Two-particle azimuthal correlations in $\gamma$p interactions using pPb collisions at $\sqrt{s_\mathrm{NN}}$ = 8.16 TeV

Understand

The first measurements of the Fourier coefficients ($V_{n\Delta}$) of the azimuthal distributions of charged hadrons emitted from photon-proton ($\gamma$p) interactions at the LHC are presented.

• The data are extracted from 68.8 nb$^{-1}$ of ultra-peripheral proton-lead (pPb) collisions at $\sqrt{s_\mathrm{NN}}$ = 8.16 TeV using the CMS detector.
• The high energy lead ions produce a flux of photons that can interact with the oncoming proton.
• This $\gamma$p system provides a set of unique initial conditions with multiplicity lower than in photon-lead collisions but comparable to recent electron-positron and electron-proton data.