|
|
BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2017). Measurement of the inclusive electron spectrum from B meson decays and determination of vertical bar V-ub vertical bar. Phys. Rev. D, 95(7), 072001–23pp.
Abstract: Based on the full BABAR data sample of 466.5 million B (B) over bar pairs, we present measurements of the electron spectrum from semileptonic B meson decays. We fit the inclusive electron spectrum to distinguish Cabibbo-Kobayashi-Maskawa (CKM) suppressed B -> X(u)ev decays from the CKM-favored B -> X(u)ev decays, and from various other backgrounds, and determine the total semileptonic branching fraction B(B -> X(u)ev) = (10.34 +/- 0.04(stat) +/- 0.26(syst))%, averaged over B-+/- and B-0 mesons. We determine the spectrum and branching fraction for charmless B -> X(u)ev decays and extract the CKM element vertical bar V-ub vertical bar, by relying on four different QCD calculations based on the heavy quark expansion. While experimentally, the electron momentum region above 2.1 GeV/c is favored, because the background is relatively low, the uncertainties for the theoretical predictions are largest in the region near the kinematic endpoint. Detailed studies to assess the impact of these four predictions on the measurements of the electron spectrum, the branching fraction, and the extraction of the CKM matrix element vertical bar V-ub vertical bar are presented, with the lower limit on the electron momentum varied from 0.8 GeV/c to the kinematic endpoint. We determine V-ub vertical bar using each of these different calculations and find, vertical bar V-ub vertical bar = (3.794 +/- 0.107(exp) (+0.292)(-0.219) (SF) (+0.078)(-0.068)theory) x 10(-3) (De Fazio and Neubert), (4.563 +/- 0.126(exp) (+0.230)(+0.162)(-0.208)(-0.163)theory) x 10(-3) (Bosch, Lange, Neubert, and Paz), (3.959 +/- 0.104(exp -0.154)(SF-0.079)(+0.164)(+0.042) theory )x 10(-3) (Gambino, Giordano, Ossola, and Uraltsev), (3.848 +/- 0.108(exp -0.070)(theory)(+0.084)) x 10(-3) (dressed gluon exponentiation), where the stated uncertainties refer to the experimental uncertainties of the partial branching fraction measurement, the shape function parameters, and the theoretical calculations.
|
|
|
|
Dombos, A. C., Spyrou, A., Naqvi, F., Quinn, S. J., Liddick, S. N., Algora, A., et al. (2019). beta-decay half-lives of neutron-rich nuclides in the A=100-110 mass region. Phys. Rev. C, 99(1), 015802–8pp.
Abstract: beta-decay half-lives of neutron-rich nuclides in the A = 100-110 mass region have been measured using an implantation station installed inside of the Summing NaI(T1) (SuN) detector at the National Superconducting Cyclotron Laboratory. Accurate half-lives for these nuclides are important for nuclear astrophysics, nuclear structure, and nuclear technology. The half-lives from the present work are compared with previous measurements, showing overall good agreement.
|
|
|
|
Sarriguren, P., Algora, A., & Kiss, G. (2018). beta-decay properties of neutron-rich Ca, Ti, and Cr isotopes. Phys. Rev. C, 98(2), 024311–10pp.
Abstract: beta-decay properties of neutron-rich Ca, Ti, and Cr isotopes are studied within a deformed proton-neutron quasiparticle random-phase approximation. The underlying mean field is described self-consistently from deformed Skyrme Hartree-Fock calculations with pairing correlations. Residual spin-isospin interactions in the particle-hole and particle-particle channels are also included in the formalism. The energy distributions of the Gamow-Teller strength, the beta-decay feedings, the beta-decay half-lives, and the beta-delayed neutron emission probabilities are discussed and compared with other theoretical results, as well as with the available experimental information. The evolution of these nuclear beta-decay properties is investigated in isotopic chains in a search for structural changes. A reliable estimate of the beta-decay properties in this mass region is valuable information for evaluating decay rates in astrophysical scenarios.
|
|
|
|
Yokoyama, R. et al, Tain, J. L., Algora, A., Agramunt, J., Domingo-Pardo, C., Morales, A. I., et al. (2023). β-delayed neutron emissions from N > 50 gallium isotopes. Phys. Rev. C, 108(6), 064307–15pp.
Abstract: beta-delayed gamma-neutron spectroscopy has been performed on the decay of A=84 to 87 gallium isotopes at the RI-beam Factory at the RIKEN Nishina Center using a high-efficiency array of 3He neutron counters (BRIKEN). beta-2n-gamma events were measured in the decays of all of the four isotopes for the first time, which is direct evidence for populating the excited states of two-neutron daughter nuclei. Detailed decay schemes with the gamma branching ratios were obtained for these isotopes, and the neutron emission probabilities (P-xn) were updated from the previous study. Hauser-Feshbach statistical model calculations were performed to understand the experimental branching ratios. We found that the P-1n and P-2n values are sensitive to the nuclear level densities of 1n daughter nuclei and showed that the statistical model reproduced the P-2n/P-1n ratio better when experimental levels plus shell-model level densities fit by the Gilbert-Cameron formula were used as the level-density input. We also showed the neutron and gamma branching ratios are sensitive to the ground-state spin of the parent nucleus. Our statistical model analysis suggested J <= 3 for the unknown ground-state spin of the odd-odd nucleus Ga-86, from the I gamma(4(+)-> 2(+))/I-gamma(2(+)-> 0(+)) ratio of Ga-84 and the P-2n/P-1n ratio. These results show the necessity of detailed understanding of the decay scheme, including data from neutron spectroscopy, in addition to gamma measurements of the multineutron emitters.
|
|
|
|
Dimitriou, P. et al, Tain, J. L., & Algora, A. (2021). Development of a Reference Database for Beta-Delayed Neutron Emission. Nucl. Data Sheets, 173, 144–238.
Abstract: Beta-delayed neutron emission is important for nuclear structure and astrophysics as well as for reactor applications. Significant advances in nuclear experimental techniques in the past two decades have led to a wealth of new measurements that remain to be incorporated in the databases. We report on a coordinated effort to compile and evaluate all the available beta-delayed neutron emission data. The different measurement techniques have been assessed and the data have been compared with semi-microscopic and microscopic-macroscopic models. The new microscopic database has been tested against aggregate total delayed neutron yields, time-dependent group parameters in 6-and 8-group re-presentation, and aggregate delayed neutron spectra. New recommendations of macroscopic delayed-neutron data for fissile materials of interest to applications are also presented.
|
|
|
|
Yokoyama, R. et al, Tain, J. L., Algora, A., Agramunt, J., Domingo-Pardo, C., Morales, A. I., et al. (2019). Strong one-neutron emission from two-neutron unbound states in beta decays of the r-process nuclei Ga-86,Ga-87. Phys. Rev. C, 100(3), 031302–6pp.
Abstract: beta-delayed one-neutron and two-neutron branching ratios (P-1n and P-2n) have been measured in the decay of A = 84 to 87 Ga isotopes at the Radioactive-Isotope Beam Factory (RIBF) at the RIKEN Nishina Center using a high-efficiency array of He-3 neutron counters (BRIKEN). Two-neutron emission was observed in the decay of Ga-84,Ga-85,Ga-87 for the first time and the branching ratios were measured to be P-2n = 1.6(2)%, 1.3(2)%, and 10.2(28)(stat)(5)(sys)%, respectively. One-neutron branching ratio of Ga-87 (P-1n = 81(9)(stat)(8)(sys)%) and half-life of 29(4) ms were measured for the first time. The branching ratios of Ga-86 were also measured to be P-1n = 74(2)(stat)(8)(sys)% and 16.2(9)(stat)(6)(sys)% with better precision than a previous study. The observation that P-1n > P-2n for both Ga-86,Ga-87 was unexpected and is interpreted as a signature of dominating one-neutron emission from the two-neutron unbound excited states in Ge-86,Ge-87. In order to interpret the experimental results, shell-model and Hauser-Feshbach statistical model calculations of delayed particle and gamma-ray emission probabilities were performed. This model framework reproduces the experimental results. The shell model alone predicts P-2n significantly larger than P-1n for the Ga-87 decay, and it is necessary to invoke a statistical description to successfully explain the observation that P-1n > P-2n. Our new results demonstrate the relevance and importance of a statistical description of neutron emission for the prediction of the decay properties of multineutron emitters and that it must be included in the r-process modeling.
|
|
|
|
Ding, G. J., Nath, N., Srivastava, R., & Valle, J. W. F. (2019). Status and prospects of 'bi-large' leptonic mixing. Phys. Lett. B, 796, 162–167.
Abstract: Bi-large patterns for the leptonic mixing matrix are confronted with current neutrino oscillation data. We analyse the status of these patterns and determine, through realistic simulations, the potential of the upcoming long-baseline experiment DUNE in testing bi-large ansatze and discriminating amongst them.
|
|
|
|
Anderson, P. R., Clark, R. D., Fabbri, A., & Good, M. R. R. (2019). Late time approach to Hawking radiation: Terms beyond leading order. Phys. Rev. D, 100(6), 061703–5pp.
Abstract: Black hole evaporation is studied using wave packets for the modes. These allow for approximate frequency and time resolution. The leading order late time behavior gives the well-known Hawking radiation that is independent of how the black hole formed. The focus here is on the higher order terms and the rate at which they damp at late times. Some of these terms carry information about how the black hole formed. A general argument is given which shows that the damping is significantly slower (power law) than what might be naively expected from a stationary phase approximation (exponential). This result is verified by numerical calculations in the cases of 2D and 4D black holes that form from the collapse of a null shell.
|
|
|
|
Arnault, P., Pepper, B., & Perez, A. (2020). Quantum walks in weak electric fields and Bloch oscillations. Phys. Rev. A, 101(6), 062324–12pp.
Abstract: Bloch oscillations appear when an electric field is superimposed on a quantum particle that evolves on a lattice with a tight-binding Hamiltonian (TBH), i.e., evolves via what we call an electric TBH; this phenomenon will be referred to as TBH Bloch oscillations. A similar phenomenon is known to show up in so-called electric discrete-time quantum walks (DQWs) [C. Cedzich et al., Phys. Rev. Lett. 111, 160601 (2013);] this phenomenon will be referred to as DQW Bloch oscillations. This similarity is particularly salient when the electric field of the DQW is weak. For a wide, i.e., spatially extended, initial condition, one numerically observes semiclassical oscillations, i.e., oscillations of a localized particle, for both the electric TBH and the electric DQW. More precisely, the numerical simulations strongly suggest that the semiclassical DQW Bloch oscillations correspond to two counterpropagating semiclassical TBH Bloch oscillations. In this work it is shown that, under certain assumptions, the solution of the electric DQW for a weak electric field and a wide initial condition is well approximated by the superposition of two continuous-time expressions, which are counterpropagating solutions of an electric TBH whose hopping amplitude is the cosine of the arbitrary coin-operator mixing angle. In contrast, if one wishes the continuous-time approximation to hold for spatially localized initial conditions, one needs at least the DQW to be lazy, as suggested by numerical simulations and by the fact that this has been proven in the case of a vanishing electric field [F. W. Strauch, Phys. Rev. A 74, 030301(R) (2006)].
|
|
|
|
ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Femtoscopy with identified charged pions in proton-lead collisions at root s(NN)=5.02 TeV with ATLAS. Phys. Rev. C, 96(6), 064908–38pp.
Abstract: Bose-Einstein correlations between identified charged pions are measured for p+Pb collisions at root s(NN) = 5.02 TeV using data recorded by the ATLAS detector at the CERN Large Hadron Collider corresponding to a total integrated luminosity of 28 nb(-1). Pions are identified using ionization energy loss measured in the pixel detector. Two-particle correlation functions and the extracted source radii are presented as a function of collision centrality as well as the average transverse momentum (k(T)) and rapidity (y*(pi pi)) of the pair. Pairs are selected with a rapidity -2 < y*(pi pi) < 1 and with an average transverse momentum 0.1 < k(T) < 0.8 GeV. The effect of jet fragmentation on the two-particle correlation function is studied, and a method using opposite-charge pair data to constrain its contributions to the measured correlations is described. The measured source sizes are substantially larger in more central collisions and are observed to decrease with increasing pair k(T). A correlation of the radii with the local charged-particle density is demonstrated. The scaling of the extracted radii with the mean number of participating nucleons is also used to compare a selection of initial-geometry models. The cross term R-ol is measured as a function of rapidity, and a nonzero value is observed with 5.1 sigma combined significance for -1 < y*pi pi < 1 in the most central events.
|
|
