0000000000216711
AUTHOR
Christoph Florian Redmer
Measurement of transition form factors in two-photon collisions at BESIII
The two-photon physics program of the BESIII Collaboration is mainly motivated by the need of new measurements of transition form factors as input for the Standard Model calculations of $ \mathop a\nolimits_\mu ^{HLbL} $, the hadronic light-by-light scattering contribution to the anomalous magentic moment of the muon. The large data sets acquired at BESIII allow to study the transition form factors of pseudoscalar mesons in the relevant region of momentum transfer for $ \mathop a\nolimits_\mu ^{HLbL} $. In this presentation the status of the respective measurements for π0,η and η’ mesons are discussed, and prospects for studies of multi-meson systems as well as of doubly-virtual transition …
Hadronic inputs to the (g– 2)μpuzzle
There is a long standing discrepancy of 3 – 4 standard deviations between the direct measurement and the Standard Model prediction of the anomalous magnetic moment of the muon (g – 2) μ . While new direct measurements have been proposed to clarify the situation, theory calculations are completely limited by the accuracy of the hadronic contributions to (g – 2) μ . In order to increase their precision, experimental information can be used as input. In this presentation we will discuss recent and future measurements of relevant hadronic cross sections and transition form factors.
Measurements of Hadronic and Transition Form Factors at BESIII
Motivated by the need of experimental input to improve the Standard Model prediction of the anomalous magnetic moment of the muon aµ, the BESIII Collaboration started a dedicated program to measure hadronic cross sections as well as transition form factors (TFF) with high accuracy. The large data sets acquired by the BESIII Collaboration allow to exploit initial state radiation in order to study hadron production over a wide energy range, as well as two-photon collisions to study the momentum dependence of TFFs in the space like regime. The current status and ongoing investigations in both endeavors are discussed.
The two-photon physics program at BESIII
Abstract One of the main aspects of the two-photon physics program of the BESIII Collaboration is the determination of electromagnetic transition form factors (TFF). Precision measurements of TFF are needed as input to the calculations of the contribution of hadronic light-by-light scattering to the anomalous magnetic moment of the muon a μ . Data acquired with the BESIII detector allow for the determination of TFF of light pseudoscalar mesons at momentum transfers below 2 GeV2, the region of highest relevance for a μ . The measurements of the TFF of π 0 , η and η ′ mesons, as well as pion pairs, are presented, and the potential for a first double-tagged measurement of the pion transition f…
Measurement of hadron form factors at BESIII
The BESIII experiment, operated at the BEPCII e+e- collider in Beijing, has acquired large data sets at center-of-mass energies between 2.0 GeV and 4.6 GeV. One of the key aspects of the physics program of the BESIII collaboration is to test the understanding of QCD at intermediate energies. Applying different experimental techniques, form factors of hadrons are measured. Among these are the pion form factor, as an important input to the (g - 2)μ puzzle, and the electro-magnetic form factors of nucleons and hyperons in the time-like regime. An overview of the recent results and some ongoing studies at BESIII is provided.
Measurement of the Time-like Pion Transition Form Factor at BESIII
The pion transition form factor is an important input to the dispersive approaches of the Standard Model calculations for the anomalous magnetic moment of the muon. We report the prospects of a first measurement at high momentum transfer in the time-like region performed at BESIII. The aim is to improve the uncertainty of the hadronic light-by-light calculations and to shed light on the BaBar-Belle puzzle in the space-like region.
The γγ Physics Program at BESIII
A key motivation for the two-photon physics program of the BESIII collaboration is the need of high precision data on electromagnetic transition form factors as input to the calculations of the contribution of hadronic Light-by-light scattering to the anomalous magnetic moment of the muon. The data collected with the BESIII detector allow to study the momentum dependence of the form factors at small momentum transfers, which is of special relevance for αμ. In this presentation the ongoing measurements of the transition form factors of π0,η and η' mesons, as well as pion pairs, are discussed, and the potential for first double-tagged measurements at BESIII are pointed out.
The hadronic light-by-light contribution to the muon's anomalous magnetic moment
In view of the current 3 - 4 $\sigma$ deviation between theoretical and experimental values for the muon's anomalous magnetic moment, we review the ongoing efforts in constraining the hadronic light-by-light contribution to $a_\mu$ by using dispersive techniques combined with a dedicated experimental program to obtain the required hadronic input.