Baryon $$\sigma$$ terms in SU(3) BChPT x 1/N_c

Conference · Fri Feb 28 00:00:00 EST 2020 · PoS - Proceedings of Science

DOI:https://doi.org/10.22323/1.317.0061· OSTI ID:1608408

Fernando, Ishara P.; Goity, Jose Luis

ChPT and the 1/N_c expansion provide systematic frameworks for the strong interactions at low energy. A combined framework of both expansions has been developed and applied for baryons with three light-quark-flavors. The small scale expansion of the combined approach is identified as the ξ-expansion, in which the power counting of the expansions is linked according to O(p) = O(1/N_c) = O(ξ). The physical baryon masses as well as lattice QCD baryon masses for different quark mass masses are analyzed to O(ξ³) in that framework. σ terms are addressed using the Feynman Hellmann theorem. For the nucleon, a useful connection between the deviation of the Gell-Mann-Okubo relation and the σ term σ_8N associated with the scalar density $$\bar{u}u+\bar{d}d-2\bar{s}s$$ is identified. In particular, the deviation from the tree level relation σ_8N = $$\frac{1}{3}$$(2m_N-m_Σ-m_Ξ), which gives rise to the so called σ-term puzzle, is studied in the ξ-expansion. A large correction non-analytic in ξ results for that relation, making plausible the resolution of the puzzle. Issues with the determination of the strangeness σ terms are discussed, emphasizing the need for lattice calculations at smaller m_s for better understanding the range of validity of the effective theory. The analysis presented here leads to σ_πN = 69(10) MeV and σ_πΔ = 60(10) MeV.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1608408
• Report Number(s): JLAB-THY-19-2915; DOE/OR/23177-4668; arXiv:1904.07112
• Journal Information: PoS - Proceedings of Science, Vol. CD18; Conference: 9th International Workshop on Chiral Dynamics (CD18), 17-21 September 2018, Durham, NC, United States; ISSN 1824-8039
• Publisher: SISSA
• Country of Publication: United States
• Language: English