Formation ofη′(958)-Mesic Nuclei and AxialUA(1)Anomaly at Fin

Abstract

We discuss the possibility to produce the bound states of the η ′ (958) meson in nuclei theoretically. We calculate the formation cross sections of the η ′ bound states with the Green function method for (γ,p) reaction and discuss the experimental feasibility at photon facilities like SPring-8. We conclude that we can expect to observe resonance peaks in (γ,p) spectra for the formation of η ′ bound states and we can deduce new information on η ′ properties at finite density. These observations are believed to be essential to know the possible mass shift of η ′ and deduce new information of the effective restoration of the chiral UA(1) anomaly in the nuclear medium.

Experimental results on theω- andη′-nucleus potential - on the way to mesic states

“…the width of possible η mesic states is expected to be much smaller than the depth of the potential. Motivated by the present experimental results and earlier theoretical predictions [30][31][32], three experiments have been launched to search for η bound states using hadron and photon beams. At the Fragment Separator FRS at GSI the 12 C(p, d) reaction has been studied in a search for η mesic states by missing mass spectrometry with a resolution of 1.6 MeV/c 2 [33].…”

Excitation Spectra of Carbon Nuclei near \(\eta '\) Emission Threshold

“…Comprehensive understanding of the origin of the widely distributed masses will contribute to understanding of the QCD [2]. Among the mesons in the lowest-mass pseudo-scalar nonet, the η ′ has much larger mass than the others and its origin has been stimulating many theoretical and experimental studies [3][4][5][6][7][8][9][10][11]. Theoretically, axial U(1) anomaly constitutes an important part of the mechanism of the large mass in combination with spontaneous breakdown of chiral symmetry [10,12,13].…”

Search for η′ Mesic Nuclei in GSI/FAIR

“…An overall explanation of the origin will certainly lead to an 1 understanding of the non-perturbative aspects of low-energy region of the Quantum ChromoDynamics (QCD) [2]. In this context, the η ′ meson has an extremely large mass and its origin stimulates theoretical and experimental studies [3][4][5][6][7][8][9][10][11]. Theoretically the large mass is interpreted in terms of the interplay between the chiral symmetry breaking and the axial U(1) anomaly [8,12,13].…”