The 26th International Workshop on Weak Interactions and Neutrinos (WIN2017)

$R_K$ and $R_{K^{\ast}}$ beyond the Standard Model

Not scheduled

20m

Conference Center (UC Irvine, Irvine, CA, USA)

Working Group Sessions Flavor and Precision Physics Working Group

Speaker

Ivan Nisandzic (Technische Universitat Dortmund)

Description

Measurements of the ratio of $B \to K^* \mu \mu $ to $B \to K^* e e $ branching fractions, $R_{K^*}$, by the LHCb collaboration strengthen the hints from previous studies with pseudoscalar kaons, $R_K$, for the breakdown of lepton universality, and therefore the Standard Model (SM), to $\sim 3.5 \sigma$. Complementarity between $R_K$ and $R_{K^*}$ allows to pin down the Dirac structure of the new contributions to be predominantly SM-like chiral, with possible admixture of chirality-flipped contributions of up to ${\cal{O}}( \mbox{few} 10 \%)$. Scalar and vector leptoquark representations $(S_3,V_1,V_3)$ plus possible ($\tilde S_2,V_2$) admixture can explain $R_{K,K^*}$ via tree level exchange. Flavor models naturally predict leptoquark masses not exceeding a few TeV, with couplings to third generation quarks at $O(0.1)$, implying that this scenario can be directly tested at the LHC.