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The LHCb Experiment

The LHCb Experiment. The search for New Physics The LHCb experiment LHCb start-up and the physics programme. Current Status. First generation B factories (BaBar@PEPII and Belle@KEKB), together with CDF/D0@Tevatron, have a spectacular physics record. PDG 2000. PDG 2006.

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The LHCb Experiment

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  1. The LHCb Experiment • The search for New Physics • The LHCb experiment • LHCb start-up and the physics programme

  2. Current Status First generation B factories (BaBar@PEPII and Belle@KEKB), together with CDF/D0@Tevatron, have a spectacular physics record PDG 2000 PDG 2006

  3. Tests of CKM picture • Unitarity triangle from tree-level processes only • Observe h  0 CP violation in CKM matrix is at work ! • Tree processes not affected by New Physics • Constraint must be satisfied by any New Physics • Requires a precision measurement of g

  4. UT sides Measurement (bccs) 2.3s Current tests indicate that the SM description of CP is successful and any New Physics will appear as a small correction Tests of CKM picture • Allowed region from CP conserving quantities • Compared to region from CP violating quantities • CKM phase is dominant • New Physics is not excluded

  5. New Physics • SM cannot be ultimate theory • low-energy effective theory of a more fundamental theory at a higher energy scale (TeV range) • Hierarchy problem: New Physics required to cancel radiative corrections to the Higgs mass but leave the SM EW predictions unaffected • How can New Physics be discovered and studied ? • NP models introduce new particles which could be produced and discovered as real particles at the LHC appear as virtual particles in loop processes  observable deviations from the SM expectations in flavour physics and CP

  6. New Physics ? ? Penguin diagram Box diagram New Physics • NP needs to have a flavour structure to provide the suppression mechanism for FCNC processes already observed. • Once NP is discovered it is important to measure this flavour structure (including new phases) and to distinguish between the NP models. • Direct and Indirect approaches are very complementary

  7. With NP allowed (SM) New Physics in B0 Mixing • Use a model independent parameterization of New Physics in B0 (and K0) mixing • includes only SM box diagrams • includes NP contributions as well • Four independent observables • One additional parameter for K0 mixing NP in D0 mixing is neglected Reiterates need for precision measurement of g 5 NP parameters

  8. New Physics in B0 Mixing SM SM Non-zero central value of fd from difference in SM fit between angles (sin2b) and sides (Vub) CBs constrained more than CBd from CDF measurement of Dms Need to measure Bs mixing phase fs

  9. Search for New Physics • Measure processes very suppressed in SM • CP in Bs mixing ( in SM) • BsJ/F • Radiative and very rare B decays • BdK*g, BsFg, Bd K*mm, Bd,s mm • Rare D decays and D0 mixing • Lepton flavour violating decays • Precision measurements of CKM elements • Bs oscillations • Compare pure tree level processes with processes sensitive to NP • Sin2b BdJ/Ks vs BdFKs • g BDK vs Bpp/KK • Measure all angles and sides in many different ways. Any inconsistency will be evidence for NP • Requires clean and improved theory predictions

  10. Interaction point The LHCb Experiment • LHCb is dedicated to the Search for New Physics in CP violation and Rare B decays • LHCb Collaboration: 14 countries, 47 institutions, ~600 people

  11. Final focus Interaction point 8 LHC

  12. RICH1 VELO Trackers Calorimeters Muon RICH2 Magnet

  13. b production at the LHC In the forward region (4.9 > h >1.9): • bb cross-section large (~230 mb) • Luminosity ℒ=2x1032 cm-2s-1 1012 B hadrons in 107 sec • All species of B hadrons produced (B, Bd, Bs, Bc, b-baryons) • B’s have large momentum <pB>acc ~ 80 GeV/c Mean flight path of B’s ~7mm. • bb production correlated and sharply peaked forward-backward.

  14. L0 efficiency (%) Trigger • Trigger crucial to the successful operation of LHCb • B fraction is only ~1% of inelastic cross-section. • Br’s of interesting B decays <10-4 • Properties of minimum bias similar to B’s • First Level Trigger (L0) • Hardware (custom boards, 4ms latency) • Largest ET hadron, e(g) and (di-)m • Pile-up system (not for m trigger) • Reduces 10 MHz inelastic rate to 1MHz

  15. Trigger • High Level Triggers • Software trigger run on CPU farm (1800 nodes) • Access to all detector data • Use more tracking information to re-confirm L0 decision • Full event reconstruction; inclusive and exclusive selections tuned to specific final states • Output rate 2 kHz, 35 kB per event Total 2000 Hz

  16. Flavour Tagging

  17. RF foil Silicon sensors interaction point ~1 m pile-up veto VELO • 21 VELO stations (r and f silicon sensors) • Placed in a secondary vacuum vessel • 3cm separation, 8mm from beam • Separated by a 300 mm of Al RF foil • Detector halves retractable for injection

  18. RF foil Vacuum vessel Beam’s eye view VELO

  19. VELO module production VELO • Status • 70% modules produced • One half VELO complete • 42 VELO modules • r and f layer • n+n type • 2048 strips/sensor • Strip pitch 40 mm to 100 mm

  20. Outer Tracker Straw tubes Inner Tracker Silicon strips 2% of area 20% of tracks Trigger Tracker Silicon strips pT information for trigger Tracking

  21. Outer Tracker Inner Tracker Trigger Tracker Tracking Status: • Module production ~finished (IT end Feb) • Installation: OT finish Mar 07 IT/TT Mar-Jul 07

  22. Magnet B/B = 0.03% By /T Peak field on axis: 1.1 T Field integral: 4 Tm (over 10 m) z /cm

  23. Impact Parameter Resolution 1/pt distribution for B tracks Event display Magnet VELO TT T Stations Tracking performance • Vertex resolution • ~10 mm in x,y; 50 mm in z • Proper time resolution ~ 40 fs • B Mass resolution ~ 15 MeV • Track fit: bi-directional Kalman fit • Tracking efficiency >95% • Ghost rate <7% p > 12 GeV Momentum Resolution p distribution for B tracks

  24. RICH Detectors • Particle ID: p~1-100 GeV provided by 2 RICH detectors RICH2 RICH1

  25. Aerogel 22 tiles RICH Detectors • 3 radiators: RICH1 Aerogel (2-10 GeV), C4F10 (10-60 GeV) RICH2 CF4 (16-100 GeV) • Status: RICH2 installed RICH1 finish installation Aug 2007

  26. 80mm 120mm Quantum Efficiency contract spec. typical 23.3 % RICH Photodetectors • 484 Hybrid Photo Detectors (HPD’s) HPD production expected to be completed March 2007

  27. K  K or p Efficiency(%) RICH1 RICH2 pK or p p (GeV) RICH Performance Full MC simulation using “global” fit to Cherenkov rings Averages: K→ K,p eff: 83.1± 0.1% p → K,p misID: 5.85± 0.03% High Level Trigger D* stream D*→D0(K) RICH independent Efficiency D* MC Truth p/K selected from D* sample (no MC truth)

  28. Calorimeters SPD/PS: Pb/Scint., 2.5 X0 ECAL: Pb-Scint. Shashlik, 25 X0 HCAL: Fe/Scint. tiles, 5.6 l0 ECAL HCAL

  29. e Efficiency = 53% for B0p+p-p0 Merged Resolved Transverse energy (GeV) p0 reconstruction Resolved π0 2 isolated photons Example: Time dependent Dalitz plot analysis of B0 rp p+p-p0 14k signal events in 2 fb-1  s(a) = 10o Merged π0 Single ECAL cluster s ~15 MeV s~10 MeV

  30. M5 Muons • 1368 MWPCs (M2-M5, outer M1 region) • 24 3-GEMs (inner M1 region) 3-GEM MWPC

  31. Muons • Status: production finished; installation and commissioning in progress • ODE electronics under commissioning Fixing chambers on the inner edge of wall requires expert climbers

  32. Muon system Tracking system Bsμμ μ Muon ID • Muons at L0 trigger (pt > 1 GeV): AND of hits in the 5 stations Distance of closest hit (pad unit) DC06 performance: ε(muons) = 90.5  0.1 % Total misID = 1.78  0.1 % misID for hadrons = 0.52  0.01 % Fraction of decays in flight = 72% misID for decays in flight = 43.1 0.2 %

  33. LHCb Status • LHCb is confident that the experiment will be ready for data-taking in March 2008 • All major and heavy structures are installed • OT, RICH2, ECAL and HCAL are very close to be ready for a “global” commissioning • RICH1, VELO, IT and TT needs still some (but short) installation work. • Installation of Muon system and PS/SPD cabling will still continue for a few months • LHCb will take physics data in 2008 with a complete detector

  34. LHCb startup programme • 2008: early phase • Complete commissioning of detector and trigger at s=14 TeV • Calibrate momentum, energy and particle ID • Start first physics data taking, assume ~ 0.5 fb–1 • Establish physics analyses, understand performance • Look asap for New Physics with measurements competitive at low lumi • 2009–20xx: stable running • Stable running, assume ~ 2 fb–1/year • Develop full physics program • Exploit statistics, work on systematics

  35. ? ? MSSM Very Rare B Decays: Bs +– • Very rare loop decay, sensitive to New Physics: • BR ~3.510–9 in SM, can be strongly enhanced in SUSY • Current 90% CL limit from CDF+D0 with 1 fb–1 is ~20 times SM • Main issue is background rejection • With limited MC statistics, indication that main background is b, b

  36. Limit at 90% C.L. (only bkg is observed) Integrated luminosity (fb–1) BR (x10–9) Expected final CDF+D0 Limit Uncertainty in bkg prediction SM prediction Integrated Luminosity (fb-1) Very Rare B Decays: Bs +– LHCb Sensitivity (signal+bkg is observed) BR (x10–9) 5 SM prediction 3 Integrated Luminosity (fb-1) 2 fb–1 3 evidence of SM signal 10 fb–1 >5 observation of SM signal 0.05 fb–1 overtake CDF+D0 0.5 fb–1 exclude BR values down to SM

  37. AFB(s), theory + B0 q K* – s = (m)2 [GeV2] AFB(s), fast MC, 2 fb–1 s = (m)2 [GeV2] Rare B Decays: B0 K*0m+m- • Suppressed by loop decay, BR ~1.210–6 Forward-backward asymmetry AFB(s) in the  rest-frame is sensitive probe of New Physics • Sensitivity • 7.7k signal events/2fb–1, Bbb/S = 0.4 ± 0.1 • After 2 fb–1, zero of AFB(s) to ±0.52 GeV2  determine ratio of Wilson coefficients C7eff/C9eff with 13% stat error (SM)

  38. ? Bs Mixing Phase s with bccs • Bs mixing phase, fs is very small in SM sSM= –0.037 ± 0.002(UT fits) • Could be much larger if New Physics in the box • Golden bccs mode is Bs J/: • Angular analysis needed to separate CP-even and CP-odd contributions • Expect ~130k BsJ/() signal events/2fb–1(before tagging), S/Bbb= 8 • Add pure CP modes (J/(’), c, DsDs) • No angular analysis, smaller statistics • Sensitivity: Statistical sensitivities on s for 2 fb–1 stat(s) = 0.044 with 0.5 fb–1 [LHCb-2006-047]

  39. ? Constraints on New Physics in Bs mixing from s measurement • New Physics in Bs mixing amplitude parametrized with and • Can exclude already significant region of allowed phase space with the very first data (2008) In April 2006, including CDF’s first measurement of ms >90% CL >32% CL >5% CL from hep-ph/0604112 After LHCb measurement of s with (s)= ±0.1 (~ 0.2 fb–1) courtesy Z.Ligeti

  40. Vcs* Vcb Vtb Vts* bsss hadronic penguin decays Currently explored at B factories with time-dependent analyses of tagged decays to CP eigenstates such as B0  KS, etc. • Expect same result (i.e. sin2) as b  ccs tree decays like B0  J/KS if only SM Decay phase = 0 Decay phase ~ 0 in SMDecay phase ≠ 0 if NP total phase = (mixing phase 2) + (decay phase)

  41. ? fNP bsss hadronic penguin decays • Also accessible at LHCb • Best channel is Bs  • CP violation < 1% in SM (Vts enters both in mixing and decay amplitudes) • significant CP-violating phase can only be due to New Physics • Angular analysis required • 4k signal events per 2 fb–1 (if BR=1.410–5), 0.4 < B/S < 2.1 @90%CL • After 10 fb–1 • ± 0.042 from Bs  • ± 0.14 from B0  KS (4k signal events, B/S < 2.4 @ 90% CL)

  42. With PID With PID  invariant mass KK invariant mass CKM angle g Many ways to measure g at LHCb using various methods: • Tree-level processes • Bs DsK s(g) ~14o per 2fb-1 • Bd D(*)p • B, Bd D(*)K(*), with D0 decaying to: 2 bodies: pK, KK, pp best modes offer s(g) = 5-10o 3 bodies: KS pp, KS KK, KS Kp each per 2 fb-1 4 bodies: Kppp, KKpp • Penguin processes • Bd+– & Bs  K+K– • U-spin approach s(g) ~ 4o per 2 fb-1 (7-10o with 20% U-spin violation) Expect s(g)=2-3o with 10 fb-1

  43. loops (2006) CKM angle g  from BDK at LHCb (10 fb–1) Two possible scenarios

  44. LHCb at L=10fb-1 Summer 2006 Effect of LHCb on UT

  45. Sensitivities to CKM angle g Signal only

  46. colour-allowed colour-suppressed  from B±  DK± Weak phase difference =  Magnitude ratio = rB ~ 0.08 • “ADS+GLW” strategy: • Measure the relative rates of B–  DK–andB+  DK+ decays with neutral D’s observed in final states such as: K–+andK+–, K–+–+andK+–+–, K+K– • These depend on: • Relative magnitude, weak phase and strong phase between B–  D0K– and B–  D0K– • Relative magnitudes (known) and strong phases between D0  K–+ and D0  K–+,and between D0  K–+–+ and D0  K–+–+ • Can solve for all unknowns, including the weak phase : () = 5–15 with 2 fb–1 (depending on the strong phases)

  47. CKM 2008 (pre-LHCb) Improvements due to • Bd, B sector: B-factories (Babar/Belle) • Assume ℒ = 2 ab-1 at the (4S) • ()  6.5°, ()  6.5°, (sin2)  0.017 • Bs sector: Tevatron (CDF/D0) • Assume (2x) 6 fb-1 • (s)  0.2, (s/s)  0.04, (ms)  0.5% • Lattice QCD prospects Courtesy V.Vagnoni CKM 2006, Nagoya

  48. LHCb Sensitivities with 2fb-1

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