The physics impact of proton track identification in future megaton-scale water Cherenkov detectors

In this paper, we investigate the impact in future megaton-scale water Cherenkov detectors of identifying proton Cherenkov rings. We estimate the expected event rates for detected neutral current and charged current quasi-elastic neutrino interactions from atmospheric neutrinos in a megaton-scale Super-Kamiokande-like detector with both 40% and 20% photo-cathode coverage. With this sample we examine the prospects for measuring the neutrino oscillation pattern, and searching for sterile neutrinos. We also determine the size of selected charged current quasi-elastic samples in a 300-kton fiducial volume Super-Kamiokande-like detector from examples of both conventional super-beams and beta-beams proposed in the literature. With these samples, it is shown that full kinematic neutrino reconstruction using the outgoing proton can improve the reconstructed energy resolution, and give good neutrino versus anti-neutrino tagging capabilities, adding important capabilities to water Cherenkov detectors in future projects. We determine the beam parameters necessary to make use of this technique and present distributions of neutrino and anti-neutrino selection efficiencies.Comment: 21 pages, 8 figures. Revised version with improved figures, text and structure, published in JHE

General bounds on non-standard neutrino interactions

We derive model-independent bounds on production and detection non-standard neutrino interactions (NSI). We find that the constraints for NSI parameters are around O(10^{-2}) to O(10^{-1}). Furthermore, we review and update the constraints on matter NSI. We conclude that the bounds on production and detection NSI are generally one order of magnitude stronger than their matter counterparts.Comment: 18 pages, revtex4, 1 axodraw figure. Minor changes, matches published versio

Loop bounds on non-standard neutrino interactions

We reconsider the bounds on non-standard neutrino interactions with matter which can be derived by constraining the four-charged-lepton operators induced at the loop level. We find that these bounds are model dependent. Naturalness arguments can lead to much stronger constraints than those presented in previous studies, while no completely model-independent bounds can be derived. We will illustrate how large loop-contributions to four-charged-lepton operators are induced within a particular model that realizes gauge invariant non-standard interactions and discuss conditions to avoid these bounds. These considerations mainly affect the $\mathcal O(10^{-4})$ constraint on the non-standard coupling strength \eps_{e\mu}, which is lost. The only model-independent constraints that can be derived are $\mathcal O(10^{-1})$. However, significant cancellations are required in order to saturate this bound.Comment: Minor changes, version to be published in JHEP. 17 pages, 3 Axodraw figures, REVTeX

Optimized Two-Baseline Beta-Beam Experiment

We propose a realistic Beta-Beam experiment with four source ions and two baselines for the best possible sensitivity to theta_{13}, CP violation and mass hierarchy. Neutrinos from 18Ne and 6He with Lorentz boost gamma=350 are detected in a 500 kton water Cerenkov detector at a distance L=650 km (first oscillation peak) from the source. Neutrinos from 8B and 8Li are detected in a 50 kton magnetized iron detector at a distance L=7000 km (magic baseline) from the source. Since the decay ring requires a tilt angle of 34.5 degrees to send the beam to the magic baseline, the far end of the ring has a maximum depth of d=2132 m for magnetic field strength of 8.3 T, if one demands that the fraction of ions that decay along the straight sections of the racetrack geometry decay ring (called livetime) is 0.3. We alleviate this problem by proposing to trade reduction of the livetime of the decay ring with the increase in the boost factor of the ions, such that the number of events at the detector remains almost the same. This allows to substantially reduce the maximum depth of the decay ring at the far end, without significantly compromising the sensitivity of the experiment to the oscillation parameters. We take 8B and 8Li with gamma=390 and 656 respectively, as these are the largest possible boost factors possible with the envisaged upgrades of the SPS at CERN. This allows us to reduce d of the decay ring by a factor of 1.7 for 8.3 T magnetic field. Increase of magnetic field to 15 T would further reduce d to 738 m only. We study the sensitivity reach of this two baseline two storage ring Beta-Beam experiment, and compare it with the corresponding reach of the other proposed facilities.Comment: 17 pages, 3 eps figures. Minor changes, matches version accepted in JHE

Scintillator detectors with long WLS fibers and multi-pixel photodiodes

We have studied the possibility of using Geiger mode multi-pixel photodiodes to read out long scintillator bars with a single wavelength-shifting fiber embedded along the bar. This detector configuration can be used in large volume detectors in future long baseline neutrino oscillation experiments. Prototype bars of 0.7 cm thickness and different widths have been produced and tested using two types of multi-pixel photodiodes: MRS APD (CPTA, Moscow) and MPPC (Hamamatsu). A minimum light yield of 7.2 p.e./MeV was obtained for a 4 cm wide bar

Neutrino Probes of the Nature of Light Dark Matter

Dark matter particles gravitationally trapped inside the Sun may annihilate into Standard Model particles, producing a flux of neutrinos. The prospects of detecting these neutrinos in future multi-\kton{} neutrino detectors designed for other physics searches are explored here. We study the capabilities of a 34/100 \kton{} liquid argon detector and a 100 \kton{} magnetized iron calorimeter detector. These detectors are expected to determine the energy and the direction of the incoming neutrino with unprecedented precision allowing for tests of the dark matter nature at very low dark matter masses, in the range of 5-50 GeV. By suppressing the atmospheric background with angular cuts, these techniques would be sensitive to dark matter - nucleon spin dependent cross sections at the fb level, reaching down to a few ab for the most favorable annihilation channels and detector technology.Comment: Minor changes and clarifications, matches JCAP versio

The influence of physical activity performed at 20-40 years of age on cardiovascular outcomes in medical patients aged 65-75

Summary Introduction Several studies show that physical activity can reduce the risk of cardiovascular disease, but the vast majority of these focus on the short- to intermediate-term benefits or refer to very specific populations. This observational study was conducted to determine whether physical activity performed during the third or fourth decade of life influences the occurrence of cardiovascular events in patients aged 65-75 years. Materials and methods We studied a cohort of 2191 unselected patients admitted to Internal Medicine Departments. Data were collected on the patients' medical history and their physical activity level when they were 20 to 40 years old. For the latter purpose, we used a specific questionnaire to assess the levels of physical activity related to the patients' job, daily life, leisure time, and sports. Results Almost half (44.2%) of the patients we evaluated reported moderate-intense physical activity when they were 20-40 years old. Around one third (35.8%) of the patients had experienced at least one major cardiovascular event, and there was a slight trend towards fewer cardiovascular events in patients with histories of physical activity (mean risk reduction: 4%, multivariate analysis). More evident benefits were observed in the subgroup of patients with diabetes, where cardiovascular outcomes were much better in patients who had been physically active than in those with sedentary life-styles (mean risk reduction: 24%). Conclusions Given its design, our study may have underestimated the cardiovascular benefits of physical activity. Nonetheless, our results suggest that moderate-intense exercise during young adulthood may have limited beneficial effects on cardiovascular disease in old age, except in specific high-risk populations (diabetic patients). More evident benefits are probably associated with regular physical activity throughout life

Perturbation Theory of Neutrino Oscillation with Nonstandard Neutrino Interactions

We discuss various physics aspects of neutrino oscillation with non-standard interactions (NSI). We formulate a perturbative framework by taking \Delta m^2_{21} / \Delta m^2_{31}, s_{13}, and the NSI elements \epsilon_{\alpha \beta} (\alpha, \beta = e, \mu, \tau) as small expansion parameters of the same order \epsilon. Within the \epsilon perturbation theory we obtain the S matrix elements and the neutrino oscillation probability formula to second order (third order in \nu_e related channels) in \epsilon. The formula allows us to estimate size of the contribution of any particular NSI element \epsilon_{\alpha beta} to the oscillation probability in arbitrary channels, and gives a global bird-eye view of the neutrino oscillation phenomena with NSI. Based on the second-order formula we discuss how all the conventional lepton mixing as well as NSI parameters can be determined. Our results shows that while \theta_{13}, \delta, and the NSI elements in \nu_e sector can in principle be determined, complete measurement of the NSI parameters in the \nu_\mu - \nu_\tau sector is not possible by the rate only analysis. The discussion for parameter determination and the analysis based on the matter perturbation theory indicate that the parameter degeneracy prevails with the NSI parameters. In addition, a new solar-atmospheric variable exchange degeneracy is found. Some general properties of neutrino oscillation with and without NSI are also illuminated.Comment: manuscript restructured, discussion of new type of parameter degeneracy added. 47 page

On the impact of systematical uncertainties for the CP violation measurement in superbeam experiments

Superbeam experiments can, in principle, achieve impressive sensitivities for CP violation in neutrino oscillations for large $\theta_{13}$. We study how those sensitivities depend on assumptions about systematical uncertainties. We focus on the second phase of T2K, the so-called T2HK experiment, and we explicitly include a near detector in the analysis. Our main result is that even an idealised near detector cannot remove the dependence on systematical uncertainties completely. Thus additional information is required. We identify certain combinations of uncertainties, which are the key to improve the sensitivity to CP violation, for example the ratio of electron to muon neutrino cross sections and efficiencies. For uncertainties on this ratio larger than 2%, T2HK is systematics dominated. We briefly discuss how our results apply to a possible two far detector configuration, called T2KK. We do not find a significant advantage with respect to the reduction of systematical errors for the measurement of CP violation for this setup.Comment: 30 pages, 10 figures, version accepted for publication in JHE

Robust Neutrino Constraints by Combining Low Redshift Observations with the CMB

We illustrate how recently improved low-redshift cosmological measurements can tighten constraints on neutrino properties. In particular we examine the impact of the assumed cosmological model on the constraints. We first consider the new HST H0 = 74.2 +/- 3.6 measurement by Riess et al. (2009) and the sigma8*(Omegam/0.25)^0.41 = 0.832 +/- 0.033 constraint from Rozo et al. (2009) derived from the SDSS maxBCG Cluster Catalog. In a Lambda CDM model and when combined with WMAP5 constraints, these low-redshift measurements constrain sum mnu<0.4 eV at the 95% confidence level. This bound does not relax when allowing for the running of the spectral index or for primordial tensor perturbations. When adding also Supernovae and BAO constraints, we obtain a 95% upper limit of sum mnu<0.3 eV. We test the sensitivity of the neutrino mass constraint to the assumed expansion history by both allowing a dark energy equation of state parameter w to vary, and by studying a model with coupling between dark energy and dark matter, which allows for variation in w, Omegak, and dark coupling strength xi. When combining CMB, H0, and the SDSS LRG halo power spectrum from Reid et al. 2009, we find that in this very general model, sum mnu < 0.51 eV with 95% confidence. If we allow the number of relativistic species Nrel to vary in a Lambda CDM model with sum mnu = 0, we find Nrel = 3.76^{+0.63}_{-0.68} (^{+1.38}_{-1.21}) for the 68% and 95% confidence intervals. We also report prior-independent constraints, which are in excellent agreement with the Bayesian constraints.Comment: 19 pages, 6 figures, submitted to JCAP; v2: accepted version. Added section on profile likelihood for Nrel, improved plot