15653982
A paradox on quantum field theory of neutrino mixing and oscillations
Neutrino mixing and oscillations in quantum field theory framework had been studied before, which shew that the Fock space of flavor states is unitarily inequivalent to that of mass states (inequivalent vacua model). A paradox emerges when we use these neutrino weak states to calculate the amplitude of W boson decay. The branching ratio of W+→e++νμ to W+→e++νe is approximately at the order of O(mi2/k2). This existence of flavor changing currents contradicts to the Hamiltonian we started from, and the usual knowledge about weak processes. Also, negative energy neutrinos (or violating the principle of energy conservation) appear in this framework. We discuss possible reasons for the appearance of this paradox.
118606894
Possible capture of keV sterile neutrino dark matter on radioactive beta-decaying nuclei
There exists an observed "desert" spanning six orders of magnitude between O(0.5) eV and O(0.5) MeV in the fermion mass spectrum. We argue that it might accommodate one or more keV sterile neutrinos as a natural candidate for warm dark matter. To illustrate this point of view, we simply assume that there is one key sterile neutrino nu(4) and its flavor eigenstate nu(s) weakly mixes with three active neutrinos. We clarify different active-sterile neutrino mixing factors for the radiative decay of nu(4) and beta decays in a self-consistent parametrization. A direct detection of this keV sterile neutrino dark matter in the laboratory is in principle possible since the nu(4) component of nu(e) can leave a distinct imprint on the electron energy spectrum when it is captured on radioactive beta-decaying nuclei. We carry out an analysis of its signatures in the capture reactions nu(e) + H-3 -> He-3 + e(-) and nu(e) + Ru-106 -> Rh-106 + e(-) against the beta-decay backgrounds, and conclude that this experimental approach might not be hopeless in the long run. (C) 2010 Elsevier B.V. All rights reserved.
118641290
Direct detection of the cosmic neutrino background including light sterile neutrinos
Current cosmological data drop an interesting hint about the existence of sub-eV sterile neutrinos, which should be a part of the cosmic neutrino background (C nu B). We point out that such light sterile neutrinos may leave a distinct imprint on the electron energy spectrum in the capture of relic electron neutrinos by means of radioactive beta-decaying nuclei. We examine possible signals of sterile neutrinos relative to active neutrinos, characterized by their masses and sensitive to their number densities, in the reaction nu(e) + (3)H -> (3)He + e(-) against the corresponding tritium beta decay. We stress that this kind of direct laboratory detection of the C nu B and its sterile component might not be hopeless in the long term. (C) 2010 Elsevier B.V. All rights reserved.
122049951
MCMC SAMPLING IN THE GLOBAL ANALYSIS OF SOLAR AND REACTOR NEUTRINO DATA
We present a global analysis of latest solar and reactor neutrino data in the three-neutrino mixing scheme by using both the simple grid scanning and the Markov Chain Monte Carlo (MCMC) sampling methods. Accuracy and efficiency of the two sampling methods are compared and advantages of the latter are discussed. The fitting results of three oscillation parameters theta(12), theta(13) and Delta m(21)(2) are provided with both old and new evaluations of the reactor antineutrino flux. Possible correlation between the fitting parameters is also discussed.
117727003
Neutrinos as Hot or Warm Dark Matter
Both active and sterile sub-eV neutrinos can serve for hot dark matter (DM). On the other hand, keV sterile neutrinos could be a good candidate for warm DM. The beta-decaying (e.g., H-3 and Ru-106) and EC-decaying (e.g., Ho-163) nuclei are considered as the most promising targets to capture those extremely low energy neutrinos and antineutrinos, respectively. We calculate the capture rates of relic electron neutrinos and antineutrinos against the corresponding beta-decay or EC-decay backgrounds in different flavor mixing schemes. We stress that such direct laboratory measurements of hot or warm DM might not be hopeless in the long term.
118445342
Shifts of neutrino oscillation parameters in reactor antineutrino experiments with non-standard interactions
We discuss reactor antineutrino oscillations with non-standard interactions (NSIs) at the neutrino production and detection processes. The neutrino oscillation probability is calculated with a parametrization of the NSI parameters by splitting them into the averages and differences of the production and detection processes respectively. The average parts induce constant shifts of the neutrino mixing angles from their true values, and the difference parts can generate the energy (and baseline) dependent corrections to the initial mass-squared differences. We stress that only the shifts of mass-squared differences are measurable in reactor antineutrino experiments. Taking hangmen Underground Neutrino Observatory (JUNO) as an example, we analyze how NSIs influence the standard neutrino measurements and to what extent we can constrain the NSI parameters. (C) 2014 The Authors. Published by Elsevier B.V.
120312696
A study of the CKM angle $\gamma$ using the LHCb experiment and a distributed workload management system
The LHCb experiment, at the Large Hadron Collider (LHC), will make precision CP violation measurements and search for new physics beyond the Standard Model of particle physics. The 14 TeV proton-proton collisions at the LHC will produce the full range of B-hadrons, at a data rate of peta-bytes per year. In order to process this unprecedented amount of data, distributed computing resources (the Grid) located across four continents are coordinated by a series of workload management systems (Grid middlewares). DIRAC, the LHCb distributed workload management system for event simulation, reconstruction and user analysis is extended from the Linux operating platform to the Windows platform, allowing a transparent integration of Windows resources to the existing Linux system. The B±→ D/D (KS π π−) K± decay, a key channel for the precision measurement of the CKM angle γ, is studied using the multiplatform DIRAC system. The expected annual yield from this channel for 2 fb−1 of data (a full data taking year) is ∼4200 events, with a total physics background to signal ratio (B/S) of < 0.54 at the 90% confidence level. The dominant background is expected to arise from a real D/D candidate reconstructed with a fake kaon from the underlying event, with a B/S = 0.35± 0.03 where the error is statistical. The potential background arising from a real D/D candidate reconstructed with a mis-identified pion is greatly reduced, with a B/S < 0.095 at the 90% confidence level, by the use of particle identification information from the RICH sub-detector. The estimated LHCb statistical sensitivity to γ is ∼12° for 2 fb−1 of data, using a model dependent Dalitz analysis with a model error of ∼9°.
120831466
Noncoplanarity effects in proton-proton bremsstrahlung
Noncoplanarity in proton-proton bremsstrahlung is investigated. Significant effects are observed for certain photon polar angles, psi(gamma). Such noncoplanarity effects, not of dynamical origin, are possibly responsible for past disagreements between theory and experiment. The Harvard noncoplanar coordinate system, which avoids kinematic singularities in the cross section, is used in our calculations and is recommended for use in the analysis of experimental data. Alternative methods of presenting cross sections are discussed. [S0556-2813(98)50110-0].
124761141
Population transfer to supercritical bound states during pair creation
We study the electron-positron pair-creation process from the vacuum under a very strong electric field. The external field is so strong that discrete states can dive into the negative energy continuum (the Dirac sea). This process is simultaneously associated with the onset of pair creation as well as the possibility for capturing the created electrons. By varying the total spatial width of the potential well, we can shift these trapping states in and out of the negative energy continuum while keeping the associated electric force the same. We compute the population transfer in and out of these states by solving the corresponding quantum field theoretical equations for the field operator on a space-time grid. We compare the population of these states obtained by projecting the time-evolved states on instantaneous energy eigenstates with the kinetic-energy spectrum of the ejected positrons.
119512566
Drell-Hearn-Gerasimov sum-rule for the deuteron in nuclear effective field theory
Abstract The Drell–Hearn–Gerasimov sum rule for the deuteron is studied in nuclear effective field theory. The low-energy theorem for the spin-dependent Compton amplitude f 1 ( ω ) is derived to the next-to-leading order in low-energy expansion. The spin-dependent photo-disintegration cross-section σ P − σ A is calculated to the same order, and its contribution to the dispersive integral is evaluated.
123491963
Noncoplanarity in proton-proton bremsstrahlung
Using the soft-photon approximation, we address the issue of the importance of noncoplanarity effects in proton-proton bremsstrahlung, We investigate the noncoplanar cross section as a function of the noncoplanarity angle (φ) over bar for the entire range of the photon polar angle psi(gamma). The (φ) over bar dependence is shown to provide a significant variation in the cross section, for a given psi(gamma). Thus, there can be some uncertainty in determining experimental coplanar cross sections. To avoid the phase-space singularities of spherical geometry. we utilize the Harvard noncoplanar geometry. A detailed explication of the Harvard geometry is provided, Comparison of our calculations with experimental data is included.