Systematic study of low-mass electron pair production in p–Be and p–Au collisions at 450 GeV/$c$

G. Agakichiev - et al.

doi:doi:10.1007/PL00021659

2023 Impact factor 4.2

Particles and Fields

Eur. Phys. J. C 4, 231-247
DOI 10.1007/s100529800874

Systematic study of low-mass electron pair production in p-Be and p-Au collisions at 450 GeV/c

G. Agakichiev¹ - M. Appenheimer² - R. Averbeck³ - F. Ballester⁴ - R. Baur⁵ - A. Brenschede² - J. Diaz⁴ - A. Drees⁵ - U. Faschingbauer¹ - J.L. Ferrero⁴ - P. Fischer⁵ - Z. Fraenkel⁶ - M. Franke² - Ch. Fuchs¹ - E. Gatti⁷ - P. Glässel⁵ - Th. Günzel⁵ - C. P. de los Heros⁶ - F. Hess¹ - R. Holzmann³ - V. Iourevitch⁸ - D. Irmscher⁵ - C. Jacob¹ - W. Kühn² - B. Lenkeit⁵ - H. Löhner⁹ - A. Marin⁴ - F.M. Marques⁴ - G. Martinez⁴ - V. Metag² - M. Notheisen² - R. Novotny² - L. H. Olsen⁵ - R. Ostendorf¹⁰ - Y. Panebrattsev¹ - A. Pfeiffer⁵ - I. Ravinovich⁶ - P. Rehak¹¹ - M. Sampietro⁷ - A. Schön⁵ - J. Schukraft⁸ - Y. Schutz¹⁰ - S. Shimansky⁸ - A. Shor⁶ - R.S. Simon³ - H. J. Specht⁵ - V. Steiner⁶ - S. Tapprogge⁵ - G. Tel-Zur⁶ - I. Tserruya⁶ - Th. Ullrich⁵ - H. Wilschut⁹ - J. P. Wurm¹

¹ Max-Planck-Institut für Kernphysik, D-69117 Heidelberg, Germany
² II. Physikalisches Institut der Universität Gießen, D-35392 Gießen, Germany
³ GSI, D-64220 Darmstadt, Germany
⁴ Instituto Fisica Corpuscular, E-46100 Burjassot Valencia, Spain
⁵ Physikalisches Institut der Universität Heidelberg, D-69120 Heidelberg, Germany
⁶ Weizmann Institute of Science, Rehovot 76100, Israel
⁷ Politecnico di Milano, I-20133 Milano, Italy
⁸ CERN, CH-1211 Geneva 23, Switzerland
⁹ Kernphysisch Versneller Institut, NL-9747AA Groningen, Netherlands
¹⁰ GANIL, F-14021 Caen, France
¹¹ Brookhaven National Laboratory, Upton, NY 11973, USA

Received: 2 July 1997 / Published online: 5 June 1998

Abstract
In a joint effort the CERES/NA45 and TAPS collaborations have measured low-mass electron pairs in p-Be and p-Au collisions at 450 GeV/c at the CERN SPS. In the range covered up to $\approx$ 1.5 GeV/c² the mass spectra from p-Be and p-Au collisions are well explained by electron pairs from decays of neutral mesons. For p-Au our result is new. For p-Be, the simultaneously measured electron pairs and photons served as a direct measure of the $\eta$ Dalitz decay contribution to the inclusive pair spectrum in which instrumental uncertainties are highly reduced. We confirm the earlier finding of HELIOS-1 with significantly reduced systematic uncertainties of 23% in the mass range below 450 MeV/c², and of 28% in the mass range above 750 MeV/c² at 90% confidence limit. Any unconventional source of electron pairs is limited by these error margins as the percentage fraction of the hadronic contribution.