Nuclear Modification Factor of Neutral Pions in the Forward and Backward Regions in p-Pb Collisions

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doi:10.1103/PhysRevLett.131.042302

The nuclear modification factor of neutral pions is measured in proton-lead collisions collected at a center-of-mass energy per nucleon of 8.16 TeV with the LHCb detector. The π0 production cross section is measured differentially in transverse momentum (p_T) for 1.5 < p_T < 10.0 GeV and in center-of-mass pseudorapidity (η_c.m.) regions 2.5 < η_c.m. < 3.5 (forward) and −4.0 < η_c.m. < −3.0 (backward) defined relative to the proton beam direction. The forward measurement shows a sizable suppression of π0 production, while the backward measurement shows the first evidence of π0 enhancement in proton-lead collisions at the LHC. Together, these measurements provide precise constraints on models of nuclear structure and particle production in high-energy nuclear collisions.

Aaij, R., Abdelmotteleb, A.S.W., Abellan Beteta, C., Abudinén, F., Ackernley, T., Adeva, B., et al. (2023). Nuclear Modification Factor of Neutral Pions in the Forward and Backward Regions in p-Pb Collisions. PHYSICAL REVIEW LETTERS, 131(4), 1-12 [10.1103/PhysRevLett.131.042302].