W. Toothacker

EVIDENCE FOR PARTON KT EFFECTS IN HIGH-PT PARTICLE PRODUCTION

Inclusive pizero and direct-photon cross sections in the kinematic range 3.5 < pT < 12 GeV/c with central rapidities are presented for 530 and 800 GeV/c proton beams and a 515 GeV/c pi- beam incident on beryllium targets. Current Next-to-Leading-Order perturbative QCD calculations fail to adequately describe the data for conventional choices of scales. Kinematic distributions from these hard scattering events provide evidence that the interacting partons carry significant initial-state parton transverse momentum (kT). Incorporating these kT effects phenomenologically greatly improves the agreement between calculations and the measured cross sections.

Measurement of the stopping power of nuclei for 100 GeV/c protons and antiprotons

Abstract We have studied the reactions p+A→ (p, n)+X and p +A→ p +X at beam momenta of 100 GeV/c for Mg, Ag and Au targets. The rapidity loss of the leading final state protons, antiprotons, and neutrons has been obtained as a measurement of the nuclear stopping power and correlated with the number of slow protons and the multiplicity and momentum of the associated charged particles.

Measurements of light nuclei production in 11.5a 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.

The limiting curve of leading particles from hadron-nucleus collisions at infinite A☆

We argue that as the atomic number of the target nucleus A → ∞, the multiplicity of leading particles in hadron-nucleus collisions tends to a finite limit. The limiting multiplicities for various particle production are computed for both proton and pion projectiles. Signatures at finite A are discussed. Data from 100 GeV/c central hadron-nucleus collisions are analyzed and found to be in qualitative agreement with this picture.

Measurement of direct-photon production at the Fermilab Tevatron fixed target energies

Measurements of the production of high transverse momentum direct photons by a 515 GeV/c {pi}{sup -} beam and 530 and 800 GeV/c proton beams in interactions with beryllium and hydrogen targets are presented. The data span the kinematic ranges of 3.5<p{sub T}<12 GeV/c in transverse momentum and 1.5 units in rapidity. The inclusive direct-photon cross sections are compared with next-to-leading-order perturbative QCD calculations and expectations based on a phenomenological parton-k{sub T} model.

Antideuteron yield at the AGS and coalescence implications

We present Experiment 864s 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.

Direct photon production at high p-transverse in pi- Be and p Be collisions at 500-GeV/c

We report new measurements of inclusive direct photon production at high transverse momenta (pT) for π - and p interactions on Be at 500 Gev/r. The yields as a function of pT and rapidity (y) are in good agreement with expectations from next-to-leading-log QCD calculations employing recently extracted quark and gluon structure functions

Design and operation of large straw-tube drift chamber planes

Abstract We describe the design, construction and operation of a straw-tube drift chamber consisting of four X and four Y planes of 16 mm diameter straw

Production of 0 andmesons at large transverse momenta in pp and pBe interactions at 530 and 800 GeV/c

We present results on the production of high transverse momentum pizero and eta mesons in pp and pBe interactions at 530 and 800 GeV/c. The data span the kinematic ranges: 1 < p_T < 10 GeV/c in transverse momentum and 1.5 units in rapidity. The inclusive pizero cross sections are compared with next-to-leading order QCD calculations and to expectations based on a phenomenological parton-k_T model.

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.