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Lattice QCD and Hadron Physics Focus Group
Coordinator : 章文箴教授(Prof. Wen-Chen, Chang(AS))
Committee members :高崇文教授(Prof.Chung-Wen Kao(CYCU)), 林及仁教授(Prof. David Chi-Jen Lin (NCTU)), 陳俊瑋教授 (Prof.Jiunn-Wei Chen (NTU)), 劉承邦教授(Prof. Cheng-Pang Liu (NDHU)), 江府峻教授 (Prof. Fu-Jiun Jiang (NTNU)), 章文箴教授(Prof. Wen-Chen, Chang(AS))
Brief Description (請點選以下項目)
Members | Highlights | Visitors | Activities | Publications | Collaborations
A. Lattice QCD
(a) Large-scale simulations of unquenched lattice QCD with optimal domain-wall quarks:
The TWQCD collaboration led by Ting-Wai Chiu has made a breakthrough in applying the new GPU technology in large scale computing. It is the first group around the world to use a GPU cluster with sustained 36 Teraflops to perform large-scale LQCD simulations, and is one of the three groups (together with RBC/UKQCD, JLQCD) that can perform large scale unquenched simulations of lattice QCD with exact chiral symmetry. TWQCD is now writing up papers on the physical results of 2-flavor QCD, in particular, the topological susceptibility, and the pion mass and decay constant.
(b) New strong interactions at TeV scale:
In the last few years, Chi-Jen David Lin has established collaboration with an Osaka University group of led by Professor Tetsuya Onogi on walking technicolour scenario. It is a popular possibility for dynamical electroweak symmetry breaking in which flavour-changing neutral current processes are suppressed naturally (dynamically). Presently, many researchers are looking for candidate strongly-coupled gauge theories for this scenario, which requires a quasi non-trivial infrared fixed point. From our simulations, we have evidence that SU(3) gauge theory with 12 flavours develops such a fixed point.
(c) Higgs-Yukawa system on the lattice:
Chi-Jen David Lin started collaboration with the Zeuthen group led by Karl Jansen on lattice simulations for the Higgs-Yukawa system. This is also part of the recently approved Academic Summit Project led by George W.-S. Hou at National Taiwan University. The goal of this programme is to study the spectrum and symmetry breaking pattern in the presence of large Yukawa couplings in the scalar-fermion system. In addition to further the understanding of such field theories in the strong coupling regime, this project will have impact on particle physics phenomenology of extra generations of fermions beyond the Standard Model.
(d) Physics related to the LHC-b program:
Chi-Jen David Lin has collaboration with colleagues in the US and the UK on the physics related to the LHC-b program which would allow us to probe the possible right-handed coupling structure in physics beyond the Standard Model. Presently, we already calculated the spectrum of baryon containing one b quark and found it consistent with experiment. Calculations for relevant matrix elements are being performed.
(e) Top Cited Articles:
Five focus group articles were ranked “Top Cited Articles” during 2009 in “hep-lat: The 400 most highly cited papers during 2009 in the hep-lat archive”:
(a) Ranked 74: “Convergence of the chiral expansion in two-flavor lattice QCD”, JLQCD and TWQCD Collaborations (J. Noaki et al.), Phys. Rev. Lett.101: 202004, 2008
(b) Ranked 146: “Two-flavor lattice QCD simulation in the epsilon-regime with exact chiral symmetry”, JLQCD Collaboration (H. Fukaya et al.), Phys. Rev. Lett. 98: 172001, 2007
(c) Ranked 170: “Two-flavor lattice QCD in the epsilon-regime and chiral Random Matrix Theory”, Fukaya, Aoki, Chiu, Hashimoto, Kaneko, Matsufuru, Noaki, Ogawa, Onogi, Yamada, Phys. Rev. D76: 054503, 2007
(d) Ranked 211: “Topological susceptibility in two-flavor lattice QCD with exact chiral symmetry”, JLQCD and TWQCD Collaborations, Phys. Lett. B665: 294, 2008
(e) Ranked 241:“Universality of mixed action extrapolation formulae”, Chen, O'Connell and Walker-Loud, JHEP 0904:090,2009.
B. 10 Year Review of the Solar Fusion Cross Sections
Jiunn-Wei Chen has been a working group leader at the Solar Fusion II Workshop (Solar Fusion Cross Sections for the pp chain and CNO cycle, January 2009, Seattle). The output of the workshop is the review article “Solar fusion cross sections II: the pp chain and CNO cycles” by E.G. Adelberger, J.W. Chen, et al., arXiv:1004.2318 [nucl-ex] which was submitted to Rev. Mod. Phys. The previous review (suggested by John Bahcall) was published in 1998 with more than 250 citations so far.
C. Extraction of the strangeness of the proton
In the last few years, Chung Wen Kao has initiated a series of the extraction of the strangeness of the proton to include state of the art “box diagram” contributions. In their previous work “The Two-Photon-Exchange and gamma Z-Exchange Corrections to parity-Violating Elastic Electron-Proton Scattering’’, Phys. Rev. Lett .99:262001,2007, CWK and collaborators challenged the widely used approximation of the box diagrams by evaluating directly the two-boson exchange effects in a hadronic model and in a partonic model. Their result shows that the two-boson exchange effects have complicated dependence on the kinematics variables and therefore should not be approximated as a constant as previous analysis did. This discovery has a wide impact on precision measurements where theoretical radiative corrections are critical for data interpretation. They have estimated this effect on the extracted value of the proton strangeness recently and are finishing up a state of the art analysis on this quantity.
D. Former postdocs obtained faculty jobs:
Eiji Nakano and Seung-il Nam obtained faculty jobs in Kochi Univ., Japan and Korea Aerospace University, Korea, respectively. They both reported to their new jobs this year.
E. Former student/assistant admitted to Stanford:
Ting-Wai Chiu’s former student/assistant Yao-Yuan Mao was admitted to top universities such as Harvard, Stanford, and Berkeley. He is now working on his Ph.D in high energy theory at Stanford.