Measurement of the neutrino velocity with the OPERA detector in the CNGS beam

TL;DR

The OPERA experiment measured neutrino velocities over 730 km, finding results consistent with neutrinos traveling at the speed of light within experimental uncertainties, using upgraded timing and geodesy methods.

Contribution

This study provides a precise measurement of neutrino velocity over long baseline, confirming consistency with the speed of light and improving systematic and statistical accuracy.

Findings

Neutrino velocity consistent with speed of light within uncertainties

Achieved high-precision timing and baseline measurements

Confirmed results with short bunch beam tests

Abstract

The OPERA neutrino experiment at the underground Gran Sasso Laboratory has measured the velocity of neutrinos from the CERN CNGS beam over a baseline of about 730 km. The measurement is based on data taken by OPERA in the years 2009, 2010 and 2011. Dedicated upgrades of the CNGS timing system and of the OPERA detector, as well as a high precision geodesy campaign for the measurement of the neutrino baseline, allowed reaching comparable systematic and statistical accuracies. An arrival time of CNGS muon neutrinos with respect to the one computed assuming the speed of light in vacuum of (6.5 +/- 7.4(stat.)((+8.3)(-8.0)sys.))ns was measured corresponding to a relative difference of the muon neutrino velocity with respect to the speed of light (v-c)/c =(2.7 +/-3.1(stat.)((+3.4)(-3.3)(sys.))x10^(-6). The above result, obtained by comparing the time distributions of neutrino interactions and of protons hitting the CNGS target in 10.5 microseconds long extractions, was confirmed by a test performed at the end of 2011 using a short bunch beam allowing to measure the neutrino time of flight at the single interaction level.