New results with colour-sextet quarks.
- High Energy Physics
We study QCD with 2 and 3 flavours of colour-sextet quarks. The 2-flavour theory is a candidate Walking Technicolor theory. Since we are attempting to distinguish whether this theory is walking or conformal, we also study the 3-flavour theory, which is believed to be conformal, for comparison. We simulate lattice QCD with 2 and 3 flavours of colour-sextet staggered quarks at finite temperatures to determine the scales of confinement and chiral-symmetry breaking from the positions of the deconfinement and chiral-symmetry restoration transitions. Unlike the case with fundamental quarks, these transitions are far apart. For 2 flavours the values of {beta} = 6/g{sup 2} for both transitions increase as Ta is decreased from 1/4 to 1/6 to 1/8, as expected for a theory whose coupling runs to smaller values as the lattice spacing is decreased. However, for the chiral transition, the increase in {beta} between Ta = 1/4 and Ta = 1/6 is much larger than the increase between Ta = 1/6 and Ta = 1/8. This suggests that between Ta = 1/4 and Ta = 1/6 we are at strong coupling where the theory is effectively quenched, while between Ta = 1/6 and Ta = 1/8 we are emerging into the weak coupling regime. It will require even smaller Ta values to determine whether the running of the chiral-transition coupling is controlled by asymptotic freedom and the theory walks, or if it reaches a non-zero limit when the transition becomes a bulk transition and the theory is conformal. The 3 flavour case at Ta = 1/4 and Ta = 1/6 behaves similarly to the 2 flavour case. Since this theory is expected to be conformal, the interpretation that we are seeing strong-coupling behaviour, inaccessible from the weak-coupling limit (continuum) is the most likely interpretation.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); JTI Grant
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 1007398
- Report Number(s):
- ANL-HEP-CP-10-42; TRN: US1101314
- Journal Information:
- PoS, Journal Issue: 2010; Conference: 28th International Symposium on Lattice Field Theory (LATTICE 2010); Jun. 14, 2010 - Jun. 19, 2010; Villasimius, Italy
- Country of Publication:
- United States
- Language:
- ENGLISH
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Thermodynamics of lattice QCD with 2 flavors of color-sextet quarks: A model of walking/conformal technicolor
Thermodynamics of lattice QCD with 2 flavours of color-sextet quarks : a model of walking/conformal technicolor.