Leptogenesis and Colliders Bhupal Dev Washington University in St. - PowerPoint PPT Presentation

Leptogenesis and Colliders Bhupal Dev Washington University in St. Louis ACFI Workshop on Neutrinos at the High Energy Frontier UMass Amherst July 19, 2017

Matter-Antimatter Asymmetry η B ≡ n B − n ¯ ≃ 6 . 1 × 10 − 10 B n γ One number − → BSM Physics Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 2 / 45

Leptogenesis [Fukugita, Yanagida ’86] A cosmological consequence of the seesaw mechanism. Provides a common link between neutrino mass and baryon asymmetry. Naturally satisfies all the Sakharov conditions. L violation due to the Majorana nature of heavy RH neutrinos. New source of CP violation in the leptonic sector (through complex Dirac Yukawa couplings and/or PMNS CP phases). Departure from thermal equilibrium when Γ N � H . Freely available: / L → / B through EW sphaleron interactions. Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 3 / 45

Popularity of Leptogenesis [INSPIRE Database] Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 4 / 45

Popularity of Leptogenesis [INSPIRE Database] Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 5 / 45

Leptogenesis for Pedestrians [Buchm¨ uller, Di Bari, Pl¨ umacher ’05] Three basic steps: Generation of L asymmetry by heavy Majorana neutrino decay: 1 Partial washout of the asymmetry due to inverse decay (and scatterings): 2 Conversion of the left-over L asymmetry to B asymmetry at T > T sph . 3 Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 6 / 45

Boltzmann Equations [Buchm¨ uller, Di Bari, Pl¨ umacher ’02] dN N − ( D + S )( N N − N eq = N ) , dz dN ∆ L ε D ( N N − N eq = N ) − N ∆ L W , dz (where z = m N 1 / T and D , S , W = Γ D , S , W / Hz for decay, scattering and washout rates.) FInal baryon asymmetry: η ∆ B = d · ε · κ f d ≃ 28 1 27 ≃ 0 . 02 ( / L → / B conversion at T c + entropy dilution from T c to T recombination ). 51 κ f ≡ κ ( z f ) is the final efficiency factor, where � z − � z D dN N z ′ dz ′′ W ( z ′′ ) dz ′ κ ( z ) = dz ′ e D + S z i Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 7 / 45

CP Asymmetry Φ † Φ † Φ † Φ L N β N α N α N α N α × × N β L × L C L C Φ L C l l l (a) (b) (c) tree self-energy vertex h l α | 2 − | � | � Γ( N α → L l Φ) − Γ( N α → L c l Φ c ) h c l α | 2 � k Φ c ) � ≡ ε l α = � ( � h † � h ) αα + ( � h c † � Γ( N α → L k Φ) + Γ( N α → L c h c ) αα k with the one-loop resummed Yukawa couplings [Pilaftsis, Underwood ’03] � � h l α = � | ǫ αβγ | � h l α − i h l β β,γ m α ( m α A αβ + m β A βα ) − iR αγ [ m α A γβ ( m α A αγ + m γ A γα ) + m β A βγ ( m α A γα + m γ A αγ )] × , α | A βγ | 2 + m β m γ Re ( A 2 m 2 α − m 2 β + 2 im 2 α A ββ + 2 i Im ( R αγ )[ m 2 βγ )] � m 2 1 A αβ ( � � h l α � α h ∗ R αβ = ; h ) = l β . m 2 α − m 2 β + 2 im 2 α A ββ 16 π l Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 8 / 45

Testability of Seesaw [Drewes ’15] In a bottom-up approach, no definite prediction of the seesaw scale. Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 9 / 45

Testability of Leptogenesis Three regions of interest: High scale: 10 9 GeV � m N � 10 14 GeV . Can be falsified with an LNV signal at LHC. – see Julia’s talk Collider-friendly scale: 100 GeV � m N � few TeV . Can be tested in collider and/or low-energy (0 νββ , LFV) searches. –this talk Low-scale: 1 GeV � m N � 5 GeV . Can be tested at the intensity frontier: SHiP , DUNE or B-factories (LHCb, Belle-II). –see Jacobo’s talk Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 10 / 45

Testability of Leptogenesis Three regions of interest: GUT/high scale: 10 9 GeV � m N � 10 14 GeV . Can be falsified with an LNV signal at LHC. [Deppisch, Harz, Hirsch ’14] – see Julia’s talk Collider-friendly scale: 100 GeV � m N � few TeV . Can be tested in collider and/or low-energy (0 νββ , LFV) searches. –this talk Low-scale: 1 GeV � m N � 5 GeV . Can be tested at the intensity frontier: SHiP , DUNE or B-factories (LHCb, Belle-II). –see Jacobo’s talk Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 11 / 45

Testability of Leptogenesis Three regions of interest: GUT/high scale: 10 9 GeV � m N � 10 14 GeV . Can be falsified with an LNV signal at LHC. [Deppisch, Harz, Hirsch ’14] – see Julia’s talk Collider-friendly scale: 100 GeV � m N � few TeV . Can be tested in collider and/or low-energy (0 νββ , LFV) searches. –this talk Low-scale: 1 GeV � m N � 5 GeV . Can be tested at the intensity frontier: SHiP , DUNE or B-factories (LHCb, Belle-II). –see Jacobo’s talk Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 12 / 45

Vanilla Leptogenesis Hierarchical heavy neutrino spectrum ( m N 1 ≪ m N 2 < m N 3 ). Both vertex correction and self-energy diagrams are relevant. For type-I seesaw, the maximal CP asymmetry is given by � 3 m N 1 ε max ∆ m 2 = 1 atm 16 π v 2 Lower bound on m N 1 : [Davidson, Ibarra ’02; Buchm¨ uller, Di Bari, Pl¨ umacher ’02] � � � � η B 0 . 05 eV m N 1 > 6 . 4 × 10 8 GeV κ − 1 � f 6 × 10 − 10 ∆ m 2 atm Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 13 / 45

Vanilla Leptogenesis Hierarchical heavy neutrino spectrum ( m N 1 ≪ m N 2 < m N 3 ). Both vertex correction and self-energy diagrams are relevant. For type-I seesaw, the maximal CP asymmetry is given by � 3 m N 1 ε max ∆ m 2 = 1 atm 16 π v 2 Lower bound on m N 1 : [Davidson, Ibarra ’02; Buchm¨ uller, Di Bari, Pl¨ umacher ’02] � � � � η B 0 . 05 eV m N 1 > 6 . 4 × 10 8 GeV κ − 1 � f 6 × 10 − 10 ∆ m 2 atm Experimentally inaccessible! Also leads to a lower limit on the reheating temperature T rh � 10 9 GeV. In supergravity models, need T rh � 10 6 − 10 9 GeV to avoid the gravitino problem. [Khlopov, Linde ’84; Ellis, Kim, Nanopoulos ’84; Cyburt, Ellis, Fields, Olive ’02; Kawasaki, Kohri, Moroi, Yotsuyanagi ’08] Also in conflict with the Higgs naturalness bound m N � 10 7 GeV. [Vissani ’97; Clarke, Foot, Volkas ’15; Bambhaniya, BD, Goswami, Khan, Rodejohann ’16] Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 13 / 45

Resonant Leptogenesis L l ( k, r ) N α ( p, s ) � ε ε ′ Φ( q ) Dominant self-energy effects on the CP -asymmetry ( ε -type) [Flanz, Paschos, Sarkar ’95; Covi, Roulet, Vissani ’96] . Resonantly enhanced, even up to order 1, when ∆ m N ∼ Γ N / 2 ≪ m N 1 , 2 . [Pilaftsis ’97; Pilaftsis, Underwood ’03] The quasi-degeneracy can be naturally motivated as due to approximate breaking of some symmetry in the leptonic sector. Heavy neutrino mass scale can be as low as the EW scale. [Pilaftsis, Underwood ’05; Deppisch, Pilaftsis ’10; BD, Millington, Pilaftsis, Teresi ’14] A testable leptogenesis scenario at both Energy and Intensity Frontiers. Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 14 / 45

Flavor-diagonal Rate Equations � � � n γ H N d η N 1 − η N α α γ N α = L l Φ η N z d z eq l � � � � n γ H N d δη L η N α γ N α l = − 1 ε l α L k Φ η N z d z eq α k � �� � � − 2 3 δη L γ L l Φ k Φ c + γ L l Φ L k Φ + δη L γ L k Φ l Φ c − γ L k Φ l k L c L c L l Φ k L l ( k , r ) L k ( k , r ) b b N α ( p , s ) N β ( p , s ) [ b [ b c ] β h ˜ c ] l h ˜ α k Φ ( q ) Φ ( q ) L n ( k 2 , r 2 ) L k ( k 1 , r 1 ) [ L ˜ c ( k 2 , r 2 )] m L k ( k 1 , r 1 ) b h n [ b h ˜ c ] β [ b [ b c ] β h ˜ c ] β h ˜ β k m k b N β ( p ) b N β ( p ) Φ ( q 2 ) Φ ( q 1 ) Φ ˜ c ( q 2 ) Φ ( q 1 ) Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 15 / 45

Analytic Solution [Deppisch, Pilaftsis ’11] 10 4 N 1 10 5 10 6 N 10 7 L L , 10 8 10 9 z 1 z 2 z c z 3 10 10 10 2 10 1 10 0 10 1 10 2 z � � α ε l α 3 η L ( z ) ≃ ( z 2 < z < z 3 ) 2 z K eff l l Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 16 / 45

Flavordynamics M i � 10 12 GeV � 10 9 GeV M i � 10 12 GeV � 10 9 GeV Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 17 / 45

Flavordynamics M i � 10 12 GeV � 10 9 GeV M i � 10 12 GeV � 10 9 GeV Flavor effects important at low scale [Abada, Davidson, Ibarra, Josse-Michaux, Losada, Riotto ’06; Nardi, Nir, Roulet, Racker ’06; De Simone, Riotto ’06; Blanchet, Di Bari, Jones, Marzola ’12; BD, Millington, Pilaftsis, Teresi ’14] Two sources of flavor effects: Heavy neutrino Yukawa couplings h α [Pilaftsis ’04; Endoh, Morozumi, Xiong ’04] l Charged lepton Yukawa couplings y k [Barbieri, Creminelli, Strumia, Tetradis ’00] l Three distinct physical phenomena: mixing, oscillation and decoherence. Captured consistently in the Boltzmann approach by the fully flavor-covariant formalism. [BD, Millington, Pilaftsis, Teresi ’14; ’15] Bhupal Dev (Washington U.) Leptogenesis and Colliders ACFI Workshop 17 / 45