Multiplicity distribution and spectra of negatively charged hadrons in Au+Au collisions at square root of (sNN) = 130 GeV

The minimum-bias multiplicity distribution and the transverse momentum and pseudorapidity distributions for central collisions have been measured for negative hadrons ( h(-)) in Au+Au interactions at square root of ([s(NN)]) = 130 GeV. The multiplicity density at midrapidity for the 5% most central interactions is dN(h(-))/d(eta)/(eta = 0) = 280+/-1(stat)+/-20(syst), an increase per participant of 38% relative to pp collisions at the same energy. The mean transverse momentum is 0.508+/-0.012 GeV/c and is larger than in central Pb+Pb collisions at lower energies. The scaling of the h(-) yield per participant is a strong function of p( perpendicular). The pseudorapidity distribution is almost constant within /eta/<1.     

Low-Loss NbTiN Films for THz SIS Mixer Tuning Circuits

Recent results at 1 THz using normal-metal tuning circuits have shown that SIS mixers can work well up to twice the gap frequency of the junction material (niobium). However, the performance at 1 THz is limited by the substantial loss in the normal metal films. For better performance superconducting films with a higher gap frequency than niobium and with low RF loss are needed. Niobium nitride has long been considered a good candidate material, but typical NbN films suffer from high RF loss. To circumvent this problem we are currently investigating the RF loss in NbTiN films, a 15K Tc compound superconductor, by incorporating them into quasi-optical slot antenna SIS devices.     

High<Emphasis Type="Italic">p</Emphasis><Subscript>T</Subscript> physics at STAR

We discuss the capabilities of STAR in exploring the physics at highp _T in ultrarelativistic heavy-ion colisions from RHIC at √^s _NN = 130 GeV Preliminary results show that the spectra of negatively charged particles get suppressed at largerp _T in comparison top-p data. A strong azimuthal anisotropy observed at large transverse momentum region. A preliminary ratio -p/p has been measured by STAR-RICH detector. Some ongoing studies and future plans are discussed.     

The effect of electron spin on plasma frequency of a narrow-gap semiconductor in quantizing magnetic fields

The effect of the electron spin on the plasma frequency of a narrow-gap semiconductor is studied including nonparabolicity of the band structure. The effect of spin is found to enhance the plasma frequency, particularly for high magnetic fields.     

Lamellar liquid crystals of zwitterionic surfactants with hydrocarbon and polyisobutylene chains

Surfactants from either polyisobutylene or alkylsuccinic anhydrides derivatized with diethanolamine in a 1:1 molar ratio with hydrocarbon and polyisobutylene chains of similar length formed lamellar liquid crystals in situ and also with added water. The repeat distance between layers was determined using low angle X-ray diffraction (LAXD), and the water penetration into the hydrocarbon space in the lamellar structure was calculated.

The results revealed a significantly increased repeat distance for the polyisobutylene chain surfactants compared to the alkyl analogues. The water penetration was significantly greater for a surfactant with a decyl chain compared to the one with a dodecyl chain and was intermediate for the polyisobutylene based surfactant.     

Thermal expansion and compressibility of β-As4S3

Temperature and pressure variation of the lattice constants and unit cell volume have been studied with the help of low temperature Guinier-Simon film technique and energy dispersive high pressure X-ray diffraction. Volume thermal expansion coefficient at room temperature and its derivative have been obtained by fitting the experimental data with volume-temperature equation obtained from purely thermodynamic considerations. Similarly bulk modulus at ambient pressure and its derivative with respect to pressure have been obtained by fitting volume-pressure data with the Murnaghan equation of state. The anisotropy of thermal expansion coefficient and the compressibility have been discussed.     

Three-pion interferometry results from central Pb+Pb collisions at 158A GeV/c

Three-particle correlations have been measured for identified pi(-) from central 158A GeV Pb+Pb collisions by the WA98 experiment at CERN. A substantial contribution of the genuine three-body correlation has been found as expected for a mainly chaotic and symmetric source.