Bose–Einstein correlations of pairs of identical charged pions produced in hadronic Z decays are analyzed in terms of various parametrizations. A good description is achieved using a Lévy stable distribution in conjunction with a model where a particle’s momentum is correlated with its space–time point of production, the τ-model. Using this description and the measured rapidity and transverse momentum distributions, the space–time evolution of particle emission in two-jet events is reconstructed. However, the elongation of the particle emission region previously observed is not accommodated in the τ-model, and this is investigated using an ad hoc modification.

We present results from a study of hadronic event structure in high energy e+e− interactions using the L3 detector at LEP. A new class of event shape distributions are measured at and above the Z boson pole for light quark (u, d, s, c) flavours. Energy flow correlations are studied for all hadronic events. Next-to-leading-log QCD calculations and QCD models with improved leading-log approximations are compared to data and good agreement is found at the Z-pole whereas some discrepancies are observed at higher centre-of-mass energies.

A search for neutron-antineutron ($n-\bar{n}$) oscillation was undertaken in Super-Kamiokande using the 1489 live-day or $2.45 \times 10^{34}$ neutron-year exposure data. This process violates both baryon and baryon minus lepton numbers by an absolute value of two units and is predicted by a large class of hypothetical models where the seesaw mechanism is incorporated to explain the observed tiny neutrino masses and the matter-antimatter asymmetry in the Universe. No evidence for $n-\bar{n}$ oscillation was found, the lower limit of the lifetime for neutrons bound in ${}^{16}$O, in an analysis that included all of the significant sources of experimental uncertainties, was determined to be $1.9 \times 10^{32}$~years at the 90\% confidence level. The corresponding lower limit for the oscillation time of free neutrons was calculated to be $2.7 \times 10^8$~s using a theoretical value of the nuclear suppression factor of $0.517 \times 10^{23}$~s$^{-1}$ and its uncertainty.

A first study of neutron tagging is conducted in Super-Kamiokande, a 50,000 ton water Cherenkov detector, The tagging efficiencies of thermal neutrons are evaluated in a 0.2% GdCl3-water solution and pure water. They are determined to be, respectively, 66.7% for events above 3 MeV and 20% with corresponding background probabilities of 2 x 10(-4) and 3 x 10(-2). This newly developed technique may enable water Cherenkov detectors to identify (nu) over bar (e)'s from astrophysical sources as well as those produced by commercial reactors via the delayed coincidence scheme. (C) 2009 Elsevier B.V. All rights reserved.

The atmospheric neutrino background for proton decay via p -> e(+)pi(0) in ring imaging water Cherenkov detectors is studied with an artificial accelerator neutrino beam for the first time. In total, 3.14x10(5) neutrino events corresponding to about 10 megaton-years of atmospheric neutrino interactions were collected by a 1000 ton water Cherenkov detector (KT). The KT charged-current single pi(0) production data are well reproduced by simulation programs of neutrino and secondary hadronic interactions used in the Super-Kamiokande (SK) proton decay search. The obtained p -> e(+)pi(0) background rate by the KT data for SK from the atmospheric neutrinos whose energies are below 3 GeV is 1.63(-0.33)(+0.42)(stat)(-0.51)(+0.45)(syst)(megaton-year)(-1). This result is also relevant to possible future, megaton-scale water Cherenkov detectors.

A subset of neutrino-induced upward through-going muons in the Super-Kamiokande detector consists of high energy muons which lose energy through radiative processes such as bremsstrahlung, e^+ e^- pair production and photonuclear interactions. These “upward showering muons” comprise an event sample whose mean parent neutrino energy is approximately 1 TeV. We show that the zenith angle distribution of upward showering muons is consistent with negligible distortion due to neutrino oscillations, as expected of such a high-energy neutrino sample. We present astronomical searches using these high energy events, such as those from WIMP annihilations in the Sun, Earth and Galactic Center, some suspected point sources, as well as searches for diffuse flux from the interstellar medium.

We consider {nu}{sub {mu}}{yields}{nu}{sub {tau}} oscillations in the context of the mass varying neutrino (MaVaN) model, where the neutrino mass can vary depending on the electron density along the flight path of the neutrino. Our analysis assumes a mechanism with dependence only upon the electron density, hence ordinary matter density, of the medium through which the neutrino travels. Fully-contained, partially-contained and upward-going muon atmospheric neutrino data from the Super-Kamiokande detector, taken from the entire SK-I period of 1489 live days, are compared to MaVaN model predictions. We find that, for the case of 2-flavor oscillations, and for the specific models tested, oscillation independent of electron density is favored over density dependence. Assuming maximal mixing, the best-fit case and the density-independent case do not differ significantly.

Single charged pion production in charged-current muon neutrino interactions with carbon is studied using data collected in the K2K long-baseline neutrino experiment. The mean energy of the incident muon neutrinos is 1.3 GeV. The data used in this analysis are mainly from a fully active scintillator detector, SciBar. The cross section for single pi(+) production in the resonance region (W < 2 GeV/c(2)) relative to the charged-current quasielastic cross section is found to be 0.734(-0.153)(+0.140). The energy-dependent cross section ratio is also measured. The results are consistent with a previous experiment and the prediction of our model.

The (KSK +/-)-K-0 pi(-/+) final state in two-photon collisions is studied with the L3 detector at LEP at e(+)e(-) centre- of- mass energies from 183 to 209 GeV with an integrated luminosity of 664.6 pb(-1). The eta (1475) and f(1)(1420) mesons are observed and their contribution is separated by measuring the formation rates as a function of the photon virtuality Q(2). The eta(1475) is found to be dominant for Q(2) <= 0.01 GeV2 and its two- photon width is measured to be 0.23 +/- 0.05 (stat.) +/- 0.05 (sys.) keV. At higher Q(2), the f(1)(1420) is formed and decays to K*(892) K. The coupling and form factor parameters of this state are measured to be Gamma(gamma gamma) = 3.2 +/- 0.6 (stat.) +/- 0.7 ( sys.) keV and Lambda(1) = 926 +/- 72 (stat.) +/- 32 (sys.) MeV, respectively.

Measurements of inclusive production of the Lambda, Xi- and Xi*(1530) baryons in two-photon collisions with the L3 detector at LEP are presented. The inclusive differential cross sections for Lambda and Xi- are measured as a function of the baryon transverse momentum, pt, and pseudo-rapidity, eta. The mean number of Lambda, Xi- and Xi*(1530) baryons per hadronic two-photon event is determined in the kinematic range 0.4 GeV < pt< 2.5 GeV, |eta| < 1.2. Overall agreement with the theoretical models and Monte Carlo predictions is observed. A search for inclusive production of the pentaquark theta+(1540) in two-photon collisions through the decay theta+ -> proton K0s is also presented. No evidence for production of this state is found.

A search for Q-balls has been carried out in Super-Kamiokande II with 541.7 days of live time. A neutral Q-ball passing through the detector can interact with nuclei to produce pions, generating a signal of successive contained pion events along a track. No candidate for successive contained event groups has been found in Super-Kamiokande II, so we obtain upper limits on the flux of such Q-balls.

The reactions gamma gamma ->pi^+pi^-pi^+pi^- and gamma gamma ->pi^+pi^0pi^-pi^0 are studied with the L3 detector at LEP in a data sample collected at centre-of-mass energies from 161GeV to 209GeV with a total integrated luminosity of 698/pb. A spin-parity-helicity analysis of the rho^0 rho^0 and rho^+ rho^- systems for two-photon centre-of-mass energies between 1GeV and 3GeV shows the dominance of the spin-parity state 2+ with helicity 2. The contribution of 0+ and 0- spin-parity states is also observed, whereas contributions of 2- states and of a state with spin-parity 2+ and zero helicity are found to be negligible.

We present measurements of nu(mu) disappearance in K2K, the KEK to Kamioka long-baseline neutrino oscillation experiment. One-hundred and twelve beam-originated neutrino events are observed in the fiducial volume of Super-Kamiokande with an expectation of 158.1(-8.6)(+9.2) events without oscillation. A distortion of the energy spectrum is also seen in 58 single-ring muonlike events with reconstructed energies. The probability that the observations are explained by the expectation for no neutrino oscillation is 0.0015% (4.3 sigma). In a two-flavor oscillation scenario, the allowed Delta m(2) region at sin(2)2 theta=1 is between 1.9 and 3.5x10(-3) eV(2) at the 90% C.L. with a best-fit value of 2.8x10(-3) eV(2).

We performed an improved search for ${\ensuremath{\nu}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{e}$ oscillation with the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment, using the full data sample of $9.2\ifmmode\times\else\texttimes\fi{}{10}^{19}$ protons on target. No evidence for a ${\ensuremath{\nu}}_{e}$ appearance signal was found, and we set bounds on the ${\ensuremath{\nu}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{e}$ oscillation parameters. At $\ensuremath{\Delta}{m}^{2}=2.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\text{ }\text{ }{\mathrm{eV}}^{2}$, the best-fit value of the K2K ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ disappearance analysis, we set an upper limit of ${sin}^{2}2{\ensuremath{\theta}}_{\ensuremath{\mu}e}<0.13$ at a 90% confidence level.

The weak nucleon axial-vector form factor for quasielastic interactions is determined using neutrino interaction data from the K2K Scintillating Fiber detector in the neutrino beam at KEK. More than 12 000 events are analyzed, of which half are charged-current quasielastic interactions nu(mu)n ->mu(-)p occurring primarily in oxygen nuclei. We use a relativistic Fermi gas model for oxygen and assume the form factor is approximately a dipole with one parameter, the axial-vector mass M-A, and fit to the shape of the distribution of the square of the momentum transfer from the nucleon to the nucleus. Our best fit result for M-A=1.20 +/- 0.12 GeV. Furthermore, this analysis includes updated vector form factors from recent electron scattering experiments and a discussion of the effects of the nucleon momentum on the shape of the fitted distributions.

We performed an improved search for nu(mu) --> nu(e) oscillation with the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment, using the full data sample of 9.2 x 10(19) protons on target. No evidence for a nu(e) appearance signal was found, and we set bounds on the nu(mu) --> nu(e) oscillation parameters. At Deltam(2)=2.8 x 10(-3) eV(2), the best-fit value of the K2Knu(mu) disappearance analysis, we set an upper limit of sin(2)2theta(mue) < 0.13 at a 90% confidence level.