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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2023). Search for pair production of third-generation leptoquarks decaying into a bottom quark and a τ-lepton with the ATLAS detector. Eur. Phys. J. C, 83(11), 1075–35pp.
Abstract: A search for pair-produced scalar or vector leptoquarks decaying into a b-quark and a tau-lepton is presented using the full LHC Run 2 (2015-2018) data sample of 139 fb(-1) collected with the ATLAS detector in proton-proton collisions at a centre-of-mass energy of root s = 13TeV. Events in which at least one tau-lepton decays hadronically are considered, and multivariate discriminants are used to extract the signals. No significant deviations from the Standard Model expectation are observed and 95% confidence-level upper limits on the production cross-section are derived as a function of leptoquark mass and branching ratio B into a tau-lepton and b-quark. For scalar leptoquarks, masses below 1460GeV are excluded assuming B = 100%, while for vector leptoquarks the corresponding limit is 1650GeV (1910GeV) in the minimal-coupling (Yang-Mills) scenario.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2024). A search for R-parity-violating supersymmetry in final states containing many jets in pp collisions at √s=13 TeV with the ATLAS detector. J. High Energy Phys., 05(5), 003–46pp.
Abstract: A search for R-parity-violating supersymmetry in final states with high jet multiplicity is presented. The search uses 140 fb(-1) of proton-proton collision data at root s = 13 TeV collected by the ATLAS experiment during Run 2 of the Large Hadron Collider. The results are interpreted in the context of R-parity-violating supersymmetry models that feature prompt gluino-pair production decaying directly to three jets each or decaying to two jets and a neutralino which subsequently decays promptly to three jets. No significant excess over the Standard Model expectation is observed and exclusion limits at the 95% confidence level are extracted. Gluinos with masses up to 1800 GeV are excluded when decaying directly to three jets. In the cascade scenario, gluinos with masses up to 2340 GeV are excluded for a neutralino with mass up to 1250 GeV.
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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 Rare Decays of D0 Mesons into Two Muons. Phys. Rev. Lett., 131(4), 041804–13pp.
Abstract: A search for the very rare D-0 -> mu(+)mu(-) decay is performed using data collected by the LHCb experiment in proton-proton collisions at root s = 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb(-1). The search is optimized for D-0 mesons from D*(+) -> D-0 pi(+) decays but is also sensitive to D-0 mesons from other sources. No evidence for an excess of events over the expected background is observed. An upper limit on the branching fraction of this decay is set at B(D-0 -> mu(+)mu(-)) < 3.1 x 10(-9) at a 90% C.L. This represents the world's most stringent limit, constraining models of physics beyond the standard model.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2023). Search for lepton-flavour violation in high-mass dilepton final states using 139 fb-1 of pp collisions at √s=13 TeV with the ATLAS detector. J. High Energy Phys., 10(10), 082–50pp.
Abstract: A search is performed for a heavy particle decaying into different-flavour, dilepton final states, using 139 fb(-1) of proton-proton collision data at root s = 13TeV collected in 2015-2018 by the ATLAS detector at the Large Hadron Collider. Final states with electrons, muons and hadronically decaying tau leptons are considered (e mu, e tau or μtau). No significant excess over the Standard Model predictions is observed. Upper limits on the production cross-section are set as a function of the mass of a Z' boson, a supersymmetric tau-sneutrino, and a quantum black-hole. The observed 95% CL lower mass limits obtained on a typical benchmark model Z' boson are 5.0TeV (e mu), 4.0TeV (e tau), and 3.9TeV (mu tau), respectively.
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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. (2024). Measurement of Ξc+ production in pPb collisions at √sNN=8.16 TeV at LHCb. Phys. Rev. C, 109(4), 044901–14pp.
Abstract: A study of prompt Xi(+)(c) production in proton-lead collisions is performed with the LHCb experiment at a centerof-mass energy per nucleon pair of 8.16 TeV in 2016 in pPb and Pbp collisions with an estimated integrated luminosity of approximately 12.5 and 17.4 nb(-1), respectively. The Xi(+)(c) roduction cross section, as well as the Xi(+)(c) to Lambda(+)(c) production cross-section ratio, are measured as a function of the transverse momentum and rapidity and compared to the latest theory predictions. The forward-backward asymmetry is also measured as a function of the Xi(+)(c) ransverse momentum. The results provide strong constraints on theoretical calculation and are a unique input for hadronization studies in different collision systems.
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Alkofer, R., Llanes-Estrada, F. J., & Salas-Bernardez, A. (2024). Spinning pairs: Supporting 3P0 quark-pair creation from Landau-gauge Green's functions. Phys. Rev. D, 109(7), 074015–21pp.
Abstract: Abundant phenomenology suggests that strong decays from relatively low-excitation hadrons into other hadrons proceed by the creation of a light quark-antiquark pair with zero total angular momentum, the so called 3P0 mechanism originating from a scalar bilinear. Yet the quantum chromodynamics (QCD) interaction is perturbatively mediated by gluons of spin one, and QCD presents a chirally symmetric Lagrangian. Such scalar decay term must be spontaneously generated upon breaking chiral symmetry. We attempt to reproduce this with the help of the quark-gluon vertex in Landau gauge, whose nonperturbative structure has been reasonably elucidated in the last years, and insertions of a uniform, constant chromoelectric field. This is akin to Schwinger pair production in quantum electrodynamics (QED), and we provide a comparison with its two field-insertions diagram. We find that, the symmetry being cylindrical, the adequate quantum numbers to discuss the production are rather 3E0, 3E1, and 3110 as in diatomic molecules, and we indeed find a sizeable contribution of the third decay mechanism, which may give a rationale for the 3P0 phenomenology, as long as the momentum of the produced pair is at or below the scale of the bare or dynamically generated fermion mass. On the other hand, ultrarelativistic fermions are rather ejected with 3E1 quantum numbers. In QED, our results suggest that 3E0 dominates, whereas the constraint of producing a color singlet in QCD leads to 3110 dominance at sub-GeV momenta.
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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. (2024). Amplitude Analysis of the B0 -> K*0 μ+μ- Decay. Phys. Rev. Lett., 132(13), 131801–13pp.
Abstract: An amplitude analysis of the B-0 -> K*(0) mu(+)mu(-) decay is presented using a dataset corresponding to an integrated luminosity of 4.7 fb(-1) of pp collision data collected with the LHCb experiment. For the first time, the coefficients associated to short-distance physics effects, sensitive to processes beyond the standard model, are extracted directly from the data through a q(2)-unbinned amplitude analysis, where q(2) is the mu(+)mu(-) invariant mass squared. Long-distance contributions, which originate from nonfactorizable QCD processes, are systematically investigated, and the most accurate assessment to date of their impact on the physical observables is obtained. The pattern of measured corrections to the short-distance couplings is found to be consistent with previous analyses of b- to s-quark transitions, with the largest discrepancy from the standard model predictions found to be at the level of 1.8 standard deviations. The global significance of the observed differences in the decay is 1.4 standard deviations.
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Super-Kamiokande Collaboration(Abe, K. et al), & Molina Sedgwick, S. (2024). Solar neutrino measurements using the full data period of Super-Kamiokande-IV. Phys. Rev. D, 109(9), 092001–44pp.
Abstract: An analysis of solar neutrino data from the fourth phase of Super-Kamiokande (SK-IV) from October 2008 to May 2018 is performed and the results are presented. The observation time of the dataset of SK- IV corresponds to 2970 days and the total live time for all four phases is 5805 days. For more precise solar neutrino measurements, several improvements are applied in this analysis: lowering the data acquisition threshold in May 2015, further reduction of the spallation background using neutron clustering events, precise energy reconstruction considering the time variation of the PMT gain. The observed number of solar neutrino events in 3.49-19.49 MeV electron kinetic energy region during SK-IV is 65, 443(-388)(+390) (stat.) +/- 925(syst.) events. Corresponding B-8 solar neutrino flux is (2.314 +/- 0.014(stat.) +/- 0.040(syst.)) x 106 cm(-2) s(-1), assuming a pure electron-neutrino flavor component without neutrino oscillations. The flux combined with all SK phases up to SK-IV is (2.336 +/- 0.011(stat.) +/- 0.043(syst.)) x 106 cm(-2) s(-1). Based on the neutrino oscillation analysis from all solar experiments, including the SK 5805 days dataset, the best-fit neutrino oscillation parameters are sin(2)theta(12,solar) = 0.306 +/- 0.013 and Delta m(21,solar)(2) = (6.10(-0.81)(+0.95)) x 10(-5) eV(2), with a deviation of about 1.5 sigma from the Delta m(21)(2) parameter obtained by KamLAND. The best-fit neutrino oscillation parameters obtained from all solar experiments and KamLAND are sin(2)theta(12, global) = 0.307 +/- 0.012 and Delta m(21,) (2)(global) = (7.50(-0.18)(+0.19)) x 10(-5) eV(2).
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Bout, R., Busto, J., Cecchini, V., Charpentier, P., Chapellier, M., Dastgheibi-Fard, A., et al. (2024). Perspectives of a single-anode cylindrical chamber operating in ionization mode and high gas pressure. Eur. Phys. J. C, 84(5), 512–14pp.
Abstract: As part of the R2D2 (Rare Decays with Radial Detector) R &D, the use of a gas detector with a spherical or cylindrical cathode, equipped with a single anode and operating at high pressure, was studied for the search of rare phenomena such as neutrinoless double-beta decay. The presented measurements were obtained with a cylindrical detector, covering gas pressures ranging from 1 to 10 bar in argon and 1 to 6 bar in xenon, using both a point-like source of 210 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$<^>{210} $$\end{document} Po (5.3 MeV alpha \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha $$\end{document} ) and a diffuse source of 222 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$<^>{222}$$\end{document} Rn (5.5 MeV alpha \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha $$\end{document} ). Analysis and interpretation of the data were developed using the anodic current waveform. Similar detection performances were achieved with both gases, and comparable energy resolutions were measured with both sources. As long as the purity of the gas was sufficient, no significant degradation of the measured energy was observed by increasing the pressure. At the highest operating pressure, an energy resolution better than 1.5% full-width at half-maximum (FWHM) was obtained for both gaseous media, although optimal noise conditions were not reached.
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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). First observation of the B+ → Ds+ Ds- K+ decay. Phys. Rev. D, 108(3), 034012–14pp.
Abstract: B+ -> D-s(+) D-s(-) K+ decay is observed for the first time using proton-proton collision data collected by the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb-1. Its branching fraction relative to that of the B+ -> D-s(+) D-s(-) K+ decay is measured to be B(B+ -> D-s(+) D-s(-) K+)/(KB+ -> D-s(+) D-s(-) K+) = 0.525 +/- 0.0333 +/- 0.027 +/- 0.034; where the first uncertainty is statistical, the second s D-s Kthornthorn systematic, and the third is due to the uncertainties on the branching fractions of the D-s(+/-) -> (KK +/-)-K--/+pi(+/-) and D-+/- -> K--/+pi(+/-)pi(+/-) decays. This measurement fills an experimental gap in the knowledge of the family of Cabibbo-favored (b) over bar -> (b) over barc (c) over bar transitions and opens the path for unique studies of spectroscopy in future.
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