A measurement of the effective QED coupling constant alpha(QED)(s) in the time-like region 600-975 MeV by using the Initial State Radiation process e(+)e(-) -> mu(+)mu(-) gamma will be presented. It represents the first measurement of the running of alpha(QED) in this energy region. Our results show more than 5 sigma significance on the hadronic contribution to the running of alpha(s), which is the strongest direct evidence ever achieved both in time- and space-like regions by a single experiment. By using the dipion cross section previously measured at KLOE, the Real and Imaginary part of the shift Delta alpha has been extracted. By fitting the Re Delta alpha, the product of the Branching Fraction BR(omega -> e(+)e(-))BR(omega -> mu(+)mu(-)) has been measured. Status and prospects in gamma gamma physics at KLOE-2 experiment will be also presented.

Measurement of the running of the fine structure constant and gamma-gamma physics at KLOE-2

Mandaglio, G.
Writing – Original Draft Preparation
2017-01-01

Abstract

A measurement of the effective QED coupling constant alpha(QED)(s) in the time-like region 600-975 MeV by using the Initial State Radiation process e(+)e(-) -> mu(+)mu(-) gamma will be presented. It represents the first measurement of the running of alpha(QED) in this energy region. Our results show more than 5 sigma significance on the hadronic contribution to the running of alpha(s), which is the strongest direct evidence ever achieved both in time- and space-like regions by a single experiment. By using the dipion cross section previously measured at KLOE, the Real and Imaginary part of the shift Delta alpha has been extracted. By fitting the Re Delta alpha, the product of the Branching Fraction BR(omega -> e(+)e(-))BR(omega -> mu(+)mu(-)) has been measured. Status and prospects in gamma gamma physics at KLOE-2 experiment will be also presented.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/3115473
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