Hadronic B Decays at LHCb

Transcription

1 Hadronic B Decays at LHCb University of Glasgow Seminar at LPHE, EPFL, Lausanne, 20 December 2010 OUTLINE: Physics motivation 2010 LHC(b) run and prospects for 2011 B D X, H b h h and B h h h

2 Physics motivation

3 Is the study of hadronic B decays worth it? = Discussed in talk CP violation Dynamics of heavy flavour decays Quark mixing Discovery channels CKM g angle H b h h B D X B h h h 2-body baryonic Hadronic B decays Time-(in)dependent measurements CP asymmetries Theory Experiment 3-body baryonic Lifetimes Branching ratios LPHE, EPFL, Lausanne, 20 Dec (Non-comprehensive listing) 3/64

4 Status of g in CKM global fits Tree-level decays Loop decays Standard Model benchmark measurement of g Measurement of g sensitive to New Physics Fit with all constraints: g = (67.2 ± 3.9)º Taken from CKMfitter LPHE, EPFL, Lausanne, 20 Dec /64

5 Status of g in CKM global fits Tree-level decays Loop decays Standard Model benchmark measurement of g Measurement of g sensitive to New Physics Fit with trees only : g = (71 ± 23)º Direct and precise measurements are welcome! Taken from CKMfitter LPHE, EPFL, Lausanne, 20 Dec /64

6 Direct measurements of g Tree-level decays B D X decays : Time-integrated measurements Time-dependent measurements Standard Model benchmark measurement of g LHCb can do them all! Loop decays Measurement of g sensitive to New Physics B h h (h) modes : Time-dependent measurements exploiting U-spin symmetry (B hh) Time-integrated Dalitz plot analysis (B hhh) LPHE, EPFL, Lausanne, 20 Dec /64

7 The LHCb experiment

8 The LHCb collaboration 730 members 15 countries 54 institutes LHCC open session 17 February 2010 Member countries of the LHCb Collaboration LPHE, EPFL, Lausanne, 20 Dec /64

9 The LHCb the LHC Forward spectrometer Acceptance: ~ mrad Nominal lumi.: cm -2 s -1 Nominal # B s / 2fb -1 : (nominal year) Reconstruction: - muons: easy - hadronic tracks: fine - electrons: OK - p 0 s, K S, L: OK; p 0 s difficult - neutrinos, neutrons, K L : no p Mission statement - Search for new physics probing the flavour structure of the SM - Study CP violation and rare decays with beauty & charm hadrons B flight path of the order 5-10mm p b b b b σ(inclusive) ~ 80 mb σ(b bbar) ~ 0.5 mb LPHE, EPFL, Lausanne, 20 Dec All b-hadron species produced 9/64

10 System requirements (Hadronic) trigger Fast, flexible and efficient Vertexing Precise reconstruction and separation of primary and secondary vertices - Identification of long-lived heavy flavour decays Tracking Precise determination of track parameters Excellent momentum resolution dp/p = 0.35% to 0.55% Excellent impact parameter (IP) resolutions Particle identification Mass peaks often overlap -> need for excellent p/k/p separation over large momentum range to separate the topologically similar decay modes Crucial to LHCb physics programme Beauty & charm mesons Excellent - Mass resolutions ~10-40 MeV - Propertime resolution ~60 fs LPHE, EPFL, Lausanne, 20 Dec /64

11 The LHC(b) run in 2010 and prospects for 2011

12 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 LPHE, EPFL, Lausanne, 20 Dec /64

13 LHC luminosity in the 2010 (proton) run 2010 goals achieved! Luminosity delivered: almost 50 pb-1 Peak instantaneous lumi.: ~ cm -2 s -1 LPHE, EPFL, Lausanne, 20 Dec /64

14 LHCb 2010 data taking luminosity recorded ~ 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 LPHE, EPFL, Lausanne, 20 Dec /64

15 LHCb 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) LPHE, EPFL, Lausanne, 20 Dec /64

16 LHC operation in 2011 prospects Re-start of physics runs in mid-march Energy : - 7 or 8 TeV collisions (to be decided at the Chamonix workshop in Jan. 2011) Integrated luminosity : - reach 1 fb -1 by end 2011 (int. lumi. between 1-3 fb -1 would appear feasible!) Plot taken from talk S. Redaelli, LHC performance in 2010 and prospects LHC end-of-year jamboree, 17/12/2010 LPHE, EPFL, Lausanne, 20 Dec /64

17 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) LPHE, EPFL, Lausanne, 20 Dec /64

18 LHCb performance in 2010

19 LHCb subdetector efficiencies Detector efficiencies > 99%! LPHE, EPFL, Lausanne, 20 Dec /64

20 Trigger scheme Crossing rate ~ MHz Level 0 Custom hardware trigger 1 MHz High Level Trigger Software trigger ~ 2 khz High E T particles - Partial detector information - Fast decision Search for physics signatures - Software trigger run in event farm - Full detector information - Increasing level of complexity in event reconstruction and selection Storage LPHE, EPFL, Lausanne, 20 Dec /64

21 Tracking High momentum resolution needed to separate topologically similar decay modes Silicon strip and straw-tube detectors for tracking - long lever arm ~ 10 m - hit resolutions ~ 55 and 250 mm, respectively Together with precise determination of track slopes provides very good mass resolutions - Worse by 10-20% compared to MC. But still excellent. Outer tracker (straw tubes) LHCb Preliminary Provides with high vertex resolutions an excellent propertime resolution LPHE, EPFL, Lausanne, 20 Dec /64

22 Mass resolutions K s pp J/y mm m = MeV s = 3.3 MeV m = MeV s = 14 MeV B + J/yK + m = 5277 MeV s = 13 MeV s = 9 MeV (w/ mass constr) Resolutions still slightly different from prediction (calibration and alignment ongoing) LPHE, EPFL, Lausanne, 20 Dec /64

23 Vertexing Best such resolutions at the LHC! Primary vertex resolution in Z Vertex detector 2 retractable halves Power Z - Const / N Epsilon z res (1.14/N ) mm IP resolutions ~ 20% worse than in MC. But still excellent IP = Impact Parameter p - Primary vertex Direction of B p + LPHE, EPFL, Lausanne, 20 Dec /64

24 Vertexing close-up of the vertex detector LPHE, EPFL, Lausanne, 20 Dec /64

25 Vertexing XY tranverse view of a collision LPHE, EPFL, Lausanne, 20 Dec /64

26 Vertexing 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) LPHE, EPFL, Lausanne, 20 Dec /64

27 A multi primary vertex event LPHE, EPFL, Lausanne, 20 Dec /64

28 Particle identification LHCb has 2 RICH detectors Provide excellent p, K and p separation over the large spectrum p [ 2, 100] GeV/c Can be improved with harder D(log likelihood) cuts D + KKp D s KKp D + Kpp (Only 0.6 pb -1 ) LPHE, EPFL, Lausanne, 20 Dec /64

29 Particle identification delta log likelihood tuning Tuning matters DLL(K-p) > 0 DLL(K-p) > 5 LPHE, EPFL, Lausanne, 20 Dec /64

30 Particle identification performance determined on data D* D sample f sample K s sample L sample LPHE, EPFL, Lausanne, 20 Dec /64

31 Towards g with B D X decays Standard Model benchmark measurement

32 The (large) B D X family Modes : B 0 D p, D K ( * ) B - D p -, D K - B s D s p, D s K, D K ( * ), D f The above with D 2-/3-/4-body Physics : Set of modes with rich scope for CP violation measurements, BR ratios Theoretically clean measurement of g with B DK modes (relative weak phase between the 2 diagrams = -g) Sensitivity to g from interference between the 2 diagrams Only requirement: D 0 and D 0 decay to common final state B V V * cb us b u s K u c D u 0 V ub V cs * B b u u D c s K u 0 - final state contains D - final state contains D-bar - colour allowed - colour suppressed LPHE, EPFL, Lausanne, 20 Dec /64

33 g with B D K decays Theoretically very clean way of measuring g Sensitivity to g from interference between the 2 diagrams Only requirement: D 0 and D 0 decay to common final state B V V * cb us b u s K u c D u 0 V ub V cs * B b u u D c s K u 0 - final state contains D - final state contains D-bar - colour allowed - colour suppressed Relative magnitude of suppressed amplitude: r B Relative weak phase: -g Relative strong phase: d B LPHE, EPFL, Lausanne, 20 Dec /64

34 g with B D K decays - Any D 0 and D 0 decay to a common final state gives interference effects dependent on g - So any hadronic final state is in principle useful! Some D 0 decay modes in use : CP eigenstates Cabibbo favoured (CF) Singly Cabibbo suppressed (SCS) Doubly Cabibbo suppressed (DCS) 3-body decays K + K -, p + p -, K s p 0, K s f K s pp KK *, KKpp Kp K s pp GLW Dalitz GLS /Dalitz ADS GGSZ Example: ADS LPHE, EPFL, Lausanne, 20 Dec /64

35 The B D X family a rich physics case Decay mode / analysis ADS / GLW analyses GGSZ model-dependent/-independent analyses Time-dependent CP violation in B s D s K Dalitz analysis with B D K p B 0 D 0 K*, B s D 0 f Measurement (s) g g A CP s, g g g B 0, B s and relative lifetime measurements Branching ratio measurements BR(B 0 DK) / BR(B 0 Dp) First observations of rare modes: B s D K/p B 0 D p, B s D s p Ratio of yields in B 0 D K and B s D s p Dm d / Dm s f d / f s LPHE, EPFL, Lausanne, 20 Dec (Non-comprehensive listing) 35/64

36 B - D 0 h - (h = p, K) decays 2-body D 0 h h decays Mass peak with ~ 34 pb -1 B - D 0 ( Kp) K - Clean signals seen for - B Dp with D Kp, KK, pp - B DK with D Kp Early-ish measurements : B DK / B Dp branching ratio measurement, with D K p (known only to ~24% precision) A CP from time-integrated analyses (ADS/GLW methods) expect (stat.) error s g ~ 17º with 1 fb -1 ( data sample) For comparison: CDF yield on 1 fb -1 ~ 65 KK+pp events LPHE, EPFL, Lausanne, 20 Dec /64

37 B - D 0 ( hh) p - / K - decays Luminosity: ~ 34 pb -1 B - D 0 ( Kp) p - B - D 0 ( Kp) K - B - D 0 ( pp) p - B - D 0 ( KK) p - LPHE, EPFL, Lausanne, 20 Dec /64

38 B - D ( * ) CP K -( * ) GLW analyses status Phys. Lett. B 265 (1991), 172 Phys. Lett. B 253 (1991), 483 Theoretically clean measurement of g from rates and CP asymmetries of B D ( * ) CP K ( * ) decays Gronau-London-Wyler method: use CP eigenstates of the D Results available from BaBar, Belle and CDF A CP+- = [Γ(B D ( ) CP+ K ( ) ) Γ(B + D ( ) CP+ K ( )+ )] [Γ(B D ( ) CP+ K ( ) ) + Γ(B + D ( ) CP+ K ( )+ )] A CP 0 direct CP violation Details at HFAG website Seminar LPHE, EPFL, Lausanne, Dec. 38/64

39 B D p decays Dalitz analyses Mass peaks with ~ 34 pb -1, i.e. almost all the 2010 data sample B + D 0 (K s pp) p B + D 0 (K s KK) p Dalitz plot analysis of B DK with D K s pp expect (stat.) error s g ~ 18º with 1 fb -1 ( data sample) LPHE, EPFL, Lausanne, 20 Dec /64

40 B (s) D (s) p decays Luminosity: ~ 34 pb -1 B s D s ( fp) p B s D s ( K*K) p Measurements of Dm d and Dm s expected for 2011 LPHE, EPFL, Lausanne, 20 Dec /64

41 B (s) D (s) h decays Time-dependent CP studies: Eventually, SM benchmark measurement of g from B (s) D (s) h (h = p, K) Analysis involves fit to time-dependent asymmetries A B 0 q D u q q cosh C cos Δmτ S sinδmτ ΔΓ t/ 2 A sinhδγ t/ 2 q ΔΓ q Extraction of g needs theoretical input on U-spin breaking effects (rather difficult and with large uncertainties) Or combined fit to Dh and D s h B 0 D + p - Mass peak with 0.75 pb -1 LPHE, EPFL, Lausanne, 20 Dec /64

42 B D X modes with 6-body final states! B +,0 D 0,+ a 1 (πππ) B s D s a 1 (πππ) Partially reconstructed background Level of combinatorics is low in spite of multi-p final state LPHE, EPFL, Lausanne, 20 Dec /64

43 B D X : physics goals with the data sample? Measurement of f d /f s ratio (b d/s fragmentation) Measurement of the D s K/D s p branching fractions ratio 2010 Measurements of relative rates and CP asymmetries - Focus first on 2-body non-suppressed D decays Combination of various g measurements will provide world-best results - Sensitivity ~ 6-8º (statistical error) with 1 fb -1 according to MC studies LPHE, EPFL, Lausanne, 20 Dec /64

44 Towards g with charmless B decays New Physics sensitive measurement

45 The H b h h family Standard modes (BRs ~ ) : B 0 pp, B s KK B 0 Kp, B s pk L b pk, pp Rare modes : B 0 KK, B s pp not yet found experimentally Physics : Set of modes with rich scope for CP violation measurements - Time-independent and dependent A CP Access to g with B 0 pp and B s KK (Phys. Lett. B 459 (1999), 306) Tree-level diagram Penguin diagram LPHE, EPFL, Lausanne, 20 Dec /64

46 The H b h h family a rich physics case B 0 pp : time-dependent asymmetry - so far inconsistency in direct CP contribution (C pp ) between BaBar and Belle B 0 K + p - : direct CP violation measurement B s p + K - : direct CP violation, branching ratio (BR) measurement B s KK: time-dependent asymmetry, BR measurement, lifetime measurement Gronau, Lipkin and Rosner relation A B p K AB p K AB p K AB p K 2 s s B 0 K + p -, B + K + p 0 : in CP asymmetry hard to understand theoretically B 0 pp, B s KK : determination of the CP angle g exploiting U-spin symmetry L b pk, pp : CP asymmetries, lifetime ratio measurements (wrt B 0 ) Rare B h + h - : h = p, K but also a baryon such as p, L Etc. List non exhaustive LPHE, EPFL, Lausanne, 20 Dec /64

47 The H b h h family world results B-factories - BaBar & Belle : Measurements involving B 0 s only Branching ratio measurements Charge asymmetry (direct CP violation) measurements Time-dependent CP asymmetries measurements TeVatron - CDF : Measurements involving B 0 s, and also B s s or L b s First observation of decay modes B s pk and B s KK First observation of decay modes L b pp and L b pk Branching ratio measurements Charge asymmetry measurements LPHE, EPFL, Lausanne, 20 Dec /64

48 The H b h h family some CDF results CDF Collaboration, arxiv:hep-ex/ fb -1 CDF Collaboration, arxiv: v1 [hep-ex] LPHE, EPFL, Lausanne, 20 Dec /64

49 The H b h h family as seen by LHCb What s in the basket with 35 pb -1, i.e. almost all the 2010 data sample? ~ 2100 signal events p p hypothesis (No PID cuts) LPHE, EPFL, Lausanne, 20 Dec /64

50 Loose selection B 0 p p and B s K K Applying particle identification cuts B 0 p p B s K K Time-dependent CP asymmetries in view of g measurement will take time... (R. Fleischer method using U-spin symmetry Phys. Lett. B 459 (1999), 306) LPHE, EPFL, Lausanne, 20 Dec /64

51 Loose selection B K p RAW A CP (B 0 ) = ± (stat.) HFAG average : ± Yield: 838 ± 38 Note: Raw numbers No corrections for production/detector asymmetries (same comment goes for all subsequent A CP results) HFAG website LPHE, EPFL, Lausanne, 20 Dec /64

52 Charge asymmetry in B 0 /B s K p (tight selection) RAW asymmetry is visually obvious! K + p - K - p + B 0 B s Note: No corrections for production/detector asymmetries LPHE, EPFL, Lausanne, 20 Dec /64

53 Tight selection optimised for B s p K RAW A CP (B s ) = 0.43 ± 0.17 (stat.) CDF, 1 fb -1 : 0.39 ± 0.15 (stat.) ± 0.08 (syst.) LHCb competitive with CDF with ~ 25 less luminosity! RAW B s / B d relative yield R pk = ( 10.7 ± 2.0 ) % (stat. error only) LPHE, EPFL, Lausanne, 20 Dec /64

54 L b p h decays Both signals clearly seen L b p p L b p K RAW yield: 31.9 ± 7.0 (stat.) RAW yield: 35.2 ± 6.7 (stat.) CP asymmetry measurements to follow shortly LPHE, EPFL, Lausanne, 20 Dec /64

55 H b h h : physics goals with the data sample Expected yields by end 2011 (1 fb -1 ) : CP asymmetry measurements in B 0 K p, B s p K and L b p h 2010 Measurement of relative branching ratios (with respect to B 0 K p) Mode Yield (1 fb -1 ) B 0 K p ~ 24 k B 0 p p ~ 6.5 k B s K K ~ 7 k L b p K/p ~ 1 k Relative B s KK / B 0 pk lifetime measurement Absolute B s KK lifetime measurement 2010(+11?) Potential discovery of rare modes B 0 KK, B s pp New Physics sensitive measurement of g - Sensitivity ~ 7º with 2 fb -1 according to MC studies In short: LHCb already competitive with CDF given the 2010 data sample! 2011 and beyond LPHE, EPFL, Lausanne, 20 Dec /64

56 LHCb MC sensitivity studies for L = 0.2 fb -1 LHCb statistical sensitivities to most relevant measurements for an integrated luminosity of 0.2fb-1 (then 1/sqrt(Lumi) scaled to 2 and 10 fb-1) LHCb physics roadmap document arxiv: Eduardo v2 Rodrigues [hep-ex] LPHE, EPFL, Lausanne, 20 Dec /64

57 B 0 pp direct and mixing-induced CP asymmetries (1/2) Time-dependent measurements BaBar and Belle still do NOT agree on direct CP asymmetry! LHCb 0.2 fb -1 expectation: s(c CP ) ~ 0.13 (stat.) s(s CP ) ~ 0.13 (stat.) (remember: signs of C and S depend on conventions and definitions) LPHE, EPFL, Lausanne, 20 Dec /64

58 B 0 pp direct and mixing-induced CP asymmetries (2/2) BaBar and Belle still do NOT agree on direct CP asymmetry! LHCb expectation: sort the situation out by end 2011 LPHE, EPFL, Lausanne, 20 Dec /64

59 The B ± h h h family Looking at the 6 decay modes (h = p, K, p) in ~ 26 pb -1 of 2010 data Signals found with the correct relative yields Mode BR (10-5 ) Signal* S/B p p p ± K p p ± K K p ± K K K ± p p p p p K ± (* not yet corrected for reconstruction and PID efficiencies) Note: Same topology starting point is common selection with no PID cuts In this family of decays reflections are an important component that needs removing - mainly from J/Y, Y(2S) m m ; D K p LPHE, EPFL, Lausanne, 20 Dec /64

60 B h h h : physics goals with the data sample Branching ratio measurements with respect to B K p p 2010 Dalitz plot amplitude analyses CP asymmetries in Dalitz plots (arxiv: [hep-ph]) Dalitz plot analysis for determination of g (arxiv:hep-ph/ , Phys. Rev. D 76 (2007), ) LPHE, EPFL, Lausanne, 20 Dec /64

61 B K p p the «reference» mode B + K + p + p - All other BRs measured wrt this mode Before removal of reflections PID cuts applied Special cuts for removal of reflections LPHE, EPFL, Lausanne, 20 Dec /64

62 Other B h h h modes (h = p, K) B + K + K - p + B + p + p + p - B + K + K - K + LPHE, EPFL, Lausanne, 20 Dec /64

63 The B p p h modes (h = p, K) B + p p K + B + p p p + LPHE, EPFL, Lausanne, 20 Dec /64

64 Summary 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! LPHE, EPFL, Lausanne, 20 Dec /64

65 Back-up slides

66 b-quark production at the LHC Gluon-Gluon-Fusion: p b x1 x2 p b s(pp H b X) = 75.3 ± 5.4 ± 13.0 mb (2<h<6) Cross sections predictions (PYTHIA) s = 7, 10, 14 TeV s inel ~ ( 0.89, 0.95, 1 ) 80 mb s bb ~ ( 0.44, 0.67, 1) 500 mb ~250 mb bb Production B ±, B 0, B s, B c, L b (40% 40% 10% 10%) 20x larger charm production Design L ~ 2 x cm -2 s -1 (tuned) ~ bb events / year (2 fb -1 ) q b q b 50 khz bb-events in LHCb LHCb Collaboration, Measurement of s(pp bbx) at s = 7 TeV in the forward region LPHE, EPFL, Phys. Lausanne, Lett. B Dec. (2010), ; arxiv: v2 [hep-ex] 66/64

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70 The LHCb detector Ring Imaging Cherenkov Calorimeters 250/300 mrad Acceptance 10 mrad pp collision «Tracking» detectors Muon System (side view) LPHE, EPFL, Lausanne, 20 Dec /64

71 LHC peak instantaneous luminosity Nominal instantaneous lumi : 2 x cm -2 s -1 ~ 1 month Peak luminosity increased by ~ 100 LPHE, EPFL, Lausanne, 20 Dec /64

72 Commissioning trigger nominal bunches Normalised efficiency (%) LHCb 2010 data taking efficiency All fills normalised to 1 pb -1 94% High luminosity with high mu Excellent efficiency 93-98% Detector Safety System Commercial Hardware fault (Apart from a few one-off problems) July August September October LPHE, EPFL, Lausanne, 20 Dec /64

73 Typical LHCb event LPHE, EPFL, Lausanne, 20 Dec /64

74 Typical LHCb event LPHE, EPFL, Lausanne, 20 Dec /64

75 Typical LHCb event LPHE, EPFL, Lausanne, 20 Dec /64

76 Why do we need 2 RICH detectors? Chrenkov angle vs. particle momentum Coverage of all particles from B ππ decays n = 1.03 aerogel RICH1 C 4 F 10 RICH2 n = n = CF 4 Two RICHes and 3 radiators cover the particle phase space almost completely LPHE, EPFL, Lausanne, 20 Dec /64

77 Other B D X modes already seen B 0 D 0 r Cousin mode B s D s r also looked for and evidence seen recently LPHE, EPFL, Lausanne, 20 Dec /64