Determinations of the form factors of semileptonic decays and leptoquark constraints

Jian Zhang; Chong-Xing Yue; Chun-Hua Li

doi:10.1140/epjc/s10052-018-6184-3

EPJ

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2023 Impact factor 4.2

Particles and Fields

Open Access

Eur. Phys. J. C (2018) 78: 695
https://doi.org/10.1140/epjc/s10052-018-6184-3

Regular Article - Theoretical Physics

Determinations of the form factors of semileptonic $D\rightarrow K$ decays and leptoquark constraints

Jian Zhang^*, Chong-Xing Yue and Chun-Hua Li

School of Physics and Electronic Technology, Liaoning Normal University, Dalian, 116029, People’s Republic of China

^* e-mail: zhangjianphy@aliyun.com

Received: 2 May 2018
Accepted: 23 August 2018
Published online: 30 August 2018

Abstract

By analyzing all existing measurements for $D\rightarrow K \ell ^+ \nu _{\ell }$ ( $\ell =e,\ \mu$ ) decays, we find that the determinations of both the vector form factor $$f_+^K(q^2)$$ and scalar form factor $$f_0^K(q^2)$$ for semileptonic $D\rightarrow K$ decays from these measurements are feasible. By taking the parameterization of the one order series expansion of the and , $f_+^K(0)|V_{cs}|$ is determined to be $0.7182\pm 0.0029$ , and the shape parameters of $$f_+^K(q^2)$$ and are $r_{+1}=-2.16\pm 0.007$ and $r_{01}=0.89\pm 3.27$ , respectively. Combining with the average $$f_+^K(0)$$ of $$N_f=2+1$$ and $$N_f=2+1+1$$ lattice calculaltion, the $|V_{cs}|$ is extracted to be $0.964\pm 0.004\pm 0.019$ where the first error is experimental and the second theoretical. Alternatively, the is extracted to be $0.7377\pm 0.003\pm 0.000$ by taking the $|V_{cs}|$ as the value from the global fit with the unitarity constraint of the CKM matrix. Moreover, using the obtained form factors by $$N_f=2+1+1$$ lattice QCD, we re-analyze these measurements in the context of new physics. Constraints on scalar leptoquarks are obtained for different final states of semileptonic $D \rightarrow K$ decays.