214 research outputs found
Solar neutrino oscillations and bounds on neutrino magnetic moment and solar magnetic field
If the observed deficit of solar neutrinos is due to neutrino oscillations,
neutrino conversions caused by the interaction of their transition magnetic
moments with the solar magnetic field (spin-flavour precession) can still be
present at a subdominant level. In that case, the combined action of neutrino
oscillations and spin-flavour precession can lead to a small but observable
flux of electron antineutrinos coming from the sun. Non-observation of these
nuebar's could set limits on neutrino transition moment \mu and the strength
and coordinate dependence of the solar magnetic field B_\perp. The sensitivity
of the nuebar flux to the product \mu B_\perp is strongest in the case of the
vacuum oscillation (VO) solution of the solar neutrino problem; in the case of
the LOW solution, it is weaker, and it is the weakest for the LMA solution. For
different solutions, different characteristics of the solar magnetic field
B_\perp(r) are probed: for the VO solution, the nuebar flux is determined by
the integral of B_\perp(r) over the solar convective zone, for LMA it is
determined by the magnitude of B_\perp in the neutrino production region, and
for LOW it depends on the competition between this magnitude and the derivative
of B_\perp(r) at the surface of the sun.Comment: LaTeX, 16 pages, 2 eps figures. References added; discussion of the
LOW case modifie
Self-shielding effect of a single phase liquid xenon detector for direct dark matter search
Liquid xenon is a suitable material for a dark matter search. For future
large scale experiments, single phase detectors are attractive due to their
simple configuration and scalability. However, in order to reduce backgrounds,
they need to fully rely on liquid xenon's self-shielding property. A prototype
detector was developed at Kamioka Observatory to establish vertex and energy
reconstruction methods and to demonstrate the self-shielding power against
gamma rays from outside of the detector. Sufficient self-shielding power for
future experiments was obtained.Comment: 8 pages, 8 figure
Measurement of single pi0 production in neutral current neutrino interactions with water by a 1.3 GeV wide band muon neutrino beam
Neutral current single pi0 production induced by neutrinos with a mean energy
of 1.3 GeV is measured at a 1000 ton water Cherenkov detector as a near
detector of the K2K long baseline neutrino experiment. The cross section for
this process relative to the total charged current cross section is measured to
be 0.064 +- 0.001 (stat.) +- 0.007 (sys.). The momentum distribution of
produced pi0s is measured and is found to be in good agreement with an
expectation from the present knowledge of the neutrino cross sections.Comment: 6 pages, 4 figures, Submitted to Phys. Lett.
Solar neutrino results in Super-Kamiokande-III
The results of the third phase of the Super-Kamiokande solar neutrino
measurement are presented and compared to the first and second phase results.
With improved detector calibrations, a full detector simulation, and improved
analysis methods, the systematic uncertainty on the total neutrino flux is
estimated to be ?2.1%, which is about two thirds of the systematic uncertainty
for the first phase of Super-Kamiokande. The observed 8B solar flux in the 5.0
to 20 MeV total electron energy region is 2.32+/-0.04 (stat.)+/-0.05 (sys.)
*10^6 cm^-2sec^-1, in agreement with previous measurements. A combined
oscillation analysis is carried out using SK-I, II, and III data, and the
results are also combined with the results of other solar neutrino experiments.
The best-fit oscillation parameters are obtained to be sin^2 {\theta}12 =
0.30+0.02-0.01(tan^2 {\theta}12 = 0.42+0.04 -0.02) and {\Delta}m2_21 =
6.2+1.1-1.9 *10^-5eV^2. Combined with KamLAND results, the best-fit oscillation
parameters are found to be sin^2 {\theta}12 = 0.31+/-0.01(tan^2 {\theta}12 =
0.44+/-0.03) and {\Delta}m2_21 = 7.6?0.2*10^-5eV^2 . The 8B neutrino flux
obtained from global solar neutrino experiments is
5.3+/-0.2(stat.+sys.)*10^6cm^-2s^-1, while the 8B flux becomes
5.1+/-0.1(stat.+sys.)*10^6cm^-2s^-1 by adding KamLAND result. In a three-flavor
analysis combining all solar neutrino experiments, the upper limit of sin^2
{\theta}13 is 0.060 at 95% C.L.. After combination with KamLAND results, the
upper limit of sin^2 {\theta}13 is found to be 0.059 at 95% C.L..Comment: 19 pages, 33 figures in the main text. The appendix section on errata
is added in v
Search for Electron Neutrino Appearance in a 250 km Long-baseline Experiment
We present a search for electron neutrino appearance from accelerator
produced muon neutrinos in the K2K long baseline neutrino experiment. One
candidate event is found in the data corresponding to an exposure of 4.8*10^19
protons on target. The expected background in the absence of neutrino
oscillations is estimated to be 2.4+-0.6 events and is dominated by
mis-identification of events from neutral current pi^0 production. We exclude
the \nu_\mu to \nu_e oscillations at 90% C.L. for the effective mixing angle in
2-flavor approximation of sin^2(2theta_\mu_e) (~= 1/2 sin^2 2 th_13) > 0.15 at
Delta m^2_\mu_e = 2.8*10^{-3} eV^2, the best fit value of the \nu_\mu
disappearance analysis in K2K. The most stringent limit of sin^2(2theta_\mu_e)
< 0.09 is obtained at Delta m^2_\mu_e = 6*10^{-3} eV^2.Comment: 5 pages with 2 figures embeded in two column revtex4 style. Accepted
to be published in Phys. Rev. Let
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 ,
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
Study of Non-Standard Neutrino Interactions with Atmospheric Neutrino Data in Super-Kamiokande I and II
In this paper we study non-standard neutrino interactions as an example of
physics beyond the standard model using atmospheric neutrino data collected
during the Super-Kamiokande I(1996-2001) and II(2003-2005) periods. We focus on
flavor-changing-neutral-currents (FCNC), which allow neutrino flavor
transitions via neutral current interactions, and effects which violate lepton
non-universality (NU) and give rise to different neutral-current
interaction-amplitudes for different neutrino flavors. We obtain a limit on the
FCNC coupling parameter, varepsilon_{mu tau}, |varepsilon_{mu tau}|<1.1 x
10^{-2} at 90%C.L. and various constraints on other FCNC parameters as a
function of the NU coupling, varepsilon_{e e}. We find no evidence of
non-standard neutrino interactions in the Super-Kamiokande atmospheric data.Comment: 12 Pages, 14 figures. To be submitted to Phys. Rev.
Evidence for the Appearance of Atmospheric Tau Neutrinos in Super-Kamiokande
Super-Kamiokande atmospheric neutrino data were fit with an unbinned maximum
likelihood method to search for the appearance of tau leptons resulting from
the interactions of oscillation-generated tau neutrinos in the detector.
Relative to the expectation of unity, the tau normalization is found to be
1.42 \pm 0.35 \ (stat) {\}^{+0.14}_{-0.12}\ (syst) excluding the
no-tau-appearance hypothesis, for which the normalization would be zero, at the
3.8 level. We estimate that 180.1 \pm 44.3\ (stat)
{\}^{+17.8}_{-15.2}\ (syst) tau leptons were produced in the 22.5 kton
fiducial volume of the detector by tau neutrinos during the 2806 day running
period. In future analyses, this large sample of selected tau events will allow
the study of charged current tau neutrino interaction physics with oscillation
produced tau neutrinos.Comment: 7 pages, 4 figures. This is the version as published in Physical
Review Letters including the supplemental figure. A typographical error in
the description of figure 3 is also correcte
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