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Register a new userPrecise test of Higgs properties via triple Higgs production in VBF at future colliders
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For certain classes of Beyond the Standard Model theories, including composite Higgs models, the coupling of the Higgs to gauge bosons can be different from the Standard Model one. In this case, the multi-boson production via vector boson fusion (VBF) can be hugely enhanced in comparison to the SM production one due to the lack of cancellation in longitudinal vector boson scattering. Among these processes, triple Higgs boson production in VBF plays a special role - its enhancement is especially spectacular due to the absence of background from transversely polarised vector bosons in the final state. While the rates from $ppto jjhhh$ production in vector boson fusion are too low at the LHC and even at future 33 TeV $pp$ colliders, we have found that the 100 TeV $pp$ future circular collider (FCC) has the unique opportunity to probe the $hVV$ coupling far beyond the LHC sensitivity. We have evaluated the $ppto jjhhh$ rates as a function of deviation from the $hVV$ coupling and have found that the background is much smaller than the signal for observable signal rates. We also found that the 100 TeV $pp$ FCC can probe the $hVV$ coupling up to the permille level, which is far beyond the LHC reach. These results highlight a special role of the $hhh$ VBF production and stress once more the importance of the 100 TeV $pp$ FCC.
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An important task at future colliders is the investigation of the Higgs-boson sector. Here the measurement of the triple Higgs coupling(s) plays a special role. Based on previous analyses, within the framework of Two Higgs Doublet Models (2HDM) type~I and~II, we define and analyze several two-dimensional benchmark planes, that are over large parts in agreement with all theoretical and experimental constraints. For these planes we evaluate di-Higgs production cross sections at future high-energy $e^+e^-$ colliders, such as ILC or CLIC. We consider two different channels for the neutral di-Higgs pairs $h_i h_j=hh,hH,HH,AA$: $e^+e^- to h_i h_j Z$ and $e^+e^- to h_i h_j u bar u$. In both channels the various triple Higgs-boson couplings contribute substantially. We find regions with a strong enhancement of the production channel of two SM-like light Higgs bosons and/or with very large production cross sections involving one light and one heavy or two heavy 2HDM Higgs bosons, offering interesting prospects for the ILC or CLIC. The mechanisms leading to these enhanced production cross sections are analyzed in detail. We propose the use of cross section distributions with the invariant mass of the two final Higgs bosons where the contributions from intermediate resonant and non-resonant BSM Higgs bosons play a crucial role. We outline which process at which center-of-mass energy would be best suited to probe the corresponding triple Higgs-boson couplings.
For the search for additional Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM) as well as for future precision analyses in the Higgs sector a precise knowledge of their production properties is mandatory. We review the evaluation of the cross sections for the neutral Higgs boson production in association with a photon at future $e^+e^-$ colliders in the MSSM with complex parameters (cMSSM). The evaluation is based on a full one-loop calculation of the production mechanism $e^+e^- to h_i gamma$ ($i = 1,2,3$). The dependence of the lightest Higgs-boson production cross sections on the relevant cMSSM parameters is analyzed numerically. We find relatively small numerical depedences of the production cross sections on the underlying parameters.
Future $gammagamma$ colliders allow the production of the heavy neutral MSSM Higgs bosons $H$ and $A$ as single resonances. The prospects of finding these particles in the $bbar{b}$ and the neutralino-pair final states have been analysed. The $H,A$ bosons can be discovered for medium values of $tanbeta$ with masses up to 70--80% of the initial $e^pm e^-$ c.m. energy. This production mode thus covers parts of the supersymmetric parameter space that are not accessible at other colliders.
The measurement of the triple Higgs coupling is a key benchmark for the LHC and future colliders. It directly probes the Higgs potential and its fundamental properties in connection to new physics beyond the Standard Model. There exist two phase space regions with an enhanced sensitivity to the Higgs self-coupling, the Higgs pair production threshold and an intermediate top pair threshold. We show how the invariant mass distribution of the Higgs pair offers a systematic way to extract the Higgs self-coupling, focusing on the leading channel $ppto hh+Xto bbar b gammagamma+X$. We utilize new features of the signal events at higher energies and estimate the potential of a high-energy upgrade of the LHC and a future hadron collider with realistic simulations. We find that the high-energy upgrade of the LHC to 27 TeV would reach a 5$sigma$ observation with an integrated luminosity of 2.5 ab$^{-1}$. It would have the potential to reach 15% (30%) accuracy at the 68% (95%) confidence level to determine the SM Higgs boson self-coupling. A future 100 TeV collider could improve the self-coupling measurement to better than 5% (10%) at the 68% (95%) confidence level.
I report on a calculation of the inclusive Higgs boson production cross section at hadron colliders at next-to-next-to-leading order in QCD. The result is computed as an expansion about the threshold region. By continuing the expansion to very high order, we map the result onto basis functions and obtain the result in closed analytic form.
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