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). Improved Measurement of CP Violation Parameters in B0s → J/ψ K+ K- Decays in the Vicinity of the φ(1020) Resonance. Phys. Rev. Lett., 132(5), 051802–12pp.
Abstract: The decay-time-dependent CP asymmetry in B0s -> J=psi(-> mu+mu-)K+K- decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 6 fb-1, collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 B0s signal decays with an invariant K+K- mass in the vicinity of the phi(1020) resonance, the CP-violating phase phi s is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B0s-B over bar 0s system, Delta Gamma s, and the difference of the average B0s and B0 meson decay widths, Gamma s – Gamma d. The values obtained are phi s = -0.039 +/- 0.022 +/- 0.006 rad, Delta Gamma s = 0.0845 +/- 0.0044 +/- 0.0024 ps-1, and -0.0015 +/- 0.0014 ps-1, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase phi s is also measured independently for each polarization state of the K+K- system and shows no evidence for polarization dependence.
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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). Study of High-Transverse-Momentum Higgs Boson Production in Association with a Vector Boson in the qqbb Final State with the ATLAS Detector. Phys. Rev. Lett., 132(13), 131802–23pp.
Abstract: This Letter presents the first study of Higgs boson production in association with a vector boson (V = W or Z) in the fully hadronic qqbb final state using data recorded by the ATLAS detector at the LHC in ffiffiproton-proton collisions at root root s= 13 TeV and corresponding to an integrated luminosity of 137fb(-1). The vector bosons and Higgs bosons are each reconstructed as large-radius jets and tagged using jet substructure techniques. Dedicated tagging algorithms exploiting b-tagging properties are used to identify jets consistent with Higgs bosons decaying into b (b) over bar. Dominant backgrounds from multijet production are determined directly from the data, and a likelihood fit to the jet mass distribution of Higgs boson candidates is used to extract the number of signal events. The VH production cross section is measured inclusively and differentially in several ranges of Higgs boson transverse momentum: 250-450, 450-650, and greater than 650 GeV. The inclusive signal yield relative to the standard model expectation is observed to be μ= 1.4(-0.9)(+1.0) and the corresponding cross section is 3.1 +/- 1.3(stat)(-1.4)(+1.8) (syst) pb.
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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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NA64 Collaboration(Andreev, Y. M. et al), Molina Bueno, L., & Tuzi, M. (2024). First Results in the Search for Dark Sectors at NA64 with the CERN SPS High Energy Muon Beam. Phys. Rev. Lett., 132(21), 211803–7pp.
Abstract: We report the first search for dark sectors performed at the NA64 experiment employing a high energy muon beam and a missing energy-momentum technique. Muons from the M2 beamline at the CERN Super Proton Synchrotron with a momentum of 160 GeV/c are directed to an active target. The signal signature consists of a single scattered muon with momentum < 80 GeV/c in the final state, accompanied by missing energy, i.e., no detectable activity in the downstream calorimeters. For a total dataset of (1.98 +/- 0.02) x 10(10) muons on target, no event is observed in the expected signal region. This allows us to set new limits on the remaining (m(Z)'; g(Z)') parameter space of a new Z' (L-mu – L-tau) vector boson which could explain the muon (g – 2)(mu) anomaly. Additionally, our study excludes part of the parameter space suggested by the thermal dark matter relic abundance. Our results pave the way to explore dark sectors and light dark matter with muon beams in a unique and complementary way to other experiments.
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Belen Galan, M., Alvarez-Ruso, L., Rafi Alam, M., Ruiz Simo, I., & Vicente Vacas, M. J. (2024). Cabibbo suppressed hyperon production off nuclei induced by antineutrinos. Phys. Rev. D, 109(3), 033001–13pp.
Abstract: In this work, we study the production of E and A hyperons in strangeness -changing AS = -1 chargedcurrent interactions of muon antineutrinos on nuclear targets. At the nucleon level, besides quasielastic scattering, we consider the inelastic mechanism in which a pion is produced alongside the hyperon. Its relevance for antineutrinos with energies below 2 GeV is conveyed in integrated and differential cross sections. We observe that the distributions on the angle between the hyperon and the final lepton are clearly different for quasielastic and inelastic processes. Hyperon final -state interactions, modeled with an intranuclear cascade, lead to a significant transfer from primary produced E's into final A's. They also cause considerable energy loss, which is apparent in hyperon energy distributions. We have investigated A production off 40Ar in the conditions of the recently reported MicroBooNE measurement. We find that the A pi contribution, dominated by E*(1385) excitation, accounts for about one third of the cross section.
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King, S. F., Marfatia, D., & Rahat, M. H. (2024). Toward distinguishing Dirac from Majorana neutrino mass with gravitational waves. Phys. Rev. D, 109(3), 035014–13pp.
Abstract: We propose a new method toward distinguishing the Dirac versus Majorana nature of neutrino masses from the spectrum of gravitational waves (GWs) associated with neutrino mass genesis. Motivated by the principle of generating small neutrino masses without tiny Yukawa couplings, we assume generic seesaw mechanisms for both Majorana and Dirac neutrino masses. For Majorana neutrinos, we further assume a spontaneously broken gauged U(1)B-L symmetry, independently of the type of Majorana seesaw mechanism, which gives a cosmic string induced GW signal flat over a wide range of frequencies. For Dirac neutrinos, we assume the spontaneous breaking of a Z2 symmetry, the minimal symmetry choice associated with all Dirac seesaw mechanisms, which is softly broken, generating a peaked GW spectrum from the annihilation of the resulting domain walls. In fact, the GW spectra for all types of Dirac seesaws with such a broken Z2 symmetry are identical, subject to a mild caveat. As an illustrative example, we study the simplest respective type-I seesaw mechanisms, and show that the striking difference in the shapes of the GW spectra can help differentiate between these Dirac and Majorana seesaws, complementing results of neutrinoless double beta decay experiments. We also discuss detailed implications of the recent NANOGrav data for Majorana and Dirac seesaw models.
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Celestino-Ramirez, J. M., Escrihuela, F. J., Flores, L. J., & Miranda, O. G. (2024). Testing the nonunitarity of the leptonic mixing matrix at FASERv and FASERv2. Phys. Rev. D, 109(1), L011705–6pp.
Abstract: The FASERv experiment has detected the first neutrino events coming from LHC. Near future highstatistic neutrino samples will allow us to search for new physics within the neutrino sector. Motivated by the forthcoming promising FASERv neutrino data, and its successor, FASERv2, we study its potential for testing the unitarity of the neutrino lepton mixing matrix. Although it would be challenging for FASERv and FASERv2 to have strong constraints on this kind of new physics, we discuss its role in contributing to a future improved global analysis.
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Feijoo, A., Dai, L. R., Abreu, L. M., & Oset, E. (2024). Correlation function for the Tbb state: Determination of the binding, scattering lengths, effective ranges, and molecular probabilities. Phys. Rev. D, 109(1), 016014–8pp.
Abstract: We perform a study of the (B*+B0), (BB+)-B-*0 correlation functions using an extension of the local hidden gauge approach which provides the interaction from the exchange of light vector mesons and gives rise to a bound state of these components in I = 0 with a binding energy of about 21 MeV. After that, we face the inverse problem of determining the low energy observables, scattering length and effective range for each channel, the possible existence of a bound state, and, if found, the couplings of such a state to each (B*+B0), (BB+)-B-*0 component as well as the molecular probabilities of each of the channels. We use the bootstrap method to determine these magnitudes and find that, with errors in the correlation function typical of present experiments, we can determine all these magnitudes with acceptable precision. In addition, the size of the source function of the experiment from where the correlation functions are measured can be also determined with a high precision.
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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). Test of lepton flavor universality using B0→D*−τ+ντ decays with hadronic τ channels. Phys. Rev. D, 108, 012018–18pp.
Abstract: The branching fraction B(B0→D*−τ+ντ) is measured relative to that of the normalization mode B0→D*−π+π−π+ using hadronic τ+→π+π−π+(π0)¯ντ decays in proton-proton collision data at a center-of-mass energy of 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb−1. The measured ratio is B(B0→D*−τ+ντ)/B(B0→D*−π+π−π+)=1.70±0.10+0.11−0.10, where the first uncertainty is statistical and the second is related to systematic effects. Using established branching fractions for the B0→D*−π+π−π+ and B0→D*−μ+νμ modes, the lepton universality test R(D*−)≡B(B0→D*−τ+ντ)/B(B0→D*−μ+νμ) is calculated, R(D*−)=0.247±0.015±0.015±0.012, where the third uncertainty is due to the uncertainties on the external branching fractions. This result is consistent with the Standard Model prediction and with previous measurements.
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Albaladejo, M., Nieves, J., & Ruiz Arriola, E. (2023). Femtoscopic signatures of the lightest S-wave scalar open-charm mesons. Phys. Rev. D, 108, 014020–7pp.
Abstract: We predict femtoscopy correlation functions for S-wave D(s)ϕ pairs of lightest pseudoscalar open-charm mesons and Goldstone bosons from next-to-leading-order unitarized heavy-meson chiral perturbation theory amplitudes. The effect of the two-state structure around 2300 MeV can be clearly seen in the (S,I)=(0,1/2) Dπ, Dη, and Ds¯K correlation functions, while in the scalar-strange (1,0) sector, the D∗s0(2317)± state lying below the DK threshold produces a depletion of the correlation function near threshold. These exotic states owe their existence to the nonperturbative dynamics of Goldstone-boson scattering off D(s). The predicted correlation functions could be experimentally measured and will shed light into the hadron spectrum, confirming that it should be viewed as more than a collection of quark model states.
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