CERN Accelerating science

Preprint
Report number	arXiv:2312.06572 ; CERN-EP-2023-283
Title	Evidence of isospin-symmetry violation in high-energy collisions of atomic nuclei
Author(s)	Adhikary, H. (Jan Kochanowski U.) ; Adrich, P. (Warsaw, Inst. Nucl. Studies) ; Allison, K.K. (Colorado U.) ; Amin, N. (KIT, Karlsruhe) ; Andronov, E.V. (Unlisted) ; Arsene, I.-C. (Oslo U.) ; Bajda, M. (Jagiellonian U.) ; Balkova, Y. (Silesia U.) ; Battaglia, D. (U. Notre Dame (main)) ; Bazgir, A. (Jan Kochanowski U.) ; Bhosale, S. (Cracow, INP) ; Bielewicz, M. (Warsaw, Inst. Nucl. Studies) ; Blondel, A. (Paris U., VI-VII) ; Bogomilov, M. (Sofiya U.) ; Bondar, Y. (Jan Kochanowski U.) ; Brandin, A. ; Bryliński, W. (Warsaw U. of Tech. (main)) ; Brzychczyk, J. (Jagiellonian U.) ; Buryakov, M. (Unlisted) ; Camino, A.F. ; Ćirković, M. (Belgrade U.) ; Csanád, M. (Eotvos U.) ; Cybowska, J. (Warsaw U. of Tech. (main)) ; Czopowicz, T. (Jan Kochanowski U.) ; Dalmazzone, C. (Paris U., VI-VII) ; Davis, N. (Cracow, INP) ; Dmitriev, A. (Unlisted) ; von Doetinchem, P. (Hawaii U.) ; Dominik, W. (Warsaw U.) ; Dumarchez, J. (Paris U., VI-VII) ; Engel, R. (KIT, Karlsruhe) ; Giacosa, F. (Unlisted) ; Gorenstein, M.I. ; Poberezhniuk, R. ; Samanta, S. ; Fields, L. (U. Notre Dame (main)) ; Fodor, Z. (Wigner RCP, Budapest ; Wroclaw U.) ; Friend, M. (KEK, Tsukuba) ; Gaździcki, M. (Jan Kochanowski U.) ; Golosov, O. (Unlisted) ; Golovatyuk, V. (Unlisted) ; Golubeva, M. (Unlisted) ; Grebieszkow, K. (Warsaw U. of Tech. (main)) ; Guber, F. (Unlisted) ; Igolkin, S.N. ; Ilieva, S. (Sofiya U.) ; Ivashkin, A. (Unlisted) ; Izvestnyy, A. (Unlisted) ; Kargin, N. ; Karpushkin, N. (Unlisted) ; Kashirin, E. (Unlisted) ; Kiełbowicz, M. (Cracow, INP) ; Kireyeu, V.A. (Unlisted) ; Kolesnikov, R. (Unlisted) ; Kolev, D. (Sofiya U.) ; Koshio, Y. ; Kovalenko, V.N. (Unlisted) ; Kowalski, S. (Silesia U.) ; Kozłowski, B. (Warsaw U. of Tech. (main)) ; Krasnoperov, A. (Unlisted) ; Kucewicz, W. (AGH-UST, Cracow) ; Kuchowicz, M. (Wroclaw U.) ; Kuich, M. (Warsaw U.) ; Kurepin, A. (Unlisted) ; László, A. (Wigner RCP, Budapest) ; Lewicki, M. (Wroclaw U.) ; Lykasov, G. (Unlisted) ; Lyubushkin, V.V. (Unlisted) ; Maćkowiak-Pawłowska, M. (Warsaw U. of Tech. (main)) ; Majka, Z. (Jagiellonian U.) ; Makhnev, A. (Unlisted) ; Maksiak, B. (Warsaw, Inst. Nucl. Studies) ; Malakhov, A.I. (Unlisted) ; Marcinek, A. (Cracow, INP) ; Marino, A.D. (Colorado U.) ; Mathes, H.-J. (KIT, Karlsruhe) ; Matulewicz, T. (Warsaw U.) ; Matveev, V. (Unlisted) ; Melkumov, G.L. (Unlisted) ; Merzlaya, A. (Oslo U.) ; Mik, Ł. (AGH-UST, Cracow) ; Morozov, S. (Unlisted) ; Nagai, Y. (Eotvos U.) ; Nakadaira, T. (KEK, Tsukuba) ; Naskret, M. (Wroclaw U.) ; Nishimori, S. ; Olivier, A. (U. Notre Dame (main)) ; Ozvenchuk, V. (Cracow, INP) ; Panova, O. (Jan Kochanowski U.) ; Paolone, V. (Pittsburgh U.) ; Petukhov, O. (Unlisted) ; Pidhurskyi, I. (Jan Kochanowski U.) ; Płaneta, R. (Jagiellonian U.) ; Podlaski, P. (Warsaw U.) ; Popov, B.A. (Unlisted ; Paris U., VI-VII) ; Pórfy, B. (Wigner RCP, Budapest ; Eotvos U.) ; Prokhorova, D.S. (Unlisted) ; Pszczel, D. (Warsaw, Inst. Nucl. Studies) ; Puławski, S. (Silesia U.) ; Puzovic, J. ; Renfordt, R. (Silesia U.) ; Ren, L. (Colorado U.) ; Reyna Ortiz, V.Z. (Jan Kochanowski U.) ; Röhrich, D. ; Rondio, E. (Warsaw, Inst. Nucl. Studies) ; Roth, M. (KIT, Karlsruhe) ; Rozpłochowski, Ł. (Cracow, INP) ; Rumberger, B.T. (Colorado U.) ; Rumyantsev, M. (Unlisted) ; Rustamov, A. (NNRC, Baku) ; Rybczynski, M. (Jan Kochanowski U.) ; Rybicki, A. (Cracow, INP) ; Rybka, D. ; Sakashita, K. (KEK, Tsukuba) ; Schmidt, K. (Silesia U.) ; Seryakov, A.Yu. (Unlisted) ; Seyboth, P. (Jan Kochanowski U.) ; Shah, U.A. (Jan Kochanowski U.) ; Shiraishi, Y. ; Shukla, A. (Hawaii U.) ; Słodkowski, M. (Warsaw U. of Tech. (main)) ; Staszel, P. (Jagiellonian U.) ; Stefanek, G. (Jan Kochanowski U.) ; Stepaniak, J. (Warsaw, Inst. Nucl. Studies) ; Strikhanov, M. ; Ströbele, H. ; Šuša, T. (Boskovic Inst., Zagreb) ; Świderski, Ł. (Warsaw, Inst. Nucl. Studies) ; Szewiński, J. (Warsaw, Inst. Nucl. Studies) ; Szukiewicz, R. (Wroclaw U.) ; Taranenko, A. (Unlisted) ; Tefelska, A. (Warsaw U. of Tech. (main)) ; Tefelski, D. (Warsaw U. of Tech. (main)) ; Tereshchenko, V. ; Tsenov, R. (Sofiya U.) ; Turko, L. (Wroclaw U.) ; Tveter, T.S. (Oslo U.) ; Unger, M. ; Urbaniak, M. (Silesia U.) ; Valiev, F.F. (Unlisted) ; Veberič, D. (KIT, Karlsruhe) ; Vechernin, V.V. (Unlisted) ; Vitiuk, O. (Wroclaw U.) ; Volkov, V. (Unlisted) ; Wickremasinghe, A. (Fermilab) ; Witek, K. (AGH-UST, Cracow) ; Wójcik, K. (Silesia U.) ; Wyszyński, O. (Jan Kochanowski U.) ; Zaitsev, A. (Unlisted) ; Zherebtsova, E. (Wroclaw U.) ; Zimmerman, E.D. (Colorado U.) ; Zviagina, A. (Unlisted) ; Zwaska, R. (Fermilab)
Corporate author(s)	The NA61 collaboration
Publication	2024
Imprint	18 Oct 2024
Number of pages	30
Note	The paper includes updates based on the final results of $K^+$ and $K^-$ yields published in Eur. Phys. J.C 84 (2024) 4, 416
Published in:	Nature
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN SPS ; NA61
Keywords	QCD ; particle and resonance production ; experimental results ; quarks, strong interaction, isospin symmetry, nucleus-nucleus collisions, strange meson production
Abstract	Strong interactions preserve an approximate isospin symmetry between up ($u$) and down ($d$) quarks, part of the more general flavor symmetry. In the case of $K$ meson production, if this isospin symmetry were exact, it would result in equal numbers of charged ($K^+$ and $K^-$) and neutral ($K^0$ and $\overline K^{\,0}$) mesons in the final state. Here, we report results on the relative abundance of charged over neutral $K$ meson production in argon and scandium nuclei collisions at a center-of-mass energy of 11.9 GeV per nucleon pair. We find that the production of $K^+$ and $K^-$ mesons at mid-rapidity is $(18.4\pm 6.1)\%$ higher than that of the neutral $K$ mesons. Although with large uncertainties, earlier data on nucleus-nucleus collisions in the collision center-of-mass energy range $2.6 < \sqrt{s_{NN}} < 200$ GeV are consistent with the present result. Using well-established models for hadron production, we demonstrate that known isospin-symmetry breaking effects and the initial nuclei containing more neutrons than protons lead only to a small (few percent) deviation of the charged-to-neutral kaon ratio from unity at high energies. Thus, they cannot explain the measurements. The significance of the flavor-symmetry violation beyond the known effects is 4.7$\sigma$ when the compilation of world data with uncertainties quoted by the experiments is used. New systematic, high-precision measurements and theoretical efforts are needed to establish the origin of the observed large isospin-symmetry breaking.
Other source	Inspire
Copyright/License	Preprint: © 2023-2024 CERN (License: CC-BY-4.0)
Submitted by	marek.gazdzicki@cern.ch