The LHCb Flavour Physics Experiment

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1 The LHCb Flavour Physics Experiment University of Glasgow AGH, University of Science and Technology, Krakow, Poland, 4 March 2010

Outline Motivation LHC @ CERN @ Geneva The LHCb experiment The 2010

2 Outline Motivation Geneva The LHCb experiment The 2010 LHC(b) run Prospects for AGH, UST, Krakow, Poland, 4 March /65

3 Motivation Universe, matter and antimatter, CP violation

4 Universe, matter and antimatter Equal amounts of matter and Antimatter? Matter dominates! AGH, UST, Krakow, Poland, 4 March /65

annihilating with antimatter in the early Universe,

5 Matter-antimatter asymmetry in the universe Common belief: For every billion ordinary particles annihilating with antimatter in the early Universe, one extra was left standing AGH, UST, Krakow, Poland, 4 March /65

6 How to generate a matter-antimatter asymmetry? No definitive answer to this question yet! In 1967 A. Sacharov formulated a set of general conditions that any mechanism of B-asymmetry generation has to meet : 1) Need a process that violates the baryon number B: (Baryon number of matter=1, of antimatter = -1) 2) Both C and CP symmetries should be violated 3) Conditions 1) and 2) should occur during a phase in which there is no thermal equilibrium Violation of the CP symmetry has been a major field of research in High Energy Physics since already the 1950s Flavour Physics is the grand picture (CP violation has far more interest than solely cosmological considerations) AGH, UST, Krakow, Poland, 4 March /65

7 On the 3 big search paths in High Energy Physics CP Violation AGH, UST, Krakow, Poland, 4 March /65

8 Flavour Physics programme (not comprehensive!) CP violation Dynamics of heavy flavour decays CKM matrix Quark mixing Discovery channels Hadronic Rare decays Semi-leptonic n-body baryonic Flavour Physics Time-(in)dependent measurements CP asymmetries Theory Experiment Radiative decays Lifetimes Branching ratios AGH, UST, Krakow, Poland, 4 March /65

9 Geneva A multi-purpose lab & accelerator complex

10 Geneva, CERN and the LHC CERN: European laboratory for high energy physics LHC

11 CERN aerial view (old-ish picture)

12 CERN accelerator complex

13 Section of the LHC

The Large Hadron Collider LHC LHC: proton-proton collider, circumference of 27 km PS, SPS: old accelerators now used as pre-accelerators for the LHC Nominal energy of 14 TeV, 1.

14 The Large Hadron Collider LHC LHC: proton-proton collider, circumference of 27 km PS, SPS: old accelerators now used as pre-accelerators for the LHC Nominal energy of 14 TeV, 1.1x10 11 protons per bunch - At 7 TeV a proton has % speed of light LHC beams formed from counter-rotating bunches of protons (clever two-in-one design : 2 beam-pipes inside same magnet with opposite B field in each pipe) Momentum cleaning RF Pt3 Pt4 CMS Totem Pt5 Pt6 Pt7 Dump Betatron cleaning ALICE Pt2 Pt1 Pt8 LHCb ATLAS LHCf

15 LHC stored energy In 2010 the LHC reached ~ 20 MJ, close to 5kg TNT! Nominal LHC A factor 2 in magnetic field A factor 7 in beam energy A factor 200 in stored energy! 360 MJ 2808x p 4x72x p LHC target Done to date

16 LHC increase in stored energy over 2010 linear Y scale log Y scale apr may jun jul aug apr may jun jul aug 3 MJ AGH, UST, Krakow, Poland, 4 March /65

17 The LHCb Experiment The flavour physics experiment at the LHC

18 LHCb an international collaboration 15 countries Over 50 universities and laboratories Over 700 scientists Cavern 100 metres below ground

19 LHCb physics roadmap Mission statement - Search for new physics probing the flavour structure of the SM - Study CP violation and rare decays with beauty & charm hadrons Measure processes strongly suppressed in the Standard Model but - Sensitive to new physics (e.g. contributions from new heavy particles in loop processes) - Poorly constrained by present data Measure the sides and angles of the unitarity triangle which is at the heart of the CKM description of CP violation in the Standard Model - Over-constrain the system with various related measurements - Look for inconsistencies among various independent measurements of the same quantity using decay modes sensitive or non-sensitive to new physics (modes dominated by tree-level or loop diagrams, respectively) Measure CP violating quantities that probe the flavour structure of the SM AGH, UST, Krakow, Poland, 4 March /65

20 At the heart of «indirect searches» for new physics Tree diagram 0 B b d,s W d π u c D, D s d, s Virtual particles appear in loop mediated processes Loop diagrams New Physics Penguin diagram 0 B Box diagram b d,s 0 B b W? u, c, u, c, t W t? W s s s d,s d, s K 0 s 0 B, d,s u,c, t b AGH, UST, Krakow, Poland, 4 March /65

21 Can one do flavour physics at the LHC? Large production of heavy flavour hadrons in proton-proton collisions : - At the E=14 TeV s pp bb ~ 500 mb (compared with s ee bb ~ 1 E=10 GeV) - In nominal conditions (LHC luminosity & data taking time of 10 7 s) this translates to ~ b-quark pairs produced per year! - All species of b-/c-flavoured hadrons produced: B 0, B ±, B c±, B s, L b, etc. BUT : - b and anti-b highly correlated, either produced very forward or very backward with respect to the p-p beam-line b need for a forward detector b - s bb /s total < 1 % and decay branching ratios (interesting modes) only ~ b need for extremely efficient selection (trigger) b with high background rejection power AGH, UST, Krakow, Poland, 4 March /65

22 Can one do flavour physics at the LHC? Characteristics of heavy flavour hadrons : - High mass high transverse momentum decay daughters - Large lifetimes typically ~ seconds measurable decay length ~ 1 cm thanks to the relativistic boost B-decay displaced vertex K B B s B-production at pp-collision primary vertex D s b tag K K + AGH, UST, Krakow, Poland, 4 March /65

23 Key ingredients to high physics performance 1. Trigger efficiency : - Fast, efficient, flexible selection of interesting physics events while rejecting as early as possible the undesired background 2. Vertex reconstruction and excellent impact parameter resolution : - Precise reconstruction and separation of primary and secondary vertices - Identification of long-lived heavy flavour decays 3. Tracking performance : - Efficient determination of charged track trajectories - Precision determination of their momentum and angles 4. Particle identification : - Differentiation of hadrons, muons, electrons, photons over large momentum spectrum 5. Invariant mass resolution : - High mass resolution easier separation of decay modes with same topology 6. Detector alignment : - Minimise biases introduced by non-precise knowledge of positions of sub-detectors

several particle measurement purposes : - Particle identity - Trajectory - Energy or

24 The LHCb detector Reconstruction: - muons: easy - hadronic tracks: fine - electrons: OK - 0 s, K S, L: OK; 0 s difficult - neutrinos, neutrons, K L : no Each sub-detector has one of several particle measurement purposes : - Particle identity - Trajectory - Energy or momentum Forward spectrometer Acceptance ~ mrad 21 m long 10 m high, 13 m wide 5600 tonnes in total

25 The LHCb cavern and detector (May 2009) AGH, UST, Krakow, Poland, 4 March /65

1. Two-level trigger system pp crossing rate - Distinguish interesting physics - Reject asap the background Fast, efficient, flexible ~ 30 MHz Level 0 Custom hardware trigger High E T particles -

26 1. Two-level trigger system pp crossing rate - Distinguish interesting physics - Reject asap the background Fast, efficient, flexible ~ 30 MHz Level 0 Custom hardware trigger High E T particles - Fast decision in ~ 4 ms - Partial detector information 1 MHz High Level Trigger ~ 2 khz 70 MB/s = 250 GB/h Software trigger Storage Search for physics signatures - Software trigger run in PC farm (several thousand CPU nodes) - Full detector information - Increasing level of complexity in event reconstruction and selection - Decision in ~ 1/20 s - Typical throughput ~ 70 MB/s 250 GB per hour AGH, UST, Krakow, Poland, 4 March /65

Vertex LOcator : - Precise determination and separation of

27 2. A precision vertex detector the VELO 2 halves of 21 stations 2 silicon strip sensors per station Only 8 mm from beams VELO Vertex LOcator : - Precise determination and separation of primary and secondary vertices - Identification of long-lived hadron decays

28 Close-up of the VELO sensors

29 The VELO schematics AGH, UST, Krakow, Poland, 4 March /65

s(x,y,z) ~ (14,13,80) mm for PVs with 25 tracks Primary vertex resolution in Z Precise primary and secondary vertex

30 VELO performance Vertex detector 2 retractable halves Long-lived heavy flavour particles vertex displaced by typically ~ 1cm with respect to the primary vertex Beam Best primary vertex resolutions at the LHC! s(x,y,z) ~ (14,13,80) mm for PVs with 25 tracks Primary vertex resolution in Z Precise primary and secondary vertex resolutions + precise momentum resolution excellent propertime resolution ~ 50 fs! Power Z - Const / N Epsilon z res (1.14/N ) mm AGH, UST, Krakow, Poland, 4 March /65

31 Impact parameter resolution IP = Impact Parameter Daughters of long-lived particles tend to have a large IP - Primary vertex Direction of B + IP resolutions as low as mm Better resolutions expected with better alignment AGH, UST, Krakow, Poland, 4 March /65

32 VELO beam-beam collisions and beam-gas events Green : vertices in beam1-beam2 events Blue : beam1 empty collisions Red : empty - beam2 collisions (z-axis is scaled compared to transverse dimensions to see clearly the beam angle) AGH, UST, Krakow, Poland, 4 March /65

33 VELO close-up of event display with real tracks AGH, UST, Krakow, Poland, 4 March /65

34 A multi primary vertex event AGH, UST, Krakow, Poland, 4 March /65

35 Event display primary and secondary vertices AGH, UST, Krakow, Poland, 4 March /65

3. Efficient and precise tracking system Precise determination of track parameters Vertex detector : - Silicon micro-strip detector - Provides track seeds - Momentum and angles (+ full covariance

36 3. Efficient and precise tracking system Precise determination of track parameters Vertex detector : - Silicon micro-strip detector - Provides track seeds - Momentum and angles (+ full covariance matrix) Silicon trackers : - Silicon micro-strip detectors - Used closer to the beam-pipe where track density is higher - TT / IT before/after the magnet Outer tracker : - Thousands of gas-filled straw tubes Magnet AGH, UST, Krakow, Poland, 4 March /65

37 The magnet (during installation, end 2004) Warm dipole magnet 2 huge 27 tonnes coils 1450 tonnes iron yoke Curving charged tracks allowing for the measurement of their momentum

38 Magnet and beampipe

39 Tracking system performance Efficient track pattern recognition - Ex.: VELO cluster finding efficiency of 99.7% High momentum resolution needed to separate topologically similar decay modes Excellent momentum resolution dp/p = 0.35% to 0.55% achieved Silicon strip and straw-tube detectors for tracking - long lever arm ~ 10 m - hit resolutions ~ 55 and 250 mm, respectively Outer tracker (straw tubes) LHCb Preliminary Together with precise determination of track slopes provides very good mass resolutions AGH, UST, Krakow, Poland, 4 March /65

4. Particle identification systems Separation of e/g/m/ /K/p over large momentum range - Heavy flavour hadron mass peaks with similar topology often overlap 2 RICH detectors : - Ring Imaging

40 4. Particle identification systems Separation of e/g/m/ /K/p over large momentum range - Heavy flavour hadron mass peaks with similar topology often overlap 2 RICH detectors : - Ring Imaging Cherenkov detectors with photo-diodes - Differentiate pions, kaons and protons over large momentum spectrum [ 2, 100 ] GeV Calorimeter system : - A preshower, a scintillator pad detector, an electromagnetic and a hadronic calorimeter - Measure particle energies for electrons, photons, hadrons - Identify electrons and photons and differentiate them from hadrons Muon chambers : - 5 stations in total - Identify and measure muons

The 2 Ring Imaging CHerenkov detectors RICH1 : - Before the magnet - For low momentum tracks RICH2 : - After the magnet - For high momentum tracks Silica

41 The 2 Ring Imaging CHerenkov detectors RICH1 : - Before the magnet - For low momentum tracks RICH2 : - After the magnet - For high momentum tracks Silica Aerogel n= GeV/c RICH1 C 4 F 10 gas n= Up to ~70 GeV/c CF 4 gas n= Beyond ~100 GeV/c RICH2 AGH, UST, Krakow, Poland, 4 March /65

42 PID with the RICH detectors 2 opposite charged tracks K + K - decay with kaon identification? PID AGH, UST, Krakow, Poland, 4 March /65

43 PID with the RICH detectors 2 particles with same final state but different mass D + KK D s KK AGH, UST, Krakow, Poland, 4 March /65

44 «RICH PID» example of B - D 0 ( hh) - / K - decays B - D 0 ( K ) - B - D 0 ( K ) K - B - D 0 ( ) - B - D 0 ( KK) - Luminosity: ~ 34 pb -1

45 Installation of calorimeters and muon chambers AGH, UST, Krakow, Poland, 4 March /65

46 The electromagnetic calorimeter (during installation, 2005) 6 x 7 m 2 wall 3300 blocks of scintillator, fibre optics and lead - Measure energy of electrons, photons - Distinguish e/g from hadrons

47 PID with the calorimeters 0 gg s = 7.2 MeV ECAL is calibrated to 2% level 0 resolution is better than expected L ~ 150 nb -1 J/y e + e - D 0 K 0 s = 23.5 ± 2.5 MeV AGH, UST, Krakow, Poland, 4 March /65

48 PID with the calorimeters Rare radiative decay B 0 K * g AGH, UST, Krakow, Poland, 4 March /65

49 PID with the muon chambers m + m - modes AGH, UST, Krakow, Poland, 4 March /65

50 5. Invariant mass resolution Separation of decay modes with same topology 2 particles with same final state but different mass : imagine a very poor mass resolution and no RICH PID Invariant mass of a 2-body decay M 2 = m m (E 1 E 2 p 1 p 2 cosq ) need precise knowledge of momentum p and angle q of decay products (as well as their particle type) D + KK D s KK Evolution of mass resolution over time: for J/ψ μμ ; ideal resolution σ MC =12 MeV May: σ~18 MeV August: σ~16 MeV November: σ~13 MeV

Module and sensor alignment known to better than 5 mm VELO is opened during

51 6. Detector alignment Better alignment minimises biases and improves resolutions Best VELO hit resolution is 4 mm Great achievement! Module and sensor alignment known to better than 5 mm VELO is opened during injection! Fill-to-fill variation of two halves relative alignment < 5mm AGH, UST, Krakow, Poland, 4 March /65

52 The 2010 LHC(b) run A very successful start!

Redaelli, LHC performance in 2010 and prospects LHC end-of-year

53 LHC efficiency in the 2010 (proton) run Great achievement (specially for a 1 st year of run) 65 % availability! Plot taken from talk S. Redaelli, LHC performance in 2010 and prospects LHC end-of-year jamboree, 17/12/2010

54 LHC luminosity in the 2010 (proton) run 2010 goals achieved! Luminosity delivered: almost 50 pb-1 Peak instantaneous lumi.: ~ cm -2 s -1 AGH, UST, Krakow, Poland, 4 March /65

55 Operation LHCb control room Shift Leader Data Manager 2 main shifters + many experts on call

56 Operation LHCb control room

recorded by LHCb Over 3 pb -1 20 days later!

57 LHCb 2010 data taking luminosity recorder ~ 38 pb -1 recorded Luminosity delivered by the LHC Luminosity recorded by LHCb Over 3 pb days later! 1 pb -1 on 7 th August AGH, UST, Krakow, Poland, 4 March /65

58 2010 data taking efficiency Excellent efficiency ~ 90% 94% Running with high average # of visible interactions per crossing Stable data taking High efficiency of all sub-detectors, increasing with time (experience)

59 LHCb sub-detector efficiencies Detector efficiencies > 99%! AGH, UST, Krakow, Poland, 4 March /65

First B + J/Y K + candidate event Mass = (5326.7±10.9) MeV/c 2 Momentum: p = 62.7 GeV/c, p T = 10.

60 First B + J/Y K + candidate event Mass = (5326.7±10.9) MeV/c 2 Momentum: p = 62.7 GeV/c, p T = GeV/c Muons are magenta, kaon is red Full spectrometer, top view VELO region, top view Transverse plane (looking from CALO to VELO) First B candidate seen in LHCb! B + J/ψ K + J/ψ μ + μ

61 «Seeing» CP violation with B 0 /B s K modes RAW asymmetry is visually obvious! K + - K - + B 0 B s Note: No corrections for production/detector asymmetries AGH, UST, Krakow, Poland, 4 March /65

62 Prospects for The future is bright

63 LHC operation in 2011 prospects Re-start of physics runs in mid-march Energy : 7 TeV collisions Integrated luminosity : Reach 1 fb -1 by end 2011 (we got ~0.04 fb -1 in 2010!) Plot taken from talk S. Redaelli, LHC performance in 2010 and prospects LHC end-of-year jamboree, 17/12/2010 AGH, UST, Krakow, Poland, 4 March /65

LHCb 2010 & 2011 running conditions 2010 running conditions : Collisions at 7 TeV ~ 38 pb -1 collected Expectations for 2011 : Reach 1 fb -1 = 1000 pb -1 by end 2011 Discussion ongoing for 8 TeV run

64 LHCb 2010 & 2011 running conditions 2010 running conditions : Collisions at 7 TeV ~ 38 pb -1 collected Expectations for 2011 : Reach 1 fb -1 = 1000 pb -1 by end 2011 Discussion ongoing for 8 TeV run Average number of visible pp interactions per crossing LHCb design specifications (80% of design luminosity reached with 344 colliding bunches instead of 2622) AGH, UST, Krakow, Poland, 4 March /65

In short LHCb has already proven to be a heavy flavour experiment at a hadron machine Excellent and promising results are coming out - This was just the beginning

65 In short LHCb has already proven to be a heavy flavour experiment at a hadron machine Excellent and promising results are coming out - This was just the beginning Many world-class measurements just around the year - And many competitive with the TeVatron results Stay tuned Thumbs up! AGH, UST, Krakow, Poland, 4 March /65

b Physics Prospects For The LHCb Experiment Thomas Ruf for the LHCb Collaboration Introduction Detector Status Physics Program

b Physics Prospects For The LHCb Experiment Thomas Ruf for the LHCb Collaboration Introduction Detector Status Physics Program b Primary goal of the LHCb Experiment Search for New Physics contributions