Novel Cross Section Ratios as Possible Signals of Saturation in UPCs
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arXiv
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| Format: | Preprint |
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2023
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| _version_ | 1866914825068609536 |
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| author | Kovchegov, Yuri V. Sun, Huachen Tu, Zhoudunming |
| author_facet | Kovchegov, Yuri V. Sun, Huachen Tu, Zhoudunming |
| contents | We propose new cross section ratios in ultra-peripheral A$+$A and $p+$A collisions (UPCs) as a potential experimental signal of saturation physics. We consider the ratio $R_1$ of elastic vector meson photoproduction cross section to the inclusive hadron or jet photoproduction cross section. The ratio can be measured in the $γ+$A and $γ+ p$ collisions taking place in the UPCs. We label the ratios $R_1 ({\rm A})$ and $R_1 (p)$, respectively. Constructing the double ratio $R_{\rm{UPC}} ({\rm A}) = R_1 ({\rm A})/R_1 (p)$, and performing a small-$x$ calculation both in the quasi-classical approximation and by including small-$x$ evolution, we observe that $R_{\rm{UPC}} ({\rm A})$ exhibits a markedly different dependence on the nuclear atomic number inside and outside the saturation region. This result indicates that $R_{\rm{UPC}} ({\rm A})$ and $R_1 ({\rm A})$ measurements in UPCs may help in the experimental searches for the evidence of saturation physics. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2311_12208 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Novel Cross Section Ratios as Possible Signals of Saturation in UPCs Kovchegov, Yuri V. Sun, Huachen Tu, Zhoudunming High Energy Physics - Phenomenology High Energy Physics - Experiment Nuclear Experiment Nuclear Theory We propose new cross section ratios in ultra-peripheral A$+$A and $p+$A collisions (UPCs) as a potential experimental signal of saturation physics. We consider the ratio $R_1$ of elastic vector meson photoproduction cross section to the inclusive hadron or jet photoproduction cross section. The ratio can be measured in the $γ+$A and $γ+ p$ collisions taking place in the UPCs. We label the ratios $R_1 ({\rm A})$ and $R_1 (p)$, respectively. Constructing the double ratio $R_{\rm{UPC}} ({\rm A}) = R_1 ({\rm A})/R_1 (p)$, and performing a small-$x$ calculation both in the quasi-classical approximation and by including small-$x$ evolution, we observe that $R_{\rm{UPC}} ({\rm A})$ exhibits a markedly different dependence on the nuclear atomic number inside and outside the saturation region. This result indicates that $R_{\rm{UPC}} ({\rm A})$ and $R_1 ({\rm A})$ measurements in UPCs may help in the experimental searches for the evidence of saturation physics. |
| title | Novel Cross Section Ratios as Possible Signals of Saturation in UPCs |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment Nuclear Experiment Nuclear Theory |
| url | https://arxiv.org/abs/2311.12208 |