Low-energy hadronic cross sections measurements at BaBar and g− 2 of the muon

2016/07/25 by D. Bernard, Denis Bernard
Physics and Astronomy · #Anomalous magnetic dipole moment #Hadron #High-Energy Particle Collisions Research #Muon #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Perturbative QCD #Photon #Photon energy #Physics #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #Quantum mechanics #Standard Model (mathematical formulation) #hep-ex #hep-ph

paper · pdf · doi:10.1016/j.nuclphysbps.2016.12.025

published as Nuclear and Particle Physics Proceedings 282-284 (2017) 132-138 · On behalf of the BaBar Collaboration. Talk given at QCD 16, 19th International Conference in Quantum Chromodynamics, 4 - 8 July 2016, Montpellier, France. Proceedings submitted to Nuclear and Particle Physics Proceedings

arxiv created 2016/07/25 · openalex publication_date 2017/01/01 · arxiv updated 2017/03/21 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

The LO hadronic vacuum polarization (VP) contribution to the muon anomalous magnetic moment a_μ is obtained as the integral as a function of energy of an expression that involves the ratio of the e⁺e^- → hadron cross section to the pointlike muon pair cross section. The former is extracted from experimental data for individual hadronic final states at low energies, and from perturbative QCD at high energies. The BaBar experiment at SLAC has a programme of systematic measurement of the production of the lowest-rest-mass hadronic final states, those that contribute most significantly to the integral. To that purpose, we use a method in which, while the PEP-II storage ring is operated at a constant energy in the center of mass system, √(s), of about 10.6 GeV, events are reconstructed and selected which have been produced with a hadronic final state together with a high-energy photon which may (photon tagging) or may not (no tagging) be observed. In our kinematic configuration the photon is almost always emitted by the electron or by the positron of the initial state, hence the name "initial-state radiation" (ISR). The cross section for the direct e⁺e^- → f production of a final state f at an energy √(s') is then extracted from the differential cross section of the ISR production of the state f with invariant mass √(s'). The programme is almost completed and has lead to a number of first measurements and to an improvement of up to a factor of three of the uncertainties on the contributions of individual channels to a_μ.

Citations

• Precise Measurement of thee+e−→π+π−(γ)Cross Section with the Initial State Radiation Method atBABAR
• Improved predictions for g−2 of the muon and αQED(MZ2)
• High-statistics measurement of the pion form factor in the ρ-meson energy range with the CMD-2 detector
• Final report of the E821 muon anomalous magnetic moment measurement at BNL
• Measurement of σ(e+e−→π+π−) from threshold to 0.85 GeV2 using initial state radiation with the KLOE detector
• The BABAR detector
• Initial-state radiation measurement of thee+e−→π+π−π+π−cross section
• Reevaluation of the hadronic contributions to the muon g−2 and to α (M²_Z)
• On Quantum-Electrodynamics and the Magnetic Moment of the Electron
• Study ofe+e−→pp¯via initial-state radiation atBABAR
• Big-Bang Nucleosynthesis