2025/03/01 by Jwa, Seungyeob, Kim, Jeehun, Kim, Sunghee +3
#FOS: Physical sciences #High Energy Physics - Lattice (hep-lat) #High Energy Physics - Phenomenology (hep-ph)
paper · doi:10.48550/arxiv.2503.00351
We present theoretical results for the indirect CP violation parameter, |εK| , evaluated directly within the Standard Model using lattice QCD inputs including BK , |Vcb| , |Vus| , |Vud| , ξ0 , ξ2 , FK , and the charm quark mass mc . Our analysis reveals a significant tension at the ∼ 5σ level ( 4.6σ to 5.2σ) between the Standard Model prediction and the experimental value of |εK| . The Standard Model prediction, informed by lattice QCD inputs, accounts for only approximately 65% of the experimental value, leaving a 35% discrepancy unexplained. Notably, this tension vanishes when using the inclusive determination of |Vcb| , derived from heavy quark expansion. The discrepancy is therefore tied to the well-known tension between the exclusive and inclusive determinations of |Vcb| . We further report results for |εK| obtained using the Brod--Gorbahn--Stamou (BGS) method based on u--t unitarity, which yields an even stronger discrepancy, in the range of 4.9σ to 5.5σ, when combined with lattice QCD inputs.