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

6533b824fe1ef96bd1280948

RESEARCH PRODUCT

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

Jason Brudvik V. Metag Yasser Maghrbi L.v. Filʼkov B. Krusche A. Starostin E. F. Mcnicoll P. Aguar Bartolomé J. Robinson B. Demissie M. Martinez-fabregate F. Pheron D. Werthmüller V. Lisin P. Pedroni S. Schumann R. W. Novotny S. Cherepnya D. P. Watts O. Jahn I. Zamboni D. I. Sober C. M. Tarbert H. J. Arends Michaela Thiel V. L. Kashevarov V. L. Kashevarov R. Kondratiev I. M. Suarez D. Mekterovic P. Drexler Sasa Micanovic M. Ostrick M. Kotulla K. Bantawa G. Rosner L. K. Akasoy T. Rostomyan V. S. Bekrenev D. M. Manley M. Korolija I. Supek A. N. Mushkarenkov Anthony W. Thomas D. I. Glazier D. Hornidge A. Koulbardis A. Knezevic R.o. Owens K. Livingston S. N. Prakhov E. J. Downie F. Zehr I. J. D. Macgregor W. J. Briscoe B. Lemmer S. P. Kruglov T.c. Jude J. C. Mcgeorge R. Beck R. Beck M. Unverzagt A. Fix H. Berghäuser A. Nikolaev A. Polonski B. M. K. Nefkens J. R. M. Annand E. Heid M. Dieterle D. Branford A. Braghieri

subject

Physics Nuclear and High Energy Physics Mass distribution 010308 nuclear & particles physics Point particle Branching fraction Form factor (quantum field theory)Particle accelerator 01 natural sciences law.invention Nuclear physics law 0103 physical sciences High Energy Physics::Experiment Invariant mass Nuclear Experiment 010306 general physics Order of magnitude Crystal Ball

description

The Dalitz decay η→γe+e− has been measured using the combined Crystal Ball and TAPS photon detector setup at the electron accelerator MAMI-C. Compared to the most recent transition form-factor measurement in the e+e− channel, statistics have been improved by one order of magnitude. The e+e− invariant mass distribution shows a deviation from the QED prediction for a point-like particle, which can be described by a form-factor. Using the usual monopole transition form-factor parameterization, F(m2)=(1−m2/Λ2)−1, a value of Λ−2=(1.92±0.35(stat)±0.13(syst)) GeV−2 has been determined. This value is in good agreement with a recent measurement of the η Dalitz decay in the μ+μ− channel and with recent form-factor calculations. An improved value of the branching ratio BR(η→γe+e−)=(6.6±0.4(stat)±0.4(syst))⋅10−3 has been determined.

year	journal	country	edition	language
2011-07-01	Physics Letters B

https://doi.org/10.1016/j.physletb.2011.06.069