Pole structures of the X(1840) or X(1835) and the

Abstract

Whether the NN¯ interaction could form a state or not is a long standing question, even before the observation of the pp¯ threshold enhancement in 2003. The recent high statistic measurement in the J/ψ→γ3(π+π−) channel would provide a good opportunity to probe the nature of the peak structures around the pp¯ threshold in various processes. By constructing the NN¯ interaction respecting chiral symmetry, we extract the pole positions by fitting the pp¯ and 3(π+π−) invariant mass distributions of the J/ψ→γpp¯ and J/ψ→γ3(π+π−) processes. The threshold enhancement in the pp¯ invariant mass distribution is from the pole on the third Riemann sheet, which more couples to the isospin triplet channel. The broader structure in the 3(π+π−) invariant mass comes from the pole on the physical Riemann sheet, which more couples to the isospin singlet channel. Furthermore, the large compositeness indicates that there should exist pp¯ resonance based on the current experimental data. In addition, we also see a clear threshold enhancement in the nn¯ channel, but not as significant as that in pp¯ channel, which is useful and compared with further experimental measurement. Published by the American Physical Society 2024