119557577
Renormalization-group analysis for low-energy scattering of charged particles
We outline our renormalization-group analysis for low-energy scattering two charged particles. This uses dimensional regularization and extends previous analyses by including both momentum- and energy-dependent perturbations.
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.
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.
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.
6857347
The Gamma-Ray-Flux Probability Distribution Function from Galactic Halo Substructure
One of the targets of the recently launched Fermi Gamma-ray Space Telescope is a diffuse gamma-ray background from dark-matter annihilation or decay in the Galactic halo. N-body simulations and theoretical arguments suggest that the dark matter in the Galactic halo may be clumped into substructure, rather than smoothly distributed. Here we propose the gamma-ray-flux probability distribution function (PDF) as a probe of substructure in the Galactic halo. We calculate this PDF for a phenomenological model of halo substructure and determine the regions of the substructure parameter space in which the PDF may be distinguished from the PDF for a smooth distribution of dark matter. In principle, the PDF allows a statistical detection of substructure, even if individual halos cannot be detected. It may also allow detection of substructure on the smallest microhalo mass scales, ∼M⊕, for weakly-interacting massive particles (WIMPs). Furthermore, it may also provide a method to measure the substructure mass function. However, an analysis that assumes a typical halo substructure model and a conservative estimate of the diffuse background suggests that the substructure PDF may not be detectable in the lifespan of Fermi in the specific case that the WIMP is a neutralino. Nevertheless, for a large range of substructure, WIMP annihilation, and diffuse background models, PDF analysis may provide a clear signature of substructure. PACS numbers: 95.85.Pw, 95.35.+d, 98.35.Gi The Gamma-Ray-Flux PDF from Galactic Halo Substructure 2
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.
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.
67832038
Colloquium: Multimessenger astronomy with gravitationalwaves and high-energy neutrinos
Many of the astrophysical sources and violent phenomena observed in our Universe are potential 
emitters of gravitational waves and high-energy cosmic radiation, including photons, hadrons, and 
presumably also neutrinos. Both gravitational waves (GW) and high-energy neutrinos (HEN) are 
cosmic messengers that may escape much denser media than photons. They travel unaffected over 
cosmological distances, carrying information from the inner regions of the astrophysical engines from 
which they are emitted (and from which photons and charged cosmic rays cannot reach us). For the same 
reasons, such messengers could also reveal new, hidden sources that have not been observed by 
conventional photon-based astronomy. Coincident observation of GWs and HENs may thus play a 
critical role in multimessenger astronomy. This is particularly true at the present time owing to the 
advent of a new generation of dedicated detectors: the neutrino telescopes IceCube at the South Pole and 
ANTARES in the Mediterranean Sea, as well as the GW interferometers Virgo in Italy and LIGO in the 
United States. Starting from 2007, several periods of concomitant data taking involving these detectors 
have been conducted. More joint data sets are expected with the next generation of advanced detectors 
that are to be operational by 2015, with other detectors, such as KAGRA in Japan, joining in the future. 
Combining information from these independent detectors can provide origin always of constraining the 
physical processes driving the sources and also help confirm the astrophysical origin of a GW or HEN 
signal in case of coincident observation. Given the complexity of the instruments, a successful joint 
analysis of this combined GW and HEN observational data set will be possible only if the expertise and 
knowledge of the data is shared between the two communities. This Colloquium aims at providing an 
overview of both theoretical and experimental state of the art and perspectives for GW and HEN 
multimessenger astronomy.
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.