W Boson Production at NLO
We discuss W boson production at HERA including NLO QCD corrections. A detailed comparison with previous work is presented.
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arXiv subjects
Michael Spira
Publications and source records attributed to Michael Spira.
Higgs Radiation off Quarks in the Standard Model and supersymmetric Theories at e+e- Colliders
Yukawa couplings between Higgs bosons and quarks in the Standard Model (SM) and supersymmetric theories can be measured in the processes e+e- -> Q\bar{Q} + Higgs. The cross sections and Higgs energy distributions of these processes in the SM and minimal supersymmetric model have been determined including the complete set of next-to-leading order QCD corrections for all channels.
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SUSY-QCD Corrections to Higgs Boson Production at Hadron Colliders
We analyze the next-to-leading order SUSY-QCD corrections to the production of Higgs particles at hadron colliders in supersymmetric extensions of the Standard Model. Besides the standard QCD corrections due to gluon exchange and emission, genuine supersymmetric corrections due to the virtual exchange of squarks and gluinos are present. At both the Tevatron and the LHC, these corrections are found to be small in the Higgs-strahlung, Drell-Yan-like Higgs pair production and vector boson fusion processes.
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SUSY Particle Production at Hadron Colliders
The determination of the full SUSY QCD corrections to the production of squarks, gluinos and gauginos at hadron colliders is reviewed. The NLO corrections stabilize the theoretical predictions of the various production cross sections significantly and lead to sizeable enhancements of the most relevant cross sections. We discuss the phenomenological consequences of the results on present and future experimental analyses.
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Higgs Boson Production and Decay at the Tevatron
The theoretical status of Higgs boson production and decay at the Tevatron within the Standard Model and its minimal supersymmetric extension is reviewed. The focus will be on the evaluation of higher-order corrections to the production cross sections and their phenomenological implications.
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Electroweak Symmetry Breaking and Higgs Physics
An introduction to electroweak symmetry breaking and Higgs physics is presented for the Standard Model and its supersymmetric extensions. A brief overview will also be given on strong interactions of the electroweak gauge bosons in alternative scenarios. In addition to the theoretical basis, the present experimental status of Higgs physics and implications for future experiments at the LHC and $e^+e^-$ linear colliders are discussed.
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MSSM Higgs Boson Production at the LHC
The theoretical status of Higgs boson production at the LHC within the minimal supersymmetric extension of the Standard Model is reviewed. The focus will be on the evaluation of higher-order corrections to the production cross sections and their phenomenological implications.
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Squark and Gluino Production at Hadron Colliders
The theoretical status of squark and gluino production at present and future hadron colliders is reviewed. I shall concentrate on the evaluation of SUSY-QCD corrections to the production cross sections and their phenomenological implications.
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Higgs Bosons Strongly Coupled to the Top Quark
Several extensions of the Standard Model require the burden of electroweak symmetry breaking to be shared by multiple states or sectors. This leads to the possibility of the top quark interacting with a scalar more strongly than it does with the Standard Model Higgs boson. In top-quark condensation this possibility is natural. We also discuss how this might be realized in supersymmetric theories. The properties of a strongly coupled Higgs boson in top-quark condensation and supersymmetry are described. We comment on the difficulties of seeing such a state at the Tevatron and LEPII, and study the dramatic signatures it could produce at the LHC. The four top quark signature is especially useful in the search for a strongly coupled Higgs boson. We also calculate the rates of the more conventional Higgs boson signatures at the LHC, including the two photon and four lepton signals, and compare them to expectations in the Standard Model.
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Higgs Production and Decay at Future Machines
Higgs boson production at future colliders within the Standard Model and its minimal supersymmetric extension is reviewed. The predictions for decay rates and production cross sections are presented including all relevant higher-order corrections.
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QCD Effects in Higgs Physics
Higgs boson production at the LHC within the Standard Model and its minimal supersymmetric extension is reviewed. The predictions for decay rates and production cross sections are updated by choosing the present value of the top quark mass and recent parton density sets. Moreover, all relevant higher order corrections, some of which have been obtained only recently, are included in a consistent way.
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Squark and Gluino Production at Hadron Colliders
The determination of the full SUSY QCD corrections to the production of squarks and gluinos at hadron colliders is reviewed. The inclusion of the NLO corrections stabilizes the theoretical predictions of the various production cross sections significantly and leads to sizeable enhancements of the most relevant cross sections. We discuss the phenomenological consequences of the results on present and future experimental analyses. Finally we investigate the impact of the corrections on the transverse momentum and rapidity distributions.
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Soft Gluon Radiation in Higgs Boson Production at the LHC
We examine the contributions of soft gluons to the Higgs production cross section at the LHC in the Standard Model and its minimal supersymmetric extension. The soft gluon radiation effects of this reaction share many features with the Drell-Yan process, but arise at lowest order from a purely gluonic initial state. We provide an extension of the conventional soft gluon resummation formalism to include a new class of contributions which we argue to be universal, and resum these and the usual Sudakov effects to all orders. The effect of these new terms is striking: only if they are included, does the expansion of the resummed cross section to next-to-leading order reproduce the exact result to within a few percent for the full range of Higgs boson masses. We use our resummed cross section to derive next-to-next-to-leading order results, and their scale dependence. Moreover, we demonstrate the importance of including the novel contributions in the resummed Drell-Yan process.
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Higgs Boson Production at the LHC
Recent theoretical progress in the evaluation of Higgs boson production at the LHC within the Standard Model and its minimal supersymmetric extension is reviewed. In particular the two-loop QCD corrections to the squark loop contributions to scalar Higgs production in the MSSM and soft gluon resummation effects in Standard and SUSY Higgs production via the gluon fusion mechanism are discussed.
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HIGLU and HDECAY: Programs for Higgs Boson Production at the LHC and Higgs Boson Decay Widths
The total cross section for Higgs boson production via the dominant gluon fusion mechanism including NLO [two-loop] QCD corrections can be calculated numerically with the program HIGLU. The QCD corrections are included for arbitrary Higgs and quark masses and increase the cross section at the LHC by up to a factor of 2. The source code HIGLU provides the evaluation of the production of the Standard Model [SM] Higgs boson as well as the neutral Higgs bosons of the minimal supersymmetric extension [MSSM]. The program HDECAY determines the decay widths and branching ratios of the Higgs bosons within the SM and the MSSM, including the dominant higher-order corrections. The latter are dominated by QCD corrections and two-loop corrections to the couplings and Higgs masses of the MSSM. The program includes all decay modes with branching ratios larger than $10^{-4}$. Moreover, below-threshold decays with off-shell top quarks, gauge and Higgs bosons are implemented. In addition the program is able to calculate the branching ratios of the MSSM Higgs bosons into supersymmetric particles, which can be dominant.
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QCD CORRECTIONS TO HIGGS BOSON DECAYS
The two--loop ${\cal O}(α_s G_F m_t^2)$ corrections to the $b\bar b$ decay rate of the Standard Model Higgs boson as well as its production via $e^+e^- \to ZH$ will be presented. These QCD corrections are obtained by using a low-energy theorem for light Higgs bosons compared to the top quark mass. The results yield strong screening effects of the ${\cal O}(G_F m_t^2)$ contributions. After that the two-loop QCD corrections to the $γγ$ and gluonic decays of the Higgs bosons of the Standard Model and its minimal supersymmetric extension are discussed. While the corrections to the $γγ$ decays remain small of ${\cal O}(α_s)$ they are huge $\sim$ 50 -- 70 \% in the case of the gluonic decays.
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Two-Loop ${\cal O}(α_sG_Fm_t^2)$ Corrections to Higgs Production at LEP
We evaluate the two-loop ${\cal O}(α_sG_Fm_t^2)$ correction to the $ZZH$ coupling in the Standard Model by means of a low-energy theorem, assuming that the top quark is much heavier than the Higgs boson. We then construct a heavy-top-quark effective Lagrangian for the $ZZH$ interaction that accommodates the ${\cal O}(G_Fm_t^2)$ and ${\cal O}(α_sG_Fm_t^2)$ corrections and derive from it the corresponding corrections to the $H\to ZZ$ decay as well as those to Higgs-boson production at LEP1, via $Z\to f\bar fH$, and at LEP2, via $e^+e^-\to ZH$. In all cases, the leading ${\cal O}(G_Fm_t^2)$ terms are considerably screened by their QCD corrections, if the on-shell renormalization scheme with $G_F$ as a basic parameter is employed.
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Two-Loop $ O(α_sG_Fm_t^2)$ Correction to the $H\to b\bar b$ Decay Rate
We present the two-loop ${\cal O}(α_sG_Fm_t^2)$ correction to the $b\bar b$ decay rate of the Stan\-dard-Model Higgs boson, assuming that the $t$ quark is much heavier than the Higgs boson. Apart from the universal correction connected with the renormalizations of the wave function and the vacuum expectation value of the Higgs field, this involves vertex corrections specific to the presence of beauty in the final state. We calculate the latter by means of a low-energy theorem. All would-be mass singularities related to the $b$ quark can be absorbed into the running Higgs-bottom Yukawa coupling. It turns out that the total ${\cal O}(α_sG_Fm_t^2)$ correction screens the leading high-$m_t$ behaviour of the one-loop result by 71\% to 75\% for $M_H$ between 60~GeV and $2M_W$.
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