Double-tag events in two-photon collisions at LEP

L3 Collaboration

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Double-tag events in two-photon collisions are studied using the L3 detector at LEP centre-of-mass energies from √s = 189 GeV to 209 GeV. The cross sections of the e+e- → e+e-hadrons and YY → hadrons processes are measured as a function of the product of the photon virtualities, Q2 = √Q2 1Q2 2, of the two-photon mass, WYY, and of the variable Y = ln(W2 YY/Q2). The average photon virtuality is 〈Q2 1〉 = 〈Q2 2〉 = 16 GeV2. The results are in agreement with next-to-leading order calculations for the process YY → qq in the interval 2 ≤ Y ≤ 5. An excess is observed in the interval 5 < Y ≤ 7, corresponding to WYY greater than 40 GeV. This may be interpreted as a contribution of resolved photon QCD processes or the onset of BFKL phenomena.

Original languageEnglish (US)
Pages (from-to)39-51
Number of pages13
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number1-2
StatePublished - Apr 4 2002

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© 2002 Elsevier Science B.V. All rights reserved.


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