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Title: A dispersive treatment of Kl4 decays

Kl4 decays offer several reasons of interest: they allow an accurate measurement of ππ-scattering lengths; they provide the best source for the determination of some low-energy constants of xPT; one form factor is directly related to the chiral anomaly, which can be measured here. We present a dispersive treatment of Kl4 decays that provides a resummation of ππ- and Kπ-rescattering effects. In addition, the free parameters of the dispersion relation are fitted to the data of the high-statistics experiments E865 and NA48/2. The matching toxPT at NLO and NNLO enables us to determine the LECs Lr1, Lr2 and Lr3. With recently published data from NA48/2, the LEC Lr9 can be determined as well. In contrast to a pure chiral treatment, the dispersion relation describes the observed curvature of one of the form factors, which we understand as a rescattering effect beyond NNLO.
 [1] ;  [2] ;  [3]
  1. Univ. of Bern, Bern (Switzerland)
  2. Indiana Univ., Bloomington, IN (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  3. Univ. of Bern, Bern (Switzerland); Univ. of Bonn, Bonn (Germany)
Publication Date:
OSTI Identifier:
Report Number(s):
JLAB--THY-15-1998; DOE/OR/23177--3265; arXiv:1501.05627
Journal ID: ISSN 1434-6044; PII: 3357
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: European Physical Journal. C, Particles and Fields; Journal Volume: 75; Journal Issue: 4
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States