| Title: | EXPERIMENTAL INVESTIGATION OF THE TWO-PHOTON WIDTHS OF THE χc0 AND χc2 |
| DOI No: | 10.1142/9789812777157_0057 |
| Source: | PHOTON 2001 (pp 283-288)
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| Author(s): | HANS P. PAAR
Physics Department 0319, University of California, San Diego, La Jolla, CA 92037-0319, U.S.A.
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| Abstract: | I present the first observation of the χc0 in photon-photon collisions and measurements of the two-photon widths of the χc0 and χc2. These results were obtained with the CLEO detector at the Cornell e+e- collider CESR and are based upon an integrated luminosity of 12.7 fb-1 obtained at centre-of-mass energies near the ϒ(4S). The Xc have been detected in their decays into π+π-π+π-. We obtained  and  . Using the world average values for  we found Γγγ(χc0) = 3.76 ± 0.65(stat) ± 0.41(syst) ± 1.69(br)keV and Γγγ(χc2) = 0.53 ± 0.15(stat) ± 0.06(syst) ± 0.22(br)keV. The two-photon width of the χc2 agrees with the world average within the large uncertainty. We avoid the 40% branching fraction uncertainties and cancel the systematic uncertainties in the measurements by measuring the ratio Γγγ(χc0)/Γγγ(χc2) and find 7.4 ± 2.4(stat) ± 0.5(syst) ± 0.9(br). Non-perturbative factors in the QCD calculation cancel in the ratio so as a result the ratio has sensitivity to the value of αs. The measurements are in excellent agreement with expectations from QCD. |
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