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arXiv · 1708.07080

Azimuthal transverse single-spin asymmetries of inclusive jets and charged pions within jets from polarized-proton collisions at $\sqrt{s} = 500$ GeV

STAR Collaboration·L. Adamczyk·J. R. Adams·J. K. Adkins·G. Agakishiev·M. M. Aggarwal·Z. Ahammed·N. N. Ajitanand·I. Alekseev·D. M. Anderson·R. Aoyama·A. Aparin·D. Arkhipkin·E. C. Aschenauer·M. U. Ashraf·A. Attri·G. S. Averichev·X. Bai·V. Bairathi·K. Barish·A. Behera·R. Bellwied·A. Bhasin·A. K. Bhati·P. Bhattarai·J. Bielcik·J. Bielcikova·L. C. Bland·I. G. Bordyuzhin·J. Bouchet·J. D. Brandenburg·A. V. Brandin·D. Brown·J. Bryslawskyj·I. Bunzarov·J. Butterworth·H. Caines·M. Calderón de la Barca Sánchez·J. M. Campbell·D. Cebra·I. Chakaberia·P. Chaloupka·Z. Chang·N. Chankova-Bunzarova·A. Chatterjee·S. Chattopadhyay·X. Chen·J. H. Chen·J. Cheng·M. Cherney·W. Christie·G. Contin·H. J. Crawford·S. Das·T. G. Dedovich·J. Deng·I. M. Deppner·A. A. Derevschikov·L. Didenko·C. Dilks·X. Dong·J. L. Drachenberg·J. E. Draper·J. C. Dunlop·L. G. Efimov·N. Elsey·J. Engelage·G. Eppley·R. Esha·S. Esumi·O. Evdokimov·J. Ewigleben·O. Eyser·R. Fatemi·S. Fazio·P. Federic·P. Federicova·J. Fedorisin·Z. Feng·P. Filip·E. Finch·Y. Fisyak·C. E. Flores·J. Fujita·L. Fulek·C. A. Gagliardi·F. Geurts·A. Gibson·M. Girard·D. Grosnick·D. S. Gunarathne·Y. Guo·A. Gupta·W. Guryn·A. I. Hamad·A. Hamed·A. Harlenderova·J. W. Harris·L. He·S. Heppelmann
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Abstract

We report the first measurements of transverse single-spin asymmetries for inclusive jet and jet + $\pi^{\pm}$ production at midrapidity from transversely polarized proton-proton collisions at $\sqrt{s} = 500$ GeV. The data were collected in 2011 with the STAR detector sampled from 23 pb$^{-1}$ integrated luminosity with an average beam polarization of 53%. Asymmetries are reported for jets with transverse momenta $6 < p_{T, jet} < 55$ GeV/c and pseudorapidity $|\eta| < 1$. Presented are measurements of the inclusive-jet azimuthal transverse single-spin asymmetry, sensitive to twist-3 initial-state quark-gluon correlators; the Collins asymmetry, sensitive to quark transversity coupled to the polarized Collins fragmentation function; and the first measurement of the "Collins-like" asymmetry, sensitive to linearly polarized gluons. Within the present statistical precision, inclusive-jet and Collins-like asymmetries are small, with the latter allowing the first experimental constraints on gluon linear polarization in a polarized proton. At higher values of jet transverse momenta, we observe the first non-zero Collins asymmetries in polarized-proton collisions, with a statistical significance of greater than $5\sigma$. The results span a range of x similar to results from SIDIS but at much higher $Q^{2}$. The Collins results enable tests of universality and factorization-breaking in the transverse momentum-dependent formulation of perturbative quantum chromodynamics.

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STAR Collaboration, L. Adamczyk, J. R. Adams, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, N. N. Ajitanand, I. Alekseev, D. M. Anderson, R. Aoyama, A. Aparin, D. Arkhipkin, E. C. Aschenauer, M. U. Ashraf, A. Attri, G. S. Averichev, X. Bai, V. Bairathi, K. Barish, A. Behera, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. Bouchet, J. D. Brandenburg, A. V. Brandin, D. Brown, J. Bryslawskyj, I. Bunzarov, J. Butterworth, H. Caines, M. Calderón de la Barca Sánchez, J. M. Campbell, D. Cebra, I. Chakaberia, P. Chaloupka, Z. Chang, N. Chankova-Bunzarova, A. Chatterjee, S. Chattopadhyay, X. Chen, J. H. Chen, J. Cheng, M. Cherney, W. Christie, G. Contin, H. J. Crawford, S. Das, T. G. Dedovich, J. Deng, I. M. Deppner, A. A. Derevschikov, L. Didenko, C. Dilks, X. Dong, J. L. Drachenberg, J. E. Draper, J. C. Dunlop, L. G. Efimov, N. Elsey, J. Engelage, G. Eppley, R. Esha, S. Esumi, O. Evdokimov, J. Ewigleben, O. Eyser, R. Fatemi, S. Fazio, P. Federic, P. Federicova, J. Fedorisin, Z. Feng, P. Filip, E. Finch, Y. Fisyak, C. E. Flores, J. Fujita, L. Fulek, C. A. Gagliardi, F. Geurts, A. Gibson, M. Girard, D. Grosnick, D. S. Gunarathne, Y. Guo, A. Gupta, W. Guryn, A. I. Hamad, A. Hamed, A. Harlenderova, J. W. Harris, L. He, S. Heppelmann. 2017-08-23. Azimuthal transverse single-spin asymmetries of inclusive jets and charged pions within jets from polarized-proton collisions at $\sqrt{s} = 500$ GeV. https://doi.org/10.1103/physrevd.97.032004

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