The shape of differential radial flow $v_0(p_T)$, not its zero-crossing, carries physical information
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| Format: | Preprint |
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2025
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| _version_ | 1866913070052278272 |
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| author | Bhatta, Somadutta Dimri, Aman Jia, Jiangyong |
| author_facet | Bhatta, Somadutta Dimri, Aman Jia, Jiangyong |
| contents | Radial flow, a key collective phenomenon in heavy-ion collisions, manifests itself through event-by-event fluctuations of transverse-momentum ($p_{\mathrm{T}}$) spectra. The $p_{\mathrm{T}}$-differential radial flow observable, $v_0(p_{\mathrm{T}})$, was introduced to quantify local spectral-shape fluctuations, but it is unavoidably influenced by global multiplicity fluctuations. Using the HIJING model, we show that different event-activity definitions for centrality classification and different spectral normalization schemes generate a constant vertical offset in $v_0(p_{\mathrm{T}})$ without altering its shape. This offset reflects the impact of residual volume/centrality fluctuations rather than genuine dynamical radial flow fluctuations. Accordingly, only the shape of $v_0(p_{\mathrm{T}})$, or equivalently its derivative $dv_0(p_{\mathrm{T}})/dp_{\mathrm{T}}$, carries physical information about radial-flow dynamics; its zero crossing does not. Practical implications include the need to vertically align measurements from different experiments before comparison, thereby removing normalization ambiguities when constraining QGP properties. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2504_20008 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The shape of differential radial flow $v_0(p_T)$, not its zero-crossing, carries physical information Bhatta, Somadutta Dimri, Aman Jia, Jiangyong Nuclear Theory High Energy Physics - Phenomenology Nuclear Experiment Radial flow, a key collective phenomenon in heavy-ion collisions, manifests itself through event-by-event fluctuations of transverse-momentum ($p_{\mathrm{T}}$) spectra. The $p_{\mathrm{T}}$-differential radial flow observable, $v_0(p_{\mathrm{T}})$, was introduced to quantify local spectral-shape fluctuations, but it is unavoidably influenced by global multiplicity fluctuations. Using the HIJING model, we show that different event-activity definitions for centrality classification and different spectral normalization schemes generate a constant vertical offset in $v_0(p_{\mathrm{T}})$ without altering its shape. This offset reflects the impact of residual volume/centrality fluctuations rather than genuine dynamical radial flow fluctuations. Accordingly, only the shape of $v_0(p_{\mathrm{T}})$, or equivalently its derivative $dv_0(p_{\mathrm{T}})/dp_{\mathrm{T}}$, carries physical information about radial-flow dynamics; its zero crossing does not. Practical implications include the need to vertically align measurements from different experiments before comparison, thereby removing normalization ambiguities when constraining QGP properties. |
| title | The shape of differential radial flow $v_0(p_T)$, not its zero-crossing, carries physical information |
| topic | Nuclear Theory High Energy Physics - Phenomenology Nuclear Experiment |
| url | https://arxiv.org/abs/2504.20008 |