标题： HERA处的弹性rho产生 显示英文标题

标题： Elastic rho production at HERA

摘要： 弹性ρ介子的电子生产结果在光子虚度范围1 < Q^2 < 60 GeV^2和强子质心系能量范围30 < W < 140 GeV内给出。 (pi pi)质量分布的形状被讨论，并给出了截面依赖于Q^2、W和t（质子的四动量转移平方）的测量结果。 完整的一组ρ自旋密度矩阵元素被测量，提供了关于ρ介子和光子极化状态的信息。 特别是，纵向与横向gamma^*p截面的比值R被确定。 显示英文摘要

摘要： Results on elastic electroproduction of rho mesons are presented for a photon virtuality in the range 1 < Q^2 < 60 GeV^2 and for a hadronic centre of mass energy in the range 30 < W < 140 GeV. The shape of the (pi pi) mass distribution is discussed and measurements of the cross section dependences on Q^2, W and t (the four-momentum transfer squared to the proton) are presented. The full set of rho spin density matrix elements is measured, providing information on the rho meson and on the photon polarisation states. In particular, the ratio R of longitudinal to transverse gamma^*p cross section is determined.