Phys. Rev. Lett.
85,
3595–3599
(2000)
Observation of Direct Photons in Central 158A GeV 208P208b+Pb Collisions
M. M. Aggarwal et al. (WA98 Collaboration)
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M. M. Aggarwal1, A. Agnihotri2, Z. Ahammed3, A. L. S. Angelis4, V. Antonenko5, V. Arefiev6, V. Astakhov6, V. Avdeitchikov6, T. C. Awes7, P. V. K. S. Baba8, S. K. Badyal8, C. Barlag9, S. Bathe9, B. Batiounia6, T. Bernier10, K. B. Bhalla2, V. S. Bhatia1, C. Blume9, R. Bock11, E.-M. Bohne9, Z. Böröcz9, D. Bucher9, A. Buijs12, H. Büsching9, L. Carlen13, V. Chalyshev6, S. Chattopadhyay3, R. Cherbatchev5, T. Chujo14, A. Claussen9, A. C. Das3, M. P. Decowski18, H. Delagrange10, V. Djordjadze6, P. Donni4, I. Doubovik5, S. Dutt8, M. R. Dutta Majumdar3, K. El Chenawi13, S. Eliseev15, K. Enosawa14, P. Foka4, S. Fokin5, M. S. Ganti3, S. Garpman13, O. Gavrishchuk6, F. J. M. Geurts12, T. K. Ghosh16, R. Glasow9, S. K. Gupta2, B. Guskov6, H. Å. Gustafsson13, H. H. Gutbrod10, R. Higuchi14, I. Hrivnacova15, M. Ippolitov5, H. Kalechofsky4, R. Kamermans12, K.-H. Kampert9, K. Karadjev5, K. Karpio17, S. Kato14, S. Kees9, C. Klein-Bösing9, S. Knoche9, B. W. Kolb11, I. Kosarev6, I. Koutcheryaev5, T. Krümpel9, A. Kugler15, P. Kulinich18, M. Kurata14, K. Kurita14, N. Kuzmin6, I. Langbein11, A. Lebedev5, Y. Y. Lee11, H. Löhner16, L. Luquin10, D. P. Mahapatra19, V. Manko5, M. Martin4, G. Martínez10, A. Maximov6, G. Mgebrichvili5, Y. Miake14, Md. F. Mir8, G. C. Mishra19, Y. Miyamoto14, B. Mohanty19, M.-J. Mora10, D. Morrison20, D. S. Mukhopadhyay3, H. Naef4, B. K. Nandi19, S. K. Nayak10, T. K. Nayak3, S. Neumaier11, A. Nianine5, V. Nikitine6, S. Nikolaev5, P. Nilsson13, S. Nishimura14, P. Nomokonov6, J. Nystrand13, F. E. Obenshain20, A. Oskarsson13, I. Otterlund13, M. Pachr15, S. Pavliouk6, T. Peitzmann9, V. Petracek15, W. Pinganaud10, F. Plasil7, U. v. Poblotzki9, M. L. Purschke11, J. Rak15, R. Raniwala2, S. Raniwala2, V. S. Ramamurthy19, N. K. Rao8, F. Retiere10, K. Reygers9, G. Roland18, L. Rosselet4, I. Roufanov6, C. Roy10, J. M. Rubio4, H. Sako14, S. S. Sambyal8, R. Santo9, S. Sato14, H. Schlagheck9, H.-R. Schmidt11, Y. Schutz10, G. Shabratova6, T. H. Shah8, I. Sibiriak5, T. Siemiarczuk17, D. Silvermyr13, B. C. Sinha3, N. Slavine6, K. Söderström13, N. Solomey4, G. Sood1, S. P. Sørensen7,20, P. Stankus7, G. Stefanek17, P. Steinberg18, E. Stenlund13, D. Stüken9, M. Sumbera15, T. Svensson13, M. D. Trivedi3, A. Tsvetkov5, L. Tykarski17, J. Urbahn11, E. C. v. d. Pijll12, N. v. Eijndhoven12, G. J. v. Nieuwenhuizen18, A. Vinogradov5, Y. P. Viyogi3, A. Vodopianov6, S. Vörös4, B. Wysłouch18, K. Yagi14, Y. Yokota14, and G. R. Young7 (WA98 Collaboration)
1University of Panjab, Chandigarh 160014, India
2University of Rajasthan, Jaipur 302004, Rajasthan, India
3Variable Energy Cyclotron Centre, Calcutta 700 064, India
4University of Geneva, CH-1211 Geneva 4, Switzerland
5RRC “Kurchatov Institute,” RU-123182 Moscow, Russia
6Joint Institute for Nuclear Research, RU-141980 Dubna, Russia
7Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372
8University of Jammu, Jammu 180001, India
9University of Münster, D-48149 Münster, Germany
10SUBATECH, Ecole des Mines, Nantes, France
11Gesellschaft für Schwerionenforschung (GSI), D-64220 Darmstadt, Germany
12Universiteit Utrecht/NIKHEF, NL-3508 TA Utrecht, The Netherlands
13University of Lund, SE-221 00 Lund, Sweden
14University of Tsukuba, Ibaraki 305, Japan
15Nuclear Physics Institute, CZ-250 68 Rez, Czech Republic
16KVI, University of Groningen, NL-9747 AA Groningen, The Netherlands
17Institute for Nuclear Studies, 00-681 Warsaw, Poland
18MIT, Cambridge, Massachusetts 02139
19Institute of Physics, 751-005 Bhubaneswar, India
20University of Tennessee, Knoxville, Tennessee 37966
Received 13 June 2000; published in the issue dated 23 October 2000
A measurement of direct photon production in 208Pb+208Pb collisions at 158A GeV has been carried out in the CERN WA98 experiment. The invariant yield of direct photons in central collisions is extracted as a function of transverse momentum in the interval 0.5<pT<4GeV/c. A significant direct photon signal, compared to statistical and systematical errors, is seen at pT>1.5GeV/c. The result constitutes the first observation of direct photons in ultrarelativistic heavy-ion collisions. It could be significant for diagnosis of quark-gluon-plasma formation.
© 2000 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevLett.85.3595
DOI:
10.1103/PhysRevLett.85.3595
PACS:
25.75.-q, 12.38.Mh, 24.85.+p
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