Reaction mechanisms and multifragmentation processes have been studied for 64Zn+58Ni collisions at intermediate energies with the help of antisymmetrized molecular dynamics (AMD-V) model calculations. Experimental energy spectra, angular distributions, charge distributions, and isotope distributions, classified by their associated charged particle multiplicities, are compared with the results of the AMD-V calculations. In general the experimental results are reasonably well reproduced by the calculations. The multifragmentation observed experimentally at all incident energies is also reproduced by the AMD-V calculations. A detailed study of AMD-V events reveals that, in nucleon transport, the reaction shows some transparency, whereas in energy transport the reaction is much less transparent at all incident energies studied here. The transparency in the nucleon transport indicates that, even for central collisions, about 75% of the projectile nucleons appear in the forward direction. In energy transport about 80% of the initial kinetic energy of the projectile in the center- of-mass frame is dissipated. The detailed study of AMD-V events also elucidates the dynamics of the multifragmentation process. The study suggests that, at 35A MeV, the semitransparency and thermal expansion are the dominant mechanisms for the multifragmentation process, whereas at 49A MeV and higher incident energies a nuclear compression occurs at an early stage of the reaction and plays an important role in the multifragmentation process in addition to that of the thermal expansion and the semitransparency.
No description provided.
Average summed transverse momentum.
The production of single photons has been studied in the reaction e+e- -> gamma + invisible particles at centre-of-mass energies of 183 GeV and 189 GeV. A previously published analysis of events with multi-photon final states accompanied by missing energy has been updated with 189 GeV data. The data were collected with the DELPHI detector and correspond to integrated luminosities of about 51 pb^{-1} and 158 pb^{-1} at the two energies. The number of light neutrino families is measured to be 2.84 +/- 0.15(stat) +/- 0.14(syst). The absence of an excess of events beyond that expected from Standard Model processes is used to set limits on new physics as described by supersymmetric and composite models. A limit on the gravitational scale is also determined.
No description provided.
Combined result.
Tensor polarization observables (t20, t21 and t22) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c)^2. The experiment was performed at the Jefferson Laboratory in Hall C using the electron HMS Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q^2 the deuteron charge form factors G_C and G_Q. They are in good agreement with relativistic calculations and disagree with pQCD predictions.
No description provided.
No description provided.
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The Dalitz plot parameters G, H, and K are used in the standard parameterization of the matrix element squared (see PDG): M**2 = 1 + G*X + H*X**2 + K*Y**2,where X = (s3-s0)/m(PI)**2 and Y = (s1-s2)/m(PI)**2, s1 = (pK - pPI0)**2, s2 = (pK - pPI0)**2, s3 = (pK - pPI+)**2, s0 = (s1+s2+s3)/3.
We report on a measurement of the branching ratio of the rare decay ω→ηγ relative to the well known decay ω→π0γ. The ω’s are produced in pp¯→ηω and pp¯→π0ω. Eigenstate mixing and interference effects of the ω and ρ0 are taken into account, as well as coherent interference with the background. We find evidence for the non-resonant annihilation channel B(pp¯→ηηγ)=(3.5±1.3)×10−5 and limit the value of B(ω→ηγ) to the range of (0.7to5.5)×10−4 depending on the degree of coherence with the background.
No description provided.
A double scattering experiment, performed at the Paul-Scherrer-Institut (PSI), has measured a large variety of spin observables for free np elastic scattering from 260 to 535 MeV in the c.m. angle ran
Relative uncertainties on the carbon polarimeter analysing power (AC).
Relative uncertainty in the beam polarisation (PB).
Measurements of DNN with statistical errors only.
The spin correlation parameters$A_{oonn}, A_{ooss}, A_{oosk}, A_{ookk}$and the analyzing power$A_{oono}$have been measured i
Values of the coefficients for the linear combinations of the spin correlation parameters Cpq measurements for the four different beam and target polarisation orientations. For the (z,z) and (y,y) configurations the coefficients are identical for all incident kinetic energies.
Measurement of the analysing power. Statistical errors only are shown. For the systematic errors see the systematics section above. Note that there are two overlapping angular settings.
Measurements of the spin correlation parameter CNN. Statistical errors onlyare shown. For the systematics see the systematic section above. Note the two overlapping angular settings.
A sample of 2.2 million hadronic Z decays, selected from the data recorded by the Delphi detector at LEP during 1994-1995 was used for an improved measurement of inclusive distributions of pi+, K+ and p and their antiparticles in gluon and quark jets. The production spectra of the individual identified particles were found to be softer in gluon jets compared to quark jets, with a higher multiplicity in gluon jets as observed for inclusive charged particles. A significant proton enhancement in gluon jets is observed indicating that baryon production proceeds directly from colour objects. The maxima, xi^*, of the xi-distributions for kaons in gluon and quark jets are observed to be different.
Jet flavor tagging is used. (C=DUSCB), (C=DUSC), (C=UDS) mean quark-jet flavors. CONST(C=GLUON/JET) is the ratio gluon/jet for all charged particles. 'Y' events, mirror symmetric events, the angle between the most energetic jet and other two jets is 150 +- 15 deg.
Jet flavor tagging is used. (C=DUSCB), (C=DUSC), (C=UDS) mean quark-jet flavors. CONST(C=GLUON/JET) is the ratio gluon/jet for all charged particles. 'Y' events, mirror symmetric events, the angle between the most energetic jet and other two jets is 150 +- 15 deg.
Jet flavor tagging is used. (C=DUSCB), (C=DUSC), (C=UDS) mean quark-jet flavors. CONST(C=GLUON/JET) is the ratio gluon/jet for all charged particles. 'Y' events, mirror symmetric events, the angle between the most energetic jet and other two jets is 150 +- 15 deg.
A first measurement of the cross section of the process e+e- -> Z gamma gamma is reported using a total integrated luminosity of 231 pb^-1 collected with the L3 detector at centre-of-mass energies of 182.7 GeV and 188.7 GeV. By selecting hadronic events with two isolated photons the e+e- -> Z gamma gamma cross section is measured to be 0.49 +0.20 -0.17 +/- 0.04 pb at 182.7 GeV and 0.47 +/- 0.10 +/- 0.04 pb at 188.7 GeV. The measurements are consistent with Standard Model expectations. Limits on Quartic Gauge Boson Couplings a_0/Lambda^2 and a_c/Lambda^2 of -0.009 GeV^-2 < a_0/Lambda^2 < 0.008 GeV^-2 and -0.007 GeV^-2 < a_c/Lambda^2 < 0.013 GeV^-2 are derived at 95% confidence level.
The measured cross section for the hadronic decay of the Z0.
The cross sections scaled for the hadronic Z0 branching ratio.
Bhabha scattering data recorded at \sqrt{s}=189 GeV by the L3 detector at LEP are used to measure the running of the effective fine-structure constant for spacelike momentum transfers. The results are alpha^-1(-2.1 GeV^2) - alpha^-1(-6.25 GeV^2) = 0.78 +/- 0.26 alpha^-1(-12.25 GeV^2) - alpha^-1(-3434 GeV^2) = 3.80 +/- 1.29, in agreement with theoretical predictions.
No description provided.
Results extracted from the small angle Bhabha scattering sample at Z peak. Results contained total experimental uncertainty.
Results extracted from the large angle Bhabha scattering sample at sqrt(s) = 189 GeV. Results contained total experimental and theoretical uncertainty.
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