Direct measurement of the J/ψ leptonic branching fraction

• Published in: Physical review letters 1992-01, Vol.68 (3), p.282-285
• Main Authors: COFFMAN, D, DEJONGH, F, BOLTON, T, BUNNELL, K. O, CASSELL, R. E, COWARD, D. H, KIM, P. C, LABS, J, ODIAN, A, PITMAN, D, SCHINDLER, R. H, TOKI, W, DUBOIS, G. P, WASSERBAECH, S, DRINARD, J. J, GATTO, C, HEUSCH, C. A, LOCKMAN, W. S, SADROZINSKI, H. F. W, SCARLATELLA, EISENSTEIN, B. I, FREESE, T, GLADDING, G, EIGEN, G, IZEN, J. M, STOCKDALE, I. E, TRIPSAS, B, MALLIK, U, WANG, M. Z, BROWN, J. S, BURNETT, T. H, LI, A. D, MIR, R, MOCKETT, P. M, HITLIN, D. G, NEMATI, B, PARRISH, L, WILLUTZKI, H, MATTHEWS, C. G, RICHMAN, J, WEINSTEIN, A. J, WISNIEWSKI, W. J, ZHU, Y
• Format: Article
• Language: English
• Subjects: 662230 - Quantum Chromodynamics- (1992-); 662350 - Decays of Mesons- (1992-); Atomic and molecular physics; BASIC INTERACTIONS; BOSONS; BRANCHING RATIO; CHARMONIUM; Classical and quantum physics: mechanics and fields; COUPLING CONSTANTS; DATA; DECAY; Electronic structure of atoms, molecules and their ions: theory; ELEMENTARY PARTICLES; Exact sciences and technology; EXPERIMENTAL DATA; FIELD THEORIES; General theory of scattering; HADRONIC PARTICLE DECAY; HADRONS; INFORMATION; INTERACTIONS; J PSI-3097 MESONS; LEPTONIC DECAY; MASS SPECTRA; MESONS; NUMERICAL DATA; Other topics in the theory of the electronic structure of atoms, molecules and their ions; PARTICLE DECAY; PARTICLE KINEMATICS; PERTURBATION THEORY; Physics; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; PSI-3685 MESONS; QUANTUM CHROMODYNAMICS; QUANTUM FIELD THEORY; QUARKONIUM; SPECTRA; VECTOR MESONS; WEAK INTERACTIONS; WEAK PARTICLE DECAY
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.68.282

The Mark III Collaboration has measured the {ital J}/{psi} leptonic branching fractions using the process {psi}(2{ital S}){r arrow}{pi}{sup +}{pi}{sup {minus}}{ital J}/{psi}, {ital J}/{psi}{r arrow}{ital l}{sup +}{ital l{minus}}. The results are {ital B}({ital J}/{psi}{r arrow}{ital e}{sup +}{ital e{minus}})=(5.92{plus minus}0.15{plus minus}0.20)% and {ital B}({ital J}/{psi}{r arrow}{mu}{sup +}{mu}{sup {minus}})=(5.90{plus minus}0.15{plus minus}0.19)%, where the first error is statistical and the second is systematic. Assuming lepton universality, the leptonic branching fraction of the {ital J}/{psi} is (5.91{plus minus}0.11{plus minus}0.20)%. This result is used to obtain the strong coupling constant {alpha}{sub {ital s}} and the QCD scale factor {Lambda}{sub MS} (M{bar S} denotes the modified minimal-subtraction scheme).