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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), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Measurement of the Z boson production cross-section in proton-lead collisions at root(NN)-N-s=8.16 TeV. J. High Energy Phys., 06(6), 022–37pp.
Abstract: This article presents the first measurement of the differential Z-boson production cross-section in the forward region using proton-lead collisions with the LHCb detector. The dataset was collected at a nucleon-nucleon centre-of-mass energy of root(NN)-N-s = 8.16TeV in 2016, corresponding to an integrated luminosity of 30.8 nb(-1). The forward-backward ratio and the nuclear modification factors are measured together with the differential crosssection as functions of the Z boson rapidity in the centre-of-mass frame, the transverse momentum of the Z boson and a geometric variable phi*. The results are in good agreement with the predictions from nuclear parton distribution functions, providing strong constraining power at small Bjorken-x.
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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). Observation of the B0s → D*+ D*- decay. J. High Energy Phys., 07(7), 119–19pp.
Abstract: The first observation of the B-s(0) -> D*+ D*- decay and the measurement of its branching ratio relative to the B-0 -> D*+ D*(-) decay are presented. The data sample used corresponds to an integrated luminosity of 9 fb(-1) of proton-proton collisions recorded by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV between 2011 and 2018. The decay is observed with more than 10 standard deviations and the time-integrated ratio of branching fractions is determined to be [GRAPHICS] . where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the fragmentation fraction ratio f(s)/f(d). The B-s(0) -> D*(+) D*(-) branching fraction is calculated to be [GRAPHICS] . where the fourth uncertainty is due to the B-0 -> D*(+) D*(-) branching fraction. These results are calculated using the average B-s(0) meson lifetime in simulation. Correction factors are reported for scenarios where either a purely heavy or a purely light B-s(0) eigenstate is considered.
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