Measurements of $$\pi ^-$$ production in $$^7$$Be + $$^9$$Be collisions at beam momenta from 19A to 150$$A\,\text{ GeV }\!/\!c$$ in the NA61/SHINE experiment at the CERN SPS
Authors: Acharya A. , Adhikary H. , Aduszkiewicz A. , Allison K. K. , 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. , Sadhu S. , 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: October 2020

The NA61/SHINE collaboration studies at the CERN Super Proton Synchrotron (SPS) the onset of deconfinement in hadronic matter by the measurement of particle production in collisions of nuclei with various sizes at a set of energies covering the SPS energy range. This paper presents results on inclusive double-differential spectra and mean multiplicities of$$\pi ^{-}$$π-mesons produced in the 5% mostcentral$$^7$$7Be +$$^9$$9Be collisions at beam momenta of 19A, 30A, 40A, 75Aand 150$$A\,\text{ GeV }\!/\!c$$AGeV/cobtained by the so-called$$h^-$$h-method which does not require any particle identification. The shape of the transverse mass spectra differs from the shapes measured incentralPb + Pb collisions and inelasticp+pinteractions. The normalized width of the rapidity distribution decreases with increasing collision energy and is in between the results for inelastic nucleon–nucleon andcentralPb + Pb collisions. The mean multiplicity of pions per wounded nucleon incentral$$^7$$7Be +$$^9$$9Be collisions is close to that incentralPb + Pb collisions up to 75$$A\,\text{ GeV }\!/\!c$$AGeV/c. However, at the top SPS energy the result lies between those for nucleon–nucleon and Pb + Pb interactions. The results are discussed in the context of predictions for the onset of deconfinement at the CERN SPS collision energies.