Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at √sNN = 5.02 TeV

Paula Anna-Maria Eerola; Henning Kirschenmann; J. Pekkanen; Mikko Voutilainen; Joona Havukainen; J.K. Heikkilä; T. Järvinen; V. Karimäki; R. Kinnunen; Tapio Lampén; K. Lassila-Perini; Santeri Henrikki Laurila; Sami Lehti; Tomas Lindén; P. Luukka; T. Mäenpää; Hannu Siikonen; Eija Maarit Tuominen; Jorma Tuominiemi; T. Tuuva; CMS Collaboration

doi:10.1016/j.physletb.2019.134826

Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at √s_NN= 5.02 TeV

Paula Anna-Maria Eerola, Henning Kirschenmann, J. Pekkanen, Mikko Voutilainen, Joona Havukainen, J.K. Heikkilä, T. Järvinen, V. Karimäki, R. Kinnunen, Tapio Lampén, K. Lassila-Perini, Santeri Henrikki Laurila, Sami Lehti, Tomas Lindén, P. Luukka, T. Mäenpää, Hannu Siikonen, Eija Maarit Tuominen, Jorma Tuominiemi, T. TuuvaCMS Collaboration

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Abstract

Evidence for the light-by-light scattering process, γγ→γγ, in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02TeV is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 390 µb⁻¹ recorded by the CMS experiment at the LHC. Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy E_T^γ> 2 GeV, pseudorapidity |η^γ| < 2.4, diphoton invariant mass m^γγ> 5 GeV, diphoton transverse momentum p_T^γγ< 1 GeV, and diphoton acoplanarity below 0.01. After all selection criteria are applied, 14 events are observed, compared to expectations of 9.0 ± 0.9 (theo) events for the signal and 4.0 ± 1.2 (stat) for the background processes. The excess observed in data relative to the background-only expectation corresponds to a significance of 3.7 standard deviations, and has properties consistent with those expected for the light-by-light scattering signal. The measured fiducial light-by-light scattering cross section, σ_fid(γγ→γγ) = 120 ± 46 (stat) ± 28 (syst)± 12 (theo) nb, is consistent with the standard model prediction. The m^γγ distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the γγ→^aa→γγ process, in the mass range m_a = 5-90 GeV.

Original language	English
Article number	134826
Journal	Physics Letters B
Volume	797
DOIs	https://doi.org/10.1016/j.physletb.2019.134826
Publication status	Published - 10 Oct 2019
MoE publication type	A1 Journal article-refereed

Funding

Individuals have received support from the Marie-Curie programme and the European Research Council and Horizon 2020 Grant, contract No. 675440 (European Union); the Leventis Foundation; the Alfred P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the F.R.S. - FNRS and FWO (Belgium) under the “Excellence of Science - EOS” - be.h project n. 30820817 ; the Ministry of Education, Youth and Sports (MEYS) of the Czech Republic; the Lendület (“Momentum”) Programme and the János Bolyai Research Scholarship of the Hungarian Academy of Sciences, the New National Excellence Program ÚNKP, the NKFIA research grants 123842, 123959, 124845, 124850 and 125105 (Hungary); the Council of Science and Industrial Research, India; the HOMING PLUS programme of the Foundation for Polish Science, cofinanced from European Union, Regional Development Fund, the Mobility Plus programme of the Ministry of Science and Higher Education, the National Science Center (Poland), contracts Harmonia 2014/14/M/ST2/00428, Opus 2014/13/B/ST2/02543, 2014/15/B/ST2/03998, and 2015/19/B/ST2/02861, Sonata-bis 2012/07/E/ST2/01406; the National Priorities Research Program by Qatar National Research Fund; the Programa Estatal de Fomento de la Investigación Científica y Técnica de Excelencia María de Maeztu, grant MDM-2015-0509 and the Programa Severo Ochoa del Principado de Asturias; the Thalis and Aristeia programmes cofinanced by EU-ESF and the Greek NSRF; the Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chulalongkorn University and the Chulalongkorn Academic into Its 2nd Century Project Advancement Project (Thailand); the Welch Foundation, contract C-1845; and the Weston Havens Foundation (USA).

Keywords

CMS
Light-by-light
PbPb
Photoproduction
UPC

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Cite this

Eerola, P. A.-M., Kirschenmann, H., Pekkanen, J., Voutilainen, M., Havukainen, J., Heikkilä, J. K., Järvinen, T., Karimäki, V., Kinnunen, R., Lampén, T., Lassila-Perini, K., Laurila, S. H., Lehti, S., Lindén, T., Luukka, P., Mäenpää, T., Siikonen, H., Tuominen, E. M., Tuominiemi, J., ... CMS Collaboration (2019). Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at √s_NN= 5.02 TeV. Physics Letters B, 797, Article 134826. https://doi.org/10.1016/j.physletb.2019.134826

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title = "Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at √sNN = 5.02 TeV",

abstract = "Evidence for the light-by-light scattering process, γγ→γγ, in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02TeV is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 390 µb−1 recorded by the CMS experiment at the LHC. Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy ETγ > 2 GeV, pseudorapidity |ηγ| < 2.4, diphoton invariant mass mγγ > 5 GeV, diphoton transverse momentum pTγγ < 1 GeV, and diphoton acoplanarity below 0.01. After all selection criteria are applied, 14 events are observed, compared to expectations of 9.0 ± 0.9 (theo) events for the signal and 4.0 ± 1.2 (stat) for the background processes. The excess observed in data relative to the background-only expectation corresponds to a significance of 3.7 standard deviations, and has properties consistent with those expected for the light-by-light scattering signal. The measured fiducial light-by-light scattering cross section, σfid(γγ→γγ) = 120 ± 46 (stat) ± 28 (syst)± 12 (theo) nb, is consistent with the standard model prediction. The mγγ distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the γγ→aa→γγ process, in the mass range ma = 5-90 GeV.",

keywords = "CMS, Light-by-light, PbPb, Photoproduction, UPC",

author = "Eerola, {Paula Anna-Maria} and Henning Kirschenmann and J. Pekkanen and Mikko Voutilainen and Joona Havukainen and J.K. Heikkil{\"a} and T. J{\"a}rvinen and V. Karim{\"a}ki and R. Kinnunen and Tapio Lamp{\'e}n and K. Lassila-Perini and Laurila, {Santeri Henrikki} and Sami Lehti and Tomas Lind{\'e}n and P. Luukka and T. M{\"a}enp{\"a}{\"a} and Hannu Siikonen and Tuominen, {Eija Maarit} and Jorma Tuominiemi and T. Tuuva and {CMS Collaboration}",

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doi = "10.1016/j.physletb.2019.134826",

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Eerola, PA-M, Kirschenmann, H, Pekkanen, J, Voutilainen, M, Havukainen, J, Heikkilä, JK, Järvinen, T, Karimäki, V, Kinnunen, R, Lampén, T, Lassila-Perini, K, Laurila, SH, Lehti, S, Lindén, T, Luukka, P, Mäenpää, T, Siikonen, H, Tuominen, EM, Tuominiemi, J, Tuuva, T & CMS Collaboration 2019, 'Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at √s_NN= 5.02 TeV', Physics Letters B, vol. 797, 134826. https://doi.org/10.1016/j.physletb.2019.134826

TY - JOUR

T1 - Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at √sNN = 5.02 TeV

AU - Eerola, Paula Anna-Maria

AU - Kirschenmann, Henning

AU - Pekkanen, J.

AU - Voutilainen, Mikko

AU - Havukainen, Joona

AU - Heikkilä, J.K.

AU - Järvinen, T.

AU - Karimäki, V.

AU - Kinnunen, R.

AU - Lampén, Tapio

AU - Lassila-Perini, K.

AU - Laurila, Santeri Henrikki

AU - Lehti, Sami

AU - Lindén, Tomas

AU - Luukka, P.

AU - Mäenpää, T.

AU - Siikonen, Hannu

AU - Tuominen, Eija Maarit

AU - Tuominiemi, Jorma

AU - Tuuva, T.

AU - CMS Collaboration

PY - 2019/10/10

Y1 - 2019/10/10

N2 - Evidence for the light-by-light scattering process, γγ→γγ, in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02TeV is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 390 µb−1 recorded by the CMS experiment at the LHC. Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy ETγ > 2 GeV, pseudorapidity |ηγ| < 2.4, diphoton invariant mass mγγ > 5 GeV, diphoton transverse momentum pTγγ < 1 GeV, and diphoton acoplanarity below 0.01. After all selection criteria are applied, 14 events are observed, compared to expectations of 9.0 ± 0.9 (theo) events for the signal and 4.0 ± 1.2 (stat) for the background processes. The excess observed in data relative to the background-only expectation corresponds to a significance of 3.7 standard deviations, and has properties consistent with those expected for the light-by-light scattering signal. The measured fiducial light-by-light scattering cross section, σfid(γγ→γγ) = 120 ± 46 (stat) ± 28 (syst)± 12 (theo) nb, is consistent with the standard model prediction. The mγγ distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the γγ→aa→γγ process, in the mass range ma = 5-90 GeV.

AB - Evidence for the light-by-light scattering process, γγ→γγ, in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02TeV is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 390 µb−1 recorded by the CMS experiment at the LHC. Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy ETγ > 2 GeV, pseudorapidity |ηγ| < 2.4, diphoton invariant mass mγγ > 5 GeV, diphoton transverse momentum pTγγ < 1 GeV, and diphoton acoplanarity below 0.01. After all selection criteria are applied, 14 events are observed, compared to expectations of 9.0 ± 0.9 (theo) events for the signal and 4.0 ± 1.2 (stat) for the background processes. The excess observed in data relative to the background-only expectation corresponds to a significance of 3.7 standard deviations, and has properties consistent with those expected for the light-by-light scattering signal. The measured fiducial light-by-light scattering cross section, σfid(γγ→γγ) = 120 ± 46 (stat) ± 28 (syst)± 12 (theo) nb, is consistent with the standard model prediction. The mγγ distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the γγ→aa→γγ process, in the mass range ma = 5-90 GeV.

KW - CMS

KW - Light-by-light

KW - PbPb

KW - Photoproduction

KW - UPC

UR - https://researchportal.helsinki.fi/en/publications/d55c2b27-a9d8-4b53-871b-bf5e4418dc92

U2 - 10.1016/j.physletb.2019.134826

DO - 10.1016/j.physletb.2019.134826

M3 - Article

SN - 0370-2693

VL - 797

JO - Physics Letters B

JF - Physics Letters B

M1 - 134826

ER -