Isothermal compressibility of hadronic matter using hagedorn mass spectrum

Abstract

A new state of nuclear matter is believed to exist at extremely high tempera- ture and/or baryonic density, where the hadronic (e.g. proton, neutron, pion etc.) degrees of freedom lose their identity and convert into soup of quarks and gluons, known as partons. Partonic degrees of freedom manifest over the nuclear volume rather than the nucleonic volume. This is seen to happen in heavy-ion collisions and possibly in hadronic (pp) collisions at the Large Hadron Collider (LHC) energies. The theory of Quantum Chromodynamics (QCD) [1] predicts that quarks and gluons bind together to form hadrons. These quarks and gluons behave as free particles at low-x or high momentum transfer (Q2), known as asymptotic freedom [2, 3], an intrinsic property of QCD. If nucleons, with their given spatial extension, were both elementary and incompressible, then a state of close packing would constitute the high- density limit of matter. Nucleons are bound states of point-like quarks. If the density of nucleons is increased, they will start to overlap each other, un- til they reach a state in which volume is comparable to the total volume of quarks. Beyond a certain point, hadrons lose their identity and form a phase of unbound quarks. According to cosmic microwave background studies, it is expected that up to a few microseconds after the Big Bang the Universe was in quark-gluon-plasma (QGP) phase. Now-a-days, such a state can be recre- ated in laboratories by colliding heavy-ions at relativistic speeds. Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory in New York, USA and Large Hadron Collider (LHC) at Geneva, Switzerland provide us a unique opportunity to study the nuclear matter at extreme conditions of temperature and density.