Physics with bottom quarks: The LHCb experiment Marcel Merk Nikhef and the Free University Jan 20, 2009 Contents: Physics with b-quarks  CP Violation The LHCb Experiment Veldhoven Focus Session F01: The start-up of the LHC at CERN

LHC CMS ALICE ATLAS LHCb CERN

LHC: Search for physics beyond Standard Model Atlas/CMS: direct observation of new particles LHCb: observation of new particles in quantum loops LHCb is aiming at search for new physics in CP violation and Rare Decays Focus of this talk AtlasCMSLHCb

Flavour physics with 3 generations of fermions u d c s t b IIIIII e   e   quarks leptons ~ ~ ~7 ~3 LEP 1 2 neutrino’s 3 neutrino’s 4 neutrino’s measurements Beam energy (GeV) Cross section Note: In the Standard Model 3 generations of Dirac particles is the minimum requirement to create a matter - antimatter asymmetry (CP violation). (masses in MeV)

Interactions between Quarks Cabibbo described “V-A” quark interactions with flavour changing charged currents:  quark mixing Nicola Cabibbo u d, s W g weak Jμ+Jμ+

Interactions between Quarks Cabibbo described “V-A” quark interactions with flavour changing charged currents:  quark mixing Kobayashi and Maskawa predicted in 1972 the 3 rd quark generation to explain CP-Violation within the Standard Model  Nobel Prize 2008 (shared with Nambu) Nicola Cabibbo Makoto Kobayashi Toshihide Maskawa u, c, t d, s, b W g weak Jμ+Jμ+ Matter →Antimatter g weak →g* weak 9 Coupling constants: g weak → g ∙ V CKM

The CKM Matrix V CKM d s b uctuct

The CKM Matrix V CKM d b d c V cb Typical B-meson ( ) decay diagram: The B-meson has a relatively long lifetime of 1.5 ps Related to mass hierarchy? W u d

The CKM Matrix V CKM From unitarity (V CKM V † CKM =1) : CKM has four free parameters: 3 real: A (  ),  1 imaginary: i  Particle → Antiparticle: V ij → V ij * => 1 CP Violating phase! Wolfenstein parametrization: V CKM

The CKM Matrix V CKM From unitarity (V CKM V † CKM =1) : CKM has four free parameters: 3 real: A (  ),  1 imaginary: i  Particle → Antiparticle: V ij → V ij * => 1 CP Violating phase! Wolfenstein parametrization: V CKM

Benchmark Example: B s →D s K

Benchmark Example: B s →D s K But how can we observe a CP asymmetry? Decay probabilities are equal? No CP asymmetry?? Make use of the fact that B mesons “mix”….. Decay amplitudes: particles: antiparticles:

The CP violating decay: B s →D s K Due to mixing possibility the decay B s →D s – K + can occur in two quantum amplitudes: A2. Directly: A1. Via mixing: Coupling constant with CP odd phase  It is straighforward to show that the interference term of the two amplitudes have an opposite sign for the particle and antiparticle cases.  The observable CP violation effect. A B-meson can oscillate into an anti-B: s b bs W t t W BsBs BsBs

Double slit experiment with quantum waves BsBs Ds-Ds-  LHCb is a completely analogous interference experiment using B-mesons…

6-sept-2007 Nikhef-evaluation 15 “slit A”: A Quantum Interference B-experiment pp at LHCb: 100 kHz bb Decay time BsBs Ds-Ds-  “slit B”: Measure decay time

6-sept-2007 Nikhef-evaluation 16 CP Violation: matter – antimatter asymmetry BsBs DsDs  An interference pattern: Decay time  Decay time

6-sept-2007 Nikhef-evaluation 17 BsBs Ds+Ds+  BsBs DsDs  Matter Antimatter CP-mirror: Difference between curves is proportional to the CKM phase  Decay time  Decay time An interference pattern: CP Violation: matter – antimatter asymmetry Observation of CP Violation is a consequence of quantum interference!!

6-sept-2007 Nikhef-evaluation 18 Searching for new virtual particles Standard Model BsBs J/   Standard Model  Decay time

6-sept-2007 Nikhef-evaluation 19 Searching for new virtual particles Standard Model New Physics BsBs J/    Decay time Tiny CP-odd phase in couplings! Possible CP-odd phase in couplings!

6-sept-2007Nikhef-evaluation20 Searching for new virtual particles Standard Model New Physics Mission: To search for new particles and interactions that affect the observed matter-antimatter asymmetry in Nature, by making precision measurements of B-meson decays. B->J/  BsBs J/   Search for a CP asymmetry:  Decay time

LHC A Large Hadron Collider Beauty Experiment for Precision Measurements of CP-Violation and Rare Decays CMS ALICE ATLAS LHCb CERN √s = 14 TeV LHCb: L =2-5 x cm -2 s -1  bb = 500  b  inel /  bb = 160 => 1 “year” = 2 fb -1 b b b b

b-b detection in LHCb LHCb event rate: 40 MHz 1 in 160 is a b-bbar event b-bbar events per year Background Supression Flavour tagging Decay time measurement vertices and momenta reconstruction effective particle identification (π, К, μ, е, γ) triggers b tag BsBs KK KK KK  DsDs Primary vertex ~1 cm

23 GEANT MC simulation Used to optimise the experiment and to test measurement sensitivities

24 A walk through the LHCb detector  pp ~ 200 mrad ~ 300 mrad (horizontal) 10 mrad

B-Vertex Measurement  Vertex Locator (Velo) Silicon strip detector with 5  m hit resolution Vertexing: Impact parameter trigger Decay distance (time) measurement DsDs BsBs KK KK KK  d 47  m 144  m 440  m Primary vertex Decay time resolution = 40 fs  ) ~40 fs Example: Bs → Ds K

26 Momentum and Mass measurement  Momentum meas.: Mass resolution for background suppression

27 Momentum and Mass measurement  Momentum meas.: Mass resolution for background suppression btbt BsBs KK KK    K   DsDs Primary vertex Bs→ Ds K Bs →Ds  Mass resolution  ~14 MeV

28 Particle Identification  RICH2: 100 m3 CF4 n= RICH: K/  identification using Cherenkov light emission angle RICH1: 5 cm aerogel n= m 3 C 4 F 10 n=1.0014

29 Particle Identification  RICH2: 100 m3 CF4 n= RICH: K/  identification; eg. distinguish D s  and D s K events. RICH1: 5 cm aerogel n= m 3 C 4 F 10 n= Cerenkov light emission angle btbt BsBs KK KK  ,K   DsDs Primary vertex K  K : ± 0.06%   K : 5.15 ± 0.02% Bs → Ds K

30 LHCb calorimeters  e h Calorimeter system : Identify electrons, hadrons, neutrals Level 0 trigger: high E T electron and hadron btbt BsBs KK KK KK  DsDs Primary vertex

31 LHCb muon detection   Muon system: Level 0 trigger: High Pt muons Flavour tagging:  D 2 =  (1-2w) 2  6% b tag BsBs KK KK KK  DsDs Primary vertex

The LHCb Detector VELO Muon det Calo’s RICH-2Magnet OTRICH-1 VELO Muon det Calo’s RICH-2Magnet OT+ITRICH-1 Installation of detector is completed

We have seen the first events from the LHC

First LHC Tracks in the Velo linked hits not linked hits  Talk of Ann Van Lysebetten

Cosmic tracks in LHCb Detector alignment T0 calibration RT-relation …

Events from the LHC beam injection

In Summary DsDs BsBs KK KK  ,K   d p 47  m 144  m 440  m Bs  Ds-K+ MC 5 years data: Reconstruct and select B-events: Decay time (ps) Extract CP-Violation parameters: Detect produced particles: Decay time spectra:

Conclusion and Outlook Complementary research approach: Atlas and CMS look for new physics via direct production of particles LHCb studies new physics via the couplings in B-decay loop effects In LHCb many different B-decay studies are prepared to examine CP violation and rare decays. The experiment is ready for data in 2009!

Backup Slides

Summary of Signal Efficiencies

Conclusions LHCb is a heavy flavour precision experiment searching for New Physics in CP Violation and Rare Decays A program to do this has been developed and the methods, including calibrations and systematic studies, are being worked out.. CP Violation: 2 fb -1 (1 year)*  from trees: 5 o - 10 o  from penguins:  10 o B s mixing phase:  s eff from penguins: 0.11 Rare Decays: 2 fb -1 (1 year)* Bs  K*  s 0 : 0.5 GeV 2 B  s  A dir, A mix : 0.11 A  : 0.22 B s   BR.: 6 x at 5  We appreciate the collaboration with the theory community to continue developing new strategies. We are excitingly looking forward to the data from the LHC. * Expect uncertainty to scale statistically to 10 fb -1. Beyond: see Jim Libby’s talk on Upgrade 42

LHCb Detector MUON RICH-2 PID RICH-1 PID Tracking (momentum) vertexing HCAL ECAL

Display of LHCb simulated event

First sign of New Physics in B s mixing? SM box has (to a good approx.) no weak phase:  SM = 0 S.M.N.P.

First sign of New Physics in B s mixing? SM box has (to a good approx.) no weak phase:  SM = 0 If  S ≠ 0 then new physics outside the CKM is present… S.M.N.P. UTfit collab.; March 5, 2008 Combining recent results of CDF, D0 on with Babar, Belle results: March 5,  deviation From 0

Quark flavour interactions Charged current interaction with quarks: Quark mass eigenstates are not identical to interaction eigenstates: In terms of the mass eigenstates the weak interaction changes from: u, c, t d, s, b W g weak J

Quark flavour interactions Charged current interaction with quarks: Quark mass eigenstates are not identical to interaction eigenstates: In terms of the mass eigenstates the weak interaction changes to: Cabibbo Kobayashi Maskawa quark mixing matrix u, c, t d, s, b W g weak J

Sept 28-29, B meson Mixing Diagrams Dominated by top quark mass: d b bd W u,c,t W BdBd BdBd A neutral B-meson can oscillate into an anti B-meson before decaying:

Sept 28-29, B 0 B 0 Mixing: ARGUS, 1987 First sign of a really large m top ! Produce a b b bound state,  (4S), in e + e - collisions: e + e -   (4S)  B 0 B 0 and then observe: ~17% of B 0 and B 0 mesons oscillate before they decay   m ~ 0.5/ps,  B ~ 1.5 ps Integrated luminosity : 103 pb -1

B d vs B s mixing d b b d W t t W BdBd BdBd Due to the different values of CKM couplings the B s mixes faster then the B d s b b s W t t W BsBs BsBs B d → B d B d mixing B s mixing B s → B s B s mixing Both the B d and B s mixing have been precisely measured in experiments 5.1 x Hz1.8 x Hz

Sept 28-29, Observing CP violation |A||A|  Only if both  and  are not 0 B  D s + K − B  D s − K + A=a 1 +a 2   ++ -- a1a1 a1a1 a2a2 a2a2 A A Compare the |amplitude| of the B decay versus that of anti-B decay;   is the CP odd phase,  is a CP even phase Note for completeness: since the CP even phase depends on the mixing the CP violation effect becomes decay time dependent

53  ~1.4  1.2 m 2 Red = Measurements (hits) Blue = Reconstructed tracks Eff = 94% (p > 10 GeV) Typical Momentum resolution  p/p ~ 0.4% Typical Impact Parameter resolution  IP ~ 40  m LHCb tracking: momentum measurement

54 LHCb trigger HLT rate Event typePhysics 200 HzExclusive B candidates B (core program) 600 HzHigh mass di- muons J/ , b  J/  X (unbiased) 300 HzD* candidatesCharm (mixing & CPV) 900 HzInclusive b (e.g. b  ) B (data mining) HLT: high IP, high p T tracks [software] then full reconstruction of event 40 MHz 1 MHz 2 kHz L0: high p T ( , e, , h) [hardware, 4  s] Storage (event size ~ 50 kB) Detector L0, HLT and L0×HLT efficiency Note: decay time dependent efficiency: eg. Bs → Ds K Proper time [ps]  Efficiency  btbt BsBs KK KK KK  DsDs Primary vertex 54

Flavour Tagging Performance of flavour tagging: Efficiency  Wrong tag wTagging power BdBd ~50% BsBs 33%~6% Tagging power:

56 Measuring time dependent decays btbt BsBs KK KK   DsDs Primary vertex Measurement of Bs oscillations: B s ->D s –   (2 fb -1 ) Experimental Situation: Ideal measurement (no dilutions)

57 Measuring time dependent decays btbt BsBs KK KK   DsDs Primary vertex B s ->D s –   (2 fb -1 ) Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging dilution

58 Measuring time dependent decays btbt BsBs KK KK   DsDs Primary vertex B s ->D s –   (2 fb -1 ) Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging dilution + Realistic decay time resolution

59 Measuring time dependent decays btbt BsBs KK KK   DsDs Primary vertex B s ->D s –   (2 fb -1 ) Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging + Realistic decay time resolution + Background events

60 Measuring time dependent decays btbt BsBs KK KK   DsDs Primary vertex Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging dilution + Realistic decay time resolution + Background events + Trigger and selection acceptance Two equally important aims for the experiment: Limit the dilutions: good resolution, tagging etc. Precise knowledge of dilutions B s ->D s –   (2 fb -1 ) Measurement of Bs oscillations:

Bs  DsK 5 years data Bs  Ds-K+Bs  Ds+K- Bsb  Ds-K+ Bsb  Ds+K-

Conclusion: after 5 years of LHCb… To make this plot only Standard Model physics is assumed. CKM Unitarity Triangle in 2007: Expected errors after 5 years (10 fb -1 ) of LHCb:

Conclusion and Outlook LHCb CP Violation Measure the Bs mixing phase (B s →J /   ) Measure the CKM angle gamma via tree method ( B s → D s K ) Measure the CKM angle gamma via penguin loops ( B (s) → h  h  ) Rare Decays Measure Branching Ratio B s →  +  - Measure angular distribution B 0 → K*  +  - Measure radiative penguins decays: b → s  → X s  Other Flavour Physics Angle beta, B-oscillations, lifetimes, D-physics, Higgs,…? The collaboration has organised analysis groups and identified “hot topics”: Atlas and CMS look for new physics via direct production of particles LHCb tries to study it via the (possibly complex) couplings in B decay loop diagrams

In the mean time: Detector Commissioning and Analysis Preparation DsDs BsBs KK KK  ,K   d p 47  m 144  m 440  m Bs  Ds-K+ Monte Carlo study for 5 years data: