Orrigo, S. E. A. et al, Rubio, B., Gelletly, W., Aguilera, P., Algora, A., Morales, A. I., et al. (2021). beta decay of the very neutron-deficient Ge-60 and Ge-62 nuclei. Phys. Rev. C, 103(1), 014324–12pp.
Abstract: We report here the results of a study of the beta decay of the proton-rich Ge isotopes, Ge-60 and Ge-62, produced in an experiment at the RIKEN Nishina Center. We have improved our knowledge of the half-lives of Ge-62 [73.5(1) ms] and Ge-60 [25.0(3) ms] and its daughter nucleus, Ga-60 [69.4(2) ms]. We measured individual beta-delayed proton and gamma emissions and their related branching ratios. Decay schemes and absolute Fermi and Gamow-Teller transition strengths have been determined. The mass excesses of the nuclei under study have been deduced. A total beta-delayed proton-emission branching ratio of 67(3)% has been obtained for Ge-60. New information has been obtained on the energy levels populated in Ga-60 and on the 1/2(-) excited state in the beta p daughter Zn-59. We extracted a ground state-to-ground state feeding of 85.3(3)% for the decay of Ge-62. Eight new y lines have been added to the deexcitation of levels populated in the Ga-62 daughter.
|
LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). First Observation of the Decay B-s(0) -> K-mu(+)nu(mu) and a Measurement of vertical bar V-ub vertical bar/vertical bar V-cb vertical bar. Phys. Rev. Lett., 126(8), 081804–11pp.
Abstract: The first observation of the suppressed semileptonic B-s(0) -> K-mu(+)nu(mu) decay is reported. Using a data sample recorded in pp collisions in 2012 with the LHCb detector, corresponding to an integrated luminosity of 2 fb(-1), the branching fraction B(B-s(0) -> K-mu(+)nu(mu)) is measured to be [1.06 +/- 0.05(stat) +/- 0.08(syst)] x 10(-4), where the first uncertainty is statistical and the second one represents the combined systematic uncertainties. The decay B-s(0) -> D-s(-)mu(+)nu(mu), where D-s(-) is reconstructed in the final state K+K-pi(-), is used as a normalization channel to minimize the experimental systematic uncertainty. Theoretical calculations on the form factors of the B-s(0) -> K- and B-s(0) -> D-s(-) transitions are employed to determine the ratio of the Cabibbo-Kobayashi-Maskawa matrix elements vertical bar V-ub vertical bar/vertical bar V-cb vertical bar at low and high B-s(0) -> K- momentum transfer.
|
ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., Castillo, F. L., et al. (2021). Medium-Induced Modification of Z-Tagged Charged Particle Yields in Pb plus Pb Collisions at 5.02 TeV with the ATLAS Detector. Phys. Rev. Lett., 126(7), 072301–20pp.
Abstract: The yield of charged particles opposite to a Z boson with large transverse momentum (p(T)) is measured in 260 pb(-1) of pp and 1.7 nb(-1) of Pb + Pb collision data at 5.02 TeV per nucleon pair recorded with the ATLAS detector at the Large Hadron Collider. The Z boson tag is used to select hard-scattered partons with specific kinematics, and to observe how their showers are modified as they propagate through the quarkgluon plasma created in Pb + Pb collisions. Compared with pp collisions, charged-particle yields in Pb + Pb collisions show significant modifications as a function of charged-particle p(T) in a way that depends on event centrality and Z boson p(T). The data are compared with a variety of theoretical calculations and provide new information about the medium-induced energy loss of partons in a p(T) regime difficult to measure through other channels.
|
MoEDAL Collaboration(Acharya, B. et al), Bernabeu, J., Mamuzic, J., Mitsou, V. A., Papavassiliou, J., Ruiz de Austri, R., et al. (2021). First Search for Dyons with the Full MoEDAL Trapping Detector in 13 TeV pp Collisions. Phys. Rev. Lett., 126(7), 071801–7pp.
Abstract: The MoEDAL trapping detector consists of approximately 800 kg of aluminum volumes. It was exposed during run 2 of the LHC program to 6.46 fb(-1) of 13 TeV proton-proton collisions at the LHCb interaction point. Evidence for dyons (particles with electric and magnetic charge) captured in the trapping detector was sought by passing the aluminum volumes comprising the detector through a superconducting quantum interference device (SQUID) magnetometer. The presence of a trapped dyon would be signaled by a persistent current induced in the SQUID magnetometer. On the basis of a Drell-Yan production model, we exclude dyons with a magnetic charge ranging up to five Dirac charges (5g(D)) and an electric charge up to 200 times the fundamental electric charge for mass limits in the range 870-3120 GeV and also monopoles with magnetic charge up to and including 5g(D) with mass limits in the range 870-2040 GeV.
|
T2K Collaboration(Abe, K. et al), Antonova, M., & Cervera-Villanueva, A. (2021). T2K measurements of muon neutrino and antineutrino disappearance using 3.13 x 10(21) protons on target. Phys. Rev. D, 103(1), L011101–9pp.
Abstract: We report measurements by the T2K experiment of the parameters theta(23) and Delta m(32)(2), which govern the disappearance of muon neutrinos and antineutrinos in the three-flavor PMNS neutrino oscillation model at T2K's neutrino energy and propagation distance. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, muon-like events from each beam mode are used to measure these parameters separately for neutrino and antineutrino oscillations. Data taken from 1.49 x 10(21) protons on target (POT) in neutrino mode and 1.64 x 10(21) POT in antineutrino mode are used. The best-fit values obtained by T2K were sin(2)(theta(23)) = 0.51(-0.07)(+0.06) (0.43(-0.05)(+0.21)) and Delta m(32)(2) = 2.47(-0.09)(+0.08) (2.50(-0.13)(+0.18)) x 10(-3) eV(2)/c(4) for neutrinos (antineutrinos). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed. An analysis using an effective two-flavor neutrino oscillation model where the sine of the mixing angle is allowed to take nonphysical values larger than 1 is also performed to check the consistency of our data with the three-flavor model. Our data were found to be consistent with a physical value for the mixing angle.
|
LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Observation of Multiplicity Dependent Prompt chi(c1) (3872) and psi (2S) Production in pp Collisions. Phys. Rev. Lett., 126(9), 092001–11pp.
Abstract: The production of chi(c1)(3872) and psi(2S) hadrons is studied as a function of charged particle multiplicity in pp collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 2 fb(-1). For both states, the fraction that is produced promptly at the collision vertex is found to decrease as charged particle multiplicity increases. The ratio of chi(c1) (3872) to psi(2S) cross sections for promptly produced particles is also found to decrease with multiplicity, while no significant dependence on multiplicity is observed for the equivalent ratio of particles produced away from the collision vertex in b-hadron decays. This behavior is consistent with a calculation that models the chi(c1) (3872) structure as a compact tetraquark. Comparisons with model calculations and implications for the binding energy of the chi(c1)(3872) state are discussed.
|
LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Measurement of CP Violation in the Decay B plus -> K+ pi(0). Phys. Rev. Lett., 126(9), 091802–11pp.
Abstract: A measurement of CP violation in the decay B+ -> K+pi(0) is reported using data corresponding to an integrated luminosity of 5.4 fb- 1 collected with the LHCb experiment at a center-of-mass energy of root s = 13 TeV. The CP asymmetry is measured to be 0.025 +/- 0.015 +/- 0.006 +/- 0.003, where the uncertainties are statistical, systematic, and due to an external input. This is the most precise measurement of this quantity. It confirms and significantly enhances the observed anomalous difference between the direct CP asymmetries of the B-0 -> K+pi(-) and B+ -> K+pi 0 decays, known as the K pi puzzle.
|
Han, C., Lopez-Ibañez, M. L., Melis, A., Vives, O., & Yang, J. M. (2021). Anomaly-free leptophilic axionlike particle and its flavor violating tests. Phys. Rev. D, 103(3), 035028–7pp.
Abstract: Motivated by the recent Xenon1T result, we study a leptophilic flavor-dependent anomaly-free axionlike particle (ALP) and its effects on charged-lepton flavor violation. We present two representative models. The first one considers that the ALP origins from the flavon that generates the charged-lepton masses. The second model assumes a larger flavor symmetry such that more general mixings in the charged-lepton are possible, while maintaining flavor-dependent ALP couplings. We find that a keV ALP explaining the Xenon1T result is still viable for lepton flavor violation and stellar cooling astrophysical limits. On the other hand, if the Xenon1T result is confirmed, future charged-lepton flavor violation measurements can be complementary to probe such a possibility.
|
Roca, L., & Oset, E. (2021). Scalar resonances in the D+ -> K-K+K+ decay. Phys. Rev. D, 103(3), 034020–9pp.
Abstract: We study theoretically the resonant structure of the double Cabibbo suppressed D+ -> K-K+K+ decay. We start from an elementary production diagram, considered subleading in previous approaches, which cannot produce a final K-K+ pair at the tree level but which we show to be able to provide the strength of the decay through final meson-meson state interaction. The different meson-meson elementary productions are related through SU(3), and the final rescattering is implemented from a suitable implementation of unitary extensions of chiral perturbation theory, which generate dynamically the scalar resonances1 f(0)(980) and a(0)(980). We obtain a good agreement with recent experimental data from the LHCb Collaboration with a minimal freedom in the fit and show the dominance of the a(0)(980) contribution close to the threshold of the K-K+ spectrum.
|
Dombos, A. C. et al, & Algora, A. (2021). Total absorption spectroscopy of the beta decay of Zr-101,102 and Tc-109. Phys. Rev. C, 103(2), 025810–20pp.
Abstract: The beta decay of Zr-101,Zr-102 and Tc-109 was studied using the technique of total absorption spectroscopy. The experiment was performed at the National Superconducting Cyclotron Laboratory using the Summing NaI(Tl) (SuN) detector in the first-ever application of total absorption spectroscopy with a fast beam produced via projectile fragmentation. The beta-decay feeding intensity and Gamow-Teller transition strength distributions were extracted for these three decays. The extracted distributions were compared to three different quasiparticle random-phase approximation (QRPA) models based on different mean-field potentials. A comparison with calculations from one of the QRPA models was performed to learn about the ground-state shape of the parent nucleus. For Zr-101 and Zr-102, calculations assuming a pure shape configuration (oblate or prolate) were not able to reproduce the extracted distributions. These results may indicate that some type of mixture between oblate and prolate shapes is necessary to reproduce the extracted distributions. For Tc-109, a comparison of the extracted distributions with QRPA calculations suggests a dominant oblate configuration. The other two QRPA models are commonly used to provide beta-decay properties in r-process network calculations. This work shows the importance of making comparisons between the experimental and theoretical beta-decay distributions, rather than just half-lives and beta-delayed neutron emission probabilities, as close to the r-process path as possible.
|
