3104882
Can proper motions of dark-matter subhalos be detected?
One of the goals of NASA's Fermi Gamma-ray Space Telescope (formerly GLAST) will be the detection of gamma rays from dark-matter annihilation in the Galactic halo. Theoretical arguments suggest that dark matter may be bound into subhalos with masses as small as 10^-4–10^2M⊕. If so, it may be possible to detect individual subhalos as point sources in the Fermi Telescope. It has further been argued that some of these point sources may exhibit proper motions. Here we show that upper limits to the diffuse gamma-ray background constrain the number of subhalos close enough to exhibit proper motions to be less than one.
119067583
Supernova Relic Neutrinos and Observational Implications for Neutrino Oscillation
We investigate the flux and the event rate of supernova relic neutrinos (SRN) at the Super-Kamiokande (SK) detector for various neutrino oscillation models with parameters inferred from recent experimental results. We discuss the detectability of SRN at SK, comparing this SRN flux with other background neutrinos in more detail than previous studies, and it is found that in the energy range 17–25 MeV, ten-year observation might enable us to detect SRN signal (at one sigma level). We also set 90% C.L. upper limit on the SRN flux for various oscillation models using the recently released observational result by SK. In addition, we propose that the SRN observation can be used to set strong constraints on the neutrino decay models. Because of the long distance scale from cosmological supernovae to the Earth, SRN have possibility to provide much stronger limit than the present one obtained from solar neutrino observation. In the near future, further reduced upper limit is actually expected, when the current SK data are reanalyzed using some technique to reduce background events against the SRN signals. It is expected that the reduced upper limit is sufficient to provide useful implications for neutrino oscillation and decaying neutrinos.
124377961
A neutrino burst and gravitational wave from supernova explosions
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.
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).
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.
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.
17697036
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$\mu$p molecules in the liquid hydrogen target.
14614656
Radiative muon capture in heavy baryon chiral perturbation theory
Abstract The radiative muon capture (RMC) on a proton is analyzed by means of heavy baryon chiral perturbation theory. The emitted photon energy spectrum is calculated and compared with the experimental data by taking the spin sum on the muonic atom states. We find that one-loop order corrections to the tree order amplitude modify the photon spectrum by less than five percent. This calculation supports that the theory is under a quantitative control as far as the chiral perturbation expansion is concerned and indicates that the discrepancy between the pseudo-scalar coupling constant required by the RMC experiment and the one deduced from ordinary muon capture, the value of which is also supported by chiral perturbation calculations, will remain unexplained from the theoretical side.
123111129
Muon Capture in CHPT
14013541
Effective field theory of the deuteron with dibaryon fields
Pionless effective field theory with dibaryon fields is reexamined for observables involving the deuteron. The electromagnetic form factors of the deuteron and the total cross section of radiative neutron capture on the proton, np{yields}d{gamma}, are calculated. The low-energy constants of vector-(photon-)dibaryon-dibaryon vertices in the effective Lagrangian are fixed primarily by the one-body vector-(photon-)nucleon-nucleon interactions. This scheme for fixing the values of the low-energy constants satisfactorily reproduces the results of the effective range theory. We also show that, by including higher-order corrections, we can obtain results that are close to those of the Argonne v18 potential model.