标题： 用入射束流研究 CM 能量区间为 1.5-3 GeV 的$\ep\en$碰撞 在\babar 入射束流下的能量区域 显示英文标题

标题： Study of $\ep\en$ Collisions in the 1.5-3 Gev C.M. Energy Region Using Isr at \babar

摘要： A preliminary analysis of low-energy $\ep\en$ collision data produced via initial state radiation (ISR) has been performed using 22 $fb^{-1}$ of \babar d̃ata. 伴随发射初始态辐射硬光子的$\mumu$、$\pipi$、$\kk$、$p \bar p$、$\kk\pi^0$、3$\pi$、4$\pi$、5$\pi$、6$\pi$、7$\pi$最终态的数据样本的选择已得到展示。 强子末态的不变质量定义了有效的对撞c.m.能量，因此\babar 的ISR数据可以与相关的直接$\ep\en$测量进行比较。所得分布已经在1.4至3.0 GeV的能量范围内与DCI和ADONE数据具有竞争力。特别是，它们不会受到某些反应中相对归一化不确定性的影响，当不同实验的结果被综合时，这些不确定性会在特定反应中显现。最终，此类数据可能用于测量R（即$\ep\en\to hadrons$和$\ep\en\to\mumu$截面之比）在低能区的能量依赖性，在此区域精确测量将对新的$(g-2)_{\mu}$测量的解释产生影响。 显示英文摘要

摘要： A preliminary analysis of low-energy $\ep\en$ collision data produced via initial state radiation (ISR) has been performed using 22 $fb^{-1}$ of \babar \~data. The selection of data samples corresponding to the $\mumu$, $\pipi$, $\kk$, $p \bar p$, $\kk\pi^0$, 3$\pi$, 4$\pi$, 5$\pi$, 6$\pi$, 7$\pi$ final states accompanied by the emitted ISR hard photon has been demonstrated. The invariant mass of the hadronic final state defines the effective collision c.m. energy, and so \babar ISR data can be compared to the relevant direct $\ep\en$ measurements. The resulting distributions are already competitive with DCI and ADONE data in the 1.4-3.0 GeV energy range. In particular, they do not suffer from the relative normalization uncertainties observed for certain reactions when results from different experiments are combined. Eventually, such data may be used to measure the energy dependence of R, the ratio of the $\ep\en\to hadrons$ and $\ep\en\to\mumu$ cross sections, in the low-energy regime where precise measurements will have an impact on the interpretation of the new $(g-2)_{\mu}$ measurements.