CMS-HIG-15-009

CMS-HIG-15-009 ; CERN-EP-2017-159
Search for a light pseudoscalar Higgs boson produced in association with bottom quarks in pp collisions at $ \sqrt{s} = $ 8 TeV
CMS Collaboration
23 July 2017
JHEP 11 (2017) 010
Abstract: A search for a light pseudoscalar Higgs boson (A) produced in association with bottom quarks and decaying into a muon pair is reported. The search uses 19.7 fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of 8 TeV, collected by the CMS experiment. No signal is observed in the dimuon mass range from 25 to 60 GeV. Upper limits on the cross section times branching fraction, $\sigma(\mathrm{ p }\mathrm{ p }\to \mathrm{ b \bar{b} }\mathrm{A})\, \mathcal{B}(\mathrm{A}\to\mu\mu)$, are set.
Links: e-print arXiv:1707.07283 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ;

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: The transverse momentum of the leading (left) and the subleading (right) muon for data (dots) and simulation (histograms). The histograms for simulated backgrounds are stacked. The histogram labeled as MC(Top) shows the sum of the single top and top quark pair production processes. The expected signal is shown assuming a signal cross section times branching fraction of 350 fb. The background is normalized to the number of events expected from simulation. In the lower panel, the ratio of the number of events in data and background simulation is shown.
png pdf	Figure 1-a: The transverse momentum of the leading muon for data (dots) and simulation (histograms). The histograms for simulated backgrounds are stacked. The histogram labeled as MC(Top) shows the sum of the single top and top quark pair production processes. The expected signal is shown assuming a signal cross section times branching fraction of 350 fb. The background is normalized to the number of events expected from simulation. In the lower panel, the ratio of the number of events in data and background simulation is shown.
png pdf	Figure 1-b: The transverse momentum of the subleading muon for data (dots) and simulation (histograms). The histograms for simulated backgrounds are stacked. The histogram labeled as MC(Top) shows the sum of the single top and top quark pair production processes. The expected signal is shown assuming a signal cross section times branching fraction of 350 fb. The background is normalized to the number of events expected from simulation. In the lower panel, the ratio of the number of events in data and background simulation is shown.
png pdf	Figure 2: The transverse momentum of the leading ${p_{\mathrm {T}}}$ b jet (left) and the missing transverse momentum (right) for data (dots) and simulation (histograms). The histograms for simulated backgrounds are stacked. The histogram labeled as MC(Top) shows the sum of the single top and top quark pair production processes. The expected signal is shown assuming a signal cross section times branching fraction of 350 fb. The background is normalized to the number of events expected from simulation. In the lower panel, the ratio of the number of events in data and background simulation is shown.
png pdf	Figure 2-a: The transverse momentum of the leading ${p_{\mathrm {T}}}$ b jet for data (dots) and simulation (histograms). The histograms for simulated backgrounds are stacked. The histogram labeled as MC(Top) shows the sum of the single top and top quark pair production processes. The expected signal is shown assuming a signal cross section times branching fraction of 350 fb. The background is normalized to the number of events expected from simulation. In the lower panel, the ratio of the number of events in data and background simulation is shown.
png pdf	Figure 2-b: The missing transverse momentum for data (dots) and simulation (histograms). The histograms for simulated backgrounds are stacked. The histogram labeled as MC(Top) shows the sum of the single top and top quark pair production processes. The expected signal is shown assuming a signal cross section times branching fraction of 350 fb. The background is normalized to the number of events expected from simulation. In the lower panel, the ratio of the number of events in data and background simulation is shown.
png pdf	Figure 3: Left: the dimuon mass distribution with the pre-fit expected background event yield and its uncertainty, and the expected signal for $m_{\mathrm{A} }= $ 30 GeV assuming a signal cross section times branching fraction of 350 fb. Right: cross-check with the $\mathrm{ e }^{+} \mathrm{ e }^{-} $ final state showing the dielectron mass spectrum with the expected background event yield and its uncertainty.
png pdf	Figure 3-a: The dimuon mass distribution with the pre-fit expected background event yield and its uncertainty, and the expected signal for $m_{\mathrm{A} }= $ 30 GeV assuming a signal cross section times branching fraction of 350 fb.
png pdf	Figure 3-b: Cross-check with the $\mathrm{ e }^{+} \mathrm{ e }^{-} $ final state showing the dielectron mass spectrum with the expected background event yield and its uncertainty.
png pdf	Figure 4: The dimuon mass distribution for events selected by both the main (PF) and alternative (JPT) jet reconstruction methods as well as events selected by only the JPT algorithm.
png pdf	Figure 5: Left: the dimuon mass distribution with the post-fit background event yield and its uncertainty given by the fit, and the expected signal for $m_{\mathrm{A} }= $ 30 GeV assuming a signal cross section times branching fraction of 350 fb. Right: expected and observed upper limit at 95% CL on $\sigma (\mathrm{ p } \mathrm{ p } \to {\mathrm{ b \bar{b} } } \mathrm{A}) \mathcal {B} \mathrm{A} \to \mu \mu)$ as a function of $m_{\mathrm{A} }$. The open circles show the limits obtained in the CMS analysis of the $\mathrm{A} \to \tau \tau $ final state [8] when translated into limits for the $\mathrm{A} \to \mu \mu $ final state using Eq.(1).
png pdf	Figure 5-a: The dimuon mass distribution with the post-fit background event yield and its uncertainty given by the fit, and the expected signal for $m_{\mathrm{A} }= $ 30 GeV assuming a signal cross section times branching fraction of 350 fb.
png pdf	Figure 5-b: Expected and observed upper limit at 95% CL on $\sigma (\mathrm{ p } \mathrm{ p } \to {\mathrm{ b \bar{b} } } \mathrm{A}) \mathcal {B} \mathrm{A} \to \mu \mu)$ as a function of $m_{\mathrm{A} }$. The open circles show the limits obtained in the CMS analysis of the $\mathrm{A} \to \tau \tau $ final state [8] when translated into limits for the $\mathrm{A} \to \mu \mu $ final state using Eq.(1).

Summary

A light pseudoscalar Higgs boson, produced in association with a pair of b jets and decaying into two muons, has been searched for in pp collisions at $ \sqrt{s} = $ 8 TeV with an integrated luminosity of 19.7 fb$^{-1}$. This is the first time associated production with b quarks in the dimuon decay channel has been looked for in the low dimuon mass range. No signal has been observed in the dimuon mass range from 25 to 60 GeV. Upper limits on the cross section times branching fraction, $\sigma(\mathrm{ p }\mathrm{ p } \to \mathrm{ b \bar{b} }\mathrm{A})\, \mathcal{B}(\mathrm{A}\to\mu\mu)$, have been set. Despite the significantly lower branching fraction, the limits evaluated from the direct search for the $\mathrm{A}\to\mu\mu$ decay in $\mathrm{ b \bar{b} }\mathrm{A}$ associated production are comparable with those from the $\mathrm{A}\to\tau\tau$ search using the same production process.

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