Measurement of sigma(e+ e- -> pi+ pi-) from threshold to 0.85 GeV² using Initial State Radiation with the KLOE detector
KLOE Collaboration · Ambrosino, F. · Archilli, F. · Beltrame, P. · Bencivenni, G. · Bini, C. · Bloise, C. · Bocchetta, S. · Bossi, F. · Branchini, P. · Capon, G. · Capussela, T. · Ceradini, F. · Ciambrone, P. · De Lucia, E. · De Santis, A. · De Simone, P. · De Zorzi, G. · Denig, A. · Di Domenico, A. · Di Donato, C. · Di Micco, B. · Dreucci, M. · Felici, G. · Fiore, S. · Franzini, P. · Gatti, C. · Gauzzi, P. · Giovannella, S. · Graziani, E. · Jacewicz, M. · Kluge, W. · Lee-Franzini, J. · Leone, D. · Massarotti, P. · Meola, S. · Miscetti, S. · Müller, S. · Murtas, F. · Napolitano, M. · Nguyen, F. · Passeri, A. · Patera, V. · Santangelo, P. · Taccini, C. · Tortora, L. · Venanzoni, G. · Versaci, R.
Original · EN
We have measured the cross section of the radiative process e+e- -> pi+pi-gamma with the KLOE detector at the Frascati phi-factory DAPHNE, from events taken at a CM energy W=1 GeV. Initial state radiation allows us to obtain the cross section for e+e- -> pi+pi-, the pion form factor |Fₚi|² and the dipion contribution to the muon magnetic moment anomaly, Delta aₘupipi = (478.5+-2.0stat+-5.0syst+-4.5th) x 10⁻¹⁰ in the range 0.1 < Mpipi² < 0.85 GeV², where the theoretical error includes a SU(3) ChPT estimate of the uncertainty on photon radiation from the final pions. The discrepancy between the Standard Model evaluation of aₘu and the value measured by the Muon g-2 collaboration at BNL is confirmed.
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