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Yao, D. L. (2018). Masses and sigma terms of doubly charmed baryons up to O(p(4)) in manifestly Lorentz-invariant baryon chiral perturbation theory. Phys. Rev. D, 97(3), 034012–12pp.
Abstract: We calculate the masses and sigma terms of the doubly charmed baryons up to next-to-next-to-next-toleading order [i.e., O(p(4))] in a covariant baryon chiral perturbation theory by using the extended-on-mass-shell renormalization scheme. Their expressions both in infinite and finite volumes are provided for chiral extrapolation in lattice QCD. As a first application, our chiral results of the masses are confronted with the existing lattice QCD data in the presence of finite-volume corrections. Up to O(p(3)), all relevant low-energy constants can be well determined. As a consequence, we obtain the physical values for the masses of Xi(cc) and Omega(cc) baryons by extrapolating to the physical limit. Our determination of the Xi(cc) mass is consistent with the recent experimental value by LHCb Collaboration, however, larger than the one by SELEX Collaboration. In addition, we predict the pion-baryon and strangeness-baryon sigma terms, as well as the mass splitting between the Xi(cc) and Omega(cc) states. Their quark mass dependences are also discussed. The numerical procedure can be applied to the chiral results of O(p(4)) order, where more unknown constants are involved, when more data are available for unphysical pion masses.
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Dai, L. Y., Kang, X. W., Meissner, U. G., Song, X. Y., & Yao, D. L. (2018). Amplitude analysis of the anomalous decay eta ' -> pi(+) pi(-) gamma. Phys. Rev. D, 97(3), 036012–12pp.
Abstract: In this paper we perform an amplitude analysis of eta ' -> pi(+)pi(-)gamma and confront it with the latest BESIII data. Based on the final-state interaction theorem, we represent the amplitude in terms of an Omnes function multiplied by a form factor that corresponds to the contributions from left-hand cuts and right-hand cuts in the inelastic channels. We also take into account the isospin violation effect induced by rho-omega mixing. Our results show that the anomaly contribution is mandatory in order to explain the data. Its contribution to the decay width of Gamma(eta ' -> pi pi gamma) is larger than that induced by isospin violation. Finally we extract the pole positions of the rho and omega as well as their corresponding residues.
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Yao, D. L., Alvarez-Ruso, L., & Vicente Vacas, M. J. (2017). Extraction of nucleon axial charge and radius from lattice QCD results using baryon chiral perturbation theory. Phys. Rev. D, 96(11), 116022–11pp.
Abstract: We calculate the nucleon axial form factor up to the leading one-loop order in a covariant chiral effective field theory with the Delta(1232) resonance as an explicit degree of freedom. We fit the axial form factor to the latest lattice QCD data and pin down the relevant low-energy constants. The lattice QCD data, for various pion masses below 400 MeV, can be well described up to a momentum transfer of similar to 0.6 GeV. The Delta(1232) loops contribute significantly to this agreement. Furthermore, we extract the axial charge and radius based on the fitted values of the low-energy constants. The results are g(A) = 1.237(74) and < r(A)(2)> = 0.263(38) fm(2). The obtained coupling g(A) is consistent with the experimental value if the uncertainty is taken into account. The axial radius is below but in agreement with the recent extraction from neutrino quasielastic scattering data on deuterium, which has large error bars. Up to our current working accuracy, r(A) is predicted only at leading order, i.e., the one-loop level. A more precise determination might need terms of O(p(5)).
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Yao, D. L., Fernandez-Soler, P., Albaladejo, M., Guo, F. K., & Nieves, J. (2018). Heavy-to-light scalar form factors from Muskhelishvili-Omnes dispersion relations. Eur. Phys. J. C, 78(4), 310–26pp.
Abstract: By solving the Muskhelishvili-Omnes integral equations, the scalar form factors of the semileptonic heavy meson decays D -> pi(l) over bar nu(l), D -> (K) over bar(l) over bar nu(l), (K) over bar -> pi(l) over bar nu(l) and (B) over bar (s) -> Kl (nu) over bar (l) are simultaneously studied. As input, we employ unitarized heavy meson-Goldstone boson chiral coupled-channel amplitudes for the energy regions not far from thresholds, while, at high energies, adequate asymptotic conditions are imposed. The scalar form factors are expressed in terms of Omn\`es matrices multiplied by vector polynomials, which contain some undetermined dispersive subtraction constants. We make use of heavy quark and chiral symmetries to constrain these constants, which are fitted to lattice QCD results both in the charm and the bottom sectors, and in this latter sector to the light-cone sum rule predictions close to q(2)=0 as well. We find a good simultaneous description of the scalar form factors for the four semileptonic decay reactions. From this combined fit, and taking advantage that scalar and vector form factors are equal at q(2)=0, we obtain |V-cd| = 0.244 +/- 0.022, |V-cs| = 0.945 +/- 0.041 and |V-ub| = (4.3 +/- 0.7)x10(-3) for the involved Cabibbo-Kobayashi-Maskawa (CKM) matrix elements. In addition, we predict the following vector form factors at q(2) = 0: |f(+)(D ->eta)(0)| = 0.01 +/- 0.05, |f(+)(Ds ->eta)(0)| = 0.50 +/- 0.08, |f(+)(Ds ->eta)(0)| = 0.73 +/- 0.03 and|f(+)((B) over bar ->eta)(0)| = 0.82 +/- 0.08, which might serve as alternatives to determine the CKM elements when experimental measurements of the corresponding differential decay rates become available. Finally, we predict the different form factors above the q(2)-regions accessible in the semileptonic decays, up to moderate energies amenable to be described using the unitarized coupled-channel chiral approach.
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Wang, Y. F., Yao, D. L., & Zheng, H. Q. (2018). New insights on low energy pi N scattering amplitudes. Eur. Phys. J. C, 78(7), 543–18pp.
Abstract: The S- and P- wave phase shifts of low-energy pion-nucleon scatterings are analysed using Peking University representation, in which they are decomposed into various terms contributing either from poles or branch cuts. We estimate the left-hand cut contributions with the help of tree-level perturbative amplitudes derived in relativistic baryon chiral perturbation theory up to O(p(2)). It is found that in S-11 and P-11 channels, contributions from known resonances and cuts are far from enough to saturate experimental phase shift data – strongly indicating contributions from low lying poles undiscovered before, and we fully explore possible physics behind. On the other side, no serious disagreements are observed in the other channels.
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