117798634
Non-oscillation probes of the neutrino mass hierarchy and vanishing |U(e3)|
One of the outstanding issues in neutrino physics is the experimental determination of the neutrino mass hierarchy: Is the order of the neutrino masses ``normal'' - m_1^2<m_2^2<m_3^2 - or is it inverted - m_3^2<m_1^2<m_2^2, with m_2^2-m_1^2 << m_2^2,m_1^2? While this issue can be resolved in next-generation long-baseline nu_{mu} to nu_e neutrino oscillation studies if |U_{e3}|^2 is large enough, a clear strategy on how to resolve it if |U_{e3}|^2 is sufficiently small is still lacking. We study the capability of non-oscillation probes of neutrino masses to determine the neutrino mass ordering. We concentrate on studies of m_{nu_e}, the kinematical neutrino mass to which precise studies of tritium beta-decay are sensitive, m_{ee}, the effective mass to which the rate for neutrinoless double-beta decay is sensitive if the neutrinos are Majorana fermions, and Sigma, the sum of the neutrino masses, to which cosmological probes of the energy budget of the Universe are sensitive. We find that combined measurements of m_{ee}, Sigma, and m_{nu_e} are capable of establishing the neutrino mass hierarchy if these measurements are precise enough and if one ``gets lucky.'' We quantify the previous sentence in detail by performing a numerical analysis of a large number of theoretical data sets, for different measured values of m_{nu_e}, m_{ee}, and Sigma, keeping in mind the ultimate sensitivity that can be reached by next (and next-to-next) generation experiments.
1539910
A phenomenological study of photon production in low energy neutrino nucleon scattering
Low energy photon production is an important background to many current and future precision neutrino experiments. We present a phenomenological study of t-channel radiative corrections to neutral current neutrino nucleus scattering. After introducing the relevant processes and phenomenological coupling constants, we will explore the derived energy and angular distributions as well as total cross-section predictions along their estimated uncertainties. This is supplemented throughout with comments on possible experimental signatures and implications. We conclude with a general discussion of the analysis in the context of complimentary methodologies.
119284838
Physical range of majorana neutrino mixing parameters
If neutrinos are Majorana fermions, the lepton mixing parameter space consists of six mixing parameters: three mixing angles and three CP-odd phases. A related issue concerns the physical range of the mixing parameters. What values should these take so that all physically distinguishable mixing scenarios are realized? We present a detailed discussion of the lepton mixing parameter space in the case of two and three active neutrinos and in the case of three active and N sterile neutrinos. We emphasize that this question, which has been a source of confusion even among neutrino physicists, is connected to an unambiguous definition of the neutrino mass eigenstates. We find that all Majorana phases can always be constrained to lie between 0 and {pi}, and that all mixing angles can be chosen positive and at most less than or equal to {pi}/2 provided the Dirac phases are allowed to vary between -{pi} and {pi}. We illustrate our results with several examples. Finally, we point out that, in the case of new flavor-changing neutrino interactions, the lepton mixing parameter space may need to be enlarged. We properly qualify this statement, and offer concrete examples.
118891248
Neutrino mass hierarchy, vacuum oscillations, and vanishing|Ue3|
Is the relatively isolated member of the neutrino mass spectrum heavier or lighter than the two closely-spaced members? This question--the character of the neutrino mass hierarchy--is of great theoretical interest. All previously identified experiments for addressing it via neutrino oscillations require that the currently unknown size of the U{sub e3} element of the leptonic mixing matrix (parameterized by the unknown {theta}{sub 13} mixing angle) be sufficiently large, and will utterly fail in the limit {theta}{sub 13}{yields}0. For this reason, we explore alternative oscillation approaches that would still succeed even if {theta}{sub 13} vanishes. We identify several alternatives that require neither a nonzero vertical bar U{sub e3} vertical bar nor the presence of significant matter effects (even if the latter are unavoidable in the case of long-baseline, Earth-based experiments). All include multiple percent-level neutrino oscillation measurements, usually involving muon-neutrino (or antineutrino) disappearance and very long baselines. We comment on the degree of promise that these alternative approaches show.
119278741
Some radiative corrections to neutrino scattering: Neutral currents
With the advent of high precision neutrino scattering experiments comes the need for improved radiative corrections. We present a phenomenological analysis of some contributions to the production of photons in neutrino neutral current scattering that are relevant to experiments subsuming the 1 % level of accuracy.
119115901
Pseudo-Dirac Neutrinos in the New Standard Model
The addition of gauge-singlet fermions to the standard model Lagrangian renders the neutrinos massive and allows one to explain all that is experimentally known about neutrino masses and lepton mixing by varying the values of the Majorana mass parameters M for the gauge singlets and the neutrino Yukawa couplings {lambda}. Here we explore the region of parameter space where M values are much smaller than the neutrino Dirac masses {lambda}v. In this region, neutrinos are pseudo-Dirac fermions. We find that current solar data constrain M values to be less than at least 10{sup -9} eV, and discuss the sensitivity of future experiments to tiny gauge-singlet fermion masses. We also discuss a useful basis for analyzing pseudo-Dirac neutrino mixing effects. In particular, we identify a simple relationship between elements of M and the induced enlarged mixing matrix and new mass-squared differences. These allow one to directly relate bounds on the new mass-squared differences to bounds on the singlet fermion Majorana masses.
122901453
Some remarks on an equivalence theorem for an interacting massive spin one particle in quantum field theory
The quantization of a massive spin one particle field, satisfying the first order system of equations due to Proca, is summarized. The interaction of such a field with an arbitrary field is then considered. Equivalent theories in terms of vector and antisymmetric second rank tensor spin one fields are then constructed in a simple manner, providing a generalization of an equivalence theorem due to the author. In addition, this approach, involving the use of first order systems of equations, allows a simple extension to the case of equivalence theorems for arbitrary integral spin. The nature of this extension is indicated.
120287965
Some remarks on causality, Lorentz invariance and the generalized Matthews' rule for a massive spin one vector field in an external potential
A massive spin one vector field is quantized in the presence of an external potential, with source linear in the vector field, to provide an illustration of the aspects of a quantum theory in an external potential, which are reflections of the causal nature of the corresponding classical theory. In the examples considered, the S operator of the quantum theory is found to be Lorentz invariant or not, according as the corresponding classical theory is causal or not. The normal dependence of the interaction hamiltonian, and the applicability of the generalized Matthews' rule are also discussed.
119095778
Initial optical results for the ChaMPlane Survey
We provide a brief description of the optical survey being conducted under the NOAO Long Term Surveys program in support of the Chandra Multiwavelength Plane (ChaMPlane) Survey (see paper by Grindlay et al. in this Volume). A representative photometry result is shown, along with spectroscopic followup.
122863150
Comments on the paper «Equivalence theorems for massive spin-one particles»
122775679
An equivalence theorem for a massive spin one particle interacting with Dirac particles in quantum field theory
The (1,0)(+)(0,1) massive spin one field phi mu nu (x) is quantized following the method of Takahashi and Umezawa (1953). The interaction Hamiltonian in the interaction picture is then calculated for such a field interacting in a simple way with Dirac fields. In contrast with a remark of Kyriakopoulos (1969) the generalized Matthews' theorem is found to apply to the calculation of S matrix elements. The analogous theory in terms of the Proca field is given in outline, and the two theories are found to be inequivalent. A discussion of how the inequivalence arises is given; then it is demonstrated how equivalent theories may be constructed, and the equivalence is proved.