Yerevan Physics Institute, Yerevan, Armenia.
Phys Rev Lett. 2011 Jul 29;107(5):052302. doi: 10.1103/PhysRevLett.107.052302. Epub 2011 Jul 28.
A comparison of the relative yields of Υ resonances in the μ(+)μ(-) decay channel in Pb-Pb and pp collisions at a center-of-mass energy per nucleon pair of 2.76 TeV is performed with data collected with the CMS detector at the LHC. Using muons of transverse momentum above 4 GeV/c and pseudorapidity below 2.4, the double ratio of the Υ(2S) and Υ(3S) excited states to the Υ(1S) ground state in Pb-Pb and pp collisions, Υ(2S+3S)/Υ(1S)/Υ(2S+3S)/Υ(1S), is found to be 0.31(-0.15)(+0.19)(stat)±0.03(syst). The probability to obtain the measured value, or lower, if the true double ratio is unity, is calculated to be less than 1%.
采用质心能量为 2.76 TeV 的对撞能，在 LHC 的 CMS 探测器上采集数据，对 μ(+)μ(-)衰变道中 Υ 共振的相对产额进行了 Pb-Pb 和 pp 碰撞的比较。利用横动量大于 4 GeV/c 和赝快度低于 2.4 的μ子，在 Pb-Pb 和 pp 碰撞中 Υ(2S)和 Υ(3S)激发态相对于 Υ(1S)基态的双比 Υ(2S+3S)/Υ(1S)/Υ(2S+3S)/Υ(1S)被发现为 0.31(-0.15)(+0.19)(stat)±0.03(syst)。如果真实的双比为 1%，则获得测量值或更低值的概率计算小于 1%。
