Motivation Loop-suppressed B meson decays can serve as sensitive - PDF document

Probing New Physics with s b B meson decays Ulrich Uwer Content: Motivation Quark flavor physics in the Standard Model Experimental Status Flavor physics beyond the Standard Model LHCb Experiment B meson key measurements at the LHC Motivation Loop-suppressed B meson decays can serve as sensitive probes for New Physics: New W W New New Physics Physics W Physics Penguin Decays Box Diagrams (Oscillation) Additional New Physics amplitudes modify absolute rates but also phase Additi l N Ph i lit d dif b l t t b t l h dependent observables such as CP asymmetries : e.g. SUSY models Heavy quark physics: • Complementary to direct New Physics searches by ATLAS and CMS. • Investigate the flavor structure of NP if found. 2 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 1

Hitorical Examples GIM Mechanism: − μ Observed branching ratio K 0 →μμ d W ν 0 K u μ → → μ μ + μ μ − BR BR ( ( K K ) ) s s W W − = ± ⋅ 9 9 L L ( ( 7 . 2 0 . 5 ) ) 10 μ + BR ( K → all ) L In contradiction with theoretical Glashow, Iliopolus, Maiani (1970): expectation in the 3-Quark Model Prediction of a 2 nd up-type quark K 0 -K 0 mixing: Gaillard, Lee and Rosner (1970++): u , c s d From from K 0 -K 0 mixing frequency: − + 0 0 W K W K m c ~1.5 GeV d s u , c 2 G Δ = θ θ 2 2 2 2 F m m f m cos sin c quark was discovered only in 1974! π K K K c c c 4 3 More Examples ARGUS Experiment, 1987: Observation of B 0 -B 0 Oscillation m t > 50 GeV V ∗ V td tb b t d c u Discarded top discovery . Discarded “top discovery” 0 B B 0 B B v b t d c u ∗ V V tb td Precision electro-weak Physics at the Z + e f Prediction of top mass t 0 0 Z Z via radiative corrections − f e t t = ± ± + + 17 17 GeV G V m 170 170 10 10 − t 19 After top discovery: Prediction of Higgs mass m H < GeV ( % CL ) 144 90 4 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 2

Why studying B mesons ? b quark: ⎛ ⎞ ⎛ ⎞ ⎛ ⎞ u c t • Heaviest quark that forms hadronic ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ bound states (m~4.7 GeV). ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎝ d d ⎝ s s ⎝ b b ⎝ ⎠ ⎠ ⎝ ⎠ ⎠ ⎝ ⎠ ⎠ • Must decay outside 3 rd family • Must decay outside 3 family • All decays are CKM suppressed • High mass: many accessible final states (all Br’s are small) • Long lifetime (~1.6 ps): experimentally simple to identify • Large CP violation expected g p FCNC Tree oscillation 5 B decays (for reference) Dominant decays Semi-leptonic Hadronic Rare hadronic decays R h d i d Gluonic W-exchange Internal spectator penguin Radiative penguin Radiative and leptonic decays Radiative and leptonic decays Electroweak Electroweak penguin box Annihilation 6 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 3

B meson physics PDG 1986 PDG 2009 > 25 pages First observation of B 0 mixing 1987 Λ Λ 1992 1992 Evidence for Evidence for b B , B s → γ B → π + π − * 1993 First observation of , time resolved B mixing B K , Ξ * * , B 1994 Evidence for , measurement of exclusive B lifetime b 1998 Discovery of B c 2001 Discovery of CPV in B system 2006 Measurement of B s mixing 7 Quark Flavor Physics in the Standard Model • Mass generation and quark mixing • Quark Mixing matrix • Quark Mixing matrix • CP Violation in the Standard Model • Unitarity Triangle • Comments on the baryon asymmetry 8 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 4

Mass Generation in Standard Model Standard Model Lagrangian: C.Jarlskog in “CP Violation” L = L ψ + L φ ψ ( A , ) ( , A , ) SM gauge a i Higgs a i ⎛ ⎛ ⎞ ⎞ q ⎟ u q ⎜ ⎜ ⎟ = j Q ⎜ ⎟ jL d q Yukawa couplings: ⎝ ⎠ j L = D d φ + U u φ + φ + L Q Y q Q Y q L Y e h . c . Y jL jk kR jL jk kR C L e R With Higgs doublet and its charge conjugate φ φ + + φ φ ⎛ ⎛ φ φ + + ⎞ ⎞ ⎛ ⎛ ⎞ ⎞ i i 1 1 ⎜ ⎟ φ = = ⎜ ⎟ 1 2 ⎜ ⎟ ⎜ ⎟ φ + φ φ i 0 ⎝ ⎠ ⎝ ⎠ 2 0 3 ⎛ ⎞ φ ( ) ∗ 0 Needed to generate mass for up- ⎜ ⎟ φ = ≡ σ φ i * type quarks. φ * does not ⎜ ⎟ C − φ − 2 ⎝ ⎠ transform as doublet under SU(2) 9 V (φ) Symmetrie Breaking Spontaneous symmetry breaking: υ φ φ = + φ φ = j 1 , , are eaten up 2 3 j 0 = − μ μ λ 2 ~ 246 GeV v 6 GeV 2 2 υ { } = ∑ 1 − + + + d D d u U u L q Y q q Y q h . c . ( φ ) 1 Y jl jk kR jL jk kR υ 2 j , k + d D d u U u q M q q M q jL jk kR jL jk kR υ U,D = = U,D M M Y Y Non diagonal mass matrices: Non-diagonal mass matrices: 2 + UU = Diagonalization with help of unitary matrices: 1 + D D D = D ≡ Diag ( m , m , m ) U M U D L R d s b Diagonalization possible with bi-unitary transformation U U U + = U ≡ Diag ( m , m , m ) U M U D L R u c t Daggers introduced for notational convenience 10 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 5

Physical Quark Fields = = + + = q M q q q q q q D q M U U M U U U U jL jk kR L R L L L R R R L L R R The physical fields (the one which correspond to the mass eigenstates) are: ⎛ ⎞ u ⎛ ⎞ d ⎜ L ⎟ ⎜ L ⎟ = = q , u phys u u u U q U c q , d phys = d d = d ⎜ ⎟ U q U s ⎜ ⎟ L L L L L L L L L L ⎜ ⎜ ⎟ ⎟ ⎜ ⎜ ⎟ ⎟ t t b b ⎝ ⎝ ⎠ ⎠ ⎝ ⎝ ⎠ ⎠ L L φ { } = − + + + + + L phys ( ) m u u m c c m d d K K 1 Y u c d υ → 6 Dirac quark masses 11 Charged Current Interaction expressed with physical quark fields [ ] q u μ = − u γ d + W i W q q h . c . 1 2 μ μ L L q d [ [ ] ] + W = − γ γ μ μ + + u , , phys p y u d d , , phys p y W W 1 i i W W 2 q q U U U U q q h h . c c . μ μ L L L L [ ] μ = − u , phys γ d , phys + W i W q q h . c . 1 2 V μ μ L CKM L Quark mixing in CC described by V CKM ⎛ ′ ⎛ ⎛ ⎞ ⎞ ⎛ ⎞ ⎞ V V pq V V V V V V d d ud d us ub b p ⎜ ⎟ ⎜ ⎟ ′ + ∝ ) ( γ ) γ ⋅ J ( u , c , t - V V V s 5 ⎜ ⎟ ⎜ ⎟ 1 cd cs cb μ μ q ⎜ ⎟ ⎜ ⎟ ′ V V V b W ⎝ ⎠ ⎝ ⎠ td ts tb • In SM Yukawa interaction only source of Flavor Violation • Masses and the mixing angles cannot be understood within SM 12 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 6

Quark mixing & Flavor Violation • In SM Yukawa interaction only source of Flavor Violation • Masses and the mixing angles cannot be understood within SM • Neutral current interaction is flavor conserving: g μ = γ q [ ] q K Neutral current IA R R = γ μ + phys phys q [ ] q K U U R R R R = γ μ phys phys q [ ] q K + = U U 1 R R R R R R R R μ − Flavor Changing Neutral Current (FCNC) d K 0 processes can appear in the Standard μ + s Model only at loop-level: 13 Parameters of CKM matrix 18 parameter (9 complex elements) Number of independent -5 relative quark phases (unobservable) parameters: -9 unitarity conditions =4 independent parameters: 3 angles + phase ⎛ − i δ ⎞ ⎛ d ' ⎞ ⎛ 1 0 0 ⎞ c 0 s e ⎛ c s 0 ⎞ ⎛ d ⎞ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ 13 13 ⎜ 12 12 ⎟ ⎜ ⎟ s ' = 0 c s ⎜ 0 1 0 ⎟ − s c 0 s ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ 23 23 12 12 ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ − − i δ b ' 0 s c s e 0 c 0 0 1 b ⎝ ⎠ ⎝ ⎠ ⎝ ⎠ ⎝ ⎠ ⎝ ⎠ 23 23 13 13 PDG ⎛ − δ ⎞ c c s c s e i parametrization ⎜ ⎟ 12 13 12 13 13 3 Euler angles − − δ − δ ⎜ i i ⎟ s c c s s e c c s s s e s c θ θ θ , , 12 23 12 23 13 12 23 12 23 13 23 13 ⎜ ⎟ δ δ 23 13 12 − i − − i s s c c s e c s s c s e c c ⎝ ⎠ 12 23 12 23 13 12 23 12 23 13 23 13 1 Phase δ = θ = θ where c cos , s sin ij ij ij ij 14 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 7