Determination of mass hierarchy with νμ → ντ appearance and the effect of nonstandard interactions

Abstract

Crucial developments in neutrino physics would be the determination of the mass hierarchy (MH) and measurement of the CP phase in the leptonic sector. The patterns of the transition probabilities P (νµ → ντ ) and P (νµ →ντ ) are sensitive to these oscillation parameters. An asymmetry parameter can be defined as the difference of these two probabilities normalized to their sum. The profile of the asymmetry parameter gives a clear signal of the mass ordering as it is found to be positive for inverted hierarchy and negative for normal hierarchy. The asymmetry parameter is also sensitive to the CP phase. We consider the effects of non-standard neutrino interactions (NSI) on the determination of the mass hierarchy. Since we assume the largest new physics effects involve the τ sector only, we ignore NSI in production and study the NSI effects in detection as well as along propagation. We find that the NSI effects can significantly modify the prediction of the asymmetry parameter though the MH can still be resolved. PACS numbers:After ruling out the zero value of the smallest mixing angle θ 13 in the lepton sector with C.L. around 5σ [1], the main scope of the future experiments is to answer some open questions such as the absolute mass scale, mass hierarchy, and CP asymmetry in the lepton sector.Knowledge of the mass hierarchy has an impact on determining the neutrino absolute mass scale, CP asymmetry in the lepton sector, and the nature of the neutrino to be either Dirac or Majorana. Once the ordering of the neutrino mass states is determined, the uncertainty on the measurement of the CP-violating phase, δ CP , is significantly reduced. Measuring the mass ordering can cut down the domain for observation of a signal in the neutrinoless double beta decay experiments. Cosmological measurements are sensitive to the sum of neutrino masses, thus, knowledge of the mass hierarchy could help in determining the absolute neutrino mass scale.The mass hierarchy (MH) can be determined using different techniques. The transition probability from a neutrino flavor to another, in the presence of matter effect, is sensitive to the mass hierarchy. The shape of the oscillation profile can be used to infer the sign of ∆m 2 23 thereby indicating whether we have normal hierarchy (NH) or the inverted hierarchy (IH). The standard proposal is to use the appearance channel ν µ → ν e to measure MH. Determination of mass hierarchy is in the scope of several future experiments such as DUNE [2][3][4][5], 7], LBNO [8,9], and INO [10]. A variety of other experiments has some sensitivity to the mass hierarchy such as the reactor neutrino experiments JUNO (formerly known as Daya Bay II) and RENO as well as PINGU [11] at IceCube. The CP asymmetry can be measured in very long base line neutrino experiments such as LBNO (2300 km baseline length) and DUNE (1300 km baseline length) as well as Hyper-K (295 km baseline length). The existence of neutrino masses and mixing require physics beyond the standard model (SM). Hence it is not unexpected that neutrinos...

Tau neutrinos at DUNE: New strategies, new opportunities

“…Despite such difficulties, upcoming multipurpose neutrino experiments, such as DUNE [14], are well posed to detect tau neutrinos given their large fiducial volume, powerful neutrino beam and exquisite track reconstruction capability. There have been a number of works which explore the tau neutrino sector including pioneering proposals for observing ν τ at beam dump experiments [15] and the subsequent experimental search by NOMAD [16], polarization effects on τ decay products for atmospheric and beam ν τ searches [17][18][19][20][21], optimization of cuts on τ decay products in the DUNE beam neutrino sample [22], tests of unitarity and patterns of leptonic mixing [23][24][25] and beyond the Standard Model physics probes with ν τ measurements [26][27][28][29].…”

Tau neutrinos at DUNE: new strategies, new opportunities

“…Despite such difficulties, upcoming multi-purpose neutrino experiments, such as DUNE [14], are well posed to detect tau neutrinos given their large fiducial volume, powerful neutrino beam and exquisite track reconstruction capability. There have been a number of works which explore the tau neutrino sector including pioneering proposals for observing ν τ at beam dump experiments [15] and the subsequent experimental search by NOMAD [16], polarization effects on τ decay products for atmospheric and beam ν τ searches [17][18][19][20][21], optimization of cuts on τ decay products in the DUNE beam neutrino sample [22], tests of unitarity and patterns of leptonic mixing [23][24][25] and beyond the Standard Model physics probes with ν τ measurements [26][27][28][29].…”