4,236 research outputs found
K0 form factor at order p^6 of chiral perturbation theory
This paper describes the calculation of the electromagnetic form factor of
the K0 meson at order p^6 of chiral perturbation theory which is the
next-to-leading order correction to the well-known p^4 result achieved by
Gasser and Leutwyler. On the one hand, at order p^6 the chiral expansion
contains 1- and 2-loop diagrams which are discussed in detail. Especially, a
numerical procedure for calculating the irreducible 2-loop graphs of the sunset
topology is presented. On the other hand, the chiral Lagrangian L^6 produces a
direct coupling of the K0 current with the electromagnetic field tensor. Due to
this coupling one of the unknown parameters of L^6 occurs in the contribution
to the K0 charge radius.Comment: 22 pages Latex with 8 figures, Typos corrected, one reference adde
Renormalization of the antisymmetric tensor field propagator and dynamical generation of the mesons in Resonance Chiral Theory
We discuss the renormalization of the vector meson propagator within
Resonance chiral theory at one loop. Using the particular form of the
interaction Lagrangian we show that additional poles of the renormalized
propagator corresponding to degrees of freedom can be generated. We
give a concrete example of such an effect.Comment: 4 pages, 1 figure, to appear in Proceedings of the conference QCD 08,
Montpellier, 7-12 July 200
Note on Strange Quarks in the Nucleon
Scalar matrix elements involving strange quarks are studied in several
models. Apart from a critical reexamination of results obtained in the Nambu
and Jona-Lasinio model we study a scenario, motivated by instanton physics,
where spontaneous chiral symmetry breaking is induced by the flavor-mixing 't
Hooft interaction only. We also investigate possible contributions of virtual
kaon loops to the strangeness content of the nucleon.Comment: 12 pages, latex style. One figure, available from the author upon
request. University of Regensburg TPR-94-0
Pion mass dependence of the semileptonic scalar form factor within finite volume
We calculate the scalar semileptonic kaon decay in finite volume at the
momentum transfer , using chiral perturbation
theory. At first we obtain the hadronic matrix element to be calculated in
finite volume. We then evaluate the finite size effects for two volumes with and and find that the difference between the finite
volume corrections of the two volumes are larger than the difference as quoted
in \cite{Boyle2007a}. It appears then that the pion masses used for the scalar
form factor in ChPT are large which result in large finite volume corrections.
If appropriate values for pion mass are used, we believe that the finite size
effects estimated in this paper can be useful for Lattice data to extrapolate
at large lattice size.Comment: 19 pages, 5 figures, accepted for publication in EPJ
QCD Accurately Predicts the Induced Pseudoscalar Coupling Constant
Using chiral Ward identities of QCD, we derive a relation for the induced
pseudoscalar coupling constant which is accurate within a few percent, .Comment: 5pp, LaTeX, CRN-94/1
Strangeness in the Scalar Form Factor of the Nucleon
The scalar form factor of the nucleon and related physical quantities are
investigated in the framework of the semibosonized SU(3) Nambu-Jona-Lasinio
soliton model. We take into account the rotational corrections and
linear corrections. The strangeness content of the nucleon in the scalar
form factor is discussed in detail. In particular, it is found that the
corrections play an essential role of reducing the arising from the leading order and rotational contributions.
We obtain the \sigma_{\pi N} (0)=40.80\;\mbox{MeV}, \Delta \sigma =
\sigma_{\pi N} (2m^{2}_{\pi})-\sigma_{\pi N} (0) = 18.18\;\mbox{MeV} and
\langle r^2\rangle^{S}_{N} = 1.50\;\mbox{fm}^2.
The results are in a remarkable agreement with empirical data analyzed by
Gasser, Leutwyler, and Sainio~\cite{gls}.Comment: 13 pages, RevTex is used. 3 figures as uufiles are include
Comment on evidence for new interference phenomena in the decay D+ -> K- pi+ mu+ nu
The experimental determination of low energy pi K scattering phase shifts
would assist in determining scattering lengths as well as low energy constants
of chiral perturbation theory for which sum rules have been constructed. The
FOCUS collaboration has presented evidence for interference pheomena from their
analysis of D_l4 decays based on decay amplitudes suitable for a cascade decay
D -> K* -> K pi. We point out that if the well-known full five body kinematics
are taken into account, pi K scattering phases may be extracted. We also point
out that other distributions considered in the context of K_l4 decays can be
applied to charm meson decays to provide constraints on violation of |Delta
I|=1/2 rule and T-violation.Comment: 9 pages, plain latex; version with minor changes compared to v1 on
lepton masses effects, sign error eliminated, clarifying remarks added, one
additional ref.; version to appear in Phys. Lett.
Chiral Corrections to Lattice Calculations of Charge Radii
Logarithmic divergences in pion and proton charge radii associated with
chiral loops are investigated to assess systematic uncertainties in current
lattice determinations of charge radii. The chiral corrections offer a possible
solution to the long standing problem of why present lattice calculations yield
proton and pion radii which are similar in size.Comment: PostScript file only. Ten pages. Figures included. U. of MD Preprint
#92-19
The Decuplet Revisited in PT
The paper deals with two issues. First, we explore the quantitiative
importance of higher multiplets for properties of the decuplet in
chiral perturbation theory. In particular, it is found that the lowest order
one--loop contributions from the Roper octet to the decuplet masses and
magnetic moments are substantial. The relevance of these results to the chiral
expansion in general is discussed. The exact values of the magnetic moments
depend upon delicate cancellations involving ill--determined coupling
constants. Second, we present new relations between the magnetic moments of the
decuplet that are independent of all couplings. They are exact at the
order of the chiral expansion used in this paper.Comment: 7 pages of double column revtex, no figure
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