Antideuteron yield at the AGS and coalescence implications

We present Experiment 864's measurement of invariant antideuteron yields in 11.5A GeV/c Au + Pt collisions. The analysis includes 250 million triggers representing 14 billion 10% central interactions sampled for events with high mass candidates. We find (1/2 pi pt) d^(2)N/dydpt = 3.5 +/- 1.5 (stat.) +0.9,-0.5 (sys.) x 10^(-8) GeV^(-2)c^(2) for 1.8=0.35 GeV/c (y(cm)=1.6) and 3.7 +/- 2.7 (stat.) +1.4,-1.5 (sys.) x 10^(-8) GeV^(-2)c^(2) for 1.4=0.26 GeV/c, and a coalescence parameter B2-bar of 4.1 +/- 2.9 (stat.) +2.3,-2.4 (sys.) x 10^(-3) GeV^(2)c^(-3). Implications for the coalescence model and antimatter annihilation are discussed.Comment: 8 pages, 4 figures, Latex, submitted to Phys. Rev. Let

Mass dependence of light nucleus production in ultrarelativistic heavy ion collisions

Light nuclei can be produced in the central reaction zone via coalescence in relativistic heavy ion collisions. E864 at BNL has measured the production of ten light nuclei with nuclear number of A=1 to A=7 at rapidity $y\simeq1.9$ and $p_{T}/A\leq300MeV/c$. Data were taken with a Au beam of momentum of 11.5 A $GeV/c$ on a Pb or Pt target with different experimental settings. The invariant yields show a striking exponential dependence on nuclear number with a penalty factor of about 50 per additional nucleon. Detailed analysis reveals that the production may depend on the spin factor of the nucleus and the nuclear binding energy as well.Comment: (6 pages, 3 figures), some changes on text, references and figures' lettering. To be published in PRL (13Dec1999

Measurements of Light Nuclei Production in 11.5 A GeV/c Au+Pb Heavy-Ion Collisions

We report on measurements by the E864 experiment at the BNL-AGS of the yields of light nuclei in collisions of Au(197) with beam momentum of 11.5 A GeV/c on targets of Pb(208) and Pt(197). The yields are reported for nuclei with baryon number A=1 up to A=7, and typically cover a rapidity range from y(cm) to y(cm)+1 and a transverse momentum range of approximately 0.1 < p(T)/A < 0.5 GeV/c. We calculate coalescence scale factors B(A) from which we extract model dependent source dimensions and collective flow velocities. We also examine the dependences of the yields on baryon number, spin, and isospin of the produced nuclei.Comment: 21 figures-to be published in Phys. Rev.

Search for Exotic Strange Quark Matter in High Energy Nuclear Reactions

We report on a search for metastable positively and negatively charged states of strange quark matter in Au+Pb reactions at 11.6 A GeV/c in experiment E864. We have sampled approximately six billion 10% most central Au+Pb interactions and have observed no strangelet states (baryon number A < 100 droplets of strange quark matter). We thus set upper limits on the production of these exotic states at the level of 1-6 x 10^{-8} per central collision. These limits are the best and most model independent for this colliding system. We discuss the implications of our results on strangelet production mechanisms, and also on the stability question of strange quark matter.Comment: 21 pages, 9 figures, to be published in Nuclear Physics A (Carl Dover memorial edition

Production of Λ3H^{3}_{\Lambda}H and Λ4H^{4}_{\Lambda}H in Central 11.5 GeV/c Au + Pt Heavy Ion Collisions

We present measurements from BNL AGS Experiment E864 of the $^{3}_{\Lambda}H$ invariant multiplicity and of the 90% Confidence Level upper limit on the $^{4}_{\Lambda}H$ yield in central 11.5 A GeV/c Au + Pt collisions. The measurements span a rapidity range from center of mass, $y_{cm}$, to $y_{cm}$+1 and a transverse momentum range of $0.< p_{T}\le 1.5$ GeV/c. We compare these results with E864 measurements of stable light nuclei and particle unstable nuclei yields of the same baryon number. The implications of these results for the coalescence of strange clusters are discussed.Comment: 16 pages, 4 figures, 2 table

Search for Strange Quark Matter Produced in Relativistic Heavy Ion Collisions

We present the final results from Experiment 864 of a search for charged and neutral strange quark matter produced in interactions of 11.5 GeV/c per nucleon Au beams with Pt or Pb targets. Searches were made for strange quark matter with A>4. Approximately 30 billion 10% most central collisions were sampled and no strangelet states with A<100 were observed. We find 90% confidence level upper limits of approximately 10^{-8} per central collision for both charged and neutral strangelets. These limits are for strangelets with proper lifetimes greater than 50 ns. Also limits for H^{0}-d and pineut production are given. The above limits are compared with the predictions of various models. The yields of light nuclei from coalescence are measured and a penalty factor for the addition of one nucleon to the coalescing nucleus is determined. This is useful in gauging the significance of our upper limits and also in planning future searches for strange quark matter.Comment: 35 pages, 18 figures, submitted to Phys. Rev.

Study of intermittency in h-h collisions at {Mathematical expression}=16.7 GeV

Charged-particle multiplicity distributions from hadron-hadron collisions at {Mathematical expression}=16.7 GeV are analyzed in rapidity, pseudorapidity and azimuthal angle intervals. The data-fully reconstructed events-were taken in the rapid-cycling Bubble Chamber of the International Hybrid Spectrometer Consortium exposed to a hadron beam (147 GeV/c momentum) of the Tevatron at Fermilab. The factorial moments of the multiplicity distributions increase with decreasing rapidity interval. The energy dependence of the slopes in h-h collisions is discussed. Suitable phase-space cuts show that most of the intermittency effect stems from low-transverse-momentum particles. In the two-dimensional analysis (rapidity azimuthal angle) we find a weak enhancement of the slope values, more in agreement with the observations by the NA22 experiment, rather than the observations in e+e- by the HRS collaboration

Measurement of leading Lambda\u27s and Delta(++)\u27s in p+Pb collisions at 19 GeV/c

We present the first comprehensive measurement of leading Lambda\u27s and Delta(++)\u27s in p+Pb collisions at 19 GeV/c using the E941/E864 spectrometer at the AGS. In comparison with the measurement of leading protons and neutrons using the same spectrometer, it is found that the cross section for baryon flavor change is large and strongly depends on rapidity, which is very different from the expectation of simple diquark-quark fragmentation of the incident proton. A suppression of leading Lambda production in the forward rapidity region compared with nonstrange leading baryons is also observed. The relative probability of the projectile proton fragmentation into a Delta(++) versus into a neutron is found to be about 35% in the region of 2.7less than or equal toyless than or equal to3.1. We will discuss the impact of these results on the dynamics of baryon fragmentation and baryon number transport in nuclear collisions

Study of intermittency in h h collisions at s**(1/2) = 16.7 GeV.

Charged-particle multiplicity distributions from hadron-hadron collisions at sqrt{s} =16.7 GeV are analyzed in rapidity, pseudorapidity and azimuthal angle intervals. The data—fully reconstructed events—were taken in the rapid-cycling Bubble Chamber of the International Hybrid Spectrometer Consortium exposed to a hadron beam (147 GeV/c momentum) of the Tevatron at Fermilab. The factorial moments of the multiplicity distributions increase with decreasing rapidity interval. The energy dependence of the slopes in h-h collisions is discussed. Suitable phase-space cuts show that most of the intermittency effect stems from low-transverse-momentum particles. In the two-dimensional analysis (rapidity azimuthal angle) we find a weak enhancement of the slope values, more in agreement with the observations by the NA22 experiment, rather than the observations in e+e− by the HRS collaboration