Two-particle correlations in azimuthal angle and pseudorapidity in central $$^7\hbox {Be}+{}^9\hbox {Be}$$ collisions at the CERN Super Proton Synchrotron
Authors:   NA61/SHINE Collaboration, Aduszkiewicz A. , Andronov E. V. , Antićić T. , Babkin V. , Baszczyk M. , Bhosale S. , Blondel A. , Bogomilov M. , Brandin A. , Bravar A. , Bryliński W. , Brzychczyk J. , Buryakov M. , Busygina O. , Bzdak A. , Cherif H. , Ćirković M. , Csanad M. , Cybowska J. , Czopowicz T. , Damyanova A. , Davis N. , Deliyergiyev M. , Deveaux M. , Dmitriev A. , Dominik W. , Dorosz P. , Dumarchez J. , Engel R. , Feofilov G. A. , Fields L. , Fodor Z. , Garibov A. , Gaździcki M. , Golosov O. , Golovatyuk V. , Golubeva M. , Grebieszkow K. , Guber F. , Haesler A. , Igolkin S. N. , Ilieva S. , Ivashkin A. , Johnson S. R. , Kadija K. , Kargin N. , Kashirin E. , Kiełbowicz M. , Kireyeu V. A. , Klochkov V. , Kolesnikov V. I. , Kolev D. , Korzenev A. , Kovalenko V. N. , Kowalski S. , Koziel M. , Krasnoperov A. , Kucewicz W. , Kuich M. , Kurepin A. , Larsen D. , László A. , Lazareva T. V. , Lewicki M. , Łojek K. , Lyubushkin V. V. , Maćkowiak-Pawłowska M. , Majka Z. , Maksiak B. , Malakhov A. I. , Marcinek A. , Marino A. D. , Marton K. , Mathes H.-J. , Matulewicz T. , Matveev V. , Melkumov G. L. , Merzlaya A. O. , Messerly B. , Mik Ł. , Morozov S. , Mrówczyński S. , Nagai Y. , Naskręt M. , Ozvenchuk V. , Paolone V. , Petukhov O. , Płaneta R. , Podlaski P. , Popov B. A. , Porfy B. , Posiadała-Zezula M. , Prokhorova D. S. , Pszczel D. , Puławski S. , Puzović J. , Ravonel M. , Renfordt R. , Röhrich D. , Rondio E. , Roth M. , Rumberger B. T. , Rumyantsev M. , Rustamov A. , Rybczynski M. , Rybicki A. , Sadovsky A. , Schmidt K. , Selyuzhenkov I. , Seryakov A. Yu. , Seyboth P. , Słodkowski M. , Staszel P. , Stefanek G. , Stepaniak J. , Strikhanov M. , Ströbele H. , Šuša T. , Taranenko A. , Tefelska A. , Tefelski D. , Tereshchenko V. , Toia A. , Tsenov R. , Turko L. , Ulrich R. , Unger M. , Uzhva D. , Valiev F. F. , Veberič D. , Vechernin V. V. , Wickremasinghe A. , Włodarczyk Z. , Wojcik K. , Wyszyński O. , Zimmerman E. D. , Zwaska R. 
Published: December 2020

A measurement of charged hadron pair correlations in two-dimensional$$\Delta \eta \Delta \phi $$ΔηΔϕ  space is presented. The analysis is based on total 30 million central Be + Be collisions observed in the NA61/SHINE detector at the CERN SPS for incident beam momenta of 19A, 30A, 40A, 75A, and 150A $$\text {Ge} \text {V}/c$$Ge/c. Measurements were carried out for unlike-sign and like-sign charge hadron pairs independently. The$$C(\Delta \eta ,\Delta \phi )$$C(Δη,Δϕ)correlation functions were compared with results from a similar analysis on p + p interactions at similar beam momenta per nucleon. General trends of the back-to-back correlations are similar in central Be + Be collisions and p + p interactions, but are suppressed in magnitude due to the increased combinatorial background. Predictions from theEposand UrQMD models are compared to the measurements. Evolution of an enhancement around$$(\Delta \eta ,\Delta \phi ) = (0,0)$$(Δη,Δϕ)=(0,0)with incident energy is observed in central Be + Be collisions. It is not predicted by both models and almost non-existing in proton–proton collisions at the same momentum per nucleon.