131394
Gamma-ray probe of cosmic ray pressure in galaxy clusters and cosmological implications
Cosmic rays produced in cluster accretion and merger shocks provide pressure to the intracluster medium (ICM) and affect the mass estimates of galaxy clusters. Although direct evidence for cosmic ray ions in the ICM is still lacking, they produce γ -ray emission through the decay 
of neutral pions produced in their collisions with ICM nucleons. We investigate the capability of the Gamma-ray Large Area Space Telescope (GLAST) and imaging atmospheric Cerenkov telescopes (IACTs) for constraining the cosmic ray pressure contribution to the ICM. We show that GLAST can be used to place stringent upper limits, a few per cent for individual nearby rich clusters, on the ratio of pressures of the cosmic rays and thermal gas. We further show that 
it is possible to place tight (≤ 
10 per cent) constraints for distant (z ≤ 
0.25) clusters in the case of hard spectrum, by stacking signals from samples of known clusters. The GLAST limits could be made more precise with the constraint on the cosmic ray spectrum potentially provided by IACTs. Future γ-ray observations of clusters can constrain the evolution of cosmic ray energy density, which would have important implications for cosmological tests with upcoming X-ray and Sunyaev–Zel’dovich effect cluster surveys.
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.
216052179
Constraints on the annihilation cross section of dark matter particles from anisotropies in the diffuse gamma-ray background measured with Fermi-LAT
Annihilation of dark matter particles in cosmological halos (including the halo of the Milky Way) contributes to the diffuse gamma-ray background (DGRB). As this contribution will appear anisotropic in the sky, one can use the angular power spectrum of anisotropies in the DGRB to constrain the properties of dark matter particles. By comparing the updated analytic model of the angular power spectrum of the DGRB from dark matter annihilation with the power spectrum recently measured from the 22-month data of the Fermi Large Area Telescope (LAT), we place upper limits on the annihilation cross section of dark matter particles as a function of dark matter masses. We find that the current data exclude (σv)≳10−25  cm3 s−1 for annihilation into bb¯ at the dark matter mass of 10 GeV, which is a factor of 3 times larger than the canonical cross section. The limits are weaker for larger dark matter masses. The limits can be improved further with more Fermi-LAT data as well as by using the power spectrum at lower multipoles (l≲150), which are currently not used due to a potential Galactic foreground contamination.
124377961
A neutrino burst and gravitational wave from supernova explosions
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).
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].
15737183
Analysis of ordinary and radiative muon capture in liquid hydrogen
The experimental data on the ordinary muon capture (OMC) rate and the partial branching ratio of radiative muon capture (RMC) in liquid hydrogen are simultaneously analyzed using theoretical estimates for the atomic OMC rates obtained in chiral perturbation theory using the most recent physical constants. Since both data have been obtained in a liquid hydrogen target, we reexamine the formulas for relating the atomic OMC and RMC rates to the liquid hydrogen OMC and RMC rates, respectively. Although the analysis is influenced significantly by the ambiguity in the molecular state population, we can conclude that, while the OMC data can be reproduced, it is not possible to explain the OMC and RMC data simultaneously.
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.
119101312
Ordinary muon capture on a proton in manifestly Lorentz invariant baryon chiral perturbation theory
The amplitude for ordinary muon capture on the proton is evaluated, through the first four orders in the expansion parameter, in a manifestly Lorentz invariant form of baryon chiral perturbation theory. Expressions for the low energy constants in terms of physical quantities are obtained in each of the several renormalization schemes which have been proposed for forcing the relativistic approach to obey the same counting rules as obtained in heavy baryon chiral perturbation theory. The advantages and disadvantages of these schemes are discussed, using the muon capture results as an example, with the aim of gaining insight as to which scheme is preferable for practical calculations.
119557577
Renormalization-group analysis for low-energy scattering of charged particles
We outline our renormalization-group analysis for low-energy scattering two charged particles. This uses dimensional regularization and extends previous analyses by including both momentum- and energy-dependent perturbations.
119189801
Parity-violating polarization in np->dgamma with a pionless effective field theory
We consider the two-nucleon weak interaction with a pionless effective field theory. Dibaryon fields are introduced to ensure fast convergence of the perturbative expansion. Weak interactions are accounted for with the parity-violating dibaryon-nucleon-nucleon vertices, which contain unknown weak coupling constants. We apply the model to the calculation of a parity-violating observable in the radiative neutron capture on a proton at threshold. Result is obtained up to the linear order of the weak dibaryon-nucleon-nucleon coupling constants. We compare our result to the ones obtained from other approaches, and discuss investigation of the weak interaction in few-body systems.