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Exploring New Physics in Electroweak Symmetry Breaking: Implications for TeV-scale Experiments

Delve into the physics of electroweak symmetry breaking and potential new physics at the TeV scale. Learn about the naturalness problem, dark matter, and weak scale supersymmetry. Discover how new theories offer motivations beyond the Standard Model and the significance of LHC and LC experiments. Uncover the intricacies of superparticle spectra, gauge coupling unification, and potential SUSY breaking mechanisms. Explore different approaches to addressing fine-tuning issues and considerations for a deeper level of physical theory.

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Exploring New Physics in Electroweak Symmetry Breaking: Implications for TeV-scale Experiments

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  1. New Developments in Physics of Electroweak Symmetry Breaking Yasunori Nomura UC Berkeley; LBNL

  2. What do we expect to see at TeV?  Physics of electroweak symmetry breaking Is there New Physics at TeV?  We don’t know Possible hints • Problem of Naturalness • Existence of the Dark Matter Good motivations for Physics beyond the SM May also be responsible for weak-Planck hierarchy … e.g. theory of radiative EWSB  Target of Next Experiments (LHC, LC, …)

  3. Naturalness Problem of the SM The SM Lagrangian is not stable under quantum corrections: VHiggs = mh2 |h|2 + l|h|4/4 We need “Experimentally’’ mh2 < O(100 GeV)2(v = 2mh2/l = 174 GeV) Naturalness: mh2 < O(100 GeV)2  m < O(TeV)

  4. What do we know about New Physics?  The SM describes physics at < O(100 GeV) extremely well Contributions from New Physics:  New Physics is (most likely) weakly coupled Weak scale supersymmetry Higgs as a pseudo Nambu-Goldstone boson ( ) M > a few TeV … opposite statistics … same statistics

  5. Weak Scale Supersymmetry Superparticle at the TeV scale Bosons Fermions Aml qq ll hh After SUSY breaking, l, q, l and h obtain masses of O(TeV)  Beautiful cancellation of dmh2 between contributions from the SM and superparticles R parity  the existence of Dark Matter ~ ~ ~ ~ ~ ~

  6. g3 Gauge coupling unification at a high scale: • nonSUSY • SUSY g2 g1 g3 g2 Munif ~ 1016 GeV g1

  7. ( ) Superparticle spectrum provides a window for a deeper level of physical theory • “Gravity’’ mediation • Gauge mediation • Anomaly mediation • …  Distinct spectra Combination of LHC and LC important LSP ~ DM: weakly interacting --- Exploration at LC Gaugino mediation, Moduli mediation, …

  8. Supersymmetry after the LEPII • “Minimal’’ Supersymmetry is fine-tuned … Supersymmetric fine-tuning problem • Minimization condition Natural EWSB requires In the MSSM, mh2 receives contribution from top-stop loop Mmess: the scale where suerparticle masses are generated

  9. What’s wrong? • MHiggs < MZ at tree level • need radiative corrections from top-stop loop • Tension with the other superparticle mass bounds • e.g.mediation by the SM gauge interactions e.g. mSUGRA

  10. Possible approaches • We don’t care • Higgs boson may be lighter Dermisek, Gunion; Chang, Fox, Weiner; …  LEPII may have missed the Higgs h0 because h0 decays into final states that are hard to detect • Higgs boson may be heavier Barbieri, Hall, Y.N., Rychkov; … … alleviates fine-tuning (in the most straightforward way)  We may have been misled in interpreting EWPT • Problem of SUSY breaking mechanism? Kitano, Y.N.; …  Some mechanism may be preferred over others • Environmental • Split SUSY Arkani-Hamed, Dimopoulos; Giudice, Romanino; … • Living dangerously Giudice, Rattazzi; …

  11. SUSY without a light Higgs boson • Heavier Higgs boson alleviates tuning VHiggs = mh2 |h|2 + l|h|4/4  v2 = |h|2 = -2mh2/l, MHiggs2 = lv2 In SUSY • Allowed by EWPT? (We imagine e.g. MHiggs ~ 200-300 GeV)

  12. Constraint on MHiggs on the S-T plane  easy to have large MHiggs if additional DT exist Maybe we are being fooled by DT|New Physics LEP EWWG

  13. lSUSY framework Barbieri, Hall, Y.N., Rychkov, hep-ph/0607332 • Higgs boson can be made heavy inSUSY by with (l perturbative up to ~10TeV) • Large l makesMHiggs heavy and at the same time induces sizable DT from singlet-doublet mixings! Parameter of the model: Scalar sector Fermion sector m12, m22, m32 tanb, mH+, v m, M in the limit of decoupling the S scalar and gauginos

  14. Contribution from the scalar Higgs sector • DT0 for tanb1 (custodial symmetry) • DT>0 can make large MHiggs consistent  tanb cannot be large also reinforced by the stop-sbottom contributions l=2 mH+=350,500,750 GeV

  15. Contribution from the Higgsino sector tanb < 3 preferred in lSUSY  rich Higgs physics at ~O(200-700 GeV) Blue – S Red – T Shaded region indicates

  16. New Possibility for Dark Matter In the limit of heavy gauginos, c = {yS, yHu, yHd} ccZff suppressed  c can be the dark matter tanb ~ 1.4 (detection promising: sSI > 10-44 cm2) Blue: WMAP region

  17. Harnik, Kribs, Larson, Murayama; Chang, Kilic, Mahbubani; Birkedal, Chacko, Y.N.; Delgado, Tait; … • Gauge Coupling Unification Compositeness of S, Hu, Hd and/or top can induce large l, keeping the desert • 5D realization/modeling  Gauge coupling unification can be preserved Higgs sector physics in supersymmetry can be quite rich – potential window for the DM sector Exploration at LC very useful Birkedal, Chacko, Y.N.

  18. Higgs as a pseudo Nambu-Goldstone boson Why mh << MPl ?  Higgs is a pseudo Nambu-Goldstone boson • Old composite models • Little Higgs models • Holographic Higgs models • Twin Higgs models • … Cancellation of dmh2 is between the same statistics fields– e.g. we have t’ instead of t Georgi, Kaplan; … Arkani-Hamed, Cohen, Georgi; … Contino, Y.N., Pomarol; … Chacko, Goh, Harnik; … ~

  19. Higgs as a holographic pseudo Nambu-Goldstone boson Contino, Y.N., Pomarol, hep-ph/0306259 Agashe, Contino, Pomarol, hep-ph/0412089 Technicolor: (LQCD ~ <qq>1/3 ~ 1 GeV gives fp ~ mW ~ 100 MeV) mW ~ 100 GeV  LTC ~ 1 TeV The scale of New Physics too close --- contradict with the precision electroweak data Pions in massless QCD: (mp± ~ 10 MeV with LQCD ~ 1 GeV) mh ~ 100 GeV  LNEW ~ 10 TeV Safer in terms of the precision electroweak data – LTC VEW LNEW VEW

  20. SU(2) • Basic structure (omitting details, e.g. U(1)Y assignment) SU(3)globalכ SU(2)L SSB: SU(3)global SU(2) produces PNGB which is SU(2)L doublet • Higgs compositeness is not enough • Analogy with QCD: “Yukawa’’ couplings suppressed because dim[On] (On=udd) is “large’’ = 9/2 Need interactions strong for a wide energy range to reduce dim[O]  CFT

  21. How to realize such theories? --- Gauge theory/gravity correspondence • Realization in 5D Higgs arises as an extra dimensional component of the gauge boson, A5 AdS (warped)

  22. Realistic Yukawa couplings obtained • Higgs potential is finite and calculable  EWSB (due to higher dimensional gauge invariance) • Existence of resonances (KK towers) for the gauge fields as well as quarks and leptons … Physics at the LHC (and LC) • Nontrivial wavefunctions for W and Z as well as for matter  couplings deviate from the SM … Physics at LC

  23. Summary • We are about to explore physics of EWSB • New Physics at the TeV scale is well motivated • Problem of Naturalness, DM, … • Weak scale supersymmetry • Higgs as a pseudo Nambu-Goldstone boson • … • Exploration of this New Physics is the prime target of experiments in the next decades A variety of possibilities for how New Physics shows up  Combination of the LHC and LC very useful • We hope to understand Nature at a deeper level

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