| 1031. |
- Aaij, R., et al.
(author)
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Improved Measurement of CP Violation Parameters in B0s→J/ψK+K− Decays in the Vicinity of the ϕ(1020) Resonance
- 2024
-
In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 132:5
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Journal article (peer-reviewed)abstract
- The decay-time-dependent CP asymmetry in B0s→J/ψ(→μ+μ−)K+K− decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 6 fb−1, collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 B0s signal decays with an invariant K+K− mass in the vicinity of the ϕ(1020) resonance, the CP-violating phase ϕs is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B0s−¯B0s system, ΔΓs, and the difference of the average B0s and B0 meson decay widths, Γs−Γd. The values obtained are ϕs=−0.039±0.022±0.006 rad, ΔΓs=0.0845±0.0044±0.0024 ps−1, and Γs−Γd=−0.0056+0.0013−0.0015±0.0014 ps−1, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase ϕs is also measured independently for each polarization state of the K+K− system and shows no evidence for polarization dependence.
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| 1032. |
- Aaij, R., et al.
(author)
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J/psi photoproduction in Pb-Pb peripheral collisions at root S-NN=5 TeV
- 2022
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In: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 105:3
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Journal article (peer-reviewed)abstract
- The photoproduction of J/psi mesons at low transverse momentum is studied in peripheral lead-lead collisions collected by the LHCb Collaboration at a center-of-mass energy per nucleon pair of 5 TeV, corresponding to an integrated luminosity of 210 mu b(-1). The J/psi candidates are reconstructed through the prompt decay into two muons of opposite charge in the rapidity region of 2.0 < y < 4.5. The results significantly improve previous measurements and are compared to the latest theoretical prediction.
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| 1033. |
- Aaij, R., et al.
(author)
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Measurement of antiproton production from antihyperon decays in pHe collisions at √ˆšsNN=110 GeV
- 2023
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In: European Physical Journal C. - : SPRINGER. - 1434-6044 .- 1434-6052. ; 83
-
Journal article (peer-reviewed)abstract
- The interpretation of cosmic antiproton flux measurements from space-borne experiments is currently limited by the knowledge of the antiproton production cross-section in collisions between primary cosmic rays and the interstellar medium. Using collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest in the proximity of the interaction region of the LHCb experiment, the ratio of antiprotons originating from antihyperon decays to prompt production is measured for antiproton momenta between 12 and 110 GeV/c. The dominant antihyperon contribution, namely (Lambda) over bar -> (p) over bar pi(+) decays from promptly produced (Lambda) over bar particles, is also exclusively measured. The results complement the measurement of prompt antiproton production obtained from the same data sample. At the energy scale of this measurement, the antihyperon contributions to antiproton production are observed to be significantly larger than predictions of commonly used hadronic production models.
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| 1034. |
- Aaij, R., et al.
(author)
-
Measurement of CP asymmetries and branching fraction ratios of B- decays to two charm mesons
- 2023
-
In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :9
-
Journal article (peer-reviewed)abstract
- The CP asymmetries of seven B- decays to two charm mesons are measured using data corresponding to an integrated luminosity of 9 fb(-1) of proton-proton collisions collected by the LHCb experiment. Decays involving a D*(0) or D-s(*-) meson are analysed by reconstructing only the D-0 or D-s(-) decay products. This paper presents the first measurement of A(CP) (B- -> D-s(*-) D-0) and A(CP) (B- -> D-s(-) D*(0)), and the most precise measurement of the other five CP asymmetries. There is no evidence of CP violation in any of the analysed decays. Additionally, two ratios between branching fractions of selected decays are measured.
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| 1035. |
- Aaij, R., et al.
(author)
-
Measurement of CP asymmetries in D-(s)(+) -> eta pi(+) and D-(s)(+) -> eta 'pi(+) decays
- 2023
-
In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479.
-
Journal article (peer-reviewed)abstract
- Searches for CP violation in the decays D-(s)(+) -> eta pi(+) and D-(s)(+) -> eta'pi(+) are performed using pp collision data corresponding to 6 fb(-1) of integrated luminosity collected by the LHCb experiment. The calibration channels D-(s)(+) -> phi pi(+) are used to remove production and detection asymmetries. The resulting CP-violating asymmetries are A(CP) (D+ -> eta pi(+)) = (0.34 +/- 0.66 +/- 0.16 +/- 0.05)%, A(CP) (D-s(+) -> eta pi(+)) = (0.32 +/- 0.51 +/- 0.12)%, A(CP) (D+ -> eta'pi(+)) = (0.49 +/- 0.18 +/- 0.06 +/- 0.05)%, A(CP) (D-s(+) -> eta'pi(+)) = (0.01 +/- 0.12 +/- 0.08)%, where the first uncertainty is statistical, the second is systematic and the third, relevant for the D+ channels, is due to the uncertainty on A(CP) (D+ -> phi pi(+)). These measurements, currently the most precise for three of the four channels considered, are consistent with the absence of CP violation. A combination of these results with previous LHCb measurements is presented.
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| 1036. |
- Aaij, R., et al.
(author)
-
Measurement of CP asymmetry in D-0 -> (KSKS0)-K-0 decays
- 2021
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In: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 104:3
-
Journal article (other academic/artistic)abstract
- A measurement of the CP asymmetry in D-0 -> (KSKS0)-K-0 decays is reported, based on a data sample of proton-proton collisions collected by the LHCb experiment from 2015 to 2018, corresponding to an integrated luminosity of 6 fb(-1). The flavor of the D-0 candidate is determined using the charge of the D-*+/- meson, from which the decay is required to originate. The D-0 -> K+K- decay is used as a calibration channel. The time-integrated CP asymmetry for the D-0 -> (KSKS0)-K-0 mode is measured to be A(CP)(D-0 -> (KSKS0)-K-0) = (-3.1 +/- 1.2 +/- 0.4 +/- 0.2), where the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the CP asymmetry of the calibration channel. This is the most precise determination of this quantity to date.
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| 1037. |
- Aaij, R., et al.
(author)
-
Measurement of J/psi production cross-sections in pp collisions at root s=5 TeV
- 2021
-
In: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; :11
-
Journal article (peer-reviewed)abstract
- The production cross-sections of J/psi mesons in proton-proton collisions at a centre-of-mass energy of root s = 5TeV are measured using a data sample corresponding to an integrated luminosity of 9.13 +/- 0.18 pb(-1), collected by the LHCb experiment. The cross-sections are measured differentially as a function of transverse momentum, p(T), and rapidity, y, and separately for J/psi mesons produced promptly and from beauty hadron decays (nonprompt). With the assumption of unpolarised J/psi mesons, the production cross-sections integrated over the kinematic range 0 < p(T) < 20 GeV/c and 2.0 < y < 4.5 are sigma(prompt) J/psi = 8.154 +/- 0.010 +/- 0.283 mu b, sigma(nonprompt) J/psi = 0.820 +/- 0.003 +/- 0.034 mu b, where the first uncertainties are statistical and the second systematic. These cross-sections are compared with those at root s = 8TeV and 13TeV, and are used to update the measurement of the nuclear modification factor in proton-lead collisions for J/psi mesons at a centre-of-mass energy per nucleon pair of root s(NN) = 5TeV. The results are compared with theoretical predictions.
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| 1038. |
- Aaij, R., et al.
(author)
-
Measurement of J/ψ-pair production in pp collisions at √‾s = 13 TeV and study of gluon transverse-momentum dependent PDFs
- 2024
-
In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :3
-
Journal article (peer-reviewed)abstract
- The production cross-section of J/ψ pairs in proton-proton collisions at a centre-of-mass energy of s√ = 13 TeV is measured using a data sample corresponding to an integrated luminosity of 4.2 fb−1 collected by the LHCb experiment. The measurement is performed with both J/ψ mesons in the transverse momentum range 0 < pT < 14 GeV/c and rapidity range 2.0 < y < 4.5. The cross-section of this process is measured to be 16.36 ± 0.28 (stat) ± 0.88 (syst) nb. The contributions from single-parton scattering and double-parton scattering are separated based on the dependence of the cross-section on the absolute rapidity difference ∆y between the two J/ψ mesons. The effective cross-section of double-parton scattering is measured to be σeff = 13.1 ± 1.8 (stat) ± 2.3 (syst) mb. The distribution of the azimuthal angle ϕCS of one of the J/ψ mesons in the Collins-Soper frame and the pT-spectrum of the J/ψ pairs are also measured for the study of the gluon transverse-momentum dependent distributions inside protons. The extracted values of ⟨cos 2ϕCS⟩ and ⟨cos 4ϕCS⟩ are consistent with zero, but the presence of azimuthal asymmetry at a few percent level is allowed.
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| 1039. |
- Aaij, R., et al.
(author)
-
Measurement of lepton universality parameters in B plus ? : K plus l + l - and B0? K?0l+l- decays
- 2023
-
In: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 108:3
-
Journal article (peer-reviewed)abstract
- A simultaneous analysis of the B thorn & RARR; K thorn e thorn e- and B0 & RARR; K & DBLBOND;0e thorn e- decays is performed to test muonelectron universality in two ranges of the square of the dilepton invariant mass, q2. The measurement uses a sample of beauty meson decays produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb-1. A sequence of multivariate selections and strict particle identification requirements produce a higher signal purity and a better statistical sensitivity per unit luminosity than previous LHCb lepton universality tests using the same decay modes. Residual backgrounds due to misidentified hadronic decays are studied using data and included in the fit model. Each of the four lepton universality measurements reported is either the first in the given q2 interval or supersedes previous LHCb measurements. The results are compatible with the predictions of the Standard Model.
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| 1040. |
- Aaij, R., et al.
(author)
-
Measurement of prompt D+ and Ds+ production in pPb collisions at √ˆšsNN=5.02 TeV
- 2024
-
In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479.
-
Journal article (peer-reviewed)abstract
- The production of prompt D+ and D+s mesons is studied in proton-lead collisions at a centre-of-mass energy of √sNN = 5.02TeV. The data sample corresponding to an integrated luminosity of (1.58 ± 0.02)nb-1 is collected by the LHCb experiment at the LHC. The differential production cross-sections are measured using D+ and D+s candidates with transverse momentum in the range of 0 < pT < 14 GeV/c and rapidities in the ranges of 1.5 < y* < 4.0 and -5.0 < y* < -2.5 in the nucleon-nucleon centre-of-mass system. For both particles, the nuclear modification factor and the forward-backward production ratio are determined. These results are compared with theoretical models that include initial-state nuclear effects. In addition, measurements of the cross-section ratios between D+, D+s and D0 mesons are presented, providing a baseline for studying the charm hadronization in lead-lead collisions at LHC energies.
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