Limits on the neutrino magnetic moment from the MUNU experiment

The MUNU experiment was carried out at the Bugey nuclear power reactor. The aim was the study of electron antineutrino-electron elastic scattering at low energy. The recoil electrons were recorded in a gas time projection chamber, immersed in a tank filled with liquid scintillator serving as veto detector, suppressing in particular Compton electrons. The measured electron recoil spectrum is presented. Upper limits on the neutrino magnetic moment were derived and are discussed.Comment: 9 pages, 7 figures Added reference: p.3, 1st col., TEXONO Added sentence: p.4, 1st col., electron attachement Modified sentence: p.5, 1st col., readout sequence Added sentence: p.5, 1st col., fast rise time cu

Monte Carlo evaluation of the external gamma, neutron and muon induced background sources in the CUORE experiment

CUORE is a 1 ton scale cryogenic experiment aiming at the measurement of the Majorana mass of the electron neutrino. The detector is an array of 988 TeO2 bolometers used for a calorimetric detection of the two electrons emitted in the BB0n of 130Te. The sensitivity of the experiment to the lowest Majorana mass is determined by the rate of background events that can mimic a BB0n. In this paper we investigate the contribution of external sources i.e. environmental gammas, neutrons and cosmic ray muons to the CUORE background and show that the shielding setup designed for CUORE guarantees a reduction of this external background down to a level <1.0E-02 c/keV/kg/y at the Q-value, as required by the physical goal of the experiment.Comment: 14 pages, 7 figure

A hydrogen beam to characterize the ASACUSA antihydrogen hyperfine spectrometer

The antihydrogen programme of the ASACUSA collaboration at the antiproton decelerator of CERN focuses on Rabi-type measurements of the ground-state hyperfine splitting of antihydrogen for a test of the combined Charge-Parity-Time symmetry. The spectroscopy apparatus consists of a microwave cavity to drive hyperfine transitions and a superconducting sextupole magnet for quantum state analysis via Stern-Gerlach separation. However, the small production rates of antihydrogen forestall comprehensive performance studies on the spectroscopy apparatus. For this purpose a hydrogen source and detector have been developed which in conjunction with ASACUSA's hyperfine spectroscopy equipment form a complete Rabi experiment. We report on the formation of a cooled, polarized, and time modulated beam of atomic hydrogen and its detection using a quadrupole mass spectrometer and a lock-in amplification scheme. In addition key features of ASACUSA's hyperfine spectroscopy apparatus are discussed.

Masses of light tetraquarks and scalar mesons in the relativistic quark model

Masses of the ground state light tetraquarks are dynamically calculated in the framework of the relativistic diquark-antidiquark picture. The internal structure of the diquark is taken into account by calculating the form factor of the diquark-gluon interaction in terms of the overlap integral of the diquark wave functions. It is found that scalar mesons with masses below 1 GeV: f_0(600) (\sigma), K^*_0(800) (\kappa), f_0(980) and a_0(980) agree well with the light tetraquark interpretation.Comment: 9 pages, Report-no adde

Mimicking diffuse supernova antineutrinos with the Sun as a source

Measuring the electron antineutrino component of the cosmic diffuse supernova neutrino background (DSNB) is the next ambitious goal for low-energy neutrino astronomy. The largest flux is expected in the lowest accessible energy bin. However, for E < 15 MeV a possible signal can be mimicked by a solar electron antineutrino flux that originates from the usual 8B neutrinos by spin-flavor oscillations. We show that such an interpretation is possible within the allowed range of neutrino electromagnetic transition moments and solar turbulent field strengths and distributions. Therefore, an unambiguous detection of the DSNB requires a significant number of events at E > 15 MeV.Comment: 4 pages, 1 figur

CPT violation and particle-antiparticle asymmetry in cosmology

General features of generation of the cosmological charge asymmetry in CPT non-invariant world are discussed. If the effects of CPT violation manifest themselves only in mass differences of particles and antiparticles, the baryon asymmetry of the universe hardly can be explained solely by breaking of CPT invariance. However, CPT non-invariant theories may lead to a new effect of distorting the usual equilibrium distributions. If this takes place, CPT violation may explain the baryon asymmetry of the universe.Comment: 7 pages, no figures. Submitted to a special issue of Yadernaya Fizika (Physics of Atomic Nuclei) dedicated to 80th birthday of L.B. Okun. Three references are adde

Electronic Fine Structure in the Electron-Hole Plasma in SrB6

Electron-hole mixing-induced fine structure in alkaline earth hexaborides leads to lower energy (temperature) scales, and thus stronger tendency toward an excitonic instability, than in their doped counterparts (viz. Ca(1-x)La(x)B(6), x=0.005), which are high Curie temperature, small moment ferromagnets. Comparison of Fermi surfaces and spectral distributions with de Haas - van Alphen (dHvA), optical, transport, and tunneling data indicates that SrB6 remains a fermionic semimetal down to (at least) 5 K, rather than forming an excitonic condensate. For the doped system the Curie temperature is higher than the degeneracy temperature.Comment: Four two-column pages, three postscript figures. Phys. Rev. Lett. (April 2000, in press

Pseudoscalar Glueball Mass: QCD vs. Lattice Gauge Theory Prediction

We study whether the pseudoscalar glueball mass in full QCD can differ from the prediction of quenched lattice calculations. Using properties of the correlator of the vacuum topological susceptibility we derive an expression for the upper bound on the QCD glueball mass. We show that the QCD pseudoscalar glueball is lighter than the pure Yang-Mills theory glueball studied in quenched lattice calculations. The mass difference between those two states is of order of $1/N_c$. The value calculated for the $0^{-+}$ QCD glueball mass can not be reconciled with any physical state observed so far in the corresponding channel. The glueball decay constant and its production rate in $J/\psi$ radiative decays are calculated. The production rate is large enough to be studied experimentally.Comment: 18 pages, LaTex fil

Near-Threshold Production of omega Mesons in the pp -> pp omega Reaction

The total cross section for omega production in the pp -> pp omega reaction has been measured at five c.m. excess energies from 3.8 to 30 MeV. The energy dependence is easily understood in terms of a strong proton-proton final state interaction combined with a smearing over the width of the state. The ratio of near-threshold phi and omega production is consistent with the predictions of a one-pion-exchange model and the degree of violation of the OZI rule is similar to that found in the pi-p -> n omega/phi reactions.Comment: Report in LaTeX2e. 12 pages with 2 eps figure

The cusp effect in eta' --> eta pi pi decays

Strong final-state interactions create a pronounced cusp in eta' --> eta pi0 pi0 decays. We adapt and generalize the non-relativistic effective field theory framework developed for the extraction of pi pi scattering lengths from K --> 3 pi decays to this case. The cusp effect is predicted to have an effect of more than 8% on the decay spectrum below the pi+ pi- threshold.Comment: 11 pages, 8 figures; comment added, typos corrected, version published in Eur. Phys. J.