S. K. Mark

Proton and pion production relative to the reaction plane in Au + Au collisions at 11A GeV/c

Results are presented of an analysis of proton and charged pion azimuthal distributions measured with respect to the reaction plane in Au + Au collisions at a beam momentum of about 11A GeV/c. The azimuthal anisotropy is studied as a function of particle rapidity and transverse momentum for different centralities of the collisions. The triple differential (in rapidity, transverse momentum, and azimuthal angle) distributions are reconstructed. A comparison of the results with a previous analysis of charged-particle and transverse energy flow as well as with model predictions are presented. {copyright} {ital 1997} {ital The American Physical Society}

Proton and pion production in Au+Au collisions at 10.8A GeV/c

We present proton and pion tranverse momentum spectra and rapidity distributions for Au+Au collisions at 10.8A GeV/c. The proton spectra exhibit collective transverse flow effects. Evidence of the influence of the Coulomb interaction from the fireball is found in the pion transverse momentum spectra. The data are compared with the predictions of the RQMD event generator.

Measurement of pion enhancement at low transverse momentum and of the Δ resonance abundance in Si-nucleus collisions at AGS energy

Abstract We present measurements of pion transverse momentum ( p t ) spectra in central Si-nucleus collisions in the rapidity range 2.0 y p t down to and including p t = 0. The data exhibit an enhanced pion yield at low p t compared to what is expected for a purely thermal spectral shape. This enhancement is used to determine the Δ resonance abundance at freeze-out. The results are consistent with a direct measurement of the Δ resonance yield by reconstruction of proton-pion pairs and imply a temperature of the system at freeze-out close to 140 MeV.We present measurements of the pion transverse momentum (p_t) spectra in central Si-nucleus collisions in the rapidity range 2.0<y<5.0 for p_t down to and including p_t=0. The data exhibit an enhanced pion yield at low p_t compared to what is expected for a purely thermal spectral shape. This enhancement is used to determine the Delta-resonance abundance at freeze-out. The results are consistent with a direct measurement of the Delta-resonance yield by reconstruction of proton-pion pairs and imply a temperature of the system at freeze-out close to 140 MeV.

Two pion correlations in Au + Au collisions at 10.8-GeV/c per nucleon

Two-particle correlation functions for positive and negative pions have been measured in Au+Au collisions at 10.8GeV/{ital c} per nucleon. The data were analyzed using one- and three-dimensional correlation functions. From the results of the three-dimensional fit the phase space density of pions was calculated. It is consistent with local thermal equilibrium. {copyright} {ital 1997} {ital The American Physical Society}

Search for strange quark matter in high-energy heavy-ion collisions

Abstract We have initiated a search for strange quark matter in the products of 14.6 GeV/ c per nucleon 28 Si collisions with nuclei, utilizing the apparatus of E-814 at Brookhaven National Laboratorys AGS. We report the first results of this search, which is sensitive to particles with charge-to-mass ratios between 0.1 and 0.3 (GeV/ c 2 ) −1 that are produced within approximately ±0.5 units of the center of mass rapidity.

The decay of 69As

Abstract The β + decay of 69 As to levels in 69 Ge has been investigated with the use of Ge(Li), Si(Li) and NaI(Tl) detectors. Six gamma rays at energies of 86.8, 145.8, 232.7, 287.1, 374.1 and 398.1 keV were observed and internal conversion coefficients for the first three gamma rays have been measured. On the basis of coincidence measurements, a decay scheme with spin and parity assignments is proposed. The half-life of the 86.8 and 232.7 keV states in 69 Ge have been measured to be 5.1 ± 0.3 μ s and 176 ± 12 ps, respectively.

States of 76Br observed in the decay of 76Kr

Abstract The decay of 76 Kr is studied by means of β- and γ-ray spectroscopy. Of the 54 γ-rays observed, 51 of them are placed in a decay scheme which includes excited states at 45.5, 150.5, 252.0, 260.0, 280.0, 315.7, 317.1, 355.3, 446.3, 451.9, 616.0, 815.3, 868.2, 898.5, 936.5 and 1047.8 keV. With the help of internal conversion electron measurements and the deduced log ft values, spin-parity assignments are made for the observed states in 76 Br. The ground state of 76 Br is established as a 1 − state.

Evidence for expansion of a hot fireball from two-pion correlations for Si + Pb collisions at AGS energy

Abstract The two-pion correlation function has been measured for charged pions produced in central 14.6 A GeV/ c Si + Pb collisions at the AGS. Data for like-sign pions show a clear quantum interference effect as expected for identical bosons. The experimental correlation function agrees well with that obtained for events generated by a cascade code (RQMD). The present data are consistent with a time-averaged rms freeze-out radius of 8.3 fm and a mean duration of pion emission of 9 fm/ c . The system has expanded considerably before freeze-out.

Study of the ((π1g92)3 s = 1)(v2d52) multiplet in 94Tc AND 98Tc by use of the 94, 98Mo(3He, t)94, 98Tc reactions

Abstract The structures of 94 43 Tc 51 and 98 43 Tc 55 have been investigated by using the 94, 98 Mc( 3 He, t) 94, 98 Tc reactions. Tentative spin and parity assignments have been made on the basis of the known systematics of the ( 3 He, t) reaction. The low-lying positive parity states of 94 Tc are shown to belong to the ((π1 g 9 2 ) 3 s = 1)(v2 d 5 2 ) multiplet. Excellent agreement between theory and experiment has been obtained. On the other hand, the ((π1 g 9 2 ) 3 s = 1)(v2 d 5 2 ) −1 multiplet in 98 Tc has been found to be fragmented due to configuration mixing. This configuration mixing appears to give rise to some intruder states in the low excitation spectrum of 98 Tc. However, the high spin states of 5 + , 6 + and 7 + at low excitation show remarkably similar features to those of the (π1 g 9 2 ) (v2 d 5 2 ) −1 multiplets in 96 Nb. The negative parity states of 2 − and 3 − which presumably have dominant (π p 1 2 ) −1 (v d 5 2 ) ±1 configurations were also observed. The triton yields for these negative parity states were rather weak, and consequently the angular distributions had anomalous shapes.

Proton stripping reactions populating levels in 95,97,101Tc

The structure of the low-lying levels of 95,97,101Tc was investigated with the proton stripping (3He,d) reaction. The experimental angular distributions were compared with distorted-wave Born-approximation calculations, and l-values and spectroscopic factors were extracted. The proton configurations of the target ground states were deduced. The systematics of transition strength distributions are discussed.