Shape of atomic nuclei in heavy ion collisions

Journal Article · 04 January 2022 · Physical Review. C

DOI: https://doi.org/10.1103/physrevc.105.014905 · OSTI ID:1979854

Jia, Jiangyong  ^[1]

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1. Stony Brook Univ., NY (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States); OSTI

In the hydrodynamic model description of heavy ion collisions, the final-state anisotropic flows v_n are linearly related to the strengths of the multipole shape of the distribution of nucleons in the transverse plane, ε_n: v_n∝ε_n. The ε_n, for n=1, 2, 3, 4, are sensitive to the shapes of the colliding ions, characterized by the quadrupole β₂, octupole β₃, and hexadecapole β₄ deformations. This sensitivity is investigated analytically and also in a Monte Carlo Glauber model. One observes a robust linear relation, $$\langleε^{2}_{n}\rangle$$ = $$a^{'}_{n} + b^{'}_{n}β^{2}_{n}$$, for events in a fixed centrality. The $$\langleε^{2}_{1}\rangle$$ has a contribution from β₃ and β₄, and $$\langleε^{2}_{3}\rangle$$ from β₄. In ultracentral collisions, there are little cross contributions between β₂ and ε₃ and between β₃ and ε₂, but clear cross contributions are present in noncentral collisions. Additionally, $$\langleε^{2}_{n}\rangle$$ are insensitive to nonaxial shape parameters such as the triaxiality. This is good news because the measurements of v₂, v₃, and v₄ can be used to constrain simultaneously the β₂, β₃, and β₄ values. This is best done by comparing two colliding ions with similar mass numbers and therefore nearly identical $$a^{'}_{n}$$, to obtain a simple equation that relates the β_n of the two species. Finally, this opens up the possibility to map the shape of the atomic nuclei at a timescale (<10^–24 s) much shorter than probed by low-energy nuclear structure physics (<10^–21 s), which ultimately may provide information complementary to that obtained in the nuclear structure experiments.

• Research Organization: State Univ. of New York (SUNY), Albany, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC); National Science Foundation (NSF)
• Grant/Contract Number: FG02-87ER40331
• OSTI ID: 1979854
• Journal Information: Physical Review. C, Journal Name: Physical Review. C Journal Issue: 1 Vol. 105; ISSN 2469-9985
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English