Long-distance contributions to neutrinoless double beta decay
Neutrinoless double beta decay, if detected, would prove that neutrinos are Majorana fermions and provide the direct evidence for lepton number violation. If such decay would exist in nature, then $$\pi^-\pi^-\to ee$$ and $$\pi^-\to\pi^+ ee$$ (or equivalently $$\pi^-e^+\to\pi^+ e^-$$) are the two simplest processes accessible via first-principle lattice QCD calculations. In this work, we calculate the long-distance contributions to the $$\pi^-\to\pi^+ee$$ transition amplitude using four ensembles at the physical pion mass with various volumes and lattice spacings. We adopt the infinite-volume reconstruction method to control the finite-volume effects arising from the (almost) massless neutrino. Providing the lattice QCD inputs for chiral perturbation theory, we obtain the low energy constant $$g_\nu^{\pi\pi}(m_\rho)=-10.89(28)_\text{stat}(74)_\text{sys}$$, which is close to $$g_\nu^{\pi\pi}(m_\rho)=-11.96(31)_\text{stat}$$ determined from the crossed-channel $$\pi^-\pi^-\to ee$$ decay.
- Research Organization:
- Univ. of Connecticut, Storrs, CT (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- Grant/Contract Number:
- SC0010339; AC02-06CH11357
- OSTI ID:
- 1575954
- Alternate ID(s):
- OSTI ID: 1596009
- Journal Information:
- Physical Review D, Journal Name: Physical Review D Vol. 100 Journal Issue: 9; ISSN 2470-0010
- Publisher:
- American Physical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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