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arXiv · 2506.11370

Asymmetric muon-antimuon emission from $Z^0$ decays: a clear magnetometer in relativistic heavy-ion collisions

Alejandro Ayala·Ana Julia Mizher·Javier Rendón
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Abstract

We show that a very clear signal of the presence of a strong magnetic field during the early stage of a high-energy heavy-ion collision is provided by the decay of the $Z^0$ into dimuon pairs. We find that the process is highly anisotropic, producing pairs mainly out of plane, as signaled by a negative value of $v_2$, and leads to an antimuon transverse momentum distribution which peaks at a higher value of the transverse momentum compared to the peak of the muon transverse momentum distribution. We also show that the process does not produce a significant distortion of the $Z^0$ spectral function. The signal can be identified by comparing the dimuon-invariant mass and the individual muon and antimuon spectra produced in semicentral heavy-ion collisions with the corresponding scaled spectra produced in p+p collisions at the $Z^0$ peak.

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Alejandro Ayala, Ana Julia Mizher, Javier Rendón. 2025-06-13. Asymmetric muon-antimuon emission from $Z^0$ decays: a clear magnetometer in relativistic heavy-ion collisions. https://arxiv.org/abs/2506.11370

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