Physics Motivation The Vertex Locator The Outer Tracker Tracking in HERA-B and LHCb LHCb Optimization

Transcription

1 b-physics: HERA-B and LHCb Marcel Merk (for Jo van den Brand) April 8, 22 Physics Motivation The Vertex Locator The Outer Tracker Tracking in HERA-B and LHCb LHCb Optimization

2 b b Physics What does LHCb offer in comparison to the B factories? s B factories HERA-B LHCb Υ(4S) 42 GeV 14 TeV σ bb /σ inel 1/ /16 N inel 16 Hz 1 MHz 13 MHz N bb 4 Hz 1 Hz 1 khz Produce factor 1 4 more b b events (rare decays!) B s physics in addition to B d physics A non trivial trigger environment! (Branching ratio s typical CP-channels: ) Both HERA-B and LHCb: Forward production of B particles with: average momentum 1 GeV average decay distance 1 cm Design of similar spectrometers with polar angle acceptance: 15mrad < θ < 25mrad...

3 Beam Pipe Photon Detector C4 F1 Electron Beam Proton Beam Planar Mirrors Spherical Mirrors 16 mrad HERA-B and LHCb Detectors HERA-B: LHCb:

4 HERA-B vs LHCb Event HERA-B LHCb

5 Tracking and Physics NIKHEF Activities: 11 staff, 2 post-docs, 8 graduate students HERA-B: (1 staff, 1 post-doc, 3 grad students) Outer Tracker & Track trigger commisioning Track & Vertex reconstruction A-dependence of J/ψ cross section B Cross section Upsilon production LHCb: Outer Tracker: ( 2 staff, 1 grad students) VELO: mechanics, electronics and pile-up detector: ( 4 staff, 1 grad students) Track Reconstruction and Detector Optimization: ( 1 staff, 1 post-doc, 2 grad students ) Grid Computing: ( 2 staff, 1 grad student) MC Performance studies with B s physics: B s D s π (x s ) B s D s K (γ) B s J/ψ φ (δγ)

6 A B s Physics Program B s Oscillations: m s : (R.Hierck, J.v.Tilburg) B s D s π + B s D + s π time & momentum resolution CP Violation: angle γ 2δγ: (R.Hierck, J.v.Tilburg) B s D s K + ; B s D + s K B s D + s K ; B s D s K + + particle ID new physics : angle δγ: (N.v.Bakel, S.Klous) B s B s J/ψ φ + angular analysis High statistics B d D nπ ππ ρπ γ detection V ub Good πk separation α V ts B s mixing Good decay time resolution B s D S K Good πk separation V ub V td γ V cb β γ V ts B d DK High statistics B d J/ψK S δγ B s J/ψφ

7 Physics Performance Common parameters in B s decays: m s, Γ s, Γ s Γ L s Γ H s, ω tag 1. From B s D s π data: (N = 35k/y) fit m s, Γ s, ω tag : Sensitivity up to: m s 6 ps 1 2. From B s D s K + data: (N = 2.4k/y) Use m s, Γ s, ω tag and fit γ 2δγ: In case m s = 2: 3. From B s J/ψ φ data: From the untagged sample: Use Γ s and fit Γ: In case Γ s /Γ s =.16: σ(γ 2δγ) 8 o σ( Γ s /Γ s ) =.5 (N = 11k/y) From the tagged sample: Use Γ s, m s, Γ s and fit δγ: (N = 44k/y) In case m s = 2: σ(δγ) =.15

8 OT stuff

9 VELO stuff

10 grid stuff

11 HERA-B NIKHEF contributions: Outer Tracker commissioning and calibrations FLT commissioning Track and vertex reconstruction Triggering on and reconstruction of J/ψ events (2 run: 1.5 M di-lepton triggers) J/ψ µµ J/ψ ee Dimuon Invariant Mass M (GeV) M (GeV)

12 J/ψ production: σ pa = A α σ pn Measure relative J/ψ production cross section on Carbon (A=12) and Ti (A=48) targets (M.Bruinsma) J/ψ (µµ) on C wire Chi2 / ndf = / 114 N ψ = m ψ = σ = p3 = 2.489e p4 = m (GeV/c 2 ) 4 2 J/ψ (µµ) on Ti wire Chi2 / ndf = / 115 N ψ = m ψ = σ = p3 = 3.176e p4 = m (GeV/c 2 ) α J/ψ = 1 ln(a Ti /A C ) ln N J/ψ Ti N J/ψ C ɛ J/ψ C ɛ J/ψ Ti L C L Ti = 1.2 ±.4 ±.17

13 Selecting B candidates: (B J/ψ X) prism prism 4.19/ host=hb-af2 date= 6/11/ BX= 173 arte vs=. time= EvtRunExp = picture= 1 event= 11 prism prism 4.19/ host=hb-af2 date= 6/11/ BX= 173 arte vs=. time= EvtRunExp = picture= 14 event= 11

14 σ(b b) (M.Mevius) entries/.1 GeV/c Upstream spectrum a) Downstream spectrum b) entries/.1 GeV/c c) d) entries/.1 GeV/c e) f) ee invariant mass (GeV/c 2 ) ee invariant mass (GeV/c 2 ) (Prelim.) σ(b b) = ± 8 nb/nucleon

15 Tracking in LHCb: optimizations

16 LHCb light Effort for overall re-optimization of LHCb detector. R.Hierck J.v.Tilburg Two major changes to tracking system under investigation: 1) Reduction of material (.6X.4X in front RICH-2) : Better beampipe and RF-foil, light RICH mirror Reduce number of tracking stations. (baseline: 9 4) tracking performance studies are promising. K S reconstruction under investigation. 2) use 1 st station in Level-1 trigger momentum information available in the topology trigger may require a full silicon station (6.8 m 2 ) careful study still needed

17 Track Reconstruction Change of track reconstruction philosofy continuous tracking (R.Hierck) discrete tracking (J.v.Tilburg) Following efficiency(%) Efficiency (%) momentum(gev/c) Momentum (GeV) performance for long tracks is promising performance for K S under study

18 Summary and Conclusion LHC delay of 1 year translates to installation delay of 6 months. Vertex Locator: TDR approved Mechanics well on schedule RF shield is of crucial importance Readout chip: choice Beetle vs ASCT decision in fall Outer Tracker: TDR approved grounding scheme being finalized preparation for mass production ongoing HERA-B Similar experimental environment as LHCb First physics results LHCb re-optimization: Performance TDR end 22 material reduction in tracking is promising trigger upgrade under study