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

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.

scholarly journals RECENT NA48/2 RESULTS ON Ke4 AND K3π DECAYS AND DETERMINATION OF THE ππ SCATTERING LENGTHS

2009 ◽  
Vol 24 (02n03) ◽  
pp. 488-492
Author(s):  
◽  
ANDREA BIZZETI
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
High Precision ◽  
Form Factors ◽  
Invariant Mass Spectrum ◽  
S Wave ◽  
Large Samples ◽  
Scattering Lengths

Large samples of K± → 3π and K± → π+π-e±ν (Ke4) decays have been collected by the NA48/2 experiment at CERN SPS. At the π+π- threshold, the π0π0 invariant mass spectrum of the decay K± → π±π0π0 xhibits a Wigner cusp, from which the S-wave ππ scattering lengths are extracted with high precision. The same scattering lengths are also independently determined from the accurate measurement of the form factors in the Ke4 decay K± → π+π-e±ν.

scholarly journals CHIRAL ANOMALY EFFECTS AND THE BABAR MEASUREMENTS OF THE γγ* → π0 TRANSITION FORM-FACTOR

2011 ◽  
Vol 26 (23) ◽  
pp. 4125-4131 ◽  
Author(s):  
T. N. PHAM ◽  
X. Y. PHAM
Keyword(s):  
Form Factor ◽  
Perturbative Qcd ◽  
Virtual Photon ◽  
Transition Form Factor ◽  
High Energy ◽  
Chiral Anomaly ◽  
Steady Increase ◽  
Transition Form ◽  
Babar Data ◽  
Energy Processes

The recent BaBar measurements of the γγ*→π0 transition form-factor show spectacular deviation from perturbative QCD prediction for large spacelike Q2 up to 34 GeV2. When plotted against Q2, Q2F(Q2) shows steady increase with Q2 in contrast with the flat Q2 behavior predicted by perturbative QCD, and at 34 GeV2 is more than 50% larger than the QCD prediction. Stimulated by the BaBar measurements, we revisit our previous paper on the cancellation of anomaly effects in high energy processes Z0→π0γ, e+e- → π0γ and apply our results to the γ*γ→π0 transition form-factor measured in the e+e- → e+e-π0 process with one highly virtual photon. We find that, the transition form-factor F(Q2) behaves as [Formula: see text] and produces a striking agreement with the BaBar data for Q2F(Q2) with m = 132 MeV which also reproduces very well the CLEO data at lower Q2.

scholarly journals $$\omega \rightarrow 3\pi $$ and $$\omega \pi ^{0}$$ transition form factor revisited

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
M. Albaladejo ◽  
◽  
I. Danilkin ◽  
S. Gonzàlez-Solís ◽  
D. Winney ◽  
...  
Keyword(s):  
Form Factor ◽  
Experimental Determination ◽  
Dalitz Plot ◽  
Transition Form Factor ◽  
Decay Amplitude ◽  
Experimental Results ◽  
Transition Form ◽  
Dispersive Analysis ◽  
Low Energies

AbstractIn light of recent experimental results, we revisit the dispersive analysis of the $$\omega \rightarrow 3\pi $$ ω → 3 π decay amplitude and of the $$\omega \pi ^0$$ ω π 0 transition form factor. Within the framework of the Khuri–Treiman equations, we show that the $$\omega \rightarrow 3\pi $$ ω → 3 π Dalitz-plot parameters obtained with a once-subtracted amplitude are in agreement with the latest experimental determination by BESIII. Furthermore, we show that at low energies the $$\omega \pi ^0$$ ω π 0 transition form factor obtained from our determination of the $$\omega \rightarrow 3\pi $$ ω → 3 π amplitude is consistent with the data from MAMI and NA60 experiments.

scholarly journals Meson transition form factor measurements with A2

2019 ◽  
Vol 199 ◽  
pp. 02013
Author(s):  
L. Heijkenskjöld
Keyword(s):  
Form Factor ◽  
Transition Form Factor ◽  
Form Factors ◽  
Precision Measurements ◽  
High Yield ◽  
Transition Form ◽  
Dalitz Decay ◽  
Decay Data ◽  
Electromagnetic Structure ◽  
Photon Interactions

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.

Determination of the η-transition form factor in the γp→pη→pγe+e− reaction

2011 ◽  
Vol 701 (5) ◽  
pp. 562-567 ◽  
Author(s):  
H. Berghäuser ◽  
V. Metag ◽  
A. Starostin ◽  
P. Aguar Bartolomé ◽  
L.K. Akasoy ◽  
...  
Keyword(s):  
Form Factor ◽  
Transition Form Factor ◽  
Transition Form

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

1989 ◽  
Vol 233 (1-2) ◽  
pp. 65-68 ◽  
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

γγ-PHYSICS AT KLOE/KLOE-2

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.

scholarly journals Towards a dispersive determination of the pion transition form factor

2018 ◽  
Vol 166 ◽  
pp. 00013 ◽  
Author(s):  
Stefan Leupold ◽  
Martin Hoferichter ◽  
Bastian Kubis ◽  
Franz Niecknig ◽  
Sebastian P. Schneider
Keyword(s):  
Experimental Data ◽  
Form Factor ◽  
Standard Model ◽  
Model Calculation ◽  
Transition Form Factor ◽  
Current Status ◽  
Transition Form ◽  
Dispersion Theory ◽  
Ongoing Project

We start with a brief motivation why the pion transition form factor is interesting and, in particular, how it is related to the high-precision standard-model calculation of the gyromagnetic ratio of the muon. Then we report on the current status of our ongoing project to calculate the pion transition form factor using dispersion theory. Finally we present and discuss a wish list of experimental data that would help to improve the input for our calculations and/or to cross-check our results.

scholarly journals Dielectrons and Direct Virutal Photons at RHIC-STAR

2020 ◽  
Vol 235 ◽  
pp. 02002
Author(s):  
Chi Yang
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Virtual Photon ◽  
Invariant Mass Spectrum ◽  
Heavy Ion ◽  
Relativistic Heavy Ion Collisions ◽  
Dense Medium ◽  
Model Calculations ◽  
Ion Collisions ◽  
Low Mass

Electromagnetic probes are unique probes of the hot and dense medium cre- ated in relativistic heavy-ion collisions due to their minimal interactions with the partonic and hadronic medium. They can be produced at all stages of a collision, thus they provide unique ways to study the medium properties of the whole collision evolution. We present the dielectron invariant mass spectrum at √sNN = 27, 39, 39, and 62.4 GeV. Comparing to hadronic cocktail simulation, significant excesses of dielectron invariant mass spectrum at low mass are observed. The direct virtual photon invariant yields derived from the low-mass e+e− continuum in Au+Au collisions at √sNN = 200 GeV is presented and the excesses from thermal photons in low transverse momentum (pT) have been observed. Model calculations can simultaneously describe both dielectron low mass excesses and direct virtual photon low pT excesses.

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