Köln 2004 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 44: Electromagnetic and Hadronic Probes VII

HK 44.3: Talk

Thursday, March 11, 2004, 17:30–17:45, B

Search for the Θ⁺(1530) in the reaction γ p → pK_S⁰(K⁰)_missing with the CB/TAPS-experiment at ELSA — •Harald van Pee — II. Physikalisches Institut, Heinrich-Buff-Ring 16, 35392 Giessen

Recently a narrow baryon state with S=+1 has been observed by various experiments. A narrow pentaquark state at the corresponding mass has been predicted within the chiral soliton model [1]. With the CB/TAPS-experiment at ELSA we have searched for the Θ⁺ in γ p → pK_S⁰(K⁰)_missing→ p π⁰ π⁰(K⁰)_missing → p 4γ(K⁰)_missing . Using an electron beam of 3.3 GeV, tagged photons from threshold up to 3.1 GeV are available. The 4 photon final state was detected with the Crystal Barrel/TAPS detector which provides an almost 4π-coverage for photon detection. In the p 4γ final state we clearly observe γ p → pπ⁰π⁰ and pπ⁰η, asking in addition for a missing K⁰ evidence for K⁰Θ⁺, p K_S⁰ K_L⁰ and π⁰ K⁰ Σ⁺(1189) is expected. A preliminary analysis shows indeed indications for all these reactions; an enhancement of events in the Θ⁺ mass region has been observed.

[1] D. Diakonov, V. Petrov and M. Polyakov, Z. Phys. A 359, 305 (1997)