Measurement of Sequential <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">ϒ</mml:mi></mml:math> Suppression in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><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" display="inline"><mml:mrow><mml:msqrt><mml:mrow><mml:msub><mml:mrow><mml:mi>s</mml:mi></mml:mrow><mml:mrow><mml:mi>N</mml:mi><mml:mi>N</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:msqrt><mml:mo>=</mml:mo><mml:mn>200</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>GeV</mml:mi></mml:mrow></mml:math> with the STAR Experiment
B. E. Aboona, J. Adam, L. Adamczyk, J. R. Adams, I. Aggarwal, M. M. Aggarwal, Z. Ahammed, D. M. Anderson, E. C. Aschenauer, Jennifer Atchison, V. Bairathi, W. Baker, J. Ball, K. Barish, R. Bellwied, P. Bhagat, A. Bhasin, S. Bhatta, J. Bielcik, J. Bielcikova, J. D. Brandenburg, X. Z. Cai, H. Caines, M. Calderon De La Barca Sanchez, D. Cebra, J. Ceska, I. Chakaberia, P. Chaloupka, B. K. Chan, Z. Chang, D. Chen, J. Chen, J. H. Chen, Z. Chen, J. Cheng, Yaodong Cheng, S. Choudhury, W. Christie, X. Chu, H. J. Crawford, M. Csanád, G. Dale-Gau, A. Das, M. Daugherity, I. M. Deppner, A. Dhamija, L. Di Carlo, L. Didenko, P. Dixit, X. Dong, J. L. Drachenberg, E. Duckworth, J. C. Dunlop, J. Engelage, G. Eppley, S. Esumi, O. Evdokimov, A. Ewigleben, O. Eyser, R. Fatemi, S. Fazio, C. Feng, Y. Feng, E. Finch, Y. Fisyak, F. A. Flor, C. D. Fu, C. A. Gagliardi, T. Galatyuk, F. J. M. Geurts, N. Ghimire, A. Gibson, K. Gopal, X. Gou, D. Grosnick, A. Gupta, W. Guryn, A. Hamed, Y. F. Han, S. Harabasz, M. D. Harasty, J. W. Harris, H. Harrison, W. He, Xin He, Y. He, S. Heppelmann, N. Herrmann, L. Holub, C. Hu, Qi Hu, Y. Hu, H. Z. Huang, H. Z. Huang, S. L. Huang, T. Huang, X. Huang, Y. Huang, Y. Huang, T. J. Humanic
Abstract
We report on measurements of sequential $\mathrm{\ensuremath{\Upsilon}}$ suppression in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{GeV}$ with the STAR detector at the Relativistic Heavy Ion Collider (RHIC) through both the dielectron and dimuon decay channels. In the 0%--60% centrality class, the nuclear modification factors (${R}_{AA}$), which quantify the level of yield suppression in heavy-ion collisions compared to $p+p$ collisions, for $\mathrm{\ensuremath{\Upsilon}}(1S)$ and $\mathrm{\ensuremath{\Upsilon}}(2S)$ are $0.40\ifmmode\pm\else\textpm\fi{}0.03(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.03(\mathrm{sys})\ifmmode\pm\else\textpm\fi{}0.09(\mathrm{norm})$ and $0.26\ifmmode\pm\else\textpm\fi{}0.08(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.02(\mathrm{sys})\ifmmode\pm\else\textpm\fi{}0.06(\mathrm{norm})$, respectively, while the upper limit of the $\mathrm{\ensuremath{\Upsilon}}(3S)$ ${R}_{AA}$ is 0.17 at a 95% confidence level. This provides experimental evidence that the $\mathrm{\ensuremath{\Upsilon}}(3S)$ is significantly more suppressed than the $\mathrm{\ensuremath{\Upsilon}}(1S)$ at RHIC. The level of suppression for $\mathrm{\ensuremath{\Upsilon}}(1S)$ is comparable to that observed at the much higher collision energy at the Large Hadron Collider. These results point to the creation of a medium at RHIC whose temperature is sufficiently high to strongly suppress excited $\mathrm{\ensuremath{\Upsilon}}$ states.