Three-flavor solar neutrino oscillations with terrestrial neutrino constraints

We present an updated analysis of the current solar neutrino data in terms of three-flavor oscillations, including the additional constraints coming from terrestrial neutrino oscillation searches at the CHOOZ (reactor), Super-Kamiokande (atmospheric), and KEK-to-Kamioka (accelerator) experiments. The best fit is reached for the subcase of two-family mixing, and the additional admixture with the third neutrino is severely limited. We discuss the relevant features of the globally allowed regions in the oscillation parameter space, as well as their impact on the amplitude of possible CP-violation effects at future accelerator experiments and on the reconstruction accuracy of the mass-mixing oscillation parameters at the KamLAND reactor experiment.Comment: 10 pages + 8 figure

Three-generation flavor transitions and decays of supernova relic neutrinos

If neutrinos have mass, they can also decay. Decay lifetimes of cosmological interest can be probed, in principle, through the detection of the redshifted, diffuse neutrino flux produced by all past supernovae--the so-called supernova relic neutrino (SRN) flux. In this work, we solve the SRN kinetic equations in the general case of three-generation flavor transitions followed by invisible (nonradiative) two-body decays. We then use the general solution to calculate observable SRN spectra in some representative decay scenarios. It is shown that, in the presence of decay, the SRN event rate can basically span the whole range below the current experimental upper bound--a range accessible to future experimental projects. Radiative SRN decays are also briefly discussed.Comment: 25 pages, including 7 figure

Structure of the ovaries of the Nimba otter shrew, Micropotamogale lamottei, and the Madagascar hedgehog tenrec, Echinops telfairi

The otter shrews are members of the subfamily Potamogalinae within the family Tenrecidae. No description of the ovaries of any member of this subfamily has been published previously. The lesser hedgehog tenrec, Echinops telfairi, is a member of the subfamily Tenrecinae of the same family and, although its ovaries have not been described, other members of this subfamily have been shown to have ovaries with non-antral follicles. Examination of these two species illustrated that non-antral follicles were characteristic of the ovaries of both species, as was clefting and lobulation of the ovaries. Juvenile otter shrews range from those with only small follicles in the cortex to those with 300- to 400-mu m follicles similar to those seen in non-pregnant and pregnant adults. As in other species, most of the growth of the oocyte occurred when follicles had one to two layers of granulosa cells. When larger follicles became atretic in the Nimba otter shrew, hypertrophy of the theca interna produced nodules of glandular interstitial tissue. In the tenrec, the hypertrophying theca interna cells in most large follicles appeared to undergo degeneration. Both species had some follicular fluid in the intercellular spaces between the more peripheral granulosa cells. It is suggested that this fluid could aid in separation of the cumulus from the remaining granulosa at ovulation. The protruding follicles in lobules and absence of a tunica albuginea might also facilitate ovulation of non-antral follicles. Ovaries with a thin-absent tunica albuginea and follicles with small-absent antra are widespread within both the Eulipotyphla and in the Afrosoricida, suggesting that such features may represent a primitive condition in ovarian development. Lobulated and deeply crypted ovaries are found in both groups but are not as common in the Eulipotyphla making inclusion of this feature as primitive more speculative. Copyright (C) 2005 S. Karger AG, Basel

On the Normalization of the Neutrino-Deuteron Cross Section

As is well-known, comparison of the solar neutrino fluxes measured in SuperKamiokande (SK) by $\nu + e^- \to \nu + e^-$ and in the Sudbury Neutrino Observatory (SNO) by $\nu_e + d \to e^- + p + p$ can provide a ``smoking gun'' signature for neutrino oscillations as the solution to the solar neutrino puzzle. This occurs because SK has some sensitivity to all active neutrino flavors whereas SNO can isolate electron neutrinos. This comparison depends crucially on the normalization and uncertainty of the theoretical charged-current neutrino-deuteron cross section. We address a number of effects which are significant enough to change the interpretation of the SK--SNO comparison.Comment: 4 pages, 1 figure, submitted to PR

KamLAND neutrino spectra in energy and time: Indications for reactor power variations and constraints on the georeactor

The Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND) is sensitive to the neutrino event spectrum from (mainly Japanese) nuclear reactors in both the energy domain and the time domain. While the energy spectrum of KamLAND events allows the determination of the neutrino oscillation parameters, the time spectrum can be used to monitor known and unknown neutrino sources. By using available monthly-binned data on event-by-event energies in KamLAND and on reactor powers in Japan, we perform a likelihood analysis of the neutrino event spectra in energy and time, and find significant indications in favor of time variations of the known reactor sources, as compared with the hypothetical case of constant reactor neutrino flux. We also find that the KamLAND data place interesting upper limits on the power of a speculative nuclear reactor operating in the Earth's core (the so-called georeactor); such limits are strengthened by including solar neutrino constraints on the neutrino mass and mixing parameters. Our results corroborate the standard interpretation of the KamLAND signal as due to oscillating neutrinos from known reactor sources.Comment: 22 pages, including 9 figure

Do solar neutrinos decay?

Despite the fact that the solar neutrino flux is now well-understood in the context of matter-affected neutrino mixing, we find that it is not yet possible to set a strong and model-independent bound on solar neutrino decays. If neutrinos decay into truly invisible particles, the Earth-Sun baseline defines a lifetime limit of \tau/m \agt 10^{-4} s/eV. However, there are many possibilities which must be excluded before such a bound can be established. There is an obvious degeneracy between the neutrino lifetime and the mixing parameters. More generally, one must also allow the possibility of active daughter neutrinos and/or antineutrinos, which may partially conceal the characteristic features of decay. Many of the most exotic possibilities that presently complicate the extraction of a decay bound will be removed if the KamLAND reactor antineutrino experiment confirms the large-mixing angle solution to the solar neutrino problem and measures the mixing parameters precisely. Better experimental and theoretical constraints on the $^8$B neutrino flux will also play a key role, as will tighter bounds on absolute neutrino masses. Though the lifetime limit set by the solar flux is weak, it is still the strongest direct limit on non-radiative neutrino decay. Even so, there is no guarantee (by about eight orders of magnitude) that neutrinos from astrophysical sources such as a Galactic supernova or distant Active Galactic Nuclei will not decay.Comment: Very minor corrections, corresponds to published versio

Bounds on the dipole moments of the tau-neutrino via the process e+e−→ννˉγe^{+}e^{-}\rightarrow \nu \bar \nu \gamma in a 331 model

We obtain limits on the anomalous magnetic and electric dipole moments of the $\nu_{\tau}$ through the reaction $e^{+}e^{-}\rightarrow \nu \bar \nu \gamma$ and in the framework of a 331 model. We consider initial-state radiation, and neglect $W$ and photon exchange diagrams. The results are based on the data reported by the L3 Collaboration at LEP, and compare favorably with the limits obtained in other models, complementing previous studies on the dipole moments.Comment: 13 pages, 4 figures, to be published in The European Physical J C. arXiv admin note: substantial text overlap with arXiv:hep-ph/060527

KamLAND Bounds on Solar Antineutrinos and neutrino transition magnetic moments

We investigate the possibility of detecting solar electron antineutrinos with the KamLAND experiment. These electron antineutrinos are predicted by spin-flavor oscillations at a significant rate even if this mechanism is not the leading solution to the SNP. KamLAND is sensitive to antineutrinos originated from solar ${}^8$B neutrinos. From KamLAND negative results after 145 days of data taking, we obtain model independent limits on the total flux of solar electron antineutrinos $\Phi({}^8 B)< 1.1-3.5\times 10^4 cm^{-2}\ s^{-1}$, more than one order of magnitude smaller than existing limits, and on their appearance probability$P<0.15%$(95antineutrino production by spin-flavor precession, this upper bound implies an upper limit on the product of the intrinsic neutrino magnetic moment and the value of the solar magnetic field$\mu B< 2.3\times 10^{-21}$MeV 95LMA$(\Delta m^2, \tan^2\theta)$values). Limits on neutrino transition moments are also obtained. For realistic values of other astrophysical solar parameters these upper limits would imply that the neutrino magnetic moment is constrained to be, in the most conservative case,$\mu\lsim 3.9\times 10^{-12} \mu_B$(95CL) for a relatively small field$B= 50$kG. For higher values of the magnetic field we obtain:$\mu\lsim 9.0\times 10^{-13} \mu_B$for field$B= 200$kG and$\mu\lsim 2.0\times 10^{-13} \mu_B$for field$B= 1000$ kG at the same statistical significance.Comment: 13 pages, 2 figure

KamLAND, solar antineutrinos and the solar magnetic field

In this work the possibility of detecting solar electron antineutrinos produced by a solar core magnetic field from the KamLAND recent observations is investigated. We find a scaling of the antineutrino probability with respect to the magnetic field profile in the sense that the same probability function can be reproduced by any profile with a suitable peak field value. In this way the solar electron antineutrino spectrum can be unambiguosly predicted. We use this scaling and the negative results indicated by the KamLAND experiment to obtain upper bounds on the solar electron antineutrino flux. We get $\phi_{\bar\nu}<3.8\times 10^{-3}\phi(^8B)$ at 95% CL. For 90% CL this becomes $\phi_{\bar\nu}<3.4\times 10^{-3}\phi(^8B)$, an improvement by a factor of 3-5 with respect to existing bounds. These limits are independent of the detailed structure of the magnetic field in the solar interior. We also derive upper bounds on the peak field value which are uniquely determined for a fixed solar field profile. In the most efficient antineutrino producing case, we get (95% CL) an upper limit on the product of the neutrino magnetic moment by the solar field $\mu B< 2.8\times 10^{-19}$ MeV or $B_0 \leq 4.9 \times 10^7 G$ for $\mu_\nu=10^{-12}\mu_B$.Comment: 15 pages. References corrected. Minor changes in the tex

Common Origin of Soft mu-tau and CP Breaking in Neutrino Seesaw and the Origin of Matter

Neutrino oscillation data strongly support mu-tau symmetry as a good approximate flavor symmetry of the neutrino sector, which has to appear in any viable theory for neutrino mass-generation. The mu-tau breaking is not only small, but also the source of Dirac CP-violation. We conjecture that both discrete mu-tau and CP symmetries are fundamental symmetries of the seesaw Lagrangian (respected by interaction terms), and they are only softly broken, arising from a common origin via a unique dimension-3 Majorana mass-term of the heavy right-handed neutrinos. From this conceptually attractive and simple construction, we can predict the soft mu-tau breaking at low energies, leading to quantitative correlations between the apparently two small deviations \theta_{23} - 45^o and \theta_{13} - 0^o. This nontrivially connects the on-going measurements of mixing angle \theta_{23} with the upcoming experimental probes of \theta_{13}. We find that any deviation of \theta_{23} - 45^o must put a lower limit on \theta_{13}. Furthermore, we deduce the low energy Dirac and Majorana CP violations from a common soft-breaking phase associated with mu-tau breaking in the neutrino seesaw. Finally, from the soft CP breaking in neutrino seesaw we derive the cosmological CP violation for the baryon asymmetry via leptogenesis. We fully reconstruct the leptogenesis CP-asymmetry from the low energy Dirac CP phase and establish a direct link between the cosmological CP-violation and the low energy Jarlskog invariant. We predict new lower and upper bounds on the \theta_{13} mixing angle, 1^o < \theta_{13} < 6^o. In addition, we reveal a new hidden symmetry that dictates the solar mixing angle \theta_12 by its group-parameter, and includes the conventional tri-bimaximal mixing as a special case, allowing deviations from it.Comment: 60pp, JCAP in Press, v2: only minor stylistic refinements (added Daya Bay's future sensitivity in Figs.2+8, shortened some eqs, added new Appendix-A and some references), comments are welcome