arXiv subjects

S. Ando

Publications and source records attributed to S. Ando.

24 records · Page 2Linked to original sources

arXiv2002

Neutrino-deuteron reactions at solar neutrino energies

In interpreting the SNO experiments, accurate estimates of the νd reaction cross sections are of great importance. In our recent work, we have improved our previous calculation by updating some of its inputs and by incorporating the results of a recent effective-field-theoretical calculation. The new cross sections are slightly (\sim 1%) larger than the previously reported values. It is reasonable to assign 1% uncertainty to the νd cross sections reported here; this error estimate does not include radiative corrections.

nucl-th↗

arXiv2002

Neutrino-deuteron reactions at solar neutrino energies

In interpreting the SNO experiments, very accurate estimates of the νd reaction cross sections are of great importance. We improve the previous estimates of our group by updating some of its inputs and by taking into account the results of a recent effective-field-theoretical calculation. The new cross sections are slightly (\sim 1%) larger than the previously reported values. We present arguments that lead to the conclusion that it is reasonable to assign 1% uncertainty to the νd cross sections reported here.

nucl-th↗

arXiv2002

Detectability of the Supernova Relic Neutrinos and Neutrino Oscillation

We investigate the flux and the event rate of the supernova relic neutrino background (SRN) at the SuperKamiokande detector for various neutrino oscillation models with parameters inferred from recent experimental results. A realistic model of neutrino emission from supernova explosions and several models of the cosmic star formation history are adopted in the calculation. The number flux over entire energy range is found to be $11-15 \mathrm{cm^{-2}s^{-1}}$. We discuss the detection possibility of SRN at SuperKamiokande, comparing this SRN flux with other background neutrinos in more detail than previous studies. Even though there is no energy window in which SRN is dominant, we might detect it as the distortion of the other background event. We found in the energy range $17-25 \mathrm{MeV}$ the expected event rate at SuperKamiokande $0.4-0.8 ~\mathrm{yr^{-1}}$. In this range, ten-year observation might enable us to detect SRN signal (at one sigma level) in the case of LMA solar neutrino solution. We also investigate event rate at SNO and KamLAND. Although we can find energy window, the expected event rate is rather small (0.03 yr$^{-1}$ for SNO, 0.1 yr$^{-1}$ for KamLAND).

astro-ph↗

arXiv2002

Gamma-Ray Burst Neutrino Background and Star Formation History in the Universe

We estimate the flux of the GRB neutrino background and compute the event rate at SK and TITAND in the collapsar model, assuming that GRB formation rate is proportional to the star formation rate. We find that the flux and the event rate depend sensitively on the mass-accretion rate. Although the detection of signals from GRBs seems to be difficult by SK, we find that we can detect them by TITAND (optimistically about 20 events per year in the energy range where the energy of anti-electron neutrino is larger than 50 MeV). Therefore, we show that we will obtain the informations on the mass-accretion rate of collapsar by observing the GRB neutrino background, which, in turn, should give us informations on the total explosion energy of GRBs.

astro-ph↗

arXiv2001

Muon capture in hydrogen

Theoretical difficulties in reconciling the measured rates for ordinary and radiative muon capture are discussed, based on heavy-baryon chiral perturbation theory. We also examine ambiguity in our analysis due to the formation of p$μ$p molecules in the liquid hydrogen target.

nucl-th↗

arXiv2001

The $μ^-d$ capture rate in effective field theory

Muon capture on the deuteron is studied in heavy baryon chiral perturbation theory (HBChPT). It is found that by far the dominant contribution to $μd$ capture comes from a region of the final three-body phase-space in which the energy of the two neutrons is sufficiently small for HBChPT to be applicable. The single unknown low-energy constant having been fixed from the tritium beta decay rate, our calculation contains no free parameter. Our estimate of the $μd$ capture rate is consistent with the existing data. The relation between $μd$ capture and the $νd$ reactions, which are important for the SNO experiments, is briefly discussed.

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