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)

Department of Physics Engineering

Research output: Contribution to journal › Article › peer-review

14 Citations (Scopus)

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
Publication status	Published - 24 Apr 2020

Bibliographical note

Publisher Copyright:
© 2020 CERN.

Funding

We congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC and thank the technical and administrative staffs at CERN and at other CMS institutes for their contributions to the success of the CMS effort. In addition, we gratefully acknowledge the computing centers and personnel of the Worldwide LHC Computing Grid for delivering so effectively the computing infrastructure essential to our analyses. Finally, we acknowledge the enduring support for the construction and operation of the LHC and the CMS detector provided by the following funding agencies: BMBWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, FAPERGS, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES and CSF (Croatia); RPF (Cyprus); SENESCYT (Ecuador); MoER, ERC IUT, PUT and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); NKFIA (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); MES (Latvia); LAS (Lithuania); MOE and UM (Malaysia); BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MOS (Montenegro); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS, RFBR, and NRC KI (Russia); MESTD (Serbia); SEIDI, CPAN, PCTI, and FEDER (Spain); MOSTR (Sri Lanka); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA).

Funders	Funder number
CPAN
ERC IUT
LNS
MESTD
MON
MSES
MSHE
MoER
PCTI
STAR
Swiss Funding Agencies
TUBITAK
UASLP-FAI
National Science Foundation
U.S. Department of Energy
Hispanics in Philanthropy
Maryland Ornithological Society
Departamento Administrativo de Ciencia, Tecnología e Innovación (COLCIENCIAS)
Secretaría de Educación Pública
Türkiye Atom Enerjisi Kurumu
Louisiana Academy of Sciences
Missouri University of Science and Technology
CERN
Thailand Center of Excellence in Physics
Cosmetic Surgery Foundation
Institute for the Promotion of Teaching Science and Technology
Science and Technology Facilities Council	GRIDPP
Department of Science and Technology, Ministry of Science and Technology, India
Ministry of Education - Singapore
Department of Atomic Energy, Government of India
Science Foundation Ireland
Helmholtz-Gemeinschaft
Deutsche Forschungsgemeinschaft
Fundação de Amparo à Pesquisa do Estado de São Paulo
National Natural Science Foundation of China
Research Promotion Foundation
National Science Council
Fundação para a Ciência e a Tecnologia
Russian Foundation for Basic Research
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Academy of Finland
Bundesministerium für Bildung und Forschung
Chinese Academy of Sciences
Austrian Science Fund
Fonds De La Recherche Scientifique - FNRS
Russian Academy of Sciences
Fonds Wetenschappelijk Onderzoek
Consejo Nacional de Ciencia y Tecnología
Ministerio de Economía y Competitividad
General Secretariat for Research and Technology
Ministry of Business, Innovation and Employment
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Ministry of Science, ICT and Future Planning
National Research Foundation of Korea
Joint Institute for Nuclear Research
Instituto Nazionale di Fisica Nucleare
National Science and Technology Development Agency	Thailand
Politechnika Poznańska
Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul
Secretaría de Educación Superior, Ciencia, Tecnología e Innovación
Universiti Malaya
Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro
Ministry of Science and Technology, Taiwan
National Academy of Sciences of Ukraine
Centre National de la Recherche Scientifique
Ministry of Education and Science
Institute for Research in Fundamental Sciences
Benemérita Universidad Autónoma de Puebla
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
Secretaría de Estado de Investigación, Desarrollo e Innovación
European Regional Development Fund
State Atomic Energy Corporation ROSATOM
Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional
Pakistan Atomic Energy Commission
Ministry of Science,Technology and Research
Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie
Institut National de Physique Nucléaire et de Physique des Particules
Nemzeti Kutatási, Fejlesztési és Innovaciós Alap
National Research Center "Kurchatov Institute"

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10.1103/PhysRevLett.124.162002

Cite this

@article{ead4bc750ba1416286de7c1053365f76,

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 A. Cakir",

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

year = "2020",

month = apr,

day = "24",

doi = "10.1103/PhysRevLett.124.162002",

language = "English",

volume = "124",

journal = "Physical Review Letters",

issn = "0031-9007",

publisher = "American Physical Society",

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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 - Cakir, A.

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.

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U2 - 10.1103/PhysRevLett.124.162002

DO - 10.1103/PhysRevLett.124.162002

M3 - Article

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

Abstract

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Funding

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