Synthesis and novel reactivity of halomethyldimethylsulfonium salts

Iodomethyl-, chloromethyl-, and fluoromethyldimethylsulfonium salts, 4b-d, have been synthesized and are observed to be highly reactive molecules that exhibit extraordinary diversity with respect to the nature of their reactivity, undergoing facile direct substitution (S(N)2) reactions, but also being highly susceptible to electron-transfer reactions. Cyclic voltametry experiments indicated that the iodomethyldimethylsulfonium compound, 4b, is a potent electron acceptor, even surpassing the reactivity of perfluoro-n-alkyl iodides in that capacity. The iodo- and chloromethyldimethylsulfonium salts, 4b,c, as well as the analogous iodomethyltrimethylammonium salt, 3a, are shown to be reactive SET acceptors.     

Improved branching ratio measurement for the decay K(0)(L) --> &mgr;(+)&mgr;(-)

We report results from Experiment 871, performed at the BNL AGS, of a measurement of the branching ratio K(0)(L)-->&mgr;(+)&mgr;(-) with respect to the CP-violating mode K(0)(L)-->pi(+)pi(-). This experiment detected over 6200 candidate &mgr;(+)&mgr;(-) events, a factor of 6 more than that seen in all previous measurements combined. The resulting branching ratio gamma(K(0)(L)-->&mgr;(+)&mgr;(-))/gamma(K(0)(L)-->pi(+)pi(-)) = (3. 474+/-0.057)x10(-6) leads to a branching fraction B(K(0)(L)-->&mgr;(+)&mgr;(-)) = (7.18+/-0.17)x10(-9), which is consistent with the current world average, and reduces the uncertainty in this decay mode by a factor of 3.     

A measurement of direct photon production at large pT at the CERN ISR

We have measured direct photon production in pp collisions at the CERN intersecting storage rings for c.m. energies 31 < √s < 63 GeV and transverse momenta up to 9GeV/c, using segmented lead/liquid-argon calorimeters. The ratio of direct photon to π⁰ production is significantly larger than zero, starting at p_T ≈ 4 GeV/c and increasing to values of about 0.4 at 9GeV/c. No significant √s dependence is seen.