scholarly journals Low energy analysis of $\pi N$ scattering and the sigma term with Covariant Baryon Chiral Perturbation Theory

2013 ◽  
Author(s):  
Jose Manuel Alarcón
Keyword(s):  
Perturbation Theory ◽  
Chiral Perturbation Theory ◽  
Energy Analysis ◽  
Low Energy ◽  
Chiral Perturbation ◽  
Sigma Term

scholarly journals New method for fitting the low-energy constants in chiral perturbation theory

2020 ◽  
Vol 102 (9) ◽  
Author(s):  
Qin-He Yang ◽  
Wei Guo ◽  
Feng-Jun Ge ◽  
Bo Huang ◽  
Hao Liu ◽  
...  
Keyword(s):  
Perturbation Theory ◽  
Chiral Perturbation Theory ◽  
Low Energy ◽  
New Method ◽  
Chiral Perturbation ◽  
Energy Constants

CHIRAL PERTURBATION THEORY AT THE QUARK LEVEL

1992 ◽  
Vol 07 (29) ◽  
pp. 7305-7338 ◽  
Author(s):  
A.N. IVANOV ◽  
M. NAGY ◽  
N.I. TROITSKAYA
Keyword(s):  
Perturbation Theory ◽  
Chiral Perturbation Theory ◽  
Final State Interaction ◽  
Low Energy ◽  
Chiral Perturbation ◽  
Final State ◽  
Large N ◽  
Quark Level ◽  
Energy Approximation

The chiral perturbation theory is developed at the quark level within the extended Nambu-Jona-Lasinio model, which we used for the low-energy approximation of QCD in the leading order of the large N expansion. In terms of constituent-quark loop diagrams we analyze all of the main low-energy effects caused by the first order corrections in the current-quark-mass expansions. For the correct description of the η→3π decays we confirm the important role of the final-state interaction quoted by Gasser and Leutwyler.

scholarly journals Dissecting the $$\Delta I=1/2$$ rule at large $$N_c$$

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
Andrea Donini ◽  
Pilar Hernández ◽  
Carlos Pena ◽  
Fernando Romero-López
Keyword(s):  
Perturbation Theory ◽  
Chiral Perturbation Theory ◽  
Low Energy ◽  
Kaon Decay ◽  
Chiral Perturbation ◽  
Kaon Decays ◽  
Diagrammatic Analysis ◽  
Good Agreement

Abstract We study the scaling of kaon decay amplitudes with the number of colours, $$N_c$$Nc, in a theory with four degenerate flavours, $$N_f=4$$Nf=4. In this scenario, two current-current operators, $$Q^\pm $$Q±, mediate $$\Delta S=1$$ΔS=1 transitions, such as the two isospin amplitudes of non-leptonic kaon decays for $$K\rightarrow (\pi \pi )_{I=0,2}$$K→(ππ)I=0,2, $$A_0$$A0 and $$A_2$$A2. In particular, we concentrate on the simpler $$K\rightarrow \pi $$K→π amplitudes, $$A^\pm $$A±, mediated by these two operators. A diagrammatic analysis of the large-$$N_c$$Nc scaling of these observables is presented, which demonstrates the anticorrelation of the leading $${{\mathcal {O}}}(1/N_c)$$O(1/Nc) and $${{\mathcal {O}}}(N_f/N_c^2)$$O(Nf/Nc2) corrections in both amplitudes. Using our new $$N_f=4$$Nf=4 and previous quenched data, we confirm this expectation and show that these corrections are naturally large and may be at the origin of the $$\Delta I=1/2$$ΔI=1/2 rule. The evidence for the latter is indirect, based on the matching of the amplitudes to their prediction in Chiral Perturbation Theory, from which the LO low-energy couplings of the chiral weak Hamiltonian, $$g^\pm $$g±, can be determined. A NLO estimate of the $$K \rightarrow (\pi \pi )_{I=0,2}$$K→(ππ)I=0,2 isospin amplitudes can then be derived, which is in good agreement with the experimental value.

scholarly journals First direct lattice calculation of the chiral perturbation theory low-energy constant ℓ7

2021 ◽  
Vol 104 (7) ◽  
Author(s):  
R. Frezzotti ◽  
G. Gagliardi ◽  
V. Lubicz ◽  
G. Martinelli ◽  
F. Sanfilippo ◽  
...  
Keyword(s):  
Perturbation Theory ◽  
Chiral Perturbation Theory ◽  
Low Energy ◽  
Lattice Calculation ◽  
Chiral Perturbation ◽  
Energy Constant ◽  
Direct Lattice
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