R. Klingenberg

Antihelium-3 production in lead-lead collisions at 158 A GeV/c

The NA52 experiment measured particle and antiparticle yields at 0° production angle over a wide range in rapidity in lead-leadxa0(Pb-Pb) collisions at 158xa0Axa0GeV/c with a minimum bias trigger. Besides (106) antiprotons () and (103) antideuterons () a total of five antihelium-3 () were found. The resulting invariant differential production cross sections at pt0xa0GeV/c turn out to be Exa0(d3σ)/(dp3) = (2.5xa0±xa01.8)xa0×xa010-7xa0bc3xa0GeV-2 at a rapidity of y = 3.4 in the laboratory system and (5.9xa0±xa03.4)xa0×xa010-8xa0bc3xa0GeV-2 at y = 4.0. The results are discussed in the framework of a simple coalescence model.

Antinuclei production in Pb + Pb collisions at 158 A GeV/c

Abstract We investigate antinuclei production in Pb + Pb interactions at 158 GeV/ c per nucleon at zero degree production angle. We quote invariant differential production cross sections for antiprotons and antideuterons. The corresponding antideuteron to antiproton ratio at midrapidity is 4.2 · 10 −4 . One antihelium-3 nucleus was observed. The results are discussed in the framework of a simple coalescence model.

Baryon and antibaryon production in lead-lead collisions at 158 A GeV/c

Abstract We report on baryon and antibaryon as well as K+ and K− production cross sections measured in lead-lead collisions at 158 GeV /c per nucleon. The presented data were taken at zero degree production angle with a minimum bias trigger. The measurements covered a wide range of rapidity 1.4

Strangelet search and particle production studies in Pb + Pb collisions

Abstract We searched for long-lived strange quark matter particles, so-called strangelets , and studied particle and antiparticle production in Pb + Pb collisions at 158 GeV/ c per nucleon at zero degree production angle. We give upper limits for the production of strangelets covering a mass to charge ratio up to 120 GeV/ c 2 and lifetimes t lab > 1.2 μ s and plot invariant differential production cross sections as a function of rapidity for a variety of particles.

Strange quark matter - a status quo

Experimental techniques looking for the existence of strange quark matter (SQM) as well as its production in the laboratory are reviewed. It is focused on examples of terrestrial searches and recent experiments on relativistic particle and heavy-ion collisions which try to produce SQM in the laboratory. An outlook on future experimental possibilities is given.

An investigation of the antinuclei and nuclei production mechanism in Pb + Pb collisions at 158 A GeV

We investigate the production mechanisms of p, d, t, 3He, 4He, 6Li, , and in Pb+Pb collisions at 158xa0Axa0GeV measured near zero transverse momentum with the NA52 experiment at the CERN SPS. We find evidence that nuclei and antinuclei in Pb+Pb collisions are mainly produced via the coalescence mechanism out of a thermalized source of hadrons, at a time close to the thermal freeze-out of hadrons corresponding to a temperature of ~120xa0MeV.

Antinuclei production in heavy ion collisions at CERN SPS

Abstract Besides the dedicated search for strangelets NA52 measures light (anti)particle and (anti)nuclei production over a wide range of rapidity. Compared to previous runs the statistics has been increased in the 1998 run by more than one order of magnitude for negatively charged objects at different spectrometer rigidities. At a rigidity of −20 GeV/c we measured 106 p , 103 d and one 3 He without any centrality requirements. These preliminary results together with previous measurements near central rapidity are discussed in the framework of a thermodynamical and a coalescence model.

The NA52 strangelet and particle search in Pb+Pb collisions at 158 A GeV/c

The NA52 experiment searched for long-lived charged strangelets in 158 A GeV/c Pb+Pb collisions at CERN SPS. We collected 1013 Pb+Pb interactions looking for negatively charged strangelets and 3 × 1011 Pb+Pb interactions for positively charged ones. No evidence for the production of strangelets has been observed. The upper strangelet production limits are discussed. Besides the strangelet searches NA52 was able to identify particles and anti-particles over a wide range in rapidity. Results of the invariant differential particle production cross sections including fragments up to carbon and 5 are presented.

Antimatter and matter production in heavy ion collisions at CERN (The NEWMASS experiment NA52)

Besides the dedicated search for strangelets NA52 measures light (anti)particle and (anti)nuclei production over a wide range of rapidity. Compared to previous runs the statistics has been increased in the 1998 run by more than one order of magnitude for negatively charged objects at different spectrometer rigidities. Together with previous data taking at a rigidity of -20 GeV/c we obtained 10^6 antiprotons 10^3 antideuterons and two antihelium3 without centrality requirements. We measured nuclei and antinuclei (p,d,antiprotons, antideuterons) near midrapidity covering an impact parameter range of b=2-12 fm. Our results strongly indicate that nuclei and antinuclei are mainly produced via the coalescence mechanism. However the centrality dependence of the antibaryon to baryon ratios show that antibaryons are diminished due to annihilation and breakup reactions in the hadron dense environment. The volume of the particle source extracted from coalescence models agrees with results from pion interferometry for an expanding source. The chemical and thermal freeze-out of nuclei and antinuclei appear to coincide with each other and with the thermal freeze-out of hadrons.

Charged pion production in fixed-target Pb + Pb collisions at 158 GeV/nucleon

Changes in pion production as a function of the impact parameter of the collision or the incident energy, may reveal characteristics of a possible first-order phase transition from nuclear to quark matter, as predicted by lattice quantum chromodynamics. In this paper we investigate charged pion production in Pb+Pb collisions at 158 GeV/nucleon near 0° production angle and at forward rapidity (4.3 y6.3). The centrality dependence of pion production is shown in the impact parameter range ~ 2-12 fm at the rapidities y = 5.7 and 6.3. An enhancement in the -/+ ratio has been measured near beam rapidity, indicating Coulomb interaction of charged pions with the spectator protons. The charged pion yield per nucleon participating in the collision (Np) at y = 5.7 increases faster than linearly with Np, up to Np~100 and then it saturates, while at y = 6.3 it does not exhibit any sudden change as a function of Np.