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Register a new userEffects of the anomalous Higgs couplings on the Higgs boson production at the Large Hadron Collider
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We study the impact of dimension-six operators on single- and double-Higgs production rates via gluon fusion at the Large Hadron Collider (LHC). If the top-Yukawa coupling is modified by some new physics whose scale is of the TeV scale, its effect changes the cross sections of single-Higgs production $ggto H$ and double-Higgs production $ggto HH$ through the top-loop diagram. In particular, double-Higgs production can receive significant enhancement from the effective top-Yukawa coupling and the new dimension-five coupling $t{bar t}HH$ which are induced by the dimension-six operator. Comparing these results to the forthcoming data at the LHC, one can extract information of the dimension-six operators relevant to the top quark and the Higgs boson.
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Charged lepton pairs are produced copiously in high-energy hadron collisions via electroweak gauge boson exchange, and are one of the most precisely measured final states in proton-proton collisions at the Large Hadron Collider (LHC). We propose that measurements of lepton angular distributions can be used to improve the accuracy of theoretical predictions for Higgs boson production cross sections at the LHC. To this end, we exploit the sensitivity of the lepton angular coefficient associated with the longitudinal Z-boson polarization to the parton density function (PDF) for gluons resolved from the incoming protons, in order to constrain the Higgs boson cross section from gluon fusion processes. By a detailed numerical analysis using the open-source platform xFitter, we find that high-statistics determinations of the longitudinally polarized angular coefficient at the LHC Run III and high-luminosity HL-LHC improve the PDF systematic uncertainties of the Higgs boson cross section predictions by 50% over a broad range of Higgs boson rapidities.
We investigate the viability of observing charged Higgs bosons (H^+/-) produced in association with W bosons at the CERN Large Hadron Collider, using the leptonic decay H^+ -> tau^+ nu_tau and hadronic W-decay, within different scenarios of the Minimal Supersymmetric Standard Model (MSSM) with both real and complex parameters. Performing a parton level study we show how the irreducible Standard Model background from W+2 jets can be controlled by applying appropriate cuts and find that the size of a possible signal depends on the cuts needed to suppress QCD backgrounds and misidentifications. In the standard maximal mixing scenario of the MSSM we find a viable signal for large tan(beta) and intermediate H^+/- masses (~m_t) when using optimistic cuts whereas for more pessimistic ones we only find a viable signal for very large tan(beta) (>~50). We have also investigated a special class of MSSM scenarios with large mass-splittings among the heavy Higgs bosons where the cross-section can be resonantly enhanced by factors up to one hundred, with a strong dependence on the CP-violating phases. Even so we find that the signal after cuts remains small except for small masses (~< m_t) with optimistic cuts. Finally, in all the scenarios we have investigated we have only found small CP-asymmetries.
We consider a minimal extension of the standard model where a real, gauge singlet scalar field is added to the standard spectrum. Introducing the Ansatz of universality of scalar couplings, we are led to a scenario which has a set of very distinctive and testable predictions: (i) the mixing between the standard model Higgs and the new state is near maximal, (ii) the ratio of the two Higgs mass eigenstates is fixed ($sim sqrt{3}$), (iii) the decay modes of each of the two eigenstates are standard model like. We also study how electroweak precision tests constrain this scenario. We predict the lighter Higgs to lie in the range of 114 and 145 GeV, and hence the heavier one between 198 and 250 GeV. The predictions of the model can be tested at the upcoming LHC.
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.
We study the prospects for constraining the Higgs bosons couplings to up and down quarks using kinematic distributions in Higgs production at the CERN Large Hadron Collider. We find that the Higgs $p_T$ distribution can be used to constrain these couplings with precision competitive to other proposed techniques. With 3000 fb$^{-1}$ of data at 13 TeV in the four-lepton decay channel, we find $-0.73 lesssim bar{kappa}_u lesssim 0.33$ and $-0.88 lesssim bar{kappa}_d lesssim 0.32$, where $bar{kappa}_q = (m_q/m_b) kappa_q$ is a scaling factor that modifies the $q$ quark Yukawa coupling relative to the Standard Model bottom quark Yukawa coupling. The sensitivity may be improved by including additional Higgs decay channels.
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