Search for $H^0 \rightarrow b \bar{b}$ or $c \bar{c}$ in association with a $W$ or $Z$ boson in the forward region of $pp$ collisions
[to restricted-access page]Abstract
The LHCb dataset consisting of proton--proton collisions recorded at $\sqrt{s}=8$ $\mathrm{TeV}$, corresponding to an integrated luminosity of 1.98 $\pm$ 0.02 $fb^{-1}$, is used to search for a Higgs boson with a mass of 125 $\mathrm{GeV}$, produced in association with a $W$ or $Z$ boson and decaying to a $b \bar{b}$ or $c \bar{c}$ pair. The final state considered is a pair of heavy flavour tagged jets and one or two high $p_T$ leptons (electrons or muons). No excess over the background expectation is found and upper limits on the product of cross section times branching fraction, with two heavy quarks from $H^0$ and one lepton from $W$/$Z$ in the LHCb acceptance $2 < \eta < 5$, are set at 95% CL: \sigma(pp $\rightarrow$ W/Z + H^0 ) \times \mathrm{ $\cal B$ }(H^0 $\rightarrow$ b \bar{b}) < 1.6 \mathrm{pb}, \sigma(pp $\rightarrow$ W/Z + H^0 ) \times \mathrm{ $\cal B$ }(H^0 $\rightarrow$ c \bar{c}) < 9.4 \mathrm{pb}.
Figures and captions
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SV-tagger algorithm $\mathrm{BDT}_{b|c}$ for the highest jet $p_{\rm T}$ versus $\mathrm{BDT}_{b|c}$ for second highest jet $p_{\rm T}$ distributions. Distributions are obtained from $ W / Z + H ^0 ( b \overline b )$ (blue) and $ W / Z + H ^0 ( c \overline c )$ (red) simulation. The areas of the rectangles are proportional to the number of entries which is equal to the SM expectation after the selection cuts. |
bb_vs_cc.pdf [19 KiB] HiDef png [154 KiB] Thumbnail [167 KiB] *.C file |
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a) Dijet mass, b) uGB ( $ W$ / $ Z$ + $ H ^0$ vs $W+b\bar{b}$) and c) uGB ( $ W$ / $ Z$ + $ H ^0$ vs $t\bar{t}$) distributions of selected data events with dijet mass greater than 70 $\mathrm{ Ge V} $ for the muon sample used in the $ H ^0 \rightarrow b \bar{b}$ limit. The SM signal and background prediction is also shown. The $ H ^0 \rightarrow b \bar{b}$ yield (in magenta) is multiplied by a factor 50. The other background components include $Z+ b \overline b $, $Z+ c \overline c $, $ZZ$, $WZ$, $Z$ and $W$+jets and several QCD processes. The compatibility between the observed data and the expected theory yield is below 2 Gaussian standard deviations. |
higgs_[..].pdf [19 KiB] HiDef png [262 KiB] Thumbnail [242 KiB] *.C file |
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a) Dijet mass, b) uGB ( $ W$ / $ Z$ + $ H ^0$ vs $W+b\bar{b}$) and c) uGB ( $ W$ / $ Z$ + $ H ^0$ vs $t\bar{t}$) distributions of selected data events with dijet mass greater than 70 $\mathrm{ Ge V} $ for the electron sample used in the $ H ^0 \rightarrow b \bar{b}$ limit. The SM signal and background prediction is also shown. The $ H ^0 \rightarrow b \bar{b}$ yield (in magenta) is multiplied by a factor 50. The other background components include $Z+ b \overline b $, $Z+ c \overline c $, $ZZ$, $WZ$, $Z$ and $W$+jets and several QCD processes. The data is compatible with the background expectation. |
higgs_bb_e.pdf [19 KiB] HiDef png [258 KiB] Thumbnail [242 KiB] *.C file |
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SM prediction of a) Dijet mass, b) uGB ( $ W$ / $ Z$ + $ H ^0$ vs $W+b\bar{b}$) and c) uGB ( $ W$ / $ Z$ + $ H ^0$ vs $t\bar{t}$) distributions of events with dijet mass greater than 70 $\mathrm{ Ge V} $ for the muon sample used in the $ H ^0 \rightarrow c \bar{c}$ limit. The $ H ^0 \rightarrow c \bar{c}$ yield (in magenta) is multiplied by a factor of 1000. The other background components include $ W + b \overline b $ , $ t \overline t $ , $Z+ b \overline b $, $Z+ c \overline c $, $ZZ$, $WZ$, $Z$ and $W$+jets and several QCD processes. There are no data events passing the selection criteria for this sample. |
higgs_[..].pdf [17 KiB] HiDef png [247 KiB] Thumbnail [230 KiB] *.C file |
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SM prediction of a) Dijet mass, b) uGB ( $ W$ / $ Z$ + $ H ^0$ vs $W+b\bar{b}$) and c) uGB ( $ W$ / $ Z$ + $ H ^0$ vs $t\bar{t}$) distributions of events with dijet mass greater than 70 $\mathrm{ Ge V} $ for the electron sample used in the $ H ^0 \rightarrow c \bar{c}$ limit. The $ H ^0 \rightarrow c \bar{c}$ yield (in magenta) is multiplied by a factor of 1000. The other background components include $ W + b \overline b $ , $ t \overline t $ , $Z+ b \overline b $, $Z+ c \overline c $, $ZZ$, $WZ$, $Z$ and $W$+jets and several QCD processes. There are no data events passing the selection criteria for this sample. |
higgs_cc_e.pdf [17 KiB] HiDef png [247 KiB] Thumbnail [229 KiB] *.C file |
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Distributions of $ W / Z + H ^0 ( b \overline b )$ , $Wb\bar{b}$ and $t \bar{t}$ simulated events in the transformed uGB space. |
higgs_[..].pdf [17 KiB] HiDef png [223 KiB] Thumbnail [202 KiB] *.C file |
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Observed and expected $CL_s$ and $95\%$ CL upper limit for the $ H ^0 \rightarrow b \bar{b}$. The 0.05 $CL_s$ level is indicated by the red horizontal line. |
limit_bb.pdf [16 KiB] HiDef png [167 KiB] Thumbnail [137 KiB] *.C file |
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Observed and expected $CL_s$ and $95\%$ CL upper limit for the $ H ^0 \rightarrow c \bar{c}$. The 0.05 $CL_s$ level is indicated by the red horizontal line. |
limit_cc.pdf [16 KiB] HiDef png [168 KiB] Thumbnail [130 KiB] *.C file |
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Animated gif made out of all figures. |
CONF-2016-006.gif Thumbnail |
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![HiDef png [154 KiB]](Directory_LHCb-CONF-2016-006/hidef_bb_vs_cc.png){kind=link}
![HiDef png [262 KiB]](Directory_LHCb-CONF-2016-006/hidef_higgs_bb_mu.png){kind=link}
![HiDef png [258 KiB]](Directory_LHCb-CONF-2016-006/hidef_higgs_bb_e.png){kind=link}
![HiDef png [247 KiB]](Directory_LHCb-CONF-2016-006/hidef_higgs_cc_mu.png){kind=link}
![HiDef png [247 KiB]](Directory_LHCb-CONF-2016-006/hidef_higgs_cc_e.png){kind=link}
![HiDef png [223 KiB]](Directory_LHCb-CONF-2016-006/hidef_higgs_bb_mu_uGBs.png){kind=link}
![HiDef png [167 KiB]](Directory_LHCb-CONF-2016-006/hidef_limit_bb.png){kind=link}
![HiDef png [168 KiB]](Directory_LHCb-CONF-2016-006/hidef_limit_cc.png){kind=link}
Tables and captions
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Bin--per--bin weighted average variation of the histograms used in the $ H ^0 \rightarrow b \bar{b}$ limit computation for the main uncertainty sources and for signal and background in the muon and electron samples. |
Table_1.pdf [36 KiB] HiDef png [59 KiB] Thumbnail [29 KiB] tex code |
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![HiDef png [59 KiB]](Directory_LHCb-CONF-2016-006/hidef_Table_1.png){kind=link}
Created on 27 April 2024.