DUNE sensitivities to the mixing between sterile and tau neutrinos

Journal of High Energy Physics, Jul 2018

Abstract Light sterile neutrinos can be probed in a number of ways, including electroweak decays, cosmology and neutrino oscillation experiments. At long-baseline experiments, the neutral-current data is directly sensitive to the presence of light sterile neutrinos: once the active neutrinos have oscillated into a sterile state, a depletion in the neutral-current data sample is expected since they do not interact with the Z boson. This channel offers a direct avenue to probe the mixing between a sterile neutrino and the tau neutrino, which is currently only weakly constrained by current data from SuperK, IceCube and NOvA, however, these constrains will continue to improve as more data is collected by these experiments. In this work, we study the potential of the DUNE experiment to constrain the mixing angle which parametrizes this mixing, θ34, through the observation of neutral-current events at the far detector. We find that DUNE will be able to improve significantly over current constraints thanks to its large statistics and excellent discrimination between neutral- and charged-current events.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

https://link.springer.com/content/pdf/10.1007%2FJHEP07%282018%29079.pdf

DUNE sensitivities to the mixing between sterile and tau neutrinos

Received: July DUNE sensitivities to the mixing between sterile and Pilar Coloma 0 1 2 4 David V. Forero 0 1 2 3 Stephen J. Parke 0 1 2 4 0 Blacksburg , VA 24061 , U.S.A 1 13083-859 , Campinas, SP , Brazil 2 P. O. Box 500, Batavia, IL 60510 , U.S.A 3 Center for Neutrino Physics , Virginia Tech , USA 4 Theoretical Physics Department, Fermi National Accelerator Laboratory Light sterile neutrinos can be probed in a number of ways, including electroweak decays, cosmology and neutrino oscillation experiments. At long-baseline experiments, the neutral-current data is directly sensitive to the presence of light sterile neutrinos: once the active neutrinos have oscillated into a sterile state, a depletion in the neutral-current data sample is expected since they do not interact with the Z boson. This channel o ers a direct avenue to probe the mixing between a sterile neutrino and the tau neutrino, which is currently only weakly constrained by current data from SuperK, IceCube and NOvA, however, these constrains will continue to improve as more data is collected by these experiments. In this work, we study the potential of the DUNE experiment to constrain the mixing angle which parametrizes this mixing, 34, through the observation of neutral-current events at the far detector. We nd that DUNE will be able to improve signi cantly over current constraints thanks to its large statistics and excellent discrimination between neutral- and charged-current events. Beyond Standard Model; Neutrino Physics; CP violation Oscillation probabilities in the 3 + 1 framework Rejection power for the three-family hypothesis, for 24; 34 6= 0 Expected allowed regions in the 24 Summary and conclusions A Complete expressions for the relevant mixing matrix elements in our 1 Introduction 2 3 4 Simulation Results 4.1 4.2 4.3 parametrization B 2-function 1 Introduction In the past decade, a tremendous experimental e ort has been carried out in order to constrain scenarios with additional neutrinos with masses below the electroweak scale. LEP data places severe constraints on the invisible decay of the Z. Hence, if there are additional neutrinos below the electroweak scale, they cannot couple to the Standard Model weak bosons (i.e., they should be sterile). Light sterile neutrinos can lead to observable phenomena in a number of electroweak processes through their impact on the unitarity of the leptonic mixing matrix, including meson decays, muon decay, neutrinoless double beta decay and charged lepton avor violating transitions (see e.g., refs. [1, 2] for recent global ts using these observables). Nevertheless, if their masses are light enough so that they are kinematically accessible in these processes, unitarity is e ectively restored at low energies and the bounds from electroweak processes fade away. In this case the best limits are derived from oscillation data [3{8], see e.g., refs. [ 9, 10 ] for a detailed discussion of these constraints. In recent years, the eV-scale has recently been put on the spot due to a set of experimental anomalies independently reported in LSND [11], MiniBooNE [12, 13], reactor [14, 15] and Gallium experiments [16]. The current and next generation of oscillation experiments will attempt to refute or con rm these hints. The Icecube experiment has recently put impressive limits on the mixing between sterile neutrinos and muon neutrinos U 4 [17, 18], { 1 { to constrain the cross-product jUe4j2jU 4j2 [23]. Conversely, placing equally competitive limits on the mixing with tau neutrinos is a much more di cult task, due to the technical challenges associated to the production and detection of a beam. Indirect constraints on the mixing with can be derived from the observation of matter e ects in atmospheric neutrino oscillations. For example, the IceCube experiment 90% CL) for an active-sterile mass splitting above 0:1 eV2 [4].1 A non-zero have set the limit jU 4j2 < 0:15 (at 90% CL) for an active-sterile mass splitting equal to 1 eV2 [18] while the Super-Kamiokande experiment have set the bound jU 4j2 < 0:18 (at 24 and 34 active-sterile mixing produces striking signatures in the zenith and energy distribution of cascade events in IceCube DeepCore, and after some years of data taking it is possible to probe the 34 parameter space [25]. On the other hand, a more direct test for the mixing between sterile neutrinos and tau neutrinos can be performed using long-baseline experiments. At long-baseline experiments most of the initial ux has oscillated into tau neutrinos by the time it reaches the far detector, thanks to by the atmospheric mass-squared splitting. The OPERA experiment has constrained the impact of sterile neutrinos on this oscillation channel, using charged-current events at the far detector, setting the bound 4jU 4j2jU 4j2 < 0:116 (at 90% CL) for an active-sterile masssquared splitting above 0:1 eV2 [26]. However, their results are severely limited by statistics, since the charged-current cross section is still low at multi-GeV neutrino energies. Alternatively, the mixing between sterile neutrinos and tau neutrinos can be tested at long-baseline experiments searching for a depletion in the neutral-current event rates at the far detector. In fact, both the MINOS and the NOvA experiments have provided competitive constraints using this approach [27, 28]. Future long-baseline experiments, with larger detectors, more powerful beams and a better control of systematic uncertainties, may be able to push these limits even further. In this work, we focus on the potential of the DUNE experiment [29]. Previous studies of sterile neutrino oscillations using the DUNE far detector data can be found, e.g., in refs. [9, 30{36].2 However, to the best of our knowledge the neutral-current data sample has not been considered in any of these works. The liquid Argon detector technology has excellent particle identi cation capabilities and therefore a very good discrimination power between charged- and neutral-current events. In addition, the statistics collected at DUNE will exceed considerably (by a rough order of magnitude) the number of events collected at MINOS or NOvA. Thus, DUNE o ers an excellent benchmark to conduct a search for sterile neutrino mixing using neutral-current data. ! oscillations driven 1An important constraint on the tau-sterile mixing angle 34 has been obtained by combining IceCube DeepCore data [18] and short baseline data in ref. [24]. However, the constraint is given for a speci c value of the sterile mass squared di erence larger than 1 eV2. 2For a sensitivity study using the DUNE near detector to probe sterile neutrino oscillations at m421 1eV2 we refer the reader to ref. [37]. { 2 { HJEP07(218)9 Although current hints of sterile-active neutrino mixing with e and occurs for a m2 of 0.1 eV2, in this paper we consider a broader range of m2 's similar to what Daya Bay has performed for the e disappearance search for sterile neutrinos, see ref. [19]. If a sterile neutrino only mixes with , then searches using e and disappearance as well as e appearance in a beam will not constrain such sterile-tau mixing. The manuscript is organized as follows. In section 2 we derive the oscillation probabilities in the ! s and ! s oscillation channels at the far detector of long-baseline experiments, and discuss the di erent limits of interest depending on the active-sterile mass-squared splitting. Section 3 summarizes the main features of the DUNE experiment and the details relevant to our numerical simulations. Our results are presented in section 4, and in section 5 we summarize and draw our conclusions. Some useful expressions for the elements of the mixing matrix using our parametrization can be found in appendix A. 2 Oscillation probabilities in the 3 + 1 framework In this section we derive approximate expressions for the oscillation probabilities, which will be useful in understanding the results of our numerical simulations later on. The mixing matrix U that changes from the avor to the mass basis in the 3 + 1 neutrino framework is a 4 4 unitary matrix: = U i i ; where e; ; ; s and i 1; 2; 3; 4. In this work we are interested in the e ect of oscillations into sterile states on the event rates measured at the DUNE far detector. Assuming that no oscillations have taken place at the near detector, this can be done searching for a depletion in the number of neutral-current (NC) events at the far detector with respect to the prediction obtained using near detector data. For a perfect beam of muon neutrinos with ux (i.e., assuming no beam contamination from other neutrino avors), the number of NC events at the far detector can be expressed as: NNC = N NeC + NNC + NNC = NC fP ( NC 1 f = and is therefore sensitive to oscillations in the ! s channel. Here, NC is the neutralcurrent cross section for the active neutrinos, which is independent of the neutrino avor. In the absence of a sterile neutrino, the NC event rates should be the same at the far and near detectors up to a known normalization factor coming from the di erent distance, detector mass, e ciency, and the di erent geometric acceptance of the beam at the two sites. In fact, the combined t between near and far detector data should provide a very e cient cancellation of systematic errors associated to the ux and cross section in this channel [28]. In addition to the standard solar and atmospheric mass-squared di erences, in the 3+1 framework the oscillation probabilities depend on three new splittings with k = 1; 2; 3. Given the values of the neutrino energy and distance corresponding to the far detector at DUNE, for illustration purposes we can e ectively neglect the solar m24k m24 m2k, { 3 { mass splitting and focus on the e ects of the oscillation due to the atmospheric and the sterile mass-squared splittings.3 Under the approximation probability in the ! s channel is given (in vacuum) by: 21 31; 41, the oscillation P s P ( ! s) = 4jU 4j2jUs4j2 sin2 41 + 4jU 3j2jUs3j2 sin2 31 + 8 Re U 4Us4U 3Us3 cos 43 sin 41 sin 31 + 8 Im U 4Us4U 3Us3 sin 43 sin 41 sin 31; where we have de ned ij mi2j L=4E. The probability in eq. (2.2) is completely general, but does not allow to see the number of independent parameters which enter the oscillation probability. A 4 4 unitary matrix U can be parametrized in terms of six mixing angles and three Dirac CP-violating phases.4 In the following, we choose to parametrize it as the product of the following consecutive rotations: U = O34V24V14O23V13O12: Here, Oij denotes a real rotation with an angle ij a ecting the i and j sub-block of the mixing matrix, while Vij denotes a similar rotation but this time including a complex phase. For example: 0 c24 0 0 cos ij . In this notation, i4 are the new mixing angles with the fourth state, and 14; 24 are the two new CP-violating phases. In this parametrization, the complex phase associated with the V13 rotation corresponds to the standard CP-violating phase in three-families, 13 CP , and the 3 3 sub-block of the matrix shows only small deviations from a unitary matrix, which at leading order are proportional to sj24 and therefore within current bounds [8]. For simplicity, from now on we consider 14 = 0, which is a valid approximation given the strong constraints set by reactor experiments in the range of work [23]. In this case there is no sensitivity to the 14 phase, which disappears from the mixing matrix, and the relevant elements of the mixing matrix read m241 considered in this 3In our numerical simulations the full Hamiltonian is diagonalized to extract the oscillation probabilities 4If neutrinos are Majorana, additional CP-phases enter the matrix. However, neutrino oscillations are { 4 { see eq. (A.1). Then we can rewrite the ! s oscillation probability, eq. (2.2), as where the dependence with the new CP-violating phase 24 phase is now evident. Depending on the value of the new mass-squared splitting, can be considered for the probability in eq. (2.6): m241, the following three limiting cases 1. The oscillations due to the active-sterile mass-squared splitting have not developed distance to the far detector (i.e., 41 31): P s = 4 U 4Us4 + U 3Us3 2 sin2 31 = 2c143s223c224 2c223s324 + sin 2 23 sin 2 34s24 cos 24 + 2s223s224c324 sin2 31 : 2. The oscillation maximum due to the active-sterile mass-squared splitting matches the = 4 jU 4j2jUs4j2 + jU 3j2jUs3j2 + 2 Re[U 4Us4U 3Us3] sin2 31 = c413 sin2 2 23c224s324 + c324 sin2 2 24(1 c213s223)2 c213c24 sin 2 23 sin 2 24 sin 2 34(1 c213s223) cos 24 sin2 0 there is a signi cant cancellation in the probability. This will be discussed in more detail later in this section. 3. The oscillations due to the active-sterile mass-splitting are already averaged-out at the far detector5 (i.e., 41 31): P s = 2 jU 4j2jUs4j2 + 4 jU 3j2jUs3j2 + Re[U 4Us4U 3Us3] sin2 31 + 2 Im[U 4Us4U 3Us3] sin 2 31 = 21 c324 sin2 2 24 41 c123c24 sin 2 23 sin 2 24 sin 2 34 sin 24 sin 2 31: 5A similar expression in this limit, but assuming a real mixing matrix, can be found in ref. [38]. Δm241=0.002 eV2 Δm241=0.004 eV2 Δm241=Δm231 5 10 spond to di erent values of the new CP-violating phase 24, while the di erent lines shown in each panel correspond to di erent values of the active-sterile mass splitting end. The rest of the oscillation parameters have been xed to: 0:5 ; sin2 2 13 = 0:084 ; and sin2 24 = sin2 34 = 0:1. m231 = 2:48 10 3 eV2 ; sin2 23 = m241, as indicated in the leg As mentioned above, a destructive interference between the standard and non-standard contributions to the oscillation amplitude is possible for certain values of the active-sterile mixing parameters and, in particular, for certain values of the CP phase 24. This is shown in gure 1 for di erent values of m241 around the atmospheric scale, when the oscillation probability simpli es to eq. (2.8). The solid lines in all panels have been obtained for m241 = m231: notice that a cancellation of the oscillation amplitude takes place in this case for 24 = 0, as shown in the left panel in gure 1. In this case, the contribution from the interference (last term in eq. (2.8)) is negative and cancels almost exactly the two other contributions to the oscillation probability. In fact, it is straightforward to show that, in the limit c13 = c24 = c34 = 1, the amplitude of the oscillation is proportional to c223js24c23 s34s23ei 24 j2, which vanishes exactly if 24 = 0 and s24c23 = s34s23. This cancellation is only partial (or negligible) for other values of the CP phase, as expected, and this can be seen from the middle and right panels in the gure. For other values of the active-sterile mass splitting the oscillation pattern is more complex, as shown by the dotted blue and dashed yellow lines in gure 1. In the most general case, the dependence of the probability with the energy becomes non-trivial due to the interference of di erent terms oscillating at di erent frequencies. Moreover, as we will see in section 4 the cancellation in the probability can also be severe in the limit m241 m231. Given the strong limits that have been set on the 24 angle by the oscillation experiments looking for oscillations involving a sterile neutrino in the eV scale, it is worth to address explicitly the case when 24 ! 0. Under this assumption, the probability simpli es considerably with respect to the expression in eq. (2.6): P s( 24 ! 0) = c143 sin2 2 23s324 sin2 31: (2.10) In contrast with eq. (2.6), in this case there is no sensitivity to 24 and, most importantly, there is no dependence with the sterile mass-squared splitting. The oscillations in this case are solely driven by the atmospheric mass-squared splitting, and the size of the e ect { 6 { parameters goes as c413 sin2 2 23 O(1). is directly proportional to s234. Moreover, the dependence with the standard oscillation Finally, it is worth to mention that matter e ects will modify the oscillation probability in eq. (2.6). We have checked that the size of these modi cations is relatively small and, therefore, the vacuum probabilities are precise enough to understand the behavior of the numerical simulations in the following sections. However, in our numerical analysis, matter e ects have been properly included using a constant matter density of 2:96 g cm 3 : 3 In contrast to usual analyses searching for signals of sterile neutrino oscillations at short distances, in this work we want to take advantage of the capabilities of the DUNE far detector, located at a distance of L = 1300 km from the source. In particular, we focus on the potential of NC measurements to discriminate between the 3- avor and 4- avor scenarios. To this end, we rely on the excellent capabilities of the DUNE far detector to discriminate between charged-current (CC) and NC events. All the simulations in the current work have been performed using a modi ed version of the GLoBES [39, 40] library which includes a new implementation of systematic errors as described in ref. [41]. The neutrino oscillation probabilities in a 3+1 scenario have been implemented using the new physics engine available from ref. [42]. In our simulation of the signal, we have computed separately the contributions to the total number of events coming from e , and NC interactions at the detector. For simplicity, we have assumed a 90% at e ciency as a function of the reconstructed visible energy. The experimental observable for a NC event is a hadronic shower with a certain visible energy (energy deposited in the detector in the form of a track and scintillation light). The correspondence between a given incident neutrino energy and the amount of visible energy deposited in the detector has to be obtained from the simulation of neutrino interactions and detector reconstruction of the particles produced in the nal state. To this end, we use the migration matrices provided by the authors of ref. [43], which were obtained using the LArSoft simulation software [ 44 ] accounting for the far detector geometry, neutrino-argon interactions and propagation of the nal state particles in the detector active volume. The authors of ref. [43] used bins in visible energy of 50 MeV for the reconstructed energy of the hadron shower, as opposed to the DUNE CDR studies where wider bins of 125 MeV were considered [29]. In the present work we have considered two sets of matrices: the original set provided by the authors of ref. [43], with 50 MeV bins, and a (more conservative) rebinned version of these matrices where the bin size was increased to 250 MeV. We performed our simulations for the two options (with 50 MeV bins and 250 MeV bins) and found similar results for the two sets of matrices. Therefore, in the following we will adopt the more conservative 250 MeV bin size as our default con guration. The main backgrounds for this search would be e and CC events that might be mis-identi ed as NC events. We have assumed that the background rejection e ciency for CC events is at the level of 90%. However, this is probably a conservative estimate: for instance, muons leave long tracks in liquid Argon (LAr) that are di cult to misidentify { 7 { HJEP07(218)9 mode mode (NNeC + NNC + NNC ) 6489 2901 Background NCeC 129 22 NCC 751 301 NCC 140 39 8 GeV at the DUNE far detector. The number of events is shown for the signal and background contributions separately. This corresponds to 7 yrs of data taking (equally split between neutrino and antineutrino running modes) with a 40 kton detector and 1.07 MW beam power, yielding a accounted for. In the case of NCC , the number of events already includes the branching ratio for hadronic decays. Usual oscillations (in the three-family scenario) have been considered in the computation of the backgrounds, setting 23 = 42 and the rest of the oscillation parameters in agreement with their current best- t values. as NC events, except when they have very low energies or are not completely contained in the detector. On the other hand, the active neutrino avors would be a ected by standard oscillations. Consequently, the number of CC events would be largely suppressed since most of the initial muon neutrinos have oscillated to tau neutrinos by the time they reach the detector. Given the energetic neutrino ux at DUNE, some of the oscillated ux will interact at the detector via CC, producing leptons. In most of the cases ( 65%), the decays hadronically producing a shower: these events constitute an irreducible background and consequently no rejection e ciency has been assumed in this case. We have assumed a Gaussian energy resolution function for the and e background contributions, following the values derived in ref. [43] from LArSoft simulations, while the hadronic showers produced from hadronic tau decays have been smeared using the same migration matrices as for the NC signal. The expected total number of signal and background events is summarized in table 1, where the di erent background contributions are shown separately for clarity. As can be seen from this table, the largest background contribution comes from CC events misidenti ed as NC, due to the large ux available at the far detector, while the contributions coming from e and CC events are much smaller and approximately of equal size. In all cases, both signal and backgrounds receive contributions from right- and wrong-sign neutrino events due to the intrinsic contamination of the beam. The number of events has been computed for visible energies between 0.5 GeV and 8 GeV, which is the region used in our analysis, using the beam con guration with 80 GeV protons as in ref. [45]. Additional experimental details for the DUNE setup considered in this work can be found in refs. [29, 45]. The expected NC event distributions are shown in gure 2, as a function of the (reconstructed) visible energy, for the three-family scenario (white histogram) and for the case when there is a sizable mixing angle with the sterile neutrino (blue/light gray histogram). As expected, a depletion in the number of events can be observed in the 3 + 1 case with { 8 { Erec [GeV] visible energy, after e ciencies and detector reconstruction. The white histogram shows the expected number of NC events in the 3-family standard scenario, while the blue (light gray) histogram shows the expected number of NC events for sin2 34 = 0:1, 14 = 24 = 0. The expected distribution for background events (CC mis-identi ed as NC) is given by the green (dark gray) histogram. respect to the three-family scenario. Moreover, the events pile up at low energies due to the energy carried away by the outgoing neutrino in the nal state. One can also see that the energy distribution of the background (shown by the green/dark gray histogram) is dictated by the standard oscillations su ered by the active neutrinos as they propagate to the far detector, which is well-known. In this case, all particles in the nal state would be observed, and there is practically no pile-up at low energies. Due to this, the sensitiv! ity to oscillations in the s channel is enhanced when some energy information is included in the t, as we will see in the next section. This is exploited in our numerical 2 in the visible (deposited) energy in the detector, with analysis implementing a binned a 2 function de ned in eq. (B.1). The e ect of systematic uncertainties is accounted for through the addition of pullterms to the 2, as speci ed in the appendix B. In addition to an overall normalization uncertainty for the signal and background (which is bin-to-bin correlated), a shape uncertainty for the signal (bin-to-bin uncorrelated) has been included to account for possible systematic uncertainties related to the shape of the event distributions. Moreover, all nuisance parameters are taken to be uncorrelated between the neutrino and antineutrino channels as well as between the di erent contributions to the signal and/or background events. Unless otherwise stated, the nal 2 is obtained after marginalization over the nuisance parameters and the relevant standard oscillation parameters (sin2 2 23; sin2 2 13; m231) within current experimental uncertainties [46{48]. Speci cally, we consider the following Gaussian priors: (sin2 2 13) = 0:005, (sin2 2 23) = 0:05 and ( m231)= m231 = 0:04. Unless otherwise speci ed, we have assumed a conservative 10% Gaussian prior for all nuisance 2 parameters, included as pull-terms in the . In practice, however, the cancellation of { 9 { systematic errors in the NC channels is expected to be extremely e cient, since the near detector can be used to measure the same convolution of the ux and cross section as in the far detector. This contrasts with oscillation measurements in appearance mode ( using CC data, where the initial and nal neutrino ux spectrum (and avor) di er due to the impact of standard oscillations, making the cancellation of systematic uncertainties extremely challenging.6 In spite of these di culties, the DUNE collaboration expects to ! ) reach a precision at the percent level in the ! e and ! e appearance channels. In view of this, we expect the 5%{10% values considered in this work for the NC sample to be conservative. Before concluding this section, let us comment on the relevance of the near detector data and its possible impact on the t. In this work, we have not simulated the near detector explicitly: its design is still undecided and its expected performance is therefore unclear yet. A detailed simulation of the near-far detector data combination is beyond the scope of this work and can ultimately be performed only by the experimental collaboration. In this work, instead, we have assumed that the oscillations due to the new state have not developed yet at the near detector. For neutrino energies in the region around 2-3 GeV, and for a near detector located at a distance of L O(500) m, this is a valid approximation as long as m241 < 1 eV2. Under this assumption, the near detector measurements will provide a clean determination of the convolution of the NC cross section and the muon neutrino ux, which can then be extrapolated to the far detector with a small uncertainty. At this point, it should be mentioned that our assumed prior uncertainties for the systematic errors in the t would correspond to the values used for the analysis of the far detector event rates. Thus, they correspond to estimates on the size of the nal systematic errors that have to be propagated to the far detector, once the near detector data has already been accounted for. Finally, it should also be stressed that in the case that 14 = 24 = 0 there would be no e ect on the near detector data regardless of the new mass-squared splitting. The reason is that, as it was shown in eq. (2.10), the dependence with the oscillation probabilities: this guarantees no e ect at the near detector, while at the far detector data the oscillation would be driven by the atmospheric scale. Thus, in this case m241 drops from the e ect in the oscillation would be observable for large enough 34. 4 Results In this section we show our numerical results for the expected sensitivities to the new mixing parameters in the di erent scenarios discussed in section 2. By the time DUNE starts taking data the constraints on the sterile mixing angles 14 and 24 might be very tight. Nevertheless DUNE is also sensitive to the 34 sterile mixing angle, which is currently the less constrained among the three sterile-active mixing angles. Therefore, we initially consider the simpler case where two of the new mixing angles xed to zero, 14 = 24 = 0 and study the sensitivity of the DUNE experiment to 34. Next we proceed to turn on the mixing angle 24 and determine for which values of 24 m241 the three-family hypothesis 6For a recent review of the challenges that long-baseline experiments have to meet regarding systematic uncertainties see ref. [49]. 2 90% C.L shape = norm = 5% shape = norm = 10% norm = 5%, Rate only norm = 10%, Rate only 14 12 10 8 6 4 2 0 lines correspond to di erent assumptions of systematical uncertainties, see text for details. Right panel: 34-discovery reach analysis where 4- avor event rates were calculated in `data' and t, with all the 4- avor parameters xed to the values in the plot, except for 34. Also, as shown in the plot, we xed the systematical errors to 5%. The shaded region is disfavored at 90% C.L. from Super-Kamiokande atmospheric data [4] and whose limit on jU 4j2 < 0:15 (at 90% CL) translates into the constraint sin2 34 < 0:15, for 14 = 24 = 0. The horizontal dotted line indicates the value of the 2 corresponding to 90% C.L. for 1 d.o.f.. could be rejected. We nalize this section by showing the expected limits that could be derived simultaneously on the two mixing angles 24 and 34, for di erent values of the active-sterile mass-squared splitting. 4.1 Sensitivity to 34, for 24 = 0 Under the assumption 24 = 14 = 0, the expression for the vacuum sterile neutrino appearance probability is given by eq. (2.10) and does not depend on any of the new oscillation frequencies induced by the sterile, nor any of the CP-violating phases. An interesting question to ask in this case is if DUNE will be able to improve over current constraints on 34, assuming that the experiment will measure event distributions in agreement with the expectation in the three-family scenario. In this case, the \observed" event distributions are simulated setting all i4 = 0, and are then tted using increasing values of 34. The sensitivity to 34 is shown in the left panel of gure 3. As seen in the gure, our results show a considerable dependence on the size and implementation of systematic errors. Assuming a (conservative) 10% systematic error on both normalization ( norm) and shape ( shape), we nd that DUNE will be sensitive down to values of sin2 34 0:12, at 90% C.L. (1 d.o.f.). For comparison we also show the limit on this mixing angle obtained from atmospheric neutrino data collected by the Super-Kamiokande (SK) collaboration [4], for m241 > 0:1 eV2. If prior uncertainties could be reduced to the 5% level for both normalization and shape errors, we nd that DUNE would be able to improve over the SK constraint by more than a factor of two. It should be stressed that the DUNE constraint would be valid for any value of m241, as long as 24; 14 ' 0. In the next subsections we will study in detail the phenomenology in case 24 6= 0. The lines labeled as \Rate only" in the left panel of gure 3 do not include a binned 2 and only consider the total event rates in the computation of the 2 . The change in sensitivity can be appreciated from the comparison between the dashed pink and dotdashed red lines, for 10% systematic errors (or between the dot-dot-dashed green and solid blue lines, for 5% systematic errors). As can be seen, the inclusion of energy information leads to a noticeable improvement in the results. Therefore, in the rest of this section we will only consider a binned 2, using equally-sized bins in visible energy, as described in section 3. Finally, we comment on the analysis shown in the right panel of gure 3. Di erent to the analysis shown in the left panel, in the right panel we performed a discovery reach analysis for 34 taking all systematical errors at the 5% level. In this case, we assume that the experiment will measure event distributions in agreement with the expectation in the four-family scenario. In order to quantify the impact of also having a nonzero 14 and 24, for simplicity, the four- avor parameters where xed to their `true' values (except for 34) with the values in the plot labels. In this case (for 14 6= 0 or 24 6= 0) there is a dependence with the sterile mass squared di erence, and we have xed its value to which is one of the values considered in our results in gure 5. For are therefore in the regime where the sterile oscillation is averaged-out at the far detector, in relation to eq. (2.9). In fact, is in this regime where constraints in the 24 34 plane are reported by di erent the collaborations (as will be addressed in section 4.3). It is then worth to mention that 14 is tightly constrained by reactor experiments for the considered [19] and therefore its impact (even for 24 6= 0) is marginal, as shown in the right panel of gure 3. Thus, since by the time DUNE will be running smaller values of m241 14 and 24 are expected, the case when 14 24 0 is of particular relevance. In this last case DUNE, with the considered con guration, will produce a `indication' of a nonzero 34 (i.e. if it happens to be as large as 18 ) with a signi cance of 2 for the assumed systematical errors. Rejection power for the three-family hypothesis, for 24; 34 6= 0 The scenario where 24 6= 0 leads to a more interesting phenomenology, since in this case the oscillation probability also depends on the active-sterile mass-squared splitting. In this case, assuming as our true hypothesis a 3+1 with nonzero 34 and 24, it is relevant to ask if the experiment would be able to reject the three-family hypothesis. This is shown in gure 4, as a function of the possible true values of m241 and sin2 24. The true value of 34 is set to be nonzero, while 14 = 0 is assumed for simplicity. In all panels, the expected events distributions are computed using the indicated values as true input values. The obtained \observed" event distributions are then compared to the expected result in the three-family scenario, i.e., in absence of a sterile neutrino. The contours indicate the sets of true values ( 24, m241) for which the three-family hypothesis would be successfully rejected at 90% C.L.. The di erent panels in gure 4 show the dependence of our results 10 2 10% syst. 10 2 sin2 2410 1 100 m241 and sin2 24. The true value of 34 has been set to a non-zero value in all cases, as indicated in the labels, while 14 = 0 for simplicity. The contours indicate the sets of true values ( 24, m241) for which the three-family hypothesis would be successfully rejected at 90% C.L.. In other words, they indicate the fraction of parameter space where the SM hypothesis (namely, the point i4 = 0) would be disfavored with a 2 > 2:71. Left panel: dependence of the results with the true value of 24. Central panel: dependence of the results with the true value of sin2 34. Right panel: dependence of the results with the assumed priors for the systematic uncertainties. with respect to di erent parameters: the true value of 24 (left panel), the true value of 34 (central panel); and the assumed priors for the systematic uncertainties (right panel). As explained in section 2, if both 24 and 34 are di erent from zero, the oscillation probability P s also depends on the value of the CP phase 24. Such dependence can be appreciated by comparing the three lines shown in the left panel in gure 4, corresponding to di erent true values of 24. The same true value of 34 and the same implementation of systematic uncertainties have been assumed for all lines (indicated by the top label). gure 1 (see also eq. (2.8)), for values of interference between the di erent contributions to the oscillation amplitude, depending on the value of 24. For values of m231, this leads to a decreased sensitivity in this region of the parameter space for 24 = 0 with respect to the results obtained for 24 = . The interference has the opposite e ect in the region m241 m231: for negative values of cos 24 the second term in eq. (2.7) is negative and suppresses the probability, leading to worse results for 24 = . In fact, it can be easily shown that, in the limit 23 = =4, c13 = 1 and at the rst oscillation maximum (sin2 2 eq. (2.7) approximates to 31 = 1) the oscillation probability in P s c224(s324 + 2s24s34c34 cos + s224c234) ; (4.1) where the e ect of the interference term can be easily appreciated. Conversely, in the limit where the new frequency is averaged-out ( m241 m231) the results show a very mild dependence with the value of 24. This can be easily explained from the expression in eq. (2.9), which shows two terms that depend on the value of 24: the rst one is directly proportional to (c213s23 2 1=2) ' O( 23 s213=2), where 23 23 =4, and is therefore very suppressed; while the second term is proportional to sin 2 31 and it is completely o -peak at the rst oscillation maximum. In fact, in the same limit ( 23 = =4, c123 = 1) and at the rst oscillation maximum it is easy to show that the term proportional to cos 24 in the oscillation probability in eq. (2.9) is additionally suppressed with cos 2 23, which is small for 23 near maximal mixing. The central panel in gure 4 shows the dependence of the results with the true value of 34. In this case, all priors for the systematic uncertainties are set at the 10% and we have xed 24 = 0. As shown in the gure, in the region where m241 m231 there is a strong dependence of the results with the true value of 34, while the contours do not show large variations for larger mass splittings. This behavior can again be easily traced back to the approximate oscillation probabilities in section 2. Finally, the right panel in gure 4 shows the dependence of the results with the assumed priors for the systematic uncertainties. In this panel, the true values of 24 and 34 have been set as indicated in the top label. The solid line uses our default implementation for the systematic uncertainties, where all priors are set to 10% for both the shape and normalization and for both signal and background. The dot-dashed line, on the other hand, shows the room for improvement if all prior uncertainties can be reduced down to 5%. As can be seen from the gure, the improvement is dramatic and leads to a successful rejection of the three-family hypothesis in practically all the parameter space, with the sole exception of the region around m231 (which is very di cult to reject, since this is the region where signi cant cancellations can take place for 24 = 0). 4.3 Expected allowed regions in the 24 34 parameter space If the observed event distributions show an agreement with the three-family expectation, one would proceed to derive a limit on the mixing angles 24 and 34. However, as we saw in section 2 the oscillation probabilities show a large dependence with the new CP-violating phase 24, and strong cancellations between the di erent contributions may occur. The e ect of the cancellations is much more severe in the limit m241 ! 0 than for larger values of the active-sterile mass splitting and, therefore, we expect very di erent results as a function of this parameter. Figure 5 shows the expected allowed regions in the 24 and 34 plane if the observed event distributions are found to be in agreement with the three-family hypothesis. In this case, the \observed" event distributions are simulated assuming the three-family hypothesis, and tted in a 3+1 scenario. The value of the 2 function, for a given pair of test values 24 34, is obtained after minimization over the new CP-violating phase 24 and over all nuisance parameters. As for the mass splitting m241, it has been kept xed during the t to the test value indicated in each panel to show the di erence in the results. For simplicity, we have also kept all the standard parameters xed during the minimization procedure; however, minimization over the standard parameters is not expected to a ect signi cantly the results shown here. gure 5, the resulting allowed regions are very di erent if the results are tested using m241 m231 or a m241 in the averaged-out regime. In the former case, a strong cancellation in the oscillation probability can always be achieved setting the value of 24 , as outlined in section 2 and section 4.2. Therefore, in this case it is not possible to disfavor large values of the new mixing angles. Only if the two mixing angles have very di erent values (e.g., in the region 24 ! 0; 34 & 25 ) the interference term would not be 10% 5 % sy s y 10% sys. DUNE 15 34( ) correspond to the expected con dence regions allowed at 90% C.L. (2 d.o.f.), for a simulation assuming i4 = 0 as true input values. The lines labeled as \10% sys" (\5% sys") have been obtained assuming 10% (5%) prior uncertainties for the signal (both shape and normalization) and 10% for the background (normalization only). For comparison, the right panel shows the latest results from the NOvA experiment from a NC search [28] (gray region), and from atmospheric data from the Super-Kamiokande experiment [4] and IceCube DeepCore data [18] (darker gray regions labeled with red lines), also at the 90% C.L.. large enough to allow for an e cient cancellation in the probability. Thus, in this regime DUNE could disfavor just the upper left and lower right corner of the parameter space. Conversely, in the limit m241 m231 the impact of the new CP-violating phase 24 is much milder and does not allow for a cancellation in the oscillation probability. A closed contour is therefore obtained in this case. NOvA has observed 95 neutral current events at the far detector while 83:5 9:7(stat.) 9:4(syst.) events where expected in the three- avor case. Since no evidence for an sterile neutrino oscillation was found, they placed the following constraints (assuming cos2 14 = 1) for the active-sterile mixings: 24 < 20:8 and 34 < 31:2 at 90% of C.L for a patible with no oscillation at the near detector (0:05 eV2 m241 0:5 eV2). This results m241 comcorrespond to an exposure-equivalent of 6:05 1020 POT and a total systematical errors 12% ref. [28]. Experiments observing atmospheric neutrinos like the Super-Kamiokande experiment have also constrained the tau-sterile mixing angle. SK, after an analysis of 4; 438 live-days of data, found no evidence for sterile neutrinos constraining jU 4j2 < 0:041 and jU 4j2 < 0:18 for m241 > 0:1 eV2 at 90% of C.L [4]. Similarly, IceCube, by the use of jU 4j2 < 0:15 for three years of atmospheric neutrino data from the DeepCore detector, which was consistent with three- avor neutrinos, placed a bound on the active-sterile mixing: jU 4j2 < 0:11 and m241 = 1 eV2 at 90% of C.L [18]. For comparison, in the right panel of gure 5 we show the currently allowed NOvA regions from ref. [28] as well as from atmospheric data from the Super-Kamiokande experiment [4] and IceCube DeepCore data [18].7 7It is worth to notice that all constraints shown in the right panel of gure 5 are valid for an sterile mass squared di erence m421 > 0:1 eV2 and therefore they do not apply to the case shown in left panel. As shown in the gure, DUNE is expected to improve over a factor of two with respect to the current allowed region set by NOvA with a good control of systematics below 5%. With 5% systematics DUNE will also improve over the current IceCube constraint for 24 < 9 . Finally, we want to comment on the impact of having a nonzero electron-sterile mixing in the results shown in gure 5. Even in the case where 14 current constraint were completely relaxed in the analysis (i.e. `free'), our result for 34 does not change at all. Only the 24 bound (for 34 Bay experiment [19] for the 1) is a ected. However, 14 is tightly constrained by Daya m241 range where the current limits on 34, shown in the right panel of gure 5, apply. On the other hand, in the left panel of the same gure (with 14 unconstrained) DUNE is not able to exclude the small window 24 . 24 . 30 with 10% systematical errors. This, also reinforces our conclusion about the loose of constraining power for m241 m231 due to cancellations in the probability. 5 Summary and conclusions The experimental anomalies independently reported in LSND, MiniBooNE, reactor and Gallium experiments have put the possible existence of an eV-scale sterile neutrino under intense scrutiny. In the near future a new generation of short-baseline experiments will come online to refute or con rm these hints, and will place strong constraints on the mixing of a light sterile neutrino with electron and muon neutrinos. Achieving similar bounds on the mixing with tau neutrinos is a much more di cult task, given the technical ! challenges associated to the production and detection of . At long-baseline experiments, however, oscillations in the channel guarantee that most of the beam will have oscillated into by the time it reaches the far detector, thanks to the atmospheric masssquared splitting. By searching for a depletion in the number of neutral-current (NC) events measured at the far detector, experiments like NOvA or MINOS have been able to probe the mixing between and a fourth neutrino. In this work, we have studied the potential of the future DUNE experiment to conduct a search for sterile neutrinos using the NC data expected at the far detector, taking advantage of the excellent capabilities of liquid Argon to discriminate between charged-current and NC events. For simplicity, we have focused on a 3 + 1 scenario, where only one extra sterile neutrino is introduced. In this case, the mixing matrix has to be extended including three additional mixing angles ( 14, 24 and 34) and two CP-violating phases 14 and 24 (our parametrization is given by eq. (2.3)). The oscillation probabilities will generally depend on an additional oscillation frequency dictated by the mass-squared splitting between the active and sterile states, m241. First, we have derived the oscillation probabilities in di erent regimes paying particular attention to the dependence with the new CP-violating phases. Unlike in other studies where the mass of the sterile was required to be at (or around) the eV scale, here we have allowed it to vary between 10 5 eV2 and 10 1 eV2; thus, in eqs. (2.7){(2.9) we provide approximate expressions for the oscillation probabilities in three di erent regimes, depending on the mass of the sterile state: (i) m241 ! 0; (ii) We have then proceeded to simulate the expected sensitivity of the DUNE experiment using the expected NC events collected at the far detector. We have studied the variation of our results with the implementation and size of the systematic errors. The details of our numerical simulations and the 2 implementation can be found in section 3. First, working under the assumption 24 = 14 = 0, we have determined the sensitivity of the DUNE experiment to the third mixing angle 34. In this case, the oscillation probability is independent of the new CP-violating phases; furthermore, oscillations are solely driven by m231, see eq. (2.10). We nd that DUNE will be able to improve over current constraints on this parameter set by the SK experiment, and will be sensitive to values of 0:12 (at 90% CL) for our default implementation of systematic uncertainties. If systematic errors could be reduced down to 5%, the experimental sensitivity would reach 0:07 (at 90% CL). Next we proceeded to study the case where 24 6= 0. In this case, the oscillation probabilities depend on the active-sterile mass-squared splitting. The phenomenology becomes more complicated and, in particular, strong cancellations in the probability can take place for certain values of 24 and m241. First, we considered the 3+1 scenario as the true hypothesis, and determined for which values of the mixing parameters DUNE would be able to reject the three-family scenario. Our results are summarized in gure 4, where we show the dependence of the sensitivity with the CP phase 24, the mixing angle 34 and the size of the systematic errors. We found that the sensitivity of the experiment to the presence of a sterile neutrino, measured as its ability to reject the three-family scenario, depends heavily on the value of the CP phase. For example, for sin2 34 = 0:1 and 24 = 0, DUNE would be able to reject the three-family scenario for sin2 24 . 4 10 3 eV2; conversely, for 24 = (and assuming the same value for 34 and m241), 24 could be almost two orders of magnitude larger and the three-family scenario would not be rejected by the data. The behavior of our results can be easily understood m241 = 10 4 eV2, in terms of the oscillation probabilities, as explained in detail in section 4.2. Finally, we considered the opposite situation, and assumed that the experiment will nd a result that is in agreement with the three-family expectation. In this case, we determined the allowed con dence regions that would turn from the analysis of the simulated data. Our results are shown in gure 5. The simulated data were tested using two very di erent values of the active-sterile mass-squared splitting. In the averaged-out regime ( a closed contour is obtained; we nd that DUNE would be able to improve over NOvA constraints in this place by a factor of two or more, depending on the size of the systematic m241 m231), errors assumed. Conversely, in the case of m241 m231 the experimental results would allow values of 24 and 34 to be as large as 30 . The reason is, again, the possibility of having a strong cancellation in the oscillation probability, which could lead to a nonobservable e ect in the event distributions even in presence of very large mixing angles. The DUNE experiment has unprecedented discrimination between neutral-current and charged-current events for a long-baseline experiment: this will allow for a measurement or constraint of the fraction of a possible sterile neutrino(s). Given the di culties associated to the production and detection of 's, measurement or limiting this fraction by other means is very challenging. In this paper, we show that the DUNE experiment can provide an excellent constrain or discover a sterile neutrino that primarily mixes with only the . Acknowledgments We warmly thank Michel Sorel for providing us with the smearing matrices needed to simulate the liquid Argon detector reconstruction for neutral-current events. PC also thanks Enrique Fernandez-Martinez for useful discussions. DVF is thankful for the support of S~ao Paulo Research Foundation (FAPESP) funding Grant No. 2014/19164-6 and 2017/017496., and also for the URA fellowship that allowed him to visit the theory department at Fermilab where this project started. DVF was also supported by the U.S. Department Of Energy under contracts DE-SC0013632 and DE-SC0009973. This work has received partial support from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 674896. This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, O ce of Science, O ce of High Energy Physics. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. A Complete expressions for the relevant mixing matrix elements in our parametrization Starting from the parametrization in eq. (2.3), the mixing matrix elements needed for the calculation of the sterile appearance probability are given by: (A.1) (A.2) (B.1) U 4 = e i 24 c14s24 ; For 14 = 0, and using eq. (A.1), we nd the following useful expressions: jUs3j2 = c123 c223s234 + sin 2 23s24 sin 2 34 cos 24 + s223s224c324 ; 8 U 4Us4U 3Us3 = c213c24 sin 2 23 sin 2 24 sin 2 34ei 24 2c123s223c324 sin2 2 24: B 2-function The results of our di erent analyses, including spectral information, have been performed with the following Poissonian 2-function: Oi Ti 1 2 n-bins X i where T are the theoretical events (depending on the model parameters) while O corresponds to the `observed' events. T is the result of the sum of signal s(a; c) plus background bg(b), where the systematical errors where included in the usual form: si(a; c) := bgi(b) := k a and b are total normalization systematical errors in signal and background, respectively. For simplicity we have assumed a = b = norm. ci are the bin-to-bin uncorrelated systematics with error shape. The last four terms in eq. (B.1) are penalties to the 2 function due to the systematics included in eq. (B.2), and also due to the standard oscillation parameters that are marginalized over assuming they have been measured as j j . Open Access. Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited. [1] S. Antusch and O. Fischer, Non-unitarity of the leptonic mixing matrix: present bounds and future sensitivities, JHEP 10 (2014) 094 [arXiv:1407.6607] [INSPIRE]. [2] E. Fernandez-Martinez, J. Hernandez-Garcia and J. Lopez-Pavon, Global constraints on heavy neutrino mixing, JHEP 08 (2016) 033 [arXiv:1605.08774] [INSPIRE]. [3] Y. Declais et al., Search for neutrino oscillations at 15-meters, 40-meters and 95-meters from a nuclear power reactor at Bugey, Nucl. Phys. B 434 (1995) 503 [INSPIRE]. [4] Super-Kamiokande collaboration, K. Abe et al., Limits on sterile neutrino mixing using atmospheric neutrinos in Super-Kamiokande, Phys. Rev. D 91 (2015) 052019 [arXiv:1410.2008] [INSPIRE]. [5] MINOS collaboration, P. Adamson et al., Search for sterile neutrinos mixing with muon neutrinos in MINOS, Phys. Rev. Lett. 117 (2016) 151803 [arXiv:1607.01176] [INSPIRE]. [6] NOMAD collaboration, P. Astier et al., Search for ! e oscillations in the NOMAD experiment, Phys. Lett. B 570 (2003) 19 [hep-ex/0306037] [INSPIRE]. [7] NOMAD collaboration, P. Astier et al., Final NOMAD results on ! and e ! oscillations including a new search for tau-neutrino appearance using hadronic tau decays, Nucl. Phys. B 611 (2001) 3 [hep-ex/0106102] [INSPIRE]. [8] S. Parke and M. Ross-Lonergan, Unitarity and the three avor neutrino mixing matrix, Phys. Rev. D 93 (2016) 113009 [arXiv:1508.05095] [INSPIRE]. JHEP 04 (2017) 153 [arXiv:1609.08637] [INSPIRE]. [9] M. Blennow et al., Non-unitarity, sterile neutrinos and non-standard neutrino interactions, [arXiv:1612.07377] [INSPIRE]. observation of e appearance in a beam, Phys. Rev. D 64 (2001) 112007 [12] MiniBooNE collaboration, A.A. Aguilar-Arevalo et al., A search for electron neutrino m2 1 eV2 scale, Phys. Rev. Lett. 98 (2007) 231801 [arXiv:0704.1500] [13] MiniBooNE collaboration, A.A. Aguilar-Arevalo et al., Event excess in the MiniBooNE ! e oscillations, Phys. Rev. Lett. 105 (2010) 181801 [arXiv:1007.1150] HJEP07(218)9 appearance at the (2011) 054615 [arXiv:1101.2663] [INSPIRE]. 84 (2011) 024617 [Erratum ibid. C 85 (2012) 029901] [arXiv:1106.0687] [INSPIRE]. (2011) 065504 [arXiv:1006.3244] [INSPIRE]. [17] IceCube collaboration, M.G. Aartsen et al., Searches for sterile neutrinos with the IceCube detector, Phys. Rev. Lett. 117 (2016) 071801 [arXiv:1605.01990] [INSPIRE]. [18] IceCube collaboration, M.G. Aartsen et al., Search for sterile neutrino mixing using three years of IceCube DeepCore data, Phys. Rev. D 95 (2017) 112002 [arXiv:1702.05160] full con guration of the Daya Bay experiment, Phys. Rev. Lett. 117 (2016) 151802 [arXiv:1607.01174] [INSPIRE]. [20] Borexino collaboration, G. Bellini et al., SOX: Short distance neutrino Oscillations with BoreXino, JHEP 08 (2013) 038 [arXiv:1304.7721] [INSPIRE]. [21] STEREO collaboration, V. Helaine, Sterile neutrino search at the ILL nuclear reactor: the STEREO experiment, in the proceedings of Prospects in Neutrino Physics (NuPhys2015), December 16{18, London, U.K. (2016), arXiv:1604.08877 [INSPIRE]. [22] LAr1-ND, ICARUS-WA104, MicroBooNE collaboration, M. Antonello et al., A proposal for a three detector short-baseline neutrino oscillation program in the Fermilab booster neutrino beam, arXiv:1503.01520 [INSPIRE]. [23] MINOS, Daya Bay collaboration, P. Adamson et al., Limits on active to sterile neutrino oscillations from disappearance searches in the MINOS, Daya Bay and Bugey-3 experiments, Phys. Rev. Lett. 117 (2016) 151801 [arXiv:1607.01177] [INSPIRE]. [24] G.H. Collin et al., First constraints on the complete neutrino mixing matrix with a sterile neutrino, Phys. Rev. Lett. 117 (2016) 221801 [arXiv:1607.00011] [INSPIRE]. [25] A. Esmaili, F. Halzen and O.L.G. Peres, Exploring - s mixing with cascade events in DeepCore, JCAP 07 (2013) 048 [arXiv:1303.3294] [INSPIRE]. to oscillations induced by a sterile neutrino state obtained by OPERA at the CNGS beam, JHEP 06 (2015) 069 [arXiv:1503.01876] [INSPIRE]. [27] MINOS collaboration, P. Adamson et al., Active to sterile neutrino mixing limits from [arXiv:1104.3922] [INSPIRE]. [INSPIRE]. HJEP07(218)9 Underground Neutrino Experiment (DUNE), arXiv:1512.06148 [INSPIRE]. [30] J.M. Berryman et al., Sterile neutrino at the Deep Underground Neutrino Experiment, Phys. Rev. D 92 (2015) 073012 [arXiv:1507.03986] [INSPIRE]. [31] R. Gandhi, B. Kayser, M. Masud and S. Prakash, The impact of sterile neutrinos on CP measurements at long baselines, JHEP 11 (2015) 039 [arXiv:1508.06275] [INSPIRE]. [32] S.K. Agarwalla, S.S. Chatterjee and A. Palazzo, Physics reach of DUNE with a light sterile neutrino, JHEP 09 (2016) 016 [arXiv:1603.03759] [INSPIRE]. [33] S.K. Agarwalla, S.S. Chatterjee and A. Palazzo, Octant of 23 in danger with a light sterile neutrino, Phys. Rev. Lett. 118 (2017) 031804 [arXiv:1605.04299] [INSPIRE]. [34] D. Dutta et al., Capabilities of long-baseline experiments in the presence of a sterile neutrino, JHEP 11 (2016) 122 [arXiv:1607.02152] [INSPIRE]. [35] J. Rout, M. Masud and P. Mehta, Can we probe intrinsic CP and T violations and nonunitarity at long baseline accelerator experiments?, Phys. Rev. D 95 (2017) 075035 [arXiv:1702.02163] [INSPIRE]. [36] S. Choubey, D. Dutta and D. Pramanik, Imprints of a light sterile neutrino at DUNE, T2HK and T2HKK, Phys. Rev. D 96 (2017) 056026 [arXiv:1704.07269] [INSPIRE]. [37] S. Choubey and D. Pramanik, Constraints on sterile neutrino oscillations using DUNE near detector, Phys. Lett. B 764 (2017) 135 [arXiv:1604.04731] [INSPIRE]. [38] MINOS collaboration, P. Adamson et al., Search for sterile neutrino mixing in the MINOS long baseline experiment, Phys. Rev. D 81 (2010) 052004 [arXiv:1001.0336] [INSPIRE]. [39] P. Huber, M. Lindner and W. Winter, Simulation of long-baseline neutrino oscillation experiments with GLoBES (General Long Baseline Experiment Simulator), Comput. Phys. Commun. 167 (2005) 195 [hep-ph/0407333] [INSPIRE]. [40] P. Huber, J. Kopp, M. Lindner, M. Rolinec and W. Winter, New features in the simulation of neutrino oscillation experiments with GLoBES 3.0: General Long Baseline Experiment Simulator, Comput. Phys. Commun. 177 (2007) 432 [hep-ph/0701187] [INSPIRE]. [41] P. Coloma, P. Huber, J. Kopp and W. Winter, Systematic uncertainties in long-baseline neutrino oscillations for large 13, Phys. Rev. D 87 (2013) 033004 [arXiv:1209.5973] [INSPIRE]. [42] J. Kopp, New physics engine for the inclusion sterile neutrinos and non-standard interactions in GLoBES, available at https://www.mpi-hd.mpg.de/personalhomes/globes/tools.html. arXiv:1311.6774 [INSPIRE]. CDR, arXiv:1606.09550 [INSPIRE]. HJEP07(218)9 (2014) 093006 [arXiv:1405.7540] [INSPIRE]. [10] F.J. Escrihuela et al., Probing CP -violation with non-unitary mixing in long-baseline neutrino oscillation experiments: DUNE as a case study, New J . Phys. 19 ( 2017 ) 093005 [11] LSND collaboration, A . Aguilar-Arevalo et al., Evidence for neutrino oscillations from the [ 14] T.A. Mueller et al., Improved predictions of reactor antineutrino spectra , Phys. Rev. C 83 [15] P. Huber , On the determination of anti-neutrino spectra from nuclear reactors , Phys. Rev . C [16] C. Giunti and M. Laveder , Statistical signi cance of the Gallium anomaly , Phys. Rev. C 83 [26] OPERA collaboration , N. Agafonova et al., Limits on neutral-current interactions in MINOS, Phys. Rev. Lett . 107 ( 2011 ) 011802 [28] NOvA collaboration, P. Adamson et al., Search for active-sterile neutrino mixing using neutral-current interactions in NOvA, Phys . Rev. D 96 ( 2017 ) 072006 [arXiv: 1706 .04592] [29] DUNE collaboration , R. Acciarri et al., Long-Baseline Neutrino Facility (LBNF) and Deep [43] V. De Romeri , E. Fernandez-Martinez and M. Sorel , Neutrino oscillations at DUNE with improved energy reconstruction , JHEP 09 ( 2016 ) 030 [arXiv: 1607 .00293] [INSPIRE]. [44] E.D. Church , LArSoft: a software package for liquid argon time projection drift chambers , [45] DUNE collaboration, T. Alion et al., Experiment simulation con gurations used in DUNE [46] I. Esteban et al., Updated t to three neutrino mixing: exploring the accelerator-reactor complementarity , JHEP 01 ( 2017 ) 087 [arXiv: 1611 .01514] [INSPIRE]. [47] F. Capozzi et al., Neutrino masses and mixings: status of known and unknown 3 parameters, Nucl . Phys. B 908 ( 2016 ) 218 [arXiv: 1601 .07777] [INSPIRE]. [48] D.V. Forero , M. Tortola and J.W.F. Valle , Neutrino oscillations re tted, Phys. Rev. D 90 [49] L. Alvarez-Ruso et al., NuSTEC White Paper: status and challenges of neutrino-nucleus scattering , Prog. Part. Nucl. Phys . 100 ( 2018 ) 1 [arXiv: 1706 .03621] [INSPIRE].


This is a preview of a remote PDF: https://link.springer.com/content/pdf/10.1007%2FJHEP07%282018%29079.pdf

Pilar Coloma, David V. Forero, Stephen J. Parke. DUNE sensitivities to the mixing between sterile and tau neutrinos, Journal of High Energy Physics, 2018, 79, DOI: 10.1007/JHEP07(2018)079