# Initial Stages 2021

Jan 10 – 15, 2021
Weizmann Institute of Science
Asia/Jerusalem timezone
See you at IS2023 in Copenhagen in June 2023

## Hot spots and gluon field fluctuations as causes of eccentricity in small systems

Jan 12, 2021, 7:40 PM
1h 30m
Patio (vDLCC)

### Patio

#### vDLCC

bullet talk (poster) Physics at low-x and gluon saturation

### Speaker

Sami Demirci (University of Jyväskylä)

### Description

We calculate eccentricities in dilute-dense limit of pA collisions, by calculating correlations functions of the energy density field of the Glasma immediately after the collision event at proper time $\tau = 0^{+}$. The proton is treated as a collection of a finite number of hot spots of Gaussianly distributed color charges, as in the IPGlasma setup. The correlations of its color charges are assumed to be Gaussian and are described by the MV model. However, instead of performing averages using Monte Carlo implementations we calculate the color charge and hot spot averages analytically to allow for better control over model parameters. The nucleus is taken to be an infinite sheet of color charge, and its color charge correlations are also assumed to be Gaussian and are described by the GBW model. For the nucleus we evaluate the full nonlinear Gaussian color charge correlations and the proton is expanded to the first order in the proton saturation scale in the dilute limit. We proceed to compute the one and two point functions for the energy density, performing the CGC and hot spot averaging procedures analytically. We then use these results to compute eccentricities originating from proton and nucleus side fluctuations separately, and find that proton fluctuations are the dominating source of eccentricity and the nucleus color fluctuations only give a negligible correction.

### Primary author

Sami Demirci (University of Jyväskylä)

### Co-authors

Tuomas Lappi (University of Jyvaskyla) Soeren Schlichting (Universität Bielefeld)

### Presentation materials

 IS2021_Sami_Demirci.mp4 IS2021Slides_Sami_Demirci.pdf