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The LHCb Perspective

The LHCb Perspective. Jim Libby – University of Oxford. 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

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The LHCb Perspective

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  1. The LHCb Perspective Jim Libby – University of Oxford 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 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) UK SuperB Factory Workshop

  4. 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! UK SuperB Factory Workshop

  6. 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 > h>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=2×1032 cm-2s-1 • Maximises number of single interactions • 1012B hadrons in 107 sec = 1 LHC year Pythia production cross section pt 100 mb 230 mb h UK SuperB Factory Workshop

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

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

  9. LHCb trigger • First level hardware trigger • High pthadrons, leptons and photons • Veto multiple interactions • If event passes 1st 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 ptobjects 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 UK SuperB Factory Workshop

  10. Tracking and vertexing BsDs All performance results with PYTHIA+GEANT4 simulation unless otherwise stated • Proper time resolution ~ 40 fs • BsDsh (h=π,K) • Bs J/  • Essential for time dependent Bs measurements BsDs UK SuperB Factory Workshop

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

  12. l- K– Qvtx D B0 Bs SV PV K+ Flavour tagging • Most powerful tag is opposite kaon (from bcs) • Combined D2 ~ 6.9% (Bs) or 4.8% (B0) • Recent multivariate approach ~9% for Bs Cut UK SuperB Factory Workshop

  13. LHCb Physics Programme Sampler • Bs mixing phase and lifetime difference • BsJ/ • Several routes toγ • Bs→ DsK – tree only • Bd→π+π-andBs→ K+K- – tree and penguin • B-→D0K- and B0→D0K*(892)0 – tree and D0 mixing • αwithBd→ρπ • Rare decays • Bs(d)μ+μ- • BdK *(892)0μ+μ- • Bd K *(892)0γandBs γ UK SuperB Factory Workshop

  14. fs and DGs from BsJ/ • Bs analogue of Bd→J/ψKs measures the Bs mixing phase • fs = –arg(Vts2) = –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 msfrom Bs→Dsπ • Exploits excellent proper time resolution • 1 year predictions with ms= 20 ps-1 • 125k events with B/S~0.5 • (sin s)~0.031 • (s /s)~ 0.011 • 3σ SM sensitivity to sin safter 5 years • Also add pure CP states BsJ/η(‘) UK SuperB Factory Workshop

  15. BsDsK BsDs gfrom Bs DsK • 2 amplitudes (b→c and b→u) of same magnitude (~λ3) interfere via Bsmixing • insensitive to new physics • large interference effects expected • 2 time dependent asymmetries • Bs (Bs)  D-sK+andBs (Bs)  D+sK- • 5400 signal events/year with B/S<1 • PID and mass resolution reduce contamination from Bs Dsπ ~ 10% UK SuperB Factory Workshop

  16. DsK asymmetries (5 years, ms=20 ps–1) Ds–K+ Ds+K– g from Bs DsK • Fit 2 time-dependent asymmetries • phase of D-sK+= D + (g + fs) • phase of D+sK-= D- (g + fs) • sfrom Bs → J/ψ to extract Δ and γ • 1 year sensitivity: • Assuming Δms= 20 ps-1 and -20°<Δ<20° • s(g) ~ 14° • Statistically limited • 8-fold ambiguities in g can be resolved • If DGs large enough, or • B0→Dp and U-spin symmetry UK SuperB Factory Workshop

  17. B   (95% CL) p/K p/K Bd/s d Bd/s p/K p/K Bs KK(95% CL) g()  from B and BsKK R.Fleischer, Phys.Lett. B459, 306 (1999) • Large penguin contributions in both decays • Sensitive to New Physics • Measure time-dependent CP asymmetry for B and Bs KK • ACP(t) = Adir cos(Dmt) + Amixsin(Dmt) • Adir and Amix depend on g, mixing phases, and ratio of penguin-to-tree amplitudes (d eiq) • Exploit “U-spin” symmetry (ds) • dpp = dKK and qpp = qKK • Mixing phases from golden modes • 4 measurements and 3 unknowns, 1 year yields and sensitivity: • 26k B and 37k BsKK, • s(g) ~ 5° UK SuperB Factory Workshop

  18. A1 = A(B0 D0K*0): bc transition, phase 0 A2 = A(B0 D0K*0): bu transition, phase + A3 = 2 A(B0 DCPK*0) = A1+A2, because DCP=(D0+D0)/2 gfrom B0 D0K*0 • Dunietz variant of Gronau, London and Wyler method • Exploits interference between two colour-suppressed diagrams • Measure 6 decay rates: B0D0(Kp,pK,KK)K*0 + CP conjugates • Allows g and other parameters to be extracted without flavour tagging or proper time determination • 80 precision on γwith one year’s data = strong phase UK SuperB Factory Workshop

  19. B →DK Similar to B0-two interfering tree processes Now one diagram colour suppressed Look for decays common to Do and Do to access interference effects, which depend on 3 parameters: •  – b→u , b→c interference • rB – the ratio in magnitude of two diagrams (0.1 – 0.2) • δB – a CP conserving strong phase difference Two types of D0decay understudy: • Cabbibo favoured self-conjugate decays e.g. Ks, KsKK, KKππ • PreliminaryKsstudies6k events/yearwith B/S ~O(1) • Cabbibo favoured/doubly Cabbibo suppressed modes e.g. K, K • One year γsensitivity 50 UK SuperB Factory Workshop

  20. m2(0–) +– 00 –+ m2(0+) Combined discriminant variable Angle from Bd 0–+ decays • Dalitz plot analysis (Quinn Snyder method) • Bd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) gen=106° 1 year () ~10° UK SuperB Factory Workshop

  21. AFB(s) for B0K*0 s = (m)2 [GeV2] Rare decays with leptons Bs→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*0μ+μ- • AFB very sensitive to new physics • Expect 4.4k events in 1 year • B/S < 2.5 • In 5 years 13% sensitivity to s(AFB=0) UK SuperB Factory Workshop

  22. B0→ K0* g and Bs →f g sm~ 64 MeV/c2 B→ Kp g • B→K0* gexpected direct CP violation Acp<0.01 • 35k/year B/S>0.7 • B→fgTDCPV zero in SM • Sensitive to same new physics as TDCPV B0→ K*0(K0sπ)g • Selection optimises proper time resolution • 9.4k/year B/S>2.5 • Sensitivity studies in progress mKπ[GeV] st~ 60 fs Bs→ KK g 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→ρ0 ρ0 • s withBs   (gluonic penguin) • Other rare decays e.g Bs  μμ • Other areas to be explored • B baryons • Bc physics – 14k/year in Bc→ J/ψπ • Charm physics (300 Hz of D*+→D0(h+h-)π+) • Control samples for control of systematic uncertainties UK SuperB Factory Workshop

  24. Comparison to Super B SuperB (50 ab-1) LHCb (2 fb-1) • 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 UK SuperB Factory Workshop

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

  26. Bop+p- BSfg BSJ/yf BSDSK- Possible LHCb upgrades • Simulation studies indicate we can run at 5×10-32cm-2s-1 and gain in statistics • Particularly dimuons • 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 1st level of the trigger to improve selection of hadronic modes • ECAL inner region replaced by PbWO4 to improve neutral performance 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 UK SuperB Factory Workshop

  28. “gold-plated” decay channel at B-factories for measuring the Bd- Bd mixing phase • needed for extracting γfrom B  ππand Bs  K K, or from B  D*π • in SM ~0, non-vanishing value O(0.01) could be a signal of Physics Beyond SM sin(2) from B0J/ KS ACP(t) (background subtracted) 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) (s(b)~0.6°) Search for direct CP violating term… LHCb UK SuperB Factory Workshop

  29. B- →D0(K+p-)K- Atwood, Dunietz and Soni B-→D0K- (colour favoured) then : B-→D0K- (colour suppressed) then : • Both D0 and D0 → K+p- : 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, rB andδB • rDK – the ratio in magnitude of two D decay processes • Well measured (PDG value 0.060) • δDK – a CP conserving strong phase difference UK SuperB Factory Workshop

  30. Have 4 B± →D(Kp)K± rates we can measure: Two rates are favoured (1) and (3) Two rates are suppressed (2) and (4) – butsuppressed rates have O(1) interference effects as rB ~ rD Taking the relative rates have more unknowns than equations – need information from other decays eg. D → Kppp or the CP eigenstates KK, pp (rDKK=1, δDKK=0) (1) (2) (3) (4) B- →D0(K+p-)K- UK SuperB Factory Workshop

  31. ADS 1 year sensitivity studies 1000 toy experiments-no background • Event yields • 60,000 favoured • 2,000 suppressed • B/S = 0.5 for both • Fit robust over range of strong D decay strong phases UK SuperB Factory Workshop

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