119101312
Ordinary muon capture on a proton in manifestly Lorentz invariant baryon chiral perturbation theory
The amplitude for ordinary muon capture on the proton is evaluated, through the first four orders in the expansion parameter, in a manifestly Lorentz invariant form of baryon chiral perturbation theory. Expressions for the low energy constants in terms of physical quantities are obtained in each of the several renormalization schemes which have been proposed for forcing the relativistic approach to obey the same counting rules as obtained in heavy baryon chiral perturbation theory. The advantages and disadvantages of these schemes are discussed, using the muon capture results as an example, with the aim of gaining insight as to which scheme is preferable for practical calculations.
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.
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.
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.
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.
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.
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.
125701625
Gamma-ray burst neutrino background and star formation history in the universe
Abstract We estimate the flux of the GRB neutrino background and compute the event rate at SK and TITAND in the collapsar model, assuming that GRB formation rate is proportional to the star formation rate. We find that the predicted background neutrino flux is highly sensitive to unknown model parameters, mainly to the mass accretion rate, to the fraction of disk energy emitted in thermal neutrinos (as opposed to emission through electromagnetic processes), and to the fraction of collapsar events leading to GRBs. The predicted neutrino flux varies over many orders of magnitude as the values of unknown model parameters are varied. We investigate the detection possibility of thermal neutrinos from collapsars which lead to GRBs by TITAND. We find that the GRB neutrino background might be detected by TITAND within ∼ 10 yrs only for the optimistic cases in which the average mass-accretion rate is high (≥ a few M ⊙ s −1 ), and the probability that one collapsar generates a GRB is high ( φ = 0.5 − 1.0).
1356531
Nonlinear evolution of anisotropic cosmological power.
There has been growing interest in the possibility of testing more precisely the assumption of statistical isotropy of primordial density perturbations. If it is to be tested with galaxy surveys at distance scales < or = 10 Mpc, then nonlinear evolution of anisotropic power must be understood. To this end, we calculate the angular dependence of the power spectrum to third order in perturbation theory for a primordial power spectrum with a quadrupole dependence on the wave vector direction. Our results suggest that primordial power anisotropies will be suppressed by < or = 7% in the quasilinear regime. We also show that the skewness in the statistically anisotropic theory differs by no more than 1% from that in the isotropic theory.