Search for DCC in 158A GeV Pb+Pb Collisions

A detailed analysis of the phase space distributions of charged particles and photons have been carried out using two independent methods. The results indicate the presence of nonstatistical fluctuations in localized regions of phase space.Comment: Talk at the PANIC99 Conference, June 9-16, 199

Present Status and Future of DCC Analysis

Disoriented Chiral Condensates (DCC) have been predicted to form in high energy heavy ion collisions where the approximate chiral symmetry of QCD has been restored. This leads to large imbalances in the production of charged to neutral pions. Sophisticated analysis methods are being developed to disentangle DCC events out of the large background of events with conventionally produced particles. We present a short review of current analysis methods and future prospects.Comment: 12 pages, 5 figures. Invited talk presented at the 13th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 97), Tsukuba, Japan, 1-5 Dec 199

Central Pb+Pb Collisions at 158 A GeV/c Studied by Pion-Pion Interferometry

Two-particle correlations have been measured for identified negative pions from central 158 AGeV Pb+Pb collisions and fitted radii of about 7 fm in all dimensions have been obtained. A multi-dimensional study of the radii as a function of kT is presented, including a full correction for the resolution effects of the apparatus. The cross term Rout-long of the standard fit in the Longitudinally CoMoving System (LCMS) and the vl parameter of the generalised Yano-Koonin fit are compatible with 0, suggesting that the source undergoes a boost invariant expansion. The shapes of the correlation functions in Qinv and Qspace have been analyzed in detail. They are not Gaussian but better represented by exponentials. As a consequence, fitting Gaussians to these correlation functions may produce different radii depending on the acceptance of the experimental setup used for the measurement.Comment: 13 pages including 10 figure

Search for Disoriented Chiral Condensates in 158 AGeV Pb+Pb Collisions

The restoration of chiral symmetry and its subsequent breaking through a phase transition has been predicted to create regions of Disoriented Chiral Condensates (DCC). This phenomenon has been predicted to cause anomalous fluctuations in the relative production of charged and neutral pions in high-energy hadronic and nuclear collisions. The WA98 experiment has been used to measure charged and photon multiplicities in the central region of 158 AGeV Pb+Pb collisions at the CERN SPS. In a sample of 212646 events, no clear DCC signal can be distinguished. Using a simple DCC model, we have set a 90% C.L. upper limit on the maximum DCC production allowed by the data.Comment: 20 Pages, LaTeX, uses elsart.cls, 8 eps figures included, submitted to Physics Letters

Directed Flow in 158 A GeV 208Pb^{208}Pb + 208Pb^{208}Pb Collisions

The directed flow of protons and positive pions have been studied in 158 A GeV Pb + Pb collisions. A directed flow analysis of the rapidity dependence of the average transverse momentum projected onto the reaction plane is presented for semi-central collisions with impact parameters of approximately 8 fm, where the flow effect is largest. The magnitude of the directed flow is found to be significantly smaller than observed at AGS energies and than RQMD model predictions.The directed flow of protons and positive pions have been studied in 158 A GeV Pb + Pb collisions. A directed flow analysis of the rapidity dependence of the average transverse momentum projected onto the reaction plane is presented for semi-central collisions with impact parameters of approximately 8 fm, where the flow effect is largest. The magnitude of the directed flow is found to be significantly smaller than observed at AGS energies and than RQMD model predictions

Apiculture: The Sweet Trail to Prosperity

44-48Honeybees play an important role in plant pollination. The honey accruing from them also provides a dense source of energy

The Incredible Journey of Nitrates and Ammonia

36-39The recent devastating explosion in Beirut was caused by 2750 tons of ammonium nitrate, a chemical compound commonly used as an agricultural fertiliser, but also known as the grandfather of explosives

Yield of K x rays emitted from U fragments

The yield of K x rays from different fragment masses have been determined in the thermal-neutron-induced fission of U235. The energies of the pairs of fragments were measured with two semiconductor detectors placed on either side of a thin U235 foil. The K x rays from the light and the heavy groups of fragments were separated by measuring the x-ray energies with a 1-mm NaI(Tl) crystal. The fragment mass distributions in coincidence with the light group of K x rays and with the heavy group of K x rays, and the unbiased mass distributions, were simultaneously recorded in different quarters of a 1024-channel analyzer memory. From these distributions, after suitable corrections for the background, x-rays detection efficiencies, and finite-energy-resolution effects, the number of x rays as a function of fragment mass has been determined. The x-ray yield per fission is found to be 0.08±0.01 for the light fragment group, and 0.30±0.02 for the heavy fragment group. The gross features of the yield as a function of mass are similar to those observed earlier for emission from Cf252 fragments. However, unlike the case of Cf252, for masses greater than 144 the striking increase in the yield is not observed. The present results are consistent with the interpretation that the x-ray yield depends both on the characteristics of the low-lying states and the initial spin of the fragments