HPLQCD · Lattice QCD Calculations in Hadron Physics
FP7 — People (Marie Curie Actions)
- Duration
- 2009-11-01 → 2012-04-30
- EU contribution
- €37,500
- Participants
- 1
- Scheme
- MC-ERG
Lines connect the coordinator with its partners.
Results in brief
Lattice QCD Calculations in Hadron Physics
The computation of nucleon form factors (FFs) and moments of parton distribution functions (PDFs). Codes to compute these quantities have been developed and tested and simulations for the relevant correlation functions have been performed. In order to perform the continuum limit extrapolation, we have used the configurations generated by the European Twisted Mass Collaboration (ETMC) with Nf = 2 dynamical light quarks at three different values of the lattice spacing, namely a ≈ 0.089 fm, a ≈ 0.070 fm and a ≈ 0.051 fm. The physical volume of the lattices is in the range L ≈ [2.1 − 2.4] fm with an additional larger volume L ≈ 2.8 fm for a ≈ 0.089 fm used to study final size effects. In order to keep fixed the physical volume, the smallest lattice spacing a ≈ 0.051 fm requires a very large number of lattice points (483 × 96) and thus the generation of gauge configurations, the inversion of quark propagators and the calculation of correlation functions become computationally very expensive. This lattice spacing is probably the smallest one available amongst all the present simulations of nucleon FFs and PDFs. In the first place we have obtained accurate results for the axial GA(Q2) and pseudo-scalar Gp(Q2) nucleon form factors as a function of the squared momentum transfer Q2 for pion masses in the range of about 260-470 MeV. For more information, see attached PDF
Data: CORDIS, © European Union
Project objective
The theory that describes interactions among elementary particles carrying the color charge (quarks and gluons) is called Quantum Chromodynamics (QCD). QCD has not been solved analytically and becomes non-perturbative at low energies. As a result, the quantitative prediction from first principles of much of its rich low-energy phenomenology remains a big challenge. Due to the lack of a coherent theoretical understanding of its various phenomena, hadron physics still represents an important testing ground for QCD and for flavor physics. An example are the recent measurements performed at JLAB which have shown that, in disagreement with the previous theoretical understanding, the electric and the magnetic elastic form factors have a substantially different behavior as function of the transfer four-momentum squared. In the so far most promising attempt to solve QCD at low energies, one discretizes the theory on space-time lattice and computes the functional integral by numerical Monte Carlo integration. Lattice QCD is the only known approach which allows ab-initio computations of non-perturbative quantities by keeping under control all the systematic errors. Recent advances in simulation algorithms now allow simulations with light sea quarks (corresponding to pion masses as small as 250 MeV) where contact with the chiral effective theory can be made. This is thus the right moment to tackle various problems of hadron physics in order to obtain the first model-independent results. With this project, we propose the use of the latest available techniques to simulate lattice QCD at small quark mass together with the chiral effective theory in order to study some subjects of particular interests for hadron physics, namely (i) the spectroscopy of ground and excited baryon (octet and decuplet) states, (ii) hadron-hadron scattering lengths, (iii) the investigation of baryon structure through form factors, parton distribution functions and generalized parton distributions.
Original text from CORDIS.
Participants
- CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS · ParisCoordinatorFrance
Links
Data: CORDIS, © European Union