1. 27/4/2006UK SuperB Factory Workshop1 The LHCb Perspective Jim Libby – University of Oxford

2. 27/4/2006 UK SuperB Factory Workshop 2 Outline Physics goals of SuperB and LHCb (almost) identical  Indirect search for New Physics in heavy flavour decay  In particular CP violating and rare B decays Is there a synergy with a Super B factory?  Synergy to symbiosis LHCb detector and status LHCb core programme  Comparison to SuperB An upgraded LHCb Conclusions

3. 27/4/2006 UK SuperB Factory Workshop 3 Symbiosis-living together In symbiosis, at least one member of the pair benefits from the relationship The other member may be:  injured  relatively unaffected  may also benefit ( = mutualism)

4. 27/4/2006 UK SuperB Factory Workshop 4

5. 27/4/2006 UK SuperB Factory Workshop 5 Requirements for flavour physics at the LHC Triggering:  6 in 1000 inelastic pp collisions at 14 TeV contain a bb pair  Average of 1 interaction/bunch crossing (40 MHz)  Reduce event rate for mass storage at 2 kHz Also require standard B physics tools  Vertexing  Particle identification  Good invariant mass resolution  Neutral reconstruction  Flavour tagging  A large number of bb events!

6. 27/4/2006 UK SuperB Factory Workshop 6 100  b 230  b Pythia production cross section Acceptance and luminosity In the forward region at LHC the bb production cross section is large  All types of B hadron LHCb uses the forward direction  4.9 >  >1.9  Both hadrons containing the b & b quarks are likely to be within the acceptance  B hadrons are moving with considerable momentum ~100 GeV/c Design luminosity L =2×10 32 cm -2 s -1  Maximises number of single interactions 10 12 B hadrons in 10 7 sec = 1 LHC year  ptpt

7. 27/4/2006 UK SuperB Factory Workshop 7 LHCb detector Muon Detector Tracking stations Trigger Tracking proton beam interaction region

8. 27/4/2006 UK SuperB Factory Workshop 8 LHCb cavern snapshot Muon shielding and electronics tower HCAL and ECAL modules RICH 2 Magnet – mapped RICH 1 - photo-detector magnetic shielding WILL BE READY FOR 2007 PILOT RUN

9. 27/4/2006 UK SuperB Factory Workshop 9 LHCb trigger First level hardware trigger  High p t hadrons, leptons and photons  Veto multiple interactions If event passes 1 st level all sub-detector data readout at 1 MHz to Higher Level Trigger farm  Adaptable software trigger  Fast VELO tracking to identify high impact parameter tracks  Match to high p t objects that fired first level 2 kHz output rate  Inclusive D * (300 Hz) – PID calibration and charm physics  Dimuon (600 Hz) – B→J/ψX with no impact parameter selection  Inclusive b→μ (900 Hz) – data mining and calibrations  Exclusive B decay (200 Hz) – physics channels

10. 27/4/2006 UK SuperB Factory Workshop 10 Tracking and vertexing  Proper time resolution   ~ 40 fs B s  D s h (h=π,K) B s  J/    Essential for time dependent B s measurements BsDsBsDs Channelσ(m B ) [MeV/c 2 ] B s   18 Bs Ds Bs Ds  14 B s  J/   16 B s  J/   (m J/ψ constrained) 8 BsDsBsDs All performance results with PYTHIA+GEANT4 simulation unless otherwise stated

11. 27/4/2006 UK SuperB Factory Workshop 11 Particle ID No RICH Kaon ID: ~88% Pion mis-ID: 3%  Low momentum – Kaon flavour tag (b→c→s)  High momentum – Background rejection for exclusive B decay reconstruction ππ hypothesis B→h + h -

12. 27/4/2006 UK SuperB Factory Workshop 12 Flavour tagging  Most powerful tag is opposite kaon (from b  c  s)  Combined  D 2 ~ 6.9% (B s ) or 4.8% (B 0 )  Recent multivariate approach ~9% for B s Q vtx BsBs B0B0 D l-l- K–K– K+K+ PV SV Tag  D 2 =  (1–2w) 2 μ±μ± 1.0% e±e± 0.4% K±K± 2.4% Jet/vertex charge1.0% Same side K ± (B s )2.1% Cut

13. 27/4/2006 UK SuperB Factory Workshop 13 LHCb Physics Programme Sampler B s mixing phase and lifetime difference  B s  J/  Several routes to γ  B s → D s K – tree only  B d → π + π - and B s → K + K - – tree and penguin  B - →D 0 K - and B 0 →D 0 K * (892) 0 – tree and D0 mixing α with B d → ρπ Rare decays  B s(d)  μ + μ -  B d  K * (892) 0 μ + μ -  B d  K * (892) 0 γ and B s   γ

14. 27/4/2006 UK SuperB Factory Workshop 14 B s analogue of B d →J/ψK s measures the B s mixing phase   s = –arg(V ts 2 ) = –2  2 ~ –0.04 in SM Large CP asymmetry would signal Physics Beyond SM J/  is not a pure CP eigenstate  Admixture of 2 CP even and 1 CP odd amplitudes Need to fit angular distributions of decay final states as function of proper time  Requires external  m s from B s →D s π  Exploits excellent proper time resolution 1 year predictions with  m s = 20 ps -1  125k events with B/S~0.5   (sin  s )~0.031   (  s /  s )~ 0.011 3σ SM sensitivity to sin  s after 5 years  Also add pure CP states B s  J/  η (‘)  s and  s from B s  J/ 

15. 27/4/2006 UK SuperB Factory Workshop 15  from B s  D s K 2 amplitudes (b→c and b→u) of same magnitude (~λ 3 ) interfere via B s mixing  insensitive to new physics  large interference effects expected 2 time dependent asymmetries  B s (B s )  D - s K + and B s (B s )  D + s K - 5400 signal events/year with B/S<1 PID and mass resolution reduce contamination from B s  D s π ~ 10% BsDsKBsDsK BsDsBsDs

16. 27/4/2006 UK SuperB Factory Workshop 16 D s K asymmetries (5 years,  m s =20 ps –1 ) Ds–K+Ds–K+ Ds+K–Ds+K–  from B s  D s K Fit 2 time-dependent asymmetries  phase of D  s K  =  s )  phase of D  s K  =  s )   s from B s → J/ψ  to extract Δ and γ 1 year sensitivity:  Assuming Δm s = 20 ps -1 and - 20°<Δ<20°   ~ 14°  Statistically limited 8-fold ambiguities in  can be resolved  If  s large enough, or  B 0 →D  and U-spin symmetry

17. 27/4/2006 UK SuperB Factory Workshop 17  from B      and B s  K  K  Large penguin contributions in both decays  Sensitive to New Physics Measure time-dependent CP asymmetry for B      and B s  K  K   A CP (t) = A dir cos(  mt) + A mix sin(  mt)  A dir and A mix depend on , mixing phases, and ratio of penguin-to-tree amplitudes (d e i   Exploit “U-spin” symmetry (d  s)  d  = d KK and   =  KK  Mixing phases from golden modes  4 measurements and 3 unknowns, 1 year yields and sensitivity:  26k B      and 37k B s  K  K ,   °  (  ) d B s  K  K  (95% CL) B       (95% CL) B d/s  /K R.Fleischer, Phys.Lett. B459, 306 (1999)

18. 27/4/2006 UK SuperB Factory Workshop 18 Dunietz variant of Gronau, London and Wyler method Exploits interference between two colour-suppressed diagrams Measure 6 decay rates: B 0  D 0 (K ,  K,KK)K* 0 + CP conjugates Allows  and other parameters to be extracted without flavour tagging or proper time determination  8 0 precision on γ with one year’s data  from B 0  D 0 K* 0 A 1 = A(B 0  D 0 K* 0 ): b  c transition, phase 0 A 2 = A(B 0  D 0 K* 0 ): b  u transition, phase  +  A 3 =  2 A(B 0  D CP K* 0 ) = A 1 +A 2, because D CP =(D 0 +D 0 )/  2 = strong phase

19. 27/4/2006 UK SuperB Factory Workshop 19 B  →DK  Similar to B 0 -two interfering tree processes Now one diagram colour suppressed  – b→u, b→c interference r B – the ratio in magnitude of two diagrams (0.1 – 0.2) δ B – a CP conserving strong phase difference Look for decays common to D o and D o to access interference effects, which depend on 3 parameters: 1.Cabbibo favoured self-conjugate decays e.g. K s , K s KK, KKππ Preliminary K s  studies 6k events/year with B/S ~O(1) 2.Cabbibo favoured/doubly Cabbibo suppressed modes e.g. K , K  One year γ sensitivity 5 0 Two types of D 0 decay understudy :

20. 27/4/2006 UK SuperB Factory Workshop 20 Angle  from B d   0  –  + decays  Dalitz plot analysis (Quinn Snyder method) B d  0  –  + selection based on multivariate analysis Use resolved and merged  0 Expect 14k events per year, B(bb)/S < 1  Toy MC study: 11-parameter likelihood fits performed in time- dependent Dalitz space B/S = 0.8 (flat and resonant bkg) 0000 –+–+ +–+– m2(0+)m2(0+) m2(0–)m2(0–) Combined discriminant variable 1 year  (  ) ~10°  gen =106°

21. 27/4/2006 UK SuperB Factory Workshop 21 s = (m  ) 2 [GeV 2 ] A FB (s) for B 0  K *0  Rare decays with leptons B s →μ + μ -  BR ~ 3.5  10 –9 in SM, can be strongly enhanced in SUSY  LHCb has prospect for significant measurement ~30 events/year Full simulation: 10M incl. bb events + 10M b , b  events (all rejected) B→K *0 μ + μ -  A FB very sensitive to new physics  Expect 4.4k events in 1 year  B/S < 2.5  In 5 years 13% sensitivity to s(A FB =0)

22. 27/4/2006 UK SuperB Factory Workshop 22 B 0 → K 0*  and B s →  B→K 0*  expected direct CP violation A cp <0.01  35k/year B/S>0.7 B→   TDCPV zero in SM  Sensitive to same new physics as TDCPV B 0 → K *0 (K 0 s π)   Selection optimises proper time resolution   k/year B/S>2.5 Sensitivity studies in progress  m ~ 64 MeV/c 2 B→ K  B s → KK    ~ 60 fs m Kπ [GeV]

23. 27/4/2006 UK SuperB Factory Workshop 23 …and much, much more Other CP measurements, for example  sin 2β  sin (2β+γ) with B→D * π  α with B→ρ 0 ρ 0   s with B s    (gluonic penguin) Other rare decays e.g B s   μμ Other areas to be explored  B baryons  B c physics – 14k/year in B c → J/ψ π  Charm physics (300 Hz of D *+ →D 0 (h + h - )π + ) Control samples for control of systematic uncertainties

24. 27/4/2006 UK SuperB Factory Workshop 24 Comparison to Super B This was shown by N. Katayama at FCPC a couple of weeks ago At first glance I’m working on the wrong experiment! But:  LHCb ~2010  SuperB ~2020  Some missing LHCb info SuperB (50 ab -1 ) LHCb (2 fb -1 )

25. 27/4/2006 UK SuperB Factory Workshop 25 Comparison to Super B Added some information on several modes Scaled LHCb to 10 fb -1 luminosity (2015) and reordered the measurements Symbiosis! Inclusive/ ν No IP BsBs Com mon

26. 27/4/2006 UK SuperB Factory Workshop 26 Possible LHCb upgrades Simulation studies indicate we can run at 5×10 -32 cm -2 s -1 and gain in statistics  Particularly dimuons Bo+-Bo+- B S  B S  J/  BSDSK-BSDSK- Vertex detector will be replaced because of radiation damage  Very radiation hard technologies would allow detectors to be closer to the beam  Pixels could be used in 1 st level of the trigger to improve selection of hadronic modes ECAL inner region replaced by PbWO 4 to improve neutral performance

27. 27/4/2006 UK SuperB Factory Workshop 27 Conclusions LHCb will be ready for data taking next year A large number of measurements will be made during the lifetime of the experiment  Largely complimentary to Super B programme Performance might be enhanced with upgrades to vertexing, triggering and electromagnetic calorimetry

28. 27/4/2006 UK SuperB Factory Workshop 28 sin(2  ) from B 0  J/  K S  “gold-plated” decay channel at B-factories for measuring the B d - B d mixing phase  needed for extracting γ from B  π π and B s  K K, or from B  D * π  in SM ~0, non-vanishing value O (0.01) could be a signal of Physics Beyond SM A CP (t) (background subtracted) LHCb One of the first CP measurements at LHC: demonstrate CP analysis performance study tagging systematics Expected sensitivity: LHCb: 240k signal events/year   stat (sin(2  )) ~ 0.02 (1year, 2fb -1 ) (   0.6°) Search for direct CP violating term…

29. 27/4/2006 UK SuperB Factory Workshop 29 B - →D 0 (K +  - )K - Both D 0 and D 0 → K +  - : Doubly Cabbibo suppressed Cabbibo favoured For these decays the reversed suppression of the D decays relative to the B decays results in much more equal amplitudes → big interference effects Counting experiment Interference depends on 5 parameters :  From the B decays γ, r B and δ B  r D K  – the ratio in magnitude of two D decay processes Well measured (PDG value 0.060)  δ D K  – a CP conserving strong phase difference B - →D 0 K - (colour favoured) then : B - →D 0 K - (colour suppressed) then : Atwood, Dunietz and Soni

30. 27/4/2006 UK SuperB Factory Workshop 30 B - →D 0 (K +  - )K - Have 4 B ± →D(K  )K ± rates we can measure: Two rates are favoured (1) and (3) Two rates are suppressed (2) and (4) – but suppressed rates have O(1) interference effects as r B ~ r D Taking the relative rates have more unknowns than equations – need information from other decays eg. D → K  or the CP eigenstates KK,  (r D KK =1,  D KK =0) (1)(1) (2)(2) (3)(3) (4)(4)

31. 27/4/2006 UK SuperB Factory Workshop 31 ADS 1 year sensitivity studies Event yields  60,000 favoured  2,000 suppressed B/S = 0.5 for both Fit robust over range of strong D decay strong phases B/S Kπ 0125 B/S Kπππ 03.9 0 4.0 0 4.1 0 14.6 0 4.8 0 5.0 0 2 5.1 0 5.3 0 5.5 0 55.6 0 5.9 0 6.0 0 6.9 0 1000 toy experiments-no background