- Open Access
Energy Correlators within Jets in Transversely Polarized Proton-Proton Collisions at
Phys. Rev. Lett. 137, 111902 – Published 8 September, 2026
DOI: https://doi.org/10.1103/fgsf-gx2q
Abstract
We report the first measurement of one- and two-point energy correlators within jets in transversely polarized proton-proton collisions at , using the STAR detector at the Relativistic Heavy Ion Collider. These observables quantify the energy-weighted angular distribution of single hadrons and hadron pairs within jets, respectively. Sizable spin-dependent asymmetries are observed for , , and pairs, revealing the onset of nonperturbative dynamics at specific angular scales. By projecting the fragmentation dynamics onto Mellin moments, these measurements provide sensitivity to the nucleon’s transversity while minimizing uncertainties from nonperturbative fragmentation functions. These results establish energy correlators as a novel and precise probe of nucleon structure and open a promising avenue for three-dimensional nucleon tomography at the future Electron-Ion Collider.
Physics Subject Headings (PhySH)
Article Text
Supplemental Material
References (36)
- C. L. Basham, L. S. Brown, S. D. Ellis, and S. T. Love, Energy correlations in electron-positron annihilation: Testing quantum chromodynamics, Phys. Rev. Lett. 41, 1585 (1978).
- X. Liu and H. X. Zhu, Nucleon energy correlators, Phys. Rev. Lett. 130, 091901 (2023).
- I. Moult and H. X. Zhu, Energy correlators: A journey from theory to experiment, arXiv:2506.09119.
- A. Hayrapetyan et al. (CMS Collaboration), Measurement of energy correlators inside jets and determination of the strong coupling , Phys. Rev. Lett. 133, 071903 (2024).
- S. Acharya et al. (ALICE Collaboration), Exposing the parton-hadron transition within jets with energy-energy correlators in pp collisions at (2024), arXiv:2409.12687.
- B. E. Aboona et al. (STAR Collaboration), Measurement of two-point energy correlators within jets in collisions at , Phys. Rev. Lett. 135, 111901 (2025).
- P. T. Komiske, I. Moult, J. Thaler, and H. X. Zhu, Analyzing N-point energy correlators inside jets with CMS open data, Phys. Rev. Lett. 130, 051901 (2023).
- Z.-B. Kang, K. Lee, D. Y. Shao, and F. Zhao, Probing transverse momentum dependent structures with azimuthal dependence of energy correlators, J. High Energy Phys. 03 (2024) 153.
- Y.-K. Song, S.-Y. Wei, L. Yang, and J. Zhou, Gluon polarimetry with energy-energy correlators, Phys. Rev. Lett. 136, 131901 (2026).
- G. L. Kane, J. Pumplin, and W. Repko, Transverse quark polarization in large- reactions, jets, and leptoproduction: A test of quantum chromodynamics, Phys. Rev. Lett. 41, 1689 (1978).
- X. Liu and H. X. Zhu, TMDs from semi-inclusive energy correlators, arXiv:2403.08874.
- M.-S. Gao, Z.-B. Kang, W. Li, and D. Y. Shao, Accessing nucleon transversity with one-point energy correlators, Phys. Rev. Lett. 136, 151902 (2026).
- Z.-B. Kang, A. Metz, D. Pitonyak, and C. Zhang, Simplified approach to extracting nucleon transversity in collinear factorization using near-side energy-energy correlators, arXiv:2604.28131.
- Z.-B. Kang, A. Metz, D. Pitonyak, and C. Zhang, Transverse-spin dependent energy-energy correlators in proton-proton collisions within the dihadron fragmentation framework, arXiv:2607.02441.
- L. Adamczyk et al. (STAR Collaboration), Observation of transverse spin-dependent azimuthal correlations of charged pion pairs in at , Phys. Rev. Lett. 115, 242501 (2015).
- M. Abdallah et al. (STAR Collaboration), Azimuthal transverse single-spin asymmetries of inclusive jets and identified hadrons within jets from polarized collisions at , Phys. Rev. D 106, 072010 (2022).
- W. B. Schmidke et al. (RHIC Polarimetry Group), Brookhaven National Laboratory Report No. BNL-209057-2018-TECH, 2018.
- M. Anderson et al. (STAR Collaboration), The STAR time projection chamber: A Unique tool for studying high multiplicity events at RHIC, Nucl. Instrum. Methods Phys. Res., Sect. A 499, 659 (2003).
- M. Beddo et al. (STAR Collaboration), The STAR barrel electromagnetic calorimeter, Nucl. Instrum. Methods Phys. Res., Sect. A 499, 725 (2003).
- C. Allgower et al. (STAR Collaboration), The STAR endcap electromagnetic calorimeter, Nucl. Instrum. Methods Phys. Res., Sect. A 499, 740 (2003).
- W. J. Llope (STAR Collaboration), The large-area time-of-flight upgrade for STAR, Nucl. Instrum. Methods Phys. Res., Sect. B 241, 306 (2005).
- J. Chen et al., Properties of the QCD matter: Review of selected results from the relativistic heavy ion collider beam energy scan (RHIC BES) program, Nucl. Sci. Tech. 35, 214 (2024).
- J. C. Collins, Fragmentation of transversely polarized quarks probed in transverse momentum distributions, Nucl. Phys. B396, 161 (1993).
- R. L. Jaffe, X.-m. Jin, and J. Tang, Interference fragmentation functions and the nucleon’s transversity, Phys. Rev. Lett. 80, 1166 (1998).
- M. Cacciari, G. P. Salam, and G. Soyez, The anti- jet clustering algorithm, J. High Energy Phys. 04 (2008) 063.
- M. Cacciari, G. P. Salam, and G. Soyez, fastjet user manual, Eur. Phys. J. C 72, 1896 (2012).
- H. Bichsel, A method to improve tracking and particle identification in TPCs and silicon detectors, Nucl. Instrum. Methods Phys. Res., Sect. A 562, 154 (2006).
- Y. Xu et al., Improving the calibration of the STAR TPC for the high- hadron identification, Nucl. Instrum. Methods Phys. Res., Sect. A 614, 28 (2010).
- M. Shao, O. Barannikova, X. Dong, Y. Fisyak, L. Ruan, P. Sorensen, and Z. Xu, Extensive particle identification with TPC and TOF at the STAR experiment, Nucl. Instrum. Methods Phys. Res., Sect. A 558, 419 (2006).
- G. G. Ohlsen and P. W. Keaton, Techniques for measurement of spin- and spin-1 polarization analyzing tensors, Nucl. Instrum. Methods 109, 41 (1973).
- See Supplemental Material at http://link.aps.org/supplemental/10.1103/fgsf-gx2q for detailed information of corrections and associated uncertainties.
- T. Sjostrand, S. Mrenna, and P. Z. Skands, pythia 6.4 physics and manual, J. High Energy Phys. 05 (2006) 026.
- P. Z. Skands, Tuning Monte Carlo generators: The Perugia tunes, Phys. Rev. D 82, 074018 (2010).
- R. Brun, F. Bruyant, M. Maire, A. C. McPherson, and P. Zanarini, geant3, geant3 CERN Report No. CERN-DD-EE-84-1, 1987.
- R. Barlow, Systematic errors: Facts and fictions, in Conference on Advanced Statistical Techniques in Particle Physics (Institute for Particle Physics Phenomenology, Durham, 2002), pp. 134–144.
- STAR Collaboration, Energy correlators within jets in transversely polarized proton-proton collisions at , HEPData (collection), https://www.hepdata.net/record/181828?observer_key=0c7f65fb, 10.17182/hepdata.181828 (2026).