.4) × 10−2, y− = (2.1 ± 2.2 ± 0.5 ± 1.1) × 10−2, x+ = (−7.7 ± 1.9 ± 0.7 ± 0.4) × 10−2, and y+ = (−1.0 ± 1.9 ± 0.4 ± 0.9) × 10−2. The first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty (on the strong-phase measurements. These values are used to obtain γ = (87 + 11− 12)∘, rB = 0.086 + 0.013− 0.014, and ÎŽB = (101±11)°, where rB is the ratio between the suppressed and favoured B-decay amplitudes and ÎŽB is the corresponding strong-interaction phase difference. This measurement is combined with the result obtained using 2011 and 2012 data collected with the LHCb experiment, to give γ = (80 + 10− 9)∘, rB = 0.080 ± 0.011, and ÎŽB = (110 ± 10)°.S

    Measurement of D ±s production asymmetry in pp collisions at √s=7 and 8 TeV

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    The inclusive D ±s production asymmetry is measured in pp collisions collected by the LHCb experiment at centre-of-mass energies of √s=7 and 8 TeV. Promptly produced D ±s mesons are used, which decay as D ±s → ϕπ±, with ϕ → K+K−. The measurement is performed in bins of transverse momentum, pT, and rapidity, y, covering the range 2.5 < pT < 25.0 GeV/c and 2.0 < y < 4.5. No kinematic dependence is observed. Evidence of nonzero D ±s production asymmetry is found with a significance of 3.3 standard deviations.S

    Evidence for the decay B0S→K¯∗0ÎŒ+Ό−

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    A search for the decay B0S→K¯∗0ÎŒ+Ό− is presented using data sets corresponding to 1.0, 2.0 and 1.6 fb−1 of integrated luminosity collected during pp collisions with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. An excess is found over the background-only hypothesis with a significance of 3.4 standard deviations. The branching fraction of the B0S→K¯∗0ÎŒ+Ό− decay is determined to be B(B0s→K¯∗0ÎŒ+Ό−)=[2.9±1.0(stat)±0.2(syst)±0.3(norm)]×10−8, where the first and second uncertainties are statistical and systematic, respectively. The third uncertainty is due to limited knowledge of external parameters used to normalise the branching fraction measurement.S

    Central exclusive production of J/ψ and ψ(2S) mesons in pp collisions at √s=13 TeV

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    Measurements are reported of the central exclusive production of J/ψ and ψ(2S) mesons in pp collisions at a centre-of-mass energy of 13 TeV. Backgrounds are significantly reduced compared to previous measurements made at lower energies through the use of new forward shower counters. The products of the cross-sections and the branching fractions for the decays to dimuons, where both muons are within the pseudorapidity range 2.0 < η < 4.5, are measured to be σJ/ψ→Ό+Ό−=435±18±11±17 pbσψ(2S)→Ό+Ό−=11.1±1.1±0.3±0.4 pb. The first uncertainties are statistical, the second are systematic, and the third are due to the luminosity determination. The cross-sections are also measured differentially for meson rapidities between 2.0 and 4.5. Good agreement is observed with theoretical predictions. Photoproduction cross-sections are derived and compared to previous experiments, and a deviation from a pure power-law extrapolation of lower energy data is observed.S

    Observation of the decay BÂŻ0s→χc2K+K− in the ϕ mass region

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    The BÂŻ0s→χc2K+K− decay mode is observed and its branching fraction relative to the corresponding χc1 decay mode, in a ±15 MeV/c2 window around the ϕ mass, is found to be B(BÂŻ0s→χc2K+K−)B(BÂŻ0s→χc1K+K−)=(17.1±3.1±0.4±0.9)%, where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the branching fractions of radiative χc decays. The decay mode BÂŻ0s→χc1K+K− allows the B0s mass to be measured as m(B0s)=5366.83±0.25±0.27 MeV/c2, where the first uncertainty is statistical and the second systematic. A combination of this result with other LHCb determinations of the B 0s mass is made.S

    Studies of the resonance structure in D0→K∓π±π±π∓ decays

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    Amplitude models are constructed to describe the resonance structure of D0 → K− π + π + π − and D0 → K+ π − π − π + decays using pp collision data collected at centre-of-mass energies of 7 and 8 TeV with the LHCb experiment, corresponding to an integrated luminosity of 3.0 f b−1. The largest contributions to both decay amplitudes are found to come from axial resonances, with decay modes D0 → a1(1260) +K− and D0 → K1(1270/1400) + π − being prominent in D0 → K− π + π + π − and D0 → K+ π − π − π +, respectively. Precise measurements of the lineshape parameters and couplings of the a1(1260) +, K1(1270) − and K(1460) − resonances are made, and a quasi model-independent study of the K(1460) − resonance is performed. The coherence factor of the decays is calculated from the amplitude models to be RK3π = 0.459 ± 0.010 (stat) ± 0.012 (syst)±0.020 (model), which is consistent with direct measurements. These models will be useful in future measurements of the unitary-triangle angle Îł and studies of charm mixing and CP violationS

    Evidence for an ηc(1S)π− resonance in B0 → ηc(1S)K+π− decays

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    A Dalitz plot analysis of B0 → ηc(1S)K +π− decays is performed using data samples of pp collisions collected with the LHCb detector at centre-of-mass energies of √s = 7, 8 and 13 TeV, corresponding to a total integrated luminosity of 4.7 fb−1. A satisfactory description of the data is obtained when including a contribution representing an exotic ηc(1S)π− resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are 4096 ± 20 +18 −22 MeV and 152±58 +60 −35 MeV, respectively. The spin-parity assignments J P = 0+ and J P = 1− are both consistent with the data. In addition, the first measurement of the B0 → ηc(1S)K +π− branching fraction is performed and gives B(B0→ ηc(1S)K +π−) = (5.73 ± 0.24 ± 0.13 ± 0.66) × 10−4, where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractionsS
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