2,384 research outputs found
Study of X(3915) → J/ψω in Two-Photon Collisions
No full textWe study the process γγ → J/ψω using a data sample of 519.2 fb⁻¹ recorded by the BABAR detector at SLAC at the PEP-II asymmetric-energy e⁺e⁻ collider at center-of-mass energies near the Υ(nS) (n = 2, 3, 4) resonances. We confirm the existence of the charmoniumlike resonance X(3915) decaying to J/ψω with a significance of 7.6 standard deviations, including systematic uncertainties, and measure its mass (3919.4 ± 2.2 ± 1.6) MeV/c² and width (13 ± 6 ± 3) MeV, where the first uncertainty is statistical and the second systematic. A spin-parity analysis supports the assignment J^P = 0⁺ and therefore the identification of the signal as due to the χ_{c0}(2P) resonance. In this hypothesis we determine the product between the two-photon width and the final state branching fraction to be (52 ± 10 ± 3) eV
Study of B^{±,0} → J/ψK⁺K⁻K^{±,0} and search for B⁰ → J/ψϕ at BaBar
No full textWe study the rare B meson decays B^{±,0} → J/ψK⁺K⁻K^{±,0}, B^{±,0} → J/ψϕK^{±,0} and search for B⁰ → J/ψϕ, using 469 x 10⁶ BB̅ events collected at the ϒ(4S) resonance with the BABAR detector at the PEP-II e⁺e⁻ asymmetric energy collider. We present new measurements of branching fractions and a study of the J/ψϕ mass distribution in search of new charmonium-like states. In addition, we search for the decay B⁰ → J/ψϕ and find no evidence of a signal
Measurement of Differential J/ψ Production Cross Sections and Forward-Backward Ratios in P + Pb Collisions with the ATLAS Detector
No full textMeasurements of differential cross sections for J/ψ production in p+Pb collisions at √{sNN}=5.02 TeV at the CERN Large Hadron Collider with the ATLAS detector are presented. The data set used corresponds to an integrated luminosity of 28.1 nb⁻¹. The J/ψ mesons are reconstructed in the dimuon decay channel over the transverse momentum range 8 < pT < 30 GeV and over the center-of-mass rapidity range -2.87 < y∗ < 1.94. Prompt J/ψ are separated from J/ψ resulting from b-hadron decays through an analysis of the distance between the J/ψ decay vertex and the event primary vertex. The differential cross section for production of nonprompt J/ψ is compared to a FONLL calculation that does not include nuclear effects. Forward-backward production ratios are presented and compared to theoretical predictions. These results complement previously published results by covering a region of higher transverse momentum and more central rapidity. They thus constrain the kinematic dependence of nuclear modifications of charmonium and b-quark production in p+Pb collisions
Study of the Reaction e⁺e⁻ -→ J/ψ π⁺π⁻ via Initial-State Radiation at BABAR
No full textWe study the process e⁺e⁻ → J/ψ π⁺π⁻ with initial-state-radiation events produced at the PEP-II asymmetric-energy collider. The data were recorded with the BABAR detector at center-of-mass energies 10.58 and 10.54 GeV, and correspond to an integrated luminosity of 454 fb⁻¹. We investigate the J/ψ π⁺π⁻ mass distribution in the region from 3.5 to 5.5 GeV/c². Below 3.7 GeV/c² the ψ(2S) signal dominates, and above 4 GeV/c² there is a significant peak due to the Y(4260). A fit to the data in the range 3.74-5.50 GeV/c² yields a mass value 4245 ±5(stat) ±4(syst) MeV/c² and a width value 114{_-15 ^{+16}} (stat) ±7(syst) MeV for this state. We do not confirm the report from the Belle Collaboration of a broad structure at 4.01 GeV/c². In addition, we investigate the π⁺π⁻ system which results from Y(4260) decay
Measurement of the Branching Ratio Γ ({Λ_b⁰} → ψ(2s)Λ⁰) / Γ ({Λ_b⁰} → J/ψΛ⁰) with the ATLAS Detector
No full textAn observation of the Γ_b^{Λ0} > ψ(2s)Λ⁰ decay and a comparison of its branching fraction with that of the Λ_b^0 > ψ(2s)Λ⁰ decay has been made with the ATLAS detector in proton-proton collisions at √s̅ = 8 TeV at the LHC using an integrated luminosity of 20.6 fb⁻¹. The J/ψ and ψ(2s) mesons are reconstructed in their decays to a muon pair, while the Λ⁰ > pπ⁻ decay is exploited for the Λ⁰ baryon reconstruction. The Λ_b^0 baryons are reconstructed with transverse momentum p_T > 10 GeV and pseudorapidity |η| < 2.1. The measured branching ratio of the Λ_b^0 → ψ(2s)Λ⁰ and Λ_b^0 and Λ_b^0 → J/ψΛ⁰ decay is Γ(Λ_b^0 / Γ(Λ_b^0 → J/ψΛ⁰) = 0.501 ± 0.033(stat) ± 0.019(syst), lower than the expectation from the covariant quark model
Measurements of ψ(2S) and X(3872) → J/ψπ⁺π⁻ Production in PP Collisions at √s = 8 TeV with the ATLAS Detector
No full textDifferential cross sections are presented for the prompt and non-prompt production of the hidden-charm states X(3872) and ψ(2S), in the decay mode J/ψπ⁺π⁻, measured using 11.4 fb⁻¹ of pp collisions at √s̅ = 8 TeV by the ATLAS detector at the LHC. The ratio of cross-sections X(3872)/ψ(2S) is also given, separately for prompt and non-prompt components, as well as the non-prompt fractions of X(3872) and ψ(2S). Assuming independent single effective lifetimes for non-prompt X(3872) and ψ(2S) production gives R_B=ℬ(Β → X(3872) + any) ℬ(X(3872) → J/ψπ⁺π⁻) / ℬ(B → ψ(2S) + any) ℬ(ψ(2S) → J/ψπ⁺π⁻) =(3.95 ± 0.32(stat) ± 0.08(sys)) × 10⁻² while separating short- and long-lived contributions, assuming that the short-lived component is due to B_c decays, gives R_B = (3.57 ± 0.33(stat) ± 0.11(sys)) × 10⁻², with the fraction of non-prompt X(3872) produced via B_c decays for p_T(X(3872)) > 10 GeV being (25 ± 13(stat) ± 2(sys) ± 5(spin))%. The distributions of the dipion invariant mass in the X(3872) and ψ(2S) decays are also measured and compared to theoretical predictions.School of Natural Sciences and Mathematic
Determination of the Ratio of B -Quark Fragmentation Fractions F{s} / f{d} in pp Collisions at √s̅ =7 TeV with the ATLAS Detector
No full textWith an integrated luminosity of 2.47 fb⁻¹ recorded by the ATLAS experiment at the LHC, the exclusive decays B_s^0 → J/ψϕ and B_d^0 → J/ψK^{*0} of B mesons produced in pp collisions at √s̅ = 7 TeV are used to determine the ratio of fragmentation fractions f_s / f_d. From the observed B_s^0 → J/ψϕ and B_d^0 → J/ψK^{*0} yields, the quantity (f_s ± 0.017(th). This result is based on a new approach that provides a significant improvement of the world average / f_d) [ℬ(B_s^0 → J/ψϕ) /ℬ(B_d^0 → J/ψK^{*0})] is measured to be 0.199 ± 0.004 (stat) ± 0.008(syst). Using a recent theory prediction for [ℬ(B_s^0 → J/ψϕ) / ℬ(B_d^0 → J/ψK^{*0})] yields (f_s / f_d)=0.240 ± 0.004(stat) ± 0.010(syst)
Observation and Measurements of the Production of Prompt and Non-Prompt J/ψ Mesons in Association with a Z Boson in pp Collisions at √s̅ = 8 TeV with the ATLAS Detector
No full textThe production of a Z boson in association with a J/ψ meson in proton-proton collisions probes the production mechanisms of quarkonium and heavy flavour in association with vector bosons, and allows studies of multiple parton scattering. Using 20.3 fb⁻¹ of data collected with the ATLAS experiment at the LHC in pp collisions at √s̅ = 8 TeV, the first measurement of associated Z + J/ψ production is presented for both prompt and non-prompt J/ψ production, with both signatures having a significance in excess of 5σ. The inclusive production cross-sections for Z boson production (analysed in μ⁺μ⁺ or e⁺e⁻ decay modes) in association with prompt and non-prompt J/ψ (→ μ⁺μ⁺) are measured relative to the inclusive production rate of Z bosons in the same fiducial volume to be (36.8 ± 6.7 ± 2.5) x 10⁻⁷ and (65.8 ± 9.2 ± 4.2) x 10⁻⁷ respectively. Normalised differential production cross-section ratios are also determined as a function of the J/ψ transverse momentum. The fraction of signal events arising from single and double parton scattering is estimated, and a lower limit of 5.3 (3.7) mb at 68 (95)% confidence level is placed on the effective cross-section regulating double parton interactions
Search for B→K^{(*)}νν̅ and Invisible Quarkonium Decays
No full textWe search for the flavor-changing neutral-current decays B→K^{(*)}νν¯, and the invisible decays J/ψ→νν̅ and ψ(2S)→νν̅ via B→K^{(*)}J/ψ and B→K^{(*)}ψ(2S), respectively, using a data sample of 471×10⁶ BB̅ pairs collected by the BABAR experiment. We fully reconstruct the hadronic decay of one of the B mesons in the Ψ(4S)→ BB̅ decay, and search for the B→K^{(*)}νν̅ decay in the rest of the event. We observe no significant excess of signal decays over background and report branching fraction upper limits of B(B⁺→K⁺νν̅) < 3.7×10⁻⁵, B(B⁰→K⁰ νν̅) <8.1×10⁻⁵, B(B⁺→K*⁺ νν̅) < 11.6×10⁻⁵, B(B⁰→K*⁰ νν̅) < 9.3×10⁻⁵, and combined upper limits of B(B→Kνν̅) <3.2×10⁻⁵ and B(B→K*νν̅) < 7.9×10⁻⁵, all at the 90% confidence level. For the invisible quarkonium decays, we report branching fraction upper limits of B(J/ψ→νν̅) < 3.9×10⁻³ and B(ψ(2S)→νν̅) < 15.5×10⁻³ at the 90% confidence level. Using the improved kinematic resolution achieved from hadronic reconstruction, we also provide partial branching fraction limits for the B→K^{(*)}νν̅ decays over the full kinematic spectrum
Measurement of Quarkonium Production in Proton-Lead and Proton- Proton Collisions at 5.02 TeV with the ATLAS Detector
No full textThe modification of the production of J/ψ, ψ(2S), and Υ(nS) (n = 1, 2, 3) in p+Pb collisions with respect to their production in pp collisions has been studied. The p+Pb and pp datasets used in this paper correspond to integrated luminosities of 28 nb⁻¹ and 25 pb⁻¹ respectively, collected in 2013 and 2015 by the ATLAS detector at the LHC, both at a centre-of-mass energy per nucleon pair of 5.02 TeV. The quarkonium states are reconstructed in the dimuon decay channel. The yields of J/ψ and ψ(2S) are separated into prompt and non- prompt sources. The measured quarkonium differential cross sections are presented as a function of rapidity and transverse momentum, as is the nuclear modification factor, R_{pPb} for J/ψ and Υ(nS). No significant modification of the J/ψ production is observed while Υ(nS) production is found to be suppressed at low transverse momentum in p+Pb collisions relative to pp collisions. The production of excited charmonium and bottomonium states is found to be suppressed relative to that of the ground states in central p+Pb collisions.School of Natural Sciences and Mathematic
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