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Sep 3 – 9, 2023
Hilton of the Americas, 1600 Lamar, Houston, Texas, 77010, USA
US/Central timezone

Investigation of initial state effects in p+Pb collisions at ATLAS via measurement of centrality dependence of dijet yields

Sep 5, 2023, 5:30 PM
2h 10m
Grand Ballroom, 4th floor ( Hilton of the Americas)

Grand Ballroom, 4th floor

Hilton of the Americas

Poster Initial state Poster Session


Riccardo Longo (Univ. Illinois at Urbana Champaign (US))


In this poster, we present the ATLAS measurement of the centrality dependence of the dijet per-event yield at center-of-mass energy 8.16 TeV in $p$+Pb collisions. The per-event yield of unfolded dijet pairs is presented in terms of kinematic variables that allow for full characterization of the partonic scattering system, i.e. the average $p_{\mathrm{T}}$ of the dijet, $p_{\mathrm{T,Avg}} = (p_{\mathrm{T,1}} + p_{\mathrm{T,2}})/2$, the boost of the dijet system, $y^{b} = (y^{\mathrm{CM}}_{1} + y^{\mathrm{CN}}_{2})/2$, and the half rapidity separation between the jets, $y^{\ast} = |y^{\mathrm{CM}}_{1} - y^{\mathrm{CM}}_{2}|/2$. Initial state effects are investigated by constructing central-to-peripheral ratios of dijet yields, $R_{\mathrm{CP}}$. We present $R_\mathrm{CP}$ results comparing central collisions with peripheral ones rescaled by the nuclear thickness function $T_{AB}$, in order to equalize the two based on pure geometrical expectations. The $R_\mathrm{CP}$ shows a clear dependence on the Bjorken-$x$ of the parton extracted from the proton in the hard-scattering, $x_\mathrm{p}$, while no clear trend is observed while displaying the results as a function $x_\mathrm{Pb}$. These results will help in understanding the implications introduced by the initial state kinematics in $p$+Pb collisions.

Category Experiment
Collaboration (if applicable) ATLAS Collaboration

Primary author

Riccardo Longo (Univ. Illinois at Urbana Champaign (US))

Presentation materials