|Delta I|=3/2 Decays of Hyperons in Chiral Perturbation Theory (original) (raw)

Chiral perturbation theory for |ΔI| = 3 2 hyperon decays

Nuclear Physics A, 1999

We study the |∆I| = 3/2 amplitudes of hyperon non-leptonic decays of the form B → B ′ π in the context of chiral perturbation theory. The lowest-order predictions are determined in terms of only one unknown parameter and are consistent within errors with current data. We investigate the theoretical uncertainty of these predictions by calculating the leading nonanalytic corrections. We also present an estimate for the size of the S-wave Λ and Ξ decays which vanish at leading order. We find that the corrections to the lowest-order predictions are within the expectations of naive power counting and, therefore, that this picture can be tested more accurately with improved measurements.

Chiral Perturbation Theory for |Delta I|=3/2 Hyperon Decays

1998

Hyperon nonleptonic decays in chiral perturbation theory reexamined

Physical Review D, 2000

We recalculate the leading nonanalytic contributions to the amplitudes for hyperon nonleptonic decays in chiral perturbation theory. Our results partially disagree with those calculated before, and include new terms previously omitted in the P-wave amplitudes. Although these modifications are numerically significant, they do not change the well-known fact that good agreement with experiment cannot be simultaneously achieved using one-loop S-and P-wave amplitudes.

Non-leptonic hyperon decays in chiral perturbation theory

1999

. The non-leptonic hyperon decays are analyzed up to one-loop order including all counterterms in the framework of heavy baryon chiral perturbation theory. We use the exchange of the spin- decuplet resonances as an indication of which low-energy constants contribute significantly to these investigated processes. We choose four independent decay amplitudes that are not related by isospin relations in order to perform a fit for the pertinent low-energy constants and find a satisfactory fit both for s- and p-waves. The chiral corrections to the lowest order forms for the s-waves are moderate whereas there are significant modifications of the p-wave amplitudes.

Semileptonic hyperon decay —a problem for chiral perturbation theory

Physics Letters B, 1985

We study the recently computed m 2 In m 2 corrections to hyperon beta decay found m chiral perturbation theory The inclusion of these effects is not compatible w~th the bagh precision hyperon data, yielding a fit much inferior to the standard assumptaon of SU(3) mvariance Thxs mcompatlbdlty of data and theory is a problem for the appllcat~on of choral perturbation theory

Hyperon weak radiative decays in chiral perturbation theory

Physical Review D, 1996

We investigate the leading-order amplitudes for weak radiative decays of hyperons in chiral perturbation theory. We consistently include contributions from the next-to-leading order weak-interaction Lagrangian. It is shown that due to these terms Hara's theorem is violated. The data for the decays of charged hyperons can be easily accounted for. However, at this order in the chiral expansion, the four amplitudes for the decays of neutral hyperons satisfy relations which are in disagreement with the data. The asymmetry parameters for all the decays can not be accounted for without higher-order terms. We shortly comment on the effect of the 27-plet part of the weak interaction.

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.

Study of the rare hyperon decay

Physics Letters B, 2010

We report a new measurement of the decay Ω − → Ξ − π + π − with 76 events and a first observation of the decay Ω + → Ξ + π + π − with 24 events, yielding a combined branching ratio (3.74 +0.67 −0.56) × 10 −4. This represents a factor 25 increase in statistics over the best previous measurement. No evidence is seen for CP violation, with B(Ω − → Ξ − π + π −) = 4.04 +0.83 −0.71 × 10 −4 and B(Ω + → Ξ + π + π −) = 3.15 +1.12 −0.89 × 10 −4. Contrary to theoretical expectation, we see little evidence for the decays Ω − → Ξ * 0 1530 π − and Ω + → Ξ * 0 1530 π + and place a 90% C.L. upper limit on the combined branching ratio B(Ω − (Ω +) → Ξ * 0 1530 (Ξ * 0 1530)π ∓) < 7.0 × 10 −5 .

The role of resonances in non–leptonic hyperon decays

1999

We examine the importance of resonances for the non–leptonic hyperon decays in the framework of chiral perturbation theory. Lower lying resonances are included into the effective theory. Integrating out the heavy degrees of freedom in the resonance saturation scheme generates higher order counterterms in the effective Lagrangian, providing an estimate of the pertinent coupling constants. A fit to the eight independent decay amplitudes that are not related by isospin symmetry is performed and reasonable agreement for both s– and p– waves is achieved. email: borasoy@het.phast.umass.edu email: holstein@phast.umass.edu

CPviolation in hyperon nonleptonic decays within the standard model

Physical Review D, 2003

We calculate the CP-violating asymmetries A(Λ 0 −) and A(Ξ − −) in nonleptonic hyperon decay within the Standard Model using the framework of heavy-baryon chiral perturbation theory (χPT). We identify those terms that correspond to previous calculations and discover several errors in the existing literature. We present a new result for the lowest-order (in χPT) contribution of the penguin operator to these asymmetries, as well as an estimate for the uncertainty of our result that is based on the calculation of the leading nonanalytic corrections.

|Delta I|=3/2 Decays of Hyperons in Chiral Perturbation Theory (original) (raw)

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