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.
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.
16520608
Parity-violating nucleon-nucleon interaction from different approaches
Two-pion exchange parity-violating nucleon-nucleon interactions from recent effective field theories and earlier fully covariant approaches are investigated. The potentials are compared with the goal of obtaining better insight into the role of low-energy constants appearing in the effective field theory approach and its convergence in terms of a perturbative series. The results are illustrated by considering the longitudinal asymmetry of polarized protons scattering off protons, p-vector+p{yields}p+p, and the asymmetry of the photon emission in radiative capture of polarized neutrons by protons, n-vector+p{yields}d+{gamma}.
18094401
Solar-neutrino reactions on deuteron in effective field theory
Abstract The cross sections for low-energy neutrino–deuteron reactions are calculated within heavy-baryon chiral perturbation theory employing a cut-off regularization scheme. The transition operators are derived up to next-to-next-to-next-to-leading order in the Weinberg counting rules, while the nuclear matrix elements are evaluated using the wave functions generated by a high-quality phenomenological NN potential. With the adoption of the axial-current-four-nucleon coupling constant fixed from the tritium beta decay data, our calculation is free from unknown low-energy constants. Our results exhibit a high degree of stability against different choices of the cutoff parameter, a feature which indicates that, apart from radiative corrections, the uncertainties in the calculated cross sections are less than 1%.
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.
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.
15665946
Cosmic Star Formation History and the Future Observation of Supernova Relic Neutrinos
We investigate the flux and event rate of supernova relic neutrinos (SRNs) and discuss their implications for the cosmic star formation rate. Since SRNs are diffuse neutrino background emitted from past core-collapse supernova explosions, they contain fruitful information on the supernova rate in the past and present universe, as well as on the supernova neutrino spectrum itself. As reference models, we adopt the supernova rate model based on recent observations and the supernova neutrino spectrum numerically calculated by several groups. In the detection energy range Ee > 10 MeV, which will possibly be a background-free region in the near future, the SRN event rate is found to be 1-2 yr-1 at a water Cerenkov detector with a fiducial volume of 22.5 kton, depending on the adopted neutrino spectrum. We also simulate the expected signal with one set of the reference models by using the Monte Carlo method and then analyze these pseudodata with several free parameters, obtaining the distribution of the best-fit values for them. In particular, we use a parameterization such that RSN(z) = R(1 + z)α, where RSN(z) is the comoving supernova rate density at redshift z and R and α are free parameters, assuming that the supernova neutrino spectrum and luminosity are well understood by way of a future Galactic supernova neutrino burst or the future development of numerical supernova simulations. The obtained 1 σ errors for these two parameters are found to be δα/α = 30% (7.8%) and δR/R = 28% (7.7%) for a detector with an effective volume of 22.5 kton × 5 yr (440 kton × 5 yr), where one of the parameters is fixed. On the other hand, if we fix neither of the values for these two parameters, the expected errors become rather large, δα/α = 37% and δR/R = 55%, even with an effective volume of 440 kton × 5 yr.
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.
73520402
Resonant Spin-Flavor Conversion of Supernova Neutrinos
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 anti-neutrinos, we give a new crossing diagram that includes not only ordinary MSW resonance but also magnetically-induced RSF effect. With the diagram, it is found that four conversions occur in supernova, two are induced by the RSF effect and two by the pure MSW. 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 seconds after core bounce, the RSF-induced νe ↔ ντ transition occurs efficiently (adiabatic resonance), when μν ∼ 10−12μB(B0/5 × 109G)−1, where B0 is the strength of the magnetic field at the surface of iron core. We also evaluate the energy spectrum as a function of μνB0 at the SuperKamiokande detector and the Sudbury Neutrino Observatory using the calculated conversion probabilities, and find that the spectral deformation might have possibility to provide useful information on neutrino magnetic moment as well as magnetic field strength in supernovae.1 1 Reference: S. Ando and K. Sato, Phys. Rev. D 67, 023004 (2003).
53419787
Inverse-Compton emission from clusters of galaxies: Predictions for ASTRO-H ?
The intra-cluster medium of several galaxy clusters hosts large-scale regions of diffuse synchrotron radio emission, known as radio halos and relics, which demonstrates the presence of magnetic fields and relativistic electrons in clusters. These relativistic electrons should also emit X-rays through inverse-Compton scattering off of cosmic microwave background photons. The detection of such a non-thermal X-ray component, together with the radio measurement, would permit the magnetic field to be clearly separated from the relativistic electron distribution because the inverse-Compton emission is independent of the magnetic field in the cluster. However, non-thermal X-rays have not been conclusively detected from any cluster of galaxies so far. In this paper, for the first time, we model the synchrotron and inverse-Compton emission of all clusters hosting radio halos and relics for which the spectral index can be determined. We provide constraints on the volume-average magnetic field by comparing with current X-ray measurements. We then estimate the maximum volume-average magnetic field that will allow detection of inverse-Compton hard X-rays by the ASTRO-H satellite. We find that several clusters are good targets for ASTRO-H to detect their inverse-Compton emission, in particular for what corresponds to radio relics, so we propose a list of promising targets for which ASTRO-H can test ≥ 1μG magnetic fields. We conclude that the already operating NuSTAR and the soon-to-be-launched ASTRO-H definitely have the potential of shedding light on the long-sought non-thermal hard-X-ray emission in clusters of galaxies.
121074021
Detectability of the supernova relic neutrinos
Abstract We investigate the flux and the event rate of the supernova relic neutrino background (SRN) at the Super-Kamiokande (SK) detector for various neutrino oscillation models with parameters inferred from recent experimental results. A realistic model of neutrino emission from supernova explosions are adopted in the calculation. The number flux over entire energy range is found to be ∼ 11 cm−2 s−1. We discuss the detectability of SRN at SK, 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 MeV the expected event rate at SK 0.4–0.7 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.