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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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Belle II Collaboration(Abudinen, F. et al), & Marinas, C. (2022). B-flavor tagging at Belle II. Eur. Phys. J. C, 82(4), 283–29pp.
Abstract: We report on new flavor tagging algorithms developed to determine the quark-flavor content of bottom (B) mesons at Belle II. The algorithms provide essential inputs for measurements of quark-flavor mixing and charge-parity violation. We validate and evaluate the performance of the algorithms using hadronic B decays with flavor-specific final states reconstructed in a data set corresponding to an integrated luminosity of 62.8 fb(-1), collected at the gamma(4S) resonance with the Belle II detector at the SuperKEKB collider. We measure the total effective tagging efficiency to be epsilon(eff) = (30.0 +/- 1.2(stat) +/- 0.4(syst))% for a category-based algorithm and epsilon(eff) = (28.8 +/- 1.2(stat) +/- 0.4(syst))% for a deep-learning-based algorithm.
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DELPHI Collaboration(Abdallah, J. et al), Costa, M. J., Ferrer, A., Fuster, J., Garcia, C., Oyanguren, A., et al. (2011). Search for single top quark production via contact interactions at LEP2. Eur. Phys. J. C, 71(2), 1555–13pp.
Abstract: Single top quark production via four-fermion contact interactions associated to flavour-changing neutral currents was searched for in data taken by the DELPHI detector at LEP2. The data were accumulated at centre-of-mass energies ranging from 189 to 209 GeV, with an integrated luminosity of 598.1 pb(-1). No evidence for a signal was found. Limits on the energy scale Lambda, were set for scalar-, vector- and tensor-like coupling scenarios.
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DELPHI Collaboration(Abdallah, J. et al), Costa, M. J., Ferrer, A., Fuster, J., Garcia, C., Oyanguren, A., et al. (2011). A study of the b-quark fragmentation function with the DELPHI detector at LEP I and an averaged distribution obtained at the Z Pole. Eur. Phys. J. C, 71(2), 1557–29pp.
Abstract: The nature of b-quark jet hadronisation has been investigated using data taken at the Z peak by the DELPHI detector at LEP. Two complementary methods are used to reconstruct the energy of weakly decaying b-hadrons, E-B(weak). The average value of x(B)(weak) = E-B(weak)/E-beam is measured to be 0.699 +/- 0.011. The resulting x(B)(weak) distribution is then analysed in the framework of two choices for the perturbative contribution (parton shower and Next to Leading Log QCD calculation) in order to extract measurements of the non-perturbative contribution to be used in studies of b-hadron production in other experimental environments than LEP. In the parton shower framework, data favour the Lund model ansatz and corresponding values of its parameters have been determined within PYTHIA 6.156 from DELPHI data: a = 1.84(-0.21)(+0.23) and b = 0.642(-0.063)(+0.073) GeV-2, with a correlation factor rho = 92.2%. Combining the data on the b-quark fragmentation distributions with those obtained at the Z peak by ALEPH, OPAL and SLD, the average value of x(B)(weak) is found to be 0.7092 +/- 0.0025 and the non-perturbative fragmentation component is extracted. Using the combined distribution, a better determination of the Lund parameters is also obtained: a = 1.48(-0.10)(+0.11) and b = 0.509(-0.023)(+0.024) GeV-2, with a correlation factor rho = 92.6%.
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T2K Collaboration(Abe, K. et al), Antonova, M., Cervera-Villanueva, A., Molina Bueno, L., & Novella, P. (2023). Measurements of neutrino oscillation parameters from the T2K experiment using 3.6 x 10^21 protons on target. Eur. Phys. J. C, 83(9), 782–50pp.
Abstract: The T2K experiment presents new measurements of neutrino oscillation parameters using 19.7(16.3) x 10(20) protons on target (POT) in (anti-)neutrino mode at the far detector (FD). Compared to the previous analysis, an additional 4.7 x 10(20) POT neutrino data was collected at the FD. Significant improvements were made to the analysis methodology, with the near-detector analysis introducing new selections and using more than double the data. Additionally, this is the first T2K oscillation analysis to use NA61/SHINE data on a replica of the T2K target to tune the neutrino flux model, and the neutrino interaction model was improved to include new nuclear effects and calculations. Frequentist and Bayesian analyses are presented, including results on sin(2) theta(13) and the impact of priors on the delta(CP) measurement. Both analyses prefer the normal mass ordering and upper octant of sin(2) theta(23) with a nearly maximally CP-violating phase. Assuming the normal ordering and using the constraint on sin(2) theta(13) from reactors, sin(2) theta(23) = 0.561(-0.032)(+0.021) using Feldman-Cousins corrected intervals, and Delta m(32)(2) = 2.494(-0.058)(+0.041) x 10(-3) eV(2) using constant Delta chi(2) intervals. The CP-violating phase is constrained to delta(CP) = -1.97(-0.70)(+0.97) using Feldman-Cousins corrected intervals, and delta(CP) = 0, pi is excluded at more than 90% confidence level. A Jarlskog invariant of zero is excluded at more than 2 sigma credible level using a flat prior in delta(CP), and just below 2 sigma using a flat prior in sin delta(CP). When the external constraint on sin(2) nu(13) is removed, sin(2) theta(13) = 28.0(-6.5)(+2.8) x 10(-3), in agreement with measurements from reactor experiments. These results are consistent with previous T2K analyses.
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