Leptogenesis with Composite Neutrinos

Transcription

1 Leptogenesis with Composite Neutrinos Based on arxiv: In collaboration with Yuval Grossman Cornell University Friday Lunch Talk Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 1 / 42

2 The Outline Is Trivial... Leptogenesis Composite Neutrinos LG with Composite Neutrinos Conclusion Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 2 / 42

3 Leptogenesis Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 3 / 42

4 The Begining of The Story... Y B = n B n B 0 = (8.66 ± 0.35) s Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 4 / 42

5 The Begining of The Story... Y B = n B n B 0 = (8.66 ± 0.35) s Because of the initial condition? For every 10 8 antiquarks, there should be quarks. Inflation diluted all the primordial baryon asymmetry. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 4 / 42

6 The Begining of The Story... Y B = n B n B 0 = (8.66 ± 0.35) s Because of the initial condition? For every 10 8 antiquarks, there should be quarks. Inflation diluted all the primordial baryon asymmetry. Can SM gives us a large enough asymmetry? No! The CPV is too small, and it is difficult to be out of equilibrium. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 4 / 42

7 The Begining of The Story... Y B = n B n B 0 = (8.66 ± 0.35) s Need new physics to generate baryon asymmetry dynamically. e.g. GUT baryongenesis, EW baryogenesis, The Affleck-Dine mechanism,..., Leptogenesis Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 5 / 42

8 Sakharov s Conditions Three ingredients are necessary to dynamically generate a baryon asymmetry: Baryon number violation C & CP violation Out of equilibrium dynamics Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 6 / 42

9 Leptogenesis Idea Generate Y B by leptonic decays. Advantage Solve Y B & m νl problems simultaneously. Leptonic decay that gives Lepton numer asymmetry Sphaleron Effect Lepton Number + Baryon Number Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 7 / 42

10 Receipe of The Day! Thermal LG, An easily making Baryon soup! M. Fukugita and T. Yanagida, Phys. Lett. B 174, 45 (1986). q L L q q L q Cook Time sec sec, about sec, (after inflation) Oven Temperature Gev-10 2 Gev Ingredients Seesaw Mechanism MNN + Y ij Li H N j Maj-neutrinos, N, used for seesaw, m N GeV. SM fields, γ, L ±, H, q, q,... Sphaleron Effect, from electroweak theory. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 8 / 42

11 Preparation L - N L + ɛ L Γ(N LH ) Γ(N LH) Γ(N LH ) + Γ(N LH) q L + N q q - L - q Γ N Y 2 m N < H T =mn m ν = Y 2 v 2 m N m2 N TeV Mix all the ingredients, including the sphaleron effect. After doing the inflation, cool down to GeV. At this time, B = 0, L = 0. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 9 / 42

12 N decay generates L-asymmetry N H* - N H + ɛ L Γ(N LH ) Γ(N LH) Γ(N LH ) + Γ(N LH) Γ N Y 2 m N < H T =mn m ν = Y 2 v 2 m N m2 N TeV When T m N, N begins to decay. The CP phase in the Yukawa gives L-number access. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 10 / 42

13 A little more about N decay... N 1 L N 1 L N 2 L N 1 H L N 2 H H H L H M L = M t I t + M l I l ML = Mt It + Ml Il M L = M t It + M l Il M L = Mt I t + Ml I l ɛ L = M L 2 M L 2 M L 2 + M L 2 Im(M t M l )Im(I t I l ) M t I t 2 Y 2 Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 11 / 42

14 N decay generates L-asymmetry - ɛ L Y Γ N Y 2 m N < H T =mn m ν = Y 2 v 2 m N m2 N TeV When T m N, N begins to decay. The CP phase in the Yukawa gives L-number access. Now L < 0 Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 12 / 42

15 Washout effect! N + + ɛ L Y 2 Γ N Y 2 m N < H T =mn m ν = Y 2 v 2 m N m2 N TeV The inverse decay, 2 2 scattering diminish the existing L-access. Need to make sure the RH neutrino is decoupled from the thermal bath. Γ N < H T =mn Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 13 / 42

16 Ready for Baryongenesis! L - - L L L - - ɛ L Y 2 Γ N Y 2 m N < H T =mn m ν = Y 2 v 2 m N m2 N TeV Now we have L < 0, B = 0 Sphaleron becomes useful! Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 14 / 42

17 Sphaleron effect L q - q L - ɛ L Y 2 Γ N Y 2 m N < H T =mn m ν = Y 2 v 2 m N m2 N TeV The sphaleron effect only act on LH fields, conserves B L and damps B + L. This means B f L f = L i, B f + L f = 0. In our soup, we can change L & B from (L i = 4, B i = 0) to (L f = 2, B f = 2) Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 15 / 42

18 After EWSB Ready to serve!! q q - - q - - q - q ɛ L Y 2 Γ N Y 2 m N < H T =mn m ν = Y 2 v 2 m N m2 N TeV We have both baryon & lepton access in the universe. With the mixing between heavy RH N, the LH neutrino has mass m ν < 0.1eV. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 16 / 42

19 A short conclusion for the standard LG The baryon asymmetry can be parametrized as Y B 1 g ɛ L η C g : relativistic degrees of freedom O(10 2 ) in SM ɛ L : L-asymmetry, O(10 7 ) when η O(1) η: washout effect, O(1) for out-of-equilibrium C: sphaleron effect, SM: C = 12/37, MSSM: C = 10/31 Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 17 / 42

20 A short conclusion for the standard LG The baryon asymmetry can be parametrized as Y B 1 g ɛ L η C g : relativistic degrees of freedom O(10 2 ) in SM ɛ L : L-asymmetry, O(10 7 ) when η O(1) η: washout effect, O(1) for out-of-equilibrium C: sphaleron effect, SM: C = 12/37, MSSM: C = 10/31 Need to satisfy the constraints: two coefficients (m N, Y ), three constraints! ɛ L Y 2 Γ N Y 2 m N < H T =mn m ν = Y 2 v 2 m N m 2 N TeV Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 17 / 42

21 Dirac Leptogenesis Can get LG even if U(1) L is conserved! K. Dick, M. Lindner, M. Ratz and D. Wright, Phys. Rev. Lett. 84, 4039 (2000). Idea leptonic decay + L conservation + L separation Advantage large Y B, small m νl, no need of Majorana neutrinos Leptonic Decay tthat conserves L-number - +L L + -L R annihilation Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 18 / 42

22 Dirac Leptogenesis Can get LG even if U(1) L is conserved! K. Dick, M. Lindner, M. Ratz and D. Wright, Phys. Rev. Lett. 84, 4039 (2000). Idea leptonic decay + L conservation + L separation Advantage large Y B, small m νl, no need of Majorana neutrinos - +L L Leptonic Decay t hat conserves L-number annihilat ion + -L R Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 19 / 42

23 Dirac Leptogenesis Can get LG even if U(1) L is conserved! K. Dick, M. Lindner, M. Ratz and D. Wright, Phys. Rev. Lett. 84, 4039 (2000). Idea leptonic decay + L conservation + L separation Advantage large Y B, small m νl, no need of Majorana neutrinos - +L L Sphaleron Effect Leptonic Decay t hat conserves L-number annihilat ion Lepton Number + Baryon Number + -L R Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 20 / 42

24 A short conclusion for Dirac LG Most of the constraints are the same: Y B 1 g ɛ L η C ɛ L Y 2 Besides, Γ N Y 2 m N < H T =mn New constraint for m ν m 2 N TeV Equilibrating rate R eq < H(T ) until EWSB. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 21 / 42

25 Composite Neutrinos Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 22 / 42

26 Composite Neutrinos Neutrinos are light because they are fat! N. Arkani-Hamed and Y. Grossman,Phys. Lett. B 459, 179 (1999). Idea N R are light composite fermions from a strong dynamics. Advantage The Λ QCD of the strong dynamics suppress m νl naturally. NR M Messenger Preons SM Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 23 / 42

27 Massless baryons? G. t Hooft s Cargese summer lectures (1979) Usually, The baryons in SM have m baryon Λ QCD after confinement. The GSB s coming from the breaking of the global symmetry can remain massless, but this is not for fermions! However, If the strong dynamics is chiral, and we have enough chiral symmetry left after SSB, the massless baryon can exit. How to find the massless baryons in the confinement scale? Gauge symmetry + anomaly matching. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 24 / 42

28 Anomaly Matching Anomaly will never die! G. t Hooft s Cargese summer lectures (1979) Idea In strongly coupled theory with composite degrees of freedom, the anomalies of the constituents and the composites must match. asymptotically free confinement + + Anomaly of the Preons = + + Anomaly of the massless baryons... Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 25 / 42

29 Massless baryons? Usually, The baryons in SM have m baryon Λ QCD after confinement. The GSB s coming from the breaking of the global symmetry can remain massless, but this is not for fermions! However, If the strong dynamics is chiral, and we have enough chiral symmetry left after SSB, the massless baryon can exit. How to identify the massless baryons in the confinement scale? (theory) By checking the anomaly & gauge symmetry, we can identify the correct massless baryons. i.e. massless composite fermions. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 26 / 42

30 The Composite Neutrinos! S. Dimopoulos, S. Raby and L. Susskind, Nucl. Phys. B 173, 208 (1980). An SU(n + 4) gauge theory with 1 antisymmetric tensor A. n antifundamentals ψ i, i = 1...n. can produce n(n + 1) 2 massless composite "baryons" B ij = ψ i Aψ j = B ji. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 27 / 42

31 The Composite Neutrinos! S. Dimopoulos, S. Raby and L. Susskind, Nucl. Phys. B 173, 208 (1980). An SU(n + 4) gauge theory with 1 antisymmetric tensor A. n antifundamentals ψ i, i = 1...n. can produce n(n + 1) 2 massless composite "baryons" B ij = ψ i Aψ j = B ji. Can we use these massless baryons as the RH (or sterile) neutrinos? Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 27 / 42

32 The Composite Neutrinos! Yes, we can! For the simplest case with n = 2, we have: 2(2 + 1) = 3 RH neutrinos. N ij = ψ i Aψ j 2 the effective Yukawa coupling suppressed by the messenger mass M λ ij,α (ψ iaψ j )L α H M 3 = λ ij,α ( Λ M )3 ˆNij L α H NR M Messenger Preons SM Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 28 / 42

33 Two ways of getting m ν Dirac neutrino mass: ( Λ M )3 ˆNLH m ν = ( Λ M )3 v Majorana neutrino mass: For v = 10 2 GeV, ( Λ M )3 ˆNLH + M( Λ M )6 ˆN ˆN m ν = v 2 M, m N = ( Λ M )6 M Λ M = Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 29 / 42

34 UV complete the theory Y. Grossman and Y. Tsai, JHEP 0812, 016 (2008) What are the fields give (ψaψ)lh M 3? A ψ ψ? L H Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 30 / 42

35 UV complete the theory Y. Grossman and Y. Tsai, JHEP 0812, 016 (2008) What are the fields give (ψaψ)lh M 3? A ψ? L A ψ Ω L ψ H ψ Φ H Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 30 / 42

36 The particle spectrum SU(6) C SU(2) L U(1) Y Q spin L Q ps SU(2) ψ i LL α , i E R H α , gω α ab , f ψ a A ab Φ ab k N 189 ; break Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 31 / 42

37 What s next? Now we have the UV completion of the theory, want to do LG with it... Can the decay of the new fields do the job? Do we have CP phase in the theory? Does the theory satisfy the experimental bound? Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 32 / 42

38 Couplings A Ω Ω Φ L H Y L gi AΩ gl i + h.c. M g H Φ Ω g + h.c. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 33 / 42

39 CP phases We have CP phases in the theory: Symbol Number of Number of parameters (R+I) Physical parameters (R+I) MΩ MΦ M Y e Y L Y A M N Y N y N Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 34 / 42

40 Experimental bound µ eγ Ω µ e A Ω µ e A Ω µ e A Comparing to the experimental bound, M Ω Y L > 10TeV. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 35 / 42

41 Experimental bound Big-Bang Nucleosynthesis (BBN) The composite N R give 3 more massless degrees of freedom. BBN and CMB data: N ν 3.3 at 95% CL from E-density bound. To satisfy the E-density bound, need T CNR 0.5T SM The early decoupling of CN R from thermal bath gives T CNR 0.47T SM Safe! Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 36 / 42

42 A short conclusion for Composite Neutrinos The idea of CN R gives small Dirac m νl naturally. We can also have Majorana mass term in the theory. The UV completion of the theory gives us the particle spectrum that: gives CP phases & new decay channels that is necessary for LG. satisfies the experimental bound. has the preons ψ, A, φ & the messenger Ω that couples to the SM sector. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 37 / 42

43 Leptogenesis with Composite Neutrinos Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 38 / 42

44 LG with Composite Neutrinos Y. Grossman and Y. Tsai, JHEP 0812, 016 (2008) Now we have enough tools to begin the work! The idea of the standard LG (with Majo-neutrinos) & the Dirac LG (L-number conservation) The idea of the CN R. The UV completion of the CN R. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 39 / 42

45 LG with Composite Neutrinos Y. Grossman and Y. Tsai, JHEP 0812, 016 (2008) Now we have enough tools to begin the work! The idea of the standard LG (with Majo-neutrinos) & the Dirac LG (L-number conservation) The idea of the CN R. The UV completion of the CN R. Two LG possibilities! Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 39 / 42

46 LG with CN R - The Standard LG When the temperature T that LG begins to happen satisfies T Λ Cannot see preons, there is only N R. Gives the standard LG from N R H L decay. Have m N 10 7 TeV, Λ TeV, M TeV. Still a high energy scale LG scenario. Leptonic NR decay that gives Lepton numer asymmetry Sphaleron Effect Lepton Number + Baryon Number Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 40 / 42

47 LG with CN R - The Dirac LG When the temperature T that LG begins to happen satisfies T Λ No N R, there are only preons. Gives the Dirac LG from the messenger decay Ω AL. The annihilation between A & L is suppressed by (T /M) 6 and H. Can have m Ω as low as 10TeV. Can be a good candidate for low energy LG. Leptonic Omega Decay decay t hat that conserves L-number - +L L + -L RA annihilat ion Sphaleron Effect Lepton Number + Baryon Number Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 41 / 42

48 Conclusion Wake up! Leptogenesis is a plausible baryogenesis scenario which solves the Y B & small m ν problems simultaneously. The Composite RH neutrinos gives small Dirac type m ν suppressed by (Λ/M) 3 The UV completion of the Composite Neutrino theory gives us interesting LG possibilities. Yuhsin Tsai, Cornell University/CIHEP Leptogenesis with Composite Neutrinos 42 / 42