Role of net baryon density on rapidity width of identified particles from the lowest energies available at the CERN Super Proton Synchrotron to those at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider

Widths of the rapidity distributions of various identified hadrons generated with the UrQMD-3.4 event generator at all the Super Proton Synchrotron (SPS) energies have been presented and compared with the existing experimental results. An increase in the width of the rapidity distribution of $\mathrm{\Lambda }$ could be seen with both Monte Carlo (MC) and experimental data for the studied energies. Using MC data, the study has been extended to Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies. A similar jump, as observed in the plot of rapidity width versus rest mass at Alternating Gradient Synchrotron (AGS) and all SPS energies, persists even at RHIC and LHC energies, confirming its universal nature from AGS to the highest LHC energies. Such observation indicates that pair production may not be the only mechanism of particle production at the highest LHC energies. However, with MC data, the separate mass scaling for mesons and baryons is found to exist even at the top LHC energy.

Figure 1

Comparison of experimental (NA49) rapidity distributions of ${\pi }^{-},K^{-},\varphi$, and $\mathrm{\Lambda }$ in Pb-Pb collisions with UrQMD-3.4, AMPT (string melting) generated data at $E_{\mathrm{lab}}=20,30,40,80$, and $158\mathit{A}$ GeV and UrQMD (Hydro) at $158\mathit{A}$ GeV [1, 11, 12, 13, 14]. The blue open circular symbols represent the experimental results of NA49, whereas the blue solid, black dotted, and red dashed curves denote the results of UrQMD-3.4, UrQMD-3.4 (Hydro), and AMPT (string melting) data respectively. The magenta solid and dotted curves represent the rapidity distributions of $\mathrm{\Lambda }+{\mathrm{\Sigma }}^0$ using UrQMD-3.4 and UrQMD-3.4 (Hydro) data.

Figure 2

Width of the rapidity distribution as a function of masses of ${\pi }^{-},K^{-},\varphi ,\mathrm{\Lambda },{\mathrm{\Xi }}^{-}$, and ${\mathrm{\Omega }}^{-}$ in Pb-Pb collisions at all the SPS energies using UrQMD-3.4-generated events (left panel) and NA49 results (right panel) [1, 12].

Figure 3

Pseudorapidity distributions of all charged particles in Au-Au collisions at different RHIC energies $\sqrt{{\mathit{s}}_{NN}}=19.6,62.4,130$, and 200 GeV ($3\%$ central) and compared with existing experimental results of PHOBOS [15]. The red open circular symbols represent the experimental results of PHOBOS, whereas the magenta dotted and blue solid curves denote the UrQMD-3.4-generated data with default mode and switching off the weak decay channels.

Figure 4

Pseudorapidity distributions of all charged particles in Pb-Pb collisions at LHC energies, $\sqrt{{\mathit{s}}_{NN}}=2.76$ (left panel) and 5.02 TeV (right panel) for $0–5\%$ centrality and compared with existing experimental results of ALICE at 2.76 TeV[16]. The red open circular symbols represent the experimental results of ALICE, whereas the magenta dotted and blue solid curves denote the UrQMD-3.4-generated data with default mode and switching off the weak decay channels.

Figure 5

Width of the rapidity distribution of various produced particles as a function of their masses for Pb-Pb collisions at RHIC and LHC energies using UrQMD-3.4-generated events. The solid lines with different colors correspond to various beam energies.

Figure 6

Variation of the width of the rapidity distribution of various produced particles as a function of collision energy for Pb-Pb collisions at all the SPS energies for both NA49 and UrQMD-3.4-generated events. The solid lines and different marker symbols with different colors respectively denote the UrQMD-3.4-generated data and experimental results of various identified particles.

Figure 7

Distributions of $B-\overline{B}$, $\mathrm{\Lambda }$, and $\overline{\mathrm{\Lambda }}$ over the rapidity space at RHIC energies using UrQMD-3.4-generated events. The filled circular symbols denote the $B-\overline{B}$ rapidity distributions, whereas the filled squares and open circular symbols respectively represent the rapidity distributions of $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$.

Figure 8

Distributions of $B-\overline{B}$, $\mathrm{\Lambda }$, and $\overline{\mathrm{\Lambda }}$ over the rapidity space at $\sqrt{{\mathit{s}}_{NN}}=2.76$ and 5.02 TeV using UrQMD-3.4-generated events. The filled circular symbols denote the $B-\overline{B}$ rapidity distributions, whereas the filled squares and open circular symbols respectively represent the rapidity distributions of $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$.