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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). Amplitude analysis of the D+s → π-π+π+ decay. J. High Energy Phys., 07(7), 204–35pp.
Abstract: A Dalitz plot analysis of the D-s(+) -> pi(-)pi(+)pi(+) decay is presented. The analysis is based on proton-proton collision data recorded by the LHCb experiment at a centre-of-mass energy of 8TeV and corresponding to an integrated luminosity of 1.5 fb(-1). The resonant structure of the decay is obtained using a quasi-model-independent partial-wave analysis, in which the pi(+)pi(-) S-wave amplitude is parameterised as a generic complex function determined by a fit to the data. The S-wave component is found to be dominant, followed by the contribution from spin-2 resonances and a small contribution from spin-1 resonances. The latter includes the first observation of the D-s(+) -> omega(782)pi(+) channel in the D-s(+) -> pi(-)pi(+)pi(+) decay. The resonant structures of the D-s(+) -> pi(-)pi(+)pi(+) and D+ -> pi(-)pi(+)pi(+) decays are compared, providing information about the mechanisms for the hadron formation 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). Measurement of the CKM angle γ with B± → D[K∓π±π±π∓] h± decays using a binned phase-space approach. J. High Energy Phys., 07(7), 138–31pp.
Abstract: The CKM angle gamma is determined from CP-violating observables measured in B-+/- -> D[K--/+pi(+/-)pi(+/-)pi(-/+)]h(+/-), (h = K, pi) decays, where the measurements are performed in bins of the decay phase-space of the D meson. Using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13TeV, corresponding to a total integrated luminosity of 9 fb(-1), gamma is determined to be gamma = (54.8 (+6.0)(-5.8) (+0.6)(-0.6) (+6.7)(-4.3))degrees, where the first uncertainty is statistical, the second systematic and the third from the external inputs on the coherence factors and strong phases of the D-meson 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). 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). 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 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). Model-independent measurement of charm mixing parameters in Bbar → D0(→ K0Sπ+π-)μ-νbar_μX decays. Phys. Rev. D, 108(5), 052005–17pp.
Abstract: A measurement of charm mixing and CP-violating parameters is reported, using B over bar -> D0(-> K0S pi+pi-)x mu- nu over bar μX decays reconstructed in proton-proton collisions collected by the LHCb experiment during the years 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb-1. The measured mixing and CP-violating parameters are xCP = [4.29 1 1.48(stat) 1 0.26(syst)] x 10-3, yCP = [12.61 1 3.12(stat) 1 0.83(syst)] x 10-3, Ax = [-0.77 1 0.93(stat) 1 0.28(syst)] x 10-3, Ay = [3.01 1 1.92(stat) 1 0.26(syst)] x 10-3. The results are complementary to and consistent with previous measurements. A combination with the recent LHCb analysis of D*+ -> D0(-> K0S pi+ pi-)pi+ decays is reported.
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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). Amplitude analysis of the D+-> pi(-)pi(+)pi(+) decay and measurement of the pi(-)pi(+) S-wave amplitude. J. High Energy Phys., 06(6), 044–28pp.
Abstract: An amplitude analysis of the D+-> (-)pi(+)pi(+) decay is performed with a sample corresponding to 1.5 fb(-1) of integrated luminosity of pp collisions at a centre-of-mass energy root s = 8 TeV collected by the LHCb detector in 2012. The sample contains approximately six hundred thousand candidates with a signal purity of 95%. The resonant structure is studied through a fit to the Dalitz plot where the pi(-)pi(+) S-wave amplitude is extracted as a function of pi(-)pi(+) mass, and spin-1 and spin-2 resonances are included coherently through an isobar model. The S-wave component is found to be dominant, followed by the rho(770)(0)pi(+) and f(2)(1270)pi(+) components. A small contribution from the omega(782) -> pi(-)pi(+) decay is seen for the first time in the D+-> pi(-)pi(+)pi(+) decay.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., Remon Alepuz, C., et al. (2023). Amplitude analysis of the Lambdac+ -> p K- pi+ decay and Lambdac+ baryon polarization measurement in semileptonic beauty hadron decays. Phys. Rev. D, 108(1), 012023–27pp.
Abstract: An amplitude analysis of A+c – pK- & pi;+ decays together with a measurement of the A+c polarization vector in semiOleptonic beauty hadron decays is presented. A sample of 400 000 candidates is selected from proton-proton collisions recorded by the LHCb detector at a center-of-mass energy of 13 TeV. An amplitude model is developed and the resonance fractions as well as two- and three-body decay parameters are reported. The mass and width of the Ao2000 thorn state are also determined. A significant A+c polarization is found. A large sensitivity of the A+c – pK-& pi;+ decay to the polarization is seen, making the amplitude model suitable for A+c polarization measurements in other systems.
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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 the lepton-flavour violating decays B-0 -> K-*0 mu(+/-)e(-/+) and B-s(0)-> phi mu(+/-)e(-/+). J. High Energy Phys., 06(6), 073–25pp.
Abstract: A search for the lepton-flavour violating decays B-0 -> K-*0 μe(-/+) and B-s(0)-> mu(+/-)e(-/+) is presented, using proton-proton collision data collected by the LHCb detector at the LHC, corresponding to an integrated luminosity of 9 fb(-1). No significant signals are observed and upper limits of are set at 90% (95%) confidence level. These results constitute the world's most stringent limits to date, with the limit on the decay B-s(0) -> phi mu(+/-) e(-/+) the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios.
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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 exclusive photoproduction of charmonium in ultra-peripheral lead-lead collisions. J. High Energy Phys., 06(6), 146–25pp.
Abstract: The cross-sections of exclusive (coherent) photoproduction J/psi and (2S) mesons in ultra-peripheral PbPb collisions at a nucleon-nucleon centre-of-mass energy of 5.02TeV are measured using a data sample corresponding to an integrated luminosity of 228 +/- 10 μb(-1), collected by the LHCb experiment in 2018. The differential cross-sections are measured separately as a function of transverse momentum and rapidity in the nucleus-nucleus centre-of-mass frame for J/psi and psi(2S) mesons. The integrated cross-sections are measured to be sigma(coh)(J/psi) = 5.965 +/- 0.059 +/- 0.232 +/- 0.262mb and sigma(coh)(psi(2S)) = 0.923 +/- 0.086 +/- 0.028 +/- 0.040mb, where the first listed uncertainty is statistical, the second systematic and the third due to the luminosity determination. The cross-section ratio is measured to be sigma(coh)(psi(2S)) /sigma(coh)(J/psi) = 0.155 +/- 0.014 +/- 0.003, where the first uncertainty is statistical and the second is systematic. These results are compatible with theoretical predictions.
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