Isospin breaking in the nucleon mass and the sensitivity of β decays to new physics

Gonzalez-Alonso, M and Camalich, J Martin (2014) Isospin breaking in the nucleon mass and the sensitivity of β decays to new physics. Physical Review Letters (PRL), 112. 042501. ISSN 0031-9007

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We discuss the consequences of the approximate conservation of the vector and axial currents for the hadronic matrix elements appearing in β decay if nonstandard interactions are present. In particular, the isovector (pseudo)scalar charge gS(P) of the nucleon can be related to the difference (sum) of the nucleon masses in the absence of electromagnetic effects. Using recent determinations of these quantities from phenomenological and lattice QCD studies we obtain the accurate values gS=1.02(11) and gP=349(9) in the modified minimal subtraction scheme at μ=2  GeV. The consequences for searches of nonstandard scalar interactions in nuclear β decays are studied, finding for the corresponding Wilson coefficient εS=0.0012(24) at 90% C.L., which is significantly more stringent than current LHC bounds and previous low-energy bounds using less precise gS values. We argue that our results could be rapidly improved with updated computations and the direct calculation of certain ratios in lattice QCD. Finally, we discuss the pion-pole enhancement of gP, which makes β decays much more sensitive to nonstandard pseudoscalar interactions than previously thought.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QC Physics > QC0770 Nuclear and particle physics. Atomic energy. Radioactivity > QC0793 Elementary particle physics
Depositing User: Catrina Hey
Date Deposited: 10 Sep 2014 11:34
Last Modified: 01 Apr 2017 08:13

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Project NameSussex Project NumberFunderFunder Ref
Particle Physics Theory at Royal Holloway and SussexG0742STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCILST/J000477/1