Low mass dimuon production in proton and ion induced interactions at the SPS

The NA38 and NA50 Collaborations:     M.C. Abreu - et al.

doi:doi:10.1007/s100520000288

2021 Impact factor 4.991

Particles and Fields

Eur. Phys. J. C 13, 69-78
DOI 10.1007/s100520000288

Low mass dimuon production
in proton and ion induced interactions at the SPS

The NA38 and NA50 Collaborations

M.C. Abreu^7,a - B. Alessandro¹² - C. Alexa⁴ - R. Arnaldi¹² - J. Astruc⁹ - M. Atayan¹⁴ - C. Baglin² - A. Baldisseri² - A. Baldit³ - M. Bedjidian¹³ - F. Bellaiche¹³ - S. Beolè¹² - V. Boldea⁴ - P. Bordalo^7,b - A. Bussière² - V. Capony² - L. Casagrande⁷ - J. Castor³ - T. Chambon³ - B. Chaurand¹⁰ - I. Chevrot³ - B. Cheynis¹³ - E. Chiavassa¹² - C. Cicalò⁵ - M.P. Comets⁹ - N. Constans¹⁰ - S. Constantinescu⁴ - D. Contardo¹³ - A. De Falco⁵ - G. Dellacasa¹ - N. De Marco¹² - E. Descroix^13,c - A. Devaux³ - S. Dita⁴ - O. Drapier¹³ - B. Espagnon³ - J. Fargeix³ - R. Ferreira⁷ - S.N. Filippov⁸ - F. Fleuret¹⁰ - P. Force³ - M. Gallio¹² - Y.K. Gavrilov⁸ - C. Gerschel⁹ - P. Giubellino¹² - M.B. Golubeva⁸ - M. Gonin¹⁰ - P. Gorodetzky^11,d - A.A. Grigorian¹⁴ - J.Y. Grossiord¹³ - F.F. Guber⁸ - A. Guichard¹³ - J.P. Guillaud² - H. Gulkanyan¹⁴ - R. Hakobyan¹⁴ - R. Haroutunian¹³ - M. Idzik^12,e - D. Jouan⁹ - T.L. Karavitcheva⁸ - L. Kluberg¹⁰ - R. Kossakowski² - A.B. Kurepin⁸ - Y. Le Bornec⁹ - P. Liaud² - C. Lourenço^6,* - M. Mac Cormick⁹ - P. Macciotta⁵ - A. Marzari-Chiesa¹² - M. Masera¹² - A. Masoni⁵ - S. Mehrabyan¹⁴ - M. Monteno¹² - S. Mourgues³ - A. Musso¹² - F. Ohlsson-Malek^13,f - P. Petiau¹⁰ - A. Piccotti¹² - J.R. Pizzi¹³ - F. Prino¹² - G. Puddu⁵ - C. Quintans⁷ - C. Racca¹¹ - L. Ramello¹ - S. Ramos⁷b - P. Rato-Mendes¹² - L. Riccati¹² - A. Romana¹⁰ - B. Ronceux² - I. Ropotar⁶ - P. Saturnini³ - E. Scomparin^6,g - S. Serci⁵ - R. Shahoyan^7,h - S. Silva⁷ - M. Sitta¹ - C. Soave¹² - P. Sonderegger^6,b - F. Staley² - X. Tarrago⁹ - N.S. Topilskaya⁸ - G.L. Usai⁵ - J. Varela⁷b,i - E. Vercellin¹² - N. Willis⁹

¹Università del Piemonte Orientale, Alessandria and INFN-Torino, Italy
²Laboratoire de Physique des Particules (LAPP), IN2P3-CNRS, Annecy-le-Vieux, France
³Laboratoire de Physique Corpusculaire (LPC), Université Blaise Pascal, IN2P3-CNRS, Aubière, France
⁴Institute of Atomic Physics (IFA), Bucharest, Romania
⁵Università di Cagliari/INFN, Cagliari, Italy
⁶CERN, Geneva, Switzerland
⁷Laboratório de Instrumentação e Física Experimental de Partículas (LIP), Lisbon, Portugal
⁸Institute for Nuclear Research (INR), Moscow, Russia
⁹Institut de Physique Nucléaire de Orsay (IPNO), Université Paris-Sud, IN2P3-CNRS, Orsay, France
¹⁰Laboratoire de Physique Nucléaire des Hautes Energies (LPNHE), Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France
¹¹Centre de Recherches Nucléaires, Université Louis Pasteur, IN2P3-CNRS, Strasbourg, France
¹²Università di Torino/INFN, Torino, Italy
¹³Institut de Physique Nucléaire de Lyon (IPNL), Université Claude Bernard, IN2P3-CNRS, Villeurbanne, France
¹⁴Yerevan Physics Institute (YerPhI), Yerevan, Armenia
^aAlso at UCEH, Universidade do Algarve, Faro, Portugal
^bAlso at IST, Universidade Técnica de Lisboa, Lisbon, Portugal
^cNow at Université Jean Monnet, Saint-Etienne, France
^dNow at PCC Collège de France, Paris, France
^eNow at FPNT, University of Mining and Metallurgy, Cracow, Poland
^fNow at ISN, University Joseph Fourier and CNRS-IN2P3, Grenoble, France
^gNow at Università di Torino/INFN, Torino, Italy
^hOn leave of absence from YerPhI, Yerevan, Armenia
ⁱNow at CERN, Geneva, Switzerland
^*Corresponding author: Carlos.Lourenco@cern.ch

Received: 14 July 1999 / Revised version: 3 November 1999 /
Published online: 27 January 2000 - © Springer-Verlag 2000

Abstract
The low mass dimuon spectra collected in p-U collisions by the NA38 experiment significantly exceeds the total cross section expected from previous analysis, done by other experiments. The `excess' events have a harder p_T distribution than the muon pairs from $\eta$ and $\omega$ Dalitz decays, expected to dominate the mass window 0.4-0.65GeV/c². We conjecture that the excess events may be due to $q\bar{q}$ annihilations, negligible at low p_T but made visible by the m_T cut applied in the NA38 data. Taking this assumption to parametrise the p-U spectra, we proceed with the corresponding analysis of the S-Cu, S-U and Pb-Pb data, collected by the NA38 and NA50 experiments, comparing the measured low mass dimuon spectra with the `expected cocktail'.