# Los Alamos National Laboratory

Delivering science and technology to protect our nation and promote world stability

# Lattice QCD

Understanding discoveries at the Energy, Intensity, and Cosmic Frontiers

## Lattice QCD at Los Alamos

Lattice QCD (LQCD) is a non-perturbative formulation on a discrete Eucledian space-time grid of Quantum Chromodynamics (QCD), the regnant theory of strong interactions. Large scale simulations of lattice QCD are providing increasingly precise estimates, from first principles, of many properties of QCD that are being used to both validate QCD and search for new physics beyond the standard model of elementary particles and interactions.

The Los Alamos lattice QCD group has made many pioneering contributions since its inception in 1984. Current members include Tanmoy Bhattacharya, Vicenzo Cirigliano, Michael Graesser, Rajan Gupta, Anosh Joseph (moved to DESY Zeuthen) and Boram Yoon. They are currently engaged in four projects:

- Investigations of the behavior of QCD at finite temperature to elucidate the nature of the chiral transition to the quark-gluon plasma and restoration of U(1) axial symmetry. These calculations are being done as part of the US wide HotQCD collaboration. Published papers include: Chiral transition and U(1)A symmetry restoration from lattice QCD using domain wall fermions, Fluctuations and Correlations of net baryon number, electric charge, and strangeness: A comparison of lattice QCD results with the hadron resonance gas model, Chiral and deconfinement aspects of the QCD transition and Equation of state and QCD transition at finite temperature.
- Calculations of matrix elements of iso-vector quark bilinear operators within the neutron and proton states to explore signatures of new physics (scalar and tensor interactions) at the TeV scale that will be investigated in precision measurements of [ultra]cold neutron decays. The PNDME (Precision Neutron Decay Matrix Elements) collaboration consists of Saul Cohen and Huey-wen Lin at the university of Washington and the LANL lattice QCD group. Published papers include Probing Novel Scalar and Tensor Interactions from (Ultra)Cold Neutrons to the LHC andNucleon Charges and Electromagnetic Form Factors from 2+1+1-Flavor Lattice QCD.
- Calculations of matrix elements of novel CP violating operators that arise in the effective field theory analysis of new physics at the TeV scale and could make contributions to the neutron electric dipole moment that are large enough to explain baryogenesis. These calculations are being done in collaboration with Tom Blum and Michael Abramczyk (University of Connecticut), Taku Izubuchi, Shigemi Ohta, Eigo Shintani and Amarjit Soni (BNL). Published papers include Neutron Electric Dipole Moment from Beyond the Standard Model.
- Calculations of matrix elements of light cone operators within the proton state that shed light on the contribution of the angular momentum of quarks to the proton spin. Of particular interest is the extraction of the Sivers and Boer-Mulders distribution functions. These calculations are being done in collaboration with Michael Engelhardt (NMSU), John Negele (MIT) and Andreas Schaefer (University of Regensburg, Germany).