Η → 3Π at Two Loops in Chiral Perturbation Theory (original) (raw)
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eta-->3pi at two loops in Chiral Perturbation Theory
J High Energy Phys, 2007
We calculate the decay η → 3π at next-to-next-to-leading order or order p 6 in Chiral Perturbation Theory. The corrections are somewhat larger than was indicated by dispersive estimates. We present numerical results for the Dalitz plot parameters, the ratio r of the neutral to charged decay and the total decay rate. In addition we derive an inequality between the slope parameters of the charged and neutral decay. The experimental charged decay rate leads to central values for the isospin breaking quantities R = 42.2 and Q = 23.2.
Decay π0→γγ to next to leading order in chiral perturbation theory
Physical Review D, 2002
The pi0-->gammagamma decay width is analyzed within the combined framework of chiral perturbation theory and the 1/Nc expansion up to O(p6) and O(p4×1/Nc) in the decay amplitude. The eta' is explicitly included in the analysis. It is found that the decay width is enhanced by about 4.5% due to the isospin-breaking induced mixing of the pure U(3) states. This effect, which is of leading order in low energy expansion, is shown to persist nearly unchanged at next to leading order. The chief prediction with its estimated uncertainty is Gammapi0-->gammagamma=8.10+/-0.08 eV. This prediction at the 1% level makes the upcoming precision measurement of the decay width even more urgent. Observations on the eta and eta' can also be made, especially about their mixing, which is shown to be significantly affected by next to leading order corrections.
Η→Π^0 Γγ Decay Within Unitarized Chiral Perturbation Theory
2003
We improve the calculations of the η→π^0 γγ decay within the context of meson chiral lagrangians. We use a chiral unitary approach for the meson-meson interaction, thus generating the a_0(980) resonance and fixing the longstanding sign ambiguity on its contribution. This also allows us to calculate the loops with one vector meson exchange, thus removing a former source of uncertainty. In addition we ensure the consistency of the approach with other processes. First, by using vector meson dominance couplings normalized to agree with radiative vector meson decays. And, second, by checking the consistency of the calculations with the related γγ→π^0 η reaction. We find an η→π^0 γγ decay width of 0.47± 0.10 eV, in clear disagreement with published data but in remarkable agreement with the most recent measurement.
Chiral dynamics predictions for η′ → ηππ
Journal of High Energy Physics, 2011
The hadronic decays η ′ → ηππ are studied in the frameworks of large-N C Chiral Perturbation Theory, at lowest and next-to-leading orders, and Resonance Chiral Theory in the leading 1/N C approximation. Higher order effects such as ππ final state interactions are taken into account through a detailed unitarization procedure. The inclusion of finite-width effects in the case of RChT is also discussed. The Dalitz plot distribution and the differential branching ratio are computed in both approaches. The predicted Dalitz plot parameters obtained from the different treatments are compared with the most recent measured values. We find that the η ′ → ηππ branching ratios are easily understood, while the Dalitz plot parameters require the inclusion of ππ loops in order to achieve a reasonable agreement. Our final predictions agree with the experimental measurements. We hope our results to be of relevance for present and future experimental analyses of these decays.
Decay pi(0)-\u3egamma gamma to next to leading order in chiral perturbation theory
2002
The π0→γγ decay width is analyzed within the combined framework of chiral perturbation theory and the 1/Nc expansion up to O(p6) and O(p4×1/Nc) in the decay amplitude. The η′ is explicitly included in the analysis. It is found that the decay width is enhanced by about 4.5% due to the isospin-breaking induced mixing of the pure U(3) states. This effect, which is of leading order in low energy expansion, is shown to persist nearly unchanged at next to leading order. The chief prediction with its estimated uncertainty is Γπ0→γγ=8.10±0.08eV. This prediction at the 1% level makes the upcoming precision measurement of the decay width even more urgent. Observations on the η and η′ can also be made, especially about their mixing, which is shown to be significantly affected by next to leading order corrections
Chiral dynamics predictions for η ′ → ηpipi
2016
The hadronic decays η ′ → ηππ are studied in the frameworks of large-N C Chiral Perturbation Theory, at lowest and next-to-leading orders, and Resonance Chiral Theory in the leading 1/N C approximation. Higher order effects such as ππ final state interactions are taken into account through a detailed unitarization procedure. The inclusion of finite-width effects in the case of RChT is also discussed. The Dalitz plot distribution and the differential branching ratio are computed in both approaches. The predicted Dalitz plot parameters obtained from the different treatments are compared with the most recent measured values. We find that the η ′ → ηππ branching ratios are easily understood, while the Dalitz plot parameters require the inclusion of ππ loops in order to achieve a reasonable agreement. Our final predictions agree with the experimental measurements. We hope our results to be of relevance for present and future experimental analyses of these decays.
Proceedings of 6th International Workshop on Chiral Dynamics — PoS(CD09)
We study the decay η ′ → ηππ in two different chiral invariant approaches: Large-N c Chiral Perturbation Theory (ChPT) and Large-N c Resonance Chiral Theory (RChT). We analyze the Dalitz plot and the invariant mass spectra. We also compare the relevance of the isoscalar and isovector channels in these approaches. While the predictions of Large-N c ChPT at next-to-leading order slightly disagree with the measured decay width (showing the need for final state interactions and higher order local contributions), a reasonable agreement is obtained for the case of RChT. Forthcoming experimental analyses at Bonn, Frascati, Jülich and Mainz will decide among the different frameworks.
Chiral loop corrections and isospin violation effects in ɛ'/ɛ
A complete analysis of isospin breaking in K → 2π amplitudes, including both strong (mu = m d ) and electromagnetic corrections at next-to-leading order in chiral perturbation theory, has been achieved recently [1]. We discuss the implication of these effects [2], together with the previously known chiral loop corrections , on the direct CP-violating ratio ε ′ /ε.
An analytic analysis of the pion decay constant in three-flavoured chiral perturbation theory
The European Physical Journal C, 2017
A representation of the two-loop contribution to the pion decay constant in SU (3) chiral perturbation theory is presented. The result is analytic up to the contribution of the three (different) mass sunset integrals, for which an expansion in their external momentum has been taken. We also give an analytic expression for the two-loop contribution to the pion mass based on a renormalized representation and in terms of the physical eta mass. We find an expansion of F π and M 2 π in the strange-quark mass in the isospin limit, and we perform the matching of the chiral SU (2) and SU (3) lowenergy constants. A numerical analysis demonstrates the high accuracy of our representation, and the strong dependence of the pion decay constant upon the values of the low-energy constants, especially in the chiral limit. Finally, we present a simplified representation that is particularly suitable for fitting with available lattice data.
Η→Π0ΓΓ Decay Within a Chiral Unitary Approach
Physical Review D, 2003
We improve the calculations of the η → π 0 γγ decay within the context of meson chiral lagrangians. We use a chiral unitary approach for the meson-meson interaction, thus generating the a 0 (980) resonance and fixing the longstanding sign ambiguity on its contribution. This also allows us to calculate the loops with one vector meson exchange, thus removing a former source of uncertainty. In addition we ensure the consistency of the approach with other processes. First, by using vector meson dominance couplings normalized to agree with radiative vector meson decays. And, second, by checking the consistency of the calculations with the related γγ → π 0 η reaction. We find an η → π 0 γγ decay width of 0.47 ± 0.10 eV, in clear disagreement with published data but in remarkable agreement with the most recent measurement.