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Charmed baryon spectroscopy on the physical point in 2+1 flavor lattice QCD

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 نشر من قبل Yusuke Namekawa
 تاريخ النشر 2012
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 تأليف Y. Namekawa




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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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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 tuned to their physical values, reweighted from those employed in the configuration generation. At the physical point, the inverse lattice spacing determined from the $Omega$ baryon mass gives $a^{-1}=2.194(10)$ GeV, and thus the spatial extent becomes $L = 32 a = 2.88(1)$ fm. Our results for the charmed baryon masses are consistent with experimental values, except for the mass of $Xi_{cc}$, which has been measured by only one experimental group so far and has not been confirmed yet by others. In addition, we report values of other doubly and triply charmed baryon masses, which have never been measured experimentally.
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 toge ther 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.
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We calculate the low-lying spectrum of charmed baryons in lattice QCD on the $32^3times64$, $N_f=2+1$ PACS-CS gauge configurations at the almost physical pion mass of $sim 156$ MeV/c$^2$. By employing a set of interpolating operators with different D irac structures and quark-field smearings for the variational analysis, we extract the ground and first few excited states of the spin-$1/2$ and spin-$3/2$, singly-, doubly-, and triply-charmed baryons. Additionally, we study the $Xi_c$-$Xi_c^prime$ mixing and the operator dependence of the excited states in a variational approach. We identify several states that lie close to the experimentally observed excited states of the $Sigma_c$, $Xi_c$ and $Omega_c$ baryons, including some of the $Xi_c$ states recently reported by LHCb. Our results for the doubly- and triply-charmed baryons are suggestive for future experiments.
321 - Y. Namekawa 2011
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 rel ativistic 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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