Recent BES measurements and the hadronic contribution to the QED vacuum polarization

TL;DR

This paper updates the calculation of the hadronic contribution to the QED vacuum polarization using recent e+e- annihilation data, refining the value of the running of the fine structure constant at the Z boson mass.

Contribution

It provides a new, more precise estimate of the hadronic contribution to the QED vacuum polarization based on recent experimental measurements.

Findings

Delta alpha (5)_had (s) = 0.02750 +/- 0.00033 at s = m_Z^2

Inclusion of recent measurements from BES, BABAR, CDM-2, KLOE, and SND

Refined estimate of the hadronic contribution to the running of alpha at the Z boson mass

Abstract

We have updated our evaluation of the hadronic contribution to the running of the QED fine structure constant using the recent precise measurements of the e+e- annihilation at the center-of-mass (c.m.s.) energy region between 2.6 and 3.65 GeV performed by the BES collaboration. In the low energy region, around the rho resonance, we include the recent measurements from the BABAR, CDM-2, KLOE and SND collaborations. We obtain Delta alpha (5)_had (s) = 0.02750 +/- 0.00033 at s = m_Z^2.