Pseudoscalar top-Higgs coupling: exploration of CP-odd observables to resolve the sign ambiguity

Abstract

We present a collection of CP-odd observables for the process pp → t (→ b + ν )t →b −ν H that are linearly dependent on the scalar (κ t ) and pseudoscalar (κ t ) top-Higgs coupling and hence sensitive to the corresponding relative sign. The proposed observables are based on triple product (TP) correlations that we extract from the expression for the differential cross section in terms of the spin vectors of the top and antitop quarks. In order to explore other possibilities, we progressively modify these TPs, first by combining them, and then by replacing the spin vectors by the lepton momenta or the t andt momenta by their visible parts. We generate Monte Carlo data sets for several benchmark scenarios, including the Standard Model (κ t = 1,κ t = 0) and two scenarios with mixed CP properties (κ t = 1,κ t = ±1). Assuming an integrated luminosity that is consistent with that envisioned for the High Luminosity Large Hadron Collider, using Monte Carlo-truth and taking into account only statistical uncertainties, we find that the most promising observable can disentangle the "CP-mixed" scenarios with an effective separation of ∼ 19σ. In the case of observables that do not require the reconstruction of the t andt momenta, the power of discrimination is up to ∼ 13σ for the same number of events. We also show that the most promising observables can still disentangle the CP-mixed scenarios when the number of events is reduced to values consistent with expectations for the Large Hadron Collider in the near term.

tWH associated production at the LHC

“…Indeed, unlike the dominant Higgs production mode via gluon fusion, where the extraction of y t is indirect, in the case of ttH such an extraction is (rather) model-independent. In addition, ttH production is known to be sensitive to the Higgs CP properties [20][21][22][23][24][25][26][27][28][29][30][31]. On the other hand, Higgs production in association with a single top quark (tH and tW H), though rare, is very sensitive to departures from the SM, since the total rate can increase by more than an order of magnitude [32,33] due to constructive interference effects, becoming comparable to or even larger than ttH.…”

Top and bottom tensor couplings from a color octet scalar

“…LHC related phenomenological studies have illustrated possible constraints on these couplings proposing a variety of observables: deviations from SM cross-sections [4,5], triple product ('T-odd') correlations [6][7][8][9][10][11][12][13], new CP-even spin correlations [14,15], lepton energy asymmetries [16], and associated production of Higgs bosons [17]. The bottom-quark CEDM and CMDM couplings have been studied in associated production with a Higgs boson [17,18].…”

Probing CP Violation in h→τ−τ+ at the LHC

“…The sensitivity is rather low because of the dominance of the tree-level (CPeven) hZZ amplitudes and the small (loop suppressed) hZγ * and hγ * γ * amplitudes. Processes pp → hjj [15], pp → htt [16], and h → τ + τ − [17,18] have also been analyzed.…”