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Karol Kampf

Publications and source records attributed to Karol Kampf.

At least 55 records · Page 3Linked to original sources
arXiv2012

Leading logarithms in the anomalous sector of two-flavour QCD

We add the Wess-Zumino-Witten term to the N=3 massive nonlinear sigma model and study the leading logarithms in the anomalous sector. We obtain the leading logarithms to six loops for π^0 --> γ^*γ^* and to five loops for γ^*πππ. In addition we extend the earlier work on the mass and decay constant to six loops and the vector form factor to five loops. We present numerical result for the anomalous processes and the vector form factor. In all cases the series are found to converge rapidly.

hep-ph↗
arXiv2011

Analytical dispersive construction of $η\to3π$ amplitude: First order in isospin breaking

Because of their small electromagnetic corrections, the isospin-breaking decays $η\to3π$ seem to be good candidates for extracting isospin-breaking parameters $ (m_d-m_u)$. This task is unfortunately complicated by large chiral corrections and the discrepancy between the experimentally measured values of the Dalitz parameters describing the energy dependence of the amplitudes of these decays and those predicted from chiral perturbation theory. We present two methods based on an analytic dispersive representation that use the information from the NNLO chiral result and the one from the measurement of the charged $η\to3π$ decay by KLOE together in a harmonized way in order to determine the value of the quark mass ratio $R$. Our final result is $R=37.7\pm 2.2$. This value supplemented by values of $m_s/\hat{m}$ or even $\hat{m}$ and $m_s$ from other methods (as sum-rules or lattice) enables us to obtain further quark mass characteristics. For instance the recent lattice value for $m_s/\hat{m}~27.5$ leads to $Q= 23.1\pm0.7$. We also quote the corresponding values of the current masses $m_u$ and $m_d$.

hep-ph↗
arXiv2011

Odd sector of QCD

A systematic study of the odd-intrinsic parity sector of QCD is presented. We briefly describe different applications including pi0 -> gamma gamma decay, muonic (g-2) factor and a test of the new holographic conjectures.

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arXiv2011

On decays of light unflavoured pseudoscalar mesons

The ongoing and planned experimental activities with direct reference to light unflavoured pseudoscalar mesons motivate a new theoretical study regarding their properties. An overview including details on new precise calculations is presented.

hep-ph↗
arXiv2011

Resonance saturation in the odd-intrinsic parity sector of low-energy QCD

Using the large N_C approximation we have constructed the most general chiral resonance Lagrangian in the odd-intrinsic parity sector that can generate low energy chiral constants up to O(p^6). Integrating out the resonance fields these O(p^6) constants are expressed in terms of resonance couplings and masses. The role of eta' is discussed and its contribution is explicitly factorized. Using the resonance basis we have also calculated two QCD Green functions of currents: and and found, imposing high energy constraints, additional relations for resonance couplings. We have studied several phenomenological implications based on these correlators from which let us mention here our prediction for the pi0-pole contribution to the muon g-2 factor: $a_μ^{π^0} = 65.8(1.2)\times 10^{-11}$.

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arXiv2010

Renormalization and additional degrees of freedom within the chiral effective theory for spin-1 resonances

We study in detail various aspects of the renormalization of the spin-1 resonance propagator in the effective field theory framework. First, we briefly review the formalisms for the description of spin-1 resonances in the path integral formulation with the stress on the issue of propagating degrees of freedom. Then we calculate the one-loop 1-- meson self-energy within the Resonance chiral theory in the chiral limit using different methods for the description of spin-one particles, namely the Proca field, antisymmetric tensor field and the first order formalisms. We discuss in detail technical aspects of the renormalization procedure which are inherent to the power-counting non-renormalizable theory and give a formal prescription for the organization of both the counterterms and one-particle irreducible graphs. We also construct the corresponding propagators and investigate their properties. We show that the additional poles corresponding to the additional one-particle states are generated by loop corrections, some of which are negative norm ghosts or tachyons. We count the number of such additional poles and briefly discuss their physical meaning.

hep-ph↗
arXiv2009

Note on renormalization of the spin-1 resonance propagator at one loop order

We study various aspects of the renormalization of the Resonance Chiral Theory at the one-loop level using a spin-one resonance propagator as a concrete example. We calculate explicitly the one-loop self-energy within the antisymmetric tensor field formalism, briefly discuss the general structure of the corresponding propagator obtained by means of the Dyson re-summation and give a classification of the propagating degrees of freedom. We find that additional pathological poles (negative norm ghosts or tachyons) are unavoidably generated and various scenarios according to their position are possible. We also briefly comment on the eventual dynamical generation of the opposite parity resonances which are frozen at the tree level and discuss the role of appropriate symmetry which could prevent such a scenario.

hep-ph↗
arXiv2009

Chiral expansion for pi^0 decays

New ongoing experimental activities that have direct reference to pi^0 decay modes call for a new theoretical study in this area. We will summarize some details and interesting facts that concern main decay modes of this lightest meson.

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arXiv2009

Chiral expansions of the pi0 lifetime

The corrections induced by light quark masses to the current algebra result for the $π^0$ lifetime are reexamined. We consider NNLO corrections and we compute all the one-loop and the two-loop diagrams which contribute to the decay amplitude at NNLO in the two-flavour chiral expansion. We show that the result is renormalizable, as Weinberg consistency conditions are satisfied. We find that chiral logarithms are present at this order unlike the case at NLO. The result could be used in conjunction with lattice QCD simulations, the feasibility of which was recently demonstrated. We discuss the matching between the two-flavour and the three-flavour chiral expansions in the anomalous sector at order one-loop and derive the relations between the coupling constants. A modified chiral counting is proposed, in which $m_s$ counts as $O(p)$. We have updated the various inputs needed and used this to make a phenomenological prediction.

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arXiv2008

Dispersive representation of K -> 3 pi amplitudes and cusps

The NA48/2 collaboration has shown clear experimental evidence for a cusp in the data for K -> pi pi^0 pi^0. This effect can be used to extract information on the pi-pi scattering lengths. We address this issue using a two-loop dispersive construction of pi pi -> pi pi and K -> pi pi pi amplitudes in the presence of isospin breaking.

hep-ph↗
arXiv2008

Renormalization of tensor self-energy in Resonance Chiral Theory

We study the problems related to the renormalization of propagators in Resonance Chiral Theory, concentrating on the case of vector $1^{--}$ resonances in the antisymmetric tensor formalism. We have found that renormalization of the divergences of the self-energy graphs needs new type of kinetic counterterms with two derivatives which are not present in the original leading order Lagrangian. The general form of the propagator for antisymmetric tensor fields could then contain not only poles corresponding to the original $1^{--}$ resonance states but also to the additional states with opposite parity which decouple in the free field limit. In some cases, these dynamically generated additional states might be negative norm ghosts or tachyons.

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arXiv2007

First order formalism for spin one fields

We study two general approaches how to describe spin one particles, using vector and antisymmetric tensor fields within RChT. In this paper we focus on the question of an equivalence of both ways. The appearing problems lead us to the introduction of a new type of the description - the first order formalism which naturally connects both traditional formalisms. Moreover, it gives a more general result on the level of the effective chiral Lagrangian that contain all terms from effective chiral Lagrangians in vector and antisymmetric tensor formulations.

hep-ph↗
arXiv2006

On different lagrangian formalisms for vector resonances within chiral perturbation theory

We study the relation of vector Proca field formalism and antisymmetric tensor field formalism for spin-one resonances in the context of the large N_C inspired chiral resonance Lagrangian systematically up to the order O(p6) and give a transparent prescription for the transition from vector to antisymmetric tensor Lagrangian and vice versa. We also discuss the possibility to describe the spin-one resonances using an alternative "mixed" first order formalism, which includes both types of fields simultaneously, and compare this one with the former two. We also briefly comment on the compatibility of the above lagrangian formalisms with the high-energy constraints for concrete VVP correlator.

hep-ph↗
arXiv2006

Tests of the naturalness of the coupling constants in ChPT at order p^6

We derive constraints on combinations of O(p^6) chiral coupling constants by matching a recent two-loop calculation of the pi-K scattering amplitude with a set of sum rules. We examine the validity of the natural expectation that the values of the chiral couplings can be associated with physics properties of the light resonance sector. We focus, in particular, on flavour symmetry breaking of vector resonances. A resonance chiral Lagrangian is constructed which incorporates flavour symmetry breaking more completely than was done before. We use pi-K unsubtracted sum rules as tests of the modelling of the resonance contributions to the chiral couplings. In some cases the O(p^6) couplings are found not to be dominated by the resonance contributions.

hep-ph↗
arXiv2005

The Dalitz decay pi0 -> e+ e- gamma revisited

The amplitude of the Dalitz decay pi0 -> e+ e gamma is studied and its model-independent properties are discussed in detail. A calculation of radiative corrections is performed within the framework of two-flavour chiral perturbation theory, enlarged by virtual photons and leptons. The lowest meson dominance approximation, motivated by large N\_C considerations, is used for the description of the pi0 - gamma* - gamma* transition form factor and for the estimate of the NLO low energy constants involved in the analysis. The two photon reducible contributions is included and discussed. Previous calculations are extended to the whole kinematical range of the soft-photon approximation, thus allowing for the possibility to consider various experimental situations and observables.

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