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Z’ models Proposal for Grenoble contribution to section 4 of CSC note

28 September 2006. Z’ models Proposal for Grenoble contribution to section 4 of CSC note. Fabienne LEDROIT Julien MOREL Benjamin TROCME ATLAS Exotic group. Today, we are interested in the part labeled “ Heavy gauge bosons ”. We study Z’ coming from : Grand Unified Theories (GUT)

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Z’ models Proposal for Grenoble contribution to section 4 of CSC note

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  1. 28 September 2006 Z’ modelsProposal for Grenoble contribution to section 4 of CSC note Fabienne LEDROIT Julien MOREL Benjamin TROCME ATLAS Exotic group

  2. Today, we are interested in the part labeled “Heavy gauge bosons” • We study Z’ coming from : • Grand Unified Theories (GUT) • Using the CDDT parameterization • Little Higgs • Extra-dimensions • For the computation of the ATLAS discovery potential : • We propose a model-independent method to take into account the detector efficiency

  3. GUT – CDDT parameterization Phys. Rev. D70, 093009 (2004) What is the model ? Used in TeV4LHC Report hep-ph/0608322 • A model independent parametrization : • based on the existence of one additional U(1) gauge group • describes Z’ from different GUT models The different Z’ are described by one of these four classes : For example Z’y, Z’h, Z’c from the E6 models are contained in What is the Z’ ? Constraints Each Z’ is described by 3 free parameters : • Z-Z’ mixing small (LEP) • Flavour changing neutral currents constraints • No Z’ decay into new particles • Anomaly cancellations • The Z’ mass • A coupling strength normalisation gZ’ • An x parameter (fermions coupling related)

  4. Little Higgs model ATL-PHYS-CONF-2006-007 (2006) What is the model ? An effective model adressing the hierarchy and the fine-tunnig problem : • Larger symmetry broken at high scale : SU(5)  SO(5) at LS~ few TeV • At the same time : SU(2)1×U(1)1× SU(2)2×U(1)2 SU(5)  SU(2)L×U(1)Y Produce new heavy gauge bosonsZH,WH, AH • Introduce heavy top T, heavy Higgs f Higgs is a pseudo-Goldstone boson Constraints What is the Z’ ? • WH , ZH comes from SU(2)2×U(1)2 • Quadratic divergences cancels thank to the new bosons loops • EW fits gives strong constraints • Littlest Higgs model already excluded by LEP without T-parity • ZH is fully describe by: • its mass • a mixing angle q !! • WH , ZH are mass degenerated !! • ZHe+e- forbidden in case of T-parity

  5. Extra-dimensions theories ADD like model Already studied in ATL-PHYS-PUB-2005-010(DC1) What is the model ? Not official Hep-ph/0602155(2006) RS with bulk matter Planck Brane TeV Brane • 5-Dim bulk with warped geometry. • New interpretation of the fermion mass hierarchy. • Compatible with a Grand Unified Theory • [hep-th/0108115] . • KK excitation provides WIMP. t H u fermions W G g Z γ What is the Z’ ? Constraints • SM charged Fermions masses and mixing angles • SM neutrino masses and mixing angles • Flavor Changing Neutral Current • S and T parameters • Z’ is the first Z/g KK excitations • Z’ and g’ are mass degenerated • The Z’ gauge coupling are non universal

  6. Z’ Generators Grand Unified Theories and little Higgs theory • We use standard Pythia with process n°141 (g / Z / Z’), for this we need : • The Z’ mass • The Z’ couplings See : Hep-ph/0301040 for the coupling of the little Higgs theory FERMILAB-FN-0773-Efor a good summary on the coupling for the CDDT parametrization Extra-dimension theories ADD like : We use Pythia with an user-defined process developed by G.Azuelos and G.Polesello RS like : We use Pythia with an user-defined process developed with G.Moreau These user-defined processes provide Z’ calculation with full interference Z/Z(1)/Z(2)/g/g(1)/g(2)

  7. A model-independent method to take into account the efficiency The efficiency depends on the model due to the Z’ boost dileptons coming from are more boosted than dileptons coming from because of different pdfs. Y Z ' SSM The detector efficiency depends on the Z’ boost 1 model-dependent combination (different couplings) Z’ rapidity model-independent shapes

  8. A model-independent method to take into account the efficiency Selection efficiency vs dielectron mass For and events separately • All models compatiblefor a given parton flavour • Efficiency only depends on initial parton flavour (for a given mass) To take into account the detector efficiency • We use full simulation for one sample to compute the model-independent detector efficiency. • For the other samples, we assign the right efficiency depending on the initial parton flavour and the invariant mass, event by event.

  9. Summary • We study Z’ from different kinds of models • Grand Unified Theories Model independent parameterization • Little Higgs theory ADD like RS like • Extra-Dimension theories • To compute the ATLAS discovery potential • We use a model independent method to take into account the detector efficiency (as in TeV4LHC Report hep-ph/0608322) • This way, we don’t need full simulation for all the models (at LO)

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