Detecting matter effects in long baseline experiments

Experiments strongly suggest that the flavour mixing responsible for the atmospheric neutrino anomaly is very close to being maximal. Thus, it is of great theoretical as well as experimental importance to measure any possible deviation from maximality. In this context, we reexamine the effects of matter interactions in long baseline neutrino oscillation experiments. Contrary to popular belief, the muon neutrino survival probability is shown to be quite sensitive to matter effects. Moreover, for moderately long baselines, the difference between the survival probilities for $\nu_\mu$ and $\bar\nu_\mu$ is shown to be large and sensitive to the deviation of $|U_{\mu 3}|$ from maximality. Performing a realistic analysis, we demonstrate that a muon-storage ring $\nu$-source alongwith an iron calorimeter detector can measure such deviations. (Contrary to recent claims, this is not so for the NuMI--{\sc minos} experiment.) We also discuss the possible correlation in measuring $U_{\mu 3}$ and $U_{e3}$ in such experiment.Comment: 18 pages, LaTe

θ13\theta_{13}, δ\delta and the neutrino mass hierarchy at a γ=350\gamma=350 double baseline Li/B β\beta-Beam

We consider a $\beta$-Beam facility where $^8$Li and $^8$B ions are accelerated at $\gamma = 350$, accumulated in a 10 Km storage ring and let decay, so as to produce intense $\bar \nu_e$ and $\nu_e$ beams. These beams illuminate two iron detectors located at $L \simeq 2000$ Km and $L \simeq 7000$ Km, respectively. The physics potential of this setup is analysed in full detail as a function of the flux. We find that, for the highest flux ($10 \times 10^{18}$ ion decays per year per baseline), the sensitivity to $\theta_{13}$ reaches $\sin^2 2 \theta_{13} \geq 2 \times10^{-4}$; the sign of the atmospheric mass difference can be identified, regardless of the true hierarchy, for $\sin^2 2 \theta_{13} \geq 4\times10^{-4}$; and, CP-violation can be discovered in 70% of the $\delta$-parameter space for $\sin^2 2 \theta_{13} \geq 10^{-3}$, having some sensitivity to CP-violation down to $\sin^2 2 \theta_{13} \geq 10^{-4}$ for $|\delta| \sim 90^\circ$.Comment: 35 pages, 20 figures. Minor changes, matches the published versio

Nucleon Decay Searches with large Liquid Argon TPC Detectors at Shallow Depths: atmospheric neutrinos and cosmogenic backgrounds

Grand Unification of the strong, weak and electromagnetic interactions into a single unified gauge group is an extremely appealing idea which has been vigorously pursued theoretically and experimentally for many years. The detection of proton or bound-neutron decays would represent its most direct experimental evidence. In this context, we studied the physics potentialities of very large underground Liquid Argon Time Projection Chambers (LAr TPC). We carried out a detailed simulation of signal efficiency and background sources, including atmospheric neutrinos and cosmogenic backgrounds. We point out that a liquid Argon TPC, offering good granularity and energy resolution, low particle detection threshold, and excellent background discrimination, should yield very good signal over background ratios in many possible decay modes, allowing to reach partial lifetime sensitivities in the range of 1034−1035 years with exposures up to 1000 kton×year, often in quasi-background-free conditions optimal for discoveries at the few events level, corresponding to atmospheric neutrino background rejections of the order of 105. Multi-prong decay modes like e.g. p→μ−π+K+ or p→e+π+π− and channels involving kaons like e.g. p→K+ν¯, p→e+K0 and p→μ+K0 are particularly suitable, since liquid Argon imaging (...)This work was in part supported by ETH and the Swiss National Foundation. AB, AJM and SN have been supported by CICYT Grants FPA-2002-01835 and FPA-2005-07605-C02-01. SN acknowledges support from the Ramon y Cajal Programme. We thank P. Sala for help with FLUKA while she was an ETH employee

Physics at a future neutrino factory and super-beam facility

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