Hadronic transitions {Upsilon}(2S){r_arrow}{Upsilon}(1S)
Using a 73.6thinsppb{sup {minus}1} data sample of {Upsilon}(2S) events collected with the CLEO II detector at the Cornell Electron Storage Ring, we have investigated the hadronic transitions between the {Upsilon}(2S) and the {Upsilon}(1S). The dipion transition {Upsilon}(2S){r_arrow}{Upsilon}(1S){pi}{sup +}{pi}{sup {minus}} was studied using two different analysis techniques. Selecting events in which {Upsilon}(1S){r_arrow}e{sup +}e{sup {minus}},{mu}{sup +}{mu}{sup {minus}} ({open_quotes}exclusive{close_quotes} analysis), and using the {Upsilon}(1S) leptonic branching fractions world averages from the PDG review, we obtained B{bold (}{Upsilon}(2S){r_arrow}{Upsilon}(1S){pi}{sup +}{pi}{sup {minus}}{bold )}=0.189{plus_minus}0.004{plus_minus}0.010, while using a method allowing {Upsilon}(1S){r_arrow}anything ({open_quotes}inclusive{close_quotes} analysis) we obtained B{bold (}{Upsilon}(2S){r_arrow}{Upsilon}(1S){pi}{sup +}{pi}{sup {minus}}{bold )}=0.196{plus_minus}0.002{plus_minus}0.010. The appropriate weighted average of the two measurements gives B{bold (}{Upsilon}(2S){r_arrow}{Upsilon}(1S){pi}{sup +}{pi}{sup {minus}}{bold )}=0.192{plus_minus}0.002{plus_minus}0.010. Combining the exclusive and inclusive results we derive the {Upsilon}(1S) leptonic branching fractions B{sub ee}=0.0229{plus_minus}0.0008{plus_minus}0.0011 and B{sub {mu}{mu}}=0.0249{plus_minus}0.0008{plus_minus}0.0013. We also studied {Upsilon}(2S){r_arrow}{Upsilon}(1S){pi}{sup 0}{pi}{sup 0} and obtained B{bold (}{Upsilon}(2S){r_arrow}{Upsilon}(1S){pi}{sup 0}{pi}{sup 0}{bold )}=0.092{plus_minus}0.006{plus_minus}0.008. Parameters of the {pi}{pi} system (dipion invariant mass spectra, angular distributions) were analyzed and found to be consistent with current theoretical models. Lastly, we searched for the {eta} and single {pi}{sup 0} transitions and obtained the 90{percent} confidence level upper limits B{bold (}{Upsilon}(2S){r_arrow}{Upsilon}(1S){eta}{bold )}{lt}0.0028 and B{bold (}{Upsilon}(2S){r_arrow}{Upsilon}(1S){pi}{sup 0}{bold )}{lt}0.0011. {copyright} {ital 1998} {ital The American Physical Society}
- OSTI ID:
- 641565
- Journal Information:
- Physical Review, D, Journal Name: Physical Review, D Journal Issue: 5 Vol. 58; ISSN PRVDAQ; ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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