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.
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.
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.
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.
121227319
What is the Energy Scale of the Physics Responsible for Neutrino Masses
The observed tiny but non-zero neutrino masses are often interpreted as evidence for new physics at energy scales above 1010 TeV. This statement is based on several assumptions, including (a) neutrinos are Ma-jorana fermions, (b) the physics responsible for neutrino masses is not very weakly coupled, and (c) the new physics sector – responsible for lepton number breaking – couples to the Standard Model in a 'simple' way. We point out that the issue of the energy scale associated to neutrino masses is far from a resolved and that we should turn to data in order to elucidate it. In particular, if one opts out of (c), the new physics responsible for neutrino masses could be associated to energy scales anywhere between 0.1 and 1012 TeV, even if one assumes that the new physics couplings to the standard model are order one. We study the neutrino phenomenology of all possible effective operators that break lepton number by two units and use those as estimates of the effect of 'all' models of high energy lepton-number breaking. We then estimate the effects of these different types of new physics on other lepton-number violating observables, including neutrinoless double-beta decay, collider signatures, and rare meson decays.
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.
125191465
On the role of fixed angular-momentum-plane branch points, with regard to thet = 0 singularity structure of Reggeized scattering amplitudes
SummaryA generating function for the Feynman amplitude for the scattering of four massive spinless particles due to the exchange of a spin-J particle, described by a (J, 0) field of Weinberg, is obtained. The amplitude is then Reggeized by way of the Van Hove model, and the resulting Reggeized amplitude is found to receive contributions from a single Regge pole, and a sequence of fixedJ-plane branch points. The leading fixed branch point is shown to play an important role with regard to thet=0 singularity structure of the Reggeized amplitude, whilst the secondary fixed branch points are of no obvious significance. Also, within the context of the Van Hove model, connections between thet=0 singularity structure of Reggeized scattering amplitudes and the choice of interaction Hamiltonian density, are discussed.RiassuntoSi ottiene una funzione generatrice per l’ampiezza di Feynman dello scattering di quattro particelle senza spin, ma con massa, dovuto allo scambio di una particella con spinJ, descritto da un campo di Weinberg (J, 0). Si reggeizza poi l’ampiezza tramite il modello di Van Hove, e si trova l’ampiezza reggeizzata risultante ricevere contributi da un singolo polo di Regge, ed una sequenza di punti di ramificazione fissi del pianoJ. Si mostra che il punto di diramazione fisso principale giuoca un ruolo importante rispetto alla struttura della singolaritàt=0 dell’ampiezza reggeizzata, mentre i punti di diramazione fissi secondari non hanno un ovvio significato. Si discutono anche, nel contesto del modello di Van Hove, le connessioni fra la struttura della singolaritàt=0 delle ampiezze di scattering reggeizzate e la scelta delle densità dell’hamiltoniano di interazione.РеэюмеВыводится проиэводяшая функция для фейнмановской амплитуды для рассеяния четырех массивных бесспиновых частиц вследствие обмена частицей со спиномJ, которая описывается полем (J, 0) Вейнберга. Затем с помошью модели Ван Хова зта амплитуда реджеиэуется. Обнаружено, что реэультируюшая реджеи-эованная амплитуда содержит вклады от отдельного полюса Редже и последовательности фиксированных точек ветвления вJ-плоскости. Покаэывается, что главная фиксированная точка ветвления играет важную роль в структуре сингулярности приt=0 реджеиэованной амплитуды, тогда как вторичные фиксированные точки ветвления не имеют явного смысла. В свяэи с моделью Ван Хова также обсуждается свяэь между структурой сингулярности приt=0 реджеиэованных амплитуд рассеяния и выбором плотности Гамильтониана вэаимодействия.
122319907
The propagation of an interacting spin one field
118501099
Daughters and Weinberg field theory
SummaryA recurrence relation is obtained for the Feynman amplitude for the scattering of four spinless particles due to the exchange of a particle with spinJ, described by a (J, 0) field of Weinberg. It is shown that lower-spin contributions still occur in the amplitude, even though there are no redundant components in the spinor field.RiassuntoSi ottiene una relazione di ricorrenza per l'ampiezza di Feynmann dello scattering di quattro particelle prive di spin dovuto allo scambio di una particella di spinJ, descritto da un campo (J, 0) di Weinberg. Si dimostra che nell'ampiezza si ha ancora il contributo dello spin minore, anche se nel campo spinoriale non si hanno componenti ridondanti.РезюмеПолучается рекурентное соотношение для фейнмановской амплитуды рассеяния четырех бесспиновых частиц, обусловленное обменом частицы со спиномJ, которая описывается (J, 0) полем Вейнберга. Показывается, что в амплитуде все же имеется вклад от более низкого спина, даже если не существуют ишбыточные компоненты в спинорном поле.
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.