Are leptoquark bosons confined?

Abstract

Recent claims for the discovery of excess fractional charge on matter (1) have proved problematical for particle theorists. Presen* dogma s~ates that if quarks are fractionally charged, they should be confined; if quarks are unconfined, they should have integer charge (2). However, all alternative interpretat ion exis*s in which unconfined fractional charge arises from leptoquark bosons rather than quarks. Leptoquark bosons (LQB's) are defined to be gauge bosons of a c010ur SU 4 group that are distinc~ from the gluons within the embedded ehromodynamie S U 3 group. Fractionally charged LQB's will occur in models in which lepton number is the fourth colour and quarks have conventional fractional charge assignments (3). The idea ~ha* colour is contained within SU4 is not new; P).TI and SALAmi proposed that lepton number be the fourth colour to explain the lepton-hadron universali ty of the weak interactions (3,a). Their utilization of S U 4 classification symmetry to account for identical weak couplings of lepton and hadron doublets is applicable for both integer and fractional quark charge assignments (a). The S U a 15-plot of gauge bosons contains the chromodynamic gluon octet, a new V 15 diagonal member (5), and six LQB's which couple colour to lepton number (quarks r leprous). If quarks are fractionally charged, the leptoquark bosons obtain charges of :~ ~ (3). LQB's acquire mass when the embedding SD~ is broken to chromodynamic SUa . A lower bound for the LQB mass is obtained from the nonobservation of the decay K ~ -+ e~z 9 (fig. 1) (a). Let fxta i'epresen~ the lcp~on-quark-LQB coupling constant at low ( ~ 1 GeV) momentum transfer. The present upper bound on the K ~ e9 decay 2 xiq s ~ ~ ~q 2 101o ra~e constrains the LQB mass mx to satisfy *ax~ (/o ) /GF~ ~--2(~o ) 9 GeV (a).