Low-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>p</mml:mi><mml:mi>T</mml:mi></mml:msub></mml:math> direct-photon production in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Au</mml:mi><mml:mo>+</mml:mo><mml:mi>Au</mml:mi></mml:mrow></mml:math> collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msqrt><mml:msub><mml:mi>s</mml:mi><mml:mrow><mml:mi>N</mml:mi><mml:mi>N</mml:mi></mml:mrow></mml:msub></mml:msqrt><mml:mo>=</mml:mo><mml:mn>39</mml:mn></mml:mrow></mml:math> and 62.4 GeV
N. J. Abdulameer, U. Acharya, A. Adare, C. Aidala, N. N. Ajitanand, Y. Akiba, R. Akimoto, H. Al-Ta'ani, J. Alexander, M. Alfred, A. Angerami, K. Aoki, N. Apadula, Yoshio Aramaki, H. Asano, E. C. Aschenauer, E. T. Atomssa, T. C. Awes, B. Azmoun, V. Babintsev, M. Bai, B. Bannier, K. N. Barish, B. Bassalleck, S. Bathe, V. Baublis, S. Baumgart, A. Bazilevsky, R. Belmont, A. Berdnikov, Y. Berdnikov, L. Bichon, B. Blankenship, D. Blau, J. S. Bok, V. Borisov, K. Boyle, M. L. Brooks, H. Buesching, V. Bumazhnov, S. Butsyk, S. Campbell, V. Canoa Roman, P. Castera, C.-H. Chen, M. Chiu, C. Y., I. J. Choi, J. B. Choi, S. Choi, R. K. Choudhury, P. Christiansen, T. Chujo, O. Chvala, V. Cianciolo, Z. H. Citron, B. Cole, M. Connors, R. Corliss, Y. Corrales Morales, M. Csanád, T. Csörgő, L. D'Orazio, S. Dairaku, A. Datta, M. S. Daugherity, G. David, C. T. Dean, A. Denisov, A. Deshpande, E. J. Desmond, K. V. Dharmawardane, O. Dietzsch, L. Ding, A. Dion, M. Donadelli, V. Doomra, O. Drapier, A. Drees, K. A. Drees, J. M. Durham, A. Durum, S. Edwards, Y. V. Efremenko, T. Engelmore, A. Enokizono, R. Esha, O. Eyser, B. Fadem, W. Fan, D. E. Fields, М. Фингер, M. Finger, D. Firak, D. Fitzgerald, F. Fleuret, S. Fokin, J. E. Frantz, A. Franz, A. D. Frawley
Abstract
The PHENIX experiment at RHIC presents a measurement of thermal photons emitted from the quark-gluon plasma produced in collisions of Au ions at $\sqrt{{s}_{N\phantom{\rule{0}{0ex}}N}}=39$ and 62.4 GeV. The yield of these photons exceeds what is expected from appropriately scaled proton collisions and is qualitatively consistent with a significant thermal contribution. Compared to results from other beam energies, the data suggest that the bulk of thermal photons are emitted under similar conditions near the transition of the quark-gluon plasma to hadronic matter.