Meson transition form factor measurements with A2

Meson transition form factors (TFF) describe the electromagnetic structure of mesons and hence provide an important tool for the understanding of the meson-photon interactions. The A2 experiment at MAMI provides a high yield of light mesons produced in photo-induced reactions on protons, which makes the experiment ideal for precision measurements of meson TFFs via studies of meson decays. The A2 collaboration has recently published results of TFFs obtained from measurements of Dalitz decays of the π0 and η mesons as well as the ω → π0e+e− decay. For the study of the η′ Dalitz decay, data has been collected and is being analysed. As a ongoing endeavour, A2 is performing a dedicated measurement of the π0 TFF with statistics increased by several factors compared to the previous A2 result.

Download Full-text

INFRARED RENORMALON EFFECTS ON LIGHT MESONS ELECTROMAGNETIC TRANSITION FORM FACTOR FMγ*(Q2, ω)

International Journal of Modern Physics A ◽

10.1142/s0217751x03013806 ◽

2003 ◽

Vol 18 (07) ◽

pp. 1023-1050 ◽

Cited By ~ 3

Author(s):

YEGANA V. MAMEDOVA

Keyword(s):

Form Factor ◽

Perturbative Qcd ◽

Transition Form Factor ◽

Form Factors ◽

Transition Form ◽

Coupling Constant ◽

Electromagnetic Transition ◽

Qcd Factorization ◽

Factorization Formula ◽

Light Mesons

The light pseudoscalar π0, η and η′ mesons electromagnetic transition γ* + γ* → M form factors FMγ*(Q2,ω) are calculated, applying the perturbative QCD factorization formula and the frozen coupling constant approximation. In the computations the O(αS) order expression for FMγ*(Q2,ω) and the mesons' infrared renormalon corrected distribution amplitudes are used. In the case of the η and η′ mesons, the SUf(3) ordinary octet-singlet mixing scheme is utilized. Comparisons are made with the results obtained, employing the mesons' ordinary distribution amplitudes and with γ + γ* → M transition form factors.

Download Full-text

PION FORM FACTORS AT INTERMEDIATE MOMENTUM TRANSFER IN A COVARIANT APPROACH

International Journal of Modern Physics A ◽

10.1142/s0217751x96000298 ◽

1996 ◽

Vol 11 (04) ◽

pp. 655-675 ◽

Cited By ~ 1

Author(s):

ADAM SZCZEPANIAK ◽

ANTHONY G. WILLIAMS

Keyword(s):

Wave Function ◽

Form Factor ◽

Momentum Transfer ◽

Transition Form Factor ◽

Form Factors ◽

Transition Form ◽

Gauge Invariant ◽

Pion Wave Function ◽

Covariant Gauge ◽

Text Component

We study the pion electromagnetic and γ*+π0→γ transition form factors at intermediate momentum transfer. We calculate soft, nonperturbative corrections to the leading perturbative amplitudes which arise from the [Formula: see text] component of the pion wave function. We work in Minkowski space and use a Lorentz-covariant, gauge-invariant generalized perturbative integral representation for the [Formula: see text] amplitudes. For the transition form factor we find relative insensitivity to the detailed nonperturbative structure of the wave function for |q2|≳10 GeV 2, whereas considerable sensitivity is found for the electromagnetic form factor.

Download Full-text

Nucleon and Δ electromagnetic form factors

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194515600897 ◽

2015 ◽

Vol 39 ◽

pp. 1560089

Author(s):

Erik Bartoš ◽

Stanislav Dubnička ◽

Anna-Zuzana Dubničková

Keyword(s):

Form Factor ◽

Magnetic Dipole ◽

Transition Form Factor ◽

Form Factors ◽

Dipole Transition ◽

Nucleon Resonance ◽

Electromagnetic Form Factors ◽

Analytic Model ◽

Transition Form ◽

Measured Ratio

The unitary and analytic model for nucleons works very well. The model for spin [Formula: see text] baryons can predict static parameters for [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]. We prepared the scheme how to construct the model also for [Formula: see text] nucleon resonance. It was used to describe transition form factor [Formula: see text] and the experimentally measured ratio [Formula: see text] with the help of relations for magnetic dipole transition and charge quadrupole form factors.

Download Full-text

Dalitz decay. π0 → γe+e− and the π0 electromagnetic transition form factor

Physics Letters B ◽

10.1016/0370-2693(89)90616-3 ◽

1989 ◽

Vol 233 (1-2) ◽

pp. 65-68 ◽

Cited By ~ 22

Author(s):

H. Fonvieille ◽

N. Bensayah ◽

J. Berthot ◽

P. Bertin ◽

B. Bihoreau ◽

...

Keyword(s):

Form Factor ◽

Transition Form Factor ◽

Transition Form ◽

Dalitz Decay ◽

Electromagnetic Transition

Download Full-text

γγ-PHYSICS AT KLOE/KLOE-2

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194514603950 ◽

2014 ◽

Vol 35 ◽

pp. 1460395

Author(s):

D. BABUSCI ◽

Keyword(s):

Form Factor ◽

Invariant Mass ◽

Transition Form Factor ◽

Transition Form ◽

Two Photon ◽

Photon Interactions

Photon-photon interactions have been studied at the ϕ-factory DAΦNE with the detector KLOE operating the machine at [Formula: see text] GeV, without tagging of the final leptons. The results about the γγ → η process and the evidence for γγ → π0π0 production at low π0π0 invariant mass are reviewed. The process γγ → π0 will be studied at KLOE-2 running the machine at ϕ-peak thanks to new lepton tagger detectors. In particular, the possibility to measure the two-photon width of π0 and the π0γ*γ transition form factor in the low (space-like) Q2 region is considered.

Download Full-text

STUDY OF THE η → γe+e- DECAY WITH THE WASA-at-COSY

International Journal of Modern Physics A ◽

10.1142/s0217751x11052359 ◽

2011 ◽

Vol 26 (03n04) ◽

pp. 650-651

Author(s):

◽

MAŁGORZATA HODANA

Keyword(s):

Form Factor ◽

Mass Spectrum ◽

Invariant Mass ◽

Virtual Photon ◽

Transition Form Factor ◽

Invariant Mass Spectrum ◽

Transition Form ◽

Lepton Pairs ◽

Dalitz Decay

In October 2008, the WASA-at-COSY collected more than 107 events for the pd → 3 He η reaction. The aim is the determination of the invariant mass of the lepton pairs created in the Dalitz decay η → γe+e-. The e+e- invariant mass spectrum is directly related to the distribution of the four-momentum squared of the virtual photon from the η → γγ* process and hence it allows for the study of the transition form factor which in turn reflects the structure of the decaying meson.

Download Full-text