# Presentation: 237927

## Baryogenesis  and theNew Cosmology

**Baryogenesis****  and the****New Cosmology**

**Mark Trodden****Syracuse University**

- COSMO-02Adler Planetarium, Chicago

- 9/18/2002

## What’s it All About?

- Matter
- Vs
- Antimatter

## A Classic Particle Cosmology Problem

- Wherever you look you see matter and not antimatter.
- Particle physics teaches us matter and antimatter are the same.
- Cosmology teaches us they must exist in equal abundances in the early universe.
- What happened between then and now?
- Baryogenesis!

## Quantifying the Asymmetry

-  Remarkable region  of concordance.
-  Possible for a single  value of ~10-10.
-  A major test of the  Big Bang theory ...
-  ... and our earliest  direct cosmological  data.

## Outline

-  A reminder to get us all on the same page.
-  A quick status summary of a popular    mechanism - electroweak baryogenesis.
-  A plea for cosmological economy.
-  Quintessential Baryogenesis.
-  I’ll just sketch the main ideas here - please  come to discuss the details with me later

*“**Quintessential Baryogenesis”, *Antonio De Felice, Salah Nasri & M.T.
- hep-ph/0207211
- (See also parallel session talk by Xinmin Zhang)

## What’s a Particle Theory to do?

- Sakharov (1968) :
- Violate Baryon number (B) symmetry
- Violate the Charge conjugation and Charge-Parity symmetries (C & CP)
- Depart from thermal equilibrium (becauseof the CPT theorem !!! More about this later.)
- There are _**LOTS**_ of ways to do this!

## Also an Important Clue for Particle Physics

- The Standard Model of particle physics, even though in principle it satisfies all 3 Sakharov criteria, (anomaly, CKM matrix, finite-temperature phase transition) cannot be sufficient to explain the baryon asymmetry!
- This is a clear indication, from observations of the universe, of physics beyond the standard model!

## So What’s Viable?

- Electroweak-like baryogenesis models using 2-higgs, SUSY, ...
- Affleck-Dine models – inflation driven
- GUT baryogenesis
- Baryogenesis through preheating after inflation (high and low scale)
- Baryogenesis through leptogenesis
- And many more ...

## Electroweak Baryogenesis I

## Electroweak Baryogenesis II

- Requires more CP violation than in SM
- (Usually) requires a (sufficiently strong) 1st order thermal EW phase transition in the early universe.
- Our most popular model of recent years

- Popularity of this idea is tightly bound to its testability.
- Physics involved is all testable in principle at realistic colliders.
- Small extensions needed can all be found in SUSY, which is an independently attractive
- However, the testability of electroweak scenarios also leads to tight constraints.

## Bounds and Tests

- Exists only a small window of parameter space in extensions of the electroweak theory in which baryogenesis is viable
- Because electroweak baryogenesis requires a strong enough first order phase transition
- Severe upper bound on lightest Higgs boson  mass,  mh <120 GeV (in the MSSM)
- Stop mass may be close to experimental bound and must be < top quark mass.

- (See Carena, Quiros, Seco and Wagner, hep-ph/0208043)

## Direct Tests

- Search for the lightest Higgs at Tevatron or LHC.
- Search for the lightest stop at the Tevatron or LHC.
- Crucial test may come from B-physics - CP-violating effects (but not guaranteedat B factories)
- Essential to have new measurements of CP-violation, particularly in the B-sector

## CP-Violation

- In allowed parameter space - BR(bs) different from the Standard Model case.
- BUT : exact value depends strongly on, for example, value of the -parameter
- Typical difference with respect to SM is of order present experimental sensitivity
- In principle testable in the near future.
- For typical spectrum (light charged Higgs) BR(bs) somewhat higher than in the SM case, but not always

## Testable Alternatives

- Might hope that Affleck-Dine occurs at low enough energies – new particles           (Dine, Randall & Thomas)
- BUT low scale inflation is very hard to make work
- Leptogenesis hard to test if have heavy right-handed neutrinos (Low-scale versions might help)

## What Might We Hope For?

- EWBG is so great because it is testable and uses physics that is _***already there for a good particle physics reason***_
- If EWBG is successful, it is a triumph of the particle physics/cosmology union
- If EWBG is unsuccessful, _***our primary attention should be focused on models with the same properties***_

## A Plea for Cosmological Economy

-  Despite indicators to the contrary (none  discovered in nature to date)
-  Cosmology continues to experience a   robust period of growth in the scalar field sector

-  Possible that this scalar field bubble may burst
-  At the very least we may consider limiting our   exposure in this sector.
-  ...and do our best to avoid accounting scandals.

## Quintessential Inflation I

- (Peebles and Vilenkin)

-  There is a considerable amount   of data in agreement with   predictions of a wide class of   inflationary models

- (Wayne Hu)

-  Data also seems to point to a   dominant dark energy component  in the universe.

- Maybe they are due to the
- Same field!

## Quintessential Inflation II

-  One field drives inflation
-  Much later, it then  drives quintessence

-  In interim, universe is kinetic energy dominated   radiation-dominated  matter-dominated
-  Matter creation not through reheating but   through particle creation during transition from   inflation to “kination”.

## Quintessential Baryogenesis

- (De Felice, Nasri & MT; see also Li, Wang, Feng & Zhang)

-  When I told you about the departure from  equilibrium I omitted a loophole.  (Nice review in Dolgov)
-  If CPT is broken - asymmetry can be generated in  equilibrium!
-  Can’t break CPT explicitly
-  But if broken *spontaneously*, can generate a  baryon asymmetry.

**Spontaneous Baryogenesis****(Cohen & Kaplan)**

- Might the Quintessential Inflation field playthis role?

## What is Required?

- Terms in effective Lagrangian of form

- J : current  some global symmetry (e.g. B or B-L)
- Since  homogeneous can write

- A time-dependent “chemicalpotential” for (e.g.) baryon number

- What net baryon number does this yield?

## Calculating the Asymmetry

- Number density atnonzero chemical potl.

- So

-  Divide by entropy density
-  Note that baryon number violating processes   “freeze out” at temperature TF
-  Resulting baryon to entropy ratio  is

- (This is all standardspontaneous baryogenesis)

## Calculating TF

- This is where the details of quintessential inflationare crucial. Answer depends on:

-  The potential V() (but not really a free   parameter - constrained through cosmology)
-  The source of baryon number violation
-  The evolution of the universe before and at TF

-  Important to take into account that universe   could be kinetic-energy dominated down to below  TF  (Joyce; Joyce & Prokopec)
-  Affects not only the asymmetry produced, but   how much it may be diluted by anomalous  electroweak processes.

## Graphical Summary

## Constraints and Tests

- (See Carroll, PRL **81**, 3067 (1998), astro-ph/9806099)

-  If our current is that for baryon number, then

-  Electromagnetic part  rotation of polarized  light from radio sources

- 

- In Peebles-Vilenkin model

- Consistent with quintessential baryogenesis !

## Conclusions I

-  There are many models out there that have a  chance to explain the asymmetry.
-  We should focus on those that are consequences  of other physics.
-  Upcoming collider experiments will test some   of our favorite models

## Conclusions II

- -Thank You -

-  Have demonstrated how a single scalar field can  be responsible for:
-  Inflation
-  Baryogenesis
-  Dark energy

-  Model may be testable if the scales and  couplings are of the right size
-  An attempt to understand how   independently-motivated models may explain other  cosmological phenomena