Abstract
The Higgs decay h → 4l has played an important role in discovering the Higgs and measuring its mass thanks to low background and excellent resolution. Current cuts in this channel have been optimized for Higgs discovery via the dominant tree level ZZ contribution arising from electroweak symmetry breaking. Going forward, one of the primary objectives of this sensitive channel will be to probe other Higgs couplings and search for new physics on top of the tree level ZZ `back-ground'. Thanks to interference between these small couplings and the large tree level contribution to ZZ, the h → 4l decay is uniquely capable of probing the magnitude and CP phases of the Higgs couplings to and Z as well as, to a lesser extent, ZZ couplings arising from higher dimensional operators. With this in mind we examine how much relaxing current cuts can enhance the sensitivity while also accounting for the dominant non-Higgs continuum qq → 4l background. We find the largest enhancement in sensitivity for the hZy couplings (≳ 100%) followed by hyy (≳ 40%) and less so for the higher dimensional hZZ couplings (a few percent). With these enhancements, we show that couplings of order Standard Model values for hyy may optimistically be probed by end of Run-II at the LHC while for hZy perhaps towards the end of a high luminosity LHC. Thus an appropriately optimized h → 4l analysis can complement direct decays of the Higgs to on-shell and Z pairs giving a unique opportunity to directly access the CP properties of these couplings.
Highlights
Background effects on sensitivityWith the signal plus background likelihood in hand we can go on to assess the effects of the qq → 4 background
Thanks to interference between these small couplings and the large tree level contribution to ZZ, the h → 4 decay is uniquely capable of probing the magnitude and CP phases of the Higgs couplings to γγ and Zγ as well as, to a lesser extent, ZZ couplings arising from higher dimensional operators
We have demonstrated that utilizing relaxed cuts or alternative lepton pairings during event selection can significantly enhance the sensitivity of the h → 4 channel to the Higgs couplings to Zγ and γγ pairs relative to that found utilizing current CMS event selection criteria
Summary
One may wonder whether there is any advantage to searching for these couplings in h → 4 rather than looking directly for Higgs decays to on-shell γγ and Zγ. Interference terms are suppressed by other factors but this gives them a head-start in terms of sensitivity [38] It has been shown recently [27, 35, 36, 38] that the h → 4 (4 ≡ 2e2μ, 4e, 4μ) decay can be used to probe the Higgs couplings to Zγ and γγ as well as ZZ pairs. In particular it was shown [38] that even with existing cuts the LHC experiments will be able to probe sub-SM-sized hγγ couplings by the end of high luminosity running while the sensitivity to SM-sized hZγ couplings is weaker, but possibly not hopeless This is despite the fact that these cuts were designed to enhance the Higgs discovery via the tree level hZZ component. In this work we examine relaxing some of the cuts in order to enhance the sensitivity to hγγ and hZγ couplings and assess to what extent the LHC may be able to probe these couplings
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
