https://doi.org/10.1140/epjc/s10052-010-1453-9
First measurement of the underlying event activity at the LHC with √s = 0.9 TeV
1
Yerevan Physics Institute, Yerevan, Armenia
2
Institut für Hochenergiephysik der OeAW, Wien, Austria
3
National Centre for Particle and High Energy Physics, Minsk, Belarus
4
Universiteit Antwerpen, Antwerpen, Belgium
5
Vrije Universiteit Brussel, Brussel, Belgium
6
Université Libre de Bruxelles, Bruxelles, Belgium
7
Ghent University, Ghent, Belgium
8
Université Catholique de Louvain, Louvain-la-Neuve, Belgium
9
Université de Mons, Mons, Belgium
10
Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil
11
Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
12
Instituto de Fisica Teorica, Universidade Estadual Paulista, Sao Paulo, Brazil
13
Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria
14
University of Sofia, Sofia, Bulgaria
15
Institute of High Energy Physics, Beijing, China
16
State Key Lab. of Nucl. Phys. and Tech., Peking University, Beijing, China
17
Universidad de Los Andes, Bogota, Colombia
18
Technical University of Split, Split, Croatia
19
University of Split, Split, Croatia
20
Institute Rudjer Boskovic, Zagreb, Croatia
21
University of Cyprus, Nicosia, Cyprus
22
Egyptian Network of High Energy Physics, Academy of Scientific Research and Technology of the Arab Republic of Egypt, Cairo, Egypt
23
National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
24
Department of Physics, University of Helsinki, Helsinki, Finland
25
Helsinki Institute of Physics, Helsinki, Finland
26
Lappeenranta University of Technology, Lappeenranta, Finland
27
Laboratoire d’Annecy-le-Vieux de Physique des Particules, IN2P3-CNRS, Annecy-le-Vieux, France
28
DSM/IRFU, CEA/Saclay, Gif-sur-Yvette, France
29
Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France
30
Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Université de Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France
31
Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique des Particules (IN2P3), Villeurbanne, France
32
CNRS-IN2P3, Institut de Physique Nucléaire de Lyon, Université de Lyon, Université Claude Bernard Lyon 1, Villeurbanne, France
33
E. Andronikashvili Institute of Physics, Academy of Science, Tbilisi, Georgia
34
I. Physikalisches Institut, RWTH Aachen University, Aachen, Germany
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III. Physikalisches Institut A, RWTH Aachen University, Aachen, Germany
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III. Physikalisches Institut B, RWTH Aachen University, Aachen, Germany
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Deutsches Elektronen-Synchrotron, Hamburg, Germany
38
University of Hamburg, Hamburg, Germany
39
Institut für Experimentelle Kernphysik, Karlsruhe, Germany
40
Institute of Nuclear Physics “Demokritos”, Aghia Paraskevi, Greece
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University of Athens, Athens, Greece
42
University of Ioánnina, Ioánnina, Greece
43
KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary
44
Institute of Nuclear Research ATOMKI, Debrecen, Hungary
45
University of Debrecen, Debrecen, Hungary
46
Panjab University, Chandigarh, India
47
University of Delhi, Delhi, India
48
Bhabha Atomic Research Centre, Mumbai, India
49
Tata Institute of Fundamental Research - EHEP, Mumbai, India
50
Tata Institute of Fundamental Research - HECR, Mumbai, India
51
Institute for Studies in Theoretical Physics & Mathematics (IPM), Tehran, Iran
52
INFN Sezione di Bari, Bari, Italy
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Università di Bari, Bari, Italy
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Politecnico di Bari, Bari, Italy
55
INFN Sezione di Bologna, Bologna, Italy
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Università di Bologna, Bologna, Italy
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INFN Sezione di Catania, Catania, Italy
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Università di Catania, Catania, Italy
59
INFN Sezione di Firenze, Firenze, Italy
60
Università di Firenze, Firenze, Italy
61
INFN Laboratori Nazionali di Frascati, Frascati, Italy
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INFN Sezione di Genova, Genova, Italy
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INFN Sezione di Milano-Biccoca, Milano, Italy
64
Università di Milano-Bicocca, Milano, Italy
65
INFN Sezione di Napoli, Napoli, Italy
66
Università di Napoli “Federico II”, Napoli, Italy
67
INFN Sezione di Padova, Padova, Italy
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Università di Padova, Padova, Italy
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Università di Trento (Trento), Padova, Italy
70
INFN Sezione di Pavia, Pavia, Italy
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Università di Pavia, Pavia, Italy
72
INFN Sezione di Perugia, Perugia, Italy
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Università di Perugia, Perugia, Italy
74
INFN Sezione di Pisa, Pisa, Italy
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Università di Pisa, Pisa, Italy
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Scuola Normale Superiore di Pisa, Pisa, Italy
77
INFN Sezione di Roma, Roma, Italy
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Università di Roma “La Sapienza”, Roma, Italy
79
INFN Sezione di Torino, Torino, Italy
80
Università di Torino, Torino, Italy
81
Università del Piemonte Orientale (Novara), Torino, Italy
82
INFN Sezione di Trieste, Trieste, Italy
83
Università di Trieste, Trieste, Italy
84
Kyungpook National University, Daegu, Korea
85
Institute for Universe and Elementary Particles, Chonnam National University, Kwangju, Korea
86
Korea University, Seoul, Korea
87
University of Seoul, Seoul, Korea
88
Sungkyunkwan University, Suwon, Korea
89
Vilnius University, Vilnius, Lithuania
90
Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico
91
Universidad Iberoamericana, Mexico City, Mexico
92
Benemerita Universidad Autonoma de Puebla, Puebla, Mexico
93
Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
94
University of Auckland, Auckland, New Zealand
95
University of Canterbury, Christchurch, New Zealand
96
National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan
97
Institute of Experimental Physics, Warsaw, Poland
98
Soltan Institute for Nuclear Studies, Warsaw, Poland
99
Laboratório de Instrumentaç ao e Física Experimental de Partículas, Lisboa, Portugal
100
Joint Institute for Nuclear Research, Dubna, Russia
101
Petersburg Nuclear Physics Institute, Gatchina (St Petersburg), Russia
102
Institute for Nuclear Research, Moscow, Russia
103
Institute for Theoretical and Experimental Physics, Moscow, Russia
104
Moscow State University, Moscow, Russia
105
P.N. Lebedev Physical Institute, Moscow, Russia
106
Institute for High Energy Physics, State Research Center of Russian Federation, Protvino, Russia
107
Faculty of Physics and Vinca Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia
108
Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain
109
Universidad Autónoma de Madrid, Madrid, Spain
110
Universidad de Oviedo, Oviedo, Spain
111
Instituto de Física de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain
112
CERN, European Organization for Nuclear Research, Geneva, Switzerland
113
Paul Scherrer Institut, Villigen, Switzerland
114
Institute for Particle Physics, ETH Zurich, Zurich, Switzerland
115
Universität Zürich, Zurich, Switzerland
116
National Central University, Chung-Li, Taiwan
117
National Taiwan University (NTU), Taipei, Taiwan
118
Cukurova University, Adana, Turkey
119
Physics Department, Middle East Technical University, Ankara, Turkey
120
Department of Physics, Bogaziçi University, Istanbul, Turkey
121
Kharkov Institute of Physics and Technology, National Scientific Center, Kharkov, Ukraine
122
University of Bristol, Bristol, UK
123
Rutherford Appleton Laboratory, Didcot, UK
124
Imperial College, University of London, London, UK
125
Brunel University, Uxbridge, UK
126
Boston University, Boston, USA
127
Brown University, Providence, USA
128
University of California, Davis, Davis, USA
129
University of California, Los Angeles, Los Angeles, USA
130
University of California, Riverside, Riverside, USA
131
University of California, San Diego, La Jolla, USA
132
University of California, Santa Barbara, Santa Barbara, USA
133
California Institute of Technology, Pasadena, USA
134
Carnegie Mellon University, Pittsburgh, USA
135
University of Colorado at Boulder, Boulder, USA
136
Cornell University, Ithaca, USA
137
Fairfield University, Fairfield, USA
138
Fermi National Accelerator Laboratory, Batavia, USA
139
University of Florida, Gainesville, USA
140
Florida International University, Miami, USA
141
Florida State University, Tallahassee, USA
142
Florida Institute of Technology, Melbourne, USA
143
University of Illinois at Chicago (UIC), Chicago, USA
144
The University of Iowa, Iowa City, USA
145
Johns Hopkins University, Baltimore, USA
146
The University of Kansas, Lawrence, USA
147
Kansas State University, Manhattan, USA
148
Lawrence Livermore National Laboratory, Livermore, USA
149
University of Maryland, College Park, USA
150
Massachusetts Institute of Technology, Cambridge, USA
151
University of Minnesota, Minneapolis, USA
152
University of Mississippi, University, USA
153
University of Nebraska-Lincoln, Lincoln, USA
154
State University of New York at Buffalo, Buffalo, USA
155
Northeastern University, Boston, USA
156
Northwestern University, Evanston, USA
157
University of Notre Dame, Notre Dame, USA
158
The Ohio State University, Columbus, USA
159
Princeton University, Princeton, USA
160
University of Puerto Rico, Mayaguez, USA
161
Purdue University, West Lafayette, USA
162
Purdue University Calumet, Hammond, USA
163
Rice University, Houston, USA
164
University of Rochester, Rochester, USA
165
The Rockefeller University, New York, USA
166
Rutgers, the State University of New Jersey, Piscataway, USA
167
University of Tennessee, Knoxville, USA
168
Texas A&M University, College Station, USA
169
Texas Tech University, Lubbock, USA
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Vanderbilt University, Nashville, USA
171
University of Virginia, Charlottesville, USA
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Wayne State University, Detroit, USA
173
University of Wisconsin, Madison, USA
cms-publication-committee-chair@cern.ch
Received:
10
June
2010
Revised:
3
September
2010
Published online:
6
November
2010
A measurement of the underlying activity in scattering processes with p
T
scale in the GeV region is performed in proton–proton collisions at 
TeV, using data collected by the CMS experiment at the LHC. Charged particle production is studied with reference to the direction of a leading object, either a charged particle or a set of charged particles forming a jet. Predictions of several QCD-inspired models as implemented in PYTHIA are compared, after full detector simulation, to the data. The models generally predict too little production of charged particles with pseudorapidity |η|<2, p
T
>0.5 GeV/c, and azimuthal direction transverse to that of the leading object.
© Springer-Verlag / Società Italiana di Fisica, 2010
