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Register a new userCharm quark system on the physical point in 2+1 flavor lattice QCD
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Y. Namekawa
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We investigate the charm quark system on 2+1 flavor PACS-CS configurations. Calculations are performed at the lattice spacing $a^{-1}=2.194(10)$ GeV and the spatial extent $L=2.9$ fm with O(a)-improved Wilson fermions for the light quarks and the relativistic heavy fermion for the charm quark. Our dynamical $ud$ and strange quark masses and valence charm quark mass are set to their physical values. A comparison of the mass spectrum and decay constants with experiments is presented. Our results for the charm quark mass and CKM matrix elements are also reported.
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We investigate the charm quark system using the relativistic heavy quark action on 2+1 flavor PACS-CS configurations previously generated on $32^3 times 64$ lattice. The dynamical up-down and strange quark masses are set to the physical values by using the technique of reweighting to shift the quark hopping parameters from the values employed in the configuration generation. At the physical point, the lattice spacing equals $a^{-1}=2.194(10)$ GeV and the spatial extent $L=2.88(1)$ fm. The charm quark mass is determined by the spin-averaged mass of the 1S charmonium state, from which we obtain $m_{rm charm}^{msbar}(mu = m_{rm charm}^{msbar}) = 1.260(1)(6)(35)$ GeV, where the errors are due to our statistics, scale determination and renormalization factor. An additional systematic error from the heavy quark is of order $alpha_s^2 f(m_Q a)(a Lambda_{QCD})$, which is estimated to be a percent level if the factor $f(m_Q a)$ analytic in $m_Q a$ is of order unity. Our results for the charmed and charmed-strange meson decay constants are $f_D=226(6)(1)(5)$ MeV, $f_{D_s}=257(2)(1)(5)$ MeV, again up to the heavy quark errors of order $alpha_s^2 f(m_Q a)(a Lambda_{QCD})$. Combined with the CLEO values for the leptonic decay widths, these values yield $|V_{cd}| = 0.205(6)(1)(5)(9)$, $|V_{cs}| = 1.00(1)(1)(3)(3)$, where the last error is on account of the experimental uncertainty of the decay widths.
We study heavy-heavy and heavy-light quark systems for charm with a relativistic heavy quark action in 2+1 flavor lattice QCD. Configurations are generated by the PACS-CS Collaboration at the lattice spacing is $a=0.09$ fm with the lattice size of $32^3times 64$ employing the $O(a)$-improved Wilson quark action and the Iwasaki gauge action. We present preliminary results for the charmonium spectrum and the $D$ and $D_s$ meson decay constants evaluated at 3.5 MeV$< m_{rm ud}<$ 12 MeV with $m_{rm s}$ around the physical value. We investigate the dynamical quark mass dependences of the hyperfine and the orbital splittings. The decay constants are compared with the recent experimental values.
We present the results of the physical point simulation in 2+1 flavor lattice QCD with the nonperturbatively $O(a)$-improved Wilson quark action and the Iwasaki gauge action at $beta=1.9$ on a $32^3 times 64$ lattice. The physical quark masses together with the lattice spacing is determined with $m_pi$, $m_K$ and $m_Omega$ as physical inputs. There are two key algorithmic ingredients to make possible the direct simulation at the physical point: One is the mass-preconditioned domain-decomposed HMC algorithm to reduce the computational cost. The other is the reweighting technique to adjust the hopping parameters exactly to the physical point. The physics results include the hadron spectrum, the quark masses and the pseudoscalar meson decay constants. The renormalization factors are nonperturbatively evaluated with the Schr{o}dinger functional method. The results are compared with the previous ones obtained by the chiral extrapolation method.
We present the first results of the PACS-CS project which aims to simulate 2+1 flavor lattice QCD on the physical point with the nonperturbatively $O(a)$-improved Wilson quark action and the Iwasaki gauge action. Numerical simulations are carried out at the lattice spacing of $a=0.0907(13)$fm on a $32^3times 64$ lattice with the use of the DDHMC algorithm to reduce the up-down quark mass. Further algorithmic improvements make possible the simulation whose ud quark mass is as light as the physical value. The resulting PS meson masses range from 702MeV down to 156MeV, which clearly exhibit the presence of chiral logarithms. An analysis of the PS meson sector with SU(3) ChPT reveals that the NLO corrections are large at the physical strange quark mass. In order to estimate the physical ud quark mass, we employ the SU(2) chiral analysis expanding the strange quark contributions analytically around the physical strange quark mass. The SU(2) LECs ${bar l}_3$ and ${bar l}_4$ are comparable with the recent estimates by other lattice QCD calculations. We determine the physical point together with the lattice spacing employing $m_pi$, $m_K$ and $m_Omega$ as input. The hadron spectrum extrapolated to the physical point shows an agreement with the experimental values at a few % level of statistical errors, albeit there remain possible cutoff effects. We also find that our results of $f_pi=134.0(4.2)$MeV, $f_K=159.4(3.1)$MeV and $f_K/f_pi=1.189(20)$ with the perturbative renormalization factors are compatible with the experimental values. For the physical quark masses we obtain $m_{rm ud}^msbar=2.527(47)$MeV and $m_{rm s}^msbar=72.72(78)$MeV extracted from the axial-vector Ward-Takahashi identity with the perturbative renormalization factors.
We investigate the charmed baryon mass spectrum using the relativistic heavy quark action on 2+1 flavor PACS-CS configurations previously generated on $32^3 times 64$ lattice. The dynamical up-down and strange quark masses are set to the physical values by using the technique of reweighting to shift the quark hopping parameters from the values employed in the configuration generation. At the physical point, the lattice spacing equals $a^{-1}=2.194(10)$ GeV and the spatial extent $L=2.88(1)$ fm. Our results for the charmed baryon masses are consistent with experiments except for $Xi_{cc}$, which has only weak experimental evidence yet. We also predict mass values for other doubly and triply charmed baryons.
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