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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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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). A study of CP violation in the decays B± → [K+ K- π+π-]Dh± (h = K, π) and B± → [π+ π- π+ π-]Dh±. Eur. Phys. J. C, 83(6), 547–23pp.
Abstract: The first study of CP violation in the decay mode B-+/- -> [K+K-pi(+)pi(-)](D)h(+/-), with h = K, pi, is presented, exploiting a data sample of proton-proton collisions collected by the LHCb experiment that corresponds to an integrated luminosity of 9fb(-1). The analysis is performed in bins of phase space, which are optimised for sensitivity to local CP asymmetries. CP-violating observables that are sensitive to the angle gamma of the Unitarity Triangle are determined. The analysis requires external information on charm-decay parameters, which are currently taken from an amplitude analysis of LHCb data, but can be updated in the future when direct measurements become available. Measurements are also performed of phase-space integrated observables for B-+/- -> [K+K-pi(+)pi(-)](D)h(+/-) and B-+/- -> [pi(+)pi(-)pi(+)pi(-)](D)h(+/-) decays.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Observation of new excited Bs0 states. Eur. Phys. J. C, 81(7), 601–11pp.
Abstract: A structure is observed in the B +/- K -/+ mass spectrum in a sample of proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9 fb-1. The structure is interpreted as the result of overlapping excited Bs0</mml:msubsup> states. With high significance, a two-peak hypothesis provides a better description of the data than a single resonance. Under this hypothesis the masses and widths of the two states, assuming they decay directly to B +/- K -/+, are determined to be m1 = 6063.5 +/- 1.2 (stat) +/- 0.8 (syst) MeV
Gamma 1 = 26 +/- 4 (stat) +/- 4 (syst) MeV
m2 = 6114 +/- 3 (stat) +/- 5 (syst) MeV
Gamma 2 = 66 +/- 18 (stat) +/- 21 (syst) MeV
Alternative values assuming a decay through B +/- K -/+, with a missing photon from the B +/- -> B +/- gamma decay, which are shifted by approximately 45 MeV, are also determined. The possibility of a single state decaying in both channels is also considered. The ratio of the total production cross-section times branching fraction of the new states relative to the previously observed Bs20 state is determined to be 0.87 +/- 0.15 (stat)+/- 0.19 (syst).
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Gorkavenko, V., Jashal, B. K., Kholoimov, V., Kyselov, Y., Mendoza, D., Ovchynnikov, M., et al. (2024). LHCb potential to discover long-lived new physics particles with lifetimes above 100 ps. Eur. Phys. J. C, 84(6), 608–15pp.
Abstract: For years, it has been believed that the main LHC detectors can play only a limited role of a lifetime frontier experiment exploring the parameter space of long-lived particles (LLPs)-hypothetical particles with tiny couplings to the Standard Model. This paper demonstrates that the LHCb experiment may become a powerful lifetime frontier experiment if it uses the new Downstream algorithm reconstructing tracks that do not allow hits in the LHCb vertex tracker. In particular, for many LLP scenarios, LHCb may be as sensitive as the proposed experiments beyond the main LHC detectors for various LLP models, including heavy neutral leptons, dark scalars, dark photons, and axion-like particles.
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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). 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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Garcia Martin, L. M., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Roy, S., Sain, R., et al. (2019). Radiative b-baryon decays to measure the photon and b-baryon polarization. Eur. Phys. J. C, 79(7), 634–10pp.
Abstract: The radiative decays of b-baryons facilitate the direct measurement of photon helicity in b -> s gamma transitions thus serving as an important test of physics beyond the Standard Model. In this paper we analyze the complete angular distribution of ground state b-baryon radiative decays to multibody final states assuming an initially polarized b-baryon sample. Our sensitivity study suggests that the photon polarization asymmetry can be extracted to a good accuracy along with a simultaneous measurement of the initial b-baryon polarization. With higher yields of b-baryons, achievable in subsequent runs of the Large Hadron Collider (LHC), we find that the photon polarization measurement can play a pivotal role in constraining different 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). J/ψ and D0 production in √s_NN=68.5 GeV PbNe collisions. Eur. Phys. J. C, 83(7), 658–11pp.
Abstract: The firstmeasurement of J/psi and D-0 production in PbNe collisions by the LHCb experiment in its fixed-target configuration is reported. The production of J/psi and D-0 mesons is studied with a beam of lead ions with an energy of 2.5 TeV per nucleon colliding on gaseous neon targets at rest, corresponding to a nucleon-nucleon centre-of-mass energy of root s(NN) = 68.5 GeV. The J/psi/D-0 production crosssection ratio is studied as a function of rapidity, transverse momentum and collision centrality. These data are compared with measurements from pNe collisions at the same energy and showno difference in the observed J/psi suppression trend when comparing pNe and PbNe peripheral collisions with PbNe central collisions.
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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 D*(2007)0 → μ+ μ- in B- → π- μ+ μ- decays. Eur. Phys. J. C, 83(7), 666–14pp.
Abstract: The very rare D*(2007)(0) -> mu(+) mu(-) decay is searched for by analysing B- -> pi (-) mu(+) mu(-) decays. The analysis uses a sample of beautymesons produced in protonproton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb(-1). The signal signature corresponds to simultaneous peaks in the mu(+) mu(-) and pi(-) mu(+) mu(-) invariant masses. No evidence for an excess of events over background is observed and an upper limit is set on the branching fraction of the decay at B(D-*(2007)(0) -> mu(+) mu(-)) < 2.6 x 10(-8) at 90% confidence level. This is the first limit on the branching fraction of D*(2007)(0) -> mu(+) mu(-) decays and the most stringent limit on D* (2007)(0) decays to leptonic final states. The analysis is the first search for a rare charm-meson decay exploiting production via beauty decays.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Search for the rare decay B+ -> mu(+) mu(-) mu(+)nu(mu). Eur. Phys. J. C, 79(8), 675–12pp.
Abstract: A search for the rare leptonic decay B +. μ+ μ- μ+.mu is performed using proton- proton collision data corresponding to an integrated luminosity of 4.7 fb – 1 collected by the LHCb experiment. The search is carried out in the region where the lowest of the two μ+ μ- mass combinations is below 980 MeV/ c2. The data are consistent with the background- only hypothesis and an upper limit of 1.6x10 – 8 at 95% confidence level is set on the branching fraction in the stated kinematic region.
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