Matching the Hagedorn mass spectrum with lattice QCD results

Abstract

Based on recent lattice QCD (LQCD) results obtained at finite temperature, we discuss modeling of the hadronic phase of QCD in the framework of hadron resonance gas (HRG) with discrete and continuous mass spectra. We focus on fluctuations of conserved charges, and show how a common limiting temperature can be used to constrain the Hagedorn exponential mass spectrum in different sectors of quantum number, through a matching of HRG and LQCD. For strange baryons, the extracted spectra are found to be consistent with all known and expected states listed by the Particle Data Group (PDG). The strange-mesonic sector, however, requires additional states in the intermediate mass range beyond that embodied in the database.

An estimate of the bulk viscosity of the hadronic medium

“…(ii) By including the Hagedorn density of states (HDS) [35,36] for counting the resonances at higher temperatures in estimating the bulk viscosity [37]. For this purpose we have used the following mass spectrum in evaluating relevant thermodynamic quantities:…”

Melting hadrons, boiling quarks

“…2 the two fits show a common value of T H around 150-170 MeV. A very recent lattice motivated effort assumes differing shape of the pre-exponential function for different families of particles [46], and uses a common, but assumed, not fitted, value of T H .…”

“…However, we note two studies [45,46] of differentiated (meson vs. baryon) hadron mass spectrum done in the way that we consider correct: using a common singularity, that is one and the same exponential T H , but "family" dependent pre-exponential functions obtained in projection on the appropriate quantum number. It should be noted that the hadronic volume V h enters any reduction of the mass spectrum by the projection method, see ref.…”

Thermalization in a small hadron gas system and high-multiplicity pp events

“…An ideal HRG, formulated with discrete mass spectrum of * Electronic address: prem@vecc.gov.in identified hadrons and resonances, has been reinforced with the ab-initio confirmation [13][14][15][16] from the LQCD. Also, as yet unmeasured higher-mass hadron states, provided by the exponentially growing continuum mass spectrum, proposed [17] by R. Hagedorn, have important contribution to the equation of state (EoS) [18][19][20] below the critical temperature (T c ) for the QCD change of phase.…”