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Abstract / Description of output
The decreasing uncertainties in theoretical predictions and experimental measurements of several hadronic observables related to weak processes, which in many cases are now smaller than O(1%), require theoretical calculations to include subleading corrections that were neglected so far. Precise determinations of leptonic and semileptonic decay rates, including QED and strong isospinbreaking effects, can play a central role in solving the current tensions in the firstrow unitarity of the CKM matrix. In this work we present the first RBC/UKQCD lattice calculation of the isospinbreaking corrections to the ratio of leptonic decay rates of kaons and pions into muons and neutrinos. The calculation is performed at fixed lattice spacing (a−1 ≃ 1.730 GeV) on a 483 × 96 volume with Nf = 2 + 1 dynamical quarks close to the physical point and domain wall fermions in the Möbius formulation are employed. Longdistance QED interactions are included according to the QEDL prescription and the crucial role of finitevolume electromagnetic corrections in the determination of leptonic decay rates, which produce a large systematic uncertainty, is extensively discussed. Finally, we study the different sources of uncertainty on Vus/Vud and observe that, if finitevolume systematics can be reduced, the error from isospinbreaking corrections is potentially subdominant in the final precision of the ratio of the CKM matrix elements.
Original language  English 

Article number  242 
Pages (fromto)  163 
Number of pages  63 
Journal  Journal of High Energy Physics 
Volume  2023 
Issue number  2 
DOIs  
Publication status  Published  27 Feb 2023 
Keywords / Materials (for Nontextual outputs)
 CKM Parameters
 Hadronic Matrix Elements and Weak Decays
 Lattice QCD
 Standard Model Parameters
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Particle Theory at the Higgs Centre
Ball, R., Boyle, P., Del Debbio, L., Gardi, E., Horsley, R., Kennedy, A., O'Connell, D., Smillie, J. & Zwicky, R.
1/10/17 → 30/09/21
Project: Research