The MOMENT to search for CP violation
JHE
The MOMENT to search for CP violation
Mattias Blennow 0 1 2 5 6 7 8
Pilar Coloma 0 1 2 3 6 7 8
Enrique Fernandez-Mart nez 0 1 2 4 6 7 8
0 P. O. Box 500, Batavia, IL 60510 , U.S.A
1 106 91 Stockholm , Sweden
2 KTH Royal Institute of Technology, Albanova University Center
3 Theoretical Physics Department, Fermi National Accelerator Laboratory
4 Departamento de F sica Teorica, Universidad Autonoma de Madrid
5 Department of Theoretical Physics, School of Engineering Sciences
6 nd a large synergy
7 Calle Nicolas Cabrera 13-15 , Cantoblanco E-28049 Madrid , Spain
8 Cantoblanco E-28049 Madrid , Spain
In this letter, we analyze for the rst time the physics reach in terms of sensitivity to leptonic CP violation of the proposed MuOn-decay MEdium baseline NeuTrino beam (MOMENT) experiment, a novel neutrino oscillation facility that would operate with neutrinos from muon decay. Apart from obtaining a su ciently intense necks to the physics reach of this experiment will be achieving a high enough suppression of the atmospheric background and, particularly, attaining a su cient level of charge identi - cation. We thus present our results as a function of these two factors. As for the detector, we consider a very massive Gd-doped Water Cherenkov detector. We nd that MOMENT will be competitive with other currently planned future oscillation experiments if a charge identi cation of at least 80 % can be achieved at the same time that the atmospheric background can be suppressed by at least a factor of ten. We also of MOMENT with the current generation of neutrino oscillation experiments, T2K and NOvA, which signi cantly enhances its nal sensitivity.
CP violation; Neutrino Physics
1 Introduction
2 Implementation 3 Results and conclusions
1
Introduction
PMNS matrix element Ue3 provided by accelerator and reactor neutrino experiments [11{
15], it is plausible that CP-violation in the lepton sector may be found in the not so distant
future. The current hints of maximal lepton CP-violation [16{18] provide further indication
that this discovery may be right around the corner.
In the next generation of neutrino oscillation experiments, the front runners in the
hunt for leptonic CP-violation are the proposed Deep Underground Neutrino Experiment
(DUNE) [19] and the Tokai to Hyper-Kamiokande (T2HK) experiment [20]. Both of them
propose to use conventional accelerator neutrino beams from pion decay. In contrast,
the MuOn-decay MEdium baseline NeuTrino beam facility (MOMENT) [21] proposes to
observe a neutrino beam produced from decaying muons at relatively low energies. By
{ 1 {
using this type of beam, some of the technical di culties related to the construction of
the more futuristic neutrino factory could be avoided [22{24]. The aim of this letter is to
study the capabilities of the MOMENT experiment and put it into context in the global
experimental e ort in neutrino physics.
2
Implementation
The MOMENT design is still not fully developed and is therefore subject to large
uncertainties. As a rst step towards studying its physics potential and the requirements
it would need to meet to reach a competitive performance with respect to other future
neutrino oscillation experiments, some assumptions regarding both the beam and
detector performance have to be made. However, in our analysis we leave the most relevant
parameters free in order to explore their impact on the expected sensitivities.
The MOMENT facility would employ a proton linac (either continuous or pulsed) of
1.5 GeV, as well as a 10 mA proton driver. The aim of its design is to deliver a beam of
extremely high power, up to 15 MW. Reaching such a high intensity already represents a
major technological challenge. In addition, if such a high intensity is eventually achieved,
a suitable target that is able to withstand it would need to be identi ed. Further issues
have been pointed out related to the focusing system for the pions, heat mitigation and
the radiation levels at the target station. These points are already being investigated, and
we refer the interested reader to ref. [21]. In this work we will start from the muon and
electron neutrino
uxes presented in refs. [21, 25] (at 150 km from the source), and we will
assume that alternating between muon polarities with a similar ux intensity is possible.
In order to assess the importance of achieving the demanding goal of 15 MW, we will
also show how our results scale with the total luminosity of the experiment. The neutrino
uxes used in this work have their maximum at energies around 150 MeV with maximum
intensity of
109 MeV 1 m 2 year 1, and have been taken from ref. [25]. Five years of
running time per polarity are assumed.
In principle, the MOMENT setup would allow the study of the e !
e
,
e !
and
!
oscillation channels as well as their corresponding CP-conjugate
partners. However, since the original ux is composed of
and e from
decay, both
good
avour and charge identi cation capabilities are need (...truncated)