Determining the Structure of Higgs Couplings at the CERN Large Hadron Collider

Abstract

Higgs boson production via weak boson fusion at the CERN Large Hadron Collider has the capability to determine the dominant CP nature of a Higgs boson, via the tensor structure of its coupling to weak bosons. This information is contained in the azimuthal angle distribution of the two outgoing forward tagging jets. The technique is independent of both the Higgs boson mass and the observed decay channel.The CERN Large Hadron Collider (LHC) is generally regarded as a tool that can guarantee direct observation of a Higgs boson, the remnant of the mechanism believed responsible for electroweak symmetry breaking and fermion mass generation, and the last unobserved element of the Standard Model (SM) of elementary particle physics. Furthermore, the LHC promises complete coverage of Higgs decay scenarios [1,2], including general MSSM parameterizations [1,3], and even invisible Higgs decays [4]. This capability has been greatly enhanced recently by the addition of the weak boson fusion (WBF) production channel to the search strategies [3,5,6]. While being extremely useful at the LHC, WBF has too low a rate and is too similar to background processes at the Fermilab Tevatron [7].Observation of a resonance in some expected decay channel is, however, only the beginning of Higgs physics. Continuing efforts will include the search for more than one Higgs boson, as predicted e.g. by two-Higgs doublet models, of which the MSSM [8,9] is a subset. At least as important is the detailed study of the properties of the Higgs-like resonance, not only at a future Linear Collider [10] but also at the LHC: determination of all the quantum numbers and couplings of the state. These include the gauge, Yukawa and self-couplings as well as the charge, color, spin, and CP quantum numbers. While charge and color identification is straightforward and a technique has been proposed for the gauge and Yukawa coupling determinations [11], the LHC has considerable difficulty in practice to determine the Higgs CP transformation properties for intermediate Higgs masses [12] via a weak boson coupling, and no technique has yet been proposed to identify the tensor structure of the Higgs-weak boson vertex in the intermediate mass range. The methods of Ref.[13] may be useful, but only for very light Higgs masses. Furthermore, this method does not involve the weak boson vertices at all.In this letter we propose a technique which achieves the CP measurement goal via a study of WBF events. WBF Higgs production, while not the largest cross section at the LHC, is useful because of its characteristic kinematical structure, involving two forward tagging jets and central Higgs decay products, which allows one to isolate the signal in a low background environment. The angular distribution of the two tagging jets carries unambiguous information on the CP properties of the Higgs couplings to weak bosons which is independent of the Higgs decay channel observed.As a theoretical framework we consider two possible ways to couple a spin zero field to two gauge bosons via hig...

Detection of the neutral MSSM Higgs bosons in the intense-coupling regime at the LHC

“…In addition, the process qq → h, H → τ + τ − discussed in Ref. [12] cannot be used to resolve the two h and H peaks in the intense-coupling regime, because of the poor resolution on the τ + τ − invariant mass.…”

QCD corrections to jet correlations in weak boson fusion

“…Since the anomalous Lagrangian in Eq. (2) A much better observable for distinguishing the different tensor structures of the HV V vertex is the azimuthal angle correlation of the two tagging jets, dσ/dφ jj [6]. Here φ jj is the azimuthal angle between the two tagging jets.…”

“…It was pointed out some time ago that the azimuthal angle correlations of the two quark jets in the weak boson fusion process qQ → qQH provide tell-tale signatures for the tensor structure of the HV V couplings [6]: the SM expectation is for a flat distribution, while the loop-induced couplings lead to a pronounced dip at azimuthal separations φ jj of the two tagging jets of 90 degrees for a HV µν V µν coupling and at 0 and 180 degrees for the CP violating HV µνṼ µν vertex. Observation of the tagging jets is crucial for isolating the WBF process from backgrounds and, therefore, their distributions will be available for all WBF samples.…”

“…[6] was performed at leading order (LO) in QCD. This means that additional gluon emission, which might lead to a de-correlation of the tagging jets, was ignored in the analysis.…”

Higgs physics: Theory

“…Alternatively, one can study the distribution in the azimuthal angle between the two jets produced in association with the Higgs produced in the vector boson fusion process or in gluon fusion in Higgs plus jet events [90,91]. Figure 14 (right) shows the azimuthal angle distribution for the two jets produced in association with the Higgs, for the CP-even and CP-odd cases.…”