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

Aaij, R;Abdelmotteleb, A S W;Abellan Beteta, C;Abudinén, F;Ackernley, T;Adeva, B;Adinolfi, M;Afsharnia, H;Agapopoulou, C;Aidala, C A;Aiola, S;Ajaltouni, Z;Akar, S;Akiba, K;Albrecht, J;Alessio, F;Alexander, M;Alfonso Albero, A;Aliouche, Z;Alvarez Cartelle, P;Amato, S;Amey, J L;Amhis, Y;An, L;Anderlini, L;Andersson, M;Andreianov, A;Andreotti, M;Ao, D;Archilli, F;Artamonov, A;Artuso, M;Arzymatov, K;Aslanides, E;Atzeni, M;Audurier, B;Bachmann, S;Bachmayer, M;Back, J J;Bailly-Reyre, A;Baladron Rodriguez, P;Balagura, V;Baldini, W;Baptista de Souza Leite, J;Barbetti, M;Barlow, R J;Barsuk, S;Barter, W;Bartolini, M;Baryshnikov, F;Basels, J M;Bassi, G;Batsukh, B;Battig, A;Bay, A;Beck, A;Becker, M;Bedeschi, F;Bediaga, I B;Beiter, A;Belavin, V;Belin, S;Bellee, V;Belous, K;Belov, I;Belyaev, I;Bencivenni, G;Ben-Haim, E;Berezhnoy, A;Bernet, R;Berninghoff, D;Bernstein, H C;Bertella, C;Bertolin, A;Betancourt, C;Betti, F;Bezshyiko, Ia;Bhasin, S;Bhom, J;Bian, L;Bieker, M S;Biesuz, N V;Bifani, S;Billoir, 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2023-01-01

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Abstract

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 p(0) 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 (?(c.m.)) regions 2.5 < ?(c.m.) < 3.5 (forward) and -4.0 < ?(c.m.) < -3.0 (backward) defined relative to the proton beam direction. The forward measurement shows a sizable suppression of p(0) production, while the backward measurement shows the first evidence of p(0) 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.