Eur. Phys. J. C (2016) 76: 635
https://doi.org/10.1140/epjc/s10052-016-4450-9

Regular Article - Experimental Physics

Multiplicity and transverse momentum fluctuations in inelastic proton–proton interactions at the CERN Super Proton Synchrotron

¹ National Nuclear Research Center, Baku, Azerbaijan
² Faculty of Physics, University of Sofia, Sofia, Bulgaria
³ Ruđer Bošković Institute, Zagreb, Croatia
⁴ LPNHE, University of Paris VI and VII, Paris, France
⁵ Karlsruhe Institute of Technology, Karlsruhe, Germany
⁶ Fachhochschule Frankfurt, Frankfurt, Germany
⁷ University of Frankfurt, Frankfurt, Germany
⁸ University of Athens, Athens, Greece
⁹ Wigner Research Centre for Physics of the Hungarian Academy of Sciences, Budapest, Hungary
¹⁰ Institute for Particle and Nuclear Studies, KEK, Tsukuba, Japan
¹¹ University of Bergen, Bergen, Norway
¹² Jan Kochanowski University in Kielce, Kielce, Poland
¹³ National Center for Nuclear Research, Warsaw, Poland
¹⁴ Jagiellonian University, Cracow, Poland
¹⁵ University of Silesia, Katowice, Poland
¹⁶ Faculty of Physics, University of Warsaw, Warsaw, Poland
¹⁷ University of Wrocław, Wrocław, Poland
¹⁸ Warsaw University of Technology, Warsaw, Poland
¹⁹ Institute for Nuclear Research, Moscow, Russia
²⁰ Joint Institute for Nuclear Research, Dubna, Russia
²¹ St. Petersburg State University, St. Petersburg, Russia
²² University of Belgrade, Belgrade, Serbia
²³ ETH Zürich, Zurich, Switzerland
²⁴ University of Bern, Bern, Switzerland
²⁵ University of Geneva, Geneva, Switzerland

^* e-mail: tobiasz.czopowicz@cern.ch

Received: 16 October 2015
Accepted: 22 August 2016
Published online: 21 November 2016

Abstract

Measurements of multiplicity and transverse momentum fluctuations of charged particles were performed in inelastic p+p interactions at 20, 31, 40, 80, and 158  beam momentum. Results for the scaled variance of the multiplicity distribution and for three strongly intensive measures of multiplicity and transverse momentum fluctuations , and are presented. For the first time the results on fluctuations are fully corrected for experimental biases. The results on multiplicity and transverse momentum fluctuations significantly deviate from expectations for the independent particle production. They also depend on charges of selected hadrons. The string-resonance Monte Carlo models Epos and Urqmd do not describe the data. The scaled variance of multiplicity fluctuations is significantly higher in inelastic p+p interactions than in central Pb+Pb collisions measured by NA49 at the same energy per nucleon. This is in qualitative disagreement with the predictions of the Wounded Nucleon Model. Within the statistical framework the enhanced multiplicity fluctuations in inelastic p+p interactions can be interpreted as due to event-by-event fluctuations of the fireball energy and/or volume.