Improved measurement of branching fractions for {pi}{pi} transitions among {upsilon}(nS) states

Using samples of (5.93{+-}0.10)x10{sup 6} {upsilon}(3S) decays and (9.11{+-}0.14)x10{sup 6} {upsilon}(2S) decays collected with the CLEO detector, we report improved measurements of the following branching fractions: B({upsilon}(3S){yields}{upsilon}(1S){pi}{sup +}{pi}{sup -})=(4.46{+-}0.01{+-}0.13)%, B({upsilon}(2S){yields}{upsilon}(1S){pi}{sup +}{pi}{sup -})=(18.02{+-}0.02{+-}0.61)%, B({upsilon}(3S){yields}{upsilon}(1S){pi}{sup 0}{pi}{sup 0})=(2.24{+-}0.09{+-}0.11)%, B({upsilon}(2S){yields} {upsilon}(1S){pi}{sup 0}{pi}{sup 0})=(8.43{+-}0.16{+-}0.42)%, and B({upsilon}(3S){yields}{upsilon}(2S){pi}{sup 0}{pi}{sup 0})=(1.82{+-}0.09{+-}0.12)%. In each case, the first uncertainty reported is statistical, while the second is systematic.