# Azimuthal transverse single-spin asymmetries of inclusive jets and charged pions within jets from polarized-proton collisions at root s=500 GeV

Adamczyk, L, Adams, JR, Adkins, JK, Agakishiev, G, Aggarwal, MM, Ahammed, Z, Ajitanand, NN, Alekseev, I, Anderson, DM, Aoyama, R
et al (show 340 more authors) (2018) Azimuthal transverse single-spin asymmetries of inclusive jets and charged pions within jets from polarized-proton collisions at root s=500 GeV. PHYSICAL REVIEW D, 97 (3). 032004-.

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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.

Item Type: Article 19 pages, 13 figures; Changes for version 2, as accepted by PRD: additional figure (new Fig. 2) comparing kinematic range of these data to existing DIS data, minor text updates for clarity hep-ex, hep-ex, nucl-ex Symplectic Admin 30 Apr 2019 09:38 19 Jan 2023 00:53 10.1103/PhysRevD.97.032004 https://doi.org/10.1103/PhysRevD.97.032004 https://livrepository.liverpool.ac.uk/id/eprint/3039030