Spherical Parametrization of the Higgs Boson Candidate

Abstract

The latest results from the ATLAS and CMS experiments at the CERN Large Hadron Collider unequivocally confirm the existence of a resonance X with mass near 125 GeV which could be the Higgs boson of the standard model. Measuring the properties (quantum numbers and couplings) of this resonance is of paramount importance. Initial analyses by the LHC Collaborations disfavor specific alternative benchmark hypotheses, e.g., pure pseudoscalars or gravitons. However, this is just the first step in a long-term program of detailed measurements. We consider the most general set of operators in the decay channels X ! ZZ, WW, Z, , and derive the constraint implied by the measured rate. This allows us to provide a useful parametrization of the orthogonal independent Higgs coupling degrees of freedom as coordinates on a suitably defined sphere. In this Letter, we provide a theoretical framework for spin and coupling measurements in full generality, without theoretical prejudice toward specific benchmarks. In contrast to recent global fits of Higgs couplings [11,12], our approach is geared toward a more model independent measurement in a single channel, including all relevant operators and utilizing all available kinematic information. For concreteness and simplicity, we consider the example of a spin-zero X resonance, decaying to four leptons through two intermediate Z bosons [13][14][15][16], though our approach can be readily extended to other spins and final states. The complete measurement of the X couplings in full generality will provide insights into the nature of electroweak symmetry breaking and may offer the first glimpses of physics beyond the standard model (SM).Effective theory.-In what follows, we will consider a spin-zero state X. In general, X has no definite CP properties, and can be thought of as a linear combination of some CP-even state H and some CP-odd state A [12]:

Cornering dimension-6 HV V interactions at high energy LHC: the role of event ratios

“…Even within their current limits, some of the operators are found to modify the efficiencies of the various kinetic cuts [9,14]. The question we address in the rest of the paper is: can these limits be improved in the next run(s) through careful measurement of the ratios of total rates in different channels?…”

“…In constructing R 2 , we include the modified cut-efficiencies [9,14] for both the V BF and W H channels. Even though we stick to small values of f i where the modification in such efficiencies from the SM-values are small, we still incorporate these to make the study more rigorous.…”

QCD corrections to vector boson pair production in gluon fusion including interference effects with off-shell Higgs at the LHC

“…There are several ways to make this assumption invalid. For example, one can extend the theory to include relatively light colored particles that contribute to the ggH coupling [12], new Higgs resonances [13] or anomalous HZZ couplings [14][15][16]. However, all such cases will give rise to relatively clear signatures of New Physics at the LHC, beyond changes in the Higgs width or a change in the number of events in the off-shell region.…”

Extended scalar sectors, effective operators and observed data

“…The role and usefulness of higher-dimensional operators in dealing with unknown physics in Higgs phenomenology have already been discussed in a large body of works found in the literature [2][3][4][5][6][7][8][9][10][11][12][13]17]. For example, in [17], ways towards improved under-standing on the dimension-6 hV V operators in the high luminosity run of the LHC have been suggested.…”

“…Thus the most general dimension-6 operators which give rise to hV V vertices (V = W, Z) get constrained from the rates of these processes, as tree-level processes are unlikely to bear clear enough stamps of of such operators. Constraints on these higher dimensional operators as well as the scale factors κ have been extensively studied on the basis of electroweak precision test and global fits of Higgs data in [2][3][4][5][6][7][8][9][10][11][12][13].…”