Summary
In an experiment performed at Adone, the Frascati 2×1.5 GeV electron-positron storage ring, the e+e− wide-angle elastic-scattering process was investigated. In this paper we present the analysis of approximately 1700 e+e− Bhabha scattering events collected at several energies of the incident electron and positron beams between 0.8 and 1.0 GeV; this corresponds in our experimental apparatus to an averaged momentum transfer to the virtual spacelike photon ranging within ∼(1.0÷1.7) (GeV/c)2. In the energy range explored the experimental data show a slope and an absolute value in agreement with the predictions of quantum electrodynamics to within the experimental errors of ∼10%.
Riassunto
In un esperimento eseguito con Adone, l’anello di accumulazione per elettroni e positoni da 2×1.5 GeV dei Laboratori Nazionali di Frascati, è stato studiato il processo di diffusione elastica di elettroni e positoni a grande angolo. In questo lavoro presentiamo l’analisi di circa 1700 eventi di diffusione Bhabha raccolti a varie energie dei fasci incidenti fra 0.8 e 1.0 GeV; corrispondenti, nel nostro apparato sperimentale, a momenti trasferiti medi al fotone virtuale di tipo spazio di ∼(1.0÷1.7) (GeV/c)2. I risultati sperimentali sono in accordo, sia come dipendenza dall’energia che in valore assoluto, con le previsioni date dalla elettrodinamica quantistica entro gli errori sperimentali di ∼10%.
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References
F. Amman et al.: Proceedings of the International Conference on High-Energy Accelerators (Dubna, 1963), p. 249;F. Amman et al.: Proceedings of the V International Conference on High-Energy Accelerators (Frascati, 1965), p. 703;F. Amman et al.: Proceedings of the Symposium International sur les Anneaux de Collisions (Saclay, 1966), III-2-1;F. Amman, R. Andreani, M. Bassetti, M. Bernardini, A. Cattoni, V. Chimenti, G. F. Corazza, D. Fabiani, E. Ferlenghi, A. Massarotti, C. Pellegrini, M. Placidi, M. Puglisi, F. Soso, S. Tazzari, F. Tazzioli andG. Vignola:Lett. Nuovo Cimento,1, 729 (1969).
B. Bartoli, B. Coluzzi, F. Felicetti, V. Silvestrini, G. Goggi, D. Scannicchio, G. Marini, F. Massa andF. Vanoli:Nuovo Cimento,70 A, 615 (1970).
G. Barbiellini, B. Borgia, M. Conversi andR. Santonico:Rendiconti della Classe di Scienze Mat. Fis. e Nat. dell’Acc. Naz. dei Lincei,44, 233 (1968).
Adone works with a 3rd harmonic R.F. system, so there are three bunches of e+ and three bunches of e− each between 1 and 2 ns (f.w.h.m.) long; they cross the R.F. cavity when the R.F. phase equals the synchronous phase\(\bar \varphi \), which is slightly dependent on the machine energy, and collide with each other in the experimental sections every ∼100 ns.
This correction has been discussed at greater length inour paper (2)B. Bartoli, B. Coluzzi, F. Felicetti, V. Silvestrini, G. Goggi, D. Scannicchio, G. Marini, F. Massa andF. Vanoli:Nuovo Cimento,70 A, 615 (1970). on multiple particle production from e+e− interactions, where this kind of contamination is more severe. The actual value of the normalization factor (to be applied, for appropriate subtraction, to the e-gas interaction events detected in the one-beam background runs) has been obtained by comparing, after subtracting cosmic-rays events, the counting rates of theT i ’s telescopes. Indeed these rates are directly associated with the interactions of the beam with the residual gas in the machine.
The symmetry of the machine and the fact that the data were collected during a long period of time, averaging over possible slight changes of the working conditions of the machine, make it reasonable to assume the overall results to be unaffected by the fact that small- and large-angle clastic scatterings were measured in different straight sections of Adone.
See, for instance,A. I. Akhiezer andV. Beresteskii:Quantum Electrodynamics (New York, 1965), p. 502.
Private communications from Adone machine staff.
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Bartoli, B., Coluzzi, B., Felicetti, F. et al. Electron-positron elastic scattering at high energies. Nuovo Cimento A (1965-1970) 70, 603–614 (1970). https://doi.org/10.1007/BF02734497
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DOI: https://doi.org/10.1007/BF02734497