Baryogenesis and New Physics
How many baryons?
The abundances of the primordial elements and the height of the peaks of the CMB power spectrum dependC.E.M. on the ratio Wagner of baryons-to-photons. EFI & KICP , Univ.Strumia of Chicago HEP Division, Argonne National Lab.
Fields, Sarkar
KICP Colloquium, Univ. of Chicago, February 3rd, 2015 1 Anti-Matter • An inevitable prediction of the marriage of Quantum Mechanics and Special Relativity. Its existence was first postulated by Dirac, in order to make sense of the negative energy states appearing as solutions of the Dirac equation
Dirac, 1930
Positrons discovered by C. Anderson in 1932
• Holes of negative energy : Positive energy positrons. • Antiparticles carry the same mass and spin as particles, but opposite charges. Every particle has its antiparticle. Symmetry C (and CP) relates them. Under reasonable assumptions, CPT is a symmetry of nature. • No symmetry prevents the annihilation of matter and anti-matter. So, they don’t coexist easily together.
2 Matter-Antimatter Annihilation
3 The Puzzle of the Matter-Antimatter asymmetry
• Anti-matter is governed by the same interactions as matter.
• Observable Universe is composed of matter.
• Anti-matter is only seen in cosmic rays and particle physics accelerators
• The rate observed in cosmic rays consistent with secondary emission of antiprotons
n P "10!4 n P
4 Theory vs. Observation
Baryons annihilate with anti-baryons via strong interactions mediated by mesons This is a very efficient annihilation channel and the equilibrium density is
nB¯ nB 20 = 10 n n How does this compare to experiment ? First of all, we have the problem of the unobserved antimatter. Secondly, from the analysis of BBN and CMBR, one obtains, consistently
5 BaryonBaryon AbundanceAbundance inin thethe UniverseUniverse
! Information on the baryon abundance comes from two main sources: ! Abundance of primordial elements. When combined with Big Bang Nucleosynthesis tell us
n B 421 " = , n! = 3 n! cm ! CMBR, tell us ratio
%B !5 2 GeV $#B , %c "10 h 3 %c cm ! There is a simple relation between these two quantities
"8 2 # =2.68 10 !Bh
6 How many baryons?
The abundances of the primordial elements and the height of the peaks of the CMB power spectrum depend on the ratio of baryons-to-photons.
Strumia
Fields, Sarkar
How to explain the absence of antimatter and the appearance of such a small asymmetry ?
7 SmallMatter Asymmetry and may Anti-Matterbe generated dynamically, at temperaturesEarly belowUniverse the reheating one : Baryogenesis
NB=30 000 000 001 NB =30 000 000 000
1,000,000,001 1,000,000,000 t 10−6 s
Matter Anti-matter
Murayama 54 Assuming the existence of a small primordial asymmetry solves the puzzle. Indeed, matter-antimatter annihilation can now occur efficiently and finally the small asymmetry will lead to observable matter in the Universe
8
8 Matter and Anti-Matter Small Asymmetry may be generated primordially : EarlyBaryogenesis Universe
NB=1 NB =0 NB=30 000 000 001 NB =30 000 000 000
1,000,000,001 1,000,000,000 t 10−6 s now
Matter Anti-matter
Murayama 54 Assuming the existence of a small primordial asymmetry solves the puzzle. Indeed,Now matter-antimatterthe question annihilation is: why can was now there occur efficiently in the and very finally early the small asymmetry will lead to observable matter in the Universe Universe an excess of baryons 9 BaryogenesisBaryogenesisBaryogenesis 9 Baryogenesis ConditionsBaryogenes ifors at Baryogenesisthe weak scale
! Under natural assumptions, there are three conditions, enunciated by Sakharov, that need to be fulfilled for baryogenesis. The SM fulfills them :
! Baryon number violation: Anomalous Processes
! C and CP violation: Quark CKM mixing
! Non-equilibrium: Possible at the electroweak phase transition.
10 Anomalous processes in the SM Non-equivalent Vacua and Static Energy in Field Configuration Space
The sphaleron is a static configuration with non-vanishing values of the Higgs and gauge boson fields.
Its energy may be identified with the height of the barrier separating vacua with different baryon number
The quantity v is the Higgs vacuum expectation value, < H > = v. 8! v E = This quantity provides an order parameter which sph distinguishes the electroweak symmetry gW preserving and violating phases. . N &µ j B,L = g Tr( $ µ#!" F F ) µ 32 % 2 µ# !" B = L =3 Instanton configuratio ns (mBay be rLeg)=0arded as semiclasical configurampationslitudes for tunelling effect between vacuum states with different baryon number 11 2" Sinst = #%B$0 " exp(!Sinst ) !W
Weak interactions: Transition amplitude exponentially small. No observable baryon number violating effects at T = 0 .. At high temperatures,B,L theN barrier can be crossed &µ j = g Tr( $ µ#!" F F ) µ 32 % 2 µ# !" Baryon Number Violation at finite T n AnomalousIns tprocessesanton config uviolaterations mbothay b ebaryon regarde dand as s eleptonmiclasi cnumber,al but configurampationslitudes for tunelling effect between vacuum states with preserve d Biff e–re L.nt bRelevantaryon num forber the explanation of the Universe baryon asymmetry. 2" Sinst = #%B$0 " exp(!Sinst 2) !W n At zero T baryon number violating processes highly suppressed Weak interactions: Transition amplitude exponentially small. No observable baryon number violating effects at T = 0 n At finite T, only Boltzman suppression
4MW T