Estimate of the magnetic field strength in heavy-ion collisions (0907.1396v1)

Abstract: Magnetic fields created in the noncentral heavy-ion collision are studied within a microscopic transport model, namely the Ultrarelativistic Quantum Molecular Dynamics model (UrQMD). Simulations were carried out for different impact parameters within the SPS energy range ($E_{lab} = 10 - 158 A$ GeV) and for highest energies accessible for RHIC. We show that the magnetic field emerging in heavy-ion collisions has the magnitude of the order of $eB_y \sim 10^{-1} m_\pi^2$ for the SPS energy range and $eB_y \sim m_\pi^2$ for the RHIC energies. The estimated value of the magnetic field strength for the LHC energy amounts to $eB_y \sim 15 m_\pi^2$.

• The paper presents a quantitative analysis of magnetic field strengths in heavy-ion collisions using the UrQMD model.
• The paper finds that the transverse magnetic field scales with energy, reaching mπ² levels at RHIC and higher values at LHC.
• The paper highlights implications for phase transitions and the chiral magnetic effect by correlating impact parameters with energy density.

Magnetic Field Strength in Heavy-Ion Collisions: A Quantitative Analysis

The paper presents a detailed investigation of the magnetic fields generated in noncentral heavy-ion collisions using the Ultrarelativistic Quantum Molecular Dynamics model (UrQMD). The primary focus is the estimation of the magnetic field strength across various energies and impact parameters, along with an exploration of the broader implications for nuclear matter under extreme conditions.

Key Findings and Methodological Approach

The authors simulate heavy-ion collisions, particularly examining energies within the SPS range (10-158 A GeV) and those accessible at RHIC. Notably, they find that the magnetic field, in terms of its transverse component ($eB_y$), scales significantly with energy. At SPS energies, $eB_y$ approaches values of approximately $10^{-1} \cdot m_\pi^2$, while at RHIC energies, it approximates $m_\pi^2$. An extrapolation for LHC energies suggests even more intense magnetic fields, on the order of $15 \cdot m_\pi^2$.

The paper leverages UrQMD, a well-regarded transport model for simulating ultrarelativistic heavy-ion collisions, to carry out these calculations. This model allows for a nuanced view of the magnetic field's evolution over time and space within the collision environment. The calculations focus primarily on field strengths at the central point of the collision and examine homogeneity and fluctuation patterns.

Implications for Phase Transitions and Experimental Observations

A major implication of the paper is its relevance to the exploration of nuclear phase transitions, particularly the potential conversions to quark-gluon plasma (QGP) and transitions involving chiral restoration. By providing a rigorous quantitative assessment of the magnetic field, the paper enhances the understanding of conditions under which phenomena like the chiral magnetic effect might be observable.

The results are consistent with prior estimations carried out by other scholars, such as Kharzeev et al., substantiating the claim that magnetic fields in heavy-ion collisions at RHIC levels can be sufficient to probe for signs of such phase transitions. Furthermore, the authors highlight the relationship between impact parameter, magnetic field strength, and energy density, which plays a crucial role in the transition dynamics of nuclear matter.

Future Research Directions and Open Questions

While the paper provides a comprehensive quantitative framework, it also raises several questions that remain open for future research. For instance, the extent to which the modeled conditions can replicate those in an actual QGP state, and how the theoretical predictions might align with or diverge from empirical data collected from experimental facilities like RHIC and LHC.

Additionally, the potential influences of magnetic fields on local equilibration processes in the collision environment, as well as their interaction with other fundamental forces at play, remain fertile ground for further exploration. Understanding these complexities can yield deeper insights into the ATLAS and ALICE experiments at LHC, potentially contributing valuable context for interpreting collision data and refining theoretical models.

Ultimately, this paper offers valuable contributions to the field of nuclear physics by quantifying magnetic field strengths in heavy-ion collisions, elucidating their potential effects on phase transition processes, and framing new avenues for future exploration.