# Hep/Astro Seminar -- Wednesday 23rd February, 2000

##
"Nucleon Decay Matrix Elements from Lattice QCD"

##
Y. Kuramashi (Tsukuba U)

- Contact the speaker by
E-mail.

### Abstract

We present a model-independent calculation of hadron
matrix elements for all dimension-six operators associated with baryon
number violating processes using lattice QCD. The calculation is
performed with the Wilson quark action in the quenched approximation
at $\beta=6/g^2=6.0$ on a $28^2\times 48\times 80$ lattice. Our
results cover all the matrix elements required to estimate the partial
lifetimes of (proton,neutron)$\rightarrow$($\pi,K,\eta$) +(${\bar
\nu},e^+,\mu^+$) decay modes. We point out the necessity of
disentangling two form factors that contribute to the matrix element;
previous calculations did not make the separation, which led to an
underestimate of the physical matrix elements. With a correct
separation, we find that the matrix elements have values $3-5$ times
larger than the smallest estimates employed in phenomenological
analyses of the nucleon decays, which could give strong constraints on
several GUT models. We also find that the values of the matrix
elements are comparable with the tree-level predictions of chiral
lagrangian.

## 3:30pm, Smith Lab 4079

Jens O. Andersen(jensoa@pacific.mps.ohio-state.edu),
last updated 24-SEP-97.