We report the observation of transverse polarization-dependent azimuthal correlations in charged pion pair production with the STAR experiment in p+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 η>0.5, and for pair masses around the mass of the ρ meson. This is the first direct transversity measurement in p+p collisions.

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Published in Physical Review Letters, v. 115, no. 24, article 242501, p. 1-7.

© 2015 American Physical Society

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Due to the large number of authors involved, only the first 10 and the ones affiliated with the University of Kentucky are listed in the author section above. The authors of this article are collectively known as STAR Collaboration. To see a full list of authors, please download this article or visit: http://dx.doi.org/10.1103/PhysRevLett.115.242501.

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This work was supported in part by the Office of Nuclear Physics within the U.S. DOE Office of Science, the U.S. NSF, the Ministry of Education and Science of the Russian Federation, NNSFC, CAS, MoST, and MoE of China, the Korean Research Foundation, GA and MSMT of the Czech Republic, FIAS of Germany, DAE, DST, and UGC of India, the National Science Centre of Poland, National Research Foundation, the Ministry of Science, Education and Sports of the Republic of Croatia, and RosAtom of Russia.

SupplementalInformation.pdf (105 kB)
The supplemental material contains data tables of the results and the kinematics sampled.