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TOPIC: Neutrinos
Blobrana


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RE: Neutrinos
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Title: Neutrino masses from a three-quanton model with spin-spin force and its relation to the gravitational coupling G_N
Authors: Hans-Peter Morsch

Based on a generalisation of quantum electrodynamics with massless elementary fermions (quantons, q) and scalar coupling of gauge bosons, neutrinos are described as composite particles of (q^o bar q^o q^o)-structure bound by a magnetic spin-spin interaction. Combining results from application of a vacuum potential sum rule with deduced mass square differences from neutrino oscillations, neutrino masses of about 0.015 eV, 0.017 eV, and 0.052 eV have been deduced for nu_e, nu_mu, and nu_tau, respectively. The electron has a similar (q^o bar q^oq^-)-structure, leading to a direct relation between the masses of electron and \nu_e, which is used as consistency test of the deduced neutrino masses. The strength of the magnetic spin-spin interaction is found to be a factor ~10^15 smaller than the 'electric' interaction between charged quantons. Together with the reduction of the coupling strength alpha from microscopic systems to a distance of ~0.5 m by a factor of ~2 10^-24, the magnetic spin-spin coupling is consistent with the gavitational coupling G_N. Thus, a unified description of fundamental forces appears possible.

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Blobrana


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Title: Discovery of two neutrino mass eigenstates from SN 1987A
Authors: Robert Ehrlich

This paper reports a new analysis of the neutrino burst detected from SN 1987 A, and it reveals the presence of two mass eigenstates. The heavier mass eigenstate has m_H²=1264 ^{+435}_{-227} eV²/c4 which is 5.6 \sigma from zero, while the lighter mass eigenstate has M_L²=44 ±20eV²/c4. Neither would appear to be superluminal, but this is not entirely unambiguous for the lighter eigenstate.

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Blobrana


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Title: Apparent faster than light propagation from light sterile neutrinos
Authors: Steen Hannestad, Martin S. Sloth

Recent data from the OPERA experiment seem to point to neutrinos propagating faster than light. One possible physics explanation for such a result is the existence of light sterile neutrinos which can propagate in a higher dimensional bulk and achieve apparent superluminal velocities when measured by an observer confined to the 4D brane of the standard model. Such a model has the advantage of easily being able to explain the non-observation of superluminal neutrinos from SN1987A. Here we discuss the phenomenological implications of such a model and show that it can provide an explanation for the observed faster than light propagation of neutrinos.

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Blobrana


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Title: Neutrino mass from higher than d=5 effective operators in SUSY, and its test at the LHC
Authors: Martin B. Krauss, Toshihiko Ota, Werner Porod, Walter Winter

We discuss neutrino masses from higher than d=5 effective operators in a supersymmetric framework, where we explicitly demonstrate which operators could be the leading contribution to neutrino mass in the MSSM and NMSSM. As an example, we focus on the d=7 operator L L H_u H_u H_d H_u, for which we systematically derive all tree-level decompositions. We argue that many of these lead to a linear or inverse see-saw scenario with two extra neutral fermions, where the lepton number violating term is naturally suppressed by a heavy mass scale when the extra mediators are integrated out. We choose one example, for which we discuss possible implementations of the neutrino flavor structure. In addition, we show that the heavy mediators, in this case SU(2) doublet fermions, may indeed be observable at the LHC, since they can be produced by Drell-Yan processes and lead to displaced vertices when they decay. However, the direct observation of lepton number violating processes is on the edge at LHC.

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Blobrana


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Title: Measurement of neutrino velocity with the MINOS detectors and NuMI neutrino beam
Authors: MINOS Collaboration: P. Adamson, et al
(31 Aug 2007, version v3)

The velocity of a ~3 GeV neutrino beam is measured by comparing detection times at the Near and Far detectors of the MINOS experiment, separated by 734 km. A total of 473 Far Detector neutrino events was used to measure (v-c)/c = 5.1 ±2.9 x 10^-5 (at 68% C.L.). By correlating the measured energies of 258 charged-current neutrino events to their arrival times at the Far Detector, a limit is imposed on the neutrino mass of m_nu < 50 MeV/c^2 (99% C.L.).

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Blobrana


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Posts: 131433
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Solar Neutrinos
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Title: Combined Analysis of all Three Phases of Solar Neutrino Data from the Sudbury Neutrino Observatory
Authors: SNO Collaboration: B. Aharmim, S. N. Ahmed, A. E. Anthony, N. Barros, E. W. Beier, A. Bellerive, B. Beltran, M. Bergevin, S. D. Biller, K. Boudjemline, M. G. Boulay, B. Cai, Y. D. Chan, D. Chauhan, M. Chen, B. T. Cleveland, G. A. Cox, X. Dai, H. Deng, J. A. Detwiler, M. DiMarco, P. J. Doe, G. Doucas, P.-L. Drouin, F. A. Duncan, M. Dunford, E. D. Earle, S. R. Elliott, H. C. Evans, G. T. Ewan, J. Farine, H. Fergani, F. Fleurot, R. J. Ford, J. A. Formaggio, N. Gagnon, J. TM. Goon, K. Graham, E. Guillian, S. Habib, R. L. Hahn, A. L. Hallin, E. D. Hallman, P. J. Harvey, R. Hazama, W. J. Heintzelman, J. Heise, R. L. Helmer, A. Hime, C. Howard, M. Huang, P. Jagam, B. Jamieson, N. A. Jelley, M. Jerkins, K. J. Keeter, J. R. Klein, L. L. Kormos, M. Kos, C. Kraus, C. B. Krauss, A Kruger, T. Kutter, et al. (60 additional authors not shown)

We report results from a combined analysis of solar neutrino data from all phases of the Sudbury Neutrino Observatory. By exploiting particle identification information obtained from the proportional counters installed during the third phase, this analysis improved background rejection in that phase of the experiment. The combined analysis resulted in a total flux of active neutrino flavours from 8B decays in the Sun of (5.25 ±0.16(stat.)+0.11-0.13(syst.)) x 10^6 cm^{-2}s^{-1}. A two-flavour neutrino oscillation analysis yielded \Deltam^2_{21} = (5.6^{+1.9}_{-1.4}) x 10^{-5} eV^2 and tan^2{\theta}_{12}= 0.427^{+0.033}_{-0.029}. A three-flavour neutrino oscillation analysis combining this result with results of all other solar neutrino experiments and the KamLAND experiment yielded \Deltam^2_{21} = (7.41^{+0.21}_{-0.19}) x 10^{-5} eV^2, tan^2{\theta}_{12} = 0.446^{+0.030}_{-0.029}, and sin^2{\theta}_{13} = (2.5^{+1.8}_{-1.5}) x 10^{-2}. This implied an upper bound of sin^2{\theta}_{13} < 0.053 at the 95% confidence level (C.L.).

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Blobrana


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Title: Effect of Collective Neutrino Oscillations on the Neutrino Mechanism of Core-Collapse Supernovae
Authors: Ondrej Pejcha, Basudeb Dasgupta, Todd A. Thompson

In the seconds after collapse of a massive star, the newborn proto-neutron star (PNS) radiates neutrinos of all flavours. The absorption of electron-type neutrinos below the radius of the stalled shockwave may drive explosions (the "neutrino mechanism"). Because the heating rate is proportional to the neutrino energy, flavour conversion of higher-energy mu and tau neutrinos to electron-type neutrinos via collective neutrino oscillations (CnuO) can increase the heating rate, and potentially drive explosions. We solve the steady-state boundary value problem of spherically-symmetric accretion between the PNS surface (r_nu) and the shock (r_S), for the first time including a scheme for flavour conversion via CnuO. For a given r_nu, PNS mass (M), and accretion rate (Mdot), we calculate the critical neutrino luminosity above which accretion is impossible and explosion results. We show that CnuO decreases the critical luminosity by a factor of ~1.5, but only if the flavour conversion is fully completed inside r_S. The effect is smaller for partial conversion. The shock radius and the physical scale for flavour conversion depend differently on the parameters of the problem. We quantify these dependencies and find that CnuO lowers the critical luminosity substantially for small M and Mdot, and large r_nu. Thus, CnuO can be important for shockwave revival if PNSs contract slowly, which may favour a stiff nuclear equation of state, and if progenitors reach low Mdot at early times after collapse, which favours the lowest-mass massive stars.

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Blobrana


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Fermilab experiment weighs in on neutrino mystery

Scientists of the MINOS experiment at the Department of Energy's Fermi National Accelerator Laboratory announced today (June 24) the results from a search for a rare phenomenon, the transformation of muon neutrinos into electron neutrinos. The result is consistent with and significantly constrains a measurement reported 10 days ago by the Japanese T2K experiment, which announced an indication of this type of transformation.
The results of these two experiments could have implications for our understanding of the role that neutrinos may have played in the evolution of the universe. If muon neutrinos transform into electron neutrinos, neutrinos could be the reason that the big bang produced more matter than antimatter, leading to the universe as it exists today.
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Blobrana


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Indication of Electron Neutrino Appearance at the T2K Experiment

The T2K experiment, whose primary purpose is to study neutrino interactions at a large distance from their source, has detected 6 electron neutrino candidate events based on the data collected before March 11, 2011. For the first time, it was possible to observe an indication that muon neutrinos are able to transform into electron neutrinos over a distance of 295 km through the quantum mechanical phenomena of neutrino flavour oscillations.
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Blobrana


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Neutrino particle 'flips to all flavours'

An important breakthrough may be imminent in the study of neutrinos.
The multinational T2K project in Japan says it has seen indications in its data that these elementary particles can flip to any of their three types.
The results are provisional because experiments had to be suspended in the wake of the Tohoku earthquake in March.
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