期刊
PHYSICS LETTERS B
卷 726, 期 1-3, 页码 187-193出版社
ELSEVIER
DOI: 10.1016/j.physletb.2013.08.055
关键词
Dark forces; Gauge vector boson
资金
- EU Integrated Infrastructure Initiative HadronPhysics Project [RII3-CT-2004-506078]
- European Commission [FP7-INFRASTRUCTURES-2008-1, 227431]
- Polish National Science Centre [86/2/N-DFG/07/2011/0, 0320/B/H03/2011/40, 2011/01/B/ST2/00431, 2011/03/B/ST2/01847, 0312/B/H03/2011/40]
- Foundation for Polish Science
- Swedish Research Council
- Knut and Alice Wallenberg Foundation
- Forschungszentrum Julich FFE Funding Program of the Julich Center for Hadron Physics
The presently world largest data sample for pi(0) -> gamma e(+)e(-) decays studies containing nearly 5 x 10(5) events was collected using the WASA detector at COSY. A search for a dark photon U produced in the pi(0) -> gamma U -> gamma e(+)e(-) decay from the pp -> pp pi(0) reaction was carried out. An upper limit on the square of the U -> gamma mixing strength parameter epsilon(2) of 5 x 10(-6) at 90% CL was obtained for the mass range 20 MeV < M-U < 100 MeV. This result together with other recent experimental limits significantly reduces the M-U vs. epsilon(2) parameter space which could explain the presently seen deviation between the Standard Model prediction and the direct measurement of the anomalous magnetic moment of the muon. (C) 2013 Elsevier B.V. All rights reserved.
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