2—5GeV能区的R值测量

MEASUREMENT OF R AT ENERGIES BETWEEN 2-5GeV

作为粒子物理中的一个基本参数 ,R值在发展粒子物理理论及检验标准模型 (SM )方面起着重要的作用 .在低能区精确测量R值的实验努力对于弱电精确物理是至关重要的 .R值测量不仅对α(M2Z)的计算及aμ 的解释是重要的 ,而且对强子产生机制和经e+e-湮没产生的粲偶素本身的理解也是必须的 .文章简要报道了在北京正负电子对撞机 (BEPC)和升级的北京谱仪 (BES Ⅱ )

Being one of the fundamental parameters in particle physics,the R value plays an important role in the development of the theory of particle physics and in testing the Standard Model(SM).Experimental efforts to precisely measure R value at low energies are crucial for the electroweak precision physics.The R measurements are not only important for the evaluation of α(M \+2\-Z) and for the interpretation of a \-μ,but also necessary for the understanding of the hadron production mechanism and the charmonium itself produced via e\++e\+- annihilation.This article briefly reports the R scan done with the upgraded Beijing Spectrometer(BES\|Ⅱ) at the Beijing Electron Positron Collider(BEPC) and its physics results.