Measurement of the transverse momentum spectrum of the Higgs boson produced in pp collisions at sqrt(s) = 8 TeV using H to WW decays

TL;DR

This CMS study measures the Higgs boson transverse momentum spectrum in pp collisions at √s = 8 TeV via the H→WW→e±μ∓νν channel. A fiducial phase space is defined to match the detector acceptance, and an unfolding procedure corrects for detector effects to compare with SM predictions from NNLO+NNLL calculations. A two-dimensional template fit in m_ll and m_T in six pT^H bins extracts the signal, with robust data-driven background estimates and a careful treatment of systematic and model-dependence uncertainties. The inclusive fiducial cross section is found to be 39 ± 8 (stat) ± 9 (syst) fb, in agreement with SM expectations, demonstrating precise Higgs kinematics measurements in dileptonic WW final states and validating theoretical predictions in the Higgs sector.

Abstract

The cross section for Higgs boson production in pp collisions is studied using the H to WW decay mode, followed by leptonic decays of the W bosons to an oppositely charged electron-muon pair in the final state. The measurements are performed using data collected by the CMS experiment at the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.4 inverse femtobarns. The Higgs boson transverse momentum (pT) is reconstructed using the lepton pair pT and missing pT. The differential cross section times branching fraction is measured as a function of the Higgs boson pT in a fiducial phase space defined to match the experimental acceptance in terms of the lepton kinematics and event topology. The production cross section times branching fraction in the fiducial phase space is measured to be 39 +/- 8 (stat) +/- 9 (syst) fb. The measurements are found to agree, within experimental uncertainties, with theoretical calculations based on the standard model.

Figures (6)

• Figure 1: Distributions of the $m_{\ell\ell}$ variable in each of the six $p_{\mathrm{T}}^{\mathrm{H}}$ bins. Background normalizations correspond to the values obtained from the fit. Signal normalization is fixed to the SM expectation. The distributions are shown in an $m_\mathrm{T}$ window of [60,110]$\,\text{Ge\spaceV}$ in order to emphasize the Higgs boson (H) signal. The signal contribution is shown both stacked on top of the background and superimposed on it. Ratios of the expected and observed event yields in individual bins are shown in the panels below the plots. The uncertainty band shown in the ratio plot corresponds to the envelope of systematic uncertainties after performing the fit to the data.
• Figure 2: Distributions of the $m_\mathrm{T}$ variable in each of the six $p_{\mathrm{T}}^{\mathrm{H}}$ bins. Background normalizations correspond to the values obtained from the fit. Signal normalization is fixed to the SM expectation. The distributions are shown in an $m_{\ell\ell}$ window of [12,75]$\,\text{Ge\spaceV}$ in order to emphasize the Higgs boson (H) signal. The signal contribution is shown both stacked on top of the background and superimposed on it. Ratios of the expected and observed event yields in individual bins are shown in the panels below the plots. The uncertainty band shown in the ratio plot corresponds to the envelope of systematic uncertainties after performing the fit to the data.
• Figure 3: Differential Higgs boson production cross section as a function of the reconstructed $p_{\mathrm{T}}^{\mathrm{H}}$, before applying the unfolding procedure. Data values after the background subtraction are shown together with the statistical and the systematic uncertainties, determined propagating the sources of uncertainty through the fit procedure. The line and dashed area represent the SM theoretical estimates in which the acceptance of the dominant ggH contribution is modelled by powheg V1. The sub-dominant component of the signal is denoted as XH=VBF+VH, and is shown with the cross filled area separately.
• Figure 4: Response matrix normalized by row (left) and by column (right) including all signal processes. The matrices are normalized either by row (left) or by column (right) in order to show the purity or stability respectively in diagonal bins.
• Figure 5: Higgs boson production cross section as a function of $p_{\mathrm{T}}^{\mathrm{H}}$, after applying the unfolding procedure. Data points are shown, together with statistical and systematic uncertainties. The vertical bars on the data points correspond to the sum in quadrature of the statistical and systematic uncertainties. The model dependence uncertainty is also shown. The pink (and back-slashed filling) and green (and slashed filling) lines and areas represent the SM theoretical estimates in which the acceptance of the dominant ggH contribution is modelled by HRes and powheg V2, respectively. The subdominant component of the signal is denoted as XH=VBF+VH and it is shown with the cross filled area separately. The bottom panel shows the ratio of data and powheg V2 theoretical estimate to the HRes theoretical prediction.