NSF Key Project and Recent Progress of Lattice QCD in China

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NSF Key Project and Recent Progress of Lattice
QCD in China

• Xiang-Qian Luo

Zhongshan (Sun Yat-Sen) University, Guangzhou,
China stslxq_at_zsu.edu.cn http//
qomolangma.zsu.edu.cn
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• Chinese physicists have been involved in the
  study of lattice gauge theory since early 80's.
• Institute of High Energy Physics, Beijing
• Institute of Theoretical Physics, Beijing
• Peking Uniniversity, Beijing
• Nankai University, Tianjin
• Sichuan University, Chengdu
• Zhejiang University, Huangzhou
• Zhongshan University, Guangzhou

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• Beijing
• Tianjin
• Chengdu
• Huangzhou
• Guangzhou

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• Most investigations in 80s were analytical, due
  to limited computational facilities.
• For review, Guo and Luo, hep-lat/9706017.
• Thanks to (1) rapid development of high
  performance supercomputers in China in late 90's,
• (2) success of the Symanzik improvement program,
• (3) support from NSF (National Science
  Foundation),
• more and more Chinese physicists do numerical
  simulations.

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• Top 500 Supercomputers in the world, 2002

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• Top 50 supercomputers in China, 2002

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Dawning 3000
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• Dawning 3000
• 128 nodes
• Rmax 279.60Gflops
• Rpeak 403.2Gflops
• Memory 168GB
• Disk 3.63TB?
• CPU Power3-II,
• Network 2D Mesh or Myrinet
• Operating system IBM AIX

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• DeepComp 1800

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• Legend GroupDeepComp 1800 - P4 Xeon 2 GHz -
  Myrinet/ 512CPU (NODES)
• Rmax1.046 TflopsRpeak 2.048 Tflops
• Location Beijing, China
• Number 43 of top 500 supercomputers 2002
• The 3rd fastest in Asia?
• http//www.top500.org/lists/2002/11/

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• Zhongshan U. self-made PC cluster, 2000

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NSFC National Science Foundation Committee
established in 1986 an organization directly
affiliated to the State Council for the
management of the National Natural Science Fund.
General project 100K yuan for 3 years. (1
Yuan1/8USD) NSF project for distinguished young
scientists 80M yuan for 4 years. Key NSF
project 100M yuan for 4 years
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• Approved NSF Funds in China

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• These years, the Chinese lattice physicists
  received a lot of supports from NSFC and other
  sources
• T.L. Chen, Nankai U., General project, 100K yuan
• S.H. Guo, Zhongshan U., Guangzhou, General
  project, 100K yuan
• C. Liu, Peking U., Beijing, General project,
  100K yuan
• J.M. Liu, Zhongshan U., General project, 100K
  yuan
• X.Q. Luo, Zhongshan U., General project, 100K
  yuan
• J.M. Wu, IHEP, Beijing, General project, 100K
  yuan
• H.P. Ying, Zhejiang U., Huangzhou, General
  project, 100K yuan
• X.Q. Luo, Zhongshan U., NSF project for
  distinguished young scientists 80M yuan
  (1999-2002)
• X.Q. Luo, Q.Z. Chen, Y. Chen, Y.Z. Fang, S.H.
  Guo, C.Q. Huang, C. Liu, Z.H. Mei, H.P. Ying, Key
  NSF project 120M yuan (2003-2006)

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• Structure of Matter
• Quantum ChromoDynamics(QCD) theory of strong
  interactions between quarks, mediated by gluons

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? Lattice Gauge Theory (Wilson, 1974) most
reliable non-perturbative tool for strong
interactions
? Basic Ideas Continuum space-time ?
Discretized grid Derivative ? Finite difference

• a) quark field ?(x)
• b) gauge field U(x,k)

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• Advantage physical quantities can now be
  calculated by Monte Carlo simulation on a
  computer
• Disadvantage O(a) errors are large at large
  coupling g.
• To reduce the error and keep La gt diameter of the
  hadron, large volume (Lgtgt1) is needed
• It costs a lot of computer time, and high
  performance parallel computer is necessary

• L the number of lattice point in one direction

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• Improved Lattice QCD
• The most efficient way to reduce the O(a) and
  finite volume errors
• Improved scalar action (Symanzik, 1983)
• Quark action Hamber and Wu, Phys. Lett. B133
  (1983) 351.
• 
  (Sheikholeslami and Wohlert, 1985)
• Improved gluon action (Luscher, Weisz, 1984)
• Tadpole improvement (Lepage, 1996)
• Improved quark Hamiltonian
• Luo, Chen, Xu, Jiang, , Phys. Rev. D50 (1994)
  501.
• Jiang, Luo, Mei, Jirari, Kroger, Wu, Phys. Rev.
  D59 (1999) 014501.
• Improved gluon Hamiltonian
• Luo, Guo, Kroger, Schutte, Phys. Rev. D59 (1999)
  034503.

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• Algorithms
• To do numerical simulations with dynamical Wilson
  fermions
• Thron, Dong, Liu, Ying,Phys.Rev. D57 (1998) 1642
• Ying, Chin. Phys. Lett. 15 (1998) 401.
• To do numerical simulations with Kogut-Susskind
  fermions in the chiral limit
• Luo, Mod. Phys. Lett. A16 (2001) 1615.
• Which extends the following algorithm to QCD
• Azcoiti, Di Carlo, Grillo, Phys. Rev. Lett. 65
  (1990) 2239.
• Azcoiti, Laliena, Luo, Piedrafita, Di Carlo,
  Galante, Grillo, Fernandez, Vladikas, Phys. Rev.
  D48 (1993) 402.

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• To do numerical simulations with clover fermions
• Luo, Comput. Phys. Commun. 94 (1996) 119-127.
• Jansen and Liu, Comput. Phys. Commun. 99 (1997)
  221.
• To do numerical simulations with Ginsparg-Wilson
  fermions
• Liu, Nucl. Phys. B554 (1999) 313.

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• Problems of standard Langrangian Monte Carlo
  simulations
• Extremely difficult to study excited states,
• Broken done in QCD at finite density.
• Hamiltonian formulation of LGT doest encounter
  above problem.
• Monte Carlo Hamiltonian to construct effective
  Hamiltonian from standard Monte Carlo
  simulations.
• Tested in quantum mechanics
• Jirari, Kroger, Luo, Moriarty, Phys. Lett. A258
  (1999) 6.
• Luo, Jiang, Huang, Jirari, Kroger, Moriarty,
  Physica A281 (2000) 201.
• Tested in the scalar model
• Huang, Kroger, Luo, Moriarty, Phys. Lett. A299
  (2002) 483.

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Fig. 1. Energy spectrum in a low energy
window.

• Fig. 2. Free energy F. Comparison of results from
  Monte Carlo Hamiltonian (filled circles) with
  standard Lagrangian lattice calculations (open
  circles).

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• Scattering of hadrons using tadpole improved
  clover Wilson action on coarse anisotropic
  lattices
• Liu, Zhang, Chen, Ma,Nucl. Phys. B624 (2002)
  360.
• C. Liu 
•   Pion scattering length with small anisotropic
  lattices, this workshop

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• Hybrid meson

• QCD predict the existence of some new particles
• Glueball bound state of gluons
• Hybrid meson bound state of quark, anti-quark
  and gluons

• Glueball

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• Glueball Spectrum
• From Hamiltonian lattice QCD
• Luo, Q. Chen, Mod.Phys.Lett. A11 (1996) 2435.
• Nucl. Phys. B(Proc.Suppl.)53 (1997) 243.
• From Improved glunon action
• C. Liu, Chin. Phys. Lett. 18 (2001) 187.
• D. Liu, Wu, Y. Chen, High Energy Phys. Nucl.
  Phys. 26 (2002) 222.
• Mod.Phys.Lett. A17 (2002) 1419.
• Mei, Luo, 2003, in preparation.

• Quantum number JPC

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• Construct New Glueball Operators using their
  relation between lattice and continuum
• D. Liu, Wu, Y. Chen, High Energy Phys. Nucl.
  Phys. 26 (2002) 222.
• First Calculation for the Mass of the 4
  Glueball
• D. Liu, Wu, Mod.Phys.Lett. A17 (2002) 1419.

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• Mei, Luo, 2002 Glueball masses from Improved
  gluon action (compared with Morningstar, Peardon,
  1997, 1999)
• MG(0)1733MeV
• MG(2)2408MeV
• MG(1-) 2951MeV

• Glueballs can also mix with mesons, and decay (in
  progress)

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• Hybrid meson masses from QCD with improved gluon
  and quark actions on the anisotropic lattice
• Mei and Luo, hep-lat/0206012

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• At sufficiently high temperature and density,
  quarks are no longer confined
• New state of matter Quark-Gluon Plasma

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• Neutron Star

• RHIC (Relativistic Heavy Ion Collider)
• LHC (Large Hadron Collider)

• Lattice QCD at High Temperature can well be
  investigated by the standard Monte Carlo approach
• At finite density (chemical potential), standard
  action approach (Hasenfratz, Kasch, 1983) fails
  because S is complex, one can not use e-S to
  generate configurations

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• Alternative (Hamiltonian) QCD at finite chemical
  potential was solved in the strong coupling
  regime
• Gregory, Guo, Kroger, Luo, Phys. Rev. D62 (2000)
  054508.
• Luo, Gregory, Guo, Kroger, hep-ph/0011120.
• Fang, Luo, hep-lat/0210031.

• There is a first order chiral phase transition at
  ?c
• Reasonable results for the physical quantities
  are obtained,

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• Nature of the chiral phase transition?
• Rapp, Schafer, Shuryak, Velkovsky, 1998
• Alford, Rajagopal, Wilczek, 1998
• Diquark condensation in the high density phase?
• Instantons and chaos play an important role?
• There is no first principle study in SU(3).
• The definition of quantum instantons and quantum
  chaos are umbiguous.

• New Quantum Instantons and Quantum Chaos
• Jirari, Kroger, Luo, Moriarty, Rubin, Phys.
  Rev. Lett. 86 (2001) 187.

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Key Project of National Science Foundation"Large
Scale Simulations of Lattice Gauge Theory, 120M
(2003-2006)

• Xiang-Qian Luo (Director, Zhongshan U., Guangzou)
• Qi-Zhou Chen (Zhongshan U., Guangzhou)Ying Chen
  (Institute of High Energy Phys.,
  Beijing)Yi-Zhong Fang (Zhongshan U.,
  Guangzou)Shuo-Hong Guo (Zhongshan U.,
  Guangzou)Chun-Qing Huang (Zhongshan U. and
  Foshan U.)Chuan Liu (Peking U., Beijing)Da-Qing
  Liu (Institute of Theoretical Phys.,
  Beijing)Zhong-Hao Mei (Zhongshan U.,
  Guangzou)He-Ping Ying (Zhejiang U., Huangzhou)

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• We plan to do large scale simulations of lattice
  QCD, using the parallel supercomputing facilities
  in China. We will develop new numerical methods
  and study the following hot topics
• new hadrons such as glueballs and hybrid mesons,
• scattering of hadrons,
• topology of QCD vacuum,
• transition from the quark confinement phase to
  quark-gluon plasma phase,
• quantum instantons and quantum chaos.