The USQCD BSM ("USBSM") community is composed of members of USQCD who are using lattice gauge theory to study strongly-coupled physics beyond the standard model on leadership-class machines.
Our current project studies SU(3) lattice gauge theory with eight nearly massless fermions in the fundamental representation. Through the Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program of the U.S. Department of Energy, we are currently generating 323x64, 483x96 and 643x128 configurations on the "Intrepid" Blue Gene/P system at the Argonne Leadership Computing Facility.
These ensembles, featuring larger volumes and lighter masses than obtained previously, are being used to calculate many physically interesting quantities including the light hadron spectrum, static quark potential, Dirac eigenvalues, running gauge couplings, glueballs, precision electroweak observables and other low-energy coefficients of the electroweak chiral lagrangian. Some initial results have appeared in arXiv:1310.7006.
In coming years we will diversify by pursuing three complementary lines of investigation, corresponding to the research directions presented in the 2013 USQCD White Paper Lattice Gauge Theories at the Energy Frontier. Using the Cray XK7 "Titan" supercomputer at the Oak Ridge Leadership Computing Facility, we will study whether a light composite Higgs particle can emerge in the near-conformal SU(3) lattice gauge theory with two nearly massless fermions in the two-index symmetric ("sextet") representation. On the "Mira" Blue Gene/Q supercomputer at Argonne, we will study supersymmetry on the lattice, beginning with investigations of N=1 supersymmetric Yang–Mills (SYM) theory utilizing SU(2) domain wall fermions. Finally, we are developing code for SU(2) gauge theory with two fundamental fermions, which we will use to study the composite Higgs that appears as a pseudo Nambu–Goldstone boson of chiral symmetry breaking.
Participants in USBSM are asked to join the "latticebsm" email list managed by . We hold occasional conference calls, informal notes from which are distributed for those unable to participate. Additional information is often posted here.
We used MIMD Lattice Computation (MILC) Collaboration software during the initial stages of our current project. Eight-fermion calculations require a much stronger bare coupling than lattice QCD, and we discovered that at such strong bare coupling the Highly Improved Staggered Quark action that we originally used is much more computationally expensive than we anticipated. To address this, we have switched to nHYP-smeared staggered fermions, and incorporated this action into the new QHMC (a.k.a. FUEL) framework that we are helping to develop. While QHMC is built on the standard USQCD software libraries, it remains under active development.
Our primary eight-flavor SU(3) production runs use overlapping ranges of fermion masses on 163x32, 243x48, 323x64, 483x96 and 643x128 lattice volumes. (483x96 and 643x128 ensembles are not yet complete.) Our saved configurations are available to any USQCD member .
Last modified 30 October 2013 by