A search is described for the neutral Higgs bosons h0 and A0 predicted by models with two scalar field doublets and, in particular, the Minimal Supersymmetric Standard Model (MSSM). The search in the ...Z0h0 and h0A0 production channels is based on data corresponding to an integrated luminosity of 25 pb−1 from e+e− collisions at centre-of-mass energies between 130 and 172 GeV collected with the OPAL detector at LEP. The observation of a number of candidates consistent with Standard Model background expectations is used in combination with earlier results from data collected at the Z0 resonance to set limits on mh and ma in general models with two scalar field doublets and in the MSSM. For example, in the MSSM, for tan β > 1, minimal and maximal scalar top quark mixing and soft SUSY-breaking masses of 1 TeV, the 95% confidence level limits mh > 59.0 GeV and ma > 59.5 GeV are obtained. For the first time, the MSSM parameter space is explored in a detailed scan.
The timing calibration is a delicate operation to perform for assuring the full functionality of a large underwater neutrino telescope. In this paper we illustrate the main features of our system for ...timing calibration tailored to the needs of the prototype of the NEMO (NEutrino Mediterranean Observatory) apparatus. We point out that the approach proposed can be easily adapted to work in any underwater neutrino telescope.
Phys.Atom.Nucl. 67 (2004) 1139-1146; Yad.Fiz. 67 (2004) 1165-1171 The final results of the MACRO experiment on atmospheric neutrino
oscillations are presented and discussed. The data concern ...different event
topologies with average neutrino energies of ~3 and ~50 GeV. Multiple Coulomb
Scattering of the high energy muons in absorbers was used to estimate the
neutrino energy of each event. The angular distributions, the L/E_nu
distribution, the particle ratios and the absolute fluxes all favour nu_mu -->
nu_tau oscillations with maximal mixing and Delta m^2 =0.0023 eV^2. A
discussion is made on the Monte Carlos used for the atmospheric neutrino flux.
Some results on neutrino astrophysics are also briefly discussed.
Searches for pair-produced charginos and neutralinos with R-parity violating decays have been performed using a data sample corresponding to an integrated luminosity of 56 pb\(^{-1}\) collected with ...the OPAL detector at LEP at a centre-of-mass energy of \(\sqrt{s}=\) 183 GeV. An important consequence of R-parity violation is that the lightest supersymmetric particle becomes unstable. The searches have been performed under the assumptions that the lightest supersymmetric particle promptly decays and that only one R-parity violating coupling is dominant for each of the decay modes considered. Such processes would yield multiple leptons, jets plus leptons, or multiple jets with or without significant missing energy in the final state. No excess of such events above Standard Model backgrounds has been observed. Limits are presented on the production cross-sections of gauginos in R-parity violating scenarios. Limits are also presented in the framework of the Minimal Supersymmetric Standard Model.
We shall discuss some aspects of science and technology, their increasing role in the society, the fast advances in modern science, the apparent decrease of interest of the young generation in basic ...sciences, the importance of proper science popularization for better public education and awareness in scientific fields.
Eur.Phys.J.C33:s826-s828,2004 The final results of the MACRO experiment on atmospheric neutrino
oscillations are presented. The data concern different event topologies with
average neutrino energies ...of ~ 3 and ~ 50 GeV. Multiple Coulomb Scattering of
the high energy muons was used to estimate the neutrino energy event by event.
The angular distributions, the L/E_nu distribution, the particle ratios and the
absolute fluxes all favour nu_mu --> nu_tau oscillations with maximal mixing
and Delta m^2 ~ 0.0023 eV^2. Emphasis is given to measured ratios which are not
affected by Monte Carlo (MC) absolute normalization; a discussion is made on MC
uncertainties.
Stochastic resonance in bulk semiconductor lasers Pedaci, Francesco; Giudici, Massimo; Tredicce, Jorge R ...
Physical review. E, Statistical, nonlinear, and soft matter physics,
03/2005, Letnik:
71, Številka:
3 Pt 2A
Journal Article
The stochastic time scale of the mode hopping in a bulk semiconductor laser can be varied maintaining the symmetry of the residence times by a proper tuning of the laser substrate temperature and ...pumping current. While the addition of external noise to the pumping current affects the symmetry of the mode-hopping process, a sinusoidal modulation does not, providing that the modulation amplitude is below a critical value. In this case, we observe stochastic resonance in the modal intensities of the laser. We show the occurrence of the phenomenon in the spectral domain, and we characterize it by a statistical analysis based on the residence times probability distributions. The evidence of bona fide resonance is also provided, varying the modulation frequency and analyzing a proper statistical indicator. Changing the temperature of the laser substrate we show that resonance occurs at different modulation periods always equal to the double of the average residence time measured without modulation.
We used Nuclear Track Detectors (NTD) CR39 and Makrofol for many purposes: (i) Exposures at the SPS and at lower energy accelerator heavy ion beams for calibration purposes and for fragmentation ...studies. (ii) Searches for GUT and Intermediate Mass Magnetic Monopoles (IMM), nuclearites, Q-balls and strangelets in the cosmic radiation. The MACRO experiment in the Gran Sasso underground lab, with ̃1,000 m2 of CR39 detectors (plus scintillators and streamer tubes), established an upper limit for superheavy GUT poles at the level of 1.4 × 10−16 cm−2 s−1 sr−1for 4 ×10−5<β<1. The SLIM experiment at the high altitude Chacaltaya lab (5,230 m a.s.l.), using 427 m2 of CR39 detectors exposed for 4.22 years, gave an upper limit for IMMs of ̃1.3 × 10−15 cm−2 s−1 sr−1. The experiments yielded interesting upper limits also on the fluxes of the other mentioned exotic particles. (iii) Environmental studies, radiation monitoring, neutron dosimetry.
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