Measurement of the cross section for electroweak production of a Z boson, a photon and two jets in proton-proton collisi
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Springer
Received: February 23, 2020 Accepted: May 12, 2020 Published: June 10, 2020
The CMS collaboration E-mail: [email protected] Abstract: A measurement is presented of the cross section for electroweak production of a Z boson and a photon in association with two jets (Zγjj) in proton-proton collisions. The Z boson candidates are selected through their decay into a pair of electrons or muons. The process of interest, electroweak Zγjj production, is isolated by selecting events with a large dijet mass and a large pseudorapidity gap between the two jets. The measurement is based √ on data collected at the CMS experiment at s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1 . The observed significance of the signal is 3.9 standard deviations, where a significance of 5.2 standard deviations is expected in the standard model. These √ results are combined with published results by CMS at s = 8 TeV, which leads to observed and expected respective significances of 4.7 and 5.5 standard deviations. From the 13 TeV data, a value is obtained for the signal strength of electroweak Zγjj production and bounds are given on quartic vector boson interactions in the framework of dimension-eight effective field theory operators. Keywords: Electroweak interaction, Hadron-Hadron scattering (experiments) ArXiv ePrint: 2002.09902
Open Access, Copyright CERN, for the benefit of the CMS Collaboration. 3 Article funded by SCOAP .
https://doi.org/10.1007/JHEP06(2020)076
JHEP06(2020)076
Measurement of the cross section for electroweak production of a Z boson, a photon and two jets in √ proton-proton collisions at s = 13 TeV and constraints on anomalous quartic couplings
Contents 1
2 The CMS detector
2
3 Signal and background simulation
2
4 Object reconstruction and event selection 4.1 Objects reconstruction 4.2 Event selection
4 4 6
5 Background estimation
8
6 Systematic uncertainties
8
7 Results 7.1 Measurement of the signal significance 7.2 Fiducial cross section 7.3 Limits on anomalous quartic gauge couplings
11 11 12 14
8 Summary
17
The CMS collaboration
22
1
Introduction
The standard model (SM) is well tested and continues to be a reliable model of nature, bolstered by the discovery and measurement of the properties of the Higgs boson at the CERN LHC [1–5]. However, a search for incontrovertible evidence of new physics, and a lack of understanding of how all the forces unify motivates further study of the EW sector. For example, novel processes, such as vector boson scattering (VBS), probe unexplored aspects of the nonabelian nature of gauge interactions. The VBS processes are pure electroweak interactions where vector bosons are radiated from the initial state quarks and directly interact via scattering to produce a final state of two scattered vector bosons and two jets from the quarks. Many beyond-the-SM (BSM) models alter the couplings of vector bosons, and such effects can be parametrized through effective field theories [6]. The VBS topology is sensitive to quartic
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