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Measurements of e+e- -> K+K-eta, K+K-pi0 and KsK+pi- Cross Sections Using Initial State Radiation Events

BaBar Collaboration, B. Aubert

TL;DR

This study leverages ISR in BaBar data to map e+e- hadronic cross sections for KKπ, KKπ0, φη, and φπ0 up to ~4.6 GeV with unprecedented precision. By performing Dalitz analyses and global fits that couple isoscalar and isovector KK*(892) channels with φη and φπ0, the work disentangles resonance contributions from non-resonant backgrounds, identifying a dominant φ′-like structure in the isoscalar sector and a broad ρ′-like state in the isovector sector. Clean J/ψ signals enable measurements of J/ψ decays to KKπ and KKη, and dedicated searches show no evidence for Y(4260) transitions to KS Kπ or KKπ0, though a 4.2 GeV excess hints at possible new dynamics. The results provide a comprehensive resonance map and improved inputs for vector-meson spectroscopy and dispersive analyses of hadronic cross sections in the 1–4 GeV region.

Abstract

This paper reports measurements of processes: e+e- -> gamma KsK+pi-, e+e- -> gamma K+K-pi0, e+e- -> gamma phi eta, and e+e- -> gamma phi pi0. The initial state radiated photon allows to cover the hadronic final state in the energy range from thresholds up to ~4.6 GeV. The overall size of the data sample analyzed is 232 fb-1, collected by the BaBar detector running at the PEP-II e+e- storage ring. From the Dalitz plot analysis of the KsK+pi- final state, moduli and relative phase of the isoscalar and the isovector components of the e+e- -> K K*(892) cross section are determined. Parameters of phi and rho recurrences are also measured, using a global fitting procedure which exploits the interconnection among amplitudes, moduli and phases of the e+e- -> KsK+pi-, K+K-pi0, phi eta final states. The cross section for the OZI-forbidden process e+e- -> phi pi0, and the J/psi branching fractions to KK*(892) and K+K-eta are also measured.

Measurements of e+e- -> K+K-eta, K+K-pi0 and KsK+pi- Cross Sections Using Initial State Radiation Events

TL;DR

This study leverages ISR in BaBar data to map e+e- hadronic cross sections for KKπ, KKπ0, φη, and φπ0 up to ~4.6 GeV with unprecedented precision. By performing Dalitz analyses and global fits that couple isoscalar and isovector KK*(892) channels with φη and φπ0, the work disentangles resonance contributions from non-resonant backgrounds, identifying a dominant φ′-like structure in the isoscalar sector and a broad ρ′-like state in the isovector sector. Clean J/ψ signals enable measurements of J/ψ decays to KKπ and KKη, and dedicated searches show no evidence for Y(4260) transitions to KS Kπ or KKπ0, though a 4.2 GeV excess hints at possible new dynamics. The results provide a comprehensive resonance map and improved inputs for vector-meson spectroscopy and dispersive analyses of hadronic cross sections in the 1–4 GeV region.

Abstract

This paper reports measurements of processes: e+e- -> gamma KsK+pi-, e+e- -> gamma K+K-pi0, e+e- -> gamma phi eta, and e+e- -> gamma phi pi0. The initial state radiated photon allows to cover the hadronic final state in the energy range from thresholds up to ~4.6 GeV. The overall size of the data sample analyzed is 232 fb-1, collected by the BaBar detector running at the PEP-II e+e- storage ring. From the Dalitz plot analysis of the KsK+pi- final state, moduli and relative phase of the isoscalar and the isovector components of the e+e- -> K K*(892) cross section are determined. Parameters of phi and rho recurrences are also measured, using a global fitting procedure which exploits the interconnection among amplitudes, moduli and phases of the e+e- -> KsK+pi-, K+K-pi0, phi eta final states. The cross section for the OZI-forbidden process e+e- -> phi pi0, and the J/psi branching fractions to KK*(892) and K+K-eta are also measured.

Paper Structure

This paper contains 18 sections, 20 equations, 40 figures, 17 tables.

Table of Contents

  1. INTRODUCTION
  2. THE B A B A R DETECTOR AND DATASET
  3. EVENT SELECTION AND KINEMATICS
  4. The $K^0_{ S}\xspace K^\pm\xspace\pi^\mp\xspace$ FINAL STATE
  5. Event selection
  6. Cross section for $e^+e^-\xspace\rightarrow\xspace K^0_{ S}\xspace K^\pm\xspace\pi^\mp\xspace\xspace$
  7. The $K^+\xspace K^-\xspace\pi^0\xspace$ FINAL STATE
  8. The Dalitz Plot analysis for $K^0_{ S}\xspace K^\pm\xspace\pi^\mp\xspace$ and $K^+\xspace K^-\xspace\pi^0\xspace$ channels
  9. The Dalitz method
  10. The ${J / \psi }$ region
  11. The $\phi\pi^0\xspace$ FINAL STATE
  12. The $K^+\xspace K^-\xspace\eta$ FINAL STATE
  13. $e^+e^-\xspace\rightarrow\xspace KK\eta$
  14. $e^+e^-\xspace\rightarrow\xspace\phi\eta$
  15. Cross section Fits
  16. ...and 3 more sections

Figures (40)

  • Figure 1: The $\chi^2$ distributions for data (points), signal MC (open histogram) normalized to the first bin of the data, background contribution due to $q\overline q$ (hatched histogram) and different ISR-produced final states (gray histogram).
  • Figure 2: Reconstructed $K^0_{ S}$ mass for data (points) and signal MC simulation (histogram).
  • Figure 3: (a) invariant mass of the ISR photon and any other photon in the event. Distributions for data (points with error bars), signal MC (open histogram) and $q\overline q$ MC (shaded histogram) samples are shown. (b) $\gamma\gamma$ mass distribution for additional photons in data (points) compared with signal MC simulation.
  • Figure 4: The invariant mass distribution of the $K^0_{ S}\xspace K^\pm\xspace\pi^\mp\xspace$ system (open histogram). The hatched and gray histograms show the $q\overline q$ and ISR backgrounds, respectively.
  • Figure 5: Detection and reconstruction efficiency as a function of the c.m. energy for the $K^0_{ S}\xspace K^\pm\xspace\pi^\mp\xspace$ final state. The solid line is the result of a linear fit to the data.
  • ...and 35 more figures