Eur. Phys. J. C (2025) 85: 198
https://doi.org/10.1140/epjc/s10052-025-13793-y

Regular Article - Experimental Physics

Common femtoscopic hadron-emission source in pp collisions at the LHC

¹ A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation, Yerevan, Armenia
² AGH University of Krakow, Cracow, Poland
³ Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Kiev, Ukraine
⁴ Department of Physics and Centre for Astroparticle Physics and Space Science (CAPSS), Bose Institute, Kolkata, India
⁵ California Polytechnic State University, San Luis Obispo, CA, USA
⁶ Central China Normal University, Wuhan, China
⁷ Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Havana, Cuba
⁸ Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City and Mérida, Mexico
⁹ Chicago State University, Chicago, IL, USA
¹⁰ China Institute of Atomic Energy, Beijing, China
¹¹ China University of Geosciences, Wuhan, China
¹² Chungbuk National University, Cheongju, Republic of Korea
¹³ Faculty of Mathematics, Physics and Informatics, Comenius University Bratislava, Bratislava, Slovak Republic
¹⁴ COMSATS University Islamabad, Islamabad, Pakistan
¹⁵ Creighton University, Omaha, NE, USA
¹⁶ Department of Physics, Aligarh Muslim University, Aligarh, India
¹⁷ Department of Physics, Pusan National University, Pusan, Republic of Korea
¹⁸ Department of Physics, Sejong University, Seoul, Republic of Korea
¹⁹ Department of Physics, University of California, Berkeley, CA, USA
²⁰ Department of Physics, University of Oslo, Oslo, Norway
²¹ Department of Physics and Technology, University of Bergen, Bergen, Norway
²² Dipartimento di Fisica, Università di Pavia, Pavia, Italy
²³ Dipartimento di Fisica dell’Università and Sezione INFN, Cagliari, Italy
²⁴ Dipartimento di Fisica dell’Università and Sezione INFN, Trieste, Italy
²⁵ Dipartimento di Fisica dell’Università and Sezione INFN, Turin, Italy
²⁶ Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Bologna, Italy
²⁷ Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Catania, Italy
²⁸ Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN, Padua, Italy
²⁹ Dipartimento di Fisica ‘E.R. Caianiello’ dell’Università and Gruppo Collegato INFN, Salerno, Italy
³⁰ Dipartimento DISAT del Politecnico and Sezione INFN, Turin, Italy
³¹ Dipartimento di Scienze MIFT, Università di Messina, Messina, Italy
³² Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari, Italy
³³ European Organization for Nuclear Research (CERN), Geneva, Switzerland
³⁴ Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, Split, Croatia
³⁵ Faculty of Engineering and Science, Western Norway University of Applied Sciences, Bergen, Norway
³⁶ Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague, Czech Republic
³⁷ Faculty of Physics, Sofia University, Sofia, Bulgaria
³⁸ Faculty of Science, P.J. Šafárik University, Košice, Slovak Republic
³⁹ Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany
⁴⁰ Fudan University, Shanghai, China
⁴¹ Gangneung-Wonju National University, Gangneung, Republic of Korea
⁴² Department of Physics, Gauhati University, Guwahati, India
⁴³ Helmholtz-Institut für Strahlen- und Kernphysik, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
⁴⁴ Helsinki Institute of Physics (HIP), Helsinki, Finland
⁴⁵ High Energy Physics Group, Universidad Autónoma de Puebla, Puebla, Mexico
⁴⁶ Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania
⁴⁷ HUN-REN Wigner Research Centre for Physics, Budapest, Hungary
⁴⁸ Indian Institute of Technology Bombay (IIT), Mumbai, India
⁴⁹ Indian Institute of Technology Indore, Indore, India
⁵⁰ INFN, Laboratori Nazionali di Frascati, Frascati, Italy
⁵¹ INFN, Sezione di Bari, Bari, Italy
⁵² INFN, Sezione di Bologna, Bologna, Italy
⁵³ INFN, Sezione di Cagliari, Cagliari, Italy
⁵⁴ INFN, Sezione di Catania, Catania, Italy
⁵⁵ INFN, Sezione di Padova, Padua, Italy
⁵⁶ INFN, Sezione di Pavia, Pavia, Italy
⁵⁷ INFN, Sezione di Torino, Turin, Italy
⁵⁸ INFN, Sezione di Trieste, Trieste, Italy
⁵⁹ Inha University, Incheon, Republic of Korea
⁶⁰ Institute for Gravitational and Subatomic Physics (GRASP), Utrecht University/Nikhef, Utrecht, The Netherlands
⁶¹ Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovak Republic
⁶² Institute of Physics, Homi Bhabha National Institute, Bhubaneswar, India
⁶³ Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic
⁶⁴ Institute of Space Science (ISS), Bucharest, Romania
⁶⁵ Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany
⁶⁶ Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico City, Mexico
⁶⁷ Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
⁶⁸ Instituto de Física, Universidad Nacional Autónoma de México, Mexico City, Mexico
⁶⁹ iThemba LABS, National Research Foundation, Somerset West, South Africa
⁷⁰ Jeonbuk National University, Jeonju, Republic of Korea
⁷¹ Johann-Wolfgang-Goethe Universität Frankfurt Institut für Informatik, Fachbereich Informatik und Mathematik, Frankfurt, Germany
⁷² Korea Institute of Science and Technology Information, Daejeon, Republic of Korea
⁷³ KTO Karatay University, Konya, Turkey
⁷⁴ Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-Alpes, CNRS-IN2P3, Grenoble, France
⁷⁵ Lawrence Berkeley National Laboratory, Berkeley, CA, USA
⁷⁶ Division of Particle Physics, Lund University Department of Physics, Lund, Sweden
⁷⁷ Nagasaki Institute of Applied Science, Nagasaki, Japan
⁷⁸ Nara Women’s University (NWU), Nara, Japan
⁷⁹ Department of Physics, School of Science, National and Kapodistrian University of Athens, Athens, Greece
⁸⁰ National Centre for Nuclear Research, Warsaw, Poland
⁸¹ National Institute of Science Education and Research, Homi Bhabha National Institute, Jatni, India
⁸² National Nuclear Research Center, Baku, Azerbaijan
⁸³ National Research and Innovation Agency-BRIN, Jakarta, Indonesia
⁸⁴ Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
⁸⁵ Nikhef, National Institute for Subatomic Physics, Amsterdam, The Netherlands
⁸⁶ Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, UK
⁸⁷ Nuclear Physics Institute of the Czech Academy of Sciences, Husinec-Řež, Czech Republic
⁸⁸ Oak Ridge National Laboratory, Oak Ridge, TN, USA
⁸⁹ Ohio State University, Columbus, OH, USA
⁹⁰ Physics Department, Faculty of Science, University of Zagreb, Zagreb, Croatia
⁹¹ Physics Department, Panjab University, Chandigarh, India
⁹² Physics Department, University of Jammu, Jammu, India
⁹³ Physics Program and International Institute for Sustainability with Knotted Chiral Meta Matter (SKCM2), Hiroshima University, Hiroshima, Japan
⁹⁴ Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
⁹⁵ Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
⁹⁶ Physik Department, Technische Universität München, Munich, Germany
⁹⁷ Politecnico di Bari and Sezione INFN, Bari, Italy
⁹⁸ Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany
⁹⁹ Saga University, Saga, Japan
¹⁰⁰ Saha Institute of Nuclear Physics, Homi Bhabha National Institute, Kolkata, India
¹⁰¹ School of Physics and Astronomy, University of Birmingham, Birmingham, UK
¹⁰² Sección Física, Departamento de Ciencias, Pontificia Universidad Católica del Perú, Lima, Peru
¹⁰³ Stefan Meyer Institut für Subatomare Physik (SMI), Vienna, Austria
¹⁰⁴ SUBATECH, IMT Atlantique, Nantes Université, CNRS-IN2P3, Nantes, France
¹⁰⁵ Sungkyunkwan University, Suwon City, Republic of Korea
¹⁰⁶ Suranaree University of Technology, Nakhon Ratchasima, Thailand
¹⁰⁷ Technical University of Košice, Košice, Slovak Republic
¹⁰⁸ The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland
¹⁰⁹ The University of Texas at Austin, Austin, TX, USA
¹¹⁰ Universidad Autónoma de Sinaloa, Culiacán, Mexico
¹¹¹ Universidade de São Paulo (USP), São Paulo, Brazil
¹¹² Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil
¹¹³ Universidade Federal do ABC, Santo Andre, Brazil
¹¹⁴ Universitatea Nationala de Stiinta si Tehnologie Politehnica Bucuresti, Bucharest, Romania
¹¹⁵ University of Cape Town, Cape Town, South Africa
¹¹⁶ University of Derby, Derby, UK
¹¹⁷ University of Houston, Houston, TX, USA
¹¹⁸ University of Jyväskylä, Jyväskylä, Finland
¹¹⁹ University of Kansas, Lawrence, KS, USA
¹²⁰ University of Liverpool, Liverpool, UK
¹²¹ University of Science and Technology of China, Hefei, China
¹²² University of South-Eastern Norway, Kongsberg, Norway
¹²³ University of Tennessee, Knoxville, TN, USA
¹²⁴ University of the Witwatersrand, Johannesburg, South Africa
¹²⁵ University of Tokyo, Tokyo, Japan
¹²⁶ University of Tsukuba, Tsukuba, Japan
¹²⁷ Universität Münster, Institut für Kernphysik, Münster, Germany
¹²⁸ Université Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France
¹²⁹ Université de Lyon, CNRS/IN2P3, Institut de Physique des 2 Infinis de Lyon, Lyon, France
¹³⁰ Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France, Strasbourg, France
¹³¹ Université Paris-Saclay, Centre d’Etudes de Saclay (CEA), IRFU, Départment de Physique Nucléaire (DPhN), Saclay, France
¹³² Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
¹³³ Università degli Studi di Foggia, Foggia, Italy
¹³⁴ Università del Piemonte Orientale, Vercelli, Italy
¹³⁵ Università di Brescia, Brescia, Italy
¹³⁶ Variable Energy Cyclotron Centre, Homi Bhabha National Institute, Kolkata, India
¹³⁷ Warsaw University of Technology, Warsaw, Poland
¹³⁸ Wayne State University, Detroit, MI, USA
¹³⁹ Yale University, New Haven, CT, USA
¹⁴⁰ Yonsei University, Seoul, Republic of Korea
¹⁴¹ Zentrum für Technologie und Transfer (ZTT), Worms, Germany
¹⁴² Affiliated with an Institute Covered by a Cooperation Agreement with CERN, Geneva, Switzerland
¹⁴³ Affiliated with an International Laboratory Covered by a Cooperation Agreement with CERN, Geneva, Switzerland
¹⁴⁴ Max-Planck-Institut fur Physik, Munich, Germany
¹⁴⁵ Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Bologna, Italy
¹⁴⁶ Dipartimento DET del Politecnico di Torino, Turin, Italy
¹⁴⁷ Yildiz Technical University, Istanbul, Turkey
¹⁴⁸ Department of Applied Physics, Aligarh Muslim University, Aligarh, India
¹⁴⁹ Institute of Theoretical Physics, University of Wroclaw, Poland
¹⁵⁰ An Institution Covered by a Cooperation Agreement with CERN, Geneva, Switzerland
¹⁵¹ CERN, 1211, Geneva 23, Switzerland

^a alice-publications@cern.ch

Received: 13 January 2024
Accepted: 21 May 2024
Published online: 19 February 2025

Abstract

The femtoscopic study of pairs of identical pions is particularly suited to investigate the effective source function of particle emission, due to the resulting Bose–Einstein correlation signal. In small collision systems at the LHC, pp in particular, the majority of the pions are produced in resonance decays, which significantly affect the profile and size of the source. In this work, we explicitly model this effect in order to extract the primordial source in pp collisions at $\sqrt{s}=13$ TeV from charged $\mathrm{\pi }$–$\mathrm{\pi }$ correlations measured by ALICE. We demonstrate that the assumption of a Gaussian primordial source is compatible with the data and that the effective source, resulting from modifications due to resonances, is approximately exponential, as found in previous measurements at the LHC. The universality of hadron emission in pp collisions is further investigated by applying the same methodology to characterize the primordial source of $\text{K}$–$\text{p}$ pairs. The size of the primordial source is evaluated as a function of the transverse mass ($m_{\text{T}}$) of the pairs, leading to the observation of a common scaling for both $\mathrm{\pi }$–$\mathrm{\pi }$ and $\text{K}$–$\text{p}$ , suggesting a collective effect. Further, the present results are compatible with the $m_{\text{T}}$ scaling of the $\text{p}$–$\text{p}$ and p$-\mathrm{\Lambda }$ primordial source measured by ALICE in high multiplicity pp collisions, providing additional evidence for the presence of a common emission source for all hadrons in small collision systems at the LHC. This will allow the determination of the source function for any hadron–hadron pairs with high precision, granting access to the properties of the possible final-state interaction among pairs of less abundantly produced hadrons, such as strange or charmed particles.