Cross sections for proton knockout observed in ($e$,$e^{\prime }p$) reactions are apparently quenched by a factor of $\sim 0.5$, an effect attributed to short-range correlations between nucleons. Here we demonstrate that such quenching is not restricted to proton knockout, but a more general phenomenon associated with any nucleon transfer. Measurements of absolute cross sections on a number of targets between ${}^{16}\mathrm{O}$ and ${}^{208}\mathrm{Pb}$ were analyzed in a consistent way, with the cross sections reduced to spectroscopic factors through the distorted-wave Born approximation with global optical potentials. Across the 124 cases analyzed here, induced by various proton- and neutron-transfer reactions and with angular momentum transfer $\ell =0–7$, the results are consistent with a quenching factor of 0.55. This is an apparently uniform quenching of single-particle motion in the nuclear medium. The effect is seen not only in ($d$,$p$) reactions but also in reactions with $A=3$ and 4 projectiles, when realistic wave functions are used for the projectiles.

• Received 20 June 2013

DOI:https://doi.org/10.1103/PhysRevLett.111.042502