Eur. Phys. J. C (2024) 84: 1264
https://doi.org/10.1140/epjc/s10052-024-13244-0

Regular Article

Search for CP violation in ${\text{D}}^0\to {\text{K}}_{\text{S}}^0{\text{K}}_{\text{S}}^0$ decays in proton–proton collisions at $\sqrt{s}=13\text{Te}\text{V}$

¹ Yerevan Physics Institute, Yerevan, Armenia
² Institut für Hochenergiephysik, Vienna, Austria
³ Universiteit Antwerpen, Antwerpen, Belgium
⁴ Vrije Universiteit Brussel, Brussel, Belgium
⁵ Université Libre de Bruxelles, Bruxelles, Belgium
⁶ Ghent University, Ghent, Belgium
⁷ Université Catholique de Louvain, Louvain-la-Neuve, Belgium
⁸ Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil
⁹ Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
¹⁰ Universidade Estadual Paulista, Universidade Federal do ABC, São Paulo, Brazil
¹¹ Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia, Bulgaria
¹² University of Sofia, Sofia, Bulgaria
¹³ Instituto De Alta Investigación, Universidad de Tarapacá, Casilla 7 D, Arica, Chile
¹⁴ Beihang University, Beijing, China
¹⁵ Department of Physics, Tsinghua University, Beijing, China
¹⁶ Institute of High Energy Physics, Beijing, China
¹⁷ State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China
¹⁸ Guangdong Provincial Key Laboratory of Nuclear Science and Guangdong-Hong Kong Joint Laboratory of Quantum Matter, South China Normal University, Guangzhou, China
¹⁹ Sun Yat-Sen University, Guangzhou, China
²⁰ University of Science and Technology of China, Hefei, China
²¹ Nanjing Normal University, Nanjing, China
²² Institute of Modern Physics and Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Fudan University, Shanghai, China
²³ Zhejiang University, Hangzhou, Zhejiang, China
²⁴ Universidad de Los Andes, Bogotá, Colombia
²⁵ Universidad de Antioquia, Medellín, Colombia
²⁶ Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, Split, Croatia
²⁷ University of Split, Faculty of Science, Split, Croatia
²⁸ Institute Rudjer Boskovic, Zagreb, Croatia
²⁹ University of Cyprus, Nicosia, Cyprus
³⁰ Charles University, Prague, Czech Republic
³¹ Universidad San Francisco de Quito, Quito, Ecuador
³² Academy of Scientific Research and Technology of the Arab Republic of Egypt, Egyptian Network of High Energy Physics, Cairo, Egypt
³³ Center for High Energy Physics (CHEP-FU), Fayoum University, El-Fayoum, Egypt
³⁴ National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
³⁵ Department of Physics, University of Helsinki, Helsinki, Finland
³⁶ Helsinki Institute of Physics, Helsinki, Finland
³⁷ Lappeenranta-Lahti University of Technology, Lappeenranta, Finland
³⁸ IRFU, CEA, Université Paris-Saclay, Gif-sur-Yvette, France
³⁹ Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
⁴⁰ Université de Strasbourg, CNRS, IPHC UMR 7178, Strasbourg, France
⁴¹ Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique des Particules, CNRS/IN2P3, Villeurbanne, France
⁴² Institut de Physique des 2 Infinis de Lyon (IP2I ), Villeurbanne, France
⁴³ Georgian Technical University, Tbilisi, Georgia
⁴⁴ I. Physikalisches Institut, RWTH Aachen University, Aachen, Germany
⁴⁵ III. Physikalisches Institut A, RWTH Aachen University, Aachen, Germany
⁴⁶ III. Physikalisches Institut B, RWTH Aachen University, Aachen, Germany
⁴⁷ Deutsches Elektronen-Synchrotron, Hamburg, Germany
⁴⁸ University of Hamburg, Hamburg, Germany
⁴⁹ Karlsruher Institut fuer Technologie, Karlsruhe, Germany
⁵⁰ Institute of Nuclear and Particle Physics (INPP), NCSR Demokritos, Aghia Paraskevi, Greece
⁵¹ National and Kapodistrian University of Athens, Athens, Greece
⁵² National Technical University of Athens, Athens, Greece
⁵³ University of Ioánnina, Ioannina, Greece
⁵⁴ HUN-REN Wigner Research Centre for Physics, Budapest, Hungary
⁵⁵ MTA-ELTE Lendület CMS Particle and Nuclear Physics Group, Eötvös Loránd University, Budapest, Hungary
⁵⁶ Faculty of Informatics, University of Debrecen, Debrecen, Hungary
⁵⁷ Institute of Nuclear Research ATOMKI, Debrecen, Hungary
⁵⁸ Karoly Robert Campus, MATE Institute of Technology, Gyongyos, Hungary
⁵⁹ Panjab University, Chandigarh, India
⁶⁰ University of Delhi, Delhi, India
⁶¹ Saha Institute of Nuclear Physics, HBNI, Kolkata, India
⁶² Indian Institute of Technology Madras, Madras, India
⁶³ Tata Institute of Fundamental Research-A, Mumbai, India
⁶⁴ Tata Institute of Fundamental Research-B, Mumbai, India
⁶⁵ National Institute of Science Education and Research, An OCC of Homi Bhabha National Institute, Bhubaneswar, Odisha, India
⁶⁶ Indian Institute of Science Education and Research (IISER), Pune, India
⁶⁷ Isfahan University of Technology, Isfahan, Iran
⁶⁸ Institute for Research in Fundamental Sciences (IPM), Tehran, Iran
⁶⁹ University College Dublin, Dublin, Ireland
⁷⁰ INFN Sezione di Bari,Università di Bari, Politecnico di Bari, Bari, Italy
⁷¹ INFN Sezione di Bologna, Università di Bologna, Bologna, Italy
⁷² INFN Sezione di Catania, Università di Catania, Catania, Italy
⁷³ INFN Sezione di Firenze,Università di Firenze, Firenze, Italy
⁷⁴ INFN Laboratori Nazionali di Frascati, Frascati, Italy
⁷⁵ INFN Sezione di Genova,Università di Genova, Genoa, Italy
⁷⁶ INFN Sezione di Milano-Bicocca,Università di Milano-Bicocca, Milan, Italy
⁷⁷ INFN Sezione di Napoli, Università di Napoli ’Federico II’, Napoli, Italy; Università della Basilicata, Potenza, Italy; Scuola Superiore Meridionale (SSM), Naples, Italy
⁷⁸ INFN Sezione di Padova, Università di Padova, Padova, Italy; Università di Trento, Trento, Italy
⁷⁹ INFN Sezione di Pavia, Università di Pavia, Pavia, Italy
⁸⁰ INFN Sezione di Perugia, Università di Perugia, Perugia, Italy
⁸¹ INFN Sezione di Pisa, Università di Pisa, Scuola Normale Superiore di Pisa, Pisa, Italy; Università di Siena, Siena, Italy
⁸² INFN Sezione di Roma, Sapienza Università di Roma, Rome, Italy
⁸³ INFN Sezione di Torino, Università di Torino, Torino, Italy; Università del Piemonte Orientale, Novara, Italy
⁸⁴ INFN Sezione di Trieste, Università di Trieste, Trieste, Italy
⁸⁵ Kyungpook National University, Daegu, Korea
⁸⁶ Department of Mathematics and Physics-GWNU, Gangneung, Korea
⁸⁷ Chonnam National University, Institute for Universe and Elementary Particles, Kwangju, Korea
⁸⁸ Hanyang University, Seoul, Korea
⁸⁹ Korea University, Seoul, Korea
⁹⁰ Department of Physics, Kyung Hee University, Seoul, Korea
⁹¹ Sejong University, Seoul, Korea
⁹² Seoul National University, Seoul, Korea
⁹³ University of Seoul, Seoul, Korea
⁹⁴ Department of Physics, Yonsei University, Seoul, Korea
⁹⁵ Sungkyunkwan University, Suwon, Korea
⁹⁶ College of Engineering and Technology, American University of the Middle East (AUM), Dasman, Kuwait
⁹⁷ Riga Technical University, Riga, Latvia
⁹⁸ University of Latvia (LU), Riga, Latvia
⁹⁹ Vilnius University, Vilnius, Lithuania
¹⁰⁰ National Centre for Particle Physics, Universiti Malaya, Kuala Lumpur, Malaysia
¹⁰¹ Universidad de Sonora (UNISON), Hermosillo, Mexico
¹⁰² Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico
¹⁰³ Universidad Iberoamericana, Mexico City, Mexico
¹⁰⁴ Benemerita Universidad Autonoma de Puebla, Puebla, Mexico
¹⁰⁵ University of Montenegro, Podgorica, Montenegro
¹⁰⁶ University of Canterbury, Christchurch, New Zealand
¹⁰⁷ National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan
¹⁰⁸ Faculty of Computer Science, Electronics and Telecommunications, AGH University of Krakow, Kraków, Poland
¹⁰⁹ National Centre for Nuclear Research, Swierk, Poland
¹¹⁰ Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland
¹¹¹ Warsaw University of Technology, Warsaw, Poland
¹¹² Laboratório de Instrumentação e Física Experimental de Partículas, Lisbon, Portugal
¹¹³ Faculty of Physics, University of Belgrade, Belgrade, Serbia
¹¹⁴ VINCA Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia
¹¹⁵ Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain
¹¹⁶ Universidad Autónoma de Madrid, Madrid, Spain
¹¹⁷ Universidad de Oviedo, Instituto Universitario de Ciencias y Tecnologías Espaciales de Asturias (ICTEA), Oviedo, Spain
¹¹⁸ Instituto de Física de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain
¹¹⁹ University of Colombo, Colombo, Sri Lanka
¹²⁰ Department of Physics, University of Ruhuna, Matara, Sri Lanka
¹²¹ CERN, European Organization for Nuclear Research, Geneva, Switzerland
¹²² Paul Scherrer Institut, Villigen, Switzerland
¹²³ ETH Zurich-Institute for Particle Physics and Astrophysics (IPA), Zurich, Switzerland
¹²⁴ Universität Zürich, Zurich, Switzerland
¹²⁵ National Central University, Chung-Li, Taiwan
¹²⁶ National Taiwan University (NTU), Taipei, Taiwan
¹²⁷ High Energy Physics Research Unit, Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
¹²⁸ Physics Department, Science and Art Faculty, Çukurova University, Adana, Turkey
¹²⁹ Middle East Technical University, Physics Department, Ankara, Turkey
¹³⁰ Bogazici University, Istanbul, Turkey
¹³¹ Istanbul Technical University, Istanbul, Turkey
¹³² Istanbul University, Istanbul, Turkey
¹³³ Yildiz Technical University, Istanbul, Turkey
¹³⁴ Institute for Scintillation Materials of National Academy of Science of Ukraine, Kharkiv, Ukraine
¹³⁵ National Science Centre, Kharkiv Institute of Physics and Technology, Kharkiv, Ukraine
¹³⁶ University of Bristol, Bristol, UK
¹³⁷ Rutherford Appleton Laboratory, Didcot, UK
¹³⁸ Imperial College, London, UK
¹³⁹ Brunel University, Uxbridge, UK
¹⁴⁰ Baylor University, Waco, TX, USA
¹⁴¹ Catholic University of America, Washington, DC, USA
¹⁴² The University of Alabama, Tuscaloosa, AL, USA
¹⁴³ Boston University, Boston, MA, USA
¹⁴⁴ Brown University, Providence, RI, USA
¹⁴⁵ University of California, Davis, Davis, CA, USA
¹⁴⁶ University of California, Los Angeles, CA, USA
¹⁴⁷ University of California, Riverside, Riverside, CA, USA
¹⁴⁸ University of California, San Diego, La Jolla, CA, USA
¹⁴⁹ Department of Physics, University of California, Santa Barbara, Santa Barbara, CA, USA
¹⁵⁰ California Institute of Technology, Pasadena, CA, USA
¹⁵¹ Carnegie Mellon University, Pittsburgh, PA, USA
¹⁵² University of Colorado Boulder, Boulder, CO, USA
¹⁵³ Cornell University, Ithaca, NY, USA
¹⁵⁴ Fermi National Accelerator Laboratory, Batavia, IL, USA
¹⁵⁵ University of Florida, Gainesville, FL, USA
¹⁵⁶ Florida State University, Tallahassee, FL, USA
¹⁵⁷ Florida Institute of Technology, Melbourne, FL, USA
¹⁵⁸ University of Illinois Chicago, Chicago, USA
¹⁵⁹ The University of Iowa, Iowa City, IA, USA
¹⁶⁰ Johns Hopkins University, Baltimore, MD, USA
¹⁶¹ The University of Kansas, Lawrence, KS, USA
¹⁶² Kansas State University, Manhattan, KS, USA
¹⁶³ University of Maryland, College Park, MD, USA
¹⁶⁴ Massachusetts Institute of Technology, Cambridge, MA, USA
¹⁶⁵ University of Minnesota, Minneapolis, MN, USA
¹⁶⁶ University of Nebraska-Lincoln, Lincoln, NE, USA
¹⁶⁷ State University of New York at Buffalo, Buffalo, NY, USA
¹⁶⁸ Northeastern University, Boston, MA, USA
¹⁶⁹ Northwestern University, Evanston, IL, USA
¹⁷⁰ University of Notre Dame, Notre Dame, IN, USA
¹⁷¹ The Ohio State University, Columbus, OH, USA
¹⁷² Princeton University, Princeton, NJ, USA
¹⁷³ University of Puerto Rico, Mayaguez, PR, USA
¹⁷⁴ Purdue University, West Lafayette, IN, USA
¹⁷⁵ Purdue University Northwest, Hammond, IN, USA
¹⁷⁶ Rice University, Houston, TX, USA
¹⁷⁷ University of Rochester, Rochester, NY, USA
¹⁷⁸ Rutgers, The State University of New Jersey, Piscataway, NJ, USA
¹⁷⁹ University of Tennessee, Knoxville, TN, USA
¹⁸⁰ Texas A&M University, College Station, TX, USA
¹⁸¹ Texas Tech University, Lubbock, TX, USA
¹⁸² Vanderbilt University, Nashville, TN, USA
¹⁸³ University of Virginia, Charlottesville, VA, USA
¹⁸⁴ Wayne State University, Detroit, MI, USA
¹⁸⁵ University of Wisconsin-Madison, Madison, WI, USA
¹⁸⁶ Authors affiliated with an institute or an international laboratory covered by a cooperation agreement with CERN, Geneva, Switzerland
¹⁸⁷ Yerevan State University, Yerevan, Armenia
¹⁸⁸ TU Wien, Vienna, Austria
¹⁸⁹ Institute of Basic and Applied Sciences, Faculty of Engineering, Arab Academy for Science, Technology and Maritime Transport, Alexandria, Egypt
¹⁹⁰ Ghent University, Ghent, Belgium
¹⁹¹ Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
¹⁹² Universidade Estadual de Campinas, Campinas, Brazil
¹⁹³ Federal University of Rio Grande do Sul, Porto Alegre, Brazil
¹⁹⁴ UFMS, Nova Andradina, Brazil
¹⁹⁵ Nanjing Normal University, Nanjing, China
¹⁹⁶ The University of Iowa, Iowa City, IA, USA
¹⁹⁷ University of Chinese Academy of Sciences, Beijing, China
¹⁹⁸ China Center of Advanced Science and Technology, Beijing, China
¹⁹⁹ University of Chinese Academy of Sciences, Beijing, China
²⁰⁰ China Spallation Neutron Source, Guangdong, China
²⁰¹ Henan Normal University, Xinxiang, China
²⁰² Université Libre de Bruxelles, Bruxelles, Belgium
²⁰³ an institute or an international laboratory covered by a cooperation agreement with CERN, Geneva, Switzerland
²⁰⁴ Suez University, Suez, Egypt
²⁰⁵ British University in Egypt, Cairo, Egypt
²⁰⁶ Purdue University, West Lafayette, IN, USA
²⁰⁷ Université de Haute Alsace, Mulhouse, France
²⁰⁸ Istinye University, Istanbul, Turkey
²⁰⁹ Tbilisi State University, Tbilisi, Georgia
²¹⁰ The University of the State of Amazonas, Manaus, Brazil
²¹¹ University of Hamburg, Hamburg, Germany
²¹² RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany
²¹³ Bergische University Wuppertal (BUW), Wuppertal, Germany
²¹⁴ Brandenburg University of Technology, Cottbus, Germany
²¹⁵ Forschungszentrum Jülich, Juelich, Germany
²¹⁶ CERN, European Organization for Nuclear Research, Geneva, Switzerland
²¹⁷ Institute of Nuclear Research ATOMKI, Debrecen, Hungary
²¹⁸ Universitatea Babes-Bolyai - Facultatea de Fizica, Cluj-Napoca, Romania
²¹⁹ MTA-ELTE Lendület CMS Particle and Nuclear Physics Group, Eötvös Loránd University, Budapest, Hungary
²²⁰ HUN-REN Wigner Research Centre for Physics, Budapest, Hungary
²²¹ Physics Department, Faculty of Science, Assiut University, Assiut, Egypt
²²² Punjab Agricultural University, Ludhiana, India
²²³ University of Visva-Bharati, Santiniketan, India
²²⁴ Indian Institute of Science (IISc), Bangalore, India
²²⁵ IIT Bhubaneswar, Bhubaneswar, India
²²⁶ Institute of Physics, Bhubaneswar, India
²²⁷ University of Hyderabad, Hyderabad, India
²²⁸ Deutsches Elektronen-Synchrotron, Hamburg, Germany
²²⁹ Isfahan University of Technology, Isfahan, Iran
²³⁰ Sharif University of Technology, Tehran, Iran
²³¹ Department of Physics, University of Science and Technology of Mazandaran, Behshahr, Iran
²³² Department of Physics, Isfahan University of Technology, Isfahan, Iran
²³³ Department of Physics, Faculty of Science, Arak University, Arak, Iran
²³⁴ Helwan University, Cairo, Egypt
²³⁵ Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Bologna, Italy
²³⁶ Centro Siciliano di Fisica Nucleare e di Struttura Della Materia, Catania, Italy
²³⁷ Università degli Studi Guglielmo Marconi, Rome, Italy
²³⁸ Scuola Superiore Meridionale, Università di Napoli ’Federico II’, Naples, Italy
²³⁹ Fermi National Accelerator Laboratory, Batavia, IL, USA
²⁴⁰ Consiglio Nazionale delle Ricerche-Istituto Officina dei Materiali, Perugia, Italy
²⁴¹ Department of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Malaysia
²⁴² Consejo Nacional de Ciencia y Tecnología, Mexico City, Mexico
²⁴³ Trincomalee Campus, Eastern University, Sri Lanka, Nilaveli, Sri Lanka
²⁴⁴ Saegis Campus, Nugegoda, Sri Lanka
²⁴⁵ National and Kapodistrian University of Athens, Athens, Greece
²⁴⁶ Ecole Polytechnique Fédérale Lausanne, Lausanne, Switzerland
²⁴⁷ Universität Zürich, Zurich, Switzerland
²⁴⁸ Stefan Meyer Institute for Subatomic Physics, Vienna, Austria
²⁴⁹ Laboratoire d’Annecy-le-Vieux de Physique des Particules, IN2P3-CNRS, Annecy-le-Vieux, France
²⁵⁰ Near East University, Research Center of Experimental Health Science, Mersin, Turkey
²⁵¹ Konya Technical University, Konya, Turkey
²⁵² Izmir Bakircay University, Izmir, Turkey
²⁵³ Adiyaman University, Adiyaman, Turkey
²⁵⁴ Bozok Universitetesi Rektörlügü, Yozgat, Turkey
²⁵⁵ Marmara University, Istanbul, Turkey
²⁵⁶ Milli Savunma University, Istanbul, Turkey
²⁵⁷ Kafkas University, Kars, Turkey
²⁵⁸ Istanbul Okan University, Istanbul, Turkey
²⁵⁹ Hacettepe University, Ankara, Turkey
²⁶⁰ Erzincan Binali Yildirim University, Erzincan, Turkey
²⁶¹ Faculty of Engineering, Istanbul University-Cerrahpasa, Istanbul, Turkey
²⁶² Yildiz Technical University, Istanbul, Turkey
²⁶³ Vrije Universiteit Brussel, Brussel, Belgium
²⁶⁴ School of Physics and Astronomy, University of Southampton, Southampton, UK
²⁶⁵ IPPP Durham University, Durham, UK
²⁶⁶ Faculty of Science, Monash University, Clayton, Australia
²⁶⁷ Università di Torino, Turin, Italy
²⁶⁸ Bethel University, St. Paul, MN, USA
²⁶⁹ Karamanoğlu Mehmetbey University, Karaman, Turkey
²⁷⁰ California Institute of Technology, Pasadena, CA, USA
²⁷¹ United States Naval Academy, Annapolis, MD, USA
²⁷² Ain Shams University, Cairo, Egypt
²⁷³ Bingol University, Bingol, Turkey
²⁷⁴ Georgian Technical University, Tbilisi, Georgia
²⁷⁵ Sinop University, Sinop, Turkey
²⁷⁶ Erciyes University, Kayseri, Turkey
²⁷⁷ Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH), Bucharest, Romania
²⁷⁸ an institute or an international laboratory covered by a cooperation agreement with CERN, Geneva, Switzerland
²⁷⁹ Texas A&M University at Qatar, Doha, Qatar
²⁸⁰ Kyungpook National University, Daegu, Korea
²⁸¹ another institute or international laboratory covered by a cooperation agreement with CERN, Geneva, Switzerland
²⁸² Universiteit Antwerpen, Antwerpen, Belgium
²⁸³ Yerevan Physics Institute, Yerevan, Armenia
²⁸⁴ Northeastern University, Boston, MA, USA
²⁸⁵ Imperial College, London, UK
²⁸⁶ Institute of Nuclear Physics of the Uzbekistan Academy of Sciences, Tashkent, Uzbekistan
²⁸⁷ CERN, 1211, Geneva 23, Switzerland

^a cms-publication-committee-chair@cern.ch

Received: 19 May 2024
Accepted: 13 August 2024
Published online: 6 December 2024

Abstract

A search is reported for charge-parity $\mathit{CP}$ violation in ${\text{D}}^0\to {\text{K}}_{\text{S}}^0{\text{K}}_{\text{S}}^0$ decays, using data collected in proton–proton collisions at $\sqrt{s}=13\text{Te}\text{V}$ recorded by the CMS experiment in 2018. The analysis uses a dedicated data set that corresponds to an integrated luminosity of 41.6${\text{fb}}^{-1}$, which consists of about 10 billion events containing a pair of b hadrons, nearly all of which decay to charm hadrons. The flavor of the neutral D meson is determined by the pion charge in the reconstructed decays $\text{D}_{}^{\ast +}\to {\text{D}}^0{\mathrm{\pi }}^{+}$ and $\text{D}_{}^{\ast -}\to {\overline{\text{D}}}^0{\mathrm{\pi }}^{-}$. The $\mathit{CP}$ asymmetry in ${\text{D}}^0\to {\text{K}}_{\text{S}}^0{\text{K}}_{\text{S}}^0$ is measured to be $A_{\mathit{CP}}({\text{K}}_{\text{S}}^0{\text{K}}_{\text{S}}^0)=(6.2\pm 3.0\pm 0.2\pm 0.8)\%$, where the three uncertainties represent the statistical uncertainty, the systematic uncertainty, and the uncertainty in the measurement of the $\mathit{CP}$ asymmetry in the ${\text{D}}^0\to {\text{K}}_{\text{S}}^0{\mathrm{\pi }}^{+}{\mathrm{\pi }}^{-}$ decay. This is the first $\mathit{CP}$ asymmetry measurement by CMS in the charm sector as well as the first to utilize a fully hadronic final state.