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| CMS-EXO-16-027 ; CERN-EP-2016-216 | ||
| Search for high-mass diphoton resonances in proton-proton collisions at 13 TeV and combination with 8 TeV search | ||
| CMS Collaboration | ||
| 8 September 2016 | ||
| Phys. Lett. B 767 (2017) 147 | ||
| Abstract: The results of a search are presented for the resonant production of high-mass photon pairs, specifically spin-0 and spin-2 resonances with an invariant mass between 0.5 and 4.5 TeV, and with a width, relative to the mass, between $ 1.4 \times 10^{-4} $ and $ 5.6 \times 10^{-2} $. The data sample corresponds to an integrated luminosity of 12.9 fb$^{-1}$ of proton-proton collisions collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV. No significant excess is observed relative to the standard model expectation. The results of the search are combined statistically with those previously obtained in 2012 and 2015 at $\sqrt{s}=$ 8 and 13 TeV, respectively, corresponding to integrated luminosities of 19.7 and 3.3 fb$^{-1}$, to derive exclusion limits on scalar resonances produced through gluon-gluon fusion, and on Randall-Sundrum gravitons. The lower mass limits for Randall-Sundrum gravitons range from 1.95 to 4.45 TeV for coupling parameters between 0.01 and 0.2. These are the most stringent limits on Randall-Sundrum graviton production to date. | ||
| Links: e-print arXiv:1609.02507 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
The observed invariant mass spectra ${m_{\gamma \gamma }}$ for selected events in the (left) EBEB and (right) EBEE categories. There are no selected events with $ {m_{\gamma \gamma }} >$ 2000 GeV. The solid lines and the shaded bands show the results of likelihood fits to the data together with the associated 1 and 2 standard deviation uncertainty bands. The ratio of the difference between the data and the fit to the statistical uncertainty in the data is given in the lower plots. |
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Figure 1-a:
The observed invariant mass spectra ${m_{\gamma \gamma }}$ for selected events in the EBEB category. There are no selected events with $ {m_{\gamma \gamma }} >$ 2000 GeV. The solid lines and the shaded bands show the results of likelihood fits to the data together with the associated 1 and 2 standard deviation uncertainty bands. The ratio of the difference between the data and the fit to the statistical uncertainty in the data is given in the lower plots. |
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Figure 1-b:
The observed invariant mass spectra ${m_{\gamma \gamma }}$ for selected events in the EBEE category. There are no selected events with $ {m_{\gamma \gamma }} >$ 2000 GeV. The solid lines and the shaded bands show the results of likelihood fits to the data together with the associated 1 and 2 standard deviation uncertainty bands. The ratio of the difference between the data and the fit to the statistical uncertainty in the data is given in the lower plots. |
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Figure 2:
The 95% CL upper limits on the production of diphoton resonances as a function of the resonance mass ${m_{\mathrm{X} }} $, from the analysis of data collected in 2016. Exclusion limits for the scalar and RS graviton signals are given by the grey (darker) and green (lighter) curves, respectively. The observed limits are shown by the solid lines, while the median expected limits are given by the dashed lines together with their associated 1 standard deviation uncertainty bands. The leading-order production cross section for diphoton resonances in the RS graviton model is shown for three values of the dimensionless coupling parameter $\tilde{k}$ together with the exclusion upper limits calculated for the corresponding three values of the width relative to the mass, ${\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} $. Shown are the results for (upper) a narrow width, (middle) an intermediate-width, and (lower) a broad resonance. |
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Figure 3:
Observed background-only $p$-values for resonances with (upper left ) $ {\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} = 1.4\times 10^{-4}$, (upper right) $1.4\times 10^{-2}$, and (bottom) $5.6\times 10^{-2}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the analysis of data collected in 2016. The solid black and dashed blue lines correspond to spin-0 and spin-2 resonances, respectively. |
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Figure 3-a:
Observed background-only $p$-values for resonances with $ {\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} = 1.4\times 10^{-4}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the analysis of data collected in 2016. The solid black and dashed blue lines correspond to spin-0 and spin-2 resonances, respectively. |
png pdf |
Figure 3-b:
Observed background-only $p$-values for resonances with $1.4\times 10^{-2}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the analysis of data collected in 2016. The solid black and dashed blue lines correspond to spin-0 and spin-2 resonances, respectively. |
png pdf |
Figure 3-c:
Observed background-only $p$-values for resonances with $5.6\times 10^{-2}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the analysis of data collected in 2016. The solid black and dashed blue lines correspond to spin-0 and spin-2 resonances, respectively. |
png pdf |
Figure 4:
The 95% CL upper limits on the production of diphoton resonances as a function of the resonance mass ${m_{\mathrm{X} }} $, from the combined analysis of data collected in 2015 and in 2016. Exclusion limits for the scalar and RS graviton signals are given by the grey (darker) and green (lighter) curves, respectively. The observed limits are shown by the solid lines, while the median expected limits are given by the dashed lines together with their associated 1 standard deviation uncertainty bands. The leading-order production cross section for diphoton resonances in the RS graviton model is shown for three values of the dimensionless coupling parameter $\tilde{k}$ together with the exclusion upper limits calculated for the corresponding three values of the width relative to the mass, ${\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} $. Shown are the results for (upper) a narrow width, (middle) an intermediate-width, and (lower) a broad resonance. |
png pdf |
Figure 5:
Observed background-only $p$-values for resonances with (upper) $ {\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} = 1.4\times 10^{-4}$ and (lower) $5.6\times 10^{-2}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the combined analysis of data recorded in 2015 and 2016. The results obtained for the two individual data sets are also shown. The curves corresponding to the scalar and RS graviton hypotheses are shown in left and right columns, respectively. The insets show an expanded region around $ {m_{\mathrm{X} }} =$ 750 GeV. |
png pdf |
Figure 5-a:
Observed background-only $p$-values for resonances with $ {\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} = 1.4\times 10^{-4}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the combined analysis of data recorded in 2015 and 2016. The results obtained for the two individual data sets are also shown. The curves corresponding to the scalar hypothesis is shown. The inset shows an expanded region around $ {m_{\mathrm{X} }} =$ 750 GeV. |
png pdf |
Figure 5-b:
Observed background-only $p$-values for resonances with $ {\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} = 1.4\times 10^{-4}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the combined analysis of data recorded in 2015 and 2016. The results obtained for the two individual data sets are also shown. The curves corresponding to the RS graviton hypothesis are shown. The inset shows an expanded region around $ {m_{\mathrm{X} }} =$ 750 GeV. |
png pdf |
Figure 5-c:
Observed background-only $p$-values for resonances with $ {\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} = 5.6\times 10^{-2}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the combined analysis of data recorded in 2015 and 2016. The results obtained for the two individual data sets are also shown. The curves corresponding to the scalar hypothesis are shown. The inset shows an expanded region around $ {m_{\mathrm{X} }} =$ 750 GeV. |
png pdf |
Figure 5-d:
Observed background-only $p$-values for resonances with $ {\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} = 5.6\times 10^{-2}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the combined analysis of data recorded in 2015 and 2016. The results obtained for the two individual data sets are also shown. The curves corresponding to the RS graviton hypothesis are shown. The inset shows an expanded region around $ {m_{\mathrm{X} }} =$ 750 GeV. |
png pdf |
Figure 6:
The 95% CL upper limits on the production of diphoton resonances as a function of the resonance mass ${m_{\mathrm{X} }} $, from the combined analysis of the 8 and 13 TeV data. The 8 TeV results are scaled by the ratio of the 8 to 13 TeV cross sections. Exclusion limits for the scalar and RS graviton signals are given by the grey (darker) and green (lighter) curves, respectively. The observed limits are shown by the solid lines, while the median expected limits are given by the dashed lines together with their associated 1 standard deviation uncertainty bands. The leading-order production cross section for diphoton resonances in the RS graviton model is shown for three values of the dimensionless coupling parameter $\tilde{k}$ together with the exclusion upper limits calculated for the corresponding three values of the width relative to the mass, ${\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} $. Shown are the results for (upper) a narrow width, (middle) an intermediate-width, and (lower) a broad resonance. |
png pdf |
Figure 7:
Observed background-only $p$-values for resonances with (upper) $ {\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} = 1.4\times 10^{-4}$ and (lower) $5.6\times 10^{-2}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the combined analysis of the 8 and 13 TeV data. The results obtained for the two individual center-of-mass energies are also shown. The curves corresponding to the scalar and RS graviton hypotheses are shown in left and right columns, respectively. The insets show an expanded region around $ {m_{\mathrm{X} }} =$ 750 GeV. |
png pdf |
Figure 7-a:
Observed background-only $p$-values for resonances with $ {\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} = 1.4\times 10^{-4}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the combined analysis of the 8 and 13 TeV data. The results obtained for the two individual center-of-mass energies are also shown. The curves corresponding to the scalar hypothesis are shown. The inset shows an expanded region around $ {m_{\mathrm{X} }} =$ 750 GeV. |
png pdf |
Figure 7-b:
Observed background-only $p$-values for resonances with $ {\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} = 1.4\times 10^{-4}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the combined analysis of the 8 and 13 TeV data. The results obtained for the two individual center-of-mass energies are also shown. The curves corresponding to the RS graviton hypothesis are shown. The inset shows an expanded region around $ {m_{\mathrm{X} }} =$ 750 GeV. |
png pdf |
Figure 7-c:
Observed background-only $p$-values for resonances with $ {\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} = 5.6\times 10^{-2}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the combined analysis of the 8 and 13 TeV data. The results obtained for the two individual center-of-mass energies are also shown. The curves corresponding to the scalar hypothesis are shown. The inset shows an expanded region around $ {m_{\mathrm{X} }} =$ 750 GeV. |
png pdf |
Figure 7-d:
Observed background-only $p$-values for resonances with $ {\Gamma _{\mathrm{X} } / m_{\mathrm{X} }} = 5.6\times 10^{-2}$ as a function of the resonance mass ${m_{\mathrm{X} }} $, from the combined analysis of the 8 and 13 TeV data. The results obtained for the two individual center-of-mass energies are also shown. The curves corresponding to the RS graviton hypothesis are shown. The inset shows an expanded region around $ {m_{\mathrm{X} }} =$ 750 GeV. |
| Summary |
| A search for the resonant production of high-mass photon pairs has been presented. The analysis is based on a sample of proton-proton collisions collected by the CMS experiment in 2016 at $\sqrt{s} =$ 13 TeV, corresponding to an integrated luminosity of 12.9 fb$^{-1}$. Events containing two photon candidates with transverse momenta above 75 GeV are selected. The diphoton mass spectrum above 500 GeV is examined for evidence of the production of high-mass spin-0 and spin-2 resonances. Limits on the production of scalar resonances and Randall-Sundrum gravitons in the range 0.5 $ < m_{\mathrm{X}} < $ 4.5 TeV and $ 1.4\times10^{-4}< \Gamma_{\mathrm{X}}/m_{\mathrm{X}} < 5.6\times10^{-2} $ are determined using the modified frequentist approach, where $m_{\mathrm{X}}$ and $\Gamma_{\mathrm{X}}$ are the resonance mass and width, respectively. The results obtained with the 2016 data set are combined statistically with those obtained in 2012 and 2015, corresponding to integrated luminosities of 19.7 and 3.3 fb$^{-1}$ of data recorded at $\sqrt{s} =$ 8 and 13 TeV, respectively. No significant excess is observed above the predictions of the standard model. Using the leading-order cross sections, Randall-Sundrum gravitons with masses below 3.85 and 4.45 TeV are excluded for values of the dimensionless coupling parameter $\tilde{k}=$ 0.1 and 0.2, respectively. For $\tilde{k}=$ 0.01, graviton masses below 1.95 TeV are excluded, except for the region between 1.75 and 1.85 TeV. These are the most stringent limits on Randall-Sundrum graviton production to date. |
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