Non-standard interactions using the OPERA experiment
Mattias Blennow
2
Davide Meloni
1
Tommy Ohlsson
0
Francesco Terranova
3
Mattias Westerberg
0
0
Department of Theoretical Physics, School of Engineering Sciences, Royal Institute of TechnologyAlbaNova University Center
, Roslagstullsbacken 21,
106 91 Stockholm, Sweden
1
Dipartimento di Fisica,
Universit di Roma Tre and INFN Sez. di Roma Tre
, Via della Vasca Navale 84,
00146 Rome, Italy
2
Max-Planck-Institut fr Physik (Werner-Heisenberg-Institut)
, Fhringer Ring 6,
80805 Munich, Germany
3
Laboratori Nazionali di Frascati dell'INFN, Via E. Fermi 40, 00044 Frascati,
Italy
We investigate the implications of non-standard interactions on neutrino oscillations in the OPERA experiment. In particular, we study the non-standard interaction parameter . We show that the OPERA experiment has a unique opportunity to reduce the allowed region for this parameter compared with other experiments such as the MINOS experiment, mostly due to the higher neutrino energies in the CNGS beam compared to the NuMI beam. We find that OPERA is mainly sensitive to a combination of standard and non-standard parameters and that a resulting anti-resonance effect could suppress the expected number of events. Furthermore, we show that running OPERA for five years each with neutrinos and anti-neutrinos would help in resolving the degeneracy between the standard parameters and . This scenario is significantly better than the scenario with a simple doubling of the statistics by running with neutrinos for ten years.
1 Introduction
Neutrino oscillation physics has definitively entered the era
of precision measurements of the fundamental neutrino
parameters such as the neutrino mass squared differences (i.e.,
m 231 and m 221) and the leptonic mixing parameters (i.e.,
12, 13, 23, and ). In particular, the Super-Kamiokande,
SNO, KamLAND, K2K, and MINOS experiments have
given valuable information on these parameters [16].
The precision measurements open up the possibility to
investigate if neutrino flavor transitions are governed by
neutrino oscillations only or if they are, in the next-to-leading
order, a combination of neutrino oscillations and some other
new physics mechanism. However, to leading order, there
exists clear evidence that neutrino oscillations constitute the
underlying physical model for neutrino flavor transitions.
The next-to-leading order mechanism could e.g. be
nonstandard interactions (NSIs), mass varying neutrinos,
neutrino decay, neutrino decoherence etc., or some combination
thereof.
In this work, we will study NSI effects at the OPERA
experiment [7], which is an experiment that consists of
a massive lead/emulsion target (the OPERA detector)
located at LNGS in Gran Sasso, Italy, receiving its neutrino
beam, originally consisting almost exclusively of , from
CERN in Geneva, Switzerland. The baseline length is
approximately 732 km and the CNGS beam has an average
neutrino energy of E 17 GeV. The OPERA experiment is
especially designed to observe events from the
neutrino oscillation channel. In fact, no previous experiment
has investigated this channel or observed neutrinos of a
different flavor than that originally produced at the source
(although the neutral-current measurements at SNO imply that
solar e have oscillated into a different flavor). Thus, the
OPERA experiment presents a unique opportunity to study
the direct appearance of [8]. In this work, we will not try
to describe the origin of the NSIs but adopt a purely
phenomenological point of view. In particular, NSIs may modify the
production, the propagation in matter as well as the
detection of the neutrinos. We will concentrate on the simplified
scenario in which NSIs only affect the neutrino propagation.
Previously, investigations of NSIs that are of importance
for this work have been presented in the following papers.
In [9], a two-flavor neutrino analysis of the so-called
atmospheric neutrino anomaly has been performed, which
effectively bounds the NSI parameters in the sector,
and , to 0.03 0.02 and | | 0.05
at 99.73% confidence level. Although these bounds may
seem quite restrictive, it has been shown that at least the
bound on is severely weakened when considering the
full three-flavor framework (allowing to be of O(1) or
larger, depending on the values of ee and e [10]). As will
be shown later in this work, the limit that could be put by
the OPERA experiment would be insensitive to whether the
two- or three-flavor scenario is studied, simply because of
the relatively short baseline. In addition, in [11], the
authors have come to the conclusion that it would be possible
to observe NSI effects at the OPERA experiment (and the
ICARUS experiment) if O(102). Next, in [12], the
KamiokaKorea two detector setup has been investigated,
which could also give restrictions on the NSI parameters
and . Recently, in [13], a study of the OPERA experiment
(in combination with the MINOS experiment) has been
presented with the conclusion that it is (...truncated)