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ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2001, vol. 86, p. 1698-1701

Direct measurement of the φ(1020) leptonic branching ratio

Achasov M. N., Beloborodov K. I., Berdyugin A. V., Bogdanchikov A. G., Bozhenok A. V., Bukin A. D., Bukin D. A., Burdin S. V., Dimova T. V., Drozdetsky A. A., Druzhinin V. P., Dubrovin M. S., Gaponenko I. A., Golubev V. B., Ivanchenko V. N., Ivanov P. M., Korol A. A., Koshuba S. V., Lysenko A. P., Nesterenko I. N., Pakhtusova E. V., Perevedentsev E. A., Salnikov A. A., Serednyakov S. I., Shary V. V., Shatunov Yu M., Sidorov V. A., Silagadze Z. K., Skrinsky A. N., Usov Yu V., Vasiljev A. V.

The process e+e- → μ+μ-has been studied by the SND detector at the VEPP-2M e+e- collider in the φ(1020)-resonance energy region. The measured effective φ meson leptonic branching ratio B(φ → l+l-) ≡ √B(φ → e+e-)B(φ → μ+μ-) = (2.89 ± 0.10 ± 0.06) × 10-4 agrees well with the Particle Data Group value B(φ → e+e-) = (2.91 ± 0.07) × 10-4, confirming μ-e universality. Without additional assumption of μ-e universality the branching ratio B(φ → μ+μ-) = (2.87 ± 0.20 ± 0.14) × 10-4 was obtained. © 2001 The American Physical Society.