Abstract
We compute the interference between the resonant process $pp\to H(\rightarrow \gamma\gamma)+2 \text{ jets}$ and the corresponding continuum background at leading order in QCD. For the Higgs signal, we include gluon fusion (GF) and vector boson fusion (VBF) production channels, while for the background we consider all tree-level contributions, including pure EW effects (${\cal O}(\alpha_{QED}^4)$) and QCD contributions (${\cal O}(\alpha_{QED}^2 \alpha_{s}^2)$), plus the loop-induced gluon-initiated process. After convolution with the experimental mass resolution, the main effect of the interference is to shift the position of the mass peak, as in the inclusive GF case studied previously. The apparent mass shift is small in magnitude but strongly dependent on the Higgs width, potentially allowing for a measurement of, or bound on, the width itself. In the $H(\rightarrow \gamma\gamma)+2 \text{ jets}$ channel, the VBF and GF contributions generate shifts of opposite signs which largely cancel, depending on the sets of cuts used, to as little as 5 MeV (toward a lower Higgs mass). The small magnitude of the shift makes this channel a good reference mass for measuring the inclusive mass shift of around 60 MeV in the Standard Model.
Highlights
In 2012, the ATLAS and CMS collaborations at the Large Hadron Collider (LHC) observed a new particle whose measured properties are, so far, compatible with the Standard Model (SM) Higgs boson [1, 2]
We will study the effect of the signal-background interference for both the gluon fusion (GF) and Vector Boson Fusion (VBF) production mechanisms.† By adjusting the cuts on the associated jets, we can use a cancellation between GF and VBF mass shifts to minimize the mass shift in this sample, making it an excellent reference mass for studies at high LHC luminosity, instead of or in addition to the ZZ∗ reference mass in eq (3)
As pointed out in Refs. [4, 5], this implies that the first term in eq (5), arising from the real part of the Breit-Wigner — which is odd in saround mH — is strongly suppressed by the integral across the resonance. (This is true provided that all s-dependent functions vary slowly across the resonance, which is the case.) as shown by Martin [6], the experimental smearing does leave behind a quantifiable effect on the position of the diphoton invariant mass peak, shifting it to lower masses by O(100 MeV) at leading order in αs (LO)
Summary
In 2012, the ATLAS and CMS collaborations at the Large Hadron Collider (LHC) observed a new particle whose measured properties are, so far, compatible with the Standard Model (SM) Higgs boson [1, 2]. [10] — is disrupted in the lineshape model mentioned above This is a powerful method, already leading to bounds from CMS [16] and ATLAS [17] that are of order Γ/ΓSM < 4.5, much smaller than eq (4). [9] it was proposed to use a subsample of the inclusive GF γγ sample with nonzero Higgs transverse momentum pT,H , taking advantange of a strong dependence of the mass shift on pT,H [8] This dependence is difficult to predict very precisely theoretically. In this paper we propose using another γγ sample, in which the two photons are produced in association with two jets This process is relatively rare, so is the background, making it possible to obtain reasonable statistical uncertainties on the position of the mass peak in this channel, despite the lower number of events. We will study the effect of the signal-background interference for both the GF and VBF production mechanisms.† By adjusting the cuts on the associated jets, we can use a cancellation between GF and VBF mass shifts to minimize the mass shift in this sample, making it an excellent reference mass for studies at high LHC luminosity, instead of or in addition to the ZZ∗ reference mass in eq (3)
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