Nuclear Transparency in Large Momentum Transfer Quasielastic Scattering

Abstract

We measured simultaneously $\mathrm{pp}$ elastic and quasielastic $(p,2p)$ scattering in hydrogen, deuterium, and carbon for momentum transfers of 4.8 to $6.2(\mathrm{GeV}/c{)}^{2}$ at incoming momenta of 5.9 and $7.5\mathrm{GeV}/c$ and center-of-mass scattering angles in the range ${\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}83.7\ifmmode^\circ\else\textdegree\fi{}--90\ifmmode^\circ\else\textdegree\fi{}$. The nuclear transparency is defined as the ratio of the quasielastic cross section to the free $\mathrm{pp}$ cross section. At incoming momentum of $5.9\mathrm{GeV}/c$, the transparency of carbon decreases by a factor of 2 from ${\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}\ensuremath{\simeq}85\ifmmode^\circ\else\textdegree\fi{}$ to ${\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}\ensuremath{\simeq}89\ifmmode^\circ\else\textdegree\fi{}$. At the largest angle the transparency of carbon increases from 5.9 to $7.5\mathrm{GeV}/c$ by more than 50%. The transparency in deuterium does not depend on incoming momentum nor on ${\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}$.