Journal Article

Measurement of the generalized spin polarizabilities of the neutron in the low-Q2 region

Bailey, Stephanie L, Stringer, Robert, Vacheret Antonin, McCormick, Kathleen R, Kim, Wooyoung, Lhuillier, David, Zhu, Lingyan, Denton, Joseph D, Ulmer, Paul E, Chao, Peng, Lindgren, Richard, Lagamba Luigi, de Jager Cornelis W, Gayou Olivier, Keister, Kathryn E, Liyanage Nilanga, Ngyen, Ton, Coman Luminita, Hai-Jiang, Lu, Cusanno Francesco, Saha Arun, Craver Brandon, Ransome, Ronald D, Holmstrom, Timothy, Solvignon, Patricia, Puckett, Andrew, Wojtsekhowski Bogdan, Averett, Todd, Kelleher, Aidan, Kaufman, Lisa J, Moffit, Bryan, Monaghan, Peter, Kolarkar Ameya, Higinbotham, Douglas W, Abrahamyan Sergey, Margaziotis, Demetrius J, Snyder, Ryan, Camsonne Alexandre, Beck, Arie, Choi Seonho, Nanda Sirish, Gomez, Javier, Hansen Jens-Ole, Kumbartzki Gerfried, Zheng Xiaochao, Bertin, Pierre, Armstrong, David S, Yuan, Jing, Deur Alexandre, Roché Rikki, Slifer Karl, Singh, Jaideep T, Kolb, Norm, Yi, Qiang, Yao Huan, Chia-Cheh, Chang, Finn, John M, Niedziela, Jennifer, Cates, Gordon D, Shabetai, Alexander, Potokar Milan, Subedi Ramesh, Reitz Bodo, Niskin Mikhail, Širca Simon, Kramer, Kevin, Paschke, Kent D, Zein-Eddine, Meziani, Gil

2021

Overview

Understanding the nucleon spin structure in the regime where the strong interaction becomes truly strong poses a challenge to both experiment and theory. At energy scales below the nucleon mass of about 1 GeV, the intense interaction among the quarks and gluons inside the nucleon makes them highly correlated. Their coherent behaviour causes the emergence of effective degrees of freedom, requiring the application of non-perturbative techniques such as chiral effective field theory1. Here we present measurements of the neutron’s generalized spin polarizabilities that quantify the neutron’s spin precession under electromagnetic fields at very low energy-momentum transfer squared down to 0.035 GeV2. In this regime, chiral effective field theory calculations2–4 are expected to be applicable. Our data, however, show a strong discrepancy with these predictions, presenting a challenge to the current description of the neutron’s spin properties.Measurements of observables sensitive to the neutron’s spin precession are extended to a regime that probes distances of the size of the nucleon. They are found to disagree with predictions from chiral effective field theory.

• Publisher: Nature Publishing Group
• Subject: Electromagnetic fields / Electromagnetism / Experiments / Field theory / Gluons / Momentum transfer / Nucleons / Precession / Quarks / Spin structure / Strong interactions (field theory)