Measurements of positrons from pair production in Coulomb collisions of 33-TeV lead ions with fixed targets

Strong suppression of Coulomb corrections to the e + e − pair production cross section in ultrarelativistic nuclear collisions

“…We found considerable reduction of the Coulomb corrections even for large γAγB due to the suppression of the production of e + e − pair with the total energy of the order of a few electron masses in the rest frame of one of the nuclei. Our result explains why the deviation from the Born result were not observed in the experiment at SPS [1,2]. Electron-positron pair production in ultrarelativistic nuclear collisions is investigated intensively during almost two last decades, see recent reviews [3,4].…”

“…However, we can claim that, due to the strong compensation between the leading term and the correction, the Coulomb corrections σ A are much smaller than σ A LA at γ 500. Therefore, this naturally explains why there was no evidence of the Coulomb corrections in the experiments [1,2].…”

“…[8]. Thus absence of the Coulomb corrections in the experiments [1,2] has remained unexplained. In the present paper, we explain this experimental result by the suppression of the Coulomb corrections due to the account of the next-to-leading term.…”

Publisher's Note: Calculation of heavy ione+e−pair production to all orders inZα[Phys. Rev. C 71, 024901 (2005)]

“…An extended discussion and reanalyis of this solution, with comments on early parallel work in the literature, shortly followed [10]. Baltz and McLerran[8] noted the apparent agreement of the obtained amplitude with that of perturbation theory even for large Z. Segev and Wells [9] further noted the perturbative scaling with Z 2 1 Z 2 2 seen in CERN SPS data [11]. These data were obtained from reactions of 160 GeV/nucleon Pb ions on C, Al, Pa, and Au targets as well as from 200 Gev/nucleon S ions on the same C, Al, Pa, and Au targets.…”

Atomic collisions at ultrarelativistic energies

“…Availability of beams of ultrarelativistic heavy ions at the CERN SPS enabled experimental studies of a variety of basic atomic collision phenomena in gases and solids, including radiative electron capture and electron capture from pair production, total energy loss, ionization and electron loss to continuum, and ion channeling. Results of some of these measurements and comparisons with theoretical treatments will be presented, as well as a number of remaining puzzles presented by the data.Experimental studies of the interactions of heavy ultrarelativistic ions with matter were carried out at the CERN SPS in the 1990's covering a variety of fundamental atomic collisional phenomena in gases and solids, including -differential measurements of binary encounter or knock-on electrons [1], free electron-positron pair production in Coulomb collisions [2,3], precise measurements of total energy loss [4], projectile electron capture through electron capture from pair production (ECPP) [5,6] and radiative electron capture (REC) of target electrons [7], projectile total ionization [5,6], electron loss to the projectile continuum [8], and ion channeling [9]. Results of several of these measurements have lead to important revisions and improvements of theory.…”