Hadronic production of a Higgs boson in association with two jets at ...
Hadronic production of a Higgs boson in association with two jets at ...
Hadronic production of a Higgs boson in association with two jets at ...
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Chapter 7ConclusionsIn this thesis we have studied the hadronic <strong>production</strong> <strong>of</strong> a <strong>Higgs</strong> <strong>boson</strong> <strong>in</strong> <strong>associ<strong>at</strong>ion</strong><strong>with</strong> <strong>two</strong> <strong>jets</strong>. At hadron colliders the <strong>Higgs</strong> is produced copiously through gluonfusion, therefore amplitudes conta<strong>in</strong><strong>in</strong>g a <strong>Higgs</strong> and additional QCD radi<strong>at</strong>ion areimportant backgrounds to <strong>Higgs</strong> search channels such as vector <strong>boson</strong> fusion. Henceknowledge <strong>of</strong> these amplitudes <strong>at</strong> Next-to-Lead<strong>in</strong>g Order (NLO) <strong>in</strong> a perturb<strong>at</strong>iveexpansion <strong>in</strong> the strong coupl<strong>in</strong>g constant is an essential requirement for the LHCand Tev<strong>at</strong>ron. The NLO calcul<strong>at</strong>ion <strong>of</strong> <strong>Higgs</strong> plus <strong>two</strong> <strong>jets</strong> has previously beenperformed semi-numerically [104], however to improve the speed <strong>of</strong> the code analyticcalcul<strong>at</strong>ions <strong>of</strong> the amplitudes were desired.In obta<strong>in</strong><strong>in</strong>g compact analytic expressions for the various <strong>Higgs</strong> plus parton helicityamplitudes we used various ideas from the recent advances <strong>in</strong> on-shell techniques.These techniques use on-shell tree-level amplitudes to construct one-loopamplitudes. S<strong>in</strong>ce tree-level amplitudes are sums <strong>of</strong> Feynman diagrams, gauge cancell<strong>at</strong>ionsoccur <strong>at</strong> the beg<strong>in</strong>n<strong>in</strong>g <strong>of</strong> a calcul<strong>at</strong>ion r<strong>at</strong>her than <strong>at</strong> the end. Also thefactorial growth <strong>of</strong> the number <strong>of</strong> Feynman diagrams is severely curtailed lead<strong>in</strong>g toa polynomial growth <strong>in</strong> complexity <strong>with</strong> <strong>in</strong>creas<strong>in</strong>g multiplicities.The fundamental concept <strong>in</strong> generalised unitarity methods is th<strong>at</strong> <strong>of</strong> multiplecuts together <strong>with</strong> the use <strong>of</strong> complex momenta. Multiple cuts allow the isol<strong>at</strong>ion <strong>of</strong>specific coefficients which enter the one-loop basis expansion, result<strong>in</strong>g <strong>in</strong> simplific<strong>at</strong>ionsfrom the older double-cut analyses. Complex momenta are necessary so th<strong>at</strong>167