Flavor Physics beyond the SM 48 FCNC Processes in the SM Δ F = 2 Δ F = 1 W q W b b b u c t u, c, t q q u c t u, c, t b b q 2 2 g m 2 2 A ∗ g m → = ⋅ t A ↔ ∗ ⋅ ( ) b q V V 0 0 2 t ( B B ) ~ ( V V ) π SM tb tq 2 2 π SM q q tb tq 16 m 2 2 16 m W W FCNC in SM suppressed: Result of SM particle Result of SM particle • Only in loop diagrams content and hierarchical • CKM couplings small Yukawa couplings • GIM suppression (in B decays inactive) → Suppression of FCNC processes not necessary present in generic extensions of SM. 49 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 1
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 u, c, b s b s X t ⎛ ⎛ ⎞ ⎞ “CKM” c c c c ⎜ ⎜ ⎟ ⎟ A → + = A + SM SM NP NP ( b q X ) factors ⎜ ⎟ Λ BSM 0 2 2 m ⎝ ⎠ W 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: Δ F=2 mixing measurements ( V tb *V td ) 2 1 A (B d ↔ B d ) ~ + c NP 16 π 2 m W 2 Λ 2 G. Isidori (2009) tree + generic flavor Λ > 2 × 10 4 TeV [K] ~ 1 ~ 1/(16 π 2 ) loop + generic flavor Λ > 2 × 10 3 TeV [K] c NP tree + MFV ~ ( V tb *V td ) 2 Λ > 5 TeV [K&B] Not too far from ~ ( V tb *V td ) 2 / (16 π 2 ) loop+ MFV Λ > 0.5 TeV [K&B] EW scale New Physics not “visible” if CKM like flavor structure! 51 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 2
Minimal Flavor Violation Flavor Physics New Physics at TeV-scale must have* ) non-generic flavor structure. * ) modulo some conspiracy * ) d l i 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! 52 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. μ μ + μ μ B B s B s d, s − μ ∗ 0 0 K B A CP (B s → J/ ψ φ ) B d,s → μμ B d → K* γ B d → K* μμ 53 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 3
LHCb Experiment • B production at the LHC • B event signature • LHCb detector 54 B Physics at the LHC B Physics Program Dedicated ATLAS B Experiment B Physics Program B Prodcution at LHC : pp @ 14 TeV → σ bb ≈ 500 μ b 40% B 0 /B + , 10% B s , 10% b-baryons 55 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 4
B Production at the LHC Gluon-Gluon-Fusion: LHCb b � pp collisions at √ s = 7, 10, 14 TeV x x 1 2 p p p p σ inel ~ ( 0.89, 0.95, 1 ) × 100 mb σ bb ~ ( 0.44, 0.67, 1) × 500 μ b b � Correlated forward production of bb � B ± , B 0 , B s , B c , Λ b … ~ 2 x 10 32 cm -2 s -1 (tuned) bb Production � L • ~ 10 12 bb events / year (2 fb 1 ) • ~ 10 12 bb events / year (2 fb -1 ) • 50 kHz bb-events in LHCb • n = 0.7 IA / BX (ATLAS 5…25) θ b � Charged particle multiplicity ~ 30 / unit θ b of rapidity 56 B Physics & LHCb Detector n = # of pp interactions/crossing 1.0 pT of B-hadron pT of B-hadron Probability 0 n=0 LHCb 0.8 S/CMS ATLAS/CMS ATLAS/CMS 10 2 10 2 100 μ b 100 μ b LHCb LHCb 0 6 0.6 ATLAS 230 μ b 0.4 10 10 1 n=1 0.2 2 3 1 1 4 -2 -2 0 0 2 2 4 4 6 6 eta of B-hadron eta of B-hadron 10 31 10 32 10 33 Luminosity [cm −2 s −1 ] LHCb 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 ~ 2 × 10 32 cm –2 s –1 → n ≈ 0.5 57 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 5
Typical Event Simulated Event pp interaction π + (primary vertex) π − B 0 L Κ − b-hadron π + π + l − • Decay length L typical ~ 7 mm all • Decay products with p ~ 1–100 GeV 25 ns 2 m • Trigger on “low p t ” particles (similar to backgr) 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 the High-energy Frontier at the LHC: Probing New Physic with B meson decays 6
LHCb Detector in its cavern Acceptance: 15-300 mrad (bending) Offset interaction point (to make 15-250 mrad (non-bending) Shielding wall best use of existing cavern) (against radiation) Muon System Tracking stations (inner and outer) Magnet Electronics + CPU farm Calorimeters Detectors can be moved away from beam-line RICH2 VELO 20 m for access RICH1 60 LHCb detector � Vertex locator around the interaction region Silicon strip detector with ~ 30 μ m impact-parameter resolution 61 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 7
Vertex detector •21 stations w/ double sided silicon sensors •micro-strip sensors with r φ geometry, •approach to 8 mm from beam (inside complex secondary vacuum system) (inside complex secondary vacuum system) Beam 62 Vertex Reconstruction B s → D s (K K π ) π π + 440 μ m 440 μ m K + K - 144 μ m π ± = 47 μ m 7 mm L Proper time resolution → D → − π + + B 0 B 0 D s s σ ~ 40 fs = βγ L c t 63 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 8
First Vertices 64 Proper time resolution For fully reconstructed B decays: Relative momentum error < 0.1% σ t ~ 40 fs Error dominated by vertex resolution Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 9
Finite Proper Time Resolution ′ ( t ) − τ ′ = / ⊗ σ P t ( , , ) e G t t t also effects the seen asymmetry (see below) LHCb Spectrometer � Warm Magnet, 4.2 MW, 4 Tm, Tracking system and dipole magnet to measure angles and momenta Δ p / p ~ 0.4 %, mass resolution ~ 14 MeV (for B s → D s K) 67 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 10
Main Tracking Stations T1 T2 T3 6 m Inner Tracker: Silicon sensors 1.3% area 20% tracks 5 m Outer Tracker Cross to optimize occupancy for OT OT occupancy average 4.3 % top 5.4 % corner 6.6 % side 6.3 % 264 Module 68 Outer Tracker Straw tube drift chamber modules Cathode Track ac 5mm cells e - e e - - pitch 5.25 mm Straw tube winding: Lamina Dielectrics Ltd. 2.5 m 69 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 11
Outer Tracker 70 First Tracks (Nov 23 rd 2009) 71 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 12
First High-Energy CollIsion (2.36 TeV) 72 First “unstable” particles erg) K s → π + π - → K + - er & S.Stahl (Heidelbe M.Schille 73 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 13
LHCb detector � Two RICH detectors for charged hadron identification 74 RICH = Ring Imaging CHerenkov Detector Cherenkov Radiation RICH detectors are the specialized detectors to allow charged hadron ( π , K, p) identification. c β > if n n Important for B physics, as there are many hadronic decay modes - K + → (K + K - π - ) K + e.g.: B s → D s θ = β cos 1 ( ) n c Since ~7 × more π than K are produced in pp events, making the mass combinations Ring Imaging would give rise to large combinatorial background unless K and π tracks can be background unless K and tracks can be separated Ring radius → θ c → β 75 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 14
Particle Identification RICH 1 RICH 2 θ C max θ C max e 250 242 mrad µ Aerogel π ε (K � K) = 88% 200 K 3 radiators to cover p full momentum range θ C (mrad) 150 100 ε ( π � K) = 3% C 4 F 10 gas 53 mrad 50 32 mrad 32 mrad CF 4 gas π K 0 1 10 100 Momentum (GeV/ c ) Radiator: Aerogel n=1.03 Radiator: CF 4 C 4 F 10 n=1.0014 n=1.0005 76 First RICH Rings (Dec 2009) 77 Probing the High-energy Frontier at the LHC: Probing New Physic with B meson decays 15
Background suppression with PID With RICH No RICH B s → K K B 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 the High-energy Frontier at the LHC: Probing New Physic with B meson decays 16
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