No abstract

It has been shown that the longitudinal mode of a massive vector boson can be produced by inflationary fluctuations and account for the dark matter content of the Universe. In this work we examine the possibility of instead producing the transverse mode via the coupling φFF between the inflaton and the vector field strength. Such a coupling leads to a tachyonic instability and exponential production of one transverse polarization of the vector field, reaching its maximum near the end of inflation. At production the mass is negligible and the vectors add up coherently to form a dark electromagnetic field. As the Universe expands, the energy density of the dark electromagnetic field then redshifts like radiation until its wavelength stretches to beyond its Compton wavelength. After this point the vectors become non-relativistic and their energy density redshifts like matter. We show that these polarized transverse vectors can account for the observed dark matter relic density in the mass range µeV to hundreds of GeV. We also find that the tachyonic production mechanism of the transverse mode can accommodate larger vector masses and lower Hubble scales of inflation compared to the production mechanism for the longitudinal mode via inflationary fluctuations.

Kinematic distributions in the decays of the newly discovered resonance to four leptons are a powerful probe of the tensor structure of its couplings to electroweak gauge bosons. We present analytic calculations for both signal and background of the fully differential cross section for the 'Golden Channel' e + e − µ + µ − final state. We include all interference effects between intermediate gauge bosons and allow them to be on-or off-shell. For the signal we compute the fully differential decay width for general scalar couplings to ZZ, γγ, and Zγ. For the background we compute the leading order fully differential cross section for qq annihilation into Z and γ gauge bosons, including the contribution from the resonant Z → 2e2µ process. We also present singly and doubly differential projections and study the interference effects on the differential spectra. These expressions can be used in a variety of ways to uncover the nature of the newly discovered resonance or any new scalars decaying to neutral gauge bosons which might be discovered in the future.

We explore the sensitivity of the Higgs decay to four leptons, the so-called golden channel, to higher dimensional loop-induced couplings of the Higgs boson to ZZ, Zγ, and γγ pairs, allowing for general CP mixtures. The larger standard model tree level coupling hZ µ Zµ is the dominant "background" for the loop induced couplings. However this large background interferes with the smaller loop induced couplings, enhancing the sensitivity. We perform a maximum likelihood analysis based on analytic expressions of the fully differential decay width for h → 4 (4 ≡ 2e2µ, 4e, 4µ) including all interference effects. We find that the spectral shapes induced by Higgs couplings to photons are particularly different than the hZ µ Zµ background leading to enhanced sensitivity to these couplings. We show that even if the h → γγ and h → 4 rates agree with that predicted by the Standard Model, the golden channel has the potential to probe both the CP nature as well as the overall sign of the Higgs coupling to photons well before the end of a high-luminosity LHC.