Search for a heavy vector resonance decaying to a $${\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}$$ boson and a Higgs boson in proton-proton collisions at $$\sqrt{s} = 13\,\text {Te}\text {V} $$

A search is presented for a heavy vector resonance decaying into a $${\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}$$ Z boson and the standard model Higgs boson, where the $${\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}$$ Z boson is identified through its leptonic decays to electrons, muons, or neutrinos, and the Higgs boson is identified through its hadronic decays. The search is performed in a Lorentz-boosted regime and is based on data collected from 2016 to 2018 at the CERN LHC, corresponding to an integrated luminosity of 137$$\,\text {fb}^{-1}$$ fb - 1 . Upper limits are derived on the production of a narrow heavy resonance $${\mathrm{{{\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}}}}_{\mathrm{}}^{\mathrm{\prime }}$$ Z ′ , and a mass below 3.5 and 3.7$$\,\text {Te}\text {V}$$ Te is excluded at 95% confidence level in models where the heavy vector boson couples predominantly to fermions and to bosons, respectively. These are the most stringent limits placed on the Heavy Vector Triplet $${\mathrm{{{\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}}}}_{\mathrm{}}^{\mathrm{\prime }}$$ Z ′ model to date. If the heavy vector boson couples exclusively to standard model bosons, upper limits on the product of the cross section and branching fraction are set between 23 and 0.3$$\,\text {fb}$$ fb for a $${\mathrm{{{\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}}}}_{\mathrm{}}^{\mathrm{\prime }}$$ Z ′ mass between 0.8 and 4.6$$\,\text {Te}\text {V}$$ Te , respectively. This is the first limit set on a heavy vector boson coupling exclusively to standard model bosons in its production and decay.

On the transition form factors of the axial-vector resonance f1(1285) and its decay into e+e−

Estimating the contribution from axial-vector intermediate states to hadronic light-by-light scattering requires input on their transition form factors (TFFs). Due to the Landau–Yang theorem, any experiment sensitive to these TFFs needs to involve at least one virtual photon, which complicates their measurement. Phenomenologically, the situation is best for the f1(1285) resonance, for which information is available from e+e− → e+e−f1, f1 → 4π, f1 → ργ, f1 → ϕγ, and f1 → e+e−. We provide a comprehensive analysis of the f1 TFFs in the framework of vector meson dominance, including short-distance constraints, to determine to which extent the three independent TFFs can be constrained from the available experimental input — a prerequisite for improved calculations of the axial-vector contribution to hadronic light-by-light scattering. In particular, we focus on the process f1 → e+e−, evidence for which has been reported recently by SND for the first time, and discuss the impact that future improved measurements will have on the determination of the f1 TFFs.

Scattering of Goldstone bosons and resonance production in a composite Higgs model on the lattice

We calculate the coupling between a vector resonance and two Goldstone bosons in SU(2) gauge theory with Nf = 2 Dirac fermions in the fundamental representation. The considered theory can be used to construct a minimal Composite Higgs models. The coupling is related to the width of the vector resonance and we determine it by simulating the scattering of two Goldstone bosons where the resonance is produced. The resulting coupling is gVPP = 7.8 ± 0.6, not far from gρππ ≃ 6 in QCD. This is the first lattice calculation of the resonance properties for a minimal UV completion. This coupling controls the production cross section of the lightest expected resonance at the LHC and enters into other tests of the Standard Model, from Vector Boson Fusion to electroweak precision tests. Our prediction is crucial to constrain the model using lattice input and for understanding the behavior of the vector meson production cross section as a function of the underlying gauge theory. We also extract the coupling $$ {g}_{\mathrm{VPP}}^{\mathrm{KSRF}} $$ g VPP KSRF = 9.4 ± 0.6 assuming the vector-dominance and find that this phenomenological estimate slightly overestimates the value of the coupling.

DK I = 0, $$ D\overline{K} $$ I = 0, 1 scattering and the $$ {D}_{s0}^{\ast } $$(2317) from lattice QCD

Elastic scattering amplitudes for I = 0 DK and I = 0, 1 $$ D\overline{K} $$ D K ¯ are computed in S, P and D partial waves using lattice QCD with light-quark masses corresponding to mπ = 239 MeV and mπ = 391 MeV. The S-waves contain interesting features including a near-threshold JP = 0+ bound state in I = 0 DK, corresponding to the $$ {D}_{s0}^{\ast } $$ D s 0 ∗ (2317), with an effect that is clearly visible above threshold, and suggestions of a 0+ virtual bound state in I = 0 $$ D\overline{K} $$ D K ¯ . The S-wave I = 1 $$ D\overline{K} $$ D K ¯ amplitude is found to be weakly repulsive. The computed finite-volume spectra also contain a deeply-bound D* vector resonance, but negligibly small P -wave DK interactions are observed in the energy region considered; the P and D-wave $$ D\overline{K} $$ D K ¯ amplitudes are also small. There is some evidence of 1+ and 2+ resonances in I = 0 DK at higher energies.

Top partner-resonance interplay in a composite Higgs framework

Guided us by the scenario of weak scale naturalness and the possible existence of exotic resonances, we have explored in a [Formula: see text] Composite Higgs setup the interplay among three matter sectors: elementary, top partners and vector resonances. We parametrize it through explicit interactions of spin-1 [Formula: see text]-resonances, coupled to the [Formula: see text]-invariant fermionic currents and tensors presented in this work. Such invariants are built upon the Standard Model fermion sector as well as top partners sourced by the unbroken [Formula: see text]. The mass scales entailed by the top partner and vector resonance sectors will control the low energy effects emerging from our interplaying model. Its phenomenological impact and parameter spaces have been considered via flavor-dijet processes and electric dipole moments bounds. Finally, the strength of the Nambu–Goldstone symmetry breaking and the extra couplings implied by the top partner mass scales are measured in accordance with expected estimations.