Measurement of the neutrino velocity with the ICARUS detector at the CNGS beam

The ICARUS Collaboration

M. Antonello a, P. Aprili a, B. Baiboussinov b, M. Baldo Ceolin 1b, P. Benetti c,

E. Calligarich c, N. Canci a, S. Centro b, A. Cesana e, K. Cie slik f, D.B. Cline g,

A.G. Cocco d, A. Dabrowska f, D. Dequal b, A. Dermenev h, R. Dolfini c,

C. Farnese b, A. Fava b, A. Ferrari i, G. Fiorillo d, D. Gibin b, A. Gigli

Berzolari 1c, S. Gninenko h, A. Guglielmi b, M. Haranczyk f, J. Holeczek l,

A. Ivashkin h, J. Kisiel l, I. Kochanek l, J. Lagoda k, S. Mania l, G. Mannocchi m,

A. Menegolli c, G. Meng b, C. Montanari c, S. Otwinowski g, L. Periale m,
A. Piazzoli c, P. Picchi m, F. Pietropaolo c, P. Plonski n, A. Rappoldi c,

G.L. Raselli c, M. Rossella c, C. Rubbia a,i, P. Sala e, E. Scantamburlo j,

A. Scaramelli e, E. Segreto a, F. Sergiampietri o, D. Stefan f, J. Stepaniak k,

R. Sulej k, M. Szarska f, M. Terrani e, F. Varanini b, S. Ventura b, C. Vignoli a,

H.G. Wang g, A. Zalewska f, K. Zaremba n,

and

P. Alvarez Sanchez i, J. Serrano i

a INFN - Laboratori Nazionali del Gran Sasso, Assergi (AQ), Italy

b Dipartimento di Fisica e INFN, Universit a di Padova, Via Marzolo 8, Padova, Italy

c Dipartimento di Fisica e INFN, Università di Pavia, Via Bassi 6, Pavia, Italy

d Dipartimento di Scienze Fisiche e INFN, Università Federico II, Napoli, Italy

e INFN, Sezione di Milano e Politecnico, Via Celoria 16, Milano, Italy

f H.Niewodniczanski Institute of Nuclear Physics, Krakow, Poland

g Department of Physics and Astronomy, University of California, Los Angeles, USA

h Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia

i CERN, European Laboratory for Particle Physics, Geneve , Switzerland

j Universita di L'Aquila, via Vetoio, Località Coppito, L'Aquila, Italy

k A.Soltan Institute for Nuclear Studies, 05-400 Swierk/Otwock, Warszawa, Poland

l Institute of Physics, University of Silesia, Katowice, Poland

m INFN Laboratori Nazionali di Frascati, Via Fermi 40, Frascati, Italy

n Institute for Radioelectronics, Warsaw Univ. of Technology, Pl. Politechniki 1, Warsaw, Poland

o Dipartimento di Fisica e INFN, Università di Pisa, Largo Bruno Pontecorvo 3, Pisa, Italy

1 Deceased
(Submitted on 15 Mar 2012 (v1), last revised 29 Mar 2012 (this version, v3))
arXiv:1203.3433v3 [hep-ex] 29 Mar 2012

Abstract

At the end of the 2011 run, the CERN CNGS neutrino beam has been briefly operated in lower intensity mode with ≈ 10^12 p.o.t./pulse and with a proton beam structure made of four LHC-like extractions, each with a narrow width of ≈ 3 ns, separated by 524 ns. This very tightly bunched beam allowed a very accurate time-of-flight measurement of neutrinos from CERN to LNGS on an event-by-event basis. The ICARUS T600 detector (CNGS2) has collected 7 beam-associated events, consistent with the CNGS collected neutrino flux of 2.2 X 10^16 p.o.t. and in agreement with the well known characteristics of neutrino events in the LAr-TPC. The time of flight difference between the speed of light and the arriving neutrino LAr-TPC events has been analysed. The result δt=0.3±4.9(stat.)±9.0(syst.) ns is compatible with the simultaneous arrival of all events with speed equal to that of light. This is in a striking difference with the reported result of OPERA claiming that high energy neutrinos from CERN arrive at LNGS ≈ 60 ns earlier than expected from luminal speed.

General layout of the CERN-LNGS time-link for neutrino time of
flight measurement. All timing delays are shown.

(a) CC event in the chamber 1L; (b) NC event in the chamber 1R, as visible in the
LAr collection view. The actual distances of the vertex from the upstream wall of the detector
are indicated. The signal of the closest PMT spontaneously induced on the charge collecting
wires is also visible.

Time distribution in ns of the difference δt between the neutrino time of
flight expectation based on speed of light the actual measurement in the ICARUS LAr-TPC.
Events are compatible with Lorentz invariance, which requires δt <= 0.
The OPERA result is also shown as a comparison.