Constraints on the interpretation of the superluminal motion of neutrinos at OPERA

Abstract

Various approaches aim to describe the recent analysis by the OPERA experiment, which indicates that neutrinos travel faster than the speed of light. We demonstrate that any such theoretical or experimental explanation must not destroy the complicated (nonlinear) structure of the proton waveform recovered in the neutrino signal. As one example, consider that only a fraction of the neutrinos travels faster than the speed of light, such as sterile neutrinos. We fit the OPERA data including this fraction as a free variable, assuming that the OPERA result is correct. In our analysis, the best-fit values are 50% of the neutrinos being superluminal and ðv À cÞ=c ¼ 4:5 Á 10 À5 , where the neutrino velocity increases as the fraction of superluminal neutrinos decreases. The minimal fraction of superluminal neutrinos is found to be 17% (3), which is constrained by the nonlinearity of the proton waveform. This minimal fraction challenges the hypothesis that only sterile neutrinos travel faster than the speed of light. In addition, we demonstrate that an experimental effect introducing a smearing between the proton waveform and neutrino signal, as expected for some systematical errors, is also limited by the shape of the waveform. Finally, we illustrate that even stronger constraints may be obtained from the recent analysis with a short-bunch beam, in spite of the low statistics.

Neutrino Splitting and Density-Dependent Dispersion Relations

“…It was also argued that one could escape by rendering other particles, such as the electron, superluminal [20,21] after all the dispersion relations could well be density dependent [22,23,24] and all strong constraints on electron velocities appear to come from experiments in a vacuum [24]. Another escape route is if, while traveling, the neutrinos are noninteracting because they are taking a short cut through another dimension [25], or converted into a sterile flavor [26]. While such models are no longer necessary to explain OPERA's anomaly, they may well resurface in attempts to explain the yet unexplained neutrino anomalies.…”

Sterile Neutrino Production Through a Matter Effect Enhancement at Long Baselines

“…This data turned out to be an experimental error. Nevertheless, the OPERA result prompted proposals of new physics [2][3][4][5][6] and phenomenological constraints on muon neutrino Lorentz invariance violation [2, 7,8]. One popular superluminal mechanism for neutrinos involved sterile neutrino transport through a higher dimensional bulk [9][10][11][12][13], which supposed active neutrinos confined to a D3 brane oscillate to sterile neutrinos, whose lack of gauge charge leaves them free to travel through large extra dimensions.…”

“…Although it is settled that the OPERA experiment * Electronic address: bramante@hawaii.edu did not observe a superluminal anomaly [1], nevertheless some of the phenomenological studies of sterile neutrino production at long baselines are applicable to future neutrino studies. In particular, among the many OPERA constraints papers that arose in the wake of the anomalous OPERA data [7] pointed out that the fraction of sterile neutrinos required to explain the anomaly was at odds with a prior study of sterile neutrinos at MINOS [21].…”

Neutrino Oscillations and Superluminal Propagation, in OPERA or Otherwise

“…As with any experimental result, these claims should be taken with a macroscopic grain of salt. The potential for uncharted systematic errors can never be overemphasized [5,6]. Nonetheless, theorists are easily excitable creatures who don't require much prompting before going down the "what if" alley [7,8].…”