Abstract

We report the observation of transverse polarization-dependent azimuthal correlations in charged pion pair production with the STAR experiment in p(up arrow) + p collisions at RHIC. These correlations directly probe quark transversity distributions. We measure signals in excess of 5 standard deviations at high transverse momenta, at high pseudorapidities eta > 0.5, and for pair masses around the mass of the rho meson. This is the first direct transversity measurement in p + p collisions.