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| CMS-PAS-EXO-17-005 | ||
| Search for high-mass Z$\gamma$ resonances in proton-proton collisions at $\sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| May 2017 | ||
| Abstract: A search for high-mass resonances decaying to a Z boson and a photon is presented. The analysis is based on a data set of proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$ collected with the CMS detector at the LHC in 2016. In the leptonic channel the Z boson candidates are reconstructed using an electron or a muon pair. In the hadronic channel they are identified using a large-radius jet containing either light-quark or b quark decay products of the Z boson, identified using jet substructure and advanced b tagging techniques. The results in the leptonic and hadronic channels are combined and interpreted in terms of upper limits on the production cross section of narrow and broad spin-0 resonances with masses between 0.3 and 4.0 TeV. These limits are most stringent to date for a wide range of resonance masses. | ||
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Links:
CDS record (PDF) ;
inSPIRE record ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, JHEP 09 (2018) 148. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Observed $ {{M}_{\ell \ell \gamma }} $ invariant mass spectra in the data, for the $ {\mathrm{ e } ^+\mathrm{ e } ^-\gamma } $ (left) and the $ {\mu ^+\mu ^-\gamma } $ (right) channels. The fitted function is represented by a line, with the 68% uncertainty band as gray shading. The lower panels show the difference between the data and the fit, divided by the uncertainty $\sigma _\text {stat}$, which includes the statistical uncertainty in both the data and the fit. For bins with a low number of data entries, the error bars correspond to the Garwood confidence intervals. |
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Figure 1-a:
Observed $ {{M}_{\ell \ell \gamma }} $ invariant mass spectra in the data, for the $ {\mathrm{ e } ^+\mathrm{ e } ^-\gamma } $ channel. The fitted function is represented by a line, with the 68% uncertainty band as gray shading. The lower panel shows the difference between the data and the fit, divided by the uncertainty $\sigma _\text {stat}$, which includes the statistical uncertainty in both the data and the fit. For bins with a low number of data entries, the error bars correspond to the Garwood confidence intervals. |
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Figure 1-b:
Observed $ {{M}_{\ell \ell \gamma }} $ invariant mass spectra in the data, for the $ {\mu ^+\mu ^-\gamma } $ channel. The fitted function is represented by a line, with the 68% uncertainty band as gray shading. The lower panel shows the difference between the data and the fit, divided by the uncertainty $\sigma _\text {stat}$, which includes the statistical uncertainty in both the data and the fit. For bins with a low number of data entries, the error bars correspond to the Garwood confidence intervals. |
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Figure 2:
Fits in the signal region in the b-tagged, tau21 and anti-tau21 categories. |
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Figure 2-a:
Fits in the signal region in the b-tagged category. |
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Figure 2-b:
Fits in the signal region in the tau21 category. |
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Figure 2-c:
Fits in the signal region in the anti-tau21 category. |
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Figure 3:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma \rightarrow \ell ^{+}\ell ^{-}\gamma )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, for (a) the ${\mathrm{ e } ^+\mathrm{ e } ^-\gamma }$ channel with the narrow-width scenario, (b) the ${\mu ^+\mu ^-\gamma }$ channel with the narrow-width scenario, (c) the ${\mathrm{ e } ^+\mathrm{ e } ^-\gamma }$ channel with the wide-width scenario, and (d) the ${\mu ^+\mu ^-\gamma }$ channel with the wide-width scenario. |
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Figure 3-a:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma \rightarrow \ell ^{+}\ell ^{-}\gamma )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, for the ${\mathrm{ e } ^+\mathrm{ e } ^-\gamma }$ channel with the narrow-width scenario. |
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Figure 3-b:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma \rightarrow \ell ^{+}\ell ^{-}\gamma )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, for the ${\mu ^+\mu ^-\gamma }$ channel with the narrow-width scenario. |
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Figure 3-c:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma \rightarrow \ell ^{+}\ell ^{-}\gamma )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, for the ${\mathrm{ e } ^+\mathrm{ e } ^-\gamma }$ channel with the wide-width scenario. |
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Figure 3-d:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma \rightarrow \ell ^{+}\ell ^{-}\gamma )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, for the ${\mu ^+\mu ^-\gamma }$ channel with the wide-width scenario. |
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Figure 4:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$ as a function of signal mass, together with the 68% (green) and 95% (yellow) ranges of expectation in the background-only hypothesis, for the combination of the ${\mathrm{ e } ^+\mathrm{ e } ^-\gamma }$ and ${\mu ^+\mu ^-\gamma }$ channels with (a) the narrow-width scenario and (b) the wide-width scenario. |
png pdf |
Figure 4-a:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$ as a function of signal mass, together with the 68% (green) and 95% (yellow) ranges of expectation in the background-only hypothesis, for the combination of the ${\mathrm{ e } ^+\mathrm{ e } ^-\gamma }$ and ${\mu ^+\mu ^-\gamma }$ channels with the narrow-width scenario. |
png pdf |
Figure 4-b:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$ as a function of signal mass, together with the 68% (green) and 95% (yellow) ranges of expectation in the background-only hypothesis, for the combination of the ${\mathrm{ e } ^+\mathrm{ e } ^-\gamma }$ and ${\mu ^+\mu ^-\gamma }$ channels with the wide-width scenario. |
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Figure 5:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, for (a) b-tagged category with the narrow-width scenario, (b) tau21 category with the narrow-width scenario, (c) anti-tau21 category with the narrow-width scenario, (d) b-tagged category with the wide-width scenario, (e) tau21 category with the wide-width scenario, and (f) anti-tau21 category with the wide-width scenario |
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Figure 5-a:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, for b-tagged category with the narrow-width scenario. |
png pdf |
Figure 5-b:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, for tau21 category with the narrow-width scenario. |
png pdf |
Figure 5-c:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, for anti-tau21 category with the narrow-width scenario. |
png pdf |
Figure 5-d:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, for b-tagged category with the wide-width scenario. |
png pdf |
Figure 5-e:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, for tau21 category with the wide-width scenario. |
png pdf |
Figure 5-f:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$, as a function of signal mass, together with the 68% and 95% ranges of expectation in the background-only hypothesis, for anti-tau21 category with the wide-width scenario. |
png pdf |
Figure 6:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$ as a function of signal mass, together with the 68% (green) and 95% (yellow) ranges of expectation in the background-only hypothesis, for the combination of the b-tagged, tau21, and anti-tau21 categories with (a) the narrow-width scenario and (b) the wide-width scenario. |
png pdf |
Figure 6-a:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$ as a function of signal mass, together with the 68% (green) and 95% (yellow) ranges of expectation in the background-only hypothesis, for the combination of the b-tagged, tau21, and anti-tau21 categories with the narrow-width scenario. |
png pdf |
Figure 6-b:
Observed (solid) and expected (dashed) 95% C.L. upper limits on $\sigma (X\rightarrow Z\gamma )$ as a function of signal mass, together with the 68% (green) and 95% (yellow) ranges of expectation in the background-only hypothesis, for the combination of the b-tagged, tau21, and anti-tau21 categories with the wide-width scenario. |
png pdf |
Figure 7:
Left: Observed and expected limits on the product of the cross section at $ \sqrt{s} = $ 13 TeV and branching fraction ${\cal B}(\mathrm {X} \to \mathrm{ Z } \gamma )$ for the production of a narrow spin-0 resonance, obtained from the combination of the 13 TeV analyses in hadronic and leptonic decay channels of the Z boson, assuming a gluon fusion production mechanism. Right: Observed and expected limits for broad spin-0 resonance. |
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Figure 7-a:
Observed and expected limits on the product of the cross section at $ \sqrt{s} = $ 13 TeV and branching fraction ${\cal B}(\mathrm {X} \to \mathrm{ Z } \gamma )$ for the production of a narrow spin-0 resonance, obtained from the combination of the 13 TeV analyses in hadronic and leptonic decay channels of the Z boson, assuming a gluon fusion production mechanism. |
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Figure 7-b:
Observed and expected limits for broad spin-0 resonance. |
| Tables | |
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Table 1:
Summary of the sources of uncertainties and their effects on the signal yield. |
| Summary |
| A search for high-mass resonances decaying to a Z boson and a photon has been presented, where the Z boson decays leptonically (an electron or a muon pair) or hadronically. In the hadronic channel, the Z boson candidates are reconstructed by a light-quark and b-quark jet identified using jet substructure and advanced b-tagging techniques. This search is based on the full 2016 dataset, corresponding to an integrated luminosity of 35.9 fb$^{-1}$ of proton-proton collision data collected by the CMS detector at the center-of-mass energies of 13 TeV. Spin-0 resonances with masses in a range between 0.3 and 4.0 TeV are considered and these results in the leptonic and hadronic channels are combined. The results are presented in terms of upper limits on the production cross section of such resonances. |
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