Matter-antimatter asymmetry in the Universe

Transcription

1 Matter-antimatter asymmetry in the Universe Wan-il Park (KIAS) APCTP-TRP, Nov Dec. 01 (2012), APCTP, Seoul 1

2 Plan Lecture 1 - Our universe - Birth of antimatter - Matter vs. antimatter - Baryon asymmetry in the universe - Symmetry breaking - The origin of the asymmetry Lecture 2 - Ingredients for baryogenesis - Mechanesms 2

3 Our universe Big: RH~3000Mpc~10 10 ly~10 28 cm~10 60 lp Old: th~10 17 sec~10 60 tp Flat: R cur 10H -1 Lots of matter(?): Stars, Galaxies, Clusters, Clusters of Clusters. 3

4 WMAP7 cosmological data Matter: ~27 %, Dark energy: ~73 % [PDG] m 10 6 GeV/cm g/cm 3 ) 1 proton/m 3 4

5 Universe seems made of matter, but our theories predict the existence of antimatter. 5

6 Birth of anti-matter Paul Dirac Relativistic quantum mechanics of free electron: = 0 { k = 0 k Two energy eigenvalues 6

7 Negative energy state? what is this? Dirac s interpretation Feynman-Stuckelberg(1948) A hole in the Dirac sea electron traveling backward in time 7

8 Matter vs. Antimatter A set of charges defines matter or anti-matter. Particle : (x µ ; m, q i ) Antiparticle : C (x µ ; m, q i ) If charge-neutral? particle = antiparticle Relativistic quantum field theories is invariant under CPT-transformation. (Lorentz invariance CPT invariance) m = m 8

9 Precision test of CPT invariance 9

10 Symmetric world # of Particles = # of antiparticles Amount of matter = amount of antimatter A particle meets its antiparticle, and annihilate, leaving only photons and neutrinos. So, in a symmetric world, only photons and neutrinos remain. No structure! (neutrino star? galaxy?) 10

11 Baryon asymmetry in the Universe Empirically, - Daily life: no proton-antiproton annihilation - Solar system: successes of satellite launches, lunar landings and planetary probes - Galaxy: only secondary production of antimatter in cosmic rays - Clusters: non-observation of detectable γ-ray background - Hubble size: no distortion of CMB radiation due to diffuse γ-ray From Big Bang Nucleosynthesis - The abundances of light elements are functions of BAU From cosmic microwave background radiation - CMB acoustic peaks are sensitive to BAU 11

12 Big Bang Nucleosynthesis [Kolb and Tuner] Number density of a nuclear species n A = g A ma T 2 3/2 exp µa T m A Mass fraction X A n AA n B, X X i =1 i µ A = Zµ p +(A Z)µ n B A Zm p +(A Z)m n m A X A / T m N 3(A 1)/2 A 1 X Z p X A Z n exp (B A /T ) Freeze-out of weak interactions p n ' G 2 F T 5 = H(T ) ) T fz 1MeV n n n p =exp mn m p T fz ' 1 6!

13 Determination of the abundances of light elements n A =(X A /A) n = n A (,n ) reaction = h vi n i = f(t ) n i reaction(,t A fz )=H(T A fz ) ) n A (,T A fz ) The abundance of a light element is determined by baryon number asymmetry (η). 13

14 14

15 Cosmic microwave background radiation (CMBR) Saha equation (for the equil. ionization fraction) 1 Xe eq (Xe eq ) 2 = 4 p 2 (3) p Recombination : X eq e T m e 3/2 exp(b H /T ) 0.1 ) T 0.3eV Decoupling of photon from free electrons = n e T e e (Thomson scattering) Decoupling : = H(T ) ) T 0.26eV CMBR = the photon released at decoupling 15

16 CMB from COBE 16

17 CMB from COBE T =2.73K 16

18 T T

19 Acoustic peaks in CMBR Odd peaks: compression Even peaks: rarefaction [ index.html] n B n '

20 Where is the asymmetry from? Theories are invariant under CPT, but... 19

21 Symmetry breaking 1954(Chinowski, Steinberger): An atomic decay: D(p + n)+! [n + n] L=0 L=1 { P tot = P (i) ( 1) L i P (D) =P (p) =P (n) =1 ) P ( )= 1 Pion parity is negative. Before 1956: General belief: Nature is symmetric w.r.t. C and P 1956(Lee, Yang)+1957(Wu, Ambler, Hayward, Hoppes, Hudson): P-violation from the β-decay of Cobalt-60 n! p (+W )! p + e + e C-violation from the non-existence of left-handed antineutrino C( L )= L? 20

22 1964(Cronin, Fitch, Christenson, Turlay): Decay of a long-lived Kaon to two pions K 0 = d s, K L = 1 p 2 K 0 K 0 [K L ] CP= 1! ( + + ) or ( ) CP=+1 CP is violated! Antiparticle does not behaves in a exactly same way as particle. 21

23 Origin of nb/nγ~10-10 Baryogenesis! 22

24 Summary-1 Our universe is made of matter. The asymmetry between matter and antimatter is nb/nγ~ The asymmetry should be generated after inflation dynamically, i.e., baryogenesis is necessary. 23

25 Backup [Wayne Hu, Maryland, Oct., 2002] 24

26 s = c s c 2 s = ṗ ' 1 3 [Wayne Hu, Maryland, Oct., 2002] 25