The Z\to c\bar c\toγγ^{\ast}, Z\to b\bar b\toγγ^{\ast} triangle diagrams and the Z\toγψ, Z\to γΥdecays

Abstract

It is expounded the approach to the Z\toγΨand Z\toγΥdecay study, based on the sum rules for the Z\to c\bar c\toγγ^{\ast} and Z\to b\bar b\toγγ^{\ast} amplitudes and their derivatives. The branching ratios of the Z\toγψand Z\toγΥdecays are calculated for different guesses as to saturation of the sum rules. The lower bounds of \sum_ψ BR(Z\toγψ) = 1.95\cdot 10^{-7} and \sum_Υ BR(Z\toγΥ) = 7.23\cdot 10^{-7} are found. Deviations from the lower bounds are discussed, among them the possibility of BR(Z\toγJ/ψ(1S))\sim BR(Z\toγΥ(1S))\sim 10^{-6}, that could be probably measured in LHC. The angle distributions in the Z\toγψand Z\toγΥdecays are calculated also.

12 pages, 1 figure; improved presentation; reported at the International Seminar "Quarks 2010", Kolomna, Russia, June, 6-12, 2010; accepted in Yadernaya Fizika, scheduled for publication in March, 2011, Yad. Fiz. [Phys. At. Nucl.], volume 74, issue 3 (2011)