Standard Model & Baryogenesis at 50 Years
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Standard Model & Baryogenesis at 50 Years Rocky Kolb The University of Chicago The Standard Model and Baryogenesis at 50 Years 1967 For the universe to evolve from B = 0 to B ¹ 0, requires: 1. Baryon number violation 2. C and CP violation 3. Departure from thermal equilibrium The Standard Model and Baryogenesis at 50 Years 95% of the Mass/Energy of the Universe is Mysterious The Standard Model and Baryogenesis at 50 Years 95% of the Mass/Energy of the Universe is Mysterious Baryon Asymmetry Baryon Asymmetry Baryon Asymmetry The Standard Model and Baryogenesis at 50 Years 99.825% of the Mass/Energy of the Universe is Mysterious The Standard Model and Baryogenesis at 50 Years Ω 2 = 0.02230 ± 0.00014 CMB (Planck 2015): B h Increasing baryon component in baryon-photon fluid: • Reduces sound speed. −1 c 3 ρ c =+1 B S ρ 3 4 γ • Decreases size of sound horizon. η rdc()η = ηη′′ ( ) SS0 • Peaks moves to smaller angular scales (larger k, larger l). = π knrPEAKS S • Baryon loading increases compression peaks, lowers rarefaction peaks. Wayne Hu The Standard Model and Baryogenesis at 50 Years 0.021 ≤ Ω 2 ≤0.024 BBN (PDG 2016): B h Increasing baryon component in baryon-photon fluid: • Increases baryon-to-photon ratio η. • In NSE abundance of species proportional to η A−1. • D, 3He, 3H build up slightly earlier leading to more 4He. • Amount of D, 3He, 3H left unburnt decreases. Discrepancy is fake news The Standard Model and Baryogenesis at 50 Years = (0.861 ± 0.005) × 10 −10 Baryon Asymmetry: nB/s • Why is there an asymmetry between matter and antimatter? o Initial (anthropic?) conditions: . Requires “acausal” initial conditions. Inflation, which seemingly evades acausal issue for density perturbations, dilutes pre-inflation baryon number by an exponential amount. o The modern perspective is that reheating after inflation produced a symmetric universe (equal abundances of matter & antimatter). o Asymmetry developed dynamically after inflation and reheating through a process known as “baryogenesis.” • Why is it about 10−10 ? The Standard Model and Baryogenesis at 50 Years Inner Space/Outer Space Connection A complete Standard Model of Particle Physics, arising from laboratory experiments and beautiful theoretical ideas, should be applicable to the universe beyond terrestrial laboratories and (in principle) allow the calculation of cosmological parameters such as the baryon number of the universe. A failure of today’s Standard Model of Particle Physics to account completely for the observed universe (dark matter, dark energy, inflation, baryogenesis) points to the fact that Today’s Standard Model of Particle Physics is not the Final Standard Model of Particle Physics. Cosmological considerations may point to directions for physics beyond today’s Standard Model. The baryon asymmetry is an example of this. The Standard Model and Baryogenesis at 50 Years = (0.861 ± 0.005) × 10 −10 Baryon Asymmetry: nB/s • Can the standard model of particle physics explain a tiny number = (0.861±0.005) × 10 −10 in the standard model of cosmology: nB/s ? No, or at least, not yet! • Can the standard model of particle physics explain an order-unity number in the standard model of cosmology: Dark Matter/Baryons ≈ 5.3? No, or at least, not yet! • Starting after inflation/reheating with a symmetric universe, how must the SM be augmented to produce an asymmetric universe? The Standard Model and Baryogenesis at 50 Years Many, Many Models for Baryogenesis To be discussed: Other possibilities: Electroweak Baryogenesis Baryogenesis from Thermal Leptogenesis • Primordial Cosmic Strings GUT Baryogenesis • Primordial Magnetic Fields Affleck-Dine Baryogenesis • Primordial Black Holes Spontaneous Baryogenesis Dissipative Baryogenesis Warm Baryogenesis Cloistered Baryogenesis Cold Baryogenesis Planck Baryogenesis Post-Sphaleron Baryogenesis WIMPy Baryogenesis Dirac Leptogenesis Resonant Leptogenesis Non-Local Electroweak Baryogenesis Magnetic-Assisted EW Baryogenesis Singlet-Assisted EW Baryogenesis Varying Constants Driven Baryogenesis . The Standard Model and Baryogenesis at 50 Years Sakharov Criteria in the Standard Model ˆˆ≠ 1. Baryon number violating processes BH ,0 : 2. C and CP violating processes: 3. Nonequilibrium conditions: The Standard Model and Baryogenesis at 50 Years Sakharov Criteria in the Standard Model ˆˆ≠ 1. Baryon number violating processes BH ,0 : Zero temperature: ’t Hooft Yes in SM Γ ∝ e −16π 2/g2 ≈ 10−171 (nonperturbatively) Non-zero temperature: Klinkhamer & Manton Conserves B − L 3 −E ()TT Γ∝()α 4 sph h ≠0 MTMeWW W 〈 〉 Γ∝()α 4 〈h〉 =0 WT 2. C and CP violating processes: 3. Nonequilibrium conditions: The Standard Model and Baryogenesis at 50 Years Sakharov Criteria in the Standard Model ˆˆ≠ 1. Baryon number violating processes BH ,0 : Zero temperature: ’t Hooft Yes in SM Γ ∝ e −16π 2/g2 ≈ 10−171 (nonperturbatively) Non-zero temperature: Klinkhamer & Manton Conserves B − L 3 −E ()TT Γ∝()α 4 sph h ≠0 MTMeWW W 〈 〉 Γ∝()α 4 〈h〉 =0 WT 2. C and CP violating processes: Yes in SM But Jarlskog invariant very small: ∝ 2− 2 2− 2 2− 2 2− 2 2− 2 2− 2 ×2 Direct CP violation CP (mt mc ) (mt mu ) (mc mu ) (mb ms ) (mb md ) (ms md ) J 2 (CKM) J = c12 c13 c23 s12 s13 s23 sinδ 3. Nonequilibrium conditions: The Standard Model and Baryogenesis at 50 Years Sakharov Criteria in the Standard Model ˆˆ≠ 1. Baryon number violating processes BH ,0 : Zero temperature: ’t Hooft Yes in SM Γ ∝ e −16π 2/g2 ≈ 10−171 (nonperturbatively) Non-zero temperature: Klinkhamer & Manton Conserves B − L 3 −E ()TT Γ∝()α 4 sph h ≠0 MTMeWW W 〈 〉 Γ∝()α 4 〈h〉 =0 WT 2. C and CP violating processes: Yes in SM But Jarlskog invariant very small: ∝ 2− 2 2− 2 2− 2 2− 2 2− 2 2− 2 ×2 Direct CP violation CP (mt mc ) (mt mu ) (mc mu ) (mb ms ) (mb md ) (ms md ) J 2 (CKM) J = c12 c13 c23 s12 s13 s23 sinδ 3. Nonequilibrium conditions: Dimopoulos & Susskind − BTrBTrCPTCPTBˆˆ==ee−−ββHHˆˆ()() 1 ˆ T ˆ −1 CPT conserved ==−Tre−β H ()() CPT Bˆˆ CPT B T ˆ = CPT,H 0 The Standard Model and Baryogenesis at 50 Years Sakharov Criteria in the Standard Model ˆˆ≠ 1. Baryon number violating processes BH ,0 : Zero temperature: ’t Hooft Yes in SM Γ ∝ e −16π 2/g2 ≈ 10−171 (nonperturbatively) Non-zero temperature: Klinkhamer & Manton Conserves B − L 3 −E ()TT Γ∝()α 4 sph h ≠0 MTMeWW W 〈 〉 Γ∝()α 4 〈h〉 =0 WT 2. C and CP violating processes: Yes in SM But Jarlskog invariant very small: ∝ 2− 2 2− 2 2− 2 2− 2 2− 2 2− 2 ×2 Direct CP violation CP (mt mc ) (mt mu ) (mc mu ) (mb ms ) (mb md ) (ms md ) J 2 (CKM) J = c12 c13 c23 s12 s13 s23 sinδ 3. Nonequilibrium conditions: Dimopoulos & Susskind − BTrBTrCPTCPTBˆˆ==ee−−ββHHˆˆ()() 1 ˆ No in SM and T ˆ −1 CPT conserved standard cosmology ==−Tre−β H ()() CPT Bˆˆ CPT B T ˆ = CPT,H 0 The Standard Model and Baryogenesis at 50 Years Electroweak Baryogenesis Kuzmin, Rubakov, Shapashnikov; Cohen, Kaplan, Nelson The baryon asymmetry is generated at the electroweak phase transition from the seed of CP-violating interactions of particles scattering at the Higgs-field bubble wall. Primordial Assume 1st-order EWK phase transition: nucleate 〈h〉 =0 Plasma broken-phase bubble in symmetric phase background (phase coexistence → nonequilibrium conditions). 〈h〉 =0 〈h〉 ≠0 〈h〉 =0 Broken phase expands into unbroken phase. In broken phase sphalerons suppressed exp(−E /T), sph 〈h〉 =0 while in symmetric phase sphalerons unsuppressed. VWall 〈h〉 ≠0 〈h〉 =0 ΔB H ΔB H h The Standard Model and Baryogenesis at 50 Years Electroweak Baryogenesis Kuzmin, Rubakov, Shapashnikov; Cohen, Kaplan, Nelson The baryon asymmetry is generated at the electroweak phase transition from the seed of CP-violating interactions of particles scattering at the Higgs-field bubble wall. Primordial Assume 1st-order EWK phase transition: nucleate 〈h〉 =0 Plasma broken-phase bubble in symmetric phase background (phase coexistence → nonequilibrium conditions). 〈h〉 =0 〈h〉 ≠0 〈h〉 =0 Broken phase expands into unbroken phase. In broken phase sphalerons suppressed exp(−E /T), sph 〈h〉 =0 while in symmetric phase sphalerons unsuppressed. V Wall 1. If CP in Higgs/fermion interactions, different 〈h〉 ≠0 〈h〉 =0 transmission & reflection of left & right- ΔB H ΔB H handed quarks at the wall leads to CP asymmetry at wall. h CP The Standard Model and Baryogenesis at 50 Years Electroweak Baryogenesis Kuzmin, Rubakov, Shapashnikov; Cohen, Kaplan, Nelson The baryon asymmetry is generated at the electroweak phase transition from the seed of CP-violating interactions of particles scattering at the Higgs-field bubble wall. Primordial Assume 1st-order EWK phase transition: nucleate 〈h〉 =0 Plasma broken-phase bubble in symmetric phase background (phase coexistence → nonequilibrium conditions). 〈h〉 =0 〈h〉 ≠0 〈h〉 =0 Broken phase expands into unbroken phase. In broken phase sphalerons suppressed exp(−E /T), sph 〈h〉 =0 while in symmetric phase sphalerons unsuppressed. V Wall 1. If CP in Higgs/fermion interactions, different 〈h〉 ≠0 〈h〉 =0 transmission & reflection of left & right- ΔB H ΔB H handed quarks at the wall leads to CP asymmetry at wall. h 2. Sphalerons violate B, they interact with qL (not qR) CP asymmetry converted to baryon asymmetry in front of wall. CP 3. Baryon asymmetry diffuses into broken phase across wall. B The Standard Model and Baryogenesis at 50 Years Electroweak Baryogenesis Problems: 1. Phase transition not 1st-order in the Standard Model (Higgs mass too large; need 72 mh GeV). 2.CP too small in the Standard Model (Jarlskog invariant small; n, nuclei EDM). →1 3. Wall velocity may be too large. As Vwall , wall moves too fast for baryon asymmetry to diffuse into broken-phase bubbles. Bad News: Electroweak baryogenesis doesn’t work within the Standard Model.