Observation of $D\to {\bar{K}}_1(1270){\mu }^{+}{\nu }_{\mu }$ and test of lepton flavor universality with $D\to {\bar{K}}_1(1270){\ell }^{+}{\nu }_{\ell }$

Abstract

By analyzing 7.93 $\mathrm{f}{\mathrm{b}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector operated at the BEPCII collider, we report the observation of the semimuonic decays of $D^{+}\to {\bar{K}}_1(1270{)}^0{\mu }^{+}{\nu }_{\mu }$ and $D^0\to K_1(1270{)}^{-}{\mu }^{+}{\nu }_{\mu }$ with statistical significances of $12.5\sigma$ and $6.0\sigma$, respectively. Their decay branching fractions are determined to be $\mathcal{B}[D^{+}\to {\bar{K}}_1(1270{)}^0{\mu }^{+}{\nu }_{\mu }]=(2.36\pm 0.20_{-0.27}^{+0.18}\pm 0.48)\times 10^{-3}$ and $\mathcal{B}[D^0\to K_1(1270{)}^{-}{\mu }^{+}{\nu }_{\mu }]=(0.78\pm 0.11_{-0.09}^{+0.05}\pm 0.15)\times 10^{-3}$, where the first and second uncertainties are statistical and systematic, respectively, and the third originates from the input branching fraction of ${\bar{K}}_1(1270{)}^0\to K^{-}{\pi }^{+}{\pi }^0$ or $K_1(1270{)}^{-}\to K^{-}{\pi }^{+}{\pi }^{-}$. Combining our branching fractions with the previous measurements of $\mathcal{B}[D^{+}\to {\bar{K}}_1(1270{)}^0{e}^{+}{\nu }_e]$ and $\mathcal{B}[D^0\to K_1(1270{)}^{-}{e}^{+}{\nu }_e]$, we determine the branching fraction ratios to be $\mathcal{B}[D^{+}\to {\bar{K}}_1(1270{)}^0{\mu }^{+}{\nu }_{\mu }]/\mathcal{B}[D^{+}\to {\bar{K}}_1(1270{)}^0{e}^{+}{\nu }_e]=1.03\pm 0.14\begin{array}{c}+0.11\\ -0.15\end{array}$ and $\mathcal{B}[D^0\to K_1(1270{)}^{-}{\mu }^{+}{\nu }_{\mu }]/\mathcal{B}[D^0\to K_1(1270{)}^{-}{e}^{+}{\nu }_e]=0.74\pm 0.13\begin{array}{c}+0.08\\ -0.13\end{array}$. Using the branching fractions measured in this work and the world-average lifetimes of the $D^{+}$ and $D^0$ mesons, we determine the semimuonic partial decay width ratio to be $\Gamma [D^{+}\to {\bar{K}}_1(1270{)}^0{\mu }^{+}{\nu }_{\mu }]/\Gamma [D^0\to K_1(1270{)}^{-}{\mu }^{+}{\nu }_{\mu }]=1.22\pm 0.10\begin{array}{c}+0.06\\ -0.09\end{array}$, which is consistent with unity as predicted by isospin conservation.

11 pages, 5 figures

References in corpus (15)

• Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of 2021
• Global Fit to Modified Neutrino Couplings and the Cabibbo-Angle Anomaly
• Beta decays as sensitive probes of lepton flavor universality
• Measurements of the cross sections for $e^{+}{e}^{-}\to \mathrm{hadrons}$ at 3.650, 3.6648, 3.773 GeV and the branching fraction for $\psi (3770)\to \mathrm{non}-D\bar{D}$
• Branching fractions of semileptonic $D$ and $D_s$ decays from the covariant light-front quark model
• Recent Progress in Leptonic and Semileptonic Decays of Charmed Hadrons
• Discerning new physics in charm meson leptonic and semileptonic decays
• Hadronic D decays involving even-parity light mesons
• Measurement of the integrated luminosity of the data collected at 3.773 GeV by BESIII from 2021 to 2024
• Erratum to "Measurement of the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ cross section between 600 and 900 MeV using initial state radiation"
• Study of the K+ pi+ pi- Final State in B+ -> J/psi K+ pi+ pi- and B+ -> psi-prime K+ pi+ pi-
• Semileptonic $D_q\to K_1\ell \nu$ and nonleptonic $D\to K_1\pi$ decays in three--point QCD sum rules and factorization approach
• Observation of $D^0\to K_1(1270{)}^{-}{e}^{+}{\nu }_e$
• Signatures of the two $K_1(1270)$ poles in $D^{+}\to \nu e^{+}VP$ decay
• Up-down Asymmetries and Angular Distributions in $D\to K_1(\to K\pi \pi ){\ell }^{+}{\nu }_{\ell }$

Cited by in corpus (1)

• Exclusive semileptonic decays of $D$ and $D_s$ mesons into orbitally and radially excited states of strange and light mesons