Measurement of the generalized spin polarizabilities of the neutron in the low $Q^2$ region

Abstract

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. 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 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.

arXiv commentV1: initial version submitted to Nature Physics. V2: Published version. 16 pages, 7 figures. Additional material: 4 data tables (18 pages) V3: Typo corrected in author list. Paper content unchanged

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Cited by in corpus (6)

• The Present and Future of QCD
• Measurement of the Bjorken Sum at very low $Q^2$
• Measured proton electromagnetic structure deviates from theoretical predictions
• Single-pion contribution to the Gerasimov--Drell--Hearn sum rule and related integrals
• Measurement of the nucleon spin structure functions for 0.01<$Q^2$<1 GeV${}^2$ using CLAS
• Signatures of the $\Delta$ isobar in spin observables of ${}^3\mathrm{He}$ electrodisintegration