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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Albaladejo, M., Gonzàlez-Solís, S., Bibrzycki, L., Fernández-Ramírez, C., Hammoud, N., Mathieu, V., et al. (2023). Khuri-Treiman analysis of J/Psi -> pi+ pi-pi0. Phys. Rev. D, 108(1), 014035–11pp.
Abstract: We study the decay J=& psi; & RARR; & pi; thorn & pi;-& pi;0 within the framework of the Khuri-Treiman equations. We find that the BESIII experimental dipion mass distribution in the & rho;o770 thorn -region is well reproduced with a once-subtracted P-wave amplitude. Furthermore, we show that F-wave contributions to the amplitude improve the description of the data in the & pi;& pi; mass region around 1.5 GeV. We also present predictions for the J=& psi; & RARR; & pi;0 & gamma;* transition form factor.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cantero, J., et al. (2023). Search for displaced photons produced in exotic decays of the Higgs boson using 13 TeV pp collisions with the ATLAS detector. Phys. Rev. D, 108(3), 032016–33pp.
Abstract: A search is performed for delayed and nonpointing photons originating from the displaced decay of a neutral long-lived particle (LLP). The analysis uses the full run 2 dataset of proton-proton collisions delivered by the LHC at a center-of-mass energy of pffisffi 1/4 13 TeV between 2015 and 2018 and recorded by the ATLAS detector, corresponding to an integrated luminosity of 139 fb-1. The capabilities of the ATLAS electromagnetic calorimeter are exploited to precisely measure the arrival times and trajectories of photons. The results are interpreted in a scenario where the LLPs are pair produced in exotic decays of the 125 GeV Higgs boson, and each LLP subsequently decays into a photon and a particle that escapes direct detection, giving rise to missing transverse momentum. No significant excess is observed above the expectation due to Standard Model background processes. The results are used to set upper limits on the branching ratio of the exotic decay of the Higgs boson. A model-independent limit is also set on the production of photons with large values of displacement and time delay.
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ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Castillo, F. L., Castillo Gimenez, V., et al. (2023). Measurement of the production of a W boson in association with a charmed hadron in pp collisions at root s=13 TeV with the ATLAS detector . Phys. Rev. D, 108(3), 032012–54pp.
Abstract: The production of a W boson in association with a single charm quark is studied using 140 fb(-1) of vS = 13 TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. ffiffis The charm quark is tagged by the presence of a charmed hadron reconstructed with a secondary-vertex fit. The W boson is reconstructed from the decay to either an electron or a muon and the missing transverse momentum present in the event. The charmed mesons reconstructed are D+ ?K-p+p+ and D*+ ? D0p+ ? (K-p+)p+ and the charge conjugate decays in the fiducial regions where pT(e; mu) > 30 GeV, l?(e; mu)l < 2.5, pT(D(*)) > 8 GeV, and l?(D(*))l < 2.2. The integrated and normalized differential cross sections as a function of the pseudorapidity of the lepton from the W boson decay, and of the transverse momentum of the charmed hadron, are extracted from the data using a profile likelihood fit. The measured total fiducial cross sections are sfidOS-SS(W- + D+) = 50.2 + 0.2(stat)+2.4 -2.3(syst) pb, s(OS-SS) (fid)(W- + D+) = 48.5 + 0.2(stat)+2.3-2.2(syst) pb, sfidOS-SS(W- + D*+) = 51.1 + 0.4(stat)+1.9 -1.8 (syst) pb, and s(OS-SS) (fid)(W+ + D*-) = 50.0 + 0.4(stat)+1.9 -1.8 (syst) pb. Results are compared with the predictions of next-to-leading-order quantum chromodynamics calculations performed using state-of-the-art parton distribution functions. Additionally, the ratio of charm to anticharm production cross sections is studied to probe the s -s- quark asymmetry. The ratio is found to be R+ c = 0.971 + 0.006(stat) + 0.011(syst). The ratio and cross-section measurements are consistent with the predictions obtained with parton distribution function sets that have a symmetric s -s- sea, indicating that any s -s- asymmetry in the Bjorken-x region relevant for this measurement is small.
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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 lepton universality parameters in B+ -> K+ l+ l- and B0 -> K0 l+ l- decays. Phys. Rev. D, 108(3), 032002–46pp.
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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