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| CMS-PAS-EXO-20-008 | ||
| Search for heavy resonances decaying to b quarks in proton-proton collisions at $\sqrt{s}=$ 13 TeV | ||
| CMS Collaboration | ||
| July 2021 | ||
| Abstract: Searches are performed for resonances decaying to two jets, with at least one jet originating from a b quark, in proton-proton collisions at $\sqrt{s}=$ 13 TeV. The dataset corresponds to an integrated luminosity of 137 fb$^{-1}$ collected by the CMS detector at the LHC. Jets are identified as containing energetic b hadrons using a deep neural network b tagger. The invariant mass spectrum of b-tagged dijets is well described by a smooth parameterization and no evidence for the production of new particles is observed. Cross-section upper limits are set on resonances decaying into b quarks. These limits exclude at 95% confidence level models of Z' bosons with a mass less than 2.4 TeV, and an excited b quark with mass less than 4.0 TeV. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, Submitted to PRD. |
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| Figures | |
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Figure 1:
Signal shapes of b* from the process bg $\to $ b* $\to $ bg. These reconstructed dijet mass spectra show wide jets from the PYTHIA 8 MC event generator including simulation of the CMS detector. |
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Figure 2:
The acceptance times efficiency of the event selection for a $\mathrm{Z'} \to \mathrm{b} {}\mathrm{\bar{b}} $ resonance as a function of the generated mass. |
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Figure 3:
The dijet mass spectra with both jets b tagged (points) are fit with background functional forms (solid curves). The 2016 data is fit with a 3 parameter function (left), 2017 is fit with 4 parameters (middle), and 2018 with 3 parameters (right). The lower panel shows the pull, (data-fit)/uncertainty, in units of the statistical uncertainty. |
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Figure 3-a:
The dijet mass spectra with both jets b tagged (points) are fit with background functional forms (solid curves). The 2016 data is fit with a 3 parameter function (left), 2017 is fit with 4 parameters (middle), and 2018 with 3 parameters (right). The lower panel shows the pull, (data-fit)/uncertainty, in units of the statistical uncertainty. |
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Figure 3-b:
The dijet mass spectra with both jets b tagged (points) are fit with background functional forms (solid curves). The 2016 data is fit with a 3 parameter function (left), 2017 is fit with 4 parameters (middle), and 2018 with 3 parameters (right). The lower panel shows the pull, (data-fit)/uncertainty, in units of the statistical uncertainty. |
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Figure 3-c:
The dijet mass spectra with both jets b tagged (points) are fit with background functional forms (solid curves). The 2016 data is fit with a 3 parameter function (left), 2017 is fit with 4 parameters (middle), and 2018 with 3 parameters (right). The lower panel shows the pull, (data-fit)/uncertainty, in units of the statistical uncertainty. |
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Figure 4:
Same as Fig. 3 for the category where only one jet is b tagged. A background functional form with 3 parameters is used to fit the data in 2016 (left), 2017 (middle) and 2018 (right). |
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Figure 4-a:
Same as Fig. 3 for the category where only one jet is b tagged. A background functional form with 3 parameters is used to fit the data in 2016 (left), 2017 (middle) and 2018 (right). |
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Figure 4-b:
Same as Fig. 3 for the category where only one jet is b tagged. A background functional form with 3 parameters is used to fit the data in 2016 (left), 2017 (middle) and 2018 (right). |
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Figure 4-c:
Same as Fig. 3 for the category where only one jet is b tagged. A background functional form with 3 parameters is used to fit the data in 2016 (left), 2017 (middle) and 2018 (right). |
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Figure 5:
Same as Fig. 3 for the category where at least one jet contains a muon. The 2016 data is fit with a 4 parameter function (left), 2017 is fit with 3 parameters (middle), and 2018 with 3 parameters (right) |
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Figure 5-a:
Same as Fig. 3 for the category where at least one jet contains a muon. The 2016 data is fit with a 4 parameter function (left), 2017 is fit with 3 parameters (middle), and 2018 with 3 parameters (right) |
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Figure 5-b:
Same as Fig. 3 for the category where at least one jet contains a muon. The 2016 data is fit with a 4 parameter function (left), 2017 is fit with 3 parameters (middle), and 2018 with 3 parameters (right) |
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Figure 5-c:
Same as Fig. 3 for the category where at least one jet contains a muon. The 2016 data is fit with a 4 parameter function (left), 2017 is fit with 3 parameters (middle), and 2018 with 3 parameters (right) |
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Figure 6:
Same as Fig. 3 for the category where at least one jet is b tagged. The 2016 data is fit with a 5 parameter function (left), 2017 is fit with 5 parameters (middle), and 2018 with 4 parameters (right). |
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Figure 6-a:
Same as Fig. 3 for the category where at least one jet is b tagged. The 2016 data is fit with a 5 parameter function (left), 2017 is fit with 5 parameters (middle), and 2018 with 4 parameters (right). |
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Figure 6-b:
Same as Fig. 3 for the category where at least one jet is b tagged. The 2016 data is fit with a 5 parameter function (left), 2017 is fit with 5 parameters (middle), and 2018 with 4 parameters (right). |
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Figure 6-c:
Same as Fig. 3 for the category where at least one jet is b tagged. The 2016 data is fit with a 5 parameter function (left), 2017 is fit with 5 parameters (middle), and 2018 with 4 parameters (right). |
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Figure 7:
The observed 95% CL upper limits (solid curve) on the product of the cross section times branching fraction (left), and multiplied by signal acceptance accounting for kinematic requirements (right), for a resonance decaying to $\mathrm{b} {}\mathrm{\bar{b}} $. The corresponding expected limits (dashed curve) and their variations at the 1 and 2 standard deviation levels (shaded bands) are also shown. Limits are compared to predicted cross sections for Z' bosons from the sequential standard model and the heavy vector triplet models A and B. |
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Figure 7-a:
The observed 95% CL upper limits (solid curve) on the product of the cross section times branching fraction (left), and multiplied by signal acceptance accounting for kinematic requirements (right), for a resonance decaying to $\mathrm{b} {}\mathrm{\bar{b}} $. The corresponding expected limits (dashed curve) and their variations at the 1 and 2 standard deviation levels (shaded bands) are also shown. Limits are compared to predicted cross sections for Z' bosons from the sequential standard model and the heavy vector triplet models A and B. |
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Figure 7-b:
The observed 95% CL upper limits (solid curve) on the product of the cross section times branching fraction (left), and multiplied by signal acceptance accounting for kinematic requirements (right), for a resonance decaying to $\mathrm{b} {}\mathrm{\bar{b}} $. The corresponding expected limits (dashed curve) and their variations at the 1 and 2 standard deviation levels (shaded bands) are also shown. Limits are compared to predicted cross sections for Z' bosons from the sequential standard model and the heavy vector triplet models A and B. |
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Figure 8:
The coupling strengths to SM bosons (${g_\text {H}}$) and fermions (${g_\text {F}}$) of a Z' boson with mass 2 TeV (red hatched) and 2.5 TeV (blue hatched), which are excluded at 95% CL for the HVT model. The benchmark scenarios corresponding to HVT models A and B are represented by a purple cross and a red point, respectively. The gray shaded area corresponds to the region where the resonance natural width is predicted to be larger than the typical experimental resolution, and thus the narrow-width approximation is not fulfilled. |
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Figure 9:
The observed 95% CL upper limits on the product of the cross section, branching fraction, and acceptance for dijet resonances decaying to a b quark and a gluon (points). The corresponding expected limits (short 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 single b* production (dot dashed), the resonant component of $\overline {\mathrm {b}}{\mathrm{b} ^*}$ production (long dashed), and the total b* signal from the sum of these two processes (double dot dashed). |
| Summary |
| A search for heavy resonances decaying into b quarks has been presented. The data sample was collected by the CMS experiment at $\sqrt{s} = $ 13 TeV during 2016, 2017, and 2018 and corresponds to an integrated luminosity of 137 fb$^{-1}$. Upper limits in the range 0.4-400 fb are set on the product of the cross section of the resonance and the branching fraction to b quarks. Signals of Z' bosons decaying to pairs of b quarks are considered, for both previously explored SSM models, and also for a new heavy vector triplet model. The decays of Z' bosons in both the SSM and the HVT model A are excluded at 95% CL for masses less than 2.4 TeV, and limits are set on the coupling strength of the HVT boson to SM bosons and fermions. Signals of an excited b quark are considered, for both a previously explored channel, bg $\to$ b* $\to$ bg, and a new channel, $\mathrm{q\bar{q}} \to \overline{\mathrm{b}}{\mathrm{b}^*} \to \overline{\mathrm{b}} \mathrm{bg}$, and the excited b quark is excluded at 95% CL for masses less than 4.0 TeV. With the inclusion of the $\overline{\mathrm{b}}{\mathrm{b}^*}$ process, this is the most stringent exclusion of the excited b quark. |
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