Olivier Schneider 6th International Conference on B-physics at Hadron Machines BEAUTY ’99 Bled, Slovenia, June 21-25, 1999 Overview of the LHCb experiment

LHCb collaboration Finland:Espoo-Vantaa Inst. Tech. France: Clermont-Ferrand, CPPM Marseille, LAL Orsay Germany: Humboldt Univ. Berlin, Univ. Freiburg, Tech. Univ. Dresden, Phys. Inst. Univ. Heidelberg, IHEP Univ. Heidelberg, MPI Heidelberg, Italy: Bologna, Cagliari, Ferrara, Genoa, Milan, Univ. Rome I (La Sapienza), Univ. Rome II (Tor Vergata) Netherlands:Univ. Amsterdam, Free Univ. Amsterdam, Univ. Utrecht, FOM Poland:Cracow Inst. Nucl. Phys., Warsaw Univ. Spain: Univ. Barcelona, Univ. Santiago de Compostela Switzerland:Univ. Lausanne, CERN UK: Univ. Cambridge, Univ. Edinburgh, Univ. Glasgow, IC London, Univ. Liverpool, Univ. Oxford Brazil: UFRJ (Rio de Janeiro) China: IHEP(Beijing), Univ. Sci. and Tech.(Hefei), Nanjing Univ., Shandong Uni. Russia: INR, ITEP, Lebedev Inst., IHEP, PNPI (Gatchina) Romania: Inst. of Atomic Phys. Bucharest Ukraine: Inst. Phys. Tech. (Kharkov), Inst. Nucl. Research (Kiev) U.S.A.: Univ. Virginia, Northwestern Univ., Rice Univ. O(500) participants from 49 institutes ( )

Why one more B-physics experiment ? and then how...

O. Schneider, Beauty 99 4 Introduction Before 2005, various experiments will explore unitarity triangle:   well measured with B d  J/  K S,  (sin 2  ) < 0.05 no good/direct measurement low statistics measurement with B d , theoretical uncertainty B d and B s mixing measured b  u measured, hadronic uncertainty Constraints on triangle will indicate: – consistency with SM within errors, – or inconsistency with SM (which will not be fully understood) In any case: Next generation experiments at LHC needed for full investigation of CP violation: – precision (high stat.) measurements on many B d and B s decay channels – aim for theoretically clean channels (not necessarily easiest experimentally) – overconstrain CKM matrix, including terms beyond O( 3 )

O. Schneider, Beauty 99 5 CKM matrix (in SM) CP violation is due to  ≠      i         i    V (3)  V CKM  V (3) +  V V ud  V us  V ub  V cd  V cs   V cb  V td  V ts   V tb   i        i    i  V V  Skip (or flash) if already shown by previous speakers

O. Schneider, Beauty 99 6 Unitarity triangles O(10 -2 ) in SM Skip (or flash) if already shown by previous speakers focus on last part anyway Skip (or flash) if already shown by previous speakers focus on last part anyway

O. Schneider, Beauty 99 7 Effect of new physics in B d mixing Within Standard Model extracted from  m d measurement extracted from J/  K S CP asymmetry In presence of new physics in B d mixing extracted from  m d measurement extracted from J/  K S CP asymmetry Note that most extensions to SM (left- right asymmetry, Technicolor, SUSY, … predict new FCNC that can manifest itself in the mixing

O. Schneider, Beauty 99 8 Effect of new physics in B d mixing (cont.) triangle looks consistent with SM because  sides and  J/  K agree within experimental uncertainties Possible scenario in 2005 need precise measurements of  to realize that  sides ≠  and hence discover new physics 1  0   sides  J/  K  sides  

O. Schneider, Beauty 99 9 B d  D* - n  +, D* + n  - CP asymmetries in these decays allow to extract   new     J/  K   and hence  using already measured  J/  K Similar story with B s decays    s new  from CP in B s   J     s new   from CP in B s  D s  K , D s  K  clean extraction of  (~ insensitive to new physics in B s mixing) These CP asymmetries are tiny: O(1%) Here CP asymmetries are larger, because amplitudes of the two tree diagrams for the decay are similar Smooth verbal transition to next transparency … e.g. “these measurements are difficult and will only be possible at the LHC …” Smooth verbal transition to next transparency … e.g. “these measurements are difficult and will only be possible at the LHC …”

O. Schneider, Beauty Dedicated B physics experiment at LHC Requirements for LHCb : reasonable acceptance for both b-hadrons in event (needed for tagging) good proper time resolution (ability to resolve fast B s oscillations) include hadronic final states of interest in trigger (e.g. B d     ) ability to reduce background –good mass resolution –good particle identification LHC’s advantage : large b production cross section large luminosity possibility to study many B s,d,u decays with branching ratios as low as nominal luminosity for ATLAS and CMS: 10**34

O. Schneider, Beauty LHCb acceptance  forward geometry with single-arm spectrometer OK beauty production predominantly at low polar angle two b-hadrons close in 15 mrad < < 300 mrad 4.9 >  > 1.9 Theta coverage determined by a) beam pipe and radiation b) cost Theta coverage determined by a) beam pipe and radiation b) cost

O. Schneider, Beauty Detector layout open geometry  easy access to all components View in bending plane (horizontal) as proposed in 1998: Stress that this is as proposed in the TP, but that the design has evolved a bit since then … differences will be mentioned where important... Stress that this is as proposed in the TP, but that the design has evolved a bit since then … differences will be mentioned where important...

O. Schneider, Beauty Layout in LHC cavern overall size of LHCb determined by existing experimental hall beam crossing point displaced by ~ 11 m (LHCb operates in collider mode) Side view at interaction point 8:

O. Schneider, Beauty o Si detectors o single-sided  150  m thick  r- and  -strips o active radius 1–6 cm o analogue readout o Si detectors o single-sided  150  m thick  r- and  -strips o active radius 1–6 cm o analogue readout Vertex detector 17 silicon stations (disks) installed in vacuum pipe retractable by 3 cm during injection (details from C. Parkes tomorrow) towards spectrometer 40  m resolution on interaction point (along beam axis)

O. Schneider, Beauty RICH detectors (details from A. Go on Thursday) Pattern recognition on photo-detector planes CF 4 rings small C 4 F 10 rings large aerogel rings

O. Schneider, Beauty K/  separation K–  separation > 3  over full momentum range 1<p< 150 GeV/c K–  separation > 3  over full momentum range 1<p< 150 GeV/c highest momentum pion from B s  D s  highest momentum pion from B d  kaon from b  c  s (tagging kaon)

O. Schneider, Beauty Particle identification … without using RICH information … without using RICH information … with RICH fast parametrization … with RICH fast parametrization.. with RICH full simulation and pattern recognition.. with RICH full simulation and pattern recognition 84% efficiency 96% purity 82% efficiency 89% purity Two-body background: B s  KK (BR=  5 ) B s  K  (BR=  5 ) B d  K  (BR=  5 ) Signal: B d   (BR=  5 )  mass in GeV/c 2 Example: B d       analysis

O. Schneider, Beauty Other systems owarm dipole magnet –4 Tm bending power oinner tracking (40 cm x 60 cm) –Micro Strip Gas Chambers + Gaseous Electron Multipliers (MSGC+GEM), or Micro Cathode Strip Chambers (MCSC) –fall-back solution:Si oouter tracking –drift chambers with straw-tube geometry Main tracker Calorimeters opre-shower –single layer Pb + scintillators oECAL (details from A. Jacholkowska tomorrow) –shashlik type, 25 X 0 oHCAL –Fe + scintillating tiles, 5.6 Muon chambers MRPC = Multi-gap Resistive Plate Chambers CPC = Cathode Pad Chamber MRPC = Multi-gap Resistive Plate Chambers CPC = Cathode Pad Chamber Length of HCAL was 7.3 lambda in TP Magnet design changed since TP, but field integral unchanged: racetrack (new shape) warm option (reversing direction of field will be easier) Magnet design changed since TP, but field integral unchanged: racetrack (new shape) warm option (reversing direction of field will be easier) Outer tracker: Say that the preferred options is straws (TP mentions honeycomb but this is now abandoned) Outer tracker: Say that the preferred options is straws (TP mentions honeycomb but this is now abandoned) –Resistive Plate Chambers (RPC) + Cathode Pad Chambers (CPC) for high rate regions –  22  for calorimeters and muon system

O. Schneider, Beauty Running luminosity Aiming for single pp interactions per bunch crossing –radiation damage –detector occupancy –pattern recognition LHCb chosen running luminosity 2 x cm  2 s  1 LHCb chosen running luminosity 2 x cm  2 s  1 Tune luminosity by defocusing beams Constant luminosity throughout LHCb’s lifetime 5.6  bb pairs per year in single pp interactions 30%

O. Schneider, Beauty Level-0 trigger 40 MHz Input rate 1 MHz Output rate 4.0  s Latency bunch-crossing rate = 40 MHz, i.e. front-end electronics and L0 pipeline clocked at 40 MHz non-empty bunch crossing rate = 30 MHz single pp interaction rate =10 MHz thus the pt triggers only provide a factor 10 reduction bunch-crossing rate = 40 MHz, i.e. front-end electronics and L0 pipeline clocked at 40 MHz non-empty bunch crossing rate = 30 MHz single pp interaction rate =10 MHz thus the pt triggers only provide a factor 10 reduction Pile-up veto –2 dedicated Si disks to reject multiple pp interactions (i.e. primary vertexes) –size of luminous region:  z ~ 5 cm p T or E T single track triggers –muonmuon chambers ~ 20 % –electronECAL ~ 10% –hadronECAL+HCAL ~ 60% –photonECAL –... Other triggers are high E T photon, di-muon, random triggers, etc... Pile-up veto: the 2 disks are backward

O. Schneider, Beauty Level-1 trigger 1 MHz Input rate 40 kHz Output rate 512–2048  s Latency variable latency: a maximum of 256  s is quoted in the TP, but it is in fact cheap to add more depth to the pipeline, and he maximum latency will be between 512 and (details from C. Parkes tomorrow) Topological identification of secondary vertexes –find tracks in silicon (only) –reconstruct primary vertex –form secondary vertexes with large impact parameter tracks TP mentioned also the track trigger, but it will probably be abandoned: so don’t mention it here

O. Schneider, Beauty Higher level triggers software only, full event buffer farms of commercial processors Level-2 : reconstruct large impact parameter tracks in Si and first tracking chambers, and use measured momenta to refine secondary vertex requirement Level-3 : reconstruct specific b-hadron decay modes (loose cuts) using all information, incl. RICH 10 ms Latency 40 kHz Input rate 5 kHz Output rate 5 kHz Input rate of which 25% b-events 200 Hz Output rate written to tape (20 MBytes/s) 200 ms Latency LEVEL 2: remove fake vertexes due to low momentum tracks undergoing multiple scattering LEVEL 2: remove fake vertexes due to low momentum tracks undergoing multiple scattering LEVEL 3: here we have to reject b-events, keeping the channels of interest LEVEL 3: here we have to reject b-events, keeping the channels of interest refine secondary vertex requirement adding momentum information to L1 vertex tracks

O. Schneider, Beauty Trigger stability trigger is flexible, robust, and well balanced between levels operating point can be adjusted to running conditions without significant loss in physics point maximizing overall CP sensitivity Example : Adjustment of L0 thresholds with fixed total (  +e+h) retention of 9% Example : Adjustment of L0 thresholds with fixed total (  +e+h) retention of 9% Sensitivity prop. to sqrt(N) or sqrt(efficiency)*(1-2*mistag) Sensitivity prop. to sqrt(N) or sqrt(efficiency)*(1-2*mistag) CP reach with B d     relative to its maximum

O. Schneider, Beauty Trigger efficiencies in %, for useful events, reconstructed and correctly tagged offline L0 L1 L2 Total  e h all B d  J/  (ee)K S + tag B d  J/  (  )K S + tag B s  D s K + tag B d  DK   31  B d     + tag trigger efficiencies are ~ 30% hadron trigger important for hadronic final states “High p T ” track firing L0 trigger can be: –track from B decay of interest –track from other b-hadron useful for tagging Tags considered (so far): –muon or electron from other b-hadron b  lepton –charged kaon from other b-hadron b  c  s Overall tag efficiency = 40% Overall mistag rate = 30% Tags considered (so far): –muon or electron from other b-hadron b  lepton –charged kaon from other b-hadron b  c  s Overall tag efficiency = 40% Overall mistag rate = 30% importance of hadron trigger efficiency dominated by kaon tag importance of hadron trigger

O. Schneider, Beauty DAQ architecture Level-0 buffer: on-detector electronics all data digitized after Level-0 yes Level-1 buffer : off-detector electronics zero-suppressed data transferred to DAQ after Level-1 yes event size: 100 kB

O. Schneider, Beauty Schedule Inner Tracker Vertex Detector RICH, Calorimeters Muon System L0 & L1 Trigger, DAQ Magnet Computing Outer Tracker Technical Proposal LHCb approved LHC and LHCb ready for many years of B physics at “nominal LHCb luminosity” Technical Design Reports Magnet installation Detector and DAQ installation

O. Schneider, Beauty B d  D* -  +, D* +  - need large stat. (CP asymmetry very small) efficient hadron trigger essential Extraction of   from 4 time-dependent decay rates, use  from J/  K S to get  – reconstruct D* inclusively (using slow pion) ~ 270 k events / year with S/B ~ 7 – add D*a 1 channels ~ 320 k events / year   in degrees   in degrees 1 year 5 years  ~ 4 o no strong phase difference assumed no uncertainty on ratio of BRs assumed Get new plot from Jonas...

O. Schneider, Beauty B d  D 0 K* 0 visible BR’s  10 –8 –10 –7 hadron trigger and K/  separation essential K    tags flavour of decaying B d Extraction of  from the measurements of 6 time-integrated rates Only possible at LHCb  m  13 MeV/c 2 ~ 400 signal events total S/B ~ 1  ~ 10 o in one year Guy: this should not be publicized too much Event yield and sensitivity quoted might be incorrect Guy: this should not be publicized too much Event yield and sensitivity quoted might be incorrect Say that LHCb is the ideal place where to study the possibility of a measurement gamma using this method

O. Schneider, Beauty B s oscillations good proper time resolution  t essential  t ~ 43 fs Need to resolve  m s oscillations to measure time-dependent CP asymmetry in B s decays B s  D s    : ~ rec. and tagged events/year > 5  measurement of  m s up to 48 ps  1 (x s = 75) Can also measure  s with untagged sample Do not spend too much time on this transparency

O. Schneider, Beauty counter part of B d  J/  K S CP asymmetry allows to extract the phase of B s mixing, i.e. angle  B s  J/  This channel: good place to look for new physics This channel: good place to look for new physics decay into spin-1 particles: J/   can be CP-odd or CP-even (depending on angular orbital momentum)   additional dilution on CP asymmetry need angular analysis to separate contributions good proper time resolution needed can also be done in ATLAS/CMS with similar sensitivity  ~ 0.01 in one year depends  m s and r=A(CP-odd)/A(CP-even) (will be extracted as well) Assumption: the decays to the 2 CP eigenstates have the same strong phase, i..e. r is real Assumption: the decays to the 2 CP eigenstates have the same strong phase, i..e. r is real

O. Schneider, Beauty B s  D s - K +, D s + K - hadron trigger proper time resolution mass resolution K/  separation (RICH) hadron trigger proper time resolution mass resolution K/  separation (RICH) kill B s  D s  background Essential features: Extraction of    from 4 time-dependent decay rates, use   from J/  to get  Large CP asymmetries expected since the two tree decay diagrams have similar rates ~ 2.5 k events / year with S/B > 10  ~ 6–13 o in one year depends on ,  m s, and strong phase (will be extracted as well)

O. Schneider, Beauty Conclusion oLHC offers unique opportunity to probe CKM sector in depth oTo go beyond what other experiments can do, LHCb will rely on –efficient, robust, and flexible triggering scheme –high performance particle identification –excellent mass and proper time resolutions oLHCb will operate at its full potential from the first day of LHC running and for many years oLHCb can study many different B decay modes and, with high precision and efficiency, including fully hadronic channels oAbility of measuring CKM elements accurately implies good sensitivity to physics beyond the Standard Model Although all LHC experiments will contribute (B d  J/  K S, B d  J/  ), LHCb has the major responsibility in most of the hadronic channels