Bose-Einstein correlations between identified charged pions are measured for $p$+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV using data recorded by the ATLAS detector at the LHC corresponding to a total integrated luminosity of $28$ $\mathrm{nb}^{-1}$. Pions are identified using ionization energy loss measured in the pixel detector. Two-particle correlation functions and the extracted source radii are presented as a function of collision centrality as well as the average transverse momentum ($k_{\mathrm{T}}$) and rapidity ($y^{\star}_{\pi\pi}$) of the pair. Pairs are selected with a rapidity $-2 < y^{\star}_{\pi\pi} < 1$ and with an average transverse momentum $0.1 < k_{\mathrm{T}} < 0.8$ GeV. The effect of jet fragmentation on the two-particle correlation function is studied, and a method using opposite-charge pair data to constrain its contributions to the measured correlations is described. The measured source sizes are substantially larger in more central collisions and are observed to decrease with increasing pair $k_{\mathrm{T}}$. A correlation of the radii with the local charged-particle density is demonstrated. The scaling of the extracted radii with the mean number of participating nucleons is also used to compare a selection of initial-geometry models. The cross-term $R_\mathrm{ol}$ is measured as a function of rapidity, and a nonzero value is observed with $5.1\sigma$ combined significance for $-1 < y^{\star}_{\pi\pi} < 1$ in the most central events.
Author
Aaboud, M. : SUNY Albany
Aad, G. : University of Alberta
Abbott, B. : TOBB University of Economics and Technology
Abdallah, J. : SUNY Albany
Abdinov, O. : University of Alberta
Abeloos, B. : TOBB University of Economics and Technology
Aben, R. : University of Alberta
AbouZeid, O. S. : TOBB University of Economics and Technology
Abraham, N. : SUNY Albany
Abramowicz, H. : SUNY Albany
Abreu, H. : University of Alberta
Abreu, R. : TOBB University of Economics and Technology
Abulaiti, Y. : SUNY Albany
Acharya, B. : University of Alberta
Adamczyk, L. : TOBB University of Economics and Technology
Adams, D. : TOBB University of Economics and Technology
Adelman, J. : SUNY Albany
Adomeit, S. : University of Alberta
Adye, T. : Université Savoie Mont Blanc
Affolder, A. : Institut National de Physique Nucléaire et de Physique des Particules
Alison, J. : University of Chicago
Anderson, K. J. : University of Chicago
Bryant, P. : University of Chicago
Camacho Toro, R. : University of Chicago
Cheng, Y. : University of Chicago
Dandoy, J. R. : University of Chicago
Facini, G. : University of Chicago
Gardner, W. : University of Chicago
Kapliy, A. : University of Chicago
Kim, Y. K. : University of Chicago
Krizka, K. : University of Chicago
Li, H. L. : University of Chicago
Merritt, F. S. : University of Chicago
Miller, D. W. : University of Chicago
Oreglia, M. J. : University of Chicago
Pilcher, J. E. : University of Chicago
Saxon, J. : University of Chicago
Shochet, M. J. : University of Chicago
Stark, G. H. : University of Chicago
Swiatlowski, M. : University of Chicago
Vukotic, I. : University of Chicago
Wu, M. : University of Chicago