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

• Published in: Nature physics Vol. 17; no. 6; pp. 687 - 692
• Main Authors: Peng, Chao, Chen, Jian-ping, Abrahamyan, Sergey, Aniol, Konrad A., Armstrong, David S., Averett, Todd, Bailey, Stephanie L., Beck, Arie, Bertin, Pierre, Butaru, Florentin, Boeglin, Werner, Camsonne, Alexandre, Cates, Gordon D., Chang, Chia-Cheh, Choi, Seonho, Chudakov, Eugene, Coman, Luminita, Cornejo, Juan C., Craver, Brandon, Cusanno, Francesco, De Leo, Raffaele, de Jager, Cornelis W., Denton, Joseph D., Feuerbach, Robert, Finn, John M., Frullani, Salvatore, Fuoti, Kirsten, Gao, Haiyan, Garibaldi, Franco, Gayou, Olivier, Glamazdin, Alexander, Glashausser, Charles, Gomez, Javier, Hansen, Jens-Ole, Hayes, David, Hersman, F. William, Holmstrom, Timothy, Humensky, Thomas B., Hyde, Charles E., Ibrahim, Hassan, Iodice, Mauro, Jiang, Xiandong, Kaufman, Lisa J., Kelleher, Aidan, Kim, Wooyoung, Kolarkar, Ameya, Kolb, Norm, Korsch, Wolfgang, Kramer, Kevin, Kumbartzki, Gerfried, Lagamba, Luigi, Lainé, Vivien, Laveissiere, Geraud, Lerose, John J., Lindgren, Richard, Liyanage, Nilanga, Lu, Hai-Jiang, Ma, Bin, Margaziotis, Demetrius J., Markowitz, Peter, McCormick, Kathleen R., Meziane, Mehdi, Meziani, Zein-Eddine, Michaels, Robert, Moffit, Bryan, Monaghan, Peter, Nanda, Sirish, Niedziela, Jennifer, Niskin, Mikhail, Pandolfi, Ronald, Paschke, Kent D., Potokar, Milan, Puckett, Andrew, Punjabi, Vina A., Qiang, Yi, Ransome, Ronald D., Reitz, Bodo, Roché, Rikki, Saha, Arun, Shabetai, Alexander, Širca, Simon, Singh, Jaideep T., Slifer, Karl, Snyder, Ryan, Solvignon, Patricia, Stringer, Robert, Subedi, Ramesh, Tobias, William A., Ton, Ngyen, Ulmer, Paul E., Urciuoli, Guido Maria, Vacheret, Antonin, Voutier, Eric, Wang, Kebin, Wan, Lu, Wojtsekhowski, Bogdan, Woo, Seungtae, Yao, Huan, Yuan, Jing, Zheng, Xiaochao
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 31-05-2021; Nature Publishing Group; Nature Publishing Group (NPG)
• Subjects: 639/766/387/1126; 639/766/387/1129; 639/766/419/1131; 639/766/419/1133; Atomic; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Electromagnetic fields; Electromagnetism; experimental nuclear physics; experimental particle physics; Experiments; Field theory; Gluons; Letter; Mathematical and Computational Physics; Molecular; Momentum transfer; NUCLEAR PHYSICS AND RADIATION PHYSICS; Nucleons; Optical and Plasma Physics; Physics; Physics and Astronomy; Precession; Quarks; Spin structure; Strong interactions (field theory); Theoretical; theoretical nuclear physics; theoretical particle physics
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-021-01245-9

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 theory
1
. 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 GeV
2
. In this regime, chiral effective field theory calculations
2
–
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.