Non-standard interactions in propagation at the Deep Underground Neutrino Experiment
HJE
Non-standard interactions in propagation at the Deep Underground Neutrino Experiment
Pilar Coloma 0 1
0 P. O. Box 500, Batavia, IL 60510 , U.S.A
1 Theoretical Physics Department, Fermi National Accelerator Laboratory
We study the sensitivity of current and future long-baseline neutrino oscillation experiments to the e ects of dimension six operators a ecting neutrino propagation through Earth, commonly referred to as Non-Standard Interactions (NSI). All relevant parameters entering the oscillation probabilities (standard and non-standard) are considered at once, in order to take into account possible cancellations and degeneracies between them. We nd that the Deep Underground Neutrino Experiment will signi cantly improve over current constraints for most NSI parameters. Most notably, it will be able to rule out the so-called LMA-dark solution, still compatible with current oscillation data, and will be sensitive to o -diagonal NSI parameters at the level of "
Beyond Standard Model; Neutrino Physics; CP violation
-
Underground
O(0:05
0:5). We also identify
two degeneracies among standard and non-standard parameters, which could be partially
resolved by combining T2HK and DUNE data.
The formalism of NSI in propagation
Simulation details
Sampling of the parameter space
Experimental setups
5
Conclusions
A Implementation of prior constraints
1 Introduction
2
3
4
3.1
3.2
4.1
4.2
4.3
Results
Expected sensitivities for the DUNE experiment
Degeneracies
Comparison to other facilities and to prior experimental constraints
(LcL ~ )( ~yLL) ;
where LL stands for the lepton doublet, ~ = i 2 ,
being the SM Higgs doublet, and
is the scale of New Physics (NP) up to which the e ective theory is valid to. In eq. (1.1),
cd=5 is a coe cient which depends on the high energy theory responsible for the e ective
operator at low energies. Interestingly enough, the Weinberg operator is the only SM
gauge invariant d = 5 operator which can be constructed within the SM particle content.
Furthermore, it beautifully explains the smallness of neutrino masses with respect to the
rest of fermions in the SM through the suppression with a scale of NP at high energies.
When working in an e ective theory approach, however, an in nite tower of operators
would in principle be expected to take place. The e ective Lagrangian at low energies
would be expressed as:
L
e = LSM +
cd=5
O
d=5 +
cd=6
take place via d = 6 four-fermion e ective operators,1 in a similar fashion as in the case of
Fermi's theory of weak interactions. Four-fermion operators involving neutrino elds can
be divided in two main categories:
1. Operators a ecting charged-current neutrino interactions. These include, for
instance, operators in the form (l
PL
)(q
P q0), where l stands for a charged lep
ton, P stands for one of the chirality projectors PR;L
5),
and
are lepton
2. Operators a ecting neutral-current neutrino interactions. These are operators in the
form (
PL
)(f
P f ). In this case, f stands for any SM fermion.
Operators belonging to the rst type will a ect neutrino production and detection
processes. For this type of NSI, near detectors exposed to a very intense neutrino beam would
be desired, in combination with a near detector, in order to collect a large enough event
sample [4]. Systematic uncertainties would play an important role in this case, since for
neutrino beams produced from pion decay the
ux cannot be computed precisely.2 For
recent studies on the potential of neutrino oscillation experiments to study NSI a ecting
neutrino production and detection, see e.g., refs. [7{12].
For operators a ecting neutral-current neutrino interactions the situation is very
different since these can take place coherently, leading to an enhanced e ect. Therefore,
longbaseline neutrino oscillation experiments, with L
O(500
1000) km, could potentially
place very strong constraints on NSI a ecting neutrino propagation. Moreover, unlike
atmospheric neutrino oscillation experiments [13{16], at long-baseline beam experiments the
beam is well-measured at a near detector, keeping systematic uncertainties under control.
Future long-baseline facilities, combined with a dedicated short-baseline program [17{19]
to determine neutrino cross sections precisely, expect to be able to bring systematic
uncertainties down to the percent level. Therefore, they o er the ideal benchmark to constrain
NSI in propagation. This will be the focus of the present work.
As a benchmark setup, we consider the proposed Deep Underground Neutrino
Experiment [20] (DUNE) and determine the bounds that it will be able to put on NSI a
ecting neutrino propagation through matter. For comparison, we will also show the
sensitivity reach for the current generation of long-baseline neutrino oscillation experiments,
1In principle, the largest e ects from NSI are expected to come from d = 6 operators since they appear
at low order in the expansion. However, this is might not be always the case [2]. The (...truncated)