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Tung-Han Hsieh

Publications and source records attributed to Tung-Han Hsieh.

At least 37 records · Page 2Linked to original sources
arXiv2006

The spectrum of charmonium-like vector mesons in lattice QCD

We present the first lattice results of the spectrum of exotic vector mesons extracted from the molecular and diquark-antidiquark operators, with quark fields c-q-cbar-qbar, and c-s-cbar-qbar (c-q-cbar-sbar) respectively, in lattice QCD with exact chiral symmetry. Our results suggest that X(3872) and Y(4260) are in the spectrum of QCD, with J^{PC} = 1^{++} and 1^{--} respectively. Moreover, we obtain the spectrum of heavier exotic mesons with c-s-cbar-ubar (c-u-cbar-sbar), c-s-cbar-dbar (c-d-cbar-sbar), c-s-cbar-sbar, and c-c-cbar-cbar, as the first theoretical predictions from lattice QCD.

hep-lat↗
arXiv2006

X(3872) in lattice QCD with exact chiral symmetry

We investigate the mass spectrum of $ 1^{++} $ exotic mesons with quark content $ (\c\q\cbar\qbar) $, using molecular and diquark-antidiquark operators, in quenched lattice QCD with exact chiral symmetry. For the molecular operator $ \{(\qbarγ_i\c)(\cbarγ_5\q)- (\cbarγ_i\q)(\qbarγ_5\c) \} $ and the diquark-antidiquark operator $ \{(\q^T C \gi \c)(\qbar C γ_5 \cbar^T)-(\qbar C \gi^T \cbar^T)(\q^T C γ_5 \c) \} $, both detect a resonance with mass around $ 3890 \pm 30 $ MeV in the limit $ m_q \to m_u $, which is naturally identified with $ X(3872) $. Further, heavier exotic meson resonance with $ J^{PC} = 1^{++} $ is also detected, with quark content $ (\c\s\cbar\sbar) $ around $ 4100 \pm 50 $ MeV.

hep-ph↗
arXiv2006

Pseudovector meson with strangeness and closed-charm

We investigate the mass spectrum of 1^{+} exotic mesons with quark content (\c\s\cbar\qbar) or (\c\q\cbar\sbar), using molecular and diquark-antidiquark operators, in quenched lattice QCD with exact chiral symmetry. For the molecular operator {(\qbarγ_i\c)(\cbarγ_5\s)-(\cbarγ_i\s)(\qbarγ_5\c)} and the diquark-antidiquark operator {(\q^T C γ_i \c)(\sbar C γ_5 \cbar^T)- (\q^T C γ_5 \c)(\sbar C γ_i^T \cbar^T)}, both detect a 1^{+} resonance with mass around 4010 +- 50 MeV in the limit m_q -> m_{u,d}.

hep-lat↗
arXiv2006

Y(4260) on the lattice

We investigate the mass spectra of closed-charm mesons with $ J^{PC} = 1^{--} $, for hybrid charmonium, molecules, and diquark-antidiquark operators, in quenched lattice QCD with exact chiral symmetry. For two lattice volumes $ 24^3 \times 48 $ and $ 20^3 \times 40 $, each of 100 gauge configurations generated with single-plaquette action at $ β= 6.1 $, we compute point-to-point quark propagators and measure the time-correlation functions of these exotic meson operators. For the molecular operator $ \{(\qbarγ_5γ_i\c)(\cbarγ_5\q)- (\cbarγ_5γ_i\q)(\qbarγ_5\c) \} $, it detects a resonance with mass around $ 4238 \pm 31 $ MeV, which is naturally identified with $ Y(4260) $. Further, for any molecular and diquark-antidiquark operator, it detects heavier exotic charmed mesons, with quark content $ (\c\s\cbar\sbar) $ around $ 4450 \pm 100 $ MeV, and $ (\c\c\cbar\cbar) $ around $ 6400 \pm 50 $ MeV.

hep-lat↗
arXiv2005

Pseudoscalar Mass and Decay Constant in Lattice QCD with Exact Chiral Symmetry

The masses and decay constants of pseudoscalar mesons $ D $, $ D_s $, and $ K $ are determined in quenched lattice QCD with exact chiral symmetry. For 100 gauge configurations generated with single-plaquette action at $ β= 6.1 $ on the $ 20^3 \times 40 $ lattice, we compute point-to-point quark propagators for 30 quark masses in the range $ 0.03 \le m_q a \le 0.80 $, and measure the time-correlation functions of pseudoscalar and vector mesons. The inverse lattice spacing $ a^{-1} $ is determined with the experimental input of $ f_π$, while the strange quark bare mass ($ m_s a = 0.08 $), and the charm quark bare mass ($ m_c a = 0.80 $) are fixed such that the masses of the corresponding vector mesons are in good agreement with $ ϕ(1020) $ and $ J/ψ(3097) $ respectively. Our results of pseudoscalar-meson decay constant are: $ f_K = 152(6)(10) $ MeV, $ f_D = 235(8)(14)$ MeV, and $ f_{D_s} = 266(10)(18) $ MeV [hep-ph/0506266]. The latest experimental result of $ f_{D^+} $ from CLEO [hep-ex/0508057] is in good agreement with our prediction.

hep-lat↗
arXiv2005

Mass Spectra of Pentaquarks -- Overlap versus Wilson Fermions

We investigate the mass spectra of $Θ^+(udud\bar s)$ in quenched lattice QCD, with overlap and Wilson fermions respectively. Using three different interpolating operators, we measure their correlation matrix, and extract the mass spectra in even and odd parity channels, for 100 gauge configurations generated with single plaquette action at $β=6.1$ on the $20^3 \times 40$ lattice. The lowest $ 1/2^- $ state agrees with the $ KN $ s-wave scattering state, for both fermion schemes. On the other hand, for the lowest $ 1/2^+ $ state, it is different from any hadron scattering states for the overlap fermion, while it seems to agree with $ KN^* $ s-wave for the Wilson fermion.

hep-lat↗
arXiv2005

Study of $ Theta^+(udud \bar s) $ in lattice QCD with exact chiral symmetry

We investigate the mass spectrum of the pentaquark baryon ($ udud \bar s $) in quenched lattice QCD with exact chiral symmetry. Using 3 different interpolating operators for $ Θ$, we measure the $ 3 \times 3 $ correlation matrix and obtain the eigenvalues $ A^{\pm} (t) $ with $ \pm $ parity, for 100 gauge configurations generated with Wilson gauge action at $ β= 6.1 $ on the $ 20^3 \times 40 $ lattice. For the lowest-lying $ J^P = 1/2^- $ state, its mass is almost identical to that of the KN S-wave, while for the lowest-lying $ J^P = 1/2^+ $ state, its mass is smaller than that of the KN P-wave, especially for the regime $ m_u < m_s $. By chiral extrapolation (linear in $m_π^2$) to $ m_π= 135 $ MeV, we obtain the masses of the lowest-lying states: $ m(1/2^-) = 1424(57) $ MeV and $ m(1/2^+) = 1562(121) $ MeV, in agreement with the masses of $ m_K + m_N \simeq 1430 $ MeV and $ Θ^+(1540) $ respectively.

hep-ph↗
arXiv2005

Pseudoscalar Decay Constants $ f_{D} $ and $ f_{D_s} $ in Lattice QCD with Exact Chiral Symmetry

We determine the masses and decay constants of pseudoscalar mesons $ D $, $ D_s $, and $ K $ in quenched lattice QCD with exact chiral symmetry. For 100 gauge configurations generated with single-plaquette action at $ β= 6.1 $ on the $ 20^3 \times 40 $ lattice, we compute point-to-point quark propagators for 30 quark masses in the range $ 0.03 \le m_q a \le 0.80 $, and measure the time-correlation functions of pseudoscalar and vector mesons. The inverse lattice spacing $ a^{-1} $ is determined with the experimental input of $ f_π$, while the strange quark bare mass $ m_s a = 0.08 $, and the charm quark bare mass $ m_c a = 0.80 $ are fixed such that the masses of the corresponding vector mesons are in good agreement with $ ϕ(1020) $ and $ J/ψ(3097) $ respectively. Our results of pseudoscalar-meson decay constants are $ f_K = 152(6)(10) $ MeV, $ f_D = 235(8)(14)$ MeV, and $ f_{D_s} = 266(10)(18) $ MeV.

hep-ph↗
arXiv2005

Signal of Theta^+ in quenched lattice QCD with exact chiral symmetry

We investigate the mass spectrum of the pentaquark baryon ($ udud \bar s $) in quenched lattice QCD with exact chiral symmetry. Using 3 different interpolating operators, we measure their $ 3 \times 3 $ correlation matrix and obtain the eigenvalues $ A^{\pm} (t) $ with $ \pm $ parity, for 100 gauge configurations generated with Wilson gauge action at $ β= 6.1 $ on the $ 20^3 \times 40 $ lattice. For the lowest-lying $ J^P = 1/2^- $ state, its effective mass is almost identical to that of the KN s-wave, while for the lowest-lying $ J^P = 1/2^+ $ state, its effective mass is smaller than that of the KN p-wave, especially for the regime $ m_u < m_s $. By chiral extrapolation (linear in $m_π^2$) to $ m_π= 135 $ MeV, we obatin the masses of the lowest-lying states: $ m(1/2^-) = 1424(57) $ MeV and $ m(1/2^+) = 1562(121) $ MeV, in agreement with the masses of $ m_K + m_N \simeq 1430 $ MeV and $ Θ^+(1540) $ respectively.

hep-ph↗
arXiv2005

Baryon Masses in Lattice QCD with Exact Chiral Symmetry

We investigate the baryon mass spectrum in quenched lattice QCD with exact chiral symmetry. For 100 gauge configurations generated with Wilson gauge action at $ β= 6.1 $ on the $ 20^3 \times 40 $ lattice, we compute (point-to-point) quark propagators for 30 quark masses in the range $ 67 {MeV} \le m_q \le 1790 {MeV} $. For baryons only composed of strange and charm quarks, their masses are extracted directly from the time correlation functions, while for those containing $ u (d) $ light quarks, their masses are obtained by chiral extrapolation to $ m_π= 135 $ MeV. Our results of baryon masses are in good agreement with experimental values, except for the negative parity states of $ Λ$ and $ Λ_c $. Further, our results of charmed (including doubly-charmed and triply-charmed) baryons can serve as predictions of QCD.

hep-lat↗
arXiv2004

N(N*) and Delta(Delta*) on the lattice

We investigate the mass spectrum of Nucleon and Delta (and its counterparts with strange and charm), and their excited states, in quenched lattice QCD with exact chiral symmetry. For each light baryon, we use 23 masses to determine the coefficients of the mass formula in quenched chiral perturbation theory. By chiral extrapolation to m_π=135 MeV, we obtain M_N=958(26) MeV, M_{N*}=1553(42) MeV, M_{Delta}=1216(32) MeV and M_{Delta*}=1611(17) MeV, which are identified with N(939)P_{11},N(1535)S_{11}, Delta(1232)P_{33} and Delta(1620)S_{31} respectively. Further, we directly measure the masses of Omega^{-}, M_{Omega}=1648(60) MeV, and its excited state, M_{Omega*}=1935(48) MeV; as well as the triply charmed baryon Omega_{ccc}^{++}, M_{Omega_{ccc}^{++}}=4931(22) MeV, and its excited state, M_{{Ω^{++}_{ccc}}^*}=5185(35) MeV.

hep-lat↗
arXiv2003

A Linux PC cluster for lattice QCD with exact chiral symmetry

A computational system for lattice QCD with exact chiral symmetry is described. The platform is a home-made Linux PC cluster, built with off-the-shelf components. At present this system constitutes of 64 nodes, with each node consisting of one Pentium 4 processor (1.6/2.0/2.5 GHz), one Gbyte of PC800/PC1066 RDRAM, one 40/80/120 Gbyte hard disk, and a network card. The computationally intensive parts of our program are written in SSE2 codes. The speed of this system is estimated to be 70 Gflops, and its price/performance is better than $1.0/Mflops for 64-bit (double precision) computations in quenched QCD. We discuss how to optimize its hardware and software for computing quark propagators via the overlap Dirac operator.

hep-lat↗
arXiv2003

A note on Neuberger's double pass algorithm

We analyze Neuberger's double pass algorithm for the matrix-vector multiplication R(H).Y (where R(H) is (n-1,n)-th degree rational polynomial of positive definite operator H), and show that the number of floating point operations is independent of the degree n, provided that the number of sites is much larger than the number of iterations in the conjugate gradient. This implies that the matrix-vector product $ (H)^{-1/2} Y \simeq R^{(n-1,n)}(H) \cdot Y $ can be approximated to very high precision with sufficiently large n, without noticeably extra costs. Further, we show that there exists a threshold $ n_T $ such that the double pass is faster than the single pass for $ n > n_T $, where $ n_T \simeq 12 - 25 $ for most platforms.

hep-lat↗
arXiv2003

Light quark masses, chiral condensate and quark-gluon condensate in quenched lattice QCD with exact chiral symmetry

We determine several quantities in quenched lattice QCD with exact chiral symmetry. For 100 gauge configurations generated with Wilson gauge action at $ β= 6.0 $ on the $ 16^3 \times 32 $ lattice, we compute quenched quark propagators for 13 bare quark masses. The pion decay constant is extracted from the pion propagator, and from which the inverse lattice spacing is determined to be $ a^{-1} = 1.979(6) $ GeV. The parameters ($ C, δ, B $) in the pseudoscalar meson mass formula in quenched chiral perturbation theory (q$χ$PT) to one-loop order are determined. Further, we measure the index (topological) susceptibility of these 100 gauge configurations, $ χ_t = (175 \pm 6 {MeV})^4 $, from which we obtain an estimate of the mass of $ η' $ in q$χ$PT, and the coefficient of quenched chiral logarithm, both in good agreement with the values determined from the pion masses, as well as with the theoretical estimates. With our values of $ C, δ, B $, the experimental inputs of pion and kaon masses, and the pion decay constant, we determine the light quark masses: $ m_{u,d} = 4.1 \pm 0.3 $ MeV, and $ m_s = 92 \pm 9 $ MeV, in the $ \bar{MS} $ scheme at scale $ μ= 2 $ GeV. Also, we determine the quark condensate $<\bar q q > = -(250 \pm 3 {MeV})^3 $, and the quark-gluon condensate $ g < \bar q σ_{μν} F_{μν} q > = -(434 \pm 4 {MeV})^5 $, in the $ \bar{MS} $ scheme at scale 2 GeV.

hep-lat↗
arXiv2002

A computational system for lattice QCD with overlap Dirac quarks

We outline the essential features of a Linux PC cluster which is now being developed at National Taiwan University, and discuss how to optimize its hardware and software for lattice QCD with overlap Dirac quarks. At present, the cluster constitutes of 30 nodes, with each node consisting of one Pentium 4 processor (1.6/2.0 GHz), one Gbyte of PC800 RDRAM, one 40/80 Gbyte hard disk, and a network card. The speed of this system is estimated to be 30 Gflops, and its price/performance ratio is better than $1.0/Mflops for 64-bit (double precision) computations in quenched lattice QCD with overlap Dirac quarks.

hep-lat↗
arXiv2002

A note on Zolotarev optimal rational approximation for the overlap Dirac operator

We discuss the salient features of Zolotarev optimal rational approximation for the inverse square root function, in particular, for its applications in lattice QCD with overlap Dirac quark. The theoretical error bound for the matrix-vector multiplication $ H_w (H_w^2)^{-1/2}Y $ is derived. We check that the error bound is always satisfied amply, for any QCD gauge configurations we have tested. An empirical formula for the error bound is determined, together with its numerical values (by evaluating elliptic functions) listed in Table 2 as well as plotted in Figure 3. Our results suggest that with Zolotarev approximation to $ (H_w^2)^{-1/2} $, one can practically preserve the exact chiral symmetry of the overlap Dirac operator to very high precision, for any gauge configurations on a finite lattice.

hep-lat↗
arXiv2002

Quenched chiral logarithms in lattice QCD with overlap Dirac quarks

We examine quenched chiral logarithms in lattice QCD with overlap Dirac quarks. From our data of m_pi^2, we determine the coefficient of quenched chiral logarithm delta = 0.203(14), 0.176(17), 0.193(17) and 0.200(13) for lattices of sizes 8^3 times 24, 10^3 times 24, 12^3 times 24 and 16^3 times 32 respectively. Also, for the first three lattice sizes, we measure the index susceptibility of the overlap Dirac operator, and use the exact relation between the index susceptibility and the eta' mass in quenched chiral perturbation theory to obtain an independent determination of delta = 0.198(27), 0.173(24), 0.169(22), which are in good agreement with those determined from m_pi^2.

hep-lat↗