22 páginas, 4 figuras, 1 tabla.-- et al.(ATLAS Collaboration).-- arXiv:1003.3124v2The first measurements from proton-proton collisions recorded with the ATLAS detector at the LHC are presented. Data were collected in December 2009 using a minimum-bias trigger during collisions at a centre-of-mass energy of 900 GeV. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity. and the relationship between mean transverse momentum and charged-particle multiplicity are measured for events with at least one charged particle in the kinematic range vertical bar eta vertical bar 500 MeV. The measurements are compared to Monte Carlo models of proton-proton collisions and to results from other experiments at the same centre-of-mass energy. The charged-particle multiplicity per event and unit of pseudorapidity eta = 0 is measured to be 1.333 +/- 0.003(stat.) +/- 0.040(syst.), which is 5-15% higher than the Monte Carlo models predict.We are greatly indebted to all CERN’s departments and to the LHC
project for their immense efforts not only in building the LHC, but also
for their direct contributions to the construction and installation of the ATLAS
detector and its infrastructure. All our congratulations go to the LHC
operation team for the superb performance during this initial data-taking period. We acknowledge equally warmly all our technical colleagues in the
collaborating Institutions without whom the ATLAS detector could not have
been built. Furthermore we are grateful to all the funding agencies which
supported generously the construction and the commissioning of the ATLAS
detector and also provided the computing infrastructure.
The ATLAS detector design and construction has taken about fifteen
years, and our thoughts are with all our colleagues who sadly could not see
its final realisation.
We acknowledge the support of ANPCyT, Argentina; Yerevan Physics
Institute, Armenia; ARC and DEST, Australia; Bundesministerium für Wissenschaft
und Forschung, Austria; National Academy of Sciences of Azerbaijan;
State Committee on Science & Technologies of the Republic of Belarus;
CNPq and FINEP, Brazil; NSERC, NRC, and CFI, Canada; CERN; CONICYT,
Chile; NSFC, China; COLCIENCIAS, Colombia; Ministry of Education,
Youth and Sports of the Czech Republic, Ministry of Industry and
Trade of the Czech Republic, and Committee for Collaboration of the Czech
Republic with CERN; Danish Natural Science Research Council and the
Lundbeck Foundation; European Commission, through the ARTEMIS Research
Training Network; IN2P3-CNRS and Dapnia-CEA, France; Georgian
Academy of Sciences; BMBF, HGF, DFG and MPG, Germany; Ministry of
Education and Religion, through the EPEAEK program PYTHAGORAS II
and GSRT, Greece; ISF, MINERVA, GIF, DIP, and Benoziyo Center, Israel;
INFN, Italy; MEXT, Japan; CNRST, Morocco; FOM and NWO, Netherlands;
The Research Council of Norway; Ministry of Science and Higher
Education, Poland; GRICES and FCT, Portugal; Ministry of Education and
Research, Romania; Ministry of Education and Science of the Russian Federation
and State Atomic Energy Corporation “Rosatom”; JINR; Ministry
of Science, Serbia; Department of International Science and Technology Cooperation,
Ministry of Education of the Slovak Republic; Slovenian Research
Agency, Ministry of Higher Education, Science and Technology, Slovenia;
Ministerio de Educación y Ciencia, Spain; The Swedish Research Council,
The Knut and Alice Wallenberg Foundation, Sweden; State Secretariat for
Education and Science, Swiss National Science Foundation, and Cantons of
Bern and Geneva, Switzerland; National Science Council, Taiwan; TAEK,
Turkey; The Science and Technology Facilities Council and The Leverhulme
Trust, United Kingdom; DOE and NSF, United States of America.Peer reviewe
