CMS-SMP-17-013

CMS-SMP-17-013 ; CERN-EP-2019-074
Search for the production of $ \mathrm{ W^{\pm} W^{\pm} W^{\mp} } $ events at $\sqrt{s} = $ 13 TeV
CMS Collaboration
10 May 2019
Phys. Rev. D 100 (2019) 012004
Abstract: A search for the production of events containing three W bosons predicted by the standard model is reported. The search is based on a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the CMS experiment at the CERN LHC and corresponding to a total integrated luminosity of 35.9 fb$^{-1}$. The search is performed in final states with three leptons (electrons or muons), or with two same-charge leptons plus two jets. The observed (expected) significance of the signal for $ \mathrm{ W^{\pm} W^{\pm} W^{\mp} } $ production is 0.60 (1.78) standard deviations, and the ratio of the measured signal yield to that expected from the standard model is 0.34$^{+0.62}_{-0.34}$. Limits are placed on three anomalous quartic gauge couplings and on the production of massive axion-like particles.
Links: e-print arXiv:1905.04246 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;

Figures & Tables	Summary	Additional Figures	References	CMS Publications

Figures
png pdf	Figure 1: Tree-level Feynman diagrams for $ \mathrm{ W^{\pm} W^{\pm} W^{\mp} } $ production
png pdf	Figure 1-a: Tree-level Feynman diagram for $ \mathrm{ W^{\pm} W^{\pm} W^{\mp} } $ production
png pdf	Figure 1-b: Tree-level Feynman diagram for $ \mathrm{ W^{\pm} W^{\pm} W^{\mp} } $ production
png pdf	Figure 1-c: Tree-level Feynman diagram for $ \mathrm{ W^{\pm} W^{\pm} W^{\mp} } $ production
png pdf	Figure 1-d: Tree-level Feynman diagram for $ \mathrm{ W^{\pm} W^{\pm} W^{\mp} } $ production
png pdf	Figure 2: Comparison of the observed numbers of events to the predicted yields in the nine signal regions. The $ \mathrm{ W^{\pm} W^{\pm} W^{\mp} } $ signal shown is stacked on top of the total background and is based on the SM theoretical cross section.
png pdf	Figure 3: (left) Expected and observed 95% CL upper limits on the product of the cross section and branching fraction $\sigma ({\mathrm{p}} {\mathrm{p}} \to \mathrm{W} {{\mathrm {a}}}) \mathcal {B}({{\mathrm {a}}}\to {\mathrm{W} \mathrm{W}})$ as a function of ALP mass. The red line corresponds to the theoretical prediction for $1/ {f_{{\mathrm {a}}}} = $ 5 TeV$ ^{-1}$. (right) Expected and observed 95% CL 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% CL upper limits on the product of the cross section and branching fraction $\sigma ({\mathrm{p}} {\mathrm{p}} \to \mathrm{W} {{\mathrm {a}}}) \mathcal {B}({{\mathrm {a}}}\to {\mathrm{W} \mathrm{W}})$ as a function of ALP mass. The red line corresponds to the theoretical prediction for $1/ {f_{{\mathrm {a}}}} = $ 5 TeV$ ^{-1}$.
png pdf	Figure 3-b: Expected and observed 95% CL 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-3$\ell $ contribution, which are estimated from simulation, are reported together with the control-to-signal region transfer factor ($TF_{\mathrm {CR}\to \mathrm {SR}}$). The last column reports the prediction of the lost-lepton and three-lepton background contributions to the signal regions, together with the statistical and systematic uncertainties.
png pdf	Table 4: Nonprompt-lepton background estimates. The data in the application regions (AR), the prompt yields (AR) from simulations, and the predicted nonprompt-lepton background are reported. The uncertainties in the prediction are split into statistical and systematic components.
png pdf	Table 5: Summary of typical systematic uncertainties in estimated background contributions. The ranges indicate variations across different signal regions.
png pdf	Table 6: Summary of systematic uncertainties for the signal process.
png pdf	Table 7: Numbers of observed events for all signal regions, including predicted background contributions and expected signal yields. The uncertainties presented include both the statistical and systematic uncertainties.
png pdf	Table 8: Limits on three anomalous quartic couplings at 95% CL.

Summary

A search for $ \mathrm{ W^{\pm} W^{\pm} W^{\mp} } $ production using proton-proton collision data at a center-of-mass energy of 13 TeV was presented. Events with either two same-sign leptons (electrons or muons) and two jets or with three leptons with total charge $\pm$1 were selected. The data were collected with the CMS experiment and correspond to an integrated luminosity of 35.9 fb$^{-1}$. The dominant sources of standard model backgrounds include nonprompt leptons, three-lepton events such as those from the process ${\mathrm{W}\mathrm{Z}} \to3\ell\nu$, as well as ${\mathrm{W^{\pm}}\mathrm{W^{\pm}}}$+jets and ${\mathrm{t\bar{t}}\mathrm{W^{\pm}}}$ production. Predictions for these backgrounds were derived or validated using data in dedicated control regions. The observed (expected) significance for $ \mathrm{ W^{\pm} W^{\pm} W^{\mp} } $ 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 0.17$^{+0.32}_{-0.17}$ pb.

New physics processes that could lead to an excess of events were considered. Limits on anomalous quartic gauge couplings are set, for example; $-1.2 < {f_{\mathrm{T},0}} / \Lambda^4 < $ 1.2 TeV$^{-4}$ at 95% confidence level. Limits are also set on the production of axion-like particles in association with a W boson: mass points between ${m_{{\mathrm{a}} }} = $ 200 and 480 GeV are excluded for the parameter value $1/{f_{{\mathrm{a}} }} = $ 5 TeV$^{-1}$.

Additional Figures
png pdf	Additional Figure 1: Predicted signal and background yields normalized to 35.9 fb$^{-1}$ for the nine signal regions. The SM production of WWW events is stacked on top of the background and is based on the SM expectation. The bottom panel shows the relative size of the WWW signal compared to all other SM processes that contribute to the signal regions, labeled here as "S/B''.
png pdf	Additional Figure 2: The top panel shows the comparison of the observed numbers of events to the predicted backgrounds in the nine signal regions. The black dots represent 35.9 fb$^{-1}$ of data collected during 2016 pp collisions. The WWW signal shown is stacked on top of the background and is based on the SM expectation. The bottom panel shows the relative size of the expected WWW signal compared to all other SM processes that contribute to the signal regions, labeled here as "S/B''. In both panels, the signal regions are ordered according to S/B.
png pdf	Additional Figure 3: Data and simulation yields for the lost lepton/3-lepton control regions for 35.9 fb$^{-1}$. The regions are defined from left to right as the control regions for $e^{\pm}e^{\pm}$, $e^{\pm}\mu ^{\pm}$, $\mu ^{\pm}\mu ^{\pm}$, 1 SFOS, and 2 SFOS. The bottom panel shows the ratio of data over simulation. The shaded area represents the statistical uncertainty associated with the background prediction.
png pdf	Additional Figure 4: The distribution of the $S_\mathrm {T}$ variable, defined as the scalar sum of the transverse momenta of all jets, leptons, and ${{p_{\mathrm {T}}} ^\text {miss}}$, in the same-sign dilepton signal region presented on a logarithmic scale. The backgrounds are represented as filled histograms and the the data are represented with black dots. Two anomalous coupling scenarios, corresponding to two different values of ${{\mathrm {f}}_{{\mathrm {T}},0}}/{\Lambda ^{4}}$, are overlaid. The last bin contains the overflow. The shaded area represents the statistical uncertainty associated with the background prediction.
png pdf	Additional Figure 5: The distribution of the $S_\mathrm {T}$ variable, defined as the scalar sum of the transverse momenta of all jets, leptons, and ${{p_{\mathrm {T}}} ^\text {miss}}$, in the same-sign dilepton signal region presented on a linear scale. The backgrounds are represented as filled histograms and the the data are represented with black dots. Two anomalous coupling scenarios, corresponding to two different values of ${{\mathrm {f}}_{{\mathrm {T}},0}}/{\Lambda ^{4}}$, are overlaid. The last bin contains the overflow. The shaded area represents the statistical uncertainty associated with the background prediction.
png pdf	Additional Figure 6: The distribution of the $S_\mathrm {T}$ variable, defined as the scalar sum of the transverse momenta of all jets, leptons, and ${{p_{\mathrm {T}}} ^\text {miss}}$, in the trilepton signal region presented on a logarithmic scale. The backgrounds are represented as filled histograms and the the data are represented with black dots. Two anomalous coupling scenarios, corresponding to two different values of ${{\mathrm {f}}_{{{\mathrm T},0}}}/{\Lambda ^{4}}$, are overlaid. The last bin contains the overflow. The shaded area represents the statistical uncertainty associated with the background prediction.
png pdf	Additional Figure 7: The distribution of the $S_\mathrm {T}$ variable, defined as the scalar sum of the transverse momenta of all jets, leptons, and ${{p_{\mathrm {T}}} ^\text {miss}}$, in the trilepton signal region presented on a linear scale. The backgrounds are represented as filled histograms and the the data are represented with black dots. Two anomalous coupling scenarios, corresponding to two different values of ${{\mathrm {f}}_{{{\mathrm T},0}}}/{\Lambda ^{4}}$, are overlaid. The last bin contains the overflow. The shaded area represents the statistical uncertainty associated with the background prediction.

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