Lattice QCD Topology Further Refines Axion Mass Range

by Tommy on 9/05/2017

https://arxiv.org/abs/1705.01847

Topology (and axion’s properties) from lattice QCD with a dynamical charm, Florian Burger, Ernst-Michael Ilgenfritz, Maria Paola Lombardo, Michael Müller-Preussker and Anton Trunin, Proceedings of Quark Matter 2017 – XXVI International Conference on Ultrarelativistic Heavy-ion Collisions, February 5-11, 2017, Chicago IL (4 May 2017)

We present results on QCD with four dynamical flavors in the temperature range 0.9 ≲ T/Tc ≲ 2. We have performed lattice simulations with Wilson fermions at maximal twist and measured the topological charge with gluonic and fermionic methods. The topological charge distribution is studied by means of its cumulants, which encode relevant properties of the QCD axion, a plausible Dark Matter candidate. The topological susceptibility measured with the fermionic method exhibits a power-law decay for T/Tc ≳ 2, with an exponent close to the one predicted by the Dilute Instanton Gas Approximation (DIGA). Close to Tc the temperature dependent effective exponent approaches the DIGA result from above, in agreement with recent analytic calculations. These results constrain the axion window, once an assumption on the fraction of axions contributing to Dark Matter is made.

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