Superluminal Neutrinos Research Articles

The ICARUS experiment and the neutrino velocity measurement

ICARUS T600 Liquid Argon (LAr) Time Projection Chamber (TPC) is located in the HALL B of the Gran Sasso National Laboratory, on axis with the CNGS neutrino beam. It is smoothly and continuously operating since June 2010. The experiment has proved to be well suited to address the superluminal neutrino problem firstly raised by the OPERA experiment. As A.G.Cohen and S.L.Glashow argued, Super-luminal muon neutrinos should lose their energy by producing photons and e+e− bremsstrahlung pairs, in analogy with Čerenkov radiation. The lack of observation of such a radiative process in the ICARUS T600 detector, using the CNGS beam neutrino events, immediately refuted a superluminal interpretation of the OPERA result. Moreover the ICARUS collaboration, profiting of two short periods of CNGS beam operation in bunched mode, repeatedly performed a high precision measurement of the neutrino time-of-flight (to∫) which resulted to be compatible with the time-of-flight of a particle traveling at the speed of light: the difference between the expected value based on the speed of light and the measured value is δt=to∫c−to∫ν=0.10±0.67stat±2.39syst ns.

Status of the ICARUS experiment

The ICARUS-T600 detector, a∼760t liquid Argon TPC able to combine “bubble chamber” quality imaging capabilities with excellent calorimetric measurements, is presently operational at the LNGS underground laboratory for a rich physics program, covering cosmic neutrinos, nucleon decay search and neutrino oscillations with the CNGS neutrino beam.The successful detector commissioning and the ongoing data taking and analysis of the recorded events demonstrate the excellent performance of this LAr-TPC, which marks also a major milestone towards the practical realization of large-scale LAr detectors.In addition, exposed at the dedicated CNGS bunched beam, the ICARUS experiment has been able to accurately measure the CERN to LNGS neutrino time of flight, setting a tight limits on superluminal neutrino velocities.

Neutrino Velocity: Results and prospects of experiments at beamlines other than CNGS

In response to the 2011 report of superluminal neutrinos made by the OPERA collaboration, both MINOS and T2K developed plans to upgrade their timing systems to be able to measure neutrino time-of-flight with increased accuracy. In addition, MINOS has undertaken an analysis of the data taken with their old timing system, substantially improving the accuracy of their 2007 measurement, and deriving a result fully consistent with neutrinos travelling at the speed of light.

Neutrino Oscillations and Superluminal Propagation, in OPERA or Otherwise

We digress on the implications of recent claims of superluminal neutrino propagation. No matter how we turn it around such behaviour is very odd and sits uncomfortably even within “far-fetched” theories. In the context of non-linear realizations of the Lorentz group (where superluminal misbehaviour is run of the mill) one has to accept rather contrived constructions to predict superluminal properties for the neutrino. The simplest explanation is to require that at least one of the mass states be tachyonic. We show that due to neutrino mixing, the flavor energy does not suffer from the usual runaway pathologies of tachyons. For non-tachyonic mass states the theories become more speculative. A neutrino specific dispersion relation is exhibited, rendering the amplitude of the effect reasonable for a standard Planck energy. This uses the fact that the beam energy is close to the geometrical average of the neutrino and Planck mass; or, seen in another way, the beam energy is unexceptional but its gamma factor is very large. A dispersion relation crossing over from a low energy bradyonic branch to a high energy tachyonic one is also considered. We comment on consistency with SN 1987Awithin these models.

Neutrinos as Superluminal Particles

Based on parity violation in the weak interaction and evidences from neutrino oscillation, a natural choice is that neutrinos may be superluminal particles with tiny mass. To keep causality for Superluminal particles, a kinematic time under a non-standard form of the Lorentz transformation is introduced. A Dirac-type equation for Superluminal neutrinos is further investigated, and its solution is brief discussed. This equation can be written in two spinor equations coupled together via tiny mass while respecting maximum parity violation. As a consequence, parity violation implies that the principle of relativity is violated in the weak interaction.

VELOCITÀ LIMITE, CAUSALITÀ E TEST DELLA RELATIVITÀ RISTRETTA

With reference to the claim, subsequently withdrawn, by the “OPERA” collaboration of “National Gran Sasso Laboratories” of the observation of superluminal neutrinos, I briefly recall some basic principles of Relativity Theory and discuss some very stringent positive tests that come from the lack of observation of some effect of the type of Cherenkov effect and indirectly from the OPERA results themselves as stressed by some authors.

THE SUPERLUMINAL NEUTRINOS FROM DEFORMED LORENTZ INVARIANCE

We study two superluminal neutrino scenarios where [Formula: see text] is a constant. To be consistent with the OPERA, Borexino and ICARUS experiments and with the SN1987a observations, we assume that δvν on the Earth is about three-order larger than that on the interstellar scale. To explain the theoretical challenges from the Bremsstrahlung effects and pion decays, we consider the deformed Lorentz invariance, and show that the superluminal neutrino dispersion relations can be realized properly while the modifications to the dispersion relations of the other Standard Model particles can be negligible. In addition, we propose the deformed energy and momentum conservation laws for a generic physical process. In Scenario I the momentum conservation law is preserved while the energy conservation law is deformed. In Scenario II the energy conservation law is preserved while the momentum conservation law is deformed. We present the energy and momentum conservation laws in terms of neutrino momentum in Scenario I and in terms of neutrino energy in Scenario II. In such formats, the energy and momentum conservation laws are exactly the same as those in the traditional quantum field theory with Lorentz symmetry. Thus, all the above theoretical challenges can be automatically solved. We show explicitly that the Bremsstrahlung processes are forbidden and there is no problem for pion decays.

Tachyonic neutrinos and the neutrino masses

With a recent claim of superluminal neutrinos shown to be in error, 2012 may not be a propitious time to consider the evidence that one or more neutrinos may indeed be tachyons. Nevertheless, there are a growing number of observations that continue to suggest this possibility – albeit with an mν2<0 having a much smaller magnitude than was implied by the original OPERA claim. One recently published non-standard analysis of SN 1987A neutrinos supports a tachyonic mass eigenstate, and here we show how it leads to 3+3 mirror neutrino model having an unconventional mass hierarchy. The model incorporates one superluminal active–sterile neutrino pair, and it is testable in numerous ways, including making a surprising prediction about an unpublished aspect of the SN 1987A neutrinos. Additional supporting evidence involving earlier analyses of cosmic rays is summarized to add credence to the tachyonic neutrino hypothesis.

Time-Shift in the OPERA Setup: Proof against Superluminal Neutrinos without the need of knowing the CERN-LNGS distance and Reminiscences on the Origin of the Gran Sasso Lab, of the Third Neutrino and of the "Teramo Anomaly"

The LVD time stability allows one to establish a time-shift in the OPERA experiment, thus providing the first proof against superluminal neutrinos, using the horizontal muons of the "Teramo Anomaly." This proof is particularly interesting because it does not need the knowledge of the distance between the location at which the neutrinos are produced (CERN) and the location they are detected (LNGS). Since the superluminal neutrinos generated in the physics community a vivid interest in good and bad behavior in physics research, the author thought it was appropriate to recall the origin of the Gran Sasso Lab, of the third neutrino, of the horizontal muons due to the "Teramo Anomaly" and of the oscillation between leptonic flavors, when the CERN-Gran Sasso neutrino beam was included in the project for the most powerful underground laboratory in the world.

Testing the special relativity theory with neutrino interactions

A recent measurement of the neutrino velocity by the OPERA experiment and the prediction of energy loss of superluminal neutrinos via the pair creation process ν → νe+e− stimulated a search of isolated e+e− pairs in detectors with good tracking capability traversed by a large flux of high-energy neutrinos like NOMAD. NOMAD has already searched for similar topologies. These results can be reinterpreted to provide stringent limits on special-relativity-violating parameters separately for each ν species.

ERRATUM: "TIME-SHIFT IN THE OPERA SETUP: PROOF AGAINST SUPERLUMINAL NEUTRINOS WITHOUT THE NEED OF KNOWING THE CERN–LNGS DISTANCE AND REMINISCENCES ON THE ORIGIN OF THE GRAN SASSO LAB, OF THE THIRD NEUTRINO AND OF THE "TERAMO ANOMALY""

The LVD time stability allows one to establish a time-shift in the OPERA experiment, thus providing the first proof against superluminal neutrinos, using the horizontal muons of the Teramo Anomaly. This proof is particularly interesting since it does not need the knowledge of the distance between the location at which the neutrinos are produced (CERN) and the location they are detected (LNGS). Since the superluminal neutrinos generated in the physics community a vivid interest in good and bad behavior in physics research, the author thought it was appropriate to recall the origin of the Gran Sasso Lab, of the third neutrino, of the horizontal muons due to the Teramo Anomaly and of the oscillation between leptonic flavors, when the CERN–Gran Sasso neutrino beam was included in the project for the most powerful underground laboratory in the world.

Tachyonic field theory and neutrino mass running

Abstract In this paper three things are done. (i) We investigate the analogues of Cerenkov radiation for the decay of a superluminal neutrino and calculate the Cerenkov angles for the emission of a photon through a W loop, and for a collinear electron-positron pair, assuming the tachyonic dispersion relation for the superluminal neutrino. The decay rate of a freely propagating neutrino is found to depend on the shape of the assumed dispersion relation, and is found to decrease with decreasing tachyonic mass of the neutrino. (ii)We discuss a few properties of the tachyonic Dirac equation (symmetries and plane-wave solutions), which may be relevant for the description of superluminal neutrinos seen by the OPERA experiment, and discuss the calculation of the tachyonic propagator. (iii) In the absence of a commonly accepted tachyonic field theory, and in view of an apparent “running” of the observed neutrino mass with the energy, we write down a model Lagrangian, which describes a Yukawa-type interaction of a neutrino coupling to a scalar background field via a scalar-minus-pseudoscalar interaction. This constitutes an extension of the standard model. If the interaction is strong, then it leads to a substantial renormalization-group “running” of the neutrino mass and could potentially explain the experimental observations.

TIME-SHIFT IN THE OPERA SETUP: PROOF AGAINST SUPERLUMINAL NEUTRINOS WITHOUT THE NEED OF KNOWING THE CERN–LNGS DISTANCE AND REMINISCENCES ON THE ORIGIN OF THE GRAN SASSO LAB, OF THE THIRD NEUTRINO AND OF THE "TERAMO ANOMALY"

The LVD time stability allows one to establish a time-shift in the OPERA experiment, thus providing the first proof against superluminal neutrinos, using the horizontal muons of the "Teramo Anomaly." This proof is particularly interesting since it does not need the knowledge of the distance between the location at which the neutrinos are produced (CERN) and the location they are detected (LNGS). Since the superluminal neutrinos generated in the physics community a vivid interest in good and bad behavior in physics research, the author thought it was appropriate to recall the origin of the Gran Sasso Lab, of the third neutrino, of the horizontal muons due to the "Teramo Anomaly" and of the oscillation between leptonic flavors, when the CERN–Gran Sasso neutrino beam was included in the project for the most powerful underground laboratory in the world.

NEUTRINO SHORTCUTS IN SPACETIME

Theories with large extra dimensions may be tested using sterile neutrinos living in the bulk. A bulk neutrino can mix with a flavor neutrino localized in the brane leading to unconventional patterns of neutrino oscillations. A resonance phenomenon, strong mixing between the flavor and the sterile neutrino, allows one to determine the radius of the large extra dimension. If our brane is curved, then the sterile neutrino can take a shortcut through the bulk, leading to an apparent superluminal neutrino speed. The amount of "superluminality" is directly connected to parameters determining the shape of the brane. On the experimental side, we suggest that a long baseline neutrino beam from CERN to NESTOR neutrino telescope will help to clarify these important issues.

Superluminal neutrino phenomenon as a result of the equivalence principle violation

In this paper we show that the recently detected superluminal neutrino motion, which now is believed to be the result of a possible technical fault in the experiment, can alternatively be explained by the absence of the gravitational mass of the neutrino, and as a result, an absence of its interaction with a gravitational field. The neutrino velocity theoretically predicted in this paper is in full agreement with the experimental data obtained by the OPERA collaboration. The conducted calculations also predict a significant anisotropy of the neutrino velocity measurement depending on the direction of the Earth’s motion relative to the Galaxy, which allows for the validation of the obtained results.

Last word on faster-than-light neutrinos

Last word on faster-than-light neutrinos

Constraining neutrino superluminality from searches for sterile neutrino decays

Superluminal neutrinos are expected to lose energy due to bremsstrahlung. It is dominated by e+e−-pair production if kinematically allowed. The same signature was used in searches for 3-body decays of hypothetical heavy sterile neutrinos. From the published analyses of these searches performed by CERN PS191 and CHARM experiments we set upper limits on the neutrino velocity in the energy range from 0.2 GeV to 280 GeV. Our limits are well below the neutrino velocity favored by the recent OPERA results. For energy-independent neutrino velocity the limits obtained in this Letter are stronger than those coming from ICARUS experiment and observations of Supernova SN1987a.

Uncertainties in constraints from pair production on superluminal neutrinos

The use of the vacuum lepton pair production process ($\nu \to \nu e^- 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.

Background-dependent Lorentz violation: natural solutions to the theoretical challenges of the superluminal neutrino propagation

To explain both the OPERA experiment and all the known phenomenological constraints/observations on Lorentz violation, the Background Dependent Lorentz Violation (BDLV) has been proposed. We study the BDLV in a model independent way, and conjecture that there may exist a "Dream Special Relativity Theory", where all the Standard Model (SM) particles can be subluminal due to the background effects. Assuming that the Lorentz violation on the Earth is much larger than those on the interstellar scale, we automatically escape all the astrophysical constraints on Lorentz violation. For the BDLV from the effective field theory, we present a simple model and discuss the possible solutions to the theoretical challenges of the OPERA experiment such as the Bremsstrahlung effects for muon neutrinos and the pion decays. Also, we address the Lorentz violation constraints from the LEP and KamLAMD experiments. For the BDLV from the Type IIB string theory with D3-branes and D7-branes, we point out that the D3-branes are flavour blind, and all the SM particles are the conventional particles as in the traditional SM when they do not interact with the D3-branes. Thus, we not only can naturally avoid all the known phenomenological constraints on Lorentz violation, but also can naturally explain all the theoretical challenges. Interestingly, the energy dependent photon velocities may be tested at the experiments.

On Superluminal Particles and the Extended Relativity Theories

Superluminal particles are studied within the framework of the Extended Relativity theory in Clifford spaces (C-spaces). In the simplest scenario, it is found that it is the contribution of the Clifford scalar component π of the poly-vector-valued momentum which is responsible for the superluminal behavior in ordinary spacetime due to the fact that the effective mass \(\mathcal{M} = \sqrt{ M^{2} - \pi^{2} }\) is imaginary (tachyonic). However, from the point of view of C-space, there is no superluminal (tachyonic) behavior because the true physical mass still obeys M2>0. Therefore, there are no violations of the Clifford-extended Lorentz invariance and the extended Relativity principle in C-spaces. It is also explained why the charged muons (leptons) are subluminal while its chargeless neutrinos may admit superluminal propagation. A Born’s Reciprocal Relativity theory in Phase Spaces leads to modified dispersion relations involving both coordinates and momenta, and whose truncations furnish Lorentz-violating dispersion relations which appear in Finsler Geometry, rainbow-metrics models and Double (deformed) Special Relativity. These models also admit superluminal particles. A numerical analysis based on the recent OPERA experimental findings on alleged superluminal muon neutrinos is made. For the average muon neutrino energy of 17 GeV, we find a value for the magnitude \(|\mathcal{M } | = 119.7\mbox{~MeV}\) that, coincidentally, is close to the mass of the muon mμ=105.7 MeV.