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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Measurement of the Time-Integrated CP Asymmetry in D0 → K- K+ Decays. Phys. Rev. Lett., 131(9), 091802–13pp.
Abstract: The time-integrated CP asymmetry in the Cabibbo suppressed decay PKK is measured using proton proton collision data, corresponding to an integrated luminosity of 5.7 th collected at a center of mass energy of 13 TeV with the LHCb detector. The D mesons are required to originate from promptly produced DD's decays, and the charge of the companion pion is used to determine the flavor of the charm meson at production. The time integrated CP asymmetry is measured to be Acr(KK) 6,815.41.6 x 10 where the first uncertainty is statistical and the second systematic. The direct CP asymmetries in D-K-K and D -> decays, and are derived by combining Ace(KK) with the time integrated CP asymmetry differ ence, AAcr-Acr(KK)-A(x), and other inputs, giving a (7.715.7) x 10, (23.2 16.1) x 10, with a correlation coefficient corresponding to p=0.88. The compatibility of these results with CP symmetry is 1.4 and 3.8 standard deviations for DKK and D degrees-xx decays, respectively. This is the first evidence for direct CP violation in a specific Do decay.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Study of charmonium decays to KS0Kπ in the B → (KS0Kπ)K channels. Phys. Rev. D, 108(3), 032010–41pp.
Abstract: A study of the B+ -> (KSK+)-K-0 K-pi(+) and B+ -> (KSK+K+)-K-0 pi(-) decays is performed using proton-proton collisions at center-of-mass energies of 7, 8 and 13 TeV at the LHCb experiment. The (KSK)-K-0 pi invariant mass spectra from both decay modes reveal a rich content of charmonium resonances. New precise measurements of the eta(c) and eta(c)(2S) resonance parameters are performed and branching fraction measurements are obtained for B+ decays to eta(c), J/psi, eta(c)(2S) and chi(c1) resonances. In particular, the first observation and branching fraction measurement of B+ -> chi K-c0(0)pi(+) is reported as well as first measurements of the B+ -> (KK+K-)-K-0 pi(+) and B+ -> (KK+K+)-K-0 pi(-) branching fractions. Dalitz plot analyses of eta(c) -> (KSK)-K-0 pi and eta(c)(2S) -> (KSK)-K-0 pi decays are performed. A new measurement of the amplitude and phase of the K pi S-wave as functions of the K pi mass is performed, together with measurements of the K-0*(1430), K-0*(1950) and a(0)(1700) parameters. Finally, the branching fractions of chi(c1) decays to K* resonances are also measured.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Multidifferential study of identified charged hadron distributions in Z-tagged jets in proton-proton collisions at vs=13 TeV. Phys. Rev. D, 108(3), L031103–13pp.
Abstract: Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a Z boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 < pT < 100 GeV and in the pseudorapidity range 2.5 < ? < 4. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb(-1). Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Study of the B- → Λc+(Λ)over-barc-K- decay. Phys. Rev. D, 108(1), 012020–15pp.
Abstract: The decay B- -> Lambda(+)(c)(Lambda) over bar K--(c)- is studied in proton-proton collisions at a center-of-mass energy of root s = 13 TeV using data corresponding to an integrated luminosity of 5 fb(-1) collected by the LHCb experiment. In the Lambda K-+(c)- system, the Xi(c)(2930)(0) state observed at the BABAR and Belle experiments is resolved into two narrower states, Xi(c)(2923)(0) and Xi(c)(2939)(0), whose masses and widths are measured to be m(Xi(c)(2930)(0) = 2924.5 +/- 0.4 +/- 1.1 Mev, m Xi(c)(2930)(0)) = 2938.5 +/- 0.9 +/- 2.3 Mev, Gamma(Xi(c)(2930)(0)) = 4.8 +/- 0.9 +/- 1.5 MeV, Gamma(Xi(c)(2930)(0) – 11.0 +/- 1.9 +/- 7.5 MeV, where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt Lambda K-+(c)- sample. Evidence of a new Xi(c)(2930)(0) state is found with a local significance of 3.8 sigma, whose mass and width are measured to be 2881.8 +/- 3.1 +/- 8.5 MeV and 12.4 +/- 5.3 +/- 5.8 MeV, respectively. In addition, evidence of a new decay mode Xi(c)(2930)(0) -> Lambda K-+(c) is found with a significance of 3.7 sigma. The relative branching fraction of B- -> Lambda(+)(c)(Lambda) over bar K--(c)- with respect to the B- -> D+D-K- decay is measured to be 2.36 +/- 0.11 +/- 0.22 +/- 0.25, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Study of Bc+ meson decays to charmonia plus multihadron final states. J. High Energy Phys., 07(7), 198–26pp.
Abstract: Four decay modes of the B-c(+) meson into a J/psi meson and multiple charged kaons or pions are studied using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13TeV and corresponding to an integrated luminosity of 9 fb(-1). The decay B-c(+) -> J/psi K+ K- pi(+)pi(+)pi(-) is observed for the first time, and evidence for the B-c(+) -> J/psi 4 pi(+)3 pi(-) decay is found. The decay B-c(+) -> J/psi 3 pi(+)2 pi(-) is observed and the previous observation of the B-c(+) -> psi(2S)pi(+)pi(+)pi(-) decay is confirmed using the psi(2S) -> J/psi pi(+)pi(-) decay mode. Ratios of the branching fractions of these four B-c(+) decay channels are measured.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Measurement of τL using the Bs0 →J/ψη decay mode. Eur. Phys. J. C, 83(7), 629–13pp.
Abstract: Using a proton-proton collision data sample collected by the LHCb detector and corresponding to an integrated luminosity of 5.7 fb(-1), the lifetime of the light B-s(0) mass eigenstate, tau(L), is measured using the B-s(0) -> J/psi eta decay mode to be tau(L) = 1.445 +/- 0.016(stat) +/- 0.008(syst) ps. A combination of this result with a previous LHCb analysis using an independent dataset corresponding to 3 fb(-1) of integrated luminosity gives tau(L) = 1.452 +/- 0.014 +/- 0.007 +/- 0.002 ps, where the first uncertainty is statistical, the second due to the uncorrelated part of the systematic uncertainty and the third due to the correlated part of the systematic uncertainty.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Charmonium production in pNe collisions at √sNN=68.5 GeV. Eur. Phys. J. C, 83(7), 625–11pp.
Abstract: The measurement of charmonium states produced in proton-neon (pNe) collisions by the LHCb experiment in its fixed-target configuration is presented. The production of J/Psi and Psi(2S) mesons is studied with a beam of 2.5 TeV protons colliding on gaseous neon targets at rest, cvorresponding to a nucleon-nucleon centre-of-mass energy root(NN)-N-s = 68.5GeV. The data sample corresponds to an integrated luminosity of 21.7 +/- 1.4 nb(-1). The J/Psi and Psi(2S) hadrons are reconstructed in mu(+) mu(-) final states. The J/Psi production cross-section per target nucleon in the centre-of-mass rapidity range y* is an element of [-2.29, 0] is found to be 506 +/- 8 +/- 46 nb/nucleon. The ratio of J/Psi and D-0 cross-sections is evaluated to (1.06 +/- 0.02 +/- 0.09)%. The Psi(2S) to J/Psi relative production rate is found to be (1.67 +/- 0.27 +/- 0.10)% in good agreement with other measurements involving beam and target nuclei of similar sizes.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Search for CP violation in D(s)+ → K- K+ K+ decays. J. High Energy Phys., 07(7), 067–25pp.
Abstract: A search for direct CP violation in the Cabibbo-suppressed decay D-s(+) -> K-K+ K+ and in the doubly Cabibbo-suppressed decay D+ -> K- K+ K+ is reported. The analysis is performed with data collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of 13TeV corresponding to an integrated luminosity of 5.6 fb(-1). The search is conducted by comparing the D-(s)(+) and D-(s)(-) Dalitz-plot distributions through a model-independent binned technique, based on fits to the K-K+K+ invariantmass distributions, with a total of 0.97 (1.27) million D-s(+) (D+) signal candidates. The results are given as p-values for the hypothesis of CP conservation and are found to be 13.3% for the D+ -> K-K+ K+ decay and 31.6% for the D+ -> K-K+ K+ decay. No evidence for CP violation is observed in these decays.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Open charm production and asymmetry in pNe collisions at √s_NN =68.5 GeV. Eur. Phys. J. C, 83(6), 541–11pp.
Abstract: A measurement of D-0 meson production by the LHCb experiment in its fixed-target configuration is presented. The production of D-0 mesons is studied with a beam of 2.5 TeV protons colliding on a gaseous neon target at rest, corresponding to a nucleon-nucleon centre-of-mass energy of root s(NN) = 68.5 GeV. The sum of the D-0 and (D-0) over bar production cross-section in pNe collisions in the centre-of-mass rapidity range y(star) is an element of[-2.29, 0] is found to be sigma(y star is an element of[-2.29, 0])(D0) = 48.2 +/- 0.3 +/- 4.5 μb/nucleon where the first uncertainty is statistical and the second is systematic. The D-0 – (D-0) over bar production asymmetry is also evaluated and suggests a trend towards negative values at large negative y(star). The considered models do not account precisely for all the features observed in the LHCb data, but theoretical predictions including 1% intrinsic charm and 10% recombination contributions better describe the data than the other models considered.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Measurement of antiproton production from antihyperon decays in <i>p</i>He collisions at √<i>s</i><sub>NN</sub>=110 GeV. Eur. Phys. J. C, 83(6), 543–19pp.
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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