Article

# Charmed-Meson Decay Constants in Three-Flavor Lattice QCD

Department of Physics, Columbia University, New York, New York, United States

Physical Review Letters (Impact Factor: 7.73). 10/2005; 95(12):122002. DOI: 10.1103/PhysRevLett.95.122002 Source: OAI

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**ABSTRACT:**We report on a first next-to-next-to-leading order calculation of the decay constants of the D (D⁎D⁎) and B (B⁎B⁎) mesons using a covariant formulation of chiral perturbation theory. It is shown that, using the state-of-the-art lattice QCD results on fDs/fDfDs/fD as input, one can predict quantitatively the ratios of fDs⁎/fD⁎, fBs/fBfBs/fB, and fBs⁎/fB⁎ taking into account heavy-quark spin-flavor symmetry breaking effects on the relevant low-energy constants. The predicted relations between these ratios, fDs⁎/fD⁎<fDs/fD and fBs/fB>fDs/fDfBs/fB>fDs/fD, and their light-quark mass dependence should be testable in future lattice QCD simulations, providing a stringent test of our understanding of heavy quark spin-flavor symmetry, chiral symmetry and their breaking patterns.Physics Letters B 07/2012; 713(s 4–5):453–456. DOI:10.1016/j.physletb.2012.06.025 · 6.02 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We compute the leptonic decay constants $f_{D^+}$, $f_{D_s}$, and $f_{K^+}$, and the quark-mass ratios $m_c/m_s$ and $m_s/m_l$ in unquenched lattice QCD using the experimentally determined value of $f_{\pi^+}$ for normalization. We use the MILC Highly Improved Staggered Quark (HISQ) ensembles with four dynamical quark flavors --- up, down, strange, and charm --- and with both physical and unphysical values of the light sea-quark masses. The use of physical pions removes the need for a chiral extrapolation, thereby eliminating a significant source of uncertainty in previous calculations. Four different lattice spacings ranging from $a\approx 0.06$ fm to $0.15$ fm are included in the analysis to control the extrapolation to the continuum limit. Our primary results are $f_{D^+} = 212.6(0.4)({}^{+1.0}_{-1.2})\ \mathrm{MeV}$, $f_{D_s} = 249.0(0.3)({}^{+1.1}_{-1.5})\ \mathrm{MeV}$, and $f_{D_s}/f_{D^+} = 1.1712(10)({}^{+29}_{-32})$, where the errors are statistical and total systematic, respectively. The errors on our results for the charm decay constants and their ratio are approximately two to four times smaller than those of the most precise previous lattice calculations. We also obtain $f_{K^+}/f_{\pi^+} = 1.1956(10)({}^{+26}_{-18})$, updating our previous result, and determine the quark-mass ratios $m_s/m_l = 27.35(5)({}^{+10}_{-7})$ and $m_c/m_s = 11.747(19)({}^{+59}_{-43})$. When combined with experimental measurements of the decay rates, our results lead to precise determinations of the CKM matrix elements $|V_{us}| = 0.22487(51) (29)(20)(5)$, $|V_{cd}|=0.217(1) (5)(1)$ and $|V_{cs}|= 1.010(5)(18)(6)$, where the errors are from this calculation of the decay constants, the uncertainty in the experimental decay rates, structure-dependent electromagnetic corrections, and, in the case of $|V_{us}|$, the uncertainty in $|V_{ud}|$, respectively. -
##### Article: Studying Double Charm Decays of B_{u,d} and B_{s} Mesons in the MSSM with R-parity Violation

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**ABSTRACT:**Motivated by the possible large direct CP asymmetry of B{sub d}°D{sup +}D decays measured by the Belle Collaboration, we investigate double charm B{sub u,d} and B{sub s} decays in the minimal supersymmetric standard model with R-parity violation. We derive the bounds on relevant R-parity violating couplings from the current experimental data, which show quite consistent measurements among relative collaborations. Using the constrained parameter spaces, we explore R-parity violating effects on other observables in these decays, which have not been measured or have not been well measured yet. We find that the R-parity violating effects on the mixing-induced CP asymmetries of B{sub d}°D{sup (}*{sup )+}D{sup (}*{sup )-} and B{sub s}°D{sub s}{sup (}*{sup )+}D{sub s}{sup (}*{sup )-} decays could be very large; nevertheless, the R-parity violating effects on the direct CP asymmetries could not be large enough to explain the large direct CP violation of B{sub d}°D{sup +}D from Belle. Our results could be used to probe R-parity violating effects and will correlate with searches for direct R-parity violating signals in future experiments.Physical review D: Particles and fields 03/2009; 79(5):055004-055004. DOI:10.1103/PHYSREVD.79.055004 · 4.86 Impact Factor