CMS-PAS-SMP-17-013

CMS-PAS-SMP-17-013
Search for the production of $\mathrm{W}^{\pm}\mathrm{W}^{\pm}\mathrm{W}^{\mp}$ events with two equally charged or three leptons at $\sqrt{s} =$ 13 TeV
CMS Collaboration
March 2019

Abstract: A search for the production of events containing three W bosons is reported. The search is based on a data sample of proton-proton collisions at $\sqrt{s}=$ 13 TeV recorded by the CMS experiment and corresponding to a total integrated luminosity of 35.9 fb $^{-1}$ . The search is performed in final states with two leptons (electrons or muons) of the same charge or with three leptons. The observed (expected) significance for WWW production is 0.60 (1.78) standard deviations, and the ratio of measured signal yields to that expected from the standard model is 0.34 $^{+0.62}_{-0.34}$ . Limits are also placed on anomalous quartic gauge couplings and on the production of massive axion-like particles.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, PRD 100 (2019) 012004. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Tree-level Feynman diagrams for WWW production
png pdf	Figure 1-a: Tree-level Feynman diagram for WWW production
png pdf	Figure 1-b: Tree-level Feynman diagram for WWW production
png pdf	Figure 1-c: Tree-level Feynman diagram for WWW production
png pdf	Figure 1-d: Tree-level Feynman diagrams for WWW production
png pdf	Figure 2: Comparison of the observed numbers of events to the predicted backgrounds in the nine signal regions. The WWW signal shown is stacked on top of the background and is based on the SM theoretical cross section.
png pdf	Figure 3: (a) Expected and observed 95% C.L. upper limits on the cross section times the branching ratio $\sigma ({\mathrm {p}} {\mathrm {p}}\rightarrow {\mathrm {W}} \mathrm{a}) B(\mathrm{a}\rightarrow {{\mathrm {W}} {\mathrm {W}}})$ as a function of ALP mass. The red line corresponds to the theory prediction for $1/f_{\mathrm{a}}=$ 5 TeV $^{-1}$ . (b) Expected and observed 95% C.L. upper limits on the photophobic ALP model parameter $1/f_{\mathrm{a}}$ as a function of ALP mass.
png pdf	Figure 3-a: Expected and observed 95% C.L. upper limits on the cross section times the branching ratio $\sigma ({\mathrm {p}} {\mathrm {p}}\rightarrow {\mathrm {W}} \mathrm{a}) B(\mathrm{a}\rightarrow {{\mathrm {W}} {\mathrm {W}}})$ as a function of ALP mass. The red line corresponds to the theory prediction for $1/f_{\mathrm{a}}=$ 5 TeV $^{-1}$ .
png pdf	Figure 3-b: Expected and observed 95% C.L. upper limits on the photophobic ALP model parameter $1/f_{\mathrm{a}}$ as a function of ALP mass.

Tables
png pdf	Table 1: Event selection criteria for the SS category, which contains events with two same-sign leptons and at least two hadronic jets
png pdf	Table 2: Event selection criteria for the $3\ell$ category, which contains events with exactly three leptons
png pdf	Table 3: Lost-lepton and three-lepton background contributions. The number of events in the data control regions (CRs) and the non-three-lepton contribution as estimated from simulation are reported together with the control-to-signal region transfer factor ( $TF_{\text {CR}\to \text {SR}}$ ). The last column reports the prediction of the lost-lepton and three-lepton background contributions to our signal regions, together with the statistical and systematic uncertainties
png pdf	Table 4: Non-prompt lepton background estimates. The data in the application regions (ARs), the prompt contribution as predicted from simulation are reported next to the final prediction of the non-prompt lepton background. The uncertainties on the prediction are split into statistical and systematic uncertainties
png pdf	Table 5: Summary of typical systematic uncertainties of estimated background contributions. The ranges indicate variations across different signal regions
png pdf	Table 6: Summary of systematic uncertainties for the signal
png pdf	Table 7: Numbers of observed events for all signal regions, including predicted background contributions and expected signal yields
png pdf	Table 8: Limits on anomalous quartic couplings at 95% CL

Summary

A search for WWW production using pp collision data at

$\sqrt{s} =$ 13 TeV in events containing either two equally charged or three leptons (electrons or muons) has been presented. The data were collected with the CMS experiment and correspond to an integrated luminosity of 35.9 fb

$^{-1}$ . The dominant sources of SM backgrounds include non-prompt leptons, three-lepton events such as the

$\mathrm{W}\mathrm{Z}\to3\ell\nu$ process, as well as

${\mathrm{W^{\pm}}\mathrm{W^{\pm}}}$ +jets and

${\mathrm{t\bar{t}}\mathrm{W^{\pm}}}$ production. Predictions for these backgrounds are derived or validated using data in dedicated control regions. The observed (expected) significance for WWW production is 0.60 (1.78) standard deviations and the ratio of measured signal yield to that expected from the standard model is 0.34

$^{+0.62}_{-0.34}$ , which corresponds to a measured cross section of 173

$^{+326}_{-173}$ fb.

New physics processes that could lead to an excess of events were considered, and limits on anomalous quartic gauge couplings were set, for example:

$-$ 1.2 TeV

$^{-4}$

$< f_{\mathrm{T},0} / \Lambda^4 <$ 1.2 TeV

$^{-4}$ at 95% CL. Limits were also set on the production of axion-like particles in association with a W boson: mass points between

$m_{a} =$ 200 GeV to

$m_{a} =$ 480 GeV are excluded for the free parameter value of

$1/f_{\mathrm{a}} =$ 5 TeV

$^{-1}$ .

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