Bounding the Higgs width at the LHC using full analytic results for gg → e − e + μ − μ +

Abstract

Abstract:We revisit the hadronic production of the four-lepton final state, e − e + µ − µ + , through the fusion of initial state gluons. This process is mediated by loops of quarks and we provide first full analytic results for helicity amplitudes that account for both the effects of the quark mass in the loop and off-shell vector bosons. The analytic results have been implemented in the Monte Carlo program MCFM and are both fast, and numerically stable in the region of low Z transverse momentum. We use our results to study the interference between Higgs-mediated and continuum production of four-lepton final states, which is necessary in order to obtain accurate theoretical predictions outside the Higgs resonance region. We have confirmed and extended a recent analysis of Caola and Melnikov that proposes to use a measurement of the off-shell region to constrain the total width of the Higgs boson. Using a simple cut-and-count method, existing LHC data should bound the width at the level of 25-45 times the Standard Model expectation. We investigate the power of using a matrix element method to construct a kinematic discriminant to sharpen the constraint. In our analysis the bound on the Higgs width is improved by a factor of about 1.6 using a simple cut on the MEM discriminant, compared to an invariant mass cut m 4l > 300 GeV.

Limits on the Higgs boson lifetime and width from its decay to four charged leptons

“…The upper bound on Γ H is set using the off-shell production method [22][23][24] and follows the technique developed by CMS [10], where the gluon fusion and weak vector boson fusion (VBF) production mechanisms were considered in the analysis. The technique considers the H boson production relationship between the on-shell (105.6 < m 4l < 140.6 GeV) and off-shell (220 < m 4l < 1600 GeV) regions.…”

“…On-shell and off-shell events from gluon fusion production are generated with the MCFM 6.7 [24,41,42] and GG2VV 3.1.5 [43] MC generators while those for the VBF and associated production with an electroweak boson V are generated with PHANTOM 1.2.3 [44]. The leptonic decay of the associated V boson is modeled with a reweighting procedure based on the branching ratios of the V boson [45], and the relatively small contribution of HH production is removed from the PHANTOM simulation.…”

Probing the top-quark width through ratios of resonance contributions of e + e − → W + W − b b ¯ $$ {\mathrm{e}}^{+}{\mathrm{e}}^{-}\to {\mathrm{W}}^{+}{\mathrm{W}}^{-}\mathrm{b}\overline{\mathrm{b}} $$

“…those with two, one and no intermediate top-quark propagators) is included in the calculation. The method we present lies close in spirit with the method recently proposed to bound the Higgs-boson width [30][31][32].…”

“…This can be achieved via the method proposed in refs. [30][31][32]. The key idea is that the ratio of off-shell to on-shell cross section measurements is sensitive to the total Higgs width.…”

Interference effects for H → W W → ℓ ν q q ¯ ′ $$ H\to W\;W\to \ell \nu q{\overline{q}}^{\prime } $$ and H → Z Z → ℓ ℓ ¯ q q ¯ $$ H\to ZZ\to \ell \overline{\ell}q\overline{q} $$ searches in gluon fusion at the LHC

“…In the SM, interference between the Higgs signal and continuum background in gg (→ H) → V V (V = W, Z) and including fully leptonic decays has been studied in refs. [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. 1 Higgs-continuum interference results for a heavy SM Higgs boson have been presented in refs.…”