https://scholars.lib.ntu.edu.tw/handle/123456789/574851
標題: | Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at sNN=5.02TeV | 作者: | Sirunyan A.M. et al. Tumasyan, A. Adam, W. Ambrogi, F. Asilar, E. Bergauer, T. Brandstetter, J. Dragicevic, M. Erö, J. Escalante Del Valle, A. Flechl, M. Frühwirth, R. Ghete, V.M. Hrubec, J. Jeitler, M. Krammer, N. Krätschmer, I. Liko, D. Madlener, T. Mikulec, I. Rad, N. Rohringer, H. Schieck, J. Schöfbeck, R. Spanring, M. Spitzbart, D. Taurok, A. Waltenberger, W. Wittmann, J. Wulz, C.-E. Zarucki, M. Chekhovsky, V. Mossolov, V. Suarez Gonzalez, J. PAO-TI CHANG KAI-FENG CHEN WEI-SHU HOU RONG-SHYANG LU Stathes Paganis |
公開日期: | 2019 | 卷: | 797 | 來源出版物: | Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | 摘要: | 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 390μb?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 ET γ>2GeV, pseudorapidity |ηγ|<2.4, diphoton invariant mass mγγ>5GeV, diphoton transverse momentum pT γγ<1GeV, 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 (Figure presented.) process, in the mass range (Figure presented.). ? 2019 The Author(s) |
URI: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070721104&doi=10.1016%2fj.physletb.2019.134826&partnerID=40&md5=fd6b7abdba68067a8c9fbe5ca6995c6f https://scholars.lib.ntu.edu.tw/handle/123456789/574851 |
ISSN: | 3702693 | DOI: | 10.1016/j.physletb.2019.134826 |
顯示於: | 物理學系 |
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