CMS-PAS-B2G-16-023

CMS-PAS-B2G-16-023
Search for diboson resonances in the $ 2 \ell 2 \nu $ final state
CMS Collaboration
May 2017

Abstract: A search for a heavy resonances decaying to a pair of Z bosons is presented. This search selects events containing two oppositely charged leptons (electrons or muons) consistent with the decay of a Z boson, and large missing transverse momentum, which is interpreted as the decay of a second Z boson to two neutrinos. The analysis uses data collected in 2016 with the CMS detector, corresponding to 35.9 fb$^{-1}$ of integrated luminosity of proton-proton collisions with a center-of-mass energy of 13 TeV at the LHC. The search is performed using the transverse mass spectrum of the two leptons and the missing transverse momentum system, where a new heavy resonance can be expected to produce a Jacobian Edge corresponding to its invariant mass at the TeV scale. The theoretical hypothesis of a narrow width spin-2 bulk graviton is examined. The observed upper limits are consistent with the SM backgrounds prediction. For $\tilde{k}=$ 0.5, the mass region below 800 GeV is excluded at 95% confidence level.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, JHEP 03 (2018) 003. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Feynman diagram for the production of a generic resonance X produced via gluon fusion and decaying to the ZZ final state considered in this study.
png pdf	Figure 2: The $p_{\mathrm {T}}^{\mathrm {Z}}$ distributions for electron (left) and muon (right) channels comparing data and data-driven background modeling in the SR. The lower panels show the ratio of data to the prediction for background, where the error band shows only the statistical uncertainties of the data over background ratio. Signal cross-sections times branching fraction are arbitrarily normalized to 1 pb.
png pdf	Figure 2-a: The $p_{\mathrm {T}}^{\mathrm {Z}}$ distributions for the electron channel comparing data and data-driven background modeling in the SR. The lower panel shows the ratio of data to the prediction for background, where the error band shows only the statistical uncertainties of the data over background ratio. Signal cross-sections times branching fraction are arbitrarily normalized to 1 pb.
png pdf	Figure 2-b: The $p_{\mathrm {T}}^{\mathrm {Z}}$ distributions for the muon channel comparing data and data-driven background modeling in the SR. The lower panel shows the ratio of data to the prediction for background, where the error band shows only the statistical uncertainties of the data over background ratio. Signal cross-sections times branching fraction are arbitrarily normalized to 1 pb.
png pdf	Figure 3: The $E_{\mathrm {T}}^{\mathrm {miss}}$ for electron (left) and muon (right) channels comparing data and background models. The lower panels show the ratio of data to the prediction for background. The signal cross-sections times branching fraction are arbitrarily normalized to 1 pb.
png pdf	Figure 3-a: The $E_{\mathrm {T}}^{\mathrm {miss}}$ for the electron channel comparing data and background models. The lower panel shows the ratio of data to the prediction for background. The signal cross-sections times branching fraction are arbitrarily normalized to 1 pb.
png pdf	Figure 3-b: The $E_{\mathrm {T}}^{\mathrm {miss}}$ for the muon channel comparing data and background models. The lower panel shows the ratio of data to the prediction for background. The signal cross-sections times branching fraction are arbitrarily normalized to 1 pb.
png pdf	Figure 4: The $M_{\mathrm {T}}$ distributions for electron (ee, left) and muon ($\mu \mu $, right) channels comparing data and data-driven background modeling after fitting only the background modeling to the data (Post-fit B-only). A model of the expected distribution for a spin-2 bulk graviton with $M_{\mathrm {G}}= $ 1 TeV is shown after normalization to a cross section of 1 pb. The uncertainty bands on the ratio plots show the systematic uncertainties, while the statistical uncertainty on the data is reflected by the error bars. The lower panels show the ratio of data to the prediction for background.
png pdf	Figure 4-a: The $M_{\mathrm {T}}$ distributions for the electron (ee) channel comparing data and data-driven background modeling after fitting only the background modeling to the data (Post-fit B-only). A model of the expected distribution for a spin-2 bulk graviton with $M_{\mathrm {G}}= $ 1 TeV is shown after normalization to a cross section of 1 pb. The uncertainty bands on the ratio plots show the systematic uncertainties, while the statistical uncertainty on the data is reflected by the error bars. The lower panel shows the ratio of data to the prediction for background.
png pdf	Figure 4-b: The $M_{\mathrm {T}}$ distributions for the muon ($\mu \mu $) channel comparing data and data-driven background modeling after fitting only the background modeling to the data (Post-fit B-only). A model of the expected distribution for a spin-2 bulk graviton with $M_{\mathrm {G}}= $ 1 TeV is shown after normalization to a cross section of 1 pb. The uncertainty bands on the ratio plots show the systematic uncertainties, while the statistical uncertainty on the data is reflected by the error bars. The lower panel shows the ratio of data to the prediction for background.
png pdf	Figure 5: Expected and observed limits on the production cross-section of a new spin-2 heavy resonance $\mathrm {X \to ZZ}$ assuming zero mass width based on the combined analysis of the electron and muon channels. Expected production cross sections are also shown for the benchmark bulk graviton model for two values of the curvature parameter $\tilde{k}$.
png pdf	Figure 6: Expected and observed limits on the production cross-section of a new spin-2 heavy resonance $\mathrm {X \to ZZ}$ assuming zero mass width separately for the electron (ee, left) and muon ($\mu \mu $, right) channels.
png pdf	Figure 6-a: Expected and observed limits on the production cross-section of a new spin-2 heavy resonance $\mathrm {X \to ZZ}$ assuming zero mass width separately for the electron (ee) channel.
png pdf	Figure 6-b: Expected and observed limits on the production cross-section of a new spin-2 heavy resonance $\mathrm {X \to ZZ}$ assuming zero mass width separately for the muon ($\mu \mu $) channel.

Tables
png pdf	Table 1: Summary of the uncertainties for the electron channel and the muon channel that are included in the limit setting. In the table, "-'' means does not apply and "(-)'' stands for negligibly small. "Signal'' refers to the hypothetical narrow width spin-2 bulk graviton sample with a mass of 1 TeV.
png pdf	Table 2: Event yields for different background contributions and those observed in data for the electron and muon channels.

Summary

A search for the production of new resonances has been performed in events with a Z boson and missing transverse momentum, using a data set corresponding to an integrated luminosity of 35.9 fb$^{-1}$ of pp collisions at a center-of-mass energy of 13 TeV. The observed data are in general agreement with expectations from SM processes and the results are analyzed to obtain limits for the production of a narrow width spin-2 bulk graviton. For a resonance X limits on the cross section times branching ratio for the process $\mathrm{X \to ZZ}$ are determined at the 95% confidence level for 600 $ <\mathrm{m_X}< $ 2500 GeV. For the narrow width resonances with $\tilde{k}= $ 0.5, the masses below 800 GeV are excluded at 95% CL, which is presently the highest upper limit for this hypothesis in ZZ final state. In comparison with the all hadronic channel results at CMS using 2016 full dataset [17], the results from the $2\ell 2\nu$ channel show a higher sensitivity in the low mass region (below 1.5 TeV), but a lower sensitivity in the high mass region (above 1.5 TeV) due to limited statistics.

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