Branching ratio measurement of K_S→ γγ decay using a pure \ks beam in the KLOE detector

2007/07/26 by The KLOE Collaboration
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #hep-ex

paper · pdf · doi:10.48550/arxiv.0707.3933

15 pages, 9 figures, contributed paper to LP07

arxiv created 2007/07/26 · arxiv updated 2012/08/27

Abstract

We have analyzed 1.62 fb^-1 of e⁺e^- collisions at a center of mass energy ∼ M_ϕ collected by the KLOE experiment at DAΦNE. This sample corresponds to a production of ∼ 1.7 billion of \ks \kl pairs which allowed us to search for the rare K_S→ γγ decay. K_S are tagged by the K_L interaction in the calorimeter and the signal is searched for by requiring two additional prompt photons. Strong kinematic requirements reduce the initial 0.5× 10⁶ events to 2300 candidates from which we extract a signal of 600 ± 35 events. By normalizing to the \ks → 2 π⁰ decays counted in the same sample, the measured value of BR(\ks → γγ) is (2.27 ± 0.13(stat.) ^+0.03_-0.04 (syst.)) × 10^-6, in agreement with O(P⁴) Chiral Perturbation Theory predictions.

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