Neutrino masses, Dark Matter and B-L symmetry at the LHC Tong Li - PowerPoint PPT Presentation

Neutrino masses, Dark Matter and B-L symmetry at the LHC Tong Li Center for High Energy Physics, Peking University PHENO2010 May 11, 2010 In collaboration with Tao Han (U. of Wisconsin), Pavel Fileviez P´ erez (U. of Wisconsin) and Wei Chao (Peking U.)

Neutrino masses, Dark Matter and B-L symmetry at the LHC1.New Physics from the observational point of view 1 - New Physics from the observational point of view • Neutrino masses and mixings (Daya Bay, T2K, Icecube...) • Dark matter particle (DAMA, XENON, CDMS...) • Matter-antimatter asymmetry Do they have anything to do with TeV scale physics? 2010/05 2

Neutrino masses, Dark Matter and B-L symmetry at the LHC2.Neutrino Masses and Heavy Majoranas: Type I seesaw 2 - Neutrino Masses and Heavy Majoranas: Type I seesaw • Type I seesaw: singlet right-handed neutrinos N R ∼ (1 , 1 , 0) HN R − M R ν = − Y D ¯ l L � L I 2 N c L N R + h.c.     √ � �  ν c 0 Y D v/ 2 = − 1 R  + h.c.   N c ν L √ L 2 Y T D v/ 2 M R N R ⇒ m ν ∼ v 2 1 Y T 0 = 2 Y D D M R M R is defined by the L/B-L symmetry breaking scale • In the context of SM, production channel of TeV scale heavy Majorana neutrino is pp → W ∗ → Nℓ , but highly suppressed to the order O ( m ν /M R ) Han et al. 06, 09 2010/05 3

Neutrino masses, Dark Matter and B-L symmetry at the LHC3.Testability of U (1) B − L extended Type I seesaw at the 3 - Testability of U (1) B − L extended Type I seesaw at the LHC B − L extension of the SM SU (3) C × SU (2) L × U (1) Y × U (1) B − L L kin = i ¯ u R γ µ D µ u R + i ¯ d R γ µ D µ d R + i ¯ Q L γ µ D µ Q L + i ¯ l L γ µ D µ l L e R γ µ D µ e R + i ¯ N R γ µ D µ N R + i ¯ D µ N R = ∂ µ N R − ig BL B ′ µ N R L scalar = ( D µ H ) † ( D µ H ) + ( D µ Φ) † ( D µ Φ) − V ( H, Φ) D µ Φ = ∂ µ Φ + i 2 g BL B ′ µ Φ HN R − Y M ¯ L ν = − Y D ¯ l L ˜ N C L N R Φ + h.c. 2 √ Once additional scalar singlet Φ ∼ (1 , 1 , 0 , 2) gets vev � Φ � = v Φ / 2 , one gets Z ′ = Z BL with M Z ′ = 2 g BL v Φ and mass matrix of right-handed √ neutrino with M N = Y M v Φ / 2 2010/05 4

Neutrino masses, Dark Matter and B-L symmetry at the LHC3.Testability of U (1) B − L extended Type I seesaw at the The typical signature of this model is to search Z ′ resonance in purely leptonic final states. Leading production channel of N pair pp → Z ′ → NN has large production rate (P .F . Perez, T. Han, TL, PRD80:073015, 2009) 10 2 σ (pp → Z , → N 1 N 1 ) (fb) 10 1 -1 10 -2 10 -3 10 200 400 600 800 1000 M N1 (GeV) 2010/05 5

Neutrino masses, Dark Matter and B-L symmetry at the LHC3.Testability of U (1) B − L extended Type I seesaw at the ∆ L = 2 signal for N decay: NN → ℓ ± ℓ ± W ∓ W ∓ → ℓ ± ℓ ± + 4 jets Basic Cuts • p T ( ℓ min ) > 15 GeV , p T ( j min ) > 25 GeV • | η ( ℓ ) | < 2 . 5 , | η ( j ) | < 3 . 0 • ∆ R jj > 0 . 3 , ∆ R jℓ , ∆ R ℓℓ > 0 . 4 SM Background: same-sign W’s leptonic decay tW ± → W ± W ± jjb ¯ • leading bkg: t ¯ b � • veto SM bkg events with large missing energy � E T < 20 GeV; hadronic W boson reconstruction; the two heavy neutrinos have equal masses 2010/05 6

Neutrino masses, Dark Matter and B-L symmetry at the LHC3.Testability of U (1) B − L extended Type I seesaw at the Decay of heavy neutrinos All the partial decay widths of heavy neutrinos N i are proportional to PMNS m ν /M N , BR ( � V 2 i N i → ℓ ± W ∓ ) under degenerate case: 2010/05 7

Neutrino masses, Dark Matter and B-L symmetry at the LHC3.Testability of U (1) B − L extended Type I seesaw at the BR ( N i → ℓ ± W ∓ ) under non-degenerate case: 2010/05 8

Neutrino masses, Dark Matter and B-L symmetry at the LHC3.Testability of U (1) B − L extended Type I seesaw at the Measuring Branching Fractions and Probing the Neutrino Mass Patterns Event contours in the M Z ′ − M N plane at the LHC including all cuts 1.6 1.6 M Z, (TeV) M Z, (TeV) 1.4 1.4 1.2 1.2 1 1 200 400 600 800 1000 200 400 600 800 1000 M N (GeV) M Ni (GeV) The number of events is written as N = L × σ ( pp → N 1 N 1 ) × 2 BR 2 ( N 1 → ℓ + W − )( 6 9 ) 2 2010/05 9

Neutrino masses, Dark Matter and B-L symmetry at the LHC 4.A pessimistic case: M N > 1 TeV or M Z ′ / 2 4 - A pessimistic case: M N > 1 TeV or M Z ′ / 2 How can we get detectable signatures at the LHC in B-L extension framework? Consider a hybrid seesaw: Type I seesaw plus radiative seesaw model in which an additional SU (2) scalar doublet η T = ( η + , η 0 ) and gauge singlet fermion are included beyond minimal B-L extension of SM (TL, W. Chao, arXiv: 1004.0296 [hep-ph]) 2010/05 10

Neutrino masses, Dark Matter and B-L symmetry at the LHC 4.A pessimistic case: M N > 1 TeV or M Z ′ / 2 Q L , u R , d R l L , ℓ R N R H Φ η ψ 1 B − L − 1 − 1 0 +2 +1 0 3 The relevant lagrangian and scalar potential are L Kin = iQ L γ µ D µ Q L + iu R γ µ D µ u R + id R γ µ D µ d R + il L γ µ D µ l L + iℓ R γ µ D µ ℓ R + iN R γ µ D µ N R + iψ R γ µ D µ ψ R HN R + 1 R ψ R + 1 ηψ R + Y D l L � 2 m ψ ψ C 2 Y M N C −L Y = Y ψ l L � R N R Φ + h.c. L Scalar = ( D µ H ) † ( D µ H ) + ( D µ η ) † ( D µ η ) + ( D µ Φ) † ( D µ Φ) − V V ( H, η, Φ) = − m 2 H H † H − m 2 η η † η − m 2 Φ Φ † Φ + λ H ( H † H ) 2 + λ η ( η † η ) 2 + λ Φ (Φ † Φ) 2 + λ 1 ( H † H )( η † η ) + λ 2 ( H † η )( η † H ) � � + λ 3 ( H † H )(Φ † Φ) + λ 4 ( η † η )(Φ † Φ) + λ 5 ( Hη † ) 2 Φ + h.c. Λ 2010/05 11

Neutrino masses, Dark Matter and B-L symmetry at the LHC 4.A pessimistic case: M N > 1 TeV or M Z ′ / 2 Neutrino mass generation � Φ � H H λ 5 / Λ δ δ ν ψ ν 2010/05 12

Neutrino masses, Dark Matter and B-L symmetry at the LHC 4.A pessimistic case: M N > 1 TeV or M Z ′ / 2 Dark Matter candidate • mass hierarchy: m ψ < m η ≪ M N ∼ M Z ′ ∼ � Φ � ∼ O (TeV) • annihilation rate of ψ 1 m ∆ � 300 GeV 0.8 �� Y Α 1 �� 2 �� Y Β 1 �� 2 0.6 m ∆ � 200 GeV 0.4 � Α , Β 0.1088 �� D h 2 � 0.1158 0.2 m ∆ � 100 GeV 50 100 150 200 250 300 m Ψ � GeV � 2010/05 13

Neutrino masses, Dark Matter and B-L symmetry at the LHC 4.A pessimistic case: M N > 1 TeV or M Z ′ / 2 Production of η and ψ at the LHC when heavy neutrinos are forbidden pp → Z ′ → η + η − → ℓ + ψℓ − ψ -3 10 2 x 10 σ (pp → Z , → δ + δ - ) (fb) d σ /dM ll (fb/GeV) 0.6 10 0.4 1 0.2 -1 10 0 200 400 600 800 1000 0 200 400 600 800 1000 m δ (GeV) M ll (GeV) It is appropriate to determine missing particle mass in this production topology using the invariant mass distribution M ℓ + ℓ − (T. Han, TL, J. Song, in progress) 2010/05 14

Neutrino masses, Dark Matter and B-L symmetry at the LHC 5.Summary 5 - Summary • The production mechanisms for the heavy neutrinos through Z ′ gauge boson in the U (1) B − L extension of SM are studied. We design different cuts to identify signal NN → ℓ ± ℓ ± jjjj and suppress SM backgrounds • We find the ∆ L = 2 channels could provide conclusive signals at the LHC in connection with the light neutrino mass and mixing properties • If we consider heavier Majorana neutrinos situation, radiative seesaw mechanism can give an option of getting physical light neutrino mass and provide dark matter candidate 2010/05 15