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Electroweak Baryogenesis: Electric dipole moments, the LHC, and the sign of the baryon asymmetry

Electroweak Baryogenesis: Electric dipole moments, the LHC, and the sign of the baryon asymmetry. Sean Tulin (Caltech). Collaborators: Daniel Chung Bjorn Garbrecht Michael Ramsey-Musolf (NPAC UW-Madison). Summary of this talk. Review electroweak baryogenesis Basic picture

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Electroweak Baryogenesis: Electric dipole moments, the LHC, and the sign of the baryon asymmetry

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  1. Electroweak Baryogenesis:Electric dipole moments, the LHC, and the sign of the baryon asymmetry Sean Tulin (Caltech) Collaborators: Daniel Chung Bjorn Garbrecht Michael Ramsey-Musolf (NPAC UW-Madison)

  2. Summary of this talk • Review electroweak baryogenesis • Basic picture • Requirements for it to work • EWB in the MSSM • What is needed • Sign of the baryon asymmetry Universe made of matter Sign of EDMs Stop/sbottom mass spectrum

  3. Supersymmetry is super-great! The minimal supersymmetric standard model (MSSM): + + Coupling unification Hierarchy problem Dark matter Stringy motivation

  4. Electroweak Baryogenesis Picture PDG Dunkley et al [WMAP5] We want to explain 95% C.L. based on dynamics during the electroweak phase transition. • Sakharov conditions: • Baryon number violation • C- and CP-violation • Departure from thermal equilibrium Electroweak sphalerons complex phases 1st order phase transition

  5. Electroweak Baryogenesis Picture First order electroweak phase transition during the early universe Higgs potential f = (f1, f2, ...) V( ) T > Tc T = Tc High T: EW symmetry restored from thermal corrections to Higgs potential Low T: EW symmetry broken T =0 At critical temp Tc, degenerate minima. Just below Tc, quantum tunneling from to bubble nucleation!

  6. CP Electroweak Baryogenesis Picture Cohen, Kaplan, Nelson, 1992-1994; Huet, Nelson, 1996 Three Steps: 1. Nucleation and expansion of bubbles of broken EW symmetry 2. CP-violating interactions at bubble wall induces charge density, diffusing outside bubble 3. Sphalerons convert LH asymmetry into B asymmetry moving bubble wall diffusion electroweak sphaleron Quark number density

  7. CP Electroweak Baryogenesis Picture Cohen, Kaplan, Nelson, 1992-1994; Huet, Nelson, 1996 Three Steps: 1. Nucleation and expansion of bubbles of broken EW symmetry 2. CP-violating interactions at bubble wall induces charge density, diffusing outside bubble 3. Sphalerons convert LH asymmetry into B asymmetry moving bubble wall 4. Baryon asymmetry captured by expanding bubble diffusion electroweak sphaleron Quark number density

  8. Requirements for electroweak baryogenesis to work Given a model of electroweak symmetry breaking (e.g. the standard model), what is required? • Two requirements: • Sufficient CP-violation to explain observed nB • A strong first-order electroweak phase transition Neither satisfied in the SM May be satisfied in the MSSM, or in extensions of MSSM (e.g. NMSSM) RH stop < 125 GeV, LH stop > 6.5 TeV (to avoid color-breaking phase transition) in MSSM Carena, Nardini, Quiros, Wagner, 2008

  9. electroweak baryogenesis requirements Requirement #1: sufficient CP-violation Need to have “sufficient” CP-violation to produce the observed baryon asymmetry • Solve Boltzmann equations for particles species in the plasma, with background of expanding bubble of broken EW symmetry ni = number density for particles — antiparticles diffusion collisions CP-violating source

  10. stolen from Bjorn Garbrecht

  11. electroweak baryogenesis requirements Requirement #1: sufficient CP-violation Need to have “sufficient” CP-violation to produce the observed baryon asymmetry • Solve Boltzmann equations for particles species in the plasma, with background of expanding bubble of broken EW symmetry ni = number density for particles — antiparticles diffusion collisions CP-violating source 2. Take left-handed fermion charge nL and compute baryon asymmetry collision factor weak sphaleron

  12. collision factor CP-violating source Baryon asymmetry • Magnitude of the baryon asymmetry depends on: • KC: depends on large fraction of MSSM spectrum • CP-violating source: depends on only a few parameters, but still much theoretical uncertainty • 2. Sign of baryon asymmetry • Depends on CP-violating phase and relatively few other parameters

  13. Collision factor What interactions in the plasma are in chemical equilibrium? (i.e. fast compared to diffusion time scale) • Previous lore: • Gauge/gaugino interactions • Top yukawa interactions • Strong sphalerons Cohen, Kaplan, Nelson, 1992-1994; Huet, Nelson, 1996 tL nL left-handed fermion density ~ tR diffusion tL ~ tR

  14. Collision factor What interactions in the plasma are in chemical equilibrium? (i.e. fast compared to diffusion time scale) • Previous lore: • Gauge/gaugino interactions • Top yukawa interactions • Strong sphalerons Cohen, Kaplan, Nelson, 1992-1994; Huet, Nelson, 1996 Cirigliano, Lee, Ramsey-Musolf, S.T. (2006) Next, use ni = kimi Then can express nL = KC nH where KC given in terms of ki’s ~

  15. Collision factor What interactions in the plasma are in chemical equilibrium? (i.e. fast compared to diffusion time scale) • Previous lore: • Gauge/gaugino interactions • Top yukawa interactions • Strong sphalerons Cohen, Kaplan, Nelson, 1992-1994; Huet, Nelson, 1996 Cirigliano, Lee, Ramsey-Musolf, S.T. (2006) New Results: 4. Bottom yukawa interactions 5. Tau yukawa interactions (lepton-driven EWB) Chung, Garbrecht, Ramsey-Musolf, S.T. (2008)

  16. Collision factor When are bottom Yukawa interactions important? Time scale for bottom Yukawa interactions vs. diffusion time scale only Chung, Garbrecht, Ramsey-Musolf, S.T. (in prep)

  17. KC = 0 for KC < 0 for KC > 0 for Collision factor With bottom Yukawa interactions, KC simplifies greatly: ~ nL = KC nH Conversion factor for Higgsinos into LH quarks (3rd gen) ki = ki(mi/T) largest for small mi Sign of KC (and, in part, nB) determined by whether RH stop or sbottom is lighter Chung, Garbrecht, Ramsey-Musolf, S.T. (2008) Also, KC -> 0 for

  18. Collision factor With bottom Yukawa interactions, KC simplifies greatly: ~ nL = KC nH Physical reason for this effect Which effect wins depends on which degrees of freedom are lighter Chung, Garbrecht, Ramsey-Musolf, S.T. (2008)

  19. Stop at the LHC * Focus on case where RH stop < 120 GeV (i.e. MSSM) p p Good: Light stop means large production cross section Decay products: (assume m < 120 GeV) 1. stable (on collider time scales) CHAMP searches imply CDF 2007 2. only if 115 GeV

  20. Stop at the LHC * Light RH stop at the LHC p p Good: Light stop means large production cross section Decay products: (assume m < 120 GeV) Hikasa, Kobayashi (1987) Hiller, Nir (2008) tends to dominate for 3. 4.

  21. Stop at the LHC * Light RH stop at the LHC p p Good: Light stop means large production cross section Bad: Difficult to observe at LHC! Missing energy c g/g Better: radiative decay (signal: missing energy + high pT jet or photon) Low energy QCD (~50 GeV) Carena, Freitas, Wagner (2008)

  22. Stop at the LHC Light RH stop at the LHC Carena, Freitas, Wagner (2008) Radiative stop decay: “LSP” Signal: high PT jet + ET + soft charm jets (tough) Light stop window for strong 1st order phase transition dominant

  23. collision factor CP-violating source Baryon asymmetry CP-violating source: Two-flavor oscillation problem (a la neutrino oscillations) but with a spacetime dependent Hamiltonian mass matrix What parameters govern the sign of the CP-violating source? relevant phases

  24. CP-violating source Various results: plotted vs. m, for M2 = 200 GeV Carena, Quiros, Seco, Wagner (2000) Lee, Cirigliano, Ramsey-Musolf (2004) and Konstandin, Prokopec, Schmidt, Seco (2005) Carena, Moreno, Quiros, Seco, Wagner (2002)

  25. CP-violating source How does an expanding bubble of broken EW symmetry produce a CP-asymmetry of particles vs antiparticles? Full treatment requires non-equilibrium, finite temp field theory Quick & dirty explanation: (using elementary QM) Two-flavor oscillation problem (a la neutrino oscillations) but with a spacetime dependent Hamiltonian H(t) V(t) V(t)* particles anti-particles V(t) rotates flavor states into mass eigenstates (Consider simplified case where Hamiltonian only depends on t)

  26. CP-violating source Evolution of states: flavor states Schrödinger Eqn: (flavor basis) a, b = L, R Then rotate to mass basis Schrödinger Eqn is now where Similarly for anti-particle states

  27. Initial condition: Begin with plasma in equilibrium: ensemble of mass basis states with weight CP-violating source Evolution of states: Amplitude for mass state |j> to be in flavor state |a> after time t CP-violating source:

  28. CP-violating source CP-violating source: where • Conclusions: • Need two nearly degenerate states — otherwise small q and source washed out by oscillations • Need spacetime-dependent phase in mixing matrix • States not too heavy compared to temp T — otherwise Boltzmann suppressed

  29. CP-violating source Example: CP-violating source from Higgsino/Wino oscillations. Flavor states

  30. CP-violating source Various results: plotted vs. m, for M2 = 200 GeV Carena, Quiros, Seco, Wagner (2000) Lee, Cirigliano, Ramsey-Musolf (2004) and Konstandin, Prokopec, Schmidt, Seco (2005) Carena, Moreno, Quiros, Seco, Wagner (2002)

  31. Implications for EDMs • Suppose EDM measured. What are implications for EWB? • Assume same phase for both baryon asymmetry and EDM • Assume one-loop EDMs suppressed (heavy 1st/2nd gen sfermions) Two-loop EDMs are irreducible: Two possible CP-violating phases that could drive baryogenesis in MSSM also give rise to EDMs Recently computed in full by Li et al (2008)

  32. CP-violating phase Sign of two-loop EDMs mostly correlated wrt CP-violating phases! positive contributions negative contributions Li, Profumo, Ramsey-Musolf (2008)

  33. Current EDM constraints electron EDM neutron EDM Excluded Li et al (2008)

  34. Future EDM searches Very exciting! Future EDM measurements will improve sensitivities by orders of magnitude.

  35. Future EDM constraints electron EDM neutron EDM Excluded Baryogenesis curves made with most optimistic estimates dn < 1x10-28 e cm de < 3x10-30 e cm Li et al (2008)

  36. Conclusions Sign of baryon asymmetry may be the easiest consistency check for electroweak baryogenesis in the MSSM • Under simplest assumptions (EDM and EWB determined by same phase), sign of baryon asymmetry determined by: • Collision factor KC: depends on whether RH stop or sbottom is heavier • Sin of CP-violating phase Generalization beyond the MSSM? same collision factor unknown if EDMs correlate with CP-violating phase

  37. CP-violating source nH ~ nH ~ Konstandin et al (2005) Cirigliano, Lee, Ramsey-Musolf, S.T. (2006) nB/s = 3 x (nB/s)WMAP x sin fM2m nB/s = 30 x (nB/s)WMAP x sin fM2m Discrepency in treatment of diffusion

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