Abstract: Background: The Gamow-Teller response of Ar-40 is important for the use of liquid argon as a medium for neutrino detection. An ambiguity about the Gamow-Teller strength for the excitation of 1(+) states at 2290 and 2730 keV in K-40 results in a significant uncertainty for neutrino capture rates. This ambiguity is caused by the large discrepancy observed between strengths extracted from Ar-40(p, n) charge-exchange data and the transition strengths for the analog transitions studied in the beta decay of Ti-40. Purpose: This study was aimed at resolving the ambiguity between the results from the Ar-40(p, n) charge-exchange and Ti-40 beta-decay data. Method: Shell-model calculations in the sd-pf shell with a new interaction (WBMB-C) were used to study differences between the structure of the transitions from Ar-40 and Ti-40. Distorted-wave Born approximation reaction calculations were used to investigate uncertainties in the extraction of Gamow-Teller strength from the Ar-40(p, n) data. New high-resolution data for the Ar-40(He-3,t) reaction were used to gain further insight into the charge-exchange reaction mechanism and to provide more information to test the validity of the shell-model calculations. Results: The shell-model calculations showed that interference between amplitudes associated with pf and sd components to the low-lying Gamow-Teller transitions, in combination with a difference in Coulomb energy shifts for Ar-40 and Ti-40, can produce the differences on the scale of those observed between the Ar-40 charge-exchange and Ti-40 beta-decay data. In combination with the difference in nuclear penetrability of the (p, n) and (He-3,t) probes, the different contributions from amplitudes associated with transitions in the pf and sd shells are likely also responsible for the observed discrepancy between the ratio of the cross sections for the low-lying 1(+) states in the Ar-40(p, n) and Ar-40(He-3,t) data. Conclusions: On the basis of this study, it is recommended to use Gamow-Teller strengths extracted from the Ar-40(p, n) data, not the Ti-40 beta-decay data, for the calculation of neutrino capture rates. Further theoretical studies are required to achieve a consistent quantitative description for the energy differences between low-lying 1(+) states in K-40 and Sc-40 and the experimentally observed Gamow-Teller strengths.

Abstract: We present measurements of the inclusive production of antideuterons in e(+)e(-) annihilation into hadrons at approximate to 10.58 GeV center-of-mass energy and in Upsilon(1S, 2S, 3S) decays. The results are obtained using data collected by the BABAR detector at the PEP-II electron-positron collider. Assuming a fireball spectral shape for the emitted antideuteron momentum, we find B(Upsilon(1S) -> (d) over barX) = (2.81 +/- 0.49(stat)-(+0.20)(0.24)(syst)) x 10(-5), B(Upsilon(2S) -> (d) over barX) = (2.64 +/- 0.11(stat)(-0.21)(+0.26)(syst)) x 10(-5), B(Upsilon(3S) -> (d) over barX) = (2.33 +/- 0.15(stat)(-0.28)(+0.31)(syst)) x 10(-5), and sigma(e(+)e(-) -> (d) over barX) = (9.63 +/- 0.41(stat)(-1.01)(+1.17)(syst) fb.

Abstract: If grand unification is real, searches for baryon-number violation should be included on the list of observables that may reveal information regarding the origin of neutrino masses. Making use of an effective-operator approach and assuming that nature is SU(5) invariant at very short distances, we estimate the consequences of different scenarios that lead to light Majorana neutrinos for low-energy phenomena that violate baryon number minus lepton number (B – L) by two (or more) units, including neutron-antineutron oscillations and B – L violating nucleon decays. We find that, among all possible effective theories of lepton-number violation that lead to nonzero neutrino masses, only a subset is, broadly speaking, consistent with grand unification.

Abstract: The surface detector array of the Pierre Auger Observatory provides information about the longitudinal development of the muonic component of extensive air showers. Using the timing information from the flash analog-to-digital converter traces of surface detectors far from the shower core, it is possible to reconstruct a muon production depth distribution. We characterize the goodness of this reconstruction for zenith angles around 60 degrees and different energies of the primary particle. From these distributions, we define X-max(mu) as the depth along the shower axis where the production of muons reaches maximum. We explore the potentiality of X-max(mu) as a useful observable to infer the mass composition of ultrahigh-energy cosmic rays. Likewise, we assess its ability to constrain hadronic interaction models.

Abstract: New data from the T2K neutrino oscillation experiment produce the most precise measurement of the neutrino mixing parameter theta(23). Using an off-axis neutrino beam with a peak energy of 0.6 GeV and a data set corresponding to 6.57 x 10(20) protons on target, T2K has fit the energy-dependent nu(mu) oscillation probability to determine oscillation parameters. The 68% confidence limit on sin(2)(theta(23)) is 0.514(-0.056)(+0.055) (0.511 +/- 0.055), assuming normal (inverted) mass hierarchy. The best-fit mass-squared splitting for normal hierarchy is Delta m(32)(2) = (2.51 +/- 0.10) x 10(-3) eV(2)/c(4) (inverted hierarchy: Delta m(13)(2) = (2.48 +/- 0.10) x 10(-3) eV(2)/c(4)). Adding a model of multinucleon interactions that affect neutrino energy reconstruction is found to produce only small biases in neutrino oscillation parameter extraction at current levels of statistical uncertainty.