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

2021; Nature Portfolio; Volume: 17; Issue: 6 Linguagem: Inglês

10.1038/s41567-021-01245-9

1745-2481

V. Sulkosky, C. Peng, J.-P. Chen, A. Deur, Sergey Abrahamyan, K. Aniol, David Armstrong, T. Averett, Stephanie Bailey, Arie Beck, P.Y. Bertin, F. Butaru, W. Boeglin, A. Camsonne, G. D. Cates, C. C. Chang, Seonho Choi, E. Chudakov, L. Coman, J. C. Cornejo, B. Craver, F. Cusanno, Raffaele De Leo, Cornelis W. de Jager, Joseph D. Denton, S. Dhamija, R. J. Feuerbach, John M. Finn, S. Frullani, K. Fuoti, H. Gao, F. Garibaldi, Olivier Gayou, R. Gilman, A. Glamazdin, C. Glashausser, J. Gómez, O. Hansen, David Hayes, F. William Hersman, D. W. Higinbotham, Timothy Holmstrom, T. B. Humensky, C. E. Hyde-Wright, H. Ibrahim, Mauro Iodice, Xiandong Jiang, L. J. Kaufman, A. Kelleher, K. Ellen Keister, Wooyoung Kim, A. Kolarkar, N. R. Kolb, W. Korsch, K. Kramer, G. Kumbartzki, L. Lagamba, V. Lainé, G. Laveissière, J. J. LeRose, D. Lhuillier, R. Lindgren, Nilanga Liyanage, Hai-Jiang Lu, Bin Ma, D. J. Margaziotis, Peter Markowitz, K. McCormick, Mehdi Meziane, Z.-E. Meziani, R. Michaels, B. Moffit, Peter Monaghan, Sirish Nanda, J. L. Niedziela, Mikhail Niskin, Ronald Pandolfi, K. Paschke, M. Potokar, A. J. R. Puckett, Vina Punjabi, Y. Qiang, R. D. Ransome, B. Reitz, R. Roché, A. Saha, Alexander Shabetai, S. Širca, Jaideep Singh, K. Slifer, R. Snyder, Patricia Solvignon, Robert Stringer, Ramesh Subedi, W. A. Tobias, Ngyen Ton, P. Ulmer, Guido Maria Urciuoli, Antonin Vacheret, E. Voutier, Kebin Wang, Lu Wan, B. Wojtsekhowski, Seungtae Woo, Huan Yao, Jing Yuan, Xiaohui Zhan, Xiaochao Zheng, Lingyan Zhu,

Quantum Chromodynamics and Particle Interactions

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.