Constraints on the χc1 versus χc2 Polarizations in Proton-Proton Collisions at s =8 TeV

(CMS Collaboration)

doi:10.1103/PhysRevLett.124.162002

Constraints on the χc1 versus χc2 Polarizations in Proton-Proton Collisions at s =8 TeV

(CMS Collaboration)

Física

A. Alikhanian Yerevan Institute of Physics
Institut für Hochenergiephysik der OeAW
Belarusian State University
University of Antwerp
Vrije Universiteit Brussel
Université Libre de Bruxelles
Ghent University
Université catholique de Louvain
Centro Brasileiro de Pesquisas Físicas
Universidade do Estado do Rio de Janeiro
Universidade Estadual Paulista Júlio de Mesquita Filho
Universidade Federal do ABC
Bulgarian Academy of Sciences
University of Sofia
Beihang University
Tsinghua University
Institute of High Energy Physics Chinese Academy of Science
Peking University
Zhejiang University
Universidad de los Andes Colombia
Universidad de Antioquia
University of Split
Faculty of Science, University of Split
Institute Rudjer Boskovic
University of Cyprus
Charles University
Escuela Politecnica Nacional
Egyptian Network of High Energy Physics
National Institute of Chemical Physics and Biophysics, Tallinn
University of Helsinki
Helsinki Institute of Physics
Lappeenranta University of Technology
Université Paris-Saclay
Laboratoire Leprince-Ringuet
Université de Strasbourg
IN2P3-CNRS
Universite Claude Bernard Lyon 1
Georgian Technical University
Tbilisi State University
RWTH Aachen University
Deutsches Elektronen-Synchrotron (DESY)
University of Hamburg
Karlsruhe Institute of Technology
NCSR Demokritos
National and Kapodistrian University of Athens
National Technical University of Athens
University of Ioannina
Eötvös Loránd University
KFKI Research Institute for Particle and Nuclear Physics
Institute for Nuclear Research
University of Debrecen
Eszterhazy Karoly University
Indian Institute of Science
National Institute of Science Education and Research
Panjab University
University of Delhi
Saha Institute of Nuclear Physics
Indian Institute of Technology Madras
Bhabha Atomic Research Centre
Tata Institute of Fundamental Research, Mumbai
Indian Institute of Science Education and Research Pune
Institute for Research for Fundamental Sciences
University College Dublin
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Centro de Investigacion y de Estudios Avanzados del Instituto Politécnico Nacional
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University of Montenegro
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AGH University of Krakow
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Joint Institute for Nuclear Research, Dubna
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National Research Nuclear University ‘Moscow Engineering Physics Institute’ (MEPhI)
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Lomonosov Moscow State University
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ETH Zurich
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Institute for Scintillation Materials of National Academy of Science of Ukraine
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Imperial College London
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16 Scopus citations

Abstract

The polarizations of promptly produced χc1 and χc2 mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at s=8 TeV. The χc states are reconstructed via their radiative decays χc→J/ψγ, with the photons being measured through conversions to e+e-, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χc2 to χc1 yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ→μ+μ- decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum.

Original language	English
Article number	162002
Journal	Physical Review Letters
Volume	124
Issue number	16
DOIs	https://doi.org/10.1103/PhysRevLett.124.162002
State	Published - 24 Apr 2020

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10.1103/PhysRevLett.124.162002

Cite this

@article{96f66bd3d78a4d61b554c3fdd0860533,

title = "Constraints on the χc1 versus χc2 Polarizations in Proton-Proton Collisions at s =8 TeV",

abstract = "The polarizations of promptly produced χc1 and χc2 mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at s=8 TeV. The χc states are reconstructed via their radiative decays χc→J/ψγ, with the photons being measured through conversions to e+e-, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χc2 to χc1 yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ→μ+μ- decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum.",

author = "\{(CMS Collaboration)\} and Sirunyan, \{A. M.\} and A. Tumasyan and W. Adam and F. Ambrogi and T. Bergauer and M. Dragicevic and J. Er{\"o} and \{Escalante Del Valle\}, A. and M. Flechl and R. Fr{\"u}hwirth and M. Jeitler and N. Krammer and I. Kr{\"a}tschmer and D. Liko and T. Madlener and I. Mikulec and N. Rad and J. Schieck and R. Sch{\"o}fbeck and M. Spanring and W. Waltenberger and Wulz, \{C. E.\} and M. Zarucki and V. Drugakov and V. Mossolov and \{Suarez Gonzalez\}, J. and Darwish, \{M. R.\} and \{De Wolf\}, \{E. A.\} and \{Di Croce\}, D. and X. Janssen and T. Kello and A. Lelek and M. Pieters and \{Rejeb Sfar\}, H. and \{Van Haevermaet\}, H. and \{Van Mechelen\}, P. and \{Van Putte\}, S. and \{Van Remortel\}, N. and F. Blekman and Bols, \{E. S.\} and Chhibra, \{S. S.\} and J. D'Hondt and \{De Clercq\}, J. and D. Lontkovskyi and S. Lowette and I. Marchesini and S. Moortgat and Q. Python and S. Tavernier and \{Carrera Jarrin\}, E.",

note = "Publisher Copyright: {\textcopyright} 2020 CERN.",

year = "2020",

month = apr,

day = "24",

doi = "10.1103/PhysRevLett.124.162002",

language = "Ingl{\'e}s",

volume = "124",

journal = "Physical Review Letters",

issn = "0031-9007",

publisher = "American Physical Society",

number = "16",

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T1 - Constraints on the χc1 versus χc2 Polarizations in Proton-Proton Collisions at s =8 TeV

AU - (CMS Collaboration)

AU - Sirunyan, A. M.

AU - Tumasyan, A.

AU - Adam, W.

AU - Ambrogi, F.

AU - Bergauer, T.

AU - Dragicevic, M.

AU - Erö, J.

AU - Escalante Del Valle, A.

AU - Flechl, M.

AU - Frühwirth, R.

AU - Jeitler, M.

AU - Krammer, N.

AU - Krätschmer, I.

AU - Liko, D.

AU - Madlener, T.

AU - Mikulec, I.

AU - Rad, N.

AU - Schieck, J.

AU - Schöfbeck, R.

AU - Spanring, M.

AU - Waltenberger, W.

AU - Wulz, C. E.

AU - Zarucki, M.

AU - Drugakov, V.

AU - Mossolov, V.

AU - Suarez Gonzalez, J.

AU - Darwish, M. R.

AU - De Wolf, E. A.

AU - Di Croce, D.

AU - Janssen, X.

AU - Kello, T.

AU - Lelek, A.

AU - Pieters, M.

AU - Rejeb Sfar, H.

AU - Van Haevermaet, H.

AU - Van Mechelen, P.

AU - Van Putte, S.

AU - Van Remortel, N.

AU - Blekman, F.

AU - Bols, E. S.

AU - Chhibra, S. S.

AU - D'Hondt, J.

AU - De Clercq, J.

AU - Lontkovskyi, D.

AU - Lowette, S.

AU - Marchesini, I.

AU - Moortgat, S.

AU - Python, Q.

AU - Tavernier, S.

AU - Carrera Jarrin, E.

PY - 2020/4/24

Y1 - 2020/4/24

N2 - The polarizations of promptly produced χc1 and χc2 mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at s=8 TeV. The χc states are reconstructed via their radiative decays χc→J/ψγ, with the photons being measured through conversions to e+e-, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χc2 to χc1 yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ→μ+μ- decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum.

AB - The polarizations of promptly produced χc1 and χc2 mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at s=8 TeV. The χc states are reconstructed via their radiative decays χc→J/ψγ, with the photons being measured through conversions to e+e-, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χc2 to χc1 yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ→μ+μ- decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum.

UR - https://www.scopus.com/pages/publications/85084721870

U2 - 10.1103/PhysRevLett.124.162002

DO - 10.1103/PhysRevLett.124.162002

M3 - Artículo

C2 - 32383915

AN - SCOPUS:85084721870

SN - 0031-9007

VL - 124

JO - Physical Review Letters

JF - Physical Review Letters

IS - 16

M1 - 162002

ER -

Constraints on the χc1 versus χc2 Polarizations in Proton-Proton Collisions at s =8 TeV

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