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  3 4 ργ • Decreases size of sound horizon. η rdc()η = ηη′′ ( ) SS0 • 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 ==−Tre− Hβ 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 ==−Tre− Hβ 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.

Good News: May point to directions BSM.

The Standard Model and Baryogenesis at 50 Years Electroweak Baryogenesis

How far BSM to have EWK phase transition 1st-order?

• MSSM initially promising if light right-handed stop (Carena, Quiros, Wagner; Cline & Moore). But increasingly stringent LHC constraints challenge the idea.

• NMSSM is more promising since extra singlet scalar field strengthens phase transition (Menon, Morrissey, Wagner; Huber, Konstandin, Prokopec, Schmidt).

• Two-Higgs models hard to make work since models that might work have very large Higgs self-coupling (Cline, Kainulainen, Trott).

• Most promising (and simplest) is to add a scalar singlet S coupling to Higgs Φ, e.g., 2 2 2 V(Φ,S) = μ S + ζ Φ†Φ S to provide cubic term (Choi & Volkas). 1 32 Δ=−+VTh(), π T()μς22 h 12 Two phase transitions since typically 〈S〉¹ 0.

• Lots of work probing models for 1st-order phase transitions at LHC & future colliders.

•1st-order phase transitions can lead to gravitational waves.

The Standard Model and Baryogenesis at 50 Years Electroweak Baryogenesis

Probe of models with 1st-order phase transitions (Huang, Long, Wang).

/2 < Φ†Φ real scalar singlet S (mH mS  TeV) interacting with SM through Higgs portal V(S) = S 2 + S 3 + S 4 + Φ†Φ S 2 + Φ†Φ S

Points represent models with 1st-order phase transition orange = too weak for baryogenesis Many models with detectable blue = viable baryogenesis Δ( ) also result in eLISA red = viable baryogenesis + detectable GWs hZZ gravitational wave signal.

eLISA (launch 2034) ,SM hZZ g / hZZ g 1 −

/ ghhh ghhh,SM (Huang, Long, Wang) The Standard Model and Baryogenesis at 50 Years (Huang, Long, Wang) Electroweak Baryogenesis

Probe of models with 1st-order phase transitions (Huang, Long, Wang).

• Same qualitative results for other models • 2 discrete symmetry S →−S and 〈S〉 = 0. • Scalar doublet (squark-like). • New fermions rather than scalars.

• Significant deviations in hZZ-coupling, large (1) deviation in hhh-coupling. Discoverable at future colliders.

• Very strong 1st-order transitions lead to detectable gravitational waves.

• Gravitational waves produced by o Collision of bubbles, o Decay of magnetohydrodynamic turbulence, o Propagation of sound waves.

The Standard Model and Baryogenesis at 50 Years Electroweak Baryogenesis

How far BSM to have CP sufficiently large?

•CP phase in MSSM chargino mass matrix leads to chiral chargino asymmetry → chiral quark asymmetry (Carena, Quiros, Riotto, Vilja, Wagner; Cline, Joyce, Kainulainen). But increasingly stringent LHC constraints, as well as EDM constraints are a problem.

• NMSSM is more promising, extra singlet provides new sources of CP .

• Ditto for non-SM singlets.

• Multi-Higgs models.

The Standard Model and Baryogenesis at 50 Years Electroweak Baryogenesis

• Doesn’t work in Standard Model, but ingredients in place.

• Need another source of CP evading FCNC, EDM, and other constraints.

st /2 < • To have phase transition 1 -order, couple light-ish (mH m  TeV) fields to Higgs. o Induces non-SM hhh and hZZ couplings which can be probed at colliders. o Sufficiently strong 1st-order transition could produce gravitational waves detectable by eLISA.

• Many aspects of calculation difficult (wall velocity, transport equations across wall, gravitational wave production, etc.).

The Standard Model and Baryogenesis at 50 Years Thermal Leptogenesis (Fukugita & Yanagida)

• Type-I see-saw model (Gell-Mann, Ramond & Slansky; Yanagida; Mohapatra & Senjanovic; Schecter & Valle) for neutrino masses and mixing enlarges the SM to include a Majorana neutrino N with a large mass which couples to SM leptons and Higgs via  = − λ LH N.

• Large Majorana mass for N; small Dirac mass for ν (generated by EWK Higgs mechanism). The see-saw results in light neutrino mass of ≈ 0.3 λ 0.1 2 1012 2 → ≈1012 mν eV ( / ) ( GeV /mN) so want mN GeV.

• N decays to SM leptons + Higgs, violating lepton number by 1: _ _ N → L H or N → L H Lepton-number violation. _ _ • Assume Γ(N → L H ) > Γ(N → L H ) CP violation.

• If nonequilibrium conditions, can generate a lepton asymmetry with B − L ¹ 0.

• Sphalerons destroy B + L at T  100 GeV, conserve B − L always. 11 •B =++−()BL() BL If start with initial L ¹ 0 & B = 0, end with B = − L / 2. 22 i i f i =−28 / 79 0 (Actually Bf Li Harvey & Turner.)

The Standard Model and Baryogenesis at 50 Years Thermal Leptogenesis CP violation

• Require interference between tree amplitude and loop corrections, e.g., λ∗ H kl H

N × N1 1 λ λ 1j 1k λ lj Lj Lj

• Lepton number generated in decay proportional to CP parameterε1:

2 2 MM− → NlH→ NlH1 312 M 3M m ελλ≡=1 Im ()† 1 ≤13 1 2  i1 2 16† = M 16 M → ()i 2,3 i h N1 all 11

CP violation expressed in terms of microphysics ππ λλ ≈10−2 • If completely out of equilibrium (only drift and decay) nB/s ε1

The Standard Model and Baryogenesis at 50 Years Thermal Leptogenesis Nonequilibrium conditions

1. N decay products thermalize; if temperature large enough can washout lepton number through processes like:

H ΔL = 1 N ΔL = 1 t H ΔL = 2 H N H N _ _ L L t LL _ _ Inverse decay, H L → N 2 « 2 scattering, NL ↔ t t 2 « 2 scattering, H L ↔ H L

2. Efficiency of washout depends on competition between reaction rates (function of ≈ 2 / model parameters and T ) and expansion rate H T MPl.

3. Rates are ≈ exp(−Μ1/Τ )

eq Γ eq () 3 nMT()/ Δ=±L 1 Tm nMTN 1 / Δ=±L 22T N1 1 Γ=DECAY t 1 Γ= Γ=Γ ↔ 22↔ mν INVERSE DECAY DECAY eq 22 2 2 eq 2 4  i 1 γ n π h ie= ,,μτ nL π h L mM 2 M Γ=11 1 DECAY mmm<< 8π h 2 E 113

The Standard Model and Baryogenesis at 50 Years Thermal Leptogenesis Nonequilibrium conditions

4. Interesting constraints on neutrino-sector parameters: 10−3 << o Condition for M1 to decay out-of-equilibrium: m  1  eV ( mmm 113  ).

2 o Bound on r.m.s. neutrino mass to avoid ΔL = 2 washout: m ν ≤ 0.3 eV . μτ i ie= ,,

The Standard Model and Baryogenesis at 50 Years Thermal Leptogenesis

• Leptogenesis is BSM, but motivated by observation of neutrino oscillations (and masses). Also massive right-handed N fermions present in Grand Unified Theories beyond SU(5), e.g., SO(10).

• Scenario has all the necessary ingredients: L violation from N decay followed by B violation from sphaleron conversion to B asymmetry; CP violation from complex Yukawa couplings; out-of-equilibrium decay for reasonable model parameters.

• Experimental proof of Majorana nature of neutrinos would give a boost to scenario.

• Inner-Space/Outer-Space connection between Baryon Asymmetry (one number) and the richness of the Type-I see-saw model.

The Standard Model and Baryogenesis at 50 Years GUT Baryogenesis

• Explosion of interest shortly after in late 1970s, after Georgi-Glashow 1974 SU(5) paper. o Yoshimura (1978) used only 2 « 2 processes; no departure from equilibrium. Doesn’t work. o Toussaint, Trieman, Wilczek, Zee (1979) and Barr (1979) pointed out problem. Dimopoulos & Susskind (1979) used out-of-equilibrium decay. Weinberg (1979), and later Yoshimura (1979), made quantitative calculations based on out-of- equilibrium decay. o Full Boltzmann reaction network including inverse decays and 2 « 2 processes by Kolb & Wolfram (1979) and Fry, Olive, Turner (1980). o Applications to SU(5) and SO(10) by Harvey, Kolb, Reiss, Wolfram in 1982.

• Grand Unified Theories are BSM, but embrace the theoretical underpinnings of the Standard Model (spontaneously broken gauge theories, fundamental quarks and leptons, etc.). o Ratio of energy scales may not be the most useful metric to measure how far “Beyond the Standard Model.”

The Standard Model and Baryogenesis at 50 Years GUT Baryogenesis

• Theoretical motivation to unify strong with electroweak interactions.

• Expected unification at a mass scale of 1014 – 1016 GeV.

5 ⊃ 3 ⊗ 2 ⊗ 1 24 • SU( ) SU( _)C SU( )L U( )Y . Gauge bosons in V representation. 5 + 10 Fermions in f f . Higgs in 5H .

• Coupling of fermions to gauge & Higgs: =⋅⋅+⋅+⋅⋅+⋅⋅λλ  g 24Vff 5 5 10 ff 10 UHffDHff 5 10 10 5 5 10 •B in decays of supermassive Γ ≈ α /3 • Gauge bosons: X MX Γ ≈ λ 2 /16π • Higgs bosons: S t MS

•CP , again from interference of tree and loop diagrams. Smallish (10−5) but workable.

• Large mass scale enables out-of-equilibrium decays.

The Standard Model and Baryogenesis at 50 Years GUT Baryogenesis

Large mass scale enables out-of-equilibrium decays.

+=−Γ−22 • Evolution of number density via decay/inverse-decay: nHn 3 () nn EQ .

• Figure of merit for departure from equilibrium is ratio of decay rate Γ to expansion rate = = ≈ 2 / at T M: H(T M) M M Pl . ΓΓM • Require ≈ P L to be small. H ()TM= MM o Small coupling as in Departure from equilibrium from decay/inverse-decay

thermal leptogenesis. ==12− 3 Mm1110 GeV;  10 eV o Large mass as in GUT baryogenesis. mM 2 = 16 Γ=11 M X 10 GeV Thermal leptogenesis: DECAY 8π h 2 Γ≈α GUT baryogenesis: DECAY GUT M X

• Similar considerations for 2↔2 scatterings & other reactions.

The Standard Model and Baryogenesis at 50 Years GUT Baryogenesis

Problems with GUT Baryogenesis: • Experimental: proton doesn’t seem to decay at expected level.

• Cosmological: o B − L is a conserved global quantum number in SU(5). Only produce B + L asymmetry, which is washed out by sphalerons. o Symmetry breaking G → H ⊗ U(1) overproduces magnetic monopoles in phase transition via Kibble mechanism and thermal production. o Expected temperatures after inflation smaller than unification scale.

• Perhaps unification at larger mass scale (helps with out-of-equilibrium conditions).

• Beyond SU(5): SO(10) has spontaneously broken local B − L so can produce B − L asymmetry (along with B + L). (Massive right-handed neutrino embedded in SO(10).)

• Cosmological issues more problematic.

• Nevertheless, take another look if observation of proton decay at Hyper-Super- Kamiokande.

The Standard Model and Baryogenesis at 50 Years Affleck-Dine Baryogenesis Affleck & Dine

Consider SUSY GUTs. Before SUSY breaking there is a many-parameter set of flat directions for the vacuum state. In general, the states may have a nonzero vacuum expectation value for sleptons and squarks, l ≠ 0 and q  ≠ 0 . VEV spontaneously breaks CP. After SUSY breaking the flat directions develop minima with curvature m2 set by SUSY soft breaking scale, and eventually fields relax to lq  ==  0 , restoring gauge and global symmetries. φ φφφ+=3Hm  2 H  m frozen V(φ) H  m φ relaxes to minimum, oscillates until Γ = H After decay at Γ=H

1/6 θ 1/6 2 Before SUSY n φφM B  0GUT0 CP 22+φ sMGUT mM GUT 0 After SUSY Can easily be  (10−10) φ 10+2 0 φ = lq, ,... Can easily be  ( )!

The Standard Model and Baryogenesis at 50 Years Affleck-Dine Baryogenesis

Baryon isocurvature perturbations.

Curvature perturbations: perturbations in all components are correlated (w = p / ρ): δρ 133δρ δρ δρ γ δρ i =→===constant CDM B ν + ρρρρρ 144wiiCDM B γ ν

Baryon Isocurvature perturbations: δρ ρδρδρ 3 γ BB=− ρρρ BBISOCURVATURE 4 γ Two sources of baryon perturbations: curvature perturbations set by quantum fluctuations in inflaton field isocurvature perturbations set by quantum fluctuations in the Affleck-Dine field.

CMB observations place limit on amplitude of baryon isocurvature perturbations (indistinguishable from CDM isocurvature perturbations) of a few percent.

The Standard Model and Baryogenesis at 50 Years Spontaneous Baryogenesis Cohen & Kaplan

φ = Λ∂−1 φ μ Scalar field , which interacts with the baryon-number current: φ−B μ jB .

φ φμ Λ≡ ≠ → Field nearly homogeneous but evolves in time (rolls) like inflaton field, B 0 = μ 0 = μ − μ φ−B B jB B (nb –nb) = B nB .

Interaction term shifts relative baryon and antibaryon spectra by an amount 2 φ  Λ , i.e., μ dynamically breaks CPT. Effective chemical potential B leads to net baryon density of ≈ μ 2. nB B T

 ˆ ≠ Require B-violating interactions, but system could be in equilibrium since  CPT, H 0 . φμ == →0 . True ground state has B 0 , so if B -reactions effective, nB

If B -reactions freeze out at T then final n is nT =Λ () φ  2 , resulting inns≈Λ()φ T . F B B F F B F Many implementations.

Concern: produce isocurvature baryon density fluctuations (Turner, Cohen, Kaplan); at the time a feature, now a bug. Complicated ways to avoid this.

The Standard Model and Baryogenesis at 50 Years Baryogenesis Conclusions

• Standard Model of Particle Physics alone, combined with standard cosmological = (0.861 ± 0.005) × 10 −10 model, cannot explain nB/s , at least so far.

• Perhaps answer will come from completely nonstandard cosmology, or from physics way beyond the Standard Model, for instance the ToE*.

• Or perhaps cosmology pointing directions BSM. o Electroweak Baryogenesis: 1st-order phase transition, new scalars coupled to Higgs. New sources of CP . o Thermal Leptogenesis: Exploits BSM physics in neutrino sector. o GUT baryogenesis: Uses concept of unification of forces.

The Standard Model and Baryogenesis at 50 Years Baryogenesis Conclusions

• Standard Model of Particle Physics alone, combined with standard cosmological = (0.861 ± 0.005) × 10 −10 model, cannot explain nB/s , at least so far.

• Perhaps answer will come from completely nonstandard cosmology, or from physics way beyond the Standard Model, for instance the ToE*.

• Or perhaps cosmology pointing directions BSM. o Electroweak Baryogenesis: 1st-order phase transition, new scalars coupled to Higgs. New sources of CP . o Thermal Leptogenesis: Exploits BSM physics in neutrino sector. o GUT baryogenesis: Uses concept of unification of forces.

*ToE — Theory omitting Evidence, which solves YUGE problems by pure thought without making boring testable predictions. Who needs observational verification? Sad. EXPERIMENTS ARE FOR LOSERS! MAGA: #MakeAstrophysicsGreekAgain.

The Standard Model and Baryogenesis at 50 Years Baryogenesis Conclusions

Hoped for disruptions: • Great new theoretical ideas in cosmology or particle physics are certainly welcome. • Unexpected discoveries in particle physics or cosmology welcome. • Discovery of low-scale SUSY would open new possibilities for Electroweak Baryogenesis. • Discovery of non-SM Higgs couplings (e.g., hhh or hZZ) at colliders could mean EWK transition is 1st-order, pointing to Electroweak Baryogenesis. • Evidence for non-minimal Higgs sector could effect EWK transition and introduce new CP phases. • Observation of non-SM sources of CP violation, say large neutron EDM. • Proof that neutrinos are Majorana particles would give impetus to Thermal Leptogenesis. • Observation of proton decay would be evidence for perturbative baryon-number violation at GUT scales; re-examine GUT Baryogenesis.

The Standard Model and Baryogenesis at 50 Years Baryogenesis Conclusions

Hoped for disruptions: • Observation of stochastic background of gravitational radiation with eLISA could be evidence for 1st-order phase transitions. • Observation of a baryon isocurvature component might suggest a rolling field as in Affleck-Dine or Spontaneous Baryogenesis. • Observation of primordial magnetic fields might point to role in baryogenesis.

The Standard Model and Baryogenesis at 50 Years Standard Model & Baryogenesis at 50 Years

Rocky Kolb The University of Chicago The Standard Model and Baryogenesis at 50 Years Standard Model & Baryogenesis at 50 Years

Thanks to collaborators on baryogenesis: Dick Bond, Gian Giudice, Jeffrey Harvey, Stuart Raby, David Reiss, Joe Silk, Michael Turner, & Stephen Wolfram.

Benefitted from reviews by: Antonio Riotto; James Cline; Wilfried Buchmüller, Pasquale Di Bari, & Michael Plumacher; …

Benefitted from conversations & communications with: Andrew Long, James Cline, …

Rocky Kolb The University of Chicago The Standard Model and Baryogenesis at 50 Years