1475604
Low energy proton-proton scattering in effective field theory
Low energy proton-proton scattering is studied in pionless effective field theory. Employing the dimensional regularization and MS and power divergence subtraction schemes for loop calculation, we calculate the scattering amplitude in the {sup 1}S{sub 0} channel up to the next-to-next-to leading order and fix low-energy constants that appear in the amplitude by effective range parameters. We study the regularization scheme and scale dependence in the separation of the Coulomb interaction from the scattering length and effective range for the S-wave proton-proton scattering.
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.
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.
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.
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.
119042532
Appearance of neutronization peak and decaying supernova neutrinos
Nonradiative neutrino decay, which is not satisfactorily constrained, possibly and significantly changes the detected neutrino signal from galactic supernova explosions. We focus on the appearance of a sharp peak due to a neutronization burst in the time profile; this phenomenon would occur if the original \nu_e, produced at the neutrinosphere and becoming \nu_{2,3} at the stellar surface, decays into a lighter antineutrino state such as \bar\nu_{1,2} coupled to \bar\nu_e. This is due to the fact that the signature of the neutronization burst is common to all numerical simulations. Therefore, the appearance of a neutronization peak in the \bar\nu_e signal, if it were detected, would clearly indicate the nonstandard properties of neutrinos. Using a newly developed formulation that includes flavor conversions inside the supernova envelope and neutrino decay during propagation in a vacuum, we calculate the expected neutrino signal at the detectors; the lifetimes of three modes \tau_{12}, \tau_{13}, and \tau_{23} are taken to be free parameters. We further introduce simple quantities, which represent a peak sharpness of time profile and spectral hardness, and investigate the parameter dependence of these quantities. As the result, it is found that they are quite dependent on the relevant parameters, but it would be quite difficult to distinguish models using the signal obtained by the Super-Kamiokande detector; the future megaton-class detectors would have sufficient sensitivity. We also compare the neutrino decay model with another mechanism, i.e., resonant spin-flavor conversion, which also may give the appearance of a neutronization peak, and conclude that these two independent mechanisms give a different signal and one can be distinguished from the other.
122096776
Multimessenger Astronomy and Neutrinos
Abstract Neutrinos play a very important role in multimessenger astronomy. In this talk, I start with a simple argument on how bright the Universe is in both photons and neutrinos. It is remarkable that one can easily show that the neutrinos, especially those emitted from past core-collapse supernovae, form the brightest radiation component in the Universe, ever emitted from astrophysical sources. The detection of this cosmic supernova neutrino background has not been made yet, but is almost guaranteed in the near future. Thus, I review theoretical predictions of the supernova neutrino background, and the latest upper limits experimentally obtained on its flux. Then I discuss prospects of detecting supernova neutrinos from nearby galaxies. With upcoming Mton detectors, or hopefully with a multi-Mton detector, one could study not only supernova neutrinos but also a true stellar death rate, hidden black-hole formation, etc. Finally, I discuss detectability of high-energy neutrinos and implications for underlying supernova–gamma-ray burst connection. Detecting neutrinos will not only give unique diagnostics but also help find gravitational waves.
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.
30020784
Probing dark gamma‐ray bursts with neutrinos
Highly relativistic jets are a key element of current gamma‐ray burst (GRB) models, where the jet kinetic energy is converted to radiation energy at optically thin shocks. Mildly relativistic jets with smaller Lorentz factors are typically optically thick to gamma rays, and do not produce the spectacular GRB phenomenon. Jets which stall inside the progenitor similarly do not produce a GRB. However, various studies suggest that these jets are more common than GRB‐producing jets. Here we report on our study of high‐energy neutrino emission from these hidden jets. We describe the detection prospects with near‐future neutrino detectors, and discuss how the presence of jets can be studied with neutrinos. The neutrino horizon for hidden jets is of order 10 Mpc, a volume which contains at least a few supernova per year.
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).