Search for the standard-model Higgs boson decaying to $\tau\tau$ in non VH channels

This is a condensed description with plots for the analysis CMS-HIG-13-004

Table of contents: Abstract Nota Bene Main Results Tables Figures from CMS-HIG-13-004 Mass/Final Discriminator Distributions at 8 TeV Results Additional Material Event Display Additional Mass Distributions Mass Distributions at 8 TeV Mass Distributions at 7 TeV

Abstract

A search for the standard model Higgs boson decaying into a pair of $\tau$ leptons is performed using events recorded by the CMS experiment at the LHC in 2011 and 2012. The dataset corresponds to an integrated luminosity of 4.9 $fb^{-1}$ at a centre-of-mass energy of 7 TeV and 19.7 $fb^{-1}$ at 8 TeV. Each $\tau$ lepton can decay hadronically or leptonically to an electron or a muon, leading to six different final states for the $\tau$ pair, all considered in the analysis. An excess of events is observed over the expected background contributions, with a local significance larger than 3 standard deviations for $m_H$ values between 110 and 130 GeV. The best-fit signal strength relative to the $\sigma * BR(H\rightarrow\tau\tau)$ for the production and decay of a standard model Higgs boson of mass $m_H$=125 GeV is $\hat\mu$ = 0.87 ± 0.29, indicating good compatibility between this excess and the rate expected for the standard model Higgs boson.

Nota Bene

Main Results

Tables

Table 1: Combined observed 95% CL upper limit on the signal strength parameter $\mu = \sigma/\sigma_{SM}$, together with the expected limit obtained in the background hypothesis and the one- and two standard- deviation probability intervals around the expected limit. This result corresponds to Fig. 25a and includes the search for a SM Higgs boson decaying into $\tau\tau$.

Table 2: Main systematic uncertainties entering the analysis.

Table 3: Observed and expected event yields in the $\mu\tau$ channel.

Table 4: Observed and expected event yields in the $e\tau$ channel.

Table 5: Observed and expected event yields in the $\tau\tau$ channel.

Table 6: Observed and expected event yields in the $e\mu$ channel.

Table 7: Observed and expected event yields in the $\mu\mu$ channel.

Table 8: Observed and expected event yields in the $ee$ channel.

Table 9: Significance and p-value

Figures from CMS-HIG-13-004

	png pdf	Figure 1: Observed and predicted distributions in the 2012 analysis for the visible $\tau$ mass, in the $\mu\tau$ channel after the baseline selection. The normalization of the predicted distributions corresponds to the final result of the analysis. The simulated contribution from the production of a Z boson decaying into a pair of $\tau$ leptons ($Z\rightarrow\tau\tau$) is split according to the decay mode reconstructed by the hadron-plus-strips algorithm. One can distinguish the $\tau$ built from one charged hadron and photons that are reconstructed with the mass of the intermediate rho resonance and the ones built from three charged hadrons that are reconstructed with the mass of the intermediate $a_1$(1260) resonance. The $\tau$ built from one charged hadron and no photons are reconstructed with the charged pion mass, assigned to all charged hadrons by the PF algorithm, and constitute the main contribution to the third bin of this histogram. The first two bins correspond to $\tau$ leptons decaying into $e \nu_e \nu_{\tau}$ and $\mu \nu_{\mu} \nu_{\tau}$, respectively, and for which the electron or muon is misidentified as a $\tau$. The electroweak background contribution is dominated by $W$+jets production. In most selected $W$+jets, $t\bar t$ and QCD multijet events, a jet is misidentified as a $\tau$. The background uncertainty band represents the combined statistical and systematic uncertainty in the background yield in each bin. Given the inclusive nature of the selection used, the expected contribution from the SM Higgs signal is negligible.
	png pdf	Figure 2: Observed and predicted distributions in the 2012 analysis for the transverse momentum of the $\tau$ in the $\mu\tau$ channel after the baseline selection . The normalization of the predicted distributions corresponds to the final result of the analysis. The electroweak background contribution includes events from $W$+jets, diboson, and single-top production. The background uncertainty band represents the combined statistical and systematic uncertainty in the background yield in each bin. Given the inclusive nature of the selection used, the expected contribution from the SM Higgs signal is negligible.
	png pdf	Figure 3: Observed and predicted distributions in the 2012 analysis for the transverse momentum of the Higgs boson candidate in the mu-tau channel. The transverse momentum of the Higgs boson candidate is defined as the scalar magnitude of the vector sum of the di-tau pair transverse momentum and the MET. The normalization of the predicted distributions corresponds to the final result of the analysis. The background uncertainty band represents the combined statistical and systematic uncertainty in the background yield in each bin. Given the inclusive nature of the selection used, the expected contribution from the SM Higgs signal is negligible.
	png pdf	Figure 4: Observed and predicted distributions in the 2012 analysis for the transverse mass in the mu-tau channel. The baseline cut used to suppress $W$+jets background requires transverse mass less than 30 GeV, whereas the sideband defined by transverse mass larger than 70 GeV is used to normalize the $W$+jets background, separately in each category of each channel.
	png pdf	Figure 5: Observed and predicted distributions in the 2012 analysis for the number of jets in the $e\mu$ channel. The normalization of the predicted distributions corresponds to the final result of the analysis. The background uncertainty band represents the combined statistical and systematic uncertainty in the background yield in each bin. Given the inclusive nature of the selection used, the expected contribution from the SM Higgs signal is negligible.
	png pdf	Figure 6: Categories definition for the 8 TeV, 2012, analysis of the six channels. The $p_T^{\tau\tau}$ variable is the transverse momentum of the Higgs boson candidate. In the definition of the VBF-tag categories, $\Delta\eta_{jj}$ is the difference in pseudorapidity between the two highest-$p_T$ jets, and $m_{jj}$ their invariant mass. In the $ee$ and $\mu\mu$ channels, events with two jets are not required to fulfill any additional VBF tagging criteria. For the analysis of the 2011 $e\tau$ and $\mu\tau$ data, the loose and tight VBF-tag categories are merged into a single VBF-tag category. In the $e\tau$ channel, the MET is required to be larger than 30 GeV in the 1-jet category, and the high-$p_T$ category is not used. Categories are mutually exclusive.
	png pdf	Figure 7a: Normalized distribution of the visible invariant mass mvis obtained from MC simulation in the $\mu\tau$ channel for the $Z\rightarrow\tau\tau$ background (solid histogram) and a SM Higgs boson signal of mass $m_H$ = 125 GeV (open histogram).
	png pdf	Figure 7b: Normalized distribution of the SVFit mass $m_{\tau\tau}$ obtained from MC simulation in the $\mu\tau$ channel for the $Z\rightarrow\tau\tau$ background (solid histogram) and a SM Higgs boson signal of mass $m_H$ = 125 GeV (open histogram).

Mass/Final Discriminator Distributions at 8 TeV

	png pdf	Figure 8: Expected and observed final discriminator D distributions in the $ee$ channel, and in the 1 jet, high $p_T^{e}$ category.
	png pdf	Figure 9: Expected and observed final discriminator D distributions in the $ee$ channel, and the 2 jets category.
	png pdf	Figure 10: Expected and observed final discriminator D distributions in the $\mu\mu$ channel, and in the 1 jet, high $p_T^{\mu}$ category.
	png pdf	Figure 11: Expected and observed final discriminator D distributions in the $\mu\mu$ channel, and in the 2 jets category.
	png pdf	Figure 12: Expected and observed SFVfit mass distributions in the $e\mu$ channel, and in the 1 jet, high $p_T^{\tau}$ category.
	png pdf	Figure 13: Expected and observed SFVfit mass distributions in the $e\mu$ channel, and in the loose VBF category.
	png pdf	Figure 14: Expected and observed SFVfit mass distributions in the $e\mu$ channel, and in the tight VBF category.
	png pdf	Figure 15: Expected and observed SFVfit mass distributions in the $\tau\tau$ channel, and in the 1 jet, medium $p_T^{\tau\tau}$ category.
	png pdf	Figure 16: Expected and observed SFVfit mass distributions in the $\tau\tau$ channel, and in the 1 jet, high $p_T^{\tau\tau}$ category.
	png pdf	Figure 17: Expected and observed SFVfit mass distributions in the $\tau\tau$ channel, and in the VBF category.
	png pdf	Figure 18: Expected and observed SFVfit mass distributions in the $e\tau$ channel, and in the 1 jet, high $p_T^{\tau}$, medium $p_T^{\tau\tau}$ category.
	png pdf	Figure 19: Expected and observed SFVfit mass distributions in the $e\tau$ channel, and in the loose VBF category.
	png pdf	Figure 20: Expected and observed SFVfit mass distributions in the $e\tau$ channel, and in the tight VBF category.
	png pdf	Figure 21: Expected and observed SFVfit mass distributions in the mu-tau channel, and in the 1 jet, high $p_T^{\tau}$, medium $p_T^{\tau\tau}$ category.
	png pdf	Figure 22: Expected and observed SFVfit mass distributions in the $\mu\tau$ channel, and in the loose VBF category.
	png pdf	Figure 23: Expected and observed SFVfit mass distributions in the $\mu\tau$ channel, and in the tight VBF category.

Results

	png pdf	Figure 24: Combined observed and predicted di-tau mass distributions for the $\mu\tau$, $e\tau$, $e\mu$ and $\tau\tau$ channels. The normalization of the predicted background distributions corresponds to the result of the global fit. The signal distribution, on the other hand, is normalized to the standard model prediction ($\mu = 1$). The distributions obtained in each category of each channel are weighted by the ratio between the expected signal and signal-plus-background yields in the category. The inset shows the corresponding difference between the observed data and ex- pected background distributions, together with the signal distribution for a SM Higgs boson at $m_H$ = 125 GeV, focussing on the signal region.
	png pdf	Figure 25a: Combined observed 95% CL upper limit on the signal strength parameter $\mu = \sigma/\sigma_{SM}$, together with the expected limit obtained in the background hypothesis. The bands show the expected one- and two-standard-deviation probability intervals around the expected limit.
	png pdf	Figure 25b: Combined observed 95% CL upper limit on the signal strength parameter $\mu = \sigma/\sigma_{SM}$, together with the expected limit obtained in the signal-plus-background hypothesis for a SM Higgs boson with $m_H$ = 125 GeV. The bands show the expected one- and two-standard-deviation probability intervals around the expected limit.
	png pdf	Figure 26: Observed and expected local p-value, and observed significance in number of standard deviations. Dashed blue line represents the expeted p-value for any given $m_H$ hypothesis.
	png pdf	Figure 27a: Best-fit signal strength values, for independent channels, with $m_H$ = 125 GeV. The combined value for the $H\rightarrow\tau\tau$ analysis in both plots corresponds to $\mu$ = 0.87 ± 0.29, obtained in the global fit combining all categories of all channels.
	png pdf	Figure 27b: Best-fit signal strength values, for independent categories, with $m_H$ = 125 GeV. The combined value for the $H\rightarrow\tau\tau$ analysis in both plots corresponds to $\mu$ = 0.87 ± 0.29, obtained in the global fit combining all categories of all channels.
	png pdf	Figure 28a: Likelihood scans as a function of $\mu$ and $m_H$. For each point, all nuisance parameters are profiled.
	png pdf	Figure 30: Likelihood scans as a function of $k_V$ and $k_f$. For each point, all nuisance parameters are profiled. $H\rightarrow WW$ contribution is considered as part of the signal

Table 10: Each row in the table reports the ($k_V$, $k_f$) coordinates of each point, for which the likelihood scan is performed, defining the 68% and 95% CL contours, as shown in Fig. 30. Signal is assumed to be at $m_H$ = 125 GeV and $H\rightarrow WW$ contribution is considered as part of the signal.

Additional Material

	png pdf	Figure 32a: Expected 95% CL upper limit on the signal strength parameter $\mu = \sigma/\sigma_{SM}$ in the background only hypothesis, shown separately for the six channels.
	png pdf	Figure 32b: Expected 95% CL upper limit on the signal strength parameter $\mu = \sigma/\sigma_{SM}$ in the background only hypothesis, shown separately for 0-Jet, 1-Jet, VBF categories.
	png pdf	Figure 34a: Distribution of $\log(S/(S+B))$, with the signal yield $S$ and background yield $B$ taken from each bin in each event category. All the channels except for the VH final state is combined. The first bin also includes the underflow. The normalization of the predicted background distributions corresponds to the result of the global fit. The signal distribution, on the other hand, is normalized to the standard model prediction ($\mu = 1$). The inset shows the corresponding difference between the observed data and expected background distributions, together with the expected signal distribution for a standard-model Higgs signal at $m_H$ = 125 GeV.
	png pdf	Figure 34b: Distribution of $\log(S/(S+B))$, with the signal yield $S$ and background yield $B$ taken from each bin in each event category. All the channels are combined. The first bin also includes the underflow. The normalization of the predicted background distributions corresponds to the result of the global fit. The signal distribution, on the other hand, is normalized to the standard model prediction ($\mu = 1$). The contributions from the six different channels are shown in different colors. The inset shows the corresponding difference between the observed data and expected background distributions, together with the expected signal distribution for a standard-model Higgs signal at $m_H$ = 125 GeV.
	png pdf	Figure 34c: Distribution of $\log(S/(S+B))$, with the signal yield $S$ and background yield $B$ taken from each bin in each event category. All the channels are combined. The first bin also includes the underflow. The normalization of the predicted background distributions corresponds to the result of the global fit. The signal distribution, on the other hand, is normalized to the standard model prediction ($\mu = 1$). The contributions from the three different categories, 0-Jet, 1-Jet and VBF are shown in different colors. The inset shows the corresponding difference between the observed data and expected background distributions, together with the expected signal distribution for a standard-model Higgs signal at $m_H$ = 125 GeV.
	png pdf	Figure 31: Combined observed 95% CL upper limit on the signal strength parameter $\mu = \sigma/\sigma_{SM}$, together with the expected limit obtained in the background only hypothesis, where the SM Higgs boson with $m_H$ = 125 GeV is included as part of the background. The bands show the expected one- and two-standard-deviation probability intervals around the expected limit.
	png pdf	Figure 29: Best-fit signal strength values, for independent categories from different channels, with $m_H$ = 125 GeV. The combined value for the $H\rightarrow\tau\tau$ analysis in both plots corresponds to $\mu$ = 0.87 ± 0.29, obtained in the global fit combining all categories of all channels. This plot assesses the compatibility of $\mu$ values as measured in different channels/categories. All categories in all channels are simultaneously fit so that inter-category correlations for background constraints are preserved. The signal strength is measured separately in each category of each channel.
	png pdf	Figure 28b: Likelihood scans as a function of $m_H$. For each point, all nuisance parameters are profiled.

Event Display

png (black background)

Figure 35: 3D view of a candidate HTauTau VBF event in the $\mu\tau$ channel, recorded by CMS during 2012. The muon, represented by the red line on the left with hits visible in the endcap muon chambers, has a $p_T$ of 23.4 GeV. The hadronically-decaying $\tau$ candidate, indicated by the two large blue towers in the center of this figure, has a $p_T$ of 39.3 GeV. The di-tau mass, calculated using the svfit algorithm, is 102.0 GeV. The two jets passing the VBF selection, indicated by the large green towers in the two opposite-side endcaps, have $p_T$ 77.6 and 75.4 GeV, are separated in eta by 5.8 and have a mass of 1.4 TeV. There are no additional jets in the eta range between these tagging jets with a $p_T$ above 30 GeV.

Additional Mass Distributions

Mass Distributions at 8 TeV

	png pdf	Figure 36: Expected and observed final discriminator D distributions in the $ee$ channel, and in the 0 jet, low $p_T^{e}$ category.
	png pdf	Figure 37: Expected and observed final discriminator D distributions in the $ee$ channel, and in the 0 jet, high $p_T^{e}$ category.
	png pdf	Figure 38: Expected and observed final discriminator D distributions in the $ee$ channel, and in the 1 jet, low $p_T^{e}$ category.
	png pdf	Figure 39: Expected and observed final discriminator D distributions in the $\mu\mu$ channel, and in the 0 jet, low $p_T^{\mu}$ category.
	png pdf	Figure 30: Expected and observed final discriminator D distributions in the $\mu\mu$ channel, and in the 0 jet, high $p_T^{\mu}$ category.
	png pdf	Figure 41: Expected and observed final discriminator D distributions in the $\mu\mu$ channel, and in the 1 jet, low $p_T^{\mu}$ category.
	png pdf	Figure 42: Expected and observed SFVfit mass distributions in the $e\mu$ channel, and in the 0 jet, medium $p_T^{\mu}$ category.
	png pdf	Figure 43: Expected and observed SFVfit mass distributions in the $e\mu$ channel, and in the 0 jet, high $p_T^{\mu}$ category.
	png pdf	Figure 44: Expected and observed SFVfit mass distributions in the $e\mu$ channel, and in the 1 jet, medium $p_T^{\mu}$ category.
	png pdf	Figure 45: Expected and observed SFVfit mass distributions in the $e\tau$ channel, and in the 0 jet, medium $p_T^{\tau}$ category.
	png pdf	Figure 46: Expected and observed SFVfit mass distributions in the $e\tau$ channel, and in the 0 jet, high $p_T^{\tau}$ category.
	png pdf	Figure 47: Expected and observed SFVfit mass distributions in the $e\tau$ channel, and in the 1 jet, medium $p_T^{\tau}$ category.
	png pdf	Figure 48: Expected and observed SFVfit mass distributions in the $\mu\tau$ channel, and in the 0 jet, medium $p_T^{\tau}$ category.
	png pdf	Figure 49: Expected and observed SFVfit mass distributions in the $\mu\tau$ channel, and in the 0 jet, high $p_T^{\tau}$ category.
	png pdf	Figure 50: Expected and observed SFVfit mass distributions in the $\mu\tau$ channel, and in the 1 jet, medium $p_T^{\tau}$ category.
	png pdf	Figure 51: Expected and observed SFVfit mass distributions in the $\mu\tau$ channel, and in the 1 jet, high $p_T^{\tau}$, low $p_T^{\tau\tau}$ category.

Mass Distributions at 7 TeV

	png pdf	Figure 52: Expected and observed final discriminator D distributions in the $ee$ channel, and in the 0 jet, low $p_T^{e}$ category.
	png pdf	Figure 53: Expected and observed final discriminator D distributions in the $ee$ channel, and in the 0 jet, high $p_T^{e}$ category.
	png pdf	Figure 54: Expected and observed final discriminator D distributions in the $ee$ channel, and in the 1 jet, low $p_T^{e}$ category.
	png pdf	Figure 55: Expected and observed final discriminator D distributions in the $ee$ channel, and in the 1 jet, high $p_T^{e}$ category.
	png pdf	Figure 56: Expected and observed final discriminator D distributions in the $ee$ channel, and in the 2 jets category.
	png pdf	Figure 57: Expected and observed final discriminator D distributions in the $\mu\mu$ channel, and in the 0 jet, low $p_T^{\mu}$ category.
	png pdf	Figure 58: Expected and observed final discriminator D distributions in the $\mu\mu$ channel, and in the 0 jet, high $p_T^{\mu}$ category.
	png pdf	Figure 59: Expected and observed final discriminator D distributions in the $\mu\mu$ channel, and in the 1 jet, low $p_T^{\mu}$ category.
	png pdf	Figure 60: Expected and observed final discriminator D distributions in the $\mu\mu$ channel, and in the 1 jet, high $p_T^{\mu}$ category.
	png pdf	Figure 61: Expected and observed final discriminator D distributions in the $\mu\mu$ channel, and in the 2 jets category.
	png pdf	Figure 62: Expected and observed SFVfit mass distributions in the $e\mu$ channel, and in the 0 jet, low $p_T^{\mu}$ category.
	png pdf	Figure 63: Expected and observed SFVfit mass distributions in the $e\mu$ channel, and in the 0 jet, high $p_T^{\mu}$ category.
	png pdf	Figure 64: Expected and observed SFVfit mass distributions in the $e\mu$ channel, and in the 1 jet, low $p_T^{\mu}$ category.
	png pdf	Figure 65: Expected and observed SFVfit mass distributions in the $e\mu$ channel, and in the 1 jet, high $p_T^{\mu}$ category.
	png pdf	Figure 66: Expected and observed SFVfit mass distributions in the $e\mu$ channel, and in the VBF category.
	png pdf	Figure 67: Expected and observed SFVfit mass distributions in the $e\tau$ channel, and in the 0 jet, medium $p_T^{\tau}$ category.
	png pdf	Figure 68: Expected and observed SFVfit mass distributions in the $e\tau$ channel, and in the 0 jet, high $p_T^{\tau}$ category.
	png pdf	Figure 69: Expected and observed SFVfit mass distributions in the $e\tau$ channel, and in the 1 jet, medium $p_T^{\tau}$ category.
	png pdf	Figure 70: Expected and observed SFVfit mass distributions in the $e\tau$ channel, and in the 1 jet, high $p_T^{\tau}$, medium $p_T^{\tau\tau}$ category.
	png pdf	Figure 71: Expected and observed SFVfit mass distributions in the $e\tau$ channel, and in the VBF category
	png pdf	Figure 72: Expected and observed SFVfit mass distributions in the $\mu\tau$ channel, and in the 0 jet, medium $p_T^{\tau}$ category.
	png pdf	Figure 73: Expected and observed SFVfit mass distributions in the $\mu\tau$ channel, and in the 0 jet, high $p_T^{\tau}$ category.
	png pdf	Figure 74: Expected and observed SFVfit mass distributions in the $\mu\tau$ channel, and in the 1 jet, medium $p_T^{\tau}$ category.
	png pdf	Figure 75: Expected and observed SFVfit mass distributions in the $\mu\tau$ channel, and in the 1 jet, high $p_T^{\tau}$, low $p_T^{\tau\tau}$ category.
	png pdf	Figure 76: Expected and observed SFVfit mass distributions in the $\mu\tau$ channel, and in the 1 jet, high $p_T^{\tau}$, medium $p_T^{\tau\tau}$ category.
	png pdf	Figure 77: Expected and observed SFVfit mass distributions in the $\mu\tau$ channel, and in the VBF category