125701625
Gamma-ray burst neutrino background and star formation history in the universe
Abstract 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 predicted background neutrino flux is highly sensitive to unknown model parameters, mainly to the mass accretion rate, to the fraction of disk energy emitted in thermal neutrinos (as opposed to emission through electromagnetic processes), and to the fraction of collapsar events leading to GRBs. The predicted neutrino flux varies over many orders of magnitude as the values of unknown model parameters are varied. We investigate the detection possibility of thermal neutrinos from collapsars which lead to GRBs by TITAND. We find that the GRB neutrino background might be detected by TITAND within ∼ 10 yrs only for the optimistic cases in which the average mass-accretion rate is high (≥ a few M ⊙ s −1 ), and the probability that one collapsar generates a GRB is high ( φ = 0.5 − 1.0).
43920467
Mapping dark matter in the gamma-ray sky with galaxy catalogs
Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI),Todai Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan(Dated: December 16, 2013)Cross-correlating gamma-ray maps with locations of galaxies in the low-redshift Universe vastlyincreases sensitivity to signatures of annihilation of dark matter particles. Low-redshift galaxiesare ideal targets, as the largest contribution to anisotropy in the gamma-ray sky from annihilationcomes from z . 0:1, where we expect minimal contributions from astrophysical sources such asblazars. Cross-correlating the ve-year data of Fermi-LAT with the redshift catalog of the 2MASSsurvey can detect gamma rays from annihilation if dark matter has the canonical annihilation crosssection and its mass is smaller than ˘100 GeV.
1356531
Nonlinear evolution of anisotropic cosmological power.
There has been growing interest in the possibility of testing more precisely the assumption of statistical isotropy of primordial density perturbations. If it is to be tested with galaxy surveys at distance scales < or = 10 Mpc, then nonlinear evolution of anisotropic power must be understood. To this end, we calculate the angular dependence of the power spectrum to third order in perturbation theory for a primordial power spectrum with a quadrupole dependence on the wave vector direction. Our results suggest that primordial power anisotropies will be suppressed by < or = 7% in the quasilinear regime. We also show that the skewness in the statistically anisotropic theory differs by no more than 1% from that in the isotropic theory.
116431772
Supernova Neutrino Oscillations and the Neutrino Magnetic Moment
Resonant spin-flavour (RSF) conversions of supernova neutrinos, which are induced by the interaction between the nonzero neutrino magnetic moment and supernova magnetic fields, are studied for both normal and inverted mass hierarchy. As the case for the pure matter-induced neutrino oscillation (Mikheyev–Smirnov–Wolfenstein (MSW) effect), we find that the RSF transitions are strongly dependent on the neutrino mass hierarchy as well as the value of θ13. Flavour conversions are solved numerically for various neutrino parameter sets, with the realistic presupernova profile. In particular, it is very interesting that the RSF-induced νe → ν̄e transition occurs if the following conditions are all satisfied: the value of μνB (μν is the neutrino magnetic moment and B is the magnetic field strength) is sufficiently strong, the neutrino mass hierarchy is inverted, and the value of θ13 is large enough to induce adiabatic MSW resonance. In this case, the strong peak due to the original νe emitted from the neutronization burst would exist in the time profile of the neutrino events detected at the Super-Kamiokande detector. If this peak were observed in reality, it would provide fruitful information on the neutrino properties. On the other hand, the characteristics of the neutrino spectra are also different between the neutrino models, but we find that there remains degeneracy among several models. This contribution is based on our recent study [1].
124377961
A neutrino burst and gravitational wave from supernova explosions
43135563
High-energy neutrinos from reverse shocks in choked and successful relativistic jets
Highly relativistic jets are a key element of current gamma-ray burst models, where the jet kinetic energy is converted to radiation energy at optically thin shocks. High-energy neutrinos are also expected, from interactions of protons accelerated in the same shocks. Here we revisit the early evolution of a relativistic jet, while the jet is still inside the star, and investigate its neutrino emission. In particular we study propagation of mildly relativistic and ultrarelativistic jets through a type Ib progenitor, and follow reverse shocks as the jets cross the star. We show that protons can be accelerated to 10^4–10^5 GeV at reverse shocks, and efficiently produce mesons. The mesons experience significant cooling, suppressing subsequent neutrino emission. We show, however, that the neutrino yield from the reverse shock is still reasonably large, especially for low-luminosity and long-duration jets, where meson cooling is less severe. We discuss implications of our results in the context of neutrinos from choked jets, which are completely shock heated and do not break out of the star. From a choked jet with isotropic equivalent energy of 10^53 erg at 10 Mpc, we expect ~20 neutrino events at IceCube.
197438832
Radiative neutron capture on a proton at BBN energies
The total cross section for radiative neutron capture on a proton, $np \to d \gamma$, is evaluated at big bang nucleosynthesis (BBN) energies. The electromagnetic transition amplitudes are calculated up to next-to leading order within the framework of pionless effective field theory with dibaryon fields. We also calculate the $d\gamma\to np$ cross section and the photon analyzing power for the $d\vec{\gamma}\to np$ process from the amplitudes. The values of low energy constants that appear in the amplitudes are estimated by a Markov Chain Monte Carlo analysis using the relevant low energy experimental data. Our result agrees well with those of other theoretical calculations except for the $np\to d\gamma$ cross section at some energies estimated by an R-matrix analysis. We also study the uncertainties in our estimation of the $np\to d\gamma$ cross section at relevant BBN energies and find that the estimated cross section is reliable to within $\sim$1% error.
14101191
The μ - d capture rate in effective field theory
Muon capture on the deuteron is studied in a framework that essentially incorporates heavy baryon chiral perturbation theory (HBχ PT). It is found that by far the dominant contribution to µd capture comes from a region of the final three-body phasespace in which the energy of the two neutrons is sufficiently small for HB χ PT 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.  2002 Elsevier Science B.V. All rights reserved.
118449544
Spin Observables in the Two-Nucleon Capture and Dissociation Processes at Low Energies
Spin observables in radiative neutron capture on a proton and its inverse process, photodisintegration of the deuteron are calculated using a pionless effective field theory with di-baryon fields. Good agreement with the results of existing standard nuclear physics approach (SNPA) is obtained at very low energies. As energy increases, however, the discrepancy between the effective field theory and the SNPA becomes substantial. We discuss the origin of the difference.
639846
Neutrino-deuteron reactions at solar neutrino energies
Abstract In interpreting the SNO experiments, 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 (∼1%) larger than the previously reported values. It is shown to be reasonable to assign 1% uncertainty to the νd cross sections reported here; this error estimate does not include radiative corrections, for which we refer to the literature.
118906717
Leading chiral corrections to the nucleon generalized parton distributions
Using heavy baryon chiral perturbation theory we study the leading chiral corrections to the complete set of nucleon generalized parton distributions (GPDs). We compute the leading quark mass and momentum transfer dependence of the moments of nucleon GPDs through the nucleon off-forward twist-2 matrix elements. These results are then applied to get insight on the GPDs and their impact parameter space distributions.