Scaling properties of direct photon yields in heavy ion collisions
Abstract A recent analysis from the PHENIX collaboration of available direct photon measurement results in collisions of various systems such as Au+Au, Cu+Cu, and Pb+Pb, at different beam energies ranging from 39 to 2760 GeV, has shown a universal, within experimental uncertainties, multiplicity sca...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
SpringerOpen
2020-07-01
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| Series: | European Physical Journal C: Particles and Fields |
| Online Access: | http://link.springer.com/article/10.1140/epjc/s10052-020-8219-9 |
| Summary: | Abstract A recent analysis from the PHENIX collaboration of available direct photon measurement results in collisions of various systems such as Au+Au, Cu+Cu, and Pb+Pb, at different beam energies ranging from 39 to 2760 GeV, has shown a universal, within experimental uncertainties, multiplicity scaling, in which direct photon $$p_{T}$$ pT -spectra for transverse momenta up to 2 GeV/c are scaled with charged hadron pseudorapidity density at midrapidity raised to power $$\alpha =1.25$$ α=1.25 . On the other hand, those direct photon $$p_{T}$$ pT -spectra also exhibit geometrical scaling in the similar $$p_{T}$$ pT range. Assuming power-law dependence of the scaled photon spectra for both scaling laws, we formulate two independent conditions for the power $$\alpha $$ α , which overshoot experimental data by $$\sim 10\%$$ ∼10% on average. We discuss possible sources that might improve this estimate. |
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| ISSN: | 1434-6044 1434-6052 |