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| CMS-PAS-HIG-18-021 | ||
| Search for a light charged Higgs boson in the $\mathrm{ H^{\pm} \to cs }$ channel at 13 TeV | ||
| CMS Collaboration | ||
| November 2019 | ||
| Abstract: A search is conducted for a low-mass charged Higgs boson produced in a top quark decay and subsequently decaying into a charm and an antistrange quark. The data sample was recorded in proton-proton collisions at $\sqrt{s}= $ 13 TeV by the CMS experiment at the LHC and corresponds to an integrated luminosity of 35.9 fb$^{-1}$. The signal search is conducted in the process of top-quark pair production, where one top quark decays to a bottom quark and a charged Higgs boson, and the other to a bottom quark and a W boson. With the W boson decaying to a charged lepton (electron or muon) and a neutrino, the final state comprises an isolated lepton, missing transverse momentum, and at least four jets, of which two are tagged as b jets. To enhance the search sensitivity, one of the jets originating from the charged Higgs boson is required to satisfy a charm tagging requirement. No significant excess beyond standard model predictions is found in the dijet invariant mass distribution. An upper limit in the range 0.20-1.65% is set on the branching fraction of the top quark decay to the charged Higgs boson and bottom quark for a Higgs mass between 80 and 160 GeV. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, PRD 102 (2020) 072001. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Production of ${\mathrm{t} {}\mathrm{\bar{t}}}$ from gluon-gluon scattering. The left plot shows the signal process in which the ${\mathrm{t} {}\mathrm{\bar{t}}}$ pair decay products include a charged Higgs boson. The right plot shows the SM decay of the ${\mathrm{t} {}\mathrm{\bar{t}}}$ pair in the semileptonic decay channel. |
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Figure 2:
Distributions of ${m_\text {jj}}$, prior to the fit to data, of the two highest ${p_{\mathrm {T}}}$ light jets for the muon+jets channel (left column) and the electron+jets channel (right column). The two distributions in the top row are obtained using reconstructed jets. On the other hand, the distributions in the bottom row are calculated using kinematic fitted jets after the kinematic fit selection. The mean of the invariant mass distribution from the kinematic fitted jets is closer to the W mass as compared to that of reconstructed jets. The uncertainty band includes statistical as well as systematic uncertainties. |
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Figure 2-a:
Distributions of ${m_\text {jj}}$, prior to the fit to data, of the two highest ${p_{\mathrm {T}}}$ light jets for the muon+jets channel (left column) and the electron+jets channel (right column). The two distributions in the top row are obtained using reconstructed jets. On the other hand, the distributions in the bottom row are calculated using kinematic fitted jets after the kinematic fit selection. The mean of the invariant mass distribution from the kinematic fitted jets is closer to the W mass as compared to that of reconstructed jets. The uncertainty band includes statistical as well as systematic uncertainties. |
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Figure 2-b:
Distributions of ${m_\text {jj}}$, prior to the fit to data, of the two highest ${p_{\mathrm {T}}}$ light jets for the muon+jets channel (left column) and the electron+jets channel (right column). The two distributions in the top row are obtained using reconstructed jets. On the other hand, the distributions in the bottom row are calculated using kinematic fitted jets after the kinematic fit selection. The mean of the invariant mass distribution from the kinematic fitted jets is closer to the W mass as compared to that of reconstructed jets. The uncertainty band includes statistical as well as systematic uncertainties. |
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Figure 2-c:
Distributions of ${m_\text {jj}}$, prior to the fit to data, of the two highest ${p_{\mathrm {T}}}$ light jets for the muon+jets channel (left column) and the electron+jets channel (right column). The two distributions in the top row are obtained using reconstructed jets. On the other hand, the distributions in the bottom row are calculated using kinematic fitted jets after the kinematic fit selection. The mean of the invariant mass distribution from the kinematic fitted jets is closer to the W mass as compared to that of reconstructed jets. The uncertainty band includes statistical as well as systematic uncertainties. |
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Figure 2-d:
Distributions of ${m_\text {jj}}$, prior to the fit to data, of the two highest ${p_{\mathrm {T}}}$ light jets for the muon+jets channel (left column) and the electron+jets channel (right column). The two distributions in the top row are obtained using reconstructed jets. On the other hand, the distributions in the bottom row are calculated using kinematic fitted jets after the kinematic fit selection. The mean of the invariant mass distribution from the kinematic fitted jets is closer to the W mass as compared to that of reconstructed jets. The uncertainty band includes statistical as well as systematic uncertainties. |
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Figure 3:
Distributions of ${m_\text {jj}}$, after a background-only fit to the data, in the exclusive charm categories for the muon + jets (left column) and electron + jets (right column) channels. The upper row shows the exclusive loose category, the middle row shows the exclusive medium category, and the lower row shows the exclusive tight category. The expected signal significance (prior to the fit) can be observed to vary across the different categories. The uncertainty band includes statistical as well as systematic uncertainties after the background-only fit. |
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Figure 3-a:
Distributions of ${m_\text {jj}}$, after a background-only fit to the data, in the exclusive charm categories for the muon + jets (left column) and electron + jets (right column) channels. The upper row shows the exclusive loose category, the middle row shows the exclusive medium category, and the lower row shows the exclusive tight category. The expected signal significance (prior to the fit) can be observed to vary across the different categories. The uncertainty band includes statistical as well as systematic uncertainties after the background-only fit. |
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Figure 3-b:
Distributions of ${m_\text {jj}}$, after a background-only fit to the data, in the exclusive charm categories for the muon + jets (left column) and electron + jets (right column) channels. The upper row shows the exclusive loose category, the middle row shows the exclusive medium category, and the lower row shows the exclusive tight category. The expected signal significance (prior to the fit) can be observed to vary across the different categories. The uncertainty band includes statistical as well as systematic uncertainties after the background-only fit. |
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Figure 3-c:
Distributions of ${m_\text {jj}}$, after a background-only fit to the data, in the exclusive charm categories for the muon + jets (left column) and electron + jets (right column) channels. The upper row shows the exclusive loose category, the middle row shows the exclusive medium category, and the lower row shows the exclusive tight category. The expected signal significance (prior to the fit) can be observed to vary across the different categories. The uncertainty band includes statistical as well as systematic uncertainties after the background-only fit. |
png pdf |
Figure 3-d:
Distributions of ${m_\text {jj}}$, after a background-only fit to the data, in the exclusive charm categories for the muon + jets (left column) and electron + jets (right column) channels. The upper row shows the exclusive loose category, the middle row shows the exclusive medium category, and the lower row shows the exclusive tight category. The expected signal significance (prior to the fit) can be observed to vary across the different categories. The uncertainty band includes statistical as well as systematic uncertainties after the background-only fit. |
png pdf |
Figure 3-e:
Distributions of ${m_\text {jj}}$, after a background-only fit to the data, in the exclusive charm categories for the muon + jets (left column) and electron + jets (right column) channels. The upper row shows the exclusive loose category, the middle row shows the exclusive medium category, and the lower row shows the exclusive tight category. The expected signal significance (prior to the fit) can be observed to vary across the different categories. The uncertainty band includes statistical as well as systematic uncertainties after the background-only fit. |
png pdf |
Figure 3-f:
Distributions of ${m_\text {jj}}$, after a background-only fit to the data, in the exclusive charm categories for the muon + jets (left column) and electron + jets (right column) channels. The upper row shows the exclusive loose category, the middle row shows the exclusive medium category, and the lower row shows the exclusive tight category. The expected signal significance (prior to the fit) can be observed to vary across the different categories. The uncertainty band includes statistical as well as systematic uncertainties after the background-only fit. |
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Figure 4:
The expected and observed upper limits in % on $\mathcal {B}(\mathrm{t} \to \mathrm{H}^{+} \mathrm{b})$ as a function of $m_{\mathrm{H}^{+}}$ using ${m_\text {jj}}$ after the individual charm tagging categories have been combined, for the muon + jets (upper left), electron + jets (upper right), and combined (bottom) channels. |
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Figure 4-a:
The expected and observed upper limits in % on $\mathcal {B}(\mathrm{t} \to \mathrm{H}^{+} \mathrm{b})$ as a function of $m_{\mathrm{H}^{+}}$ using ${m_\text {jj}}$ after the individual charm tagging categories have been combined, for the muon + jets (upper left), electron + jets (upper right), and combined (bottom) channels. |
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Figure 4-b:
The expected and observed upper limits in % on $\mathcal {B}(\mathrm{t} \to \mathrm{H}^{+} \mathrm{b})$ as a function of $m_{\mathrm{H}^{+}}$ using ${m_\text {jj}}$ after the individual charm tagging categories have been combined, for the muon + jets (upper left), electron + jets (upper right), and combined (bottom) channels. |
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Figure 4-c:
The expected and observed upper limits in % on $\mathcal {B}(\mathrm{t} \to \mathrm{H}^{+} \mathrm{b})$ as a function of $m_{\mathrm{H}^{+}}$ using ${m_\text {jj}}$ after the individual charm tagging categories have been combined, for the muon + jets (upper left), electron + jets (upper right), and combined (bottom) channels. |
| Tables | |
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Table 1:
Expected event yields for different signal mass scenarios and backgrounds in each of the channels and event categories. The number of events, along with the uncertainty (including statistical and systematic effects), is shown. The yields for background processes are obtained after a background-only fit to the data. The total uncertainty on the background process is calculated by taking into account all the positive as well as negative correlations among the fit parameters. |
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Table 2:
Systematic and statistical uncertainties in %, prior to the fit to data, for the exclusive charm categories in the muon (electron) channel. The "--" indicates that the corresponding uncertainties are not considered for the given process. |
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Table 3:
Expected and observed 95% CL exclusion limits in % on $\mathcal {B}(\mathrm{t} \to \mathrm{H}^{+} \mathrm{b})$ for the muon (electron) channel, after the individual charm tagging categories have been combined. |
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Table 4:
Expected and observed 95% CL exclusion limits in % on $\mathcal {B}(\mathrm{t} \to \mathrm{H}^{+} \mathrm{b})$, after the individual charm tagging categories and the electron and muon channels have been combined. |
| Summary |
| A search for a light charged Higgs boson ${\mathrm{\widetilde{H}^{\pm_j}}}$ has been performed in the muon + jets and electron + jets channels at $\sqrt{s}=$ 13 TeV, using a data sample with an integrated luminosity of 35.9 fb$^{-1}$. The observed and predicted number of events are in agreement within the statistical and systematic uncertainties as shown in Table 1. In the absence of observed signal, an exclusion limit at 95% confidence level on the branching ratio $\mathcal{B}(\mathrm{t} \to \mathrm{H}^{+}\mathrm{b})$ has been computed by assuming $\mathcal{B}(\mathrm{H}^{+} \to \mathrm{c}\mathrm{\bar{s}}) =$ 100%. The observed exclusion limits are in the range, depending on the $\mathrm{H}^{+}$ mass, 0.29-2.12%, 0.27-3.29%, and 0.20-1.65% for the muon + jets, electron + jets, and combined channels, respectively. The expected exclusion limits from 13 TeV are better by a factor of ${\approx}$4, as compared to those obtained from earlier CMS results at 8 TeV [15]. |
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