2022 Impact factor 4.4
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

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.

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