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What can we learn about new physics without having observed new particles

This article discusses the insights gained from various measurements in the field of particle physics, including the discovery of the top quark and the Higgs boson. It explores the implications of these discoveries for the stability of the Standard Model, the precision on top quark and electroweak masses, and the possibility of modifying Higgs couplings. The article also examines the impact of supersymmetry on tree-level couplings and the potential for observing sparticles at the LHC. Overall, the article emphasizes the importance of high-precision measurements in uncovering new physics at the GUT scale.

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What can we learn about new physics without having observed new particles

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  1. What can we learn about new physics without having observed new particles Snowmass on the Mississippi Minneapolis-St. Paul July 31, 2013 Dirk Zerwas LAL Orsay EW fit: combining many measurements! LEP, SLC, Tevatron,…aka: EW-factories  • top quark discovered at the TeVatron • EW fit compatible (radiative corrections under control) • Higgs should be light (less than order 200GeV) • ATLAS and CMS (plus TeVatron) discovered and measured 126GeV • other example: Z interference in e+e- at sqrt(s) << 91GeV

  2. Learning from the top and the Higgs S.Heinemeyer, W. Hollik, D. Stockinger, G. Weiglein, L. Zeune ’12 • Stable Standard Model? Up to which scale? • RGE(scale)  precision on the top quark mass • Standard model or supersymmetry? • precision on top quark mass • precision electroweak mass W • Electroweak fit  Higgs couplings fit? • similar problematic: observables are σ*Br (LHC, ILC) and σ • Br = f(all couplings) • Two options to modify Higgs couplings: • mixing (e.g., portal, supersymmetry) • adding new particles in the loop diagrams (Hgg, Hγγ), vertex corrections, e.g. supersymmetry • Example: a simple 2-parameter model: • dark sector with a dark Higgs mixing with the “standard” Higgs • cos2χ: governs mixing • (Γhidinvisible Higgs decays to the dark sector) • Global factor cos χ: • 1+Δ with Δ = vev2/Λ2 (operator expansion motivated) • 1% precision corresponds to 2.5TeV Gupta, Rzehak, Wells, Phys.Rev. D86 (2012) 095001

  3. Higgs and invisible Supersymmetry SUSY affects the tree-level couplings: decoupling limit  presented by Sally Dawson, Heather Logan, … Tim Barklow… Europhys.Lett. 101 (2013) 51001 • which depend on unobserved sparticles: • stops via: Rt (stop/top loops) • pseudoscalar Higgs boson A • LHC+ILC combined analysis: • LHCILC % level and better • model independent determination

  4. Visible Supersymmetry • What if we see sparticles at the LHC? • does the measurement tell us something beyond TeV scale? Eur.Phys.J. C71 (2011) 1520 • Evolve SUSY parameters to GUT scale: • close miss • or unification • precision is necessary • measuring unification! Essential to put all frontiers together: Energy, Intensity (g-2), Cosmology, theory, precision e.g., to get a coherent picture… Buchmueller et al, Eur.Phys.J. C72 (2012) 2243

  5. Precise measurements: • top quark, W boson, Higgs boson • will it lead to a consistent picture? • The Higgs couplings: • sensitivity to unobserved new particles • precision is the key! • putting together all frontiers is necessary The perennial optimist’s take: high precision will tell us something about the GUT scale

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