Evidence for Two-Body Hadronic Decays of the Upsilon

Abstract

We describe a search for hadronic decays of the Y(1S), Y(2S), and Y(3S) resonances to the exclusive final states rho pi, K*(892) Kbar, rho a2(1320), omega f2(1270), phi f2'(1525), K*(892) K2*(1430)bar, b1(1235) pi, K1(1270) Kbar, and K1(1400) Kbar. Upper limits at 90% CL are set for all these decays from all three resonances below 33x10**-6; in particular, B(Y(1S)--> rho pi) < 4x10**-6 is the smallest such upper limit. For two modes, a branching fraction of zero can be ruled out with a statistical significance of more than 5sigma: B(Y(1S) --> phi f2'(1525)) = (7 +3-2(stat) +-1(syst)) x 10**-6 and B(Y(1S) --> K1(1400) Kbar) = (14 +4-3(stat) +-2(syst)) x 10**-6. Production of K1(1270) Kbar in Y(1S) decay is suppressed relative to that of K1(1400) Kbar. These results add another piece to the challenging ``rho-pi puzzle'' of the charmonium system, placing constraints on models of how quantum chromodynamics should be applied to heavy quarkonia. All results are preliminary.