Hydrodynamic extension of a two-component model for hadroproduction in heavy-ion collisions

The dependence of the spectral shape of produced charged hadrons on the size of a colliding system is discussed using a two-component model. As a result, the system-size hierarchy in spectral shape is observed. Next, a hydrodynamic extension of a two-component model for hadroproduction using recent theoretical calculations is suggested to describe the spectra of charged particles produced in heavy-ion collisions in the full range of transverse momenta $p_T$. Data from heavy-ion collisions measured at the Relativistic Heavy Ion Collider and the Large Hadron Collider are analyzed using the introduced approach and are combined in terms of energy density. The observed regularities might be explained by the formation of a quark-gluon plasma during the collision.

Figure 1

Charged particle spectra in $\gamma \gamma$ [4] (a), $pp$ [5] (b), and central lead-lead collisions [3] (c) fitted to the function (2); the red (dashed) line shows the exponential term and the green (solid) and blue (dash-dot) lines show the two power-law terms.

Figure 2

Nuclear modification factor $R_{AA}$ measured for central lead-lead collisions [3] shown together with the terms of (2) independently divided over the fit (1) of the $pp$ data at the same c.m.s energy; the red (dashed) line shows the exponential term and the green (solid) and blue (dash-dot) lines show the two power-law terms.

Figure 3

Central lead-lead collisions [3] fitted with (4); the red (dashed) line shows the hydrodynamic term and the green (solid) and blue (dash-dot) lines show the two power-law terms.

Figure 4

Temperature of the final-state hadrons coming from the thermalized part of the spectra in heavy-ion collisions as a function of energy density. Full points show the results extracted from the fit by taking into account the collective flow (4) (marked with F. in the legend); open points show the results when using a fit with the Boltzmann exponent (2) (marked with B in the legend). The solid line stands for the $T_e\propto {(\varepsilon -B)}^{0.25}$ fit and the dashed line shows $T_e\to \mathrm{const}.$ behavior.