https://doi.org/10.1140/epjc/s10052-017-4819-4
Regular Article - Experimental Physics
Measurement of the W boson polarisation in 
events from pp collisions at 
= 8 TeV in the lepton + jets channel with ATLAS
1
Department of Physics, University of Adelaide, Adelaide, Australia
2
Physics Department, SUNY Albany, Albany, NY, USA
3
Department of Physics, University of Alberta, Edmonton, AB, Canada
4
Department of Physics, Ankara University, Ankara, Turkey
5
Istanbul Aydin University, Istanbul, Turkey
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Division of Physics, TOBB University of Economics and Technology, Ankara, Turkey
7
LAPP, CNRS/IN2P3 and Université Savoie Mont Blanc, Annecy-le-Vieux, France
8
High Energy Physics Division, Argonne National Laboratory, Argonne, IL, USA
9
Department of Physics, University of Arizona, Tucson, AZ, USA
10
Department of Physics, The University of Texas at Arlington, Arlington, TX, USA
11
Physics Department, National and Kapodistrian University of Athens, Athens, Greece
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Physics Department, National Technical University of Athens, Zografou, Greece
13
Department of Physics, The University of Texas at Austin, Austin, TX, USA
14
Institute of Physics, Azerbaijan Academy of Sciences, Baku, Azerbaijan
15
Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Barcelona, Spain
16
Institute of Physics, University of Belgrade, Belgrade, Serbia
17
Department for Physics and Technology, University of Bergen, Bergen, Norway
18
Physics Division, Lawrence Berkeley National Laboratory and University of California, Berkeley, CA, USA
19
Department of Physics, Humboldt University, Berlin, Germany
20
Albert Einstein Center for Fundamental Physics and Laboratory for High Energy Physics, University of Bern, Bern, Switzerland
21
School of Physics and Astronomy, University of Birmingham, Birmingham, UK
22
Department of Physics, Bogazici University, Istanbul, Turkey
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Department of Physics Engineering, Gaziantep University, Gaziantep, Turkey
24
Faculty of Engineering and Natural Sciences, Istanbul Bilgi University, Istanbul, Turkey
25
Faculty of Engineering and Natural Sciences, Bahcesehir University, Istanbul, Turkey
26
Centro de Investigaciones, Universidad Antonio Narino, Bogota, Colombia
27
INFN Sezione di Bologna, Bologna, Italy
28
Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna, Italy
29
Physikalisches Institut, University of Bonn, Bonn, Germany
30
Department of Physics, Boston University, Boston, MA, USA
31
Department of Physics, Brandeis University, Waltham, MA, USA
32
Universidade Federal do Rio De Janeiro COPPE/EE/IF, Rio de Janeiro, Brazil
33
Electrical Circuits Department, Federal University of Juiz de Fora (UFJF), Juiz de Fora, Brazil
34
Federal University of Sao Joao del Rei (UFSJ), São João del Rei, Brazil
35
Instituto de Fisica, Universidade de Sao Paulo, São Paulo, Brazil
36
Physics Department, Brookhaven National Laboratory, Upton, NY, USA
37
Transilvania University of Brasov, Brasov, Romania
38
National Institute of Physics and Nuclear Engineering, Bucharest, Romania
39
Physics Department, National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca, Romania
40
University Politehnica Bucharest, Bucharest, Romania
41
West University in Timisoara, Timisoara, Romania
42
Departamento de Física, Universidad de Buenos Aires, Buenos Aires, Argentina
43
Cavendish Laboratory, University of Cambridge, Cambridge, UK
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Department of Physics, Carleton University, Ottawa, ON, Canada
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CERN, Geneva, Switzerland
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Enrico Fermi Institute, University of Chicago, Chicago, IL, USA
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Departamento de Física, Pontificia Universidad Católica de Chile, Santiago, Chile
48
Departamento de Física, Universidad Técnica Federico Santa María, Valparaíso, Chile
49
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
50
Department of Physics, Nanjing University, Jiangsu, China
51
Physics Department, Tsinghua University, Beijing, 100084, China
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Department of Modern Physics, University of Science and Technology of China, Anhui, China
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School of Physics, Shandong University, Shandong, China
54
Department of Physics and Astronomy, Shanghai Key Laboratory for Particle Physics and Cosmology, Shanghai Jiao Tong University (also affiliated with PKU-CHEP), Shanghai, China
55
Laboratoire de Physique Corpusculaire, Université Clermont Auvergne, Université Blaise Pascal, CNRS/IN2P3, Clermont-Ferrand, France
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Nevis Laboratory, Columbia University, Irvington, NY, USA
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Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
58
INFN Gruppo Collegato di Cosenza, Laboratori Nazionali di Frascati, Frascati, Italy
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Dipartimento di Fisica, Università della Calabria, Rende, Italy
60
Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Kraków, Poland
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Marian Smoluchowski Institute of Physics, Jagiellonian University, Kraków, Poland
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Institute of Nuclear Physics, Polish Academy of Sciences, Kraków, Poland
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Physics Department, Southern Methodist University, Dallas, TX, USA
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Physics Department, University of Texas at Dallas, Richardson, TX, USA
65
DESY, Hamburg and Zeuthen, Germany
66
Lehrstuhl für Experimentelle Physik IV, Technische Universität Dortmund, Dortmund, Germany
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Institut für Kern- und Teilchenphysik, Technische Universität Dresden, Dresden, Germany
68
Department of Physics, Duke University, Durham, NC, USA
69
SUPA-School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
70
INFN Laboratori Nazionali di Frascati, Frascati, Italy
71
Fakultät für Mathematik und Physik, Albert-Ludwigs-Universität, Freiburg, Germany
72
Departement de Physique Nucleaire et Corpusculaire, Université de Genève, Geneva, Switzerland
73
INFN Sezione di Genova, Genoa, Italy
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Dipartimento di Fisica, Università di Genova, Genoa, Italy
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E. Andronikashvili Institute of Physics, Iv. Javakhishvili Tbilisi State University, Tbilisi, Georgia
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High Energy Physics Institute, Tbilisi State University, Tbilisi, Georgia
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II Physikalisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany
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SUPA-School of Physics and Astronomy, University of Glasgow, Glasgow, UK
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II Physikalisches Institut, Georg-August-Universität, Göttingen, Germany
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Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-Alpes, CNRS/IN2P3, Grenoble, France
81
Laboratory for Particle Physics and Cosmology, Harvard University, Cambridge, MA, USA
82
Kirchhoff-Institut für Physik, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
83
Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
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ZITI Institut für technische Informatik, Ruprecht-Karls-Universität Heidelberg, Mannheim, Germany
85
Faculty of Applied Information Science, Hiroshima Institute of Technology, Hiroshima, Japan
86
Department of Physics, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
87
Department of Physics, The University of Hong Kong, Hong Kong, China
88
Department of Physics and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
89
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
90
Department of Physics, Indiana University, Bloomington, IN, USA
91
Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität, Innsbruck, Austria
92
University of Iowa, Iowa City, IA, USA
93
Department of Physics and Astronomy, Iowa State University, Ames, IA, USA
94
Joint Institute for Nuclear Research, JINR Dubna, Dubna, Russia
95
KEK, High Energy Accelerator Research Organization, Tsukuba, Japan
96
Graduate School of Science, Kobe University, Kobe, Japan
97
Faculty of Science, Kyoto University, Kyoto, Japan
98
Kyoto University of Education, Kyoto, Japan
99
Department of Physics, Kyushu University, Fukuoka, Japan
100
Instituto de Física La Plata, Universidad Nacional de La Plata and CONICET, La Plata, Argentina
101
Physics Department, Lancaster University, Lancaster, UK
102
INFN Sezione di Lecce, Lecce, Italy
103
Dipartimento di Matematica e Fisica, Università del Salento, Lecce, Italy
104
Oliver Lodge Laboratory, University of Liverpool, Liverpool, UK
105
Department of Experimental Particle Physics, Jožef Stefan Institute and Department of Physics, University of Ljubljana, Ljubljana, Slovenia
106
School of Physics and Astronomy, Queen Mary University of London, London, UK
107
Department of Physics, Royal Holloway University of London, Surrey, UK
108
Department of Physics and Astronomy, University College London, London, UK
109
Louisiana Tech University, Ruston, LA, USA
110
Laboratoire de Physique Nucléaire et de Hautes Energies, UPMC and Université Paris-Diderot and CNRS/IN2P3, Paris, France
111
Fysiska institutionen, Lunds universitet, Lund, Sweden
112
Departamento de Fisica Teorica C-15, Universidad Autonoma de Madrid, Madrid, Spain
113
Institut für Physik, Universität Mainz, Mainz, Germany
114
School of Physics and Astronomy, University of Manchester, Manchester, UK
115
CPPM, Aix-Marseille Université and CNRS/IN2P3, Marseille, France
116
Department of Physics, University of Massachusetts, Amherst, MA, USA
117
Department of Physics, McGill University, Montreal, QC, Canada
118
School of Physics, University of Melbourne, Melbourne, VIC, Australia
119
Department of Physics, The University of Michigan, Ann Arbor, MI, USA
120
Department of Physics and Astronomy, Michigan State University, East Lansing, MI, USA
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INFN Sezione di Milano, Milan, Italy
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Dipartimento di Fisica, Università di Milano, Milan, Italy
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B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk, Republic of Belarus
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Research Institute for Nuclear Problems of Byelorussian State University, Minsk, Republic of Belarus
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Group of Particle Physics, University of Montreal, Montreal, QC, Canada
126
P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russia
127
Institute for Theoretical and Experimental Physics (ITEP), Moscow, Russia
128
National Research Nuclear University MEPhI, Moscow, Russia
129
D.V. Skobeltsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, Moscow, Russia
130
Fakultät für Physik, Ludwig-Maximilians-Universität München, Munich, Germany
131
Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Munich, Germany
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Nagasaki Institute of Applied Science, Nagasaki, Japan
133
Graduate School of Science and Kobayashi-Maskawa Institute, Nagoya University, Nagoya, Japan
134
INFN Sezione di Napoli, Naples, Italy
135
Dipartimento di Fisica, Università di Napoli, Naples, Italy
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Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM, USA
137
Institute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen/Nikhef, Nijmegen, Netherlands
138
Nikhef National Institute for Subatomic Physics and University of Amsterdam, Amsterdam, Netherlands
139
Department of Physics, Northern Illinois University, DeKalb, IL, USA
140
Budker Institute of Nuclear Physics, SB RAS, Novosibirsk, Russia
141
Department of Physics, New York University, New York, NY, USA
142
Ohio State University, Columbus, OH, USA
143
Faculty of Science, Okayama University, Okayama, Japan
144
Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK, USA
145
Department of Physics, Oklahoma State University, Stillwater, OK, USA
146
Palacký University, RCPTM, Olomouc, Czech Republic
147
Center for High Energy Physics, University of Oregon, Eugene, OR, USA
148
LAL, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, France
149
Graduate School of Science, Osaka University, Osaka, Japan
150
Department of Physics, University of Oslo, Oslo, Norway
151
Department of Physics, Oxford University, Oxford, UK
152
INFN Sezione di Pavia, Pavia, Italy
153
Dipartimento di Fisica, Università di Pavia, Pavia, Italy
154
Department of Physics, University of Pennsylvania, Philadelphia, PA, USA
155
National Research Centre “Kurchatov Institute” B.P. Konstantinov Petersburg Nuclear Physics Institute, St. Petersburg, Russia
156
INFN Sezione di Pisa, Pisa, Italy
157
Dipartimento di Fisica E. Fermi, Università di Pisa, Pisa, Italy
158
Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, USA
159
Laboratório de Instrumentação e Física Experimental de Partículas-LIP, Lisbon, Portugal
160
Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
161
Department of Physics, University of Coimbra, Coimbra, Portugal
162
Centro de Física Nuclear da Universidade de Lisboa, Lisbon, Portugal
163
Departamento de Fisica, Universidade do Minho, Braga, Portugal
164
Departamento de Fisica Teorica y del Cosmos and CAFPE, Universidad de Granada, Granada, Spain
165
Dep Fisica and CEFITEC of Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
166
Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
167
Czech Technical University in Prague, Prague, Czech Republic
168
Faculty of Mathematics and Physics, Charles University in Prague, Prague, Czech Republic
169
State Research Center Institute for High Energy Physics (Protvino), NRC KI, Protvino, Russia
170
Particle Physics Department, Rutherford Appleton Laboratory, Didcot, UK
171
INFN Sezione di Roma, Rome, Italy
172
Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy
173
INFN Sezione di Roma Tor Vergata, Rome, Italy
174
Dipartimento di Fisica, Università di Roma Tor Vergata, Rome, Italy
175
INFN Sezione di Roma Tre, Rome, Italy
176
Dipartimento di Matematica e Fisica, Università Roma Tre, Rome, Italy
177
Faculté des Sciences Ain Chock, Réseau Universitaire de Physique des Hautes Energies-Université Hassan II, Casablanca, Morocco
178
Centre National de l’Energie des Sciences Techniques Nucleaires, Rabat, Morocco
179
Faculté des Sciences Semlalia, Université Cadi Ayyad, LPHEA-Marrakech, Marrakech, Morocco
180
Faculté des Sciences, Université Mohamed Premier and LPTPM, Oujda, Morocco
181
Faculté des Sciences, Université Mohammed V, Rabat, Morocco
182
DSM/IRFU (Institut de Recherches sur les Lois Fondamentales de l’Univers), CEA Saclay (Commissariat à l’Energie Atomique et aux Energies Alternatives), Gif-sur-Yvette, France
183
Santa Cruz Institute for Particle Physics, University of California Santa Cruz, Santa Cruz, CA, USA
184
Department of Physics, University of Washington, Seattle, WA, USA
185
Department of Physics and Astronomy, University of Sheffield, Sheffield, UK
186
Department of Physics, Shinshu University, Nagano, Japan
187
Fachbereich Physik, Universität Siegen, Siegen, Germany
188
Department of Physics, Simon Fraser University, Burnaby, BC, Canada
189
SLAC National Accelerator Laboratory, Stanford, CA, USA
190
Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovak Republic
191
Department of Subnuclear Physics, Institute of Experimental Physics of the Slovak Academy of Sciences, Kosice, Slovak Republic
192
Department of Physics, University of Cape Town, Cape Town, South Africa
193
Department of Physics, University of Johannesburg, Johannesburg, South Africa
194
School of Physics, University of the Witwatersrand, Johannesburg, South Africa
195
Department of Physics, Stockholm University, Stockholm, Sweden
196
The Oskar Klein Centre, Stockholm, Sweden
197
Physics Department, Royal Institute of Technology, Stockholm, Sweden
198
Departments of Physics and Astronomy and Chemistry, Stony Brook University, Stony Brook, NY, USA
199
Department of Physics and Astronomy, University of Sussex, Brighton, UK
200
School of Physics, University of Sydney, Sydney, Australia
201
Institute of Physics, Academia Sinica, Taipei, Taiwan
202
Department of Physics, Technion: Israel Institute of Technology, Haifa, Israel
203
Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel
204
Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece
205
International Center for Elementary Particle Physics and Department of Physics, The University of Tokyo, Tokyo, Japan
206
Graduate School of Science and Technology, Tokyo Metropolitan University, Tokyo, Japan
207
Department of Physics, Tokyo Institute of Technology, Tokyo, Japan
208
Tomsk State University, Tomsk, Russia
209
Department of Physics, University of Toronto, Toronto, ON, Canada
210
INFN-TIFPA, Trento, Italy
211
University of Trento, Trento, Italy
212
TRIUMF, Vancouver, BC, Canada
213
Department of Physics and Astronomy, York University, Toronto, ON, Canada
214
Faculty of Pure and Applied Sciences, and Center for Integrated Research in Fundamental Science and Engineering, University of Tsukuba, Tsukuba, Japan
215
Department of Physics and Astronomy, Tufts University, Medford, MA, USA
216
Department of Physics and Astronomy, University of California Irvine, Irvine, CA, USA
217
INFN Gruppo Collegato di Udine, Sezione di Trieste, Udine, Italy
218
ICTP, Trieste, Italy
219
Dipartimento di Chimica, Fisica e Ambiente, Università di Udine, Udine, Italy
220
Department of Physics and Astronomy, University of Uppsala, Uppsala, Sweden
221
Department of Physics, University of Illinois, Urbana, IL, USA
222
Instituto de Fisica Corpuscular (IFIC) and Departamento de Fisica Atomica, Molecular y Nuclear and Departamento de Ingeniería Electrónica and Instituto de Microelectrónica de Barcelona (IMB-CNM), University of Valencia and CSIC, Valencia, Spain
223
Department of Physics, University of British Columbia, Vancouver, BC, Canada
224
Department of Physics and Astronomy, University of Victoria, Victoria, BC, Canada
225
Department of Physics, University of Warwick, Coventry, UK
226
Waseda University, Tokyo, Japan
227
Department of Particle Physics, The Weizmann Institute of Science, Rehovot, Israel
228
Department of Physics, University of Wisconsin, Madison, WI, USA
229
Fakultät für Physik und Astronomie, Julius-Maximilians-Universität, Würzburg, Germany
230
Fakultät für Mathematik und Naturwissenschaften, Fachgruppe Physik, Bergische Universität Wuppertal, Wuppertal, Germany
231
Department of Physics, Yale University, New Haven, CT, USA
232
Yerevan Physics Institute, Yerevan, Armenia
233
Centre de Calcul de l’Institut National de Physique Nucléaire et de Physique des Particules (IN2P3), Villeurbanne, France
234
CERN, 1211, Geneva 23, Switzerland
* e-mail: atlas.publications@cern.ch
Received:
9
December
2016
Accepted:
11
April
2017
Published online:
26
April
2017
This paper presents a measurement of the polarisation of W bosons from decays, reconstructed in events with one high-
lepton and at least four jets. Data from pp collisions at the LHC were collected at = 8 TeV and correspond to an integrated luminosity of 20.2 fb
. The angle 
between the b-quark from the top quark decay and a direct W boson decay product in the W boson rest frame is sensitive to the W boson polarisation. Two different W decay products are used as polarisation analysers: the charged lepton and the down-type quark for the leptonically and hadronically decaying W boson, respectively. The most precise measurement of the W boson polarisation via the distribution of 
is obtained using the leptonic analyser and events in which at least two of the jets are tagged as b-quark jets. The fitted fractions of longitudinal, left- and right-handed polarisation states are 
, 
and 
, and are the most precisely measured W boson polarisation fractions to date. Limits on anomalous couplings of the Wtb vertex are set.
© CERN for the benefit of the ATLAS collaboration, 2017
