Isospin breaking in KπK\piKπ vector form-factors for the weak and rare decays Kℓ3K_{\ell3}Kℓ3, K→πννˉK\to\pi\nu\bar\nuK→πννˉ and K→πℓ+ℓ−K\to\pi\ell^+\ell^-K→πℓ+ℓ− (original) (raw)
Related papers
2007
We calculate the two form-factors for the four Kaon to pion transitions via a vector current to order p 6 in Chiral Perturbation Theory to first order in isospin breaking via the quark masses. In addition we derive relations between these formfactors valid to first order in the up-down quark-mass difference but to all orders in Chiral Perturbation Theory. We present numerical results for all eight form-factors at t = 0 and for varying t and for the scalar form-factors at the Callan-Treiman point.
Near-threshold isospin violation in the pion form factor from chiral perturbation theory
We examine the isospin violation in the timelike pion form factor near threshold at next-to-leading order in the chiral expansion using the techniques of Chiral Perturbation Theory. This next-to-leading order contribution contains the first nonvanishing isospin violation. This isospin violation is found to be very small near threshold. In particular, the isospin violation at threshold is found to be of order 10 −4 , which should be compared with the few percent level seen in the vector meson resonance region.
Isospin breaking corrections to nucleon form factors in the constituent quark model
Phys Rev C, 1995
We examine isospin breaking in the nucleon wave functions due to the u−du - du−d quark mass difference and the Coulomb interaction among the quarks, and their consequences on the nucleon electroweak form factors in a nonrelativistic constituent quark model. The mechanically induced isospin breaking in the nucleon wave functions and electroweak form factors are exactly evaluated in this model. We calculate the electromagnetically induced isospin admixtures by using first-order perturbation theory, including the lowest-lying resonance with nucleon quantum numbers but isospin 3/2. We find a small ($\leq 1\%$), but finite correction to the anomalous magnetic moments of the nucleon stemming almost entirely from the quark mass difference, while the static nucleon axial coupling remains uncorrected. Corrections of the same order of magnitude appear in charge, magnetic, and axial radii of the nucleon. The correction to the charge radius in this model is primarily isoscalar, and may be of some significance for the extraction of the strangeness radius from e.g. elastic forward angle parity violating electron-proton asymmetries, or elastic 4He(vece,e′){}^4He({\vec e},e')4He(vece,e′) experiments.
Isospin breaking in KrightarrowpipiK \rightarrow \pi\piKrightarrowpipi decays
The European Physical Journal C - Particles and Fields, 2004
We perform a complete analysis of isospin breaking in K → 2π amplitudes in chiral perturbation theory, including both strong isospin violation (m u = m d ) and electromagnetic corrections to next-to-leading order in the low-energy expansion. The unknown chiral couplings are estimated at leading order in the 1/N c expansion. We study the impact of isospin breaking on CP conserving amplitudes and rescattering phases. In particular, we extract the effective couplings g 8 and g 27 from a fit to K → ππ branching ratios, finding small deviations from the isospin-limit case. The ratio ReA 0 /ReA 2 measuring the ∆I = 1/2 enhancement is found to decrease from 22.2±0.1 in the isospin limit to 20.3±0.5 in the presence of isospin breaking. We also analyse the effect of isospin violation on the CP violation parameter ǫ ′ , finding a destructive interference between three different sources of isospin violation. Within the uncertainties of large-N c estimates for the low-energy constants, the isospin violating correction for ǫ ′ is below 15 %.
Meson Decays with Isospin Breaking at Two Loops
In all calculations done in this thesis, the evaluation of higher order quantum corrections has been central. In the first paper included in this thesis we have investigated the effects of finite volume meson propagators for quark-antiquark vacuum expectation value at two-loop level. In the second paper we have improved the earlier calculations for the eta decay to three pions by implementing two-loop quantum corrections. The low energy constants of order p 6 are estimated by means of a resonance chiral Lagrangian. In addition, the experimental charged decay rate leads to the determination for the isospin breaking quantities. Finally, we have studied the isospin breaking effects on the vector and scalar form-factors of semi-leptonic kaon decays, both rare and weak semi-leptonic decays. Semi-leptonic kaon decays provide a rich laboratory to find the CKM matrix element Vus and the rare decays provide a good environment to search for the possible new physics beyond the Standard Model in the flavor sector.
Isospin-breaking corrections to nucleon electroweak form factors in the constituent quark model
Physical Review C, 1995
We examine isospin breaking in the nucleon wave functions due to the u−d quark mass difference and the Coulomb interaction among the quarks, and their consequences on the nucleon electroweak form factors in a nonrelativistic constituent quark model. The mechanically induced isospin breaking in the nucleon wave functions and electroweak form factors are exactly evaluated in this model. We calculate the electromagnetically induced isospin admixtures by using first-order perturbation theory, including the lowest-lying resonance with nucleon quantum numbers but isospin 3/2. We find a small (≤ 1%), but finite correction to the anomalous magnetic moments of the nucleon stemming almost entirely from the quark mass difference, while the static nucleon axial coupling remains uncorrected. Corrections of the same order of magnitude appear in charge, magnetic, and axial radii of the nucleon. The correction to the charge radius in this model is primarily isoscalar, and may be of some significance for the extraction of the strangeness radius from e.g. elastic forward angle parity violating electron-proton asymmetries, or elastic 4 He( e, e ′ ) experiments.
Meson Decay with Isospin Breaking At Two Loops
2007
In all calculations done in this thesis, the evaluation of higher order quantum corrections has been central. In the first paper included in this thesis we have investigated the effects of finite volume meson propagators for quark-antiquark vacuum expectation value at two-loop level. In the second paper we have improved the earlier calculations for the eta decay to three pions by implementing two-loop quantum corrections. The low energy constants of order p6 are estimated by means of a resonance chiral Lagrangian. In addition, the experimental charged decay rate leads to the determination for the isospin breaking quantities. Finally, we have studied the isospin breaking effects on the vector and scalar form-factor of semi-leptonic decays. Semi-leptonic kaon decays, both rare and weak semi-leptonic decays. Semi-leptonic kaon decays provide a rich laboratory to find the CKM matrix element Vus and the possible new physics beyond the Standard Model in flavor sector. (Less)
Isospin-breaking quark condensates in chiral perturbation theory
We analyze the isospin-breaking corrections to quark condensates within oneloop SU(2) and SU(3) chiral perturbation theory including m u � = m d as well as electromagnetic (EM) contributions. The explicit expressions are given and several phenomenological aspects are studied. We analyze the sensitivity of recent condensate determinations to the EM low-energy constants (LEC). If the explicit chiral symmetry breaking induced by EM terms generates a ferromagnetic-like response of the vacuum, as in the case of quark masses, the increasing of the order parameter implies constraints for the EM LEC, which we check with different estimates in the literature. In addition, we extend the sum rule relating quark condensate ratios in SU(3) to include EM corrections, which are of the same order as the m u � = m d ones, and we use that sum rule to estimate the vacuum asymmetry within ChPT. We also discuss the matching conditions between the SU(2) and SU(3) LEC involved in the condensates, when both isospin-breaking sources are taken into account.
AIP Conference Proceedings, 2007
Light constituent quark masses and the corresponding dynamical quark masses are determined by data, the quark-level linear σ model, and infrared QCD. This allows to define effective nonstrange and strange current quark masses, which reproduce the experimental pion and kaon masses very accurately, by simple additivity. In contrast, the usual nonstrange and strange current quarks employed by the Particle Data Group and Chiral Perturbation Theory do not allow a straightforward quantitative explanation of the pion and kaon masses.