15824677
Electroweak processes of the deuteron in effective field theory
We review our recent calculations of electroweak processes involving the deuteron, based on pionless effective field theory with dibaryon fields. These calculations are concerned with neutron-neutron fusion and np -> d gamma at BBN energies.
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.
122375456
Renormalization group analysis of nuclear current operators
A Wilsonian renormalization group (WRG) equation for nuclear current operators in two-nucleon systems is derived. Nuclear current operators relevant to low-energy Gamow-Teller transitions are analyzed using the WRG equation. We employ the axial two-body current operators from phenomenological models and heavy-baryon chiral perturbation theory, which are quite different from one another in describing small-scale physics. After reducing the model space of the operators using the WRG equation, we find that there still remains a significant model dependence at {lambda}=200 MeV, where {lambda} is the sharp cutoff specifying the size of the model space. A model-independent effective current operator is found at a rather small cutoff value, {lambda}=70 MeV. By simulating the effective current operator at {lambda}=70 MeV, we obtain a current operator based on a pionless theory, thereby arguing that an equivalence relation exists between nuclear current operators of phenomenological models and those of effective field theories.
118594879
Renormalization-group analysis for low-energy scattering of charged particles
The low-energy scattering of two charged particles is analyzed using a renormalization group approach based on dimensional regularization with power-divergence subtraction. A nontrivial solution with a marginally unstable direction is found, corresponding to a system with a bound state at zero energy. For purely energy-dependent perturbations around this solution, the power counting agrees with that from Wilsonian methods. These terms in the effective potential are in direct correspondence with the the terms in the Coulomb-distorted effective-range expansion. We also study perturbations that depend on off-shell momenta as well as energy, and we show that these affect only the off-shell form of the scattering matrix. These terms are of higher order than the corresponding energy-dependent ones and so terms in the potential that depend only on the off-shell momenta do not have definite orders in power counting.
14652153
Neutron–neutron fusion
Abstract The neutron–neutron fusion process, n n → d e ν , at very low neutron energies is studied in the framework of pionless effective field theory that incorporates dibaryon fields. The cross section and electron energy spectrum for this process are calculated up to next-to-leading order. We include the radiative corrections of O ( α ) calculated for the one-body transition amplitude. The precision of our theoretical estimates is found to be governed essentially by the accuracy with which the empirical values of the neutron–neutron scattering length and effective range are currently known. Also discussed is the precision of theoretical estimates of the transition rates of related electroweak processes in few-nucleon systems.
55936228
Effective field theory of 3He
We examine the effects of the long range Coulomb force on the three-body contact interaction in a pionless effective theory of 3He. The corresponding interaction in 3H exhibits limit-cycle behavior and we show that this is not altered by the 1/r singularity of the potential.
15332448
Relic neutrino background from cosmological supernovae
Present and future observations of supernova relic neutrinos (SRNs), i.e., a cosmological neutrino background from past core-collapse supernova explosions, potentially give us useful information concerning various fields of astrophysics, cosmology and particle physics. We review recent progress of theoretical and observational studies of SRNs, particularly focusing on the detectability, and also on implications for cosmic star formation history and neutrino physics.
118958027
Three generation study of neutrino spin flavor conversion in supernova and implication for neutrino magnetic moment
We investigate resonant spin-flavor (RSF) conversions of supernova neutrinos which are induced by the interaction of neutrino magnetic moment and supernova magnetic fields. From the formulation which includes all three-flavor neutrinos and antineutrinos, we give a new crossing diagram that includes not only ordinary Mikheyev-Smirnov-Wolfenstein (MSW) resonance but also a magnetically induced RSF effect. With the diagram, it is found that four conversions occur in supernovae: two are induced by the RSF effect and two by the pure MSW effect. We also numerically calculate neutrino conversions in supernova matter, using neutrino mixing parameters inferred from recent experimental results and a realistic supernova progenitor model. The results indicate that until 0.5 sec after the core bounce, the RSF-induced ${\overline{\ensuremath{\nu}}}_{e}\ensuremath{\leftrightarrow}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ transition occurs efficiently (adiabatic resonance), when ${\ensuremath{\mu}}_{\ensuremath{\nu}}\ensuremath{\gtrsim}{10}^{\ensuremath{-}12}{\ensuremath{\mu}}_{B}{(B}_{0}/5\ifmmode\times\else\texttimes\fi{}{10}^{9}\mathrm{G}{)}^{\ensuremath{-}1},$ where ${B}_{0}$ is the strength of the magnetic field at the surface of iron core. We also evaluate the energy spectrum as a function of ${\ensuremath{\mu}}_{\ensuremath{\nu}}{B}_{0}$ at the super-Kamiokande detector and the Sudbury Neutrino Observatory using the calculated conversion probabilities, and find that the spectral deformation might have the possibility to provide useful information on the neutrino magnetic moment as well as the magnetic field strength in supernovae.
19252350
Neutrino oscillations, Lorentz/CPT violation, and dark energy
If dark energy (DE) couples to neutrinos, then there may be apparent violations of Lorentz/CPT invariance in neutrino oscillations. The DE-induced Lorentz/CPT violation takes a specific form that introduces neutrino oscillations that are energy independent, differ for particles and antiparticles, and can lead to novel effects for neutrinos propagating through matter. We show that ultra-high-energy neutrinos may provide one avenue to seek this type of Lorentz/CPT violation in ν_μ-ν_τ oscillations, improving the current sensitivity to such effects by 7 orders of magnitude. Lorentz/CPT violation in electron-neutrino oscillations may be probed with the zenith-angle dependence for high-energy atmospheric neutrinos. More compelling evidence for a DE-neutrino coupling would be provided by a dependence of neutrino oscillations on the direction of the neutrino momentum relative to our peculiar velocity with respect to the cosmic microwave background rest frame. While the amplitude of this directional dependence is expected to be small, it may nevertheless be worth seeking in current data and may be a target for future neutrino experiments.
10058011
Angular power spectrum of gamma-ray sources for GLAST: blazars and clusters of galaxies
Blazars, a beamed population of active galactic nuclei, radiate high-energy γ-rays, and thus are a good target for the Gamma Ray Large Area Space Telescope (GLAST). As the blazars trace the large-scale structure of the Universe, one may observe spatial clustering of blazars. We calculate the angular power spectrum of blazars that would be detected by GLAST. We show that we have the best chance of detecting their clustering at large angular scales, θ ≳ 10°, where shot noise is less important, and the dominant contribution to the correlation comes from relatively low redshift, z ≲ 0.1. The GLAST can detect the correlation signal, if the blazars detected by GLAST trace the distribution of low-z quasars observed by optical galaxy surveys, which have the bias of unity. If the bias of blazars is greater than 1.5, GLAST will detect the correlation signal unambiguously. We also find that GLAST may detect spatial clustering of clusters of galaxies in γ-rays. The shape of the angular power spectrum is different for blazars and clusters of galaxies; thus, we can separate these two contributions on the basis of the shape of the power spectrum.
119046200
Dark matter annihilation from intermediate-mass black holes: Contribution to the extragalactic gamma-ray background
We investigate contributions to the extragalactic gamma-ray background (EGB) due to neutralino dark matter (DM) pair-annihilation into photons, from DM density enhancements (minispikes) surrounding intermediate-mass black holes (IMBHs). We focus on two IMBH formation scenarios; our conservative scenario where IMBHs are remnants of Population-III stars, and our optimistic scenario where IMBHs are formed in protogalactic disks. In both scenarios, their formation in pregalactic halos at high redshift lead to the formation of minispikes that are bright sources of gamma-ray photons. Taking into account minispike depletion processes, we only sum contributions from a cosmological distribution of IMBHs with maintained minispikes. Our conservative scenario (BH mass 10^2M[sun] with a r^-3/2 minispike) predicts gamma-ray fluxes that are an order larger than the equivalent flux, using the same DM parameters (mass 100 GeV and annihilation cross section 3×10^-26 cm^3 s^-1), from the host halo without IMBH minispikes. Our optimistic scenario (BH mass 105^M[sun] with a r^-7/3 minispike) predicts fluxes that are three orders larger, that can reach current EGB observations taken by EGRET (DM parameters as above). This fact may serve interesting consequences for constraining DM parameters and elucidating the true nature of IMBHs. Additionally, we determine the spectra of DM annihilation into monochromatic gamma rays, and show that its flux can be within observational range of GLAST, providing a potential "smoking-gun" signature of DM.