Observation of the color coherence effect in sub-jet multiplicity of three-jet and four-jet events in e+e− annihilations

We have measured the ratio of the average sub-jet multiplicity in 3-jet to 2-jet events, R(23), and 4-jet to 2-jet events, R(24), using the e(+)e(-) annihilation data at root s = 58 GeV obtained from the AMY detector. We compare the measured values of R(23) and R(24) With the predictions of coherent and incoherent Monte Carlo models. R(23) is also compared with the NLLA calculations to all-orders. The color coherence effect has been observed to contribute to the suppression of R(23) and R(24) Also, the difference of the behavior between gluon jets in 3-jet and 4-jet events has been studied.