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| CMS-HIG-18-011 ; CERN-EP-2018-309 | ||
| Search for an exotic decay of the Higgs boson to a pair of light pseudoscalars in the final state with two muons and two b quarks in pp collisions at 13 TeV | ||
| CMS Collaboration | ||
| 15 December 2018 | ||
| Phys. Lett. B 795 (2019) 398 | ||
| Abstract: A search for exotic decays of the Higgs boson to a pair of light pseudoscalar particles ${{\mathrm{a}_1}} $ is performed under the hypothesis that one of the pseudoscalars decays to a pair of opposite sign muons and the other decays to $\mathrm{b\bar{b}}$. Such signatures are predicted in a number of extensions of the standard model (SM), including next-to-minimal supersymmetry and two-Higgs-doublet models with an additional scalar singlet. The results are based on a data set of proton-proton collisions corresponding to an integrated luminosity of 35.9 fb$^{-1}$, accumulated with the CMS experiment at the CERN LHC in 2016 at a centre-of-mass energy of 13 TeV. No statistically significant excess is observed with respect to the SM backgrounds in the search region for pseudoscalar masses from 20 GeV to half of the Higgs boson mass. Upper limits at 95% confidence level are set on the product of the production cross section and branching fraction, $\sigma_{\mathrm{h}}\mathcal{B}(\mathrm{h}\to {{\mathrm{a}_1}} {{\mathrm{a}_1}} \to\mu^{+}\mu^{-}\mathrm{b\bar{b}})$, ranging from 5 to 36 fb, depending on the pseudoscalar mass. Corresponding limits on the branching fraction, assuming the SM prediction for $\sigma_{\mathrm{h}}$, are (1-6)$\times 10^{-4}$. | ||
| Links: e-print arXiv:1812.06359 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
The distribution of $ {\chi ^2} $ in simulated background processes and the signal process with $ {m_{{\mathrm {a}} _1}} = $ 40 GeV. The samples are normalized to unity. |
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Figure 2:
The distribution of $ {\chi _{{\mathrm {b}} {\mathrm {b}}}} $ versus $ {\chi _{{\mathrm {h}}}} $ as defined in Eq. (2) for (left) simulated background processes and (right) the signal process with $ {m_{{\mathrm {a}} _1}} = $ 40 GeV. The contours encircle the area with $ {\chi ^2} < $ 5. The grey scale represents the expected yields at 35.9 fb$^{-1}$. |
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Figure 2-a:
The distribution of $ {\chi _{{\mathrm {b}} {\mathrm {b}}}} $ versus $ {\chi _{{\mathrm {h}}}} $ as defined in Eq. (2) for simulated background processes. The contours encircle the area with $ {\chi ^2} < $ 5. The grey scale represents the expected yields at 35.9 fb$^{-1}$. |
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Figure 2-b:
The distribution of $ {\chi _{{\mathrm {b}} {\mathrm {b}}}} $ versus $ {\chi _{{\mathrm {h}}}} $ as defined in Eq. (2) for the signal process with $ {m_{{\mathrm {a}} _1}} = $ 40 GeV. The contours encircle the area with $ {\chi ^2} < $ 5. The grey scale represents the expected yields at 35.9 fb$^{-1}$. |
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Figure 3:
The distribution of the $ {p_{\mathrm {T}}} $ of the (top left) dimuon and (top right) di- b-jet system, the mass of the (middle left) di- b-jet and (middle right) $ {{\mu}} {{\mu}}{{\mathrm {b}} {\mathrm {b}}}$ system, and (bottom left) the $ {p_{\mathrm {T}}} $ of the $ {{\mu}} {{\mu}}{{\mathrm {b}} {\mathrm {b}}}$ system, all after requiring two muons and two b-tagged jets in the event. Simulated samples are normalised to an integrated luminosity of 35.9 fb$^{-1}$ using their theoretical cross sections. |
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Figure 3-a:
The distribution of the $ {p_{\mathrm {T}}} $ of the dimuon, after requiring two muons and two b-tagged jets in the event. Simulated samples are normalised to an integrated luminosity of 35.9 fb$^{-1}$ using their theoretical cross sections (see Legend in Fig.3-f). |
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Figure 3-b:
The distribution of the $ {p_{\mathrm {T}}} $ di- b-jet system, after requiring two muons and two b-tagged jets in the event. Simulated samples are normalised to an integrated luminosity of 35.9 fb$^{-1}$ using their theoretical cross sections (see Legend in Fig.3-f). |
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Figure 3-c:
The distribution of the mass of the di- b-jet system, after requiring two muons and two b-tagged jets in the event. Simulated samples are normalised to an integrated luminosity of 35.9 fb$^{-1}$ using their theoretical cross sections (see Legend in Fig.3-f). |
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Figure 3-d:
The distribution of the mass of the $ {{\mu}} {{\mu}}{{\mathrm {b}} {\mathrm {b}}}$ system, after requiring two muons and two b-tagged jets in the event. Simulated samples are normalised to an integrated luminosity of 35.9 fb$^{-1}$ using their theoretical cross sections (see Legend in Fig.3-f). |
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Figure 3-e:
The distribution of the $ {p_{\mathrm {T}}} $ of the $ {{\mu}} {{\mu}}{{\mathrm {b}} {\mathrm {b}}}$ system, after requiring two muons and two b-tagged jets in the event. Simulated samples are normalised to an integrated luminosity of 35.9 fb$^{-1}$ using their theoretical cross sections (see Legend in Fig.3-f). |
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Figure 3-f:
Legend for Figs. 3 a-e. |
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Figure 4:
The best fit output to the data under the background-only hypothesis for the (top-left) TL category, (top right) TM category, (bottom left) TT category and (bottom right) all categories, presented together with 68% CL uncertainty band for the background model. |
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Figure 4-a:
The best fit output to the data under the background-only hypothesis for the TL category, presented together with 68% CL uncertainty band for the background model. |
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Figure 4-b:
The best fit output to the data under the background-only hypothesis for the TM category, presented together with 68% CL uncertainty band for the background model. |
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Figure 4-c:
The best fit output to the data under the background-only hypothesis for the TT category, presented together with 68% CL uncertainty band for the background model. |
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Figure 4-d:
The best fit output to the data under the background-only hypothesis for all categories, presented together with 68% CL uncertainty band for the background model. |
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Figure 5:
Observed and expected upper limits at 95% CL on the (left) product of the Higgs boson production cross section and $ {\mathcal {B}({{\mathrm {h}}}\to {{{{\mathrm {a}} _1}} {{{\mathrm {a}} _1}}}\to {{{\mu ^+}} {{\mu ^-}}} {{{\mathrm {b}} {\overline {\mathrm {b}}}}})} $ and (right) the branching fraction as a function of $ {m_{{\mathrm {a}} _1}} $. The inner and outer bands indicate the regions containing the distribution of limits located within 68 and 95% confidence intervals, respectively, of the expectation under the background-only hypothesis. |
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Figure 5-a:
Observed and expected upper limits at 95% CL on the product of the Higgs boson production cross section and $ {\mathcal {B}({{\mathrm {h}}}\to {{{{\mathrm {a}} _1}} {{{\mathrm {a}} _1}}}\to {{{\mu ^+}} {{\mu ^-}}} {{{\mathrm {b}} {\overline {\mathrm {b}}}}})} $. The inner and outer bands indicate the regions containing the distribution of limits located within 68 and 95% confidence intervals, respectively, of the expectation under the background-only hypothesis. |
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Figure 5-b:
Observed and expected upper limits at 95% CL on the the branching fraction as a function of $ {m_{{\mathrm {a}} _1}} $. The inner and outer bands indicate the regions containing the distribution of limits located within 68 and 95% confidence intervals, respectively, of the expectation under the background-only hypothesis. |
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Figure 6:
Observed upper limits at 95% CL on $\mathcal {B}({\mathrm {h}} \to {{{\mathrm {a}} _1}} {{{\mathrm {a}} _1}})$ in the plane of ($ {m_{{\mathrm {a}} _1}}, {\tan\beta} $) for (left) type-III and (right) type-IV 2HDM+S, using only the $ {{{{\mu ^+}} {{\mu ^-}}} {{\mathrm {b}} {\overline {\mathrm {b}}}}} $ signal. |
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Figure 6-a:
Observed upper limits at 95% CL on $\mathcal {B}({\mathrm {h}} \to {{{\mathrm {a}} _1}} {{{\mathrm {a}} _1}})$ in the plane of ($ {m_{{\mathrm {a}} _1}}, {\tan\beta} $) for type-III 2HDM+S, using only the $ {{{{\mu ^+}} {{\mu ^-}}} {{\mathrm {b}} {\overline {\mathrm {b}}}}} $ signal. |
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Figure 6-b:
Observed upper limits at 95% CL on $\mathcal {B}({\mathrm {h}} \to {{{\mathrm {a}} _1}} {{{\mathrm {a}} _1}})$ in the plane of ($ {m_{{\mathrm {a}} _1}}, {\tan\beta} $) for type-IV 2HDM+S, using only the $ {{{{\mu ^+}} {{\mu ^-}}} {{\mathrm {b}} {\overline {\mathrm {b}}}}} $ signal. |
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Figure 7:
Observed upper limits at 95% CL on $\mathcal {B}({\mathrm {h}} \to {{{\mathrm {a}} _1}} {{{\mathrm {a}} _1}})$ in the plane of ($ {m_{{\mathrm {a}} _1}}, {\tan\beta} $) for type-III 2HDM+S, including $ {{{{\mu ^+}} {{\mu ^-}}} {{\tau}^{+} {\tau}^{-}}} $ signal that is misidentified as ${{{{\mu ^+}} {{\mu ^-}}} {{\mathrm {b}} {\overline {\mathrm {b}}}}}$. |
| Tables | |
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Table 1:
Event yields for simulated processes and data after requiring two muons and two b jets (${{{{\mu ^+}} {{\mu ^-}}} {{\mathrm {b}} {\overline {\mathrm {b}}}}}$ selection) and after the final selection. The expected number of simulated events is normalised to the integrated luminosity of 35.9 fb$^{-1}$. Uncertainties are only statistical. |
| Summary |
| A search for the Higgs boson decay to a pair of new pseudoscalars ${\mathrm{h}}\to{{\mathrm{a}_1}} {{\mathrm{a}_1}} \to mmbb$, motivated by the next-to-minimal supersymmetric standard model and other extensions to two-Higgs-doublet models, is carried out using a sample of proton-proton collision data corresponding to an integrated luminosity of 35.9 fb$^{-1}$ at 13 TeV centre-of-mass energy. No statistically significant excess is found in data with respect to the background prediction. The results of the analysis are presented in the form of upper limits, at 95% confidence level, on the product of the Higgs boson production cross section and branching fraction, $\sigma_{\mathrm{h}}\mathcal{B}(\mathrm{h}\to {{\mathrm{a}_1}} {{\mathrm{a}_1}} \to\mu^{+}\mu^{-}\mathrm{b\bar{b}})$, as well as on the Higgs boson branching fraction assuming the SM prediction of $\sigma_{\mathrm{h}}$. The former ranges between 5 to 36 fb, depending on ${m_{\mathrm{a}_1}} $. The corresponding limits on the branching fraction are (1-6)$\times 10^{-4}$ for the mass range of 20 $\leq{m_{\mathrm{a}_1}} \leq $ 62.5 GeV. In an analysis performed by ATLAS [18], the limits on the branching fraction range between $2\times10^{-4}$ and $10^{-3}$. Compared with the similar analysis in Run I [14], the expected upper limits on the branching fraction are improved by more than a factor of two. |
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