Effect of an electromagnetic field on the spectra and elliptic flow of particles

In 2+1 dimensions, the evolution of flow under the influence of an external electromagnetic field is simulated. The external electromagnetic field is exponentially decaying with time. Under the same initial conditions, flow evolution with and without the external electromagnetic field is compared. It was found that the production of particles was enhanced when the external electromagnetic field was present. As the strength of the electromagnetic field increased, more particles were produced. Enhancement is greater at the high transverse momentum than at the low transverse momentum. In addition, the electromagnetic field also modifies the elliptic flow and the modification is related to the mass and charge of the particles.

Figure 1

Transverse momentum spectra of ${\pi }^{+}$ and $K^{+}$ in Pb-Pb collisions in centralities 10–20%, obtained in the ideal hydrodynamic model with (dash-dotted lines) and without an external electromagnetic field (solid lines). Symbols represent data of the ALICE Collaboration [28].

Figure 2

Elliptic flow coefficients of the identified particles as a function of transverse momentum in the ideal case (solid lines) or with an electromagnetic field (dash-dotted lines); the symbols represent the results of the ALICE Collaboration [29], centrality 40–50%.

Figure 3

Transverse momentum spectra of photons in Pb-Pb collisions at the LHC in the 0–20% centrality range. The solid curve represents the ideal case, while the dash-dotted line represents the case in the electromagnetic field. The data are from Ref. [40].

Figure 4

Elliptic flow $v_2$ of the photons as a function of the transverse momentum $p_T$. The solid blue line is for an ideal fluid. The dash-dotted green line is for the fluid with an electromagnetic field. The symbols represent the results of the ALICE Collaboration [41, 42], centrality 0–40%.