Off-shell Higgs production at the LHC as a probe of the trilinear Higgs coupling

Abstract

In the context of the Standard Model effective field theory (SMEFT) we examine the constraints on the trilinear Higgs coupling that originate from off-shell Higgs production in proton-proton collisions. Our calculation of the gg → h* → ZZ → 4ℓ process includes two-loop corrections to gluon-gluon-fusion Higgs production and one-loop corrections to the Higgs propagator and its decay. Employing a matrix-element based kinematic discriminant we determine the reach of LHC Run 3 and the high-luminosity option of the LHC in constraining the relevant SMEFT Wilson coefficients. We present constraints that are not only competitive with but also complementary to the projected indirect limits that one expects to obtain from inclusive measurements of single-Higgs production processes at future LHC runs.

Probing Higgs portals with matrix-element based kinematic discriminants in $ZZ \to 4 \ell$ production

“…Being sensitive not only to m 4 but also to another seven variables such as the invariant masses of the two opposite-sign lepton pairs (for details consult the articles [41][42][43]), ME-based discriminants fully exploit the event kinematics. As in our recent study [44], we find that the use of a ME method leads to a significantly improved coverage of the BSM parameter space, i.e. c φ and m φ in the case of (1.1), than a shape analysis of the m 4 distribution.…”

“…Notice that (3.2) is accurate in the case of the m 4 spectrum. For the D S distribution one observes [44] a close to flat K-factor of around 1.6 between the LO and the improved prediction (3.2). It is furthermore found that the inclusion of higher-order QCD corrections reduces the scale uncertainties by a factor of about 3 from…”

“…By comparing the relative modifications in the right panels of Figures 2 and 3 it should be already clear that the four-lepton invariant mass m 4 has a much weaker discriminating power than the variable D S in constraining interactions of the form (1.1). In order to make this statement quantitative we perform a shape analysis of both the m 4 and D S spectrum following the method outlined in our earlier work [44]. Specifically, the significance Z i is calculated as a Poisson ratio of likelihoods modified to incorporate systematic uncertainties on the background using the Asimov approximation [61]:…”

“…To include higher-order QCD corrections in our pp → ZZ → 4 analysis, we proceed as in our recent work [44]. For the two relevant production channels we calculate the socalled K-factor defined as the ratio between the fiducial cross section at a given order in QCD and the corresponding leading order (LO) QCD prediction.…”

One-loop on-shell and off-shell decay $H^*\rightarrow VV$ at future $e^-e^-$ collider

“…Recently, off-shell Higgs decay H * → Z * Z * → 4 leptons have been measured at the LHC in [3,4,5,6,7,8]. We also can find many interesting points from the phenomenological studies for off-shell Higgs decays in [9,10,11,12,14,15,16,17,18,19,20]. In all mentioned references, the authors have not only provided the framework for testing the Higgs scalar sector at different energy scales but also discussed the possibility to explore new physics beyond the SM (BSM).…”