XXVIII International Workshop on Deep Inelastic Scattering and Related Subjects

First measurement of diffraction in pPb and pp collisions with CMS and Search for elliptic azimuthal anisotropies in γp interactions within ultra-peripheral pPb collisions at sqrtsNN = 8.16 TeV

Not scheduled

20m

Brooklyn, NY

Contributed Talk Small-x, Diffraction and Vector Mesons Small-x, Diffraction and Vector Mesons

Speaker

Michael Murray (The University of Kansas (US))

Description

We present a first measurement of two-particle angular correlations for charged hadrons emitted from photon-proton, $\gamma p$, interactions over a wide range of pseudorapidity and full azimuth. The $\gamma p$ events were produced within ultra-peripheral pPb collisions at $\sqrt{s_{NN}}$ = 8.16 TeV and were selected by requiring a large rapidity gap in the lead-going direction and no neutron emission from the lead nucleus. The results are compared to a sample of minimum-bias pPb events with same multiplicity. The observed azimuthal correlations at large relative pseudorapidity are used to extract the first, second and third-order two-particle anisotropy harmonics, V1D, V2D, and V3D as a function of track multiplicity and transverse momentum pT. For both the photon-p and minimum-bias pPb samples V1D is negative, V2D is positive and V3D is negative but consistent with zero. The single particle second-order harmonic, v2 (pT) is larger for photon-p events than for minimum-bias pPb collisions of the same multiplicity.