Quarkonium Spectra at Finite Temperature from QCD Sum Rules and MEM

Abstract

See More

In this chapter, we will discuss a system for which the MEM technique will play an essential role for extracting meaningful information from the sum rules. This is so because, we have in principle no established information on the spectral functions of quarkonia at finite temperature, in contrast to the zero temperature case or the channels investigated in the last two chapters, for which we had at hand experimental information on the existence of the lowest few peaks showing up in the spectral functions. At finite temperature the peaks representing bound states or resonances will, however, inevitably vanish at a certain temperature and a smooth continuum corresponding to weakly interacting quarks will appear instead. At present, we do not know at what temperature this will happen and therefore should better not introduce any strong assumption on the form of the spectral function into the analysis. MEM is the method of choice for such a problem as it extracts the spectral function directly from the sum rules. This chapter is partly based on Gubler et al. (Nucl Phys A897:28, 2013)