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| CMS-PAS-EXO-17-026 | ||
| Searches for dijet resonances in pp collisions at $\sqrt{s}= $ 13 TeV using the 2016 and 2017 datasets | ||
| CMS Collaboration | ||
| September 2018 | ||
| Abstract: Searches are presented for resonances decaying to dijet final states in proton-proton collisions at $\sqrt{s}= $ 13 TeV. A high-mass search, for resonances with mass above 1.8 TeV, is performed using dijets reconstructed from data corresponding to an integrated luminosity of 77.8 fb$^{-1}$. The main QCD background is predicted both by fitting the data with an empirical functional form, and with a data-driven method via a $|\Delta\eta|$ sideband. The dijet mass spectrum is well described by both methods and no significant evidence for the production of new particles is observed. Upper limits at 95% confidence level are reported on the production cross section for narrow resonances with masses above 1.8 TeV extending previous searches. Limits are placed on the mass of dijet resonances within various models of new physics. | ||
| Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures & Tables | Summary | Additional Figures | References | CMS Publications |
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| Figures | |
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Figure 1:
The pseudorapidity separation between the two wide-jets for the signal and control regions. Data (black points) are compared to QCD predictions from the Pythia-8 MC with detector simulation (red line) normalized to the data. A signal from an RS graviton decaying to two quarks is also shown (blue line) normalized to the same number of events as the data. |
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Figure 2:
The dijet mass spectra of the data and Pythia simulation in the SR (black points and red line), $ {\mathrm {CR}_{\mathrm {middle}}} $ (triangles and blue line), and $ {\mathrm {CR}_{\mathrm {high}}} $ (crosses and magenta line). |
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Figure 3:
Event displays of the event with the highest dijet invariant mass at 8 TeV. The grouping of the jets into two wide jets is shown in the bottom event display and discussed in the text. |
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Figure 3-a:
Event display of the event with the highest dijet invariant mass at 8 TeV. The grouping of the jets into two wide jets is shown in the bottom event display and discussed in the text. |
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Figure 3-b:
Event display of the event with the highest dijet invariant mass at 8 TeV. The grouping of the jets into two wide jets is shown in the bottom event display and discussed in the text. |
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Figure 3-c:
Event display of the event with the highest dijet invariant mass at 8 TeV. The grouping of the jets into two wide jets is shown in the bottom event display and discussed in the text. |
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Figure 4:
Event displays of the event with the second highest dijet invariant mass at 7.9 TeV. |
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Figure 4-a:
Event display of the event with the second highest dijet invariant mass at 7.9 TeV. |
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Figure 4-b:
Event display of the event with the second highest dijet invariant mass at 7.9 TeV. |
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Figure 4-c:
Event display of the event with the second highest dijet invariant mass at 7.9 TeV. |
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Figure 5:
Left: $ {R_{\mathrm {ext.}}^{\mathrm {aux.}}} $ auxiliary transfer factor for data (black points) and pythia (blue line) on the top, along with their ratio fitted with the correction function on the bottom (magenta line with 68% CL error band). Right: $ {R_{\mathrm {ext.}}} $ transfer factor for data (black points), Pythia (blue line), Powheg (red line) and corrected Pythia (magenta line) shown on the top. The ratio of data to Pythia (black points) fitted with the correction function (blue line), along with the ratio of Powheg to Pythia (red line), and the ratio of corrected Pythia to uncorrected Pythia (magenta line) are shown on the bottom. The corrected Pythia transfer factor (magenta line) using $ {\mathrm {CR}_{\mathrm {middle}}} $ agrees with the data one (blue line). |
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Figure 5-a:
$ {R_{\mathrm {ext.}}^{\mathrm {aux.}}} $ auxiliary transfer factor for data (black points) and pythia (blue line) on the top, along with their ratio fitted with the correction function on the bottom (magenta line with 68% CL error band). |
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Figure 5-b:
$ {R_{\mathrm {ext.}}} $ transfer factor for data (black points), Pythia (blue line), Powheg (red line) and corrected Pythia (magenta line) shown on the top. The ratio of data to Pythia (black points) fitted with the correction function (blue line), along with the ratio of Powheg to Pythia (red line), and the ratio of corrected Pythia to uncorrected Pythia (magenta line) are shown on the bottom. The corrected Pythia transfer factor (magenta line) using $ {\mathrm {CR}_{\mathrm {middle}}} $ agrees with the data one (blue line). |
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Figure 6:
Dijet mass spectra in the signal region (points) compared to a fitted parameterization of the background (solid curve) and the one obtained from the control region (green squares). For the displayed signal a cross section at the 95% CL observed exclusion limit is being used. The lower panel shows the difference between the data and the fitted parametrization (red), and the data and the prediction obtained from the control region (green), divided by the statistical uncertainty of the data, which for the ratio method includes the one in $ {\mathrm {CR}_{\mathrm {high}}} $ as well. The ratio of the expected signal showed in the upper panel to the statistical uncertainty of the data is also shown for three different resonance masses and signals models. |
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Figure 7:
The observed 95% CL upper limits on the product of the cross section, branching fraction, and acceptance for dijet resonances decaying to quark-quark (top left), quark-gluon (top right), gluon-gluon (bottom left), and for RS gravitons (bottom right). The corresponding expected limits (dashed) and their variations at the 1 and 2 standard deviation levels (shaded bands) are also shown. Limits are compared to predicted cross sections for string resonances [18,19], excited quarks [24,25], axigluons [21], colorons [23], scalar diquarks [20], color-octet scalars [26], new gauge bosons W' and Z' with SM-like couplings [27], dark matter mediators for $ {m_{\text {DM}}} =$ 1 GeV [28,29], and RS gravitons [30]. |
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Figure 7-a:
The observed 95% CL upper limits on the product of the cross section, branching fraction, and acceptance for dijet resonances decaying to quark-quark. The corresponding expected limits (dashed) and their variations at the 1 and 2 standard deviation levels (shaded bands) are also shown. Limits are compared to predicted cross sections for axigluons [21], colorons [23], scalar diquarks [20], new gauge bosons W' and Z' with SM-like couplings [27], and dark matter mediators for $ {m_{\text {DM}}} =$ 1 GeV [28,29]. |
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Figure 7-b:
The observed 95% CL upper limits on the product of the cross section, branching fraction, and acceptance for dijet resonances decaying to quark-gluon. The corresponding expected limits (dashed) and their variations at the 1 and 2 standard deviation levels (shaded bands) are also shown. Limits are compared to predicted cross sections for string resonances [18,19] and excited quarks [24,25]. |
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Figure 7-c:
The observed 95% CL upper limits on the product of the cross section, branching fraction, and acceptance for dijet resonances decaying to gluon-gluon.The corresponding expected limits (dashed) and their variations at the 1 and 2 standard deviation levels (shaded bands) are also shown. Limits are compared to predicted cross sections for color-octet scalars [26]. |
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Figure 7-d:
The observed 95% CL upper limits on the product of the cross section, branching fraction, and acceptance for RS gravitons. The corresponding expected limits (dashed) and their variations at the 1 and 2 standard deviation levels (shaded bands) are also shown. Limits are compared to predicted cross sections for RS gravitons [30]. |
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Figure 8:
The observed 95% CL upper limits on the product of the cross section, branching fraction, and acceptance for quark-quark, quark-gluon, and gluon-gluon type dijet resonances. Limits are compared to predicted cross sections for string resonances [18,19], excited quarks [24,25], axigluons [21], colorons [23], scalar diquarks [20], color-octet scalars [26], new gauge bosons W' and Z' with SM-like couplings [27], dark matter mediators for $ {m_{\text {DM}}} =$ 1 GeV [28,29], and RS gravitons [30]. |
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Figure 9:
The 95% CL upper limits on the universal quark coupling $ {g_{\mathrm {q}}} ^{\prime}$ as a function of resonance mass for a leptophobic Z' resonance that only couples to quarks. The observed limits (solid), expected limits (dashed) and their variation at the 1 and 2 standard deviation levels (shaded bands) are shown. Dotted horizontal lines show the coupling strength for which the cross section for dijet production in this model is the same as for a DM mediator. |
| Tables | |
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Table 1:
Observed and expected mass limits at 95% CL from this analysis with 77.8 fb$^{-1}$ at $\sqrt {s}=$ 13 TeV compared to previously published limits on narrow resonances from CMS with 36 fb$^{-1}$ at $\sqrt {s}=$ 13 TeV [1] The listed models are excluded between 1.8 TeV and the indicated mass limit by this analysis. The Z' model within the mass interval between 3.1 and 3.3 TeV is also excluded. |
| Summary |
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Searches for resonances decaying into a pair of jets have been performed using proton-proton collisions at $\sqrt{s}=$ 13 TeV corresponding to an integrated luminosity of up to 77.8 fb$^{-1}$. The dijet mass spectra are observed to be smoothly falling distributions, and the QCD background is predicted using a new method for ${m_{\mathrm{jj}}} > $ 2.4 TeV, utilizing a control region in a $|\Delta \eta|$ sideband. This new background prediction method is orthogonal and complementary to the existing one and with a more robust background prediction. In the analyzed data samples, there is no evidence for resonant particle production. Generic upper limits are presented on the product of the cross section, the branching fraction, and the acceptance for narrow quark-quark, quark-gluon, and gluon-gluon resonances that are applicable to any model of narrow dijet resonance production. String resonances with masses below 7.6 TeV are excluded at 95% confidence level, as are scalar diquarks below 7.3 TeV, axigluons and colorons below 6.2 TeV, excited quarks below 6.0 TeV, color-octet scalars below 3.7 TeV, W' bosons below 3.6 TeV, Z' bosons with SM-like couplings below 2.9 TeV and between 3.1 and 3.3 TeV, Randall-Sundrum gravitons below 2.4 TeV, and dark matter mediators below 2.5 TeV. This extends previously reported limits in the dijet channel. |
| Additional Figures | |
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Additional Figure 1:
Ratio of expected 95% CL limits between the fit method and the ratio method when both start from 2.4 TeV (red line) and when the fit method starts at 1.5 TeV and the ratio method at 2.4 TeV (black line). |
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Additional Figure 2:
Local significance for a narrow resonance from the fit method (red) and the ratio method search (blue) for $ {\mathrm {q}} {\mathrm {q}} $ resonances. |
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Additional Figure 3:
Local significance for a narrow resonance from the fit method (red) and the ratio method search (blue) for $ {\mathrm {q}} {\mathrm {g}} $ resonances. |
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Additional Figure 4:
Local significance for a narrow resonance from the fit method (red) and the ratio method search (blue) for $ {\mathrm {g}} {\mathrm {g}} $ resonances. |
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