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

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journal contribution
posted on 2023-06-08, 18:15 authored by M Gonzalez-Alonso, J Martin Camalich
We discuss the consequences of the approximate conservation of the vector and axial currents for the hadronic matrix elements appearing in ß 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 ß decays are studied, finding for the corresponding Wilson coefficient eS=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 ß decays much more sensitive to nonstandard pseudoscalar interactions than previously thought.

Funding

Particle Physics Theory at Royal Holloway and Sussex; G0742; STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCIL; ST/J000477/1

History

Publication status

  • Published

File Version

  • Published version

Journal

Physical Review Letters (PRL)

ISSN

0031-9007

Publisher

American Physical Society

Volume

112

Page range

042501

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2014-09-10

First Open Access (FOA) Date

2014-09-10

First Compliant Deposit (FCD) Date

2014-09-10

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