Simulation of a Cross Section and Mass Measurement of a SM Higgs Boson in the H->WW->lvlv Channel at the LHC

TL;DR

The paper evaluates how accurately the SM Higgs mass and cross section can be extracted from gg→H→WW→ℓνℓν in the 150–180 GeV range. It combines a fixed, mass-independent event selection with NNLO-reweighted Higgs pT information and leverages lepton pT spectra, especially the ΔpT observable, which are robust to Higgs pT modeling. The authors show that with about 10 fb−1, the Higgs mass can be measured to roughly 2–2.5 GeV, though rate-only information can yield a twofold mass ambiguity that is resolved by lepton pT shape analyses. The proposed combined approach thus enables a precise, cross-validated MH determination in this channel, while highlighting systematic uncertainties that become limiting as data accumulate.

Abstract

The potential to discover a Standard-Model-like Higgs boson at the LHC in the mass range from 150-180 GeV, decaying into a pair of W bosons with subsequent leptonic decays, has been established during the last 10 years. Assuming that such a signal will eventually be observed, the analysis described in this paper investigates how accurate the signal cross section can be measured and how the observable lepton pt spectra can be used to constrain the mass of the Higgs boson. Combining the signal cross section with the analysis of the lepton pt spectra and assuming the SM Higgs cross section is known with an accuracy of +-5%, our study indicates that an integrated luminosity of about 10 fb-1 allows to measure the mass of a SM Higgs boson with an accuracy between 2 and 2.5 GeV.

Figures (11)

• Figure 1: Cross section of the Higgs signal ($\rm{M_H}$ = 165 GeV) as well as the main backgrounds, that is qqWW, ggWW, $\rm{ t\bar{t}}$ and Wtb, as a function of the ^ℓ_T max $p^\ell_\mathrm{T max}$ (left) and ^ℓ_T min $p^\ell_\mathrm{T min}$ (right). All cuts are applied except the ones on the _T $p_\mathrm{T}$ of the leptons. The events are generated with PYTHIA and TOPREX Slabospitsky:2002ag and reweighted to NNLO and NLO respectively. WW production via gluon fusion was generated using a Monte Carlo provided by N. Kauer Binoth:2005ua, with parton shower simulation in PYTHIA.
• Figure 2: Cross section of the Higgs signal ($\rm{M_{H}}$ = 165 GeV) and the sum of the main backgrounds, that is qqWW, ggWW, $\rm{ t\bar{t}}$ and Wtb, and the background alone, as a function of the _T $p_\mathrm{T}$ of the lepton with the maximal _T $p_\mathrm{T}$ (left) and the minimal _T $p_\mathrm{T}$ (right). All cuts are applied except the ones on the _T $p_\mathrm{T}$ of the leptons. The events are generated with PYTHIA and TOPREX and reweighted to NNLO and NLO respectively. WW production via gluon fusion was generated using a Monte Carlo provided by N. Kauer Binoth:2005ua, with parton shower simulation in PYTHIA.
• Figure 3: Cross section of $\rm{gg} \rightarrow H \rightarrow \rm{WW} \rightarrow \ell\nu \ell \nu$ process for a Higgs mass of 155, 165 and 175 GeV as a function of the lepton _T $p_\mathrm{T}$ of ^ℓ_T max $p^\ell_\mathrm{T max}$ (left) and ^ℓ_T min $p^\ell_\mathrm{T min}$ (right). Only the lepton isolation cut and the minimal _T $p_\mathrm{T}$ of 10 GeV are applied.
• Figure 4: Cross section of the Higgs signal decaying into $\rm{WW \rightarrow \ell\nu \ell \nu}$ for a Higgs mass of 155, 165 and 175 GeV as a function of ^ℓ_T max $p^\ell_\mathrm{T max}$ (left) and ^ℓ_T min $p^\ell_\mathrm{T min}$ (right). All cuts, except the final ones on the _T $p_\mathrm{T}$ of the leptons, are applied.
• Figure 5: Number of SM Higgs events events for 10 fb$^{-1}$ with all cuts applied and approximated with a fit of two Gaussian distributions for Higgs masses between 150-180 GeV and assuming a theoretical cross section uncertainty of $\pm$ 5%. Three hypothetical experimental numbers of signal events, including statistical and systematic error, are also shown. For the case of a hypothetical result corresponding to a Higgs mass of 155 GeV, the possible graphical interpretation in terms of the SM Higgs mass is also indicated.