Exploration of Possible Quantum Gravity Effects with Neutrinos I: Decoherence in Neutrino Oscillations Experiments

Quantum gravity may involve models with stochastic fluctuations of the associated metric field, around some fixed background value. Such stochastic models of gravity may induce decoherence for matter propagating in such fluctuating space time. In most cases, this leads to fewer neutrinos of all active flavours being detected in a long baseline experiment as compared to three-flavour standard neutrino oscillations. We discuss the potential of the CNGS and J-PARC beams in constraining models of quantum-gravity induced decoherence using neutrino oscillations as a probe. We use as much as possible model-independent parameterizations, even though they are motivated by specific microscopic models, for fits to the expected experimental data which yield bounds on quantum-gravity decoherence parameters.Comment: 9 pages, 4 figures, proceedings for invited talk by A.Sakharov at DISCRETE'08, Valencia, Spain; December 200

Quantum-Gravity Decoherence Effects in Neutrino Oscillations: Expected Constraints from CNGS and J-PARC

Quantum decoherence, the evolution of pure states into mixed states, may be a feature of quantum-gravity models. In most cases, such models lead to fewer neutrinos of all active flavours being detected in a long baseline experiment as compared to three-flavour standard neutrino oscillations. We discuss the potential of the CNGS and J-PARC beams in constraining models of quantum-gravity induced decoherence using neutrino oscillations as a probe. We use as much as possible model-independent parameterizations, even though they are motivated by specific microscopic models, for fits to the expected experimental data which yield bounds on quantum-gravity decoherence parameters.Comment: 40 pages, 8 figures, minor correction

Probes of Lorentz Violation in Neutrino Propagation

It has been suggested that the interactions of energetic particles with the foamy structure of space-time thought to be generated by quantum-gravitational (QG) effects might violate Lorentz invariance, so that they do not propagate at a universal speed of light. We consider the limits that may be set on a linear or quadratic violation of Lorentz invariance in the propagation of energetic neutrinos, v/c=[1 +- (E/M_\nuQG1)] or [1 +- (E/M_\nu QG2}^2], using data from supernova explosions and the OPERA long-baseline neutrino experiment. Using the SN1987a neutrino data from the Kamioka II, IMB and Baksan experiments, we set the limits M_\nuQG1 > 2.7(2.5)x10^10 GeV for subluminal (superluminal) propagation, respectively, and M_\nuQG2 >4.6(4.1)x10^4 GeV at the 95% confidence level. A future galactic supernova at a distance of 10 kpc would have sensitivity to M_\nuQG1 > 2(4)x10^11 GeV for subluminal (superluminal) propagation, respectively, and M_\nuQG2 > 2(4)x10^5 GeV. With the current CNGS extraction spill length of 10.5 micro seconds and with standard clock synchronization techniques, the sensitivity of the OPERA experiment would reach M_\nuQG1 ~ 7x10^5 GeV (M_\nuQG2 ~ 8x10^3 GeV) after 5 years of nominal running. If the time structure of the SPS RF bunches within the extracted CNGS spills could be exploited, these figures would be significantly improved to M_\nuQG1 ~ 5x10^7 GeV (M_\nuQG2 ~ 4x10^4 GeV). These results can be improved further if similar time resolution can be achieved with neutrino events occurring in the rock upstream of the OPERA detector: we find potential sensitivities to M_\nuQG1 ~ 4x10^8 GeV and M_\nuQG2 ~ 7x10^5 GeV.Comment: 33 pages, 22 figures, version accepted for publication in Physical Review

Exploration of Possible Quantum Gravity Effects with Neutrinos II: Lorentz Violation in Neutrino Propagation

It has been suggested that the interactions of energetic particles with the foamy structure of space-time thought to be generated by quantum-gravitational (QG) effects might violate Lorentz invariance, so that they do not propagate at a universal speed of light. We consider the limits that may be set on a linear or quadratic violation of Lorentz invariance in the propagation of energetic neutrinos, v/c=[1 +- (E/M_\nuQG1)] or [1 +- (E/M_\nu QG2}^2], using data from supernova explosions and the OPERA long-baseline neutrino experiment.Comment: 8 pages, 6 figures, proceedings for invited talk by A.Sakharov at DISCRETE'08, Valencia, Spain; December 200

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

Neutrino Physics with JUNO

The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purposeunderground liquid scintillator detector, was proposed with the determinationof the neutrino mass hierarchy as a primary physics goal. It is also capable ofobserving neutrinos from terrestrial and extra-terrestrial sources, includingsupernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos,atmospheric neutrinos, solar neutrinos, as well as exotic searches such asnucleon decays, dark matter, sterile neutrinos, etc. We present the physicsmotivations and the anticipated performance of the JUNO detector for variousproposed measurements. By detecting reactor antineutrinos from two power plantsat 53-km distance, JUNO will determine the neutrino mass hierarchy at a 3-4sigma significance with six years of running. The measurement of antineutrinospectrum will also lead to the precise determination of three out of the sixoscillation parameters to an accuracy of better than 1\%. Neutrino burst from atypical core-collapse supernova at 10 kpc would lead to ~5000inverse-beta-decay events and ~2000 all-flavor neutrino-proton elasticscattering events in JUNO. Detection of DSNB would provide valuable informationon the cosmic star-formation rate and the average core-collapsed neutrinoenergy spectrum. Geo-neutrinos can be detected in JUNO with a rate of ~400events per year, significantly improving the statistics of existing geoneutrinosamples. The JUNO detector is sensitive to several exotic searches, e.g. protondecay via the $p\to K^++\bar\nu$ decay channel. The JUNO detector will providea unique facility to address many outstanding crucial questions in particle andastrophysics. It holds the great potential for further advancing our quest tounderstanding the fundamental properties of neutrinos, one of the buildingblocks of our Universe

Detection of the Diffuse Supernova Neutrino Background with JUNO

As an underground multi-purpose neutrino detector with 20 kton liquid scintillator, Jiangmen Underground Neutrino Observatory (JUNO) is competitive with and complementary to the water-Cherenkov detectors on the search for the diffuse supernova neutrino background (DSNB). Typical supernova models predict 2-4 events per year within the optimal observation window in the JUNO detector. The dominant background is from the neutral-current (NC) interaction of atmospheric neutrinos with 12C nuclei, which surpasses the DSNB by more than one order of magnitude. We evaluated the systematic uncertainty of NC background from the spread of a variety of data-driven models and further developed a method to determine NC background within 15\% with {\it{in}} {\it{situ}} measurements after ten years of running. Besides, the NC-like backgrounds can be effectively suppressed by the intrinsic pulse-shape discrimination (PSD) capabilities of liquid scintillators. In this talk, I will present in detail the improvements on NC background uncertainty evaluation, PSD discriminator development, and finally, the potential of DSNB sensitivity in JUNO

Latest results of the R2D2 project

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Preliminary results of the R2D2 project

The search for neutrinoless double beta decay ($0\nu\beta\beta$) could cast light on one critical piece missing in our knowledge i.e. the nature of the neutrino mass. Its observation is indeed the most sensitive experimental way to prove that neutrino is a Majorana particle. The observation of such a potentially rare process demands a detector with an excellent energy resolution, an extremely low radioactivity and a large mass of emitter isotope. Nowadays many techniques are pursued but none of them meets all the requirements at the same time. The goal of R2D2 is to prove that a spherical high pressure gas TPC filled with xenon could meet all the requirements and provide an ideal detector for the $0\nu\beta\beta$ decay search. The first prototype has demonstrated an excellent resolution with argon meeting the expectations and independently on the particle track's length. In the presented talk the first R2D2 results are discussed as well as the project roadmap and future developments.