[Paper Review] Observation of charged $\kappa$ in $J/\psi -> K^*(892)^{-+}K_s\ pi^{+-}$, $K^*(892)^{-+} -> K_s\pi^{-+}$ at BESII

F. De Mori, H. X. Yang+144 more|arXiv (Cornell University)|Aug 26, 2010

Quantum Chromodynamics and Particle Interactions27 references21 citations

TL;DR

This study reports the first observation of a charged κ resonance in J/ψ → K*(892)∓ K_S π± decays using 58 million J/ψ events from BESII. The charged κ is measured with a mass of (826±49−34+49) MeV/c² and width of (449±156−81+144) MeV/c², consistent with the neutral κ, confirming its existence and properties in the charged channel.

ABSTRACT

Using 58 million J/ψ decays obtained by BESII, a charged κ particle is observed in the analysis of the KSπ± system recoiling against K⁎(892)∓ selected in J/ψ→KSKSπ+π− . The mass and width values of the charged κ are obtained to be (826±49−34+49) MeV/c2 and (449±156−81+144) MeV/c2 for the Breit–Wigner parameters, and the pole position is determined to be (764±63−54+71)−i(306±149−85+143) MeV/c2 . They are in good agreement with those of the neutral κ observed by the BES Collaboration.

Motivation & Objective

• To search for charged κ resonance in J/ψ → K*(892)∓ K_S π± decays using high-statistics BESII data.
• To measure the mass and width of the charged κ resonance via amplitude analysis of the KSπ± system.
• To compare the properties of the charged κ with those of the previously observed neutral κ.
• To test the consistency of resonance parameters across charged and neutral channels in charmonium decays.

Proposed method

• Analyzed 58 million J/ψ events collected by the BESII detector.
• Selected K*(892)∓ via invariant mass reconstruction in the J/ψ → K_S K_S π+ π− decay channel.
• Reconstructed the KSπ± system as the recoil system to search for resonant structures.
• Performed amplitude analysis to extract the Breit–Wigner parameters of the charged κ resonance.
• Determined the pole position using a dynamical model fit to the invariant mass distribution.
• Applied systematic error estimation with correlated uncertainties in mass and width.

Experimental results

Research questions

• RQ1 Does a charged κ resonance appear in the KSπ± invariant mass spectrum recoiling against K*(892)∓ in J/ψ decays?
• RQ2 What are the mass and width of the charged κ resonance, and how do they compare to the neutral κ?
• RQ3 Is the pole position of the charged κ consistent with the neutral κ observed previously by BES?
• RQ4 Do the resonance parameters of the charged κ support its interpretation as a scalar resonance in the S-wave Kπ system?

Key findings

• The charged κ resonance is observed in the KSπ± system recoiling against K*(892)∓ in J/ψ → K_S K_S π+ π− decays.
• The Breit–Wigner mass of the charged κ is measured as (826±49−34+49) MeV/c².
• The Breit–Wigner width is determined to be (449±156−81+144) MeV/c².
• The pole position of the charged κ is found to be (764±63−54+71)−i(306±149−85+143) MeV/c².
• The measured mass and width of the charged κ are in good agreement with those of the neutral κ previously observed by BES.
• The consistency of the resonance parameters supports the existence of the charged κ as a scalar resonance in the Kπ system.