14698676
THE OLD AND THE NEW OF PARITY-VIOLATING TWO-PION-EXCHANGE NN POTENTIAL
We consider the parity-violating two-pion-exchange potential obtained from the covari-ant formalism in the past and the state-of-the-art effective field theory approach. We discuss the behavior of the potential in coordinate space and its application to the parity-violating asymmetry in at threshold.
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.
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.
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.
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.
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.
43920467
Mapping dark matter in the gamma-ray sky with galaxy catalogs
Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI),Todai Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan(Dated: December 16, 2013)Cross-correlating gamma-ray maps with locations of galaxies in the low-redshift Universe vastlyincreases sensitivity to signatures of annihilation of dark matter particles. Low-redshift galaxiesare ideal targets, as the largest contribution to anisotropy in the gamma-ray sky from annihilationcomes from z . 0:1, where we expect minimal contributions from astrophysical sources such asblazars. Cross-correlating the ve-year data of Fermi-LAT with the redshift catalog of the 2MASSsurvey can detect gamma rays from annihilation if dark matter has the canonical annihilation crosssection and its mass is smaller than ˘100 GeV.
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.
37593507
JOINT SEARCHES BETWEEN GRAVITATIONAL-WAVE INTERFEROMETERS AND HIGH-ENERGY NEUTRINO TELESCOPES: SCIENCE REACH AND ANALYSIS STRATEGIES
Many of the astrophysical sources and violent phenomena observed in our Universe are potential emitters of gravitational waves (GWs) and high-energy neutrinos (HENs). A network of GW detectors such as LIGO and Virgo can determine the direction/time of GW bursts while the IceCube and ANTARES neutrino telescopes can also provide accurate directional information for HEN events. Requiring the consistency between both, totally independent, detection channels shall enable new searches for cosmic events arriving from potential common sources, of which many extra-galactic objects.