Measurement of the α -Particle Monopole Transition Form Factor Challenges Theory: A Low-Energy Puzzle for Nuclear Forces

S. Kegel, P. Achenbach, S. Bacca, N. Barnea, J. Beričič, D. Bosnar, L. Correa, M. O. Distler, A. Esser, H. Fonvieille, I. Friščić, M. Heilig, P. Herrmann, M. Hoek, P. Klag, T. Kolar, W. Leidemann, H. Merkel, M. Mihovilovič, J. MüllerU. Müller, G. Orlandini, J. Pochodzalla, B. S. Schlimme, M. Schoth, F. Schulz, C. Sfienti*, S. Širca, R. Spreckels, Y. Stöttinger, M. Thiel, A. Tyukin, T. Walcher, A. Weber

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

We perform a systematic study of the α-particle excitation from its ground state 0_{1}^{+} to the 0_{2}^{+} resonance. The so-called monopole transition form factor is investigated via an electron scattering experiment in a broad Q^{2} range (from 0.5 to 5.0  fm^{-2}). The precision of the new data dramatically supersedes that of older sets of data, each covering only a portion of the Q^{2} range. The new data allow the determination of two coefficients in a low-momentum expansion, leading to a new puzzle. By confronting experiment to state-of-the-art theoretical calculations, we observe that modern nuclear forces, including those derived within chiral effective field theory that are well tested on a variety of observables, fail to reproduce the excitation of the α particle.

Original languageAmerican English
Article number152502
JournalPhysical Review Letters
Volume130
Issue number15
DOIs
StatePublished - 14 Apr 2023

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© 2023 American Physical Society.

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