This talk opens the CosPA2011 session on OPERA's superluminal neutrino claim. I summarize relevant observations and constraints from OPERA, MINOS, ICARUS, KamLAND, IceCube and LEP as well as observations of SN1987A. I selectively review some models of neutrino superluminality which have been proposed since OPERA's announcement, focusing on a neutrino dark energy model. Powerful theoretical constraints on these models arise from Cohen-Glashow bremsstrahlung and from phase space requirements for the initial neutrino production. I discuss these constraints and how they might be evaded in models in which the maximum velocities of both neutrinos and charged leptons are equal but only superluminal inside of a dense medium.
If the tau neutrino is as heavy as 10 MeV which may have certain astrophysical implications, the neutrino mass pattern is studied so as to accommodate the new oscillation observations. It predicts that the electron neutrino has Marjorana mass around 0.05 eV. A supersymmetric model is described to realize the above scenario.
We revisit the pair creation constraint on superluminal neutrinos considered by Cohen and Glashow in order to clarify which types of superluminal models are constrained. We show that a model in which the superluminal neutrino is effectively light-like can evade the Cohen-Glashow constraint.
We show that spin flavor precession solutions to the solar neutrino problem, although preferred by the latest solar data, are ruled out by the first results from the KamLAND reactor experiment, at more than 3_sigma. An illustrative chi2 plot comparing these descriptions with oscillations is given.
We consider a possibility that the recent OPERA results on neutrinos' superluminality could be caused by a local effect of a new gauge field sourced by the earth. If neutrinos couple to this gauge field via a gauge-invariant but non-renormalizable interaction, the coupling effectively changes a background metric, thereby leading to superluminality of neutrinos. This possibility naturally might explain why neutrinos from CERN CNGS beam to Gran Sasso Laboratory become superluminal while those from SN1987A to Earth become subluminal.
Experimental evidence and theoretical argument in favor the claim of neutrino being likely a superluminal particle, a tachyon, are discussed from six aspects with details.
In this article an idea is presented, which allows for the explanation of superluminal muon neutrinos. It is based on the introduction of a new superluminal, massless gauge boson coupling to the neutrino only, but not to other standard model particles. The model is discussed with regard to the Supernova 1987 (SN 1987) velocity bound on electron antineutrinos and the Cohen-Glashow constraint on superluminal neutrino propagation. The latter can be circumvented if - within the framework of the model - a sterile neutrino mixing with the active neutrino mass eigenstates is introduced. The suggestio…
The superluminal is reported in OPERA neutrino experiment (arXiv:1109.4897v2), this result is consistent with previous MINOS experiment about neutrino velocity (Phys. Rev. D 76, 072005 (2007)). Here we propose a Dirac equation of tachyon for superluminal neutrino in which the mass matrix is anti-hermitian. Additionally we find that this anti-hermitian mass matrix which is responsible for superluminal can only be for neutrinos, while other results of Standard Model are unchanged. In case that Lorentz invariant is remained, the masses of neutrinos are estimated based on available data of experim…
The toy fermion model coupled with Lagrange multiplier constraint field is proposed. The possibility of superluminal neutrino propagation as result of dynamical Lorentz symmetry breaking is studied.
We compare the solutions to the short baseline neutrino anomaly based on oscillations to sterile neutrinos and the Stochastic Neutrino Mixing Mechanism (SNMM) through an analysis of the present neutrino data. The SNMM suggests worse fits than a 3 + 1 sterile neutrino model, although it cannot be discarded by present data. We propose an experiment to distinguish between both solutions, based on placing a $^8$Li source inside a 5kton-yr detector (like SNO). We studied the sensitivity of such an experiment, which makes it possible to discriminate within $2σ$ the SNMM from the 3+1 sterile hypothes…
The OPERA collaboration recently reported that muon neutrinos could be superluminal. More recently, Cohen and Glashow pointed that such superluminal neutrinos would be suppressed since they lose their energies rapidly via bremsstrahlung. In this Letter, we propose that Finslerian nature of spacetime could account for the superluminal phenomena of particles. The Finsler spacetime permits the existence of superluminal behavior of particles while the casuality still holds. A new dispersion relation is obtained in a class of Finsler spacetime. It is shown that the superluminal speed is linearly de…
The splitting of neutrinos, a viable reaction for superluminal neutrinos, is shown to have phenomenologically relevant consequences if one accepts the recent OPERA results for the velocity of neutrinos. Neutrino splitting can be used to put strong constraints on the energy dependence of the velocity of propagation of neutrinos in a general analysis of modifications of relativistic kinematics and to propose observable effects due to the departures from special relativity in neutrino physics.
Recent experimental research progress of solar neutrino and neutrino oscillation reveals that neutrinos do have nonzero mass, which poses a serious challenge to theoretical physics. Two symmetries, the common invariance under the space-time inversion and the invariance or violation to maximum under the space inversion are analyzed for Dirac equation or the equation for superluminal neutrino respectively. Then a simple three-flavor model containing only one parameter is proposed and the relations among neutrino oscillation, parity violation and superluminal property are emphasized.
We show that in the presence of a distance dependent Lorentz-violating time-like background one may find superluminal neutrinos at some high energy such as OPERA's scale. The similar behavior but approaching the subluminal branch is found to appear for inflaton field in the low energy scale. Thus this scenario seems to be suitable to acomplish both superluminal neutrinos and dark energy.
The OPERA collaboration has claimed the discovery of supeluminal neutrino propagation. However the superluminal interpretation of the OPERA result was refuted by Cohen and Glashow because it was shown that such superluminal neutrinos would lose energy rapidly via the bremsstrahlung of electron-positron pairs (arXiv:1109.6562). We note that the superluminal interpretation is still possible if there exists a new (dark) neutrino which can propagate with a superluminal velocity and which couples with usual neutrinos only via the mass mixing leading to neutrino oscillations. It is supposed that the…
We show that the more energetic superluminal neutrinos with quadratically dispersed superluminalities δ=β^2-1, for β=v/c where v is the neutrino velocity, also lose significant energy to radiation to the ν+e^-+e^+ final state in travelling from CERN to Gran Sasso as has been shown to occur for those with constant superluminality by Cohen and Glashow if indeed δ\simeq 5\times 10^{-5}. In addition, we clarify the dependence of such radiative processes on the size of the superluminality.
Based on the experimental discovery that the mass-square of neutrino is negative, a quantum theory for superluminal neutrino is proposed. Two Weyl equations coupled together via a mass term respecting the maximum parity violation lead to a new equation which describes the superluminal motion of neutrino with permanent helicity. Various strange features of subluminal and superluminal particles can be ascribed to the relative variation of two contradictory fields superposing coherently inside the particle with the change of its speed u in the whole range ($0<u<\infty$). Being compatible with the…
We study neutrino physics in a model with one large extra dimension. We assume the existence of two four-dimensional branes in the five-dimensional space-time, one for the ordinary particles and the other one for mirror particles, and we investigate neutrino masses and mixings in this scheme. Comparison of experimental neutrino data with the predictions of the model leads to various restrictions on the parameters of the model. For instance, the size of the extra dimension, R, turns out to be bounded from below. Cosmological considerations seem to favor a large R. The usual mixing schemes propo…
An interpretation of the superluminal velocity observed by OPERA collaboration is given in terms wave packet distortion of ultrarelativistic massive neutrinos. Standard quantum-mechanical time evolution of physical states can explain the observed Delta x/Delta t > c without violating the fundamental principles of special relativity.
In this short note we remark that the OPERA measurement could be reconciled with information from SN1987a in the context of deformed special relativity without the loss of energy through Cherenkov-like process reported by Cohen and Glashow.
We consider Lorentz- and CPT-violating dimension-5 operators to address the issue of superluminal neutrinos recently pointed out in OPERA experiments. We assume these operators in the photon and neutrino sectors coupled to Lorentz-violating backgrounds in a preferred frame defined by a time-like direction. We show that such operators can produce a curve with OPERA's slope that fits OPERA, MINOS and supernova SN1987a data.
This report presents a brief review on the experimental measurements of the muon neutrino velocities from the OPERA, Fermilab and MINOS experiments and that of the (anti)-electron neutrino velocities from the supernova SN1987A, and consequently on the theoretical attempts to attribute the data as signals for superluminality of neutrinos. Different scenarios on how to understand and treat the background fields in the effective field theory frameworks are pointed out. Challenges on interpreting the OPERA result as a signal of neutrino superluminality are briefly reviewed and discussed. It is als…
It is suggested that recent superluminal neutrinos from the OPERA collaboration might indicate that there are other ultimate speeds than usual speed of light in our universe. The leptonic sector of the standard model (SM) is reformulated incorporating with new ultimate speeds. In minimal cases where there is another maximum speed $c'$ which equals to the speed of the OPERA neutrinos, new effects would appear at the level of ${\cal O}(10^{-5})$. Improved precisions for the electroweak observables would check the validity of this scenario.
Einstein's theory of special relativity(SR) and the principle of causality imply that the speed of any moving object can not exceed that of light in a vacuum($c$).However,there were many attempts in literature discussing the particle moving with speed $u>c$(called as superluminal particle or tachyon)either in the scheme of SR or beyond it.These theories all encountered a series of insurmountable difficulties which will be named ``superluminal paradox''in this paper.We will analyze it in some detail and then prove that the paradox disappears unambiguously in quantum theory,which is compatible w…
OPERA has claimed the discovery of superluminal propagation of neutrinos. We analyze the consistency of this claim with previous tests of special relativity. We find that reconciling the OPERA measurement with information from SN1987a and from neutrino oscillations requires stringent conditions. The superluminal limit velocity of neutrinos must be nearly flavor independent, must decrease steeply in the low-energy domain, and its energy dependence must depart from a simple power law. We construct illustrative models that satisfy these conditions, by introducing Lorentz violation in a sector wit…
The use of the vacuum lepton pair production process ($ν\to νe^- e^+ $), a viable reaction for superluminal neutrinos, to put constraints on Lorentz violations requires a dynamical framework. Different choices of dynamical matrix elements and modified dispersion relations for neutrinos, leading to numerical factors differing by one order of magnitude in the results for the pair production decay width, are used to show the uncertainties on these constraints.
The effect of nonlinear self-interaction can be associated with superluminal velocity of neutrino. The power energy spectrum E=p+Cp^a is derived from the nonlinear Dirac equation when interaction term V=λ(ψγ_μψψγ^μψ)^a is added to the Lagrangian of a free spin-1/2 particle. The superluminal velocity recorded by the OPERA and MINOS collaborations is achieved when the coupling constants are taken in the range a=0.4-1.18 and λ=-(0.5-1.6)x10^-4. The self-interaction Lagrangian V=λ(ψγ_μψψγ^μψ) with the coupling constant λ=-(0.7-0.9)x10^-4 yields the same result. Scalar interaction V=λ(ψψ)^b and sca…
We consider a restricted Type-I seesaw scenario with four texture zeros in the neutrino Yukawa matrix, in the weak basis where both the charged-lepton Yukawa matrix and the Majorana mass matrix for right-handed neutrinos are diagonal and real. Inspired by grand unified theories, we further require the neutrino Yukawa matrix to exhibit a similar hierarchical pattern to that in the up-type quark Yukawa matrix. With such a hierarchy requirement, we find that leptogenesis, which would operate in a $N_2^{}$-dominated scenario with the asymmetry generated by the next-to-lightest right-handed neutrin…
Recently, Cohen and Glashow [A.G. Cohen, S.L. Glashow, Phys. Rev. Lett. {\bf 107}, 181803 (2011)] pointed out that the superluminal neutrinos reported by the OPERA would lose their energy rapidly via the Cherenkov-like process. The Cherenkov-like process for the superluminal particles would be forbidden if the principle of special relativity holds in any frame instead violated with a preferred frame. We have proposed that the Finslerian special relativity could account for the data of the neutrino superluminality (arXiv:1110.6673[hep-ph]). The Finslerian special relativity preserves the princi…
Quantum coherence can significantly increase the strength of the forward scattering of neutrinos propagating through the Earth and interacting with matter. The index of refraction of the neutrinos propagating in a medium and hence their phase velocity is determined by the forward scattering. So, depending on the nature of the interaction of neutrinos with matter, their phase velocity can be larger than the speed of light in vacuum. We show that such effects can explain the apparent superluminal propagation of muon neutrinos found recently by the OPERA experiment. Our proposal explains why the …
Recently the OPERA collaboration {\cite{opera}} has reported the observation of superluminal neutrinos traveling a distance of 730 km from Grand Sasso Laboratory to CERN.These results contradict the basic tenet of the Theory of Special Relativity: No particle can travel faster than light in vacuum. Moreover they seem to be in conflict with the speed of (anti)neutrinos detected from the explosion of the SP1987A Super Nova{\cite{SP1987A}}.Here we show that the relative velocity between neutrino and photon has the following property: It depends weakly on the energy of the particle excepts in cert…
Recent neutrino oscillation results have evoked renewed interest in sterile neutrino oscillation models. This paper reviews the data from MiniBooNE and short-baseline reactor antineutrino experiments within the context of sterile neutrinos. The results are incorporated into combined fits to test the viability of sterile neutrino oscillation models, which are later expanded to address matter effects. Finally, future experiments that can resolve the questions that have been raised are discussed.
In the context of theories where particles can have different limiting velocities, we review the running of particle speeds towards a common limiting velocity at low energy. Motivated by the recent OPERA experimental results, we describe a model where the neutrinos would deviate from the common velocity by more than do other particles in the theory, because their running is slower due to weaker interactions.
In recent experiments conducted by the OPERA collaboration, researchers claimed the observation of neutrinos propagating faster than the light speed in vacuum. If correct, their results raise several issues concerning the special theory of relativity and the standard model of fundamental particles. Here, the physical consequences of superluminal neutrinos described by a tachyonic Dirac lagrangian, are explored within the standard model of electroweak interactions. If neutrino tachyonic behavior is allowed, it could provide a simple explanation for the parity violation in weak interactions and …
In this letter, we show that superluminal neutrinos announced by OPERA could be explained by the existence of a monopole, which is left behind after the spontaneous symmetry breaking (SSB) phase transition of some scalar fields in the universe. We assume the 't Hooft-Polyakov monopole couples to the neutrinos but not photon fields. The monopole introduces a different effective metric to the neutrinos from the one experienced by photons. We find that the superluminal propagation only exists in a very short distance from the monopole, about $10^3$ cm in OPERA. No matter how far they travel, neut…
The result of the OPERA experiment revealed that the velocity of muon-neutrinos was larger than the speed of light. We argue that this apparent superluminal velocity can be interpreted as a weak value, which is a new concept recently studied in the context of quantum physics. The OPERA experiment setup forms a scheme that manifests the neutrino velocity as a weak value. The velocity defined in the scheme of weak measurement can exceed the speed of light. The weak velocity is not a concept associated to a single phenomenon but it is a statistical concept defined by accumulating data at separate…
Most recently, the measurement of the neutrino velocity with the OPERA detector in the CNGS beam shows unexpected indication, that the muon neutrino velocity, $v_ν$, exceeds the velocity of light in the vacuum, $c$, which is obviously in contradiction with the most basic hypothesis of modern physics. Within the framework of minimal Standard Model Extension, we discuss the modified dispersion relation and consequently the velocity-energy relation of muon neutrinos. The simplified models are fit to the OPERA data, Fermilab experiment and MINO data. We find that minimal Standard Extension can des…
According to the measurement of muon-neutrino experiment done by the OPERA collaboration, the speed of high-energy neutrino exceeds that of light in vacuum by 25ppm. Assuming that this result is correct, a possible resolution of the dilemma between it and the validity of relativity is proposed without changing the framework of the Standard Model of elementary particles. The essential idea is based on a possible resolution, proposed previously, of the color confinement problem of quantum chromodynamics.
Motivated by the tentative observation of superluminal neutrinos by the OPERA experiment, we present a model of active-sterile neutrino oscillations in which sterile neutrinos are superluminal and active neutrinos appear superluminal by virtue of neutrino mixing. The model demonstrates some interesting possibilities and challenges that apply to a large class of models aiming to explain the OPERA result.
The present work introduces two possible extensions of the Standard Model Higgs sector. In the first case, the Zee-Babu type model for the generation of neutrino mass is augmented with a scalar triplet and additional singly charged scalar singlets. The second scenario, on the other hand, generalizes the Type-II seesaw model by replicating the number of the scalar triplets. A $\mathbb{Z}_3$ symmetry is imposed in case of both the scenarios, but, allowed to be violated by terms of mass dimension two and three for generating neutrino masses and mixings. We examine how the models so introduced can…
We suggest a possible interpretation of the recent observation by the OPERA collaboration of superluminal propagation of neutrinos. We show that it is in principle possible that the group velocity of neutrinos exceeds the speed of light without violating special relativity.
The recent OPERA experiment of superluminal neutrinos has deep consequences in cosmology. In cosmology a fundamental constant is the cosmological constant. From observations one can estimate the effective cosmological constant $Λ_{eff}$ which is the sum of the quantum zero point energy $Λ_{dark energy}$ and the geometric cosmological constant $Λ$. The OPERA experiment can be applied to determine the geometric cosmological constant $Λ$. It is the first time to distinguish the contributions of $Λ$ and $Λ_{dark energy}$ from each other by experiment. The determination is based on an explanation o…
The superluminal propagation of neutrinos observed by OPERA collaboration can be interpreted as neutrinos traveling in a pseudoscalar potential which may be generated by a medium. The OPERA differential arrival time data set a constraint on the form of the pseudoscalar potential.
We propose a new type of radiative neutrino model with a local hidden $U(1)$ symmetry, in which neutrino masses are induced at the three loop level, and discuss the muon anomalous magnetic moment, and dark matter candidates therein. By allowing the hypercharges larger than 3/2 for new fields that contribute to the neutrino masses and making them decay into the standard model fields appropriately, we introduce a lot of new particles with multiple electrical charges in a natural manner. As a by-product, we can accommodate the 750 GeV diphoton excess depending on the hypercharge quantum numbers o…
Quantum trajectories are used to study OPERA findings regarding superluminal neutrinos. As the applicable stationary quantum Klein-Gordon equation is real, real quantum reduced actions and subsequent real quantum trajectories follow. The requirements for superluminal neutrinos are examined. A neutrino that is self-entangled by its own backscatter is shown to have a nonlocal quantum trajectory that may generate a superluminal transit time. Various cases are shown to produce theoretical superluminal neutrinos consistent with OPERA neutrinos. Quantum trajectories are also shown to provide insight…
Modified neutrino dispersion relations, which still obey the relativity principle, can have both a superluminal (muon-type) neutrino and a luminal (electron-type) neutrino, as long as neutrino-mass effects can be neglected. The idea is to allow for flavor-dependent deformed Lorentz transformations and an appropriate hierarchy of energy scales. If OPERA's result on a superluminal velocity of the muon-neutrino is confirmed, the model has a matching superluminal velocity of the corresponding charged lepton, the muon, at equal particle energy. Assuming that this model is not already ruled out, new…
Non-dispersive wave packet for massless fermions is formulated on the basis of squeezed coherent states that are put in a form of common eigenfunction for the Hamiltonian and the helicity operator, starting from the Dirac equation. The wave packet thus constructed is demonstrated to propagate at a constant velocity as that of light. This explicit expression of wave packet for the massless fermions can facilitate theoretical analysis of problems where a wave packet is of formal significance. Furthermore, extensive wave packet may result in a superluminal velocity statistics if determined from t…
Several popular Ansätze of lepton mass matrices that contain texture zeros are confronted with current neutrino observational data. We perform a systematic $χ^2$-analysis in a wide class of schemes, considering arbitrary Hermitian charged lepton mass matrices and symmetric mass matrices for Majorana neutrinos or Hermitian mass matrices for Dirac neutrinos. Our study reveals that several patterns are still consistent with all the observations at 68.27% confidence level, while some others are disfavored or excluded by the experimental data. The well-known Frampton-Glashow-Marfatia two-zero textu…
We revisit the model building challenges that one faces when trying to reconcile the OPERA claim of neutrino superluminality with other observational constraints. The severity of the supernova bound and of the kinematical constraints of Cohen-Glashow type lead us to focus on scenarios where all types of particles are superluminal inside matter. In contrast to the Dvali-Vikman proposal, this matter effect needs to be very short-ranged to avoid constraints from experiments on the Earth's surface in low-density environments. Due to this short range, the interaction underlying such a matter effect…
A review is given of hypothetical faster-than-light tachyons and the development of the author's $3+3$ model of the neutrino mass states, which includes one tachyonic mass state doublet. Published empirical evidence for the model is summarized, including an interpretation of the mysterious Mont Blanc neutrino burst from SN 1987A as being due to tachyonic neutrinos having $m^2=-0.38 eV^2.$ This possibility requires an 8 MeV antineutrino line from SN 1987A, which a new dark matter model has been found to support. Furthermore, this dark matter model is supported by several data sets: $γ-$rays fro…
It is shown that the measured neutrino velocity, apparently violating relativity theory, is compatible with (general) relativistic causality provided that we assume that the metric of spacetime fluctuates at short distances.
The superluminal propagation of neutrinos observed by the OPERA collaboration can be explained by an energy dependent potential for the neutrino beam in passage through the Earth.
We argue that the recent measurement of the neutrino velocity to be higher than the velocity of light could be due to violation of Lorentz invariance by the muon neutrinos. This result need not undermine special-relativistic foundational notions of causality.
Tri-direct CP symmetry is an economical neutrino model building paradigm, and it allows to describe neutrino masses, mixing angles and CP violation phases in terms of four free parameters. Viability of a class of tri-direct CP models is examined with a comprehensive simulation of current and future neutrino oscillation experiments. Two benchmark models as well as the full parameter space are carefully scanned, and the parameter degeneracy problem is observed from the constraint of one group of neutrino oscillation experiments. Complementary roles from the accelerator neutrino experiments (e.g.…
The purpose of this paper is both to provide mathematical reinforcements to the paper [Mecozzi and Bellini : arXiv:1110.1253 [hep-ph]] by taking decoherence into consideration and to present some important problems related. We claim that neutrinos have superluminality as a latent possibility.
The analysis of the sample of charged current quasi elastic events collected by the MiniBooNE Collaboration suggests that the scheme successfully employed to describe electron-nucleus scattering fails to explain neutrino-nucleus cross sections. I argue that, due to flux average, the double differential neutrino-nucleus cross section does not allow for a clearcut determination of the dominant reaction mechanism. A systematic study of the large body of electron scattering data may help to identify the processes, other than single nucleon knockout, contributing to the observed neutrino cross sect…
We present an updated fit of supersymmetric SO(10) models to quark and lepton masses and mixing parameters. Including latest results from lattice QCD determinations of quark masses and neutrino oscillation data, we show that fits neglecting supersymmetric threshold corrections are strongly disfavoured in our setup. Only when we include these corrections we find good fit points. We present $χ^2$-profiles for the threshold parameters, which show that in our setup the thresholds related to the third generation of fermions exhibit two rather narrow minima.
The DArk Matter Particle Explorer (DAMPE) has observed a tentative peak at $E\sim1.4~\TeV$ in the cosmic-ray electron spectrum. In this paper, we interpret this excess in the scotogenic type-II seesaw model. This model extends the canonical type-II seesaw model with dark matter (DM) candidates and a loop-induced vacuum expectation value of the triplet scalars, $v_Δ$, resulting in small neutrino masses naturally even for TeV scale triplet scalars. Assuming a nearby DM subhalo, the DAMPE excess can be explained by DM annihilating into a pair of triplet scalars which subsequently decay to charged…
