New chiral structures for nucleon baryon number violating decays

Abstract: We examine the most general nucleon decay interactions that involve three light quarks without being acted upon by a derivative. We identify four generic operator structures that correspond to the irreducible representations in the chiral group ${\rm SU(3)}{\tt L}\otimes {\rm SU(3)}{\tt R}$ of QCD, {$\pmb{8}{\tt L}\otimes \pmb{1}{\tt R}$, $\bar{\pmb{3}}{\tt L}\otimes \pmb{3}{\tt R}$, $\pmb{6}{\tt L}\otimes \pmb{3}{\tt R}$, $\pmb{10}{\tt L}\otimes \pmb{1}{\tt R}$}, plus their chirality partners under the interchange of chiralities ${\tt L}\leftrightarrow {\tt R}$. While half of them have been extensively discussed in the literature, the other half, $\pmb{6}{\tt L(R)}\otimes \pmb{3}{\tt R(L)}$ and $\bar{\pmb{10}}{\tt L(R)}\otimes \pmb{1}{\tt R(L)}$, are identified for the first time. We perform chiral matching for these interactions at the leading chiral order and find that each has a unique chiral realization in terms of the octet baryons and pseudoscalars. Notably, the chiral interaction in the $\pmb{6}{\tt L(R)}\otimes \pmb{3}{\tt R(L)}$ representation appears at the same chiral order as those of the known ones, while the one in the $\pmb{10}{\tt L(R)}\otimes \pmb{1}{\tt R(L)}$ representation appears at a higher chiral order. These new structures are prevalent in effective field theories and UV models, and offer novel experimental avenues to search for baryon number violating nucleon decays.