The conclusions of the Physics Working Group of the International Scoping Study of a future Neutrino Factory and super-beam facility (the ISS) are presented. The ISS was carried out by the international community between NuFact05, (the 7th International Workshop on Neutrino Factories and Super-beams, Laboratori Nazionali di Frascati, Rome, 21-26 June 2005) and NuFact06 (Ivine, CA, 24-30 August 2006). The physics case for an extensive experimental programme to understand the properties of the neutrino is presented and the role of high-precision measurements of neutrino oscillations within this programme is discussed in detail. The performance of second-generation super-beam experiments, beta-beam facilities and the Neutrino Factory are evaluated and a quantitative comparison of the discovery potential of the three classes of facility is presented. High-precision studies of the properties of the muon are complementary to the study of neutrino oscillations. The Neutrino Factory has the potential to provide extremely intense muon beams and the physics potential of such beams is discussed in the final section of the report.

The first results from the KamLAND experiment in conjunction with the global solar neutrino data has demonstrated striking ability to constrain the ∆m 2 ⊙ (∆m 2 21 ) very precisely. However the allowed range of θ ⊙ (θ 12 ) did not change much with the inclusion of the KamLAND results. In this paper we probe if future data from KamLAND can increase the accuracy of the allowed range in θ ⊙ and conclude that even after 3 kton-year of statistics and most optimistic error estimates, KamLAND may find it hard to significantly improve the bounds on the mixing angle obtained from the solar neutrino data. We discuss the θ 12 sensitivity of the survival probabilities in matter (vacuum) as is relevant for the solar (Kam-LAND) experiments. We find that the presence of matter effects in the survival probabilities for 8 B neutrinos give the solar neutrino experiments SK and SNO an edge over KamLAND, as far as θ 12 sensitivity is concerned, particularly near maximal mixing. Among solar neutrino experiments we identify SNO as the most promising candidate for constraining θ 12 and make a projected sensitivity test for the mixing angle by reducing the error in the neutral current measurement at SNO. Finally we argue that the most accurate bounds on θ 12 can be achieved in a reactor experiment, if the corresponding baseline and energy can be tuned to a minimum in the survival probability. We propose a new reactor experiment which can give the value of tan 2 θ 12 to within 14%. We also discuss the future Borexino and LowNu experiments. 1

The Deep Underground Neutrino Experiment (DUNE) will be a world-class neutrino observatory and nucleon decay detector designed to answer fundamental questions about the nature of elementary particles and their role in the universe.

We study the problem of determination of the sign of ∆m 2 31 , or the neutrino mass hierarchy, through observations of atmospheric neutrinos in future detectors. We consider two proposed detector types : (a) Megaton sized waterCerenkov detectors, which can measure the event rates of ν µ +ν µ and ν e +ν e and (b) 100 kton sized magnetized iron detectors, which can measure the event rates of ν µ andν µ . For energies and path-lengths relevant to atmospheric neutrinos, these rates obtain significant matter contributions from P µe , P µµ and P ee , leading to an appreciable sensitivity to the hierarchy. We do a binned χ 2 analysis of simulated data in these two types of detectors which includes the effect of smearing in neutrino energy and direction and incorporates detector efficiencies and relevant statistical, theoretical and systematic errors. We also marginalize the χ 2 over the allowed ranges of neutrino parameters in order to accurately account for their uncertainties. Finally, we compare the performance of both types of detectors vis a vis the hierarchy determination.

We discuss the possibilities of high precision measurement of the solar neutrino mixing angle θ ⊙ ≡ θ 12 in solar and reactor neutrino experiments. The improvements in the determination of sin 2 θ 12 , which can be achieved with the expected increase of statistics and reduction of systematic errors in the currently operating solar and KamLAND experiments, are summarised. The potential of LowNu ν − e elastic scattering experiment, designed to measure the pp solar neutrino flux, for high precision determination of sin 2 θ 12 , is investigated in detail. The accuracy in the measurement of sin 2 θ 12 , which can be achieved in a reactor experiment with a baseline L ∼ (50 − 70) km, corresponding to a Survival Probability MINimum (SPMIN), is thoroughly studied. We include the effect of the uncertainty in the value of sin 2 θ 13 in the analyses. A LowNu measurement of the pp neutrino flux with a 1% error would allow to determine sin 2 θ 12 with an error of 14% (17%) at 3σ from a two-generation (three-generation) analysis. The same parameter sin 2 θ 12 can be measured with an uncertainty of 2% (6%) at 1σ (3σ) in a reactor experiment with L ∼ 60 km, statistics of ∼60 GWkTy and systematic error of 2%. For the same statistics, the increase of the systematic error from 2% to 5% leads to an increase in the uncertainty in sin 2 θ 12 from 6% to 9% at 3σ. The inclusion of the sin 2 θ 13 uncertainty in the analysis changes the error on sin 2 θ 12 to 3% (9%). The effect of sin 2 θ 13 uncertainty on the sin 2 θ 12 measurement in both types of experiments is considerably smaller than naively expected.