SU(3) symmetry breaking in decay constants and electromagnetic properties of pseudoscalar heavy mesons

In this paper, the decay constants and mean square radii of pseudoscalar heavy mesons are studied in the SU(3) symmetry breaking. Within the light-front framework, the ratios $f_{D_s}/f_D$ and $f_{B_s}/f_B$ are individually estimated using the hyperfine splittings in the $D_{(s)}^*-D_{(s)}$ and $B_{(s)}^*-B_{(s)}$ states and the light quark masses, $m_{s,q}$ ($q=u,d$), to extract the wave function parameter $β$. The values $f_{D_s}/f_D= 1.29\pm0.07$ and $f_{B_s}/f_B= 1.32\pm 0.08$ are obtained, which are not only chiefly determined by the ratio of light quark masses $m_s/m_q$, but also insensitive to the heavy quark masses $m_{c,b}$ and the decay constants $f_{D,B}$. The dependence of $f_{B_c}/f_B$ on $ΔM_{B_cB^*_c}$ with the varied charm quark masses is also shown. In addition, the mean square radii are estimated as well. The values $\sqrt{<r^2_{D_s^+}><r^2_{D^+}>} =0.740^{-0.041}_{+0.050}$ and $\sqrt{<r^2_{B_s^0}><r^2_{B^0}>} =0.711^{-0.049}_{+0.058}$ are obtained, and the sensitivities of $<r^2_P >$ on the heavy and light quark masses are similar to those of the decay constants.

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