Researchers Achieve 25% Precision in Rare Decay Calculations Using Lattice QCD and QED Formalism

The rare decay of particles provides a sensitive test of the Standard Model of particle physics, and understanding the underlying mechanisms driving this process remains a significant challenge. Peter Boyle of Brookhaven National Laboratory and the University of Edinburgh, along with En-Hung Chao and Norman Christ from Columbia University, and colleagues, now present a detailed calculation of this decay using lattice quantum chromodynamics, a powerful method for simulating the behaviour of quarks and gluons. Their work achieves an impressive 25% statistical precision in determining the contribution from long-distance effects, and importantly, reveals a destructive interference between these long-distance contributions and those arising from shorter-range interactions. This first-principles calculation offers crucial insights into the fundamental forces governing particle decay, and provides a stringent test of theoretical predictions within the Standard Model.

Lattice QCD Calculation of Kaon Decay Width

Researchers compute the complex, long-distance two-photon-exchange amplitude, a key factor in understanding the rare decay of neutral kaons into pairs of muons, using lattice Quantum Chromodynamics. The calculations utilize simulation parameters mirroring physical conditions and a sophisticated mathematical framework to accurately model this process, achieving a 25% statistical precision on the dispersive part of the amplitude. This delivers, for the first time, a first-principles calculation that determines destructive interference between the long- and short-distance parts of the decay amplitude, offering new insights into the underlying physics.

Two-Photon Exchange in Kaon Decay Calculated

Researchers present a first-principles calculation of the two-photon exchange amplitude, crucial for understanding the rare decay of neutral kaons into muons. The calculation reveals destructive interference between the long-distance two-photon exchange and the short-distance contributions to the decay, a finding previously unconfirmed by such calculations.

By precisely calculating this contribution, researchers can refine predictions for the decay rate and compare them with experimental measurements, potentially revealing new physics at high energy scales. The authors acknowledge that the precision of their results is currently limited by challenges in reconstructing the contribution from intermediate states within the calculation, and future work will focus on improving these reconstructions to further enhance the accuracy of the calculated amplitude and reduce associated uncertainties.