Models of Neutrino Masses and Mixings

We review theoretical ideas, problems and implications of neutrino masses and mixing angles. We give a general discussion of schemes with three light neutrinos. Several specific examples are analyzed in some detail, particularly those that can be embedded into grand unified theories.Comment: 44 pages, 2 figures, version accepted for publication on the Focus Issue on 'Neutrino Physics' edited by F.Halzen, M.Lindner and A. Suzuki, to be published in New Journal of Physics

Status of global fits to neutrino oscillations

We review the present status of global analyses of neutrino oscillations, taking into account the most recent neutrino data including the latest KamLAND and K2K updates presented at Neutrino2004, as well as state-of-the-art solar and atmospheric neutrino flux calculations. We give the two-neutrino solar + KamLAND results, as well as two-neutrino atmospheric + K2K oscillation regions, discussing in each case the robustness of the oscillation interpretation against departures from the Standard Solar Model and the possible existence of non-standard neutrino physics. Furthermore, we give the best fit values and allowed ranges of the three-flavour oscillation parameters from the current worlds' global neutrino data sample and discuss in detail the status of the small parameters \alpha \equiv \Dms/\Dma as well as $\sin^2\theta_{13}$, which characterize the strength of CP violating effects in neutrino oscillations. We also update the degree of rejection of four-neutrino interpretations of the LSND anomaly in view of the most recent developments.Comment: v6: In the last Appendix we provide updated neutrino oscillation results which take into account the relevant oscillation data released by the MINOS and KamLAND collaboration

The ICECUBE prototype string in AMANDA

The Antarctic Muon And Neutrino Detector Array (Amanda) is a high-energy neutrino telescope. It is a lattice of optical modules (OM) installed in the clear ice below the South Pole Station. Each OM contains a photomultiplier tube (PMT) that detects photons of Cherenkov light generated in the ice by muons and electrons. IceCube is a cubic-kilometer-sized expansion of Amanda currently being built at the South Pole. In IceCube the PMT signals are digitized already in the optical modules and transmitted to the surface. A prototype string of 41 OMs equipped with this new all-digital technology was deployed in the Amanda array in the year 2000. In this paper we describe the technology and demonstrate that this string serves as a proof of concept for the IceCube array. Our investigations show that the OM timing accuracy is 5 ns. Atmospheric muons are detected in excellent agreement with expectations with respect to both angular distribution and absolute rate

Type II See-Saw at Collider, Lepton Asymmetry and Singlet Scalar Dark Matter.

We propose an extension of the standard model with a B–L global symmetry that is broken softly at the TeV scale. The neutrinos acquire masses through a type-II seesaw while the lepton (L) asymmetry arises in the singlet sector but without B–L-number violation. The model has the virtue that the scale of L-number violation (Λ) giving rise to neutrino masses is independent of the scale of leptogenesis (Λ'). As a result the model can explain neutrino masses, singlet scalar dark matter and leptogenesis at the TeV scale. The stability of the dark matter is ensured by a surviving Z2 symmetry, which could be lifted at the Planck scale, thereby allowing Planck scale suppressed decay of singlet scalar dark matter particles of mass 3 MeV to e+e- pairs in the Galactic halo. The model also predicts a few hundred GeV doubly charged scalar and a long-lived charged fermion, whose decay can be studied at the Large Hadron Collider (LHC) and International Linear Collider (ILC)

Five Years of Searches for Point Sources of Astrophysical Neutrinos with the AMANDA-II Neutrino Telescope.

We report the results of a five-year survey of the northern sky to search for point sources of high energy neutrinos. The search was performed on the data collected with the AMANDA-II neutrino telescope in the years 2000 to 2004, with a live-time of 1001 days. The sample of selected events consists of 4282 upward going muon tracks with high reconstruction quality and an energy larger than about 100 GeV. We found no indication of point sources of neutrinos and set 90% confidence level flux upper limits for an all-sky search and also for a catalog of 32 selected sources. For the all-sky search, our average (over declination and right ascension) experimentally observed upper limit \Phi^{0}=(E/TeV)^\gamma d\Phi/dE to a point source flux of muon and tau neutrino (detected as muons arising from taus) is \Phi_{\nu_\mu}^{0} + \Phi_{\nu_\tau}^{0} = 11.1 x 10^{-11} TeV^-1 cm^-2 s^-1, in the energy range between 1.6 TeV and 2.5 PeV for a flavor ratio \Phi_{\nu_\mu}^{0} / \Phi_{\nu_\tau}^{0}= 1 and assuming a spectral index \gamma=2. It should be noticed that this is the first time we set upper limits to the flux of muon and tau neutrinos. In previous papers we provided muon neutrino upper limits only neglecting the sensitivity to a signal from tau neutrinos, which improves the limits by 10% to 16%. The value of the average upper limit presented in this work corresponds to twice the limit on the muon neutrino flux \Phi_{\nu_\mu}^{0} = 5.5 \cdot 10^{-11} TeV^-1 cm^-2 s^-1. A stacking analysis for preselected active galactic nuclei and a search based on the angular separation of the events were also performed. We report the most stringent flux upper limits to date, including the results of a detailed assessment of systematic uncertainties.Comment: 32 pages, 9 figures, submitted to Phys. Rev.

Search for Neutrino-Induced Cascades From Gamma-Ray Bursts with AMANDA.

Using the neutrino telescope AMANDA-II, we have conducted two analyses searching for neutrino-induced cascades from gamma-ray bursts. No evidence of astrophysical neutrinos was found, and limits are presented for several models. We also present neutrino effective areas which allow the calculation of limits for any neutrino production model. The first analysis looked for a statistical excess of events within a sliding window of 1 or 100 s (for short and long burst classes, respectively) during the years 2001-2003. The resulting upper limit on the diffuse flux normalization times .E2 for the Waxman-Bahcall model at 1 PeVis 1.6 × 10-6 GeV cm-2 s-1 sr-1 (a factor of 120 above the theoretical prediction). For this search 90% of the neutrinos would fall in the energy range 50 TeV to 7 PeV. The second analysis looked for neutrino-induced cascades in coincidence with 73 bursts detected by BATSE in the year 2000. The resulting upper limit on the diffuse flux normalization times E2, also at 1 PeV, is 1.5 × 10-6 GeV cm-2 s-1 sr-1 (a factor of 110 above the theoretical prediction) for the same energy range. The neutrino-induced cascade channel is complementary to the up-going muon channel, We comment on its advantages for searches of neutrinos from GRBs and its future use with IceCube. © 2007. The American Astronomical Society. All rights reserved.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe