1. Physics Performance of LHC-B Neville Harnew University of Oxford Beauty-97, Los Angeles October 13-17 1997 Outline Introduction The LHC-B Experiment New Developments : The Trigger The RICH Physics Performance Summary

2. LHC will provide an intense source of B-hadrons :  bb  b Unprecedented source of bb pairs. Probe consistency of the Standard Model : CKM Physics CP Violation B s -B s mixing Rare B decays, FCNC’s LHC-B specialised detector : Measure x s,  ’,  in SINGLE EXPERIMENT. Precision probe of new physics beyond SM. MOTIVATION FOR B PHYSICS AT LHC-B

3. V * td Measure angles  Side V * td (  ’ )   Unitarity Triangle Unitarity Triangle  V * ub V ud +V * cb V cd +V * tb V td ) = 0  V * ud V td +V * us V ts +V * ub V tb ) =0 (, i)(, i) (   , i   )) (1-     , i   ) 0 Re 1 0 Re 1     ’ Im  V * ub  V * td Test of Standard Model 2 unitarity conditions of CKM matrix out of 6 which give triangles which do not have a side much shorter than the other two :   

5. Production angle  b vs  b Advantages bb production sharply peaked forward-backward Low luminosity is sufficient (1.5x10 32 cm -2 s -1 )  Less radiation  >80% single interactions Threshold for p t trigger can be set low, 1.1-1.25 GeV/c Fast B hadrons  Accepted ~ 80 GeV/c  Mean flight path of B’s ~ 7 mm Open geometry allows for easy installation and maintenance Vertex detector close to interaction region. Disadvantages Minimum bias also peaks forward High occupancy, high track density Needs more sophisticated trigger than high p t Forward Geometry

7. Advantages of LHC-B Rhobust and efficient 4 Level Trigger system Level 0 : Muon p T > 1.25 GeV/c Electron p T > 1.4 GeV/c Dihadron p T > 3 and 2 GeV/c Level 1 : Vertex and track trigger Level 2 and 3 : Software triggers Very good particle identification : Muon system Electron (e-  separation > 100) p/K/  /  separation with two RICH detectors (3   /K separation between ~2 to 150 GeV/c) Good decay time resolution Decay distance resolution ~ 120  m Decay time resolution ~ 0.04 ps Bunch crossing rate 40 MHz Bunch crossing with single interaction 9 MHz b-hadron production rate 75 kHz

8.  inelastic = 80 mb,  bb = 500  b Nominal luminosity = 1.5 x10 32 cm -2 s -1 (Max luminosity = 5 x10 32 cm -2 s -1 ) Interaction rate (single interaction) = 9 MHz Fraction of bunch crossings with no interaction = 0.68 Fraction of bunch crossing with one interaction = 0.26 Choice of Luminosity Number of interactions vs. Luminosity Probability of B interaction vs. Luminosity

9. B  Event Full GEANT simulation dN/dA  R 2 particles/cm 2 (<5% occupancy)

10. LHC-B Trigger

12. LHC-B  -Vertex Precision vertexing :  z primary  m  t Bs mixing  ps Level 1 Trigger Device

14. Vertex detector L1 trigger provides ~10 suppression with efficiency 75% for B    - and 90% for B s  D s      - Track-finding with 3 successive planes of r-strip detectors : reconstruct primary vertex by histogramming combinations with opposite (   sectors). Calculate impact parameters (IP) wrt primary and cut on this quantity Add  -strip information for tracks with large IP Construct 2-track vertices in space LHC-B Level 1 Vertex Trigger

16. LHC-B RICH  /K Separation 3   /K separation between ~2 to 150 GeV/c

17. LHC-B RICH DETECTOR CHARACTERISTICS RICH-1 : Combined Aerogel and gas (C 4 F 10 ) Approx 125 HPDs, 250000 pads. C 4 F 10 : n=1.0014 ; ~ 55 Thresholds :  2.7 GeV/c, K 9.4 GeV/c Aeogel : n=1.03 ; ~ 15 Thresholds :  0.6 GeV/c, K 2.0 GeV/c RICH-2 : Gas (CF 4 ) Approx 125 HPDs, 250000 pads. CF 4 : n=1.0005 ; ~ 30 Thresholds :  4.6 GeV/c, K 16.3 GeV/c RICH 1,2 Detectors provide  /K separation in LHC-B between 1 and 150 GeV/c LHC-B will develop HPD in collaboration with industry 2000 Si pads per HPD, 2x2 mm pads Amplifier/Shaper/L0-Pipeline inside the gas envelope Large area coverage (11 cm diameter photocathode) 80% photocathode active area (HPD) 90% packing active area

18. PATTERN RECOGNITION IN RICH-1 Aerogel: n=1.03, =15 C 4 F 10 : n=1. 0014, =55 B     event Reconstruction efficiency and purity both better than 90% (for  and K) Random hits - Rayleigh scattered  ’s Scale in cm

19. LHC-B Prototype RICH Aerogel and C 4 F 10 Cerenkov rings for 10 GeV/c Pions : 1/4 scale prototype Aerogel : approx 1.4 mean no. of photons observed, 2.0 expected (N 0 ~ 100 cm -1 prelim.) C 4 F 10 : approx 7.9 mean no. of photons observed, 6 expected (N 0 ~ 230 cm -1 prelim.) First Ring Imaging Counter using hybrid photo diodes SEE TALK BY N.BROOK Scale in mm PRELIM

20. LHC-B Event Rates (LoI) L=1.5x10 32, 1 year running (=10 7 s)  recon  0.3,  tag  0.4 not included These are LoI values, tabulated values are conservative Expect improvement with new L1 trigger scheme -

21. LHC-B PHYSICS PERFORMANCE x S measurement sin2  sin 2   Note : All sensitivities quoted are still LoI. New calculations in progress : Improvement expected.

22. B0B0 BB J/   , e   +, e +  ++ KK D0D0  , e  Ks0Ks0 Lepton Tag Kaon Tag B Flavour Tagging eg. B  J/  K s 0 Signal B Tag B

23. Bs-Bs Oscillations Look at time evolution of B s  D s  No CP violation expected Time evolution of B s (B s ) given by : R   t)  exp(-t/  s ) (cosh(  s /2 t)  1-2  cos(  m s t) ) Fit  m s,  s,  s ; x s =  m s /  s LHC-B in one year: 35k tagged B s  D s  events (wrong tag fraction,  LHC-B x s reach  B s tag X s   Proper time distributions for reconstructed D s -   (ie. B s decay)

24. B s  D s  Decay

25. Interference via B d 0 B d 0 mixing and decay LHC-B Events on tape J/        : 340k J/     e + e   : 183k L=1.5x10 32, 1 year =10 7 s, BR x (  e BR) =2.1x10 -5  recon  0.3,  tag  0.4 Reconstructed and tagged events=55k/year Measure decay asymmetry : N(B 0  J/  s 0 )(t) - N(B 0  J/  s 0 )(t) N(B 0  J/  s 0 )(t) + N(B 0  J/  s 0 )(t)  N b (t) - rN b (t) = a sin(  m t) N b (t)+ rN b (t) d a : fitted parameter sin 2  a / (1-  r=B d /B d tagged ratio (found from control sample)  =wrong tag fraction=0.290 (  0.00   And  sin  ) = 0.023 (statistics dominated) Sin 2  from B  J/  s 0

26. B  J/  s 0   J/     s 0    d     e + e 

27. LHC-B Events on tape : 110k L=1.5x10 32, 1 year =10 7 s, BR=2x10 -5 NB  recon  0.3,  tag  0.4 Reconstructed and tagged events=14k/year Measure decay asymmetry : N b (t) - rN b (t) = a cos(  m t) + b sin(  m t) N b (t)+ rN b (t) d d a, b fitted parameters (if no penguin, a=0) r=B d /B d tagged ratio (found from control sample) Background : Predominantly B d  K  B s  K  B s  K  Particle ID with RICH is vitally important If a=0, then : sin 2  = b/(1-   =wrong tag fraction=0.260 (  0.00   And  sin  ) = 0.039 (statistics dominated) Sin 2  from B 

29. 4 channels : B s  D s - K +, B s  D s + K - B s  D s + K -, B s  D s - K + Reconstructed and tagged events=3000/year Measure decay time evolution for B s, B s  D s - K + N b,b  t)  exp(-t/  s ) (cosh(  s /2 t)  A sinh(  s /2 t)  a cos(  m s t)  b sin(  m s t)) Measure decay time evolution for B s, B s  D s + K - Coefficients a, b  a’, b’ a, b, a’, b’ fitted parameters b, b’ give sin  Sin   from B  D s K Background to B s  D s K is B s  D s  Mass resolution  m =8.5 MeV and particle ID (RICH) vital.

30. Measure 6 relative branching fractions B d  D K*, D K*, D CP K* LHC-B  sin 2  ) = 0.14 - 0.24 (  dependent) Small CP violation in B s  J/   s /B s time-dependent asymmetry. Reconstruct 44k events with a tag. LHC-B  sin 2  ) = 0.02 (x s =25) Sin   from B s  J/  Sin 2   from B d  DK * Error on  depends on  x s … eg. 10 o  o, 80 o  o LHC-B  ) = 6 o - 16 o (This  measurement is unique to 2nd generation hadron-machine dedicated CP experiments) (600, 200, 50 events/year per channel)

31. LHC-B CP Reach Summary : One year’s running at 1.5 x 10 32 cm -2 s -1  (sin2  ) assumes penguin contribution known, and BR(B d         x   All measurements are statistics, not systematics, limited. Table is based on LoI (Summer 1995). Expect improvement with new L1 trigger.

32. LHC provides an opportunity to study CP (and other physics) in B-decay with very high statistics LHC-B: Optimized Forward Detector - Flexible, efficient, robust triggers - Particle ID - Excellent decay-time precision CKM-PHYSICS: Angles and sides of Unitarity Triangle overconstrained through measurements of  '  x s. Different decay channels, triggers, tags allow redundancy and control of systematics “LOW” Luminosity: - LHC-B can “choose”: L LHCB = 1.5 x 10 32 cm -2 s -1 - No Pile-up - Exploit initial (& subsequent) LHC running End 1995 : LoI approved Feb 1998 : Technical Proposal submitted 2005 : Beam (Day 1 experiment) LHC-B can run for MANY YEARS at optimal luminosity to study CP-violation SUMMARY