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 $\beta$. 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 $\Delta M_{ B_cB^*_c}$ 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.
Categories: hep-ph hep-ex