Non-standard interactions in propagation at the Deep Underground Neutrino Experiment

Journal of High Energy Physics, Mar 2016

We study the sensitivity of current and future long-baseline neutrino oscillation experiments to the effects of dimension six operators affecting 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 find that the Deep Underground Neutrino Experiment will significantly 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 off-diagonal NSI parameters at the level of ε ∼ \( \mathcal{O} \)(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.

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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)


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Pilar Coloma. Non-standard interactions in propagation at the Deep Underground Neutrino Experiment, Journal of High Energy Physics, 2016, pp. 16, Volume 2016, Issue 3, DOI: 10.1007/JHEP03(2016)016