Flavor Physics beyond the SM. FCNC Processes in the SM

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1 Flavor Physics beyond the SM 48 FCNC Processes in the SM A SM ( B ΔF = ΔF = 1 W q W b b u, c, t q b u, c, t q 0 q B ) ~ ( V V 0 q ) tb tq g m 16π m t W A SM ( b q) = V V tb tq g 16π m m t W FCNC in SM suppressed: Only in loop diagrams CKM couplings small GIM suppression (in B decays inactive) Result of SM particle content and hierarchical Yukawa couplings Suppression of FCNC processes not necessary present in generic extensions of SM. 49 Probing New Physic with B meson decays 1

2 Flavor Violation beyond the SM Effects of New Physics* ) at Λ = O(Λ EW ) on B decays can be treated in a low-energy effective theory approach (similar to Fermi-theory). * ) electroweak New Physics in flavor changing amplitudes: Y b A u, c, t s c SM c b q + X ) = A + NP 0 mw Λ NP BSM ( b X s CKM factors Loop-factors In most general case NP with generic flavor structure! There are good arguments that NP should appear around the EW scale. 50 Flavor Problem No indication of large O(1) New Physics contribution to FCNC processes. Puts severe constraints on New Physics. Example: ΔF= mixing measurements (V tb *V td ) A(B d B d ) ~ 16 π m W c NP ~ 1/(16 π ) + c NP 1 ~ 1 tree + generic flavor ~ (V tb *V td ) ~ (V tb *V td ) / (16 π ) loop + generic flavor tree + MFV loop+ MFV Λ Λ > 10 4 TeV [K] Λ > 10 3 TeV [K] Λ > 5 TeV [K&B] Λ > 0.5 TeV [K&B] G. Isidori (009) Not too far from EW scale New Physics not visible if CKM like flavor structure! 51 Probing New Physic with B meson decays

3 Minimal Flavor Violation Flavor Physics New Physics at TeV-scale must have* ) non-generic flavor structure. * ) modulo some conspiracy Minimal flavor violation: Standard Model Yukawa couplings are the only non-trivial flavor-breaking terms also beyond the Standard Model. Minimal flavor violation realized by construction in MSSM SUSY models (CMSSM) often used as reference point. MFV should not be taken as granted! 5 Flavor Structure of New Physics Test MFV Hypothesis - Flavor breaking terms beside SM Yukawas? Study flavor structure of new particles if found by ATLAS/CMS. Expect sizeable deviation even in MVF models B s mixing phase φ s b s γ penguins Very rare FCNC proc. Bs A CP (B s J/ψ φ) Bs 0 B B d K*γ B d K* μμ μ μ 0 K B d,s B d,s μμ + μ μ 53 Probing New Physic with B meson decays 3

4 LHCb Experiment B production at the LHC B event signature LHCb detector 54 B Physics at the LHC B Physics Program Dedicated B Experiment B Prodcution at LHC: 14 TeV σ bb 500 μb 40% B 0 /B +, 10% B s, 10% b-baryons ATLAS B Physics Program 55 Probing New Physic with B meson decays 4

5 B Production at the LHC LHCb pp collisions at s = 7, 10, 14 TeV σ inel ~ ( 0.89, 0.95, 1 ) 100 mb σ bb ~ ( 0.44, 0.67, 1) 500 μb Correlated forward production of bb Gluon-Gluon-Fusion: b p x1 x p b B ±, B 0, B s, B c, Λ b L ~ x 10 3 cm - s -1 (tuned) ~10 1 bb events / year ( fb -1 ) 50 khz bb-events in LHCb n = 0.7 IA / BX (ATLAS 5 5) Charged particle multiplicity ~30 / unit of rapidity bb Production θ b θ b 56 pt of B-hadron ATLAS/CMS 100 μb B Physics & LHCb Detector LHCb 30 μb eta of B-hadron n = # of pp interactions/crossing n=0 Probability LHCb ATLAS S/CMS 1 n= Luminosity [cm s 1 ] LHCb: Forward, single arm spectrometer, 1.9 < η < 4.9 (bb pairs correlated, mainly forward) Excellent vertexing and particle ID (K/π separation) high p T triggers, including purely hadronic modes, very flexible Luminosity tuneable by adjusting beam focus: run at L ~ 10 3 cm s 1 n Probing New Physic with B meson decays 5

6 Typical Event Simulated Event pp interaction (primary vertex) B 0 b-hadron L l π + π Κ π + π + Decay length L typical ~ 7 mm Decay m products with p ~ GeV Trigger on low p t particles (similar to backgr) all 5 ns 58 b Physics at LHC - Summary LHC = b (not only B) factory: B 0, B +, B s, B c, b-baryons ~ 40 : 40 : 10 : 0.1 : 10 % 59 Probing New Physic with B meson decays 6

7 LHCb Detector in its cavern Acceptance: mrad (bending) Shielding mrad (non-bending) wall (against radiation) Offset interaction point (to make best use of existing cavern) Muon System Tracking stations (inner and outer) Magnet Electronics + CPU farm Calorimeters VELO RICH1 0 m Detectors can be moved away RICH from beam-line for access 60 LHCb detector Vertex locator around the interaction region Silicon strip detector with ~ 30 μm impact-parameter resolution 61 Probing New Physic with B meson decays 7

8 Vertex detector 1 stations w/ double sided silicon sensors micro-strip sensors with rφ geometry, approach to 8 mm from beam (inside complex secondary vacuum system) Beam 6 Vertex Reconstruction B s D s (K K π ) π π μm K + K - 47μm L = 7mm 144 μm Proper time resolution π ± L = cβγ t π B 0 + s D s σ ~ 40 fs 63 Probing New Physic with B meson decays 8

9 First Vertices 64 Proper time resolution For fully reconstructed B decays: Relative momentum error < 0.1% Error dominated by vertex resolution σ t ~ 40 fs Probing New Physic with B meson decays 9

10 Finite Proper Time Resolution e t / τ G( t, t, σ ) t = P( also effects the seen asymmetry (see below) LHCb Spectrometer Warm Magnet, 4. MW, 4 Tm, Tracking system and dipole magnet to measure angles and momenta Δp/p ~ 0.4 %, mass resolution ~ 14 MeV (for B s D s K) 67 Probing New Physic with B meson decays 10

11 Main Tracking Stations Inner Tracker: Silicon sensors T1 T T3 6 m 5 m 1.3% area 0% tracks Cross to optimize occupancy for OT Outer Tracker OT occupancy average 4.3 % top 5.4 % corner 6.6 % side 6.3 % 64 Module 68 Outer Tracker Straw tube drift chamber modules Cathode 5mm cells pitch 5.5 mm e - e e - - Track.5 m Straw tube winding: Lamina Dielectrics Ltd. 69 Probing New Physic with B meson decays 11

12 Outer Tracker 70 First Tracks (Nov 3 rd 009) 71 Probing New Physic with B meson decays 1

13 First High-Energy CollIsion (.36 TeV) 7 First unstable particles K s π + π - M.Schille er & S.Stahl (Heidelbe erg) 73 Probing New Physic with B meson decays 13

14 LHCb detector Two RICH detectors for charged hadron identification 74 RICH = Ring Imaging CHerenkov Detector RICH detectors are the specialized detectors to allow charged hadron (π, K, p) identification. Important for B physics, as there are many hadronic decay modes e.g.: B s D s- K + (K + K - π - )K + Since ~7 more π than K are produced in pp events, making the mass combinations would give rise to large combinatorial background unless K and π tracks can be separated if Cherenkov Radiation β > c n cosθ c = 1 ( βn) Ring Imaging Ring radius θ c β 75 Probing New Physic with B meson decays 14

15 Particle Identification RICH 1 RICH θ C (mrad) e μ π K p Aerogel ε (K K) = 88% 3 radiators to cover full momentum range ε (π K) = 3% C 4 F 10 gas θ C max 4 mrad 53 mrad 3 mrad π K CF 4 gas Momentum (GeV/c) Radiator: Aerogel n=1.03 Radiator: CF 4 C 4 F 10 n= n= First RICH Rings (Dec 009) 77 Probing New Physic with B meson decays 15

16 Background suppression with PID No RICH With RICH B s K K purity 13% purity 84% efficiency 79% B s D s K purity 7% purity 67% efficiency 89% 78 LHCb detector e h Calorimeter system to identify electrons, hadrons and neutrals Important for the first level (Level 0) of the trigger. 79 Probing New Physic with B meson decays 16

17 LHCb detector μ Muon system to identify muons, also used in first level (L0) of the trigger 80 LHCb Detector 81 Probing New Physic with B meson decays 17

18 Trigger Calorimeter Muon system B events look very much like minimum bias Pile-up system Level-0 Hardware: (4μs) Readout 40 MHz High p T μ, e, h, γ signatures 1 MHz 1.1,.8, 3.6,.6 GeV PC Farm: Higher Level Trigger KHz Disk Rather modest p t values only modest rate reduction 8 Higher Level SoftwareTrigger Higher Level Trigger (Software) Computing Fram ~ CPUs ~ 30 KHz 1. Confirmation of trigger signature using tracking information (1 ms/track) + track impact parameter information ~ 30 KHz. Global event reconstruction: inclusive & exclusive selections Storage (event size ~ 35 KB) 83 Probing New Physic with B meson decays 18

19 Necessary Tool: B Flavor Tagging B 0 π + π Signal B (same side tagging) Fragmentation kaon near B s B 0 D l + K - Tagging B (opposite tagging) lepton kaon Vertex charge Dilution form oscillation if B 0 Mistag rate Tag ε Tag (%) w (%) ε eff (%) Muon Electron Kaon Dilution D=(1-w) Vertex Charge Frag. kaon (B s ) Effective Tagging Power Combined B 0 (decay dependent: ~4 ε eff =ε Tag D Combined B s trigger + select.) ~6 84 b B s b s s Κ + u u Effect on Asymmetry N( N( A( = N( + N( Observed asymmetry w/ wrong tag fraction ω A meas N ( N ( ( = N ( + N ( N( (1 ω) + N( ω N( (1 ω) N( ω = N( (1 ω) + N( ω + N( (1 ω) + N( ω N ( B )( t ) N ( B )( t ) = ( 1 ω) = (1 ω) A( = D A( N( N( N ( B), N ( B) D = ( 1 ω) Observed number of events of given flavor Tagging dilution : ω=50% D=0 no measurement possible Probing New Physic with B meson decays 19

20 Dilution ω (1-ω) Sensitivity and Tagging Power N( B) N( B) Statistical error of asymmetry A = N( B) + N( B) Ttl Total event number N = N ( B ) + N ( B ) fixed N N B B = qn, = (1 q) N = pn NB q = N σ ( qn ) = N(1 q) q Statistical error calculated according binominal distribution (A or nota): Tagging efficiency: ΔA = 1 (1 A N ) 1/ N N = ε N ΔA = 1 (1 ( εn meas A meas ) 1/ ) Wrong tag fraction: A meas = D A We are interested in A and 1 ΔA = ΔA therefore also in the error of A D meas Δ 1 ~ ε D N A stat = effective tagging power Probing New Physic with B meson decays 0