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B 0 s  J/   with the ATLAS and CMS detectors Nicolò Magini University and INFN, Firenze Nagoya, 15 th December 2006 CKM 2006 4 th International Workshop.

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Presentation on theme: "B 0 s  J/   with the ATLAS and CMS detectors Nicolò Magini University and INFN, Firenze Nagoya, 15 th December 2006 CKM 2006 4 th International Workshop."— Presentation transcript:

1 B 0 s  J/   with the ATLAS and CMS detectors Nicolò Magini University and INFN, Firenze Nagoya, 15 th December 2006 CKM 2006 4 th International Workshop on the CKM Unitarity Triangle

2 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 2Outline  The B 0 s  J/   decay  Trigger at ATLAS and CMS  Reconstruction and selection with ATLAS and CMS  Analysis and parameter extraction

3 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 3 s s B0sB0s B0sB0s B 0 s mixing B s are too heavy to be produced at  (4s) B factories  studied with high statistics at hadron colliders CDF and D0 results on mixing  s  s  Standard Model prediction for  s  s   s  s s  m s = 17.77 ± 0.10 ± 0.07 ps -1 17 ps -1 <  m s < 21 ps -1 @ 90% CL

4 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 4 B s  J/     +  - K + K - BR(B s  J/   )=(9.3±3.3)x10 -4 BR(J/  +  - ) =(5.93±0.06)% BR (  K + K - )=(49.2±0.6)% CP violation weak phase  s = 2  = 2 2  SM predicts  s ~ O(0.03) Angular distributions of decay products depend on  s,  s,  M s (B 0 s mixing) and  s (CP Violation)

5 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 5 B s  J/     +  - K + K - CP violating weak phase SM predicts （ UTFit ）  s = -2  s = -0.037 ± 0.002 s b t t V cb V * cs V tb V ts * BR(B s  J/   )=(9.3±3.3)x10 -4 BR(J/  +  - ) =(5.93±0.06)% BR (  K + K - )=(49.2±0.6)% s

6 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 6 New physics in  s  s  Present measurements still allow for almost arbitrary NP contributions to  s  Measuring  s will greatly constrain flavour violation in NP models

7 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 7 B s  J/   B s decay products are both J PC = 1 -- states The final state has CP = +1 if L = 0,2 and CP = -1 if L = 1 The two contributions with opposite CP can be separated with an angular analysis of the final decay products ℓ+ℓ+ ℓ-ℓ- K+K+ K-K- pp

8 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 8 Angular distributions Time evolution is a function of the transversity amplitudes A 0 (t), A || (t) (CP = +1) and A  (t) (CP = -1) Known functions of the three angles  describing decay product kinematics in the transversity basis

9 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 9 Angular distributions - tagged The distributions depend on 8 independent parameters Amplitudes |A || (0)|,|A  (0)| - Strong phases  1,  2 Width difference ΔΓ s = (Γ H - Γ L ) - Average width Γ s = (Γ H +Γ L )/2 Mass difference Δm s - Weak phase  s moduli 2 interference

10 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 10 Angular distributions - untagged Remarkable feature:  If  s ≠0 the distributions are still sensitive to the weak phase  s  Terms with  m s cancel: not necessary to resolve the very fast oscillations

11 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 11 B Physics at ATLAS /CMS  b production at LHC Luminosity  2x10 33 cm -2 s -1 (2009)   0.5 mb  about 10 6 bb pairs/sec  But minimum bias ~100x: must be rejected still keeping maximum bandwidth for discoveries TRIGGER IS FUNDAMENTAL TRIGGER IS FUNDAMENTAL

12 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 12 Main backgrounds  at LHC  Signal B 0 s  J/        K + K - 167 fb B 0 d  J/  K*  Exclusive bkg B 0 d  J/  K*       K  900 fb  Inclusive backgrounds :  b  J/  X  b  J/  X 51.4 nb  Prompt pp  J/  X  Prompt pp  J/  X 310 nb   In all samples : p T  GeV/c   In signal + B d bkg : p T  GeV/c

13 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 13 Main backgrounds  Signal B 0 s  J/        K + K - 1 ev B 0 d  J/  K*  Exclusive bkg B 0 d  J/  K*       K  50k ev  Generated with SIMUB  full angular distributions  Inclusive backgrounds :  b  J/  X  b  J/  X 200k ev  Combinatorial bb    Combinatorial bb   with M(  2.5-3.5 GeV/c 2 100k ev  Generated with PYTHIA  no angular distributions  Prompt pp  J/  X  Prompt pp  J/  X 50k ev J/   Generated with modified PYTHIA tuned on CDF J/  production cross sections   In all samples : p T  GeV/c   In signal + B d bkg : p T  GeV/c

14 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 14 The detectors CMSATLAS  Multipurpouse central detectors  Main features for B physics: Muon detectors for trigger & muon ID Precise inner tracking detectors

15 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 15 Trigger architecture CMS 40 MHz 50 (100) kHz 150 Hz ATLAS

16 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 16 Trigger selection - L1  Di-muon trigger at L1 ATLAS : p T (  ) > 6,3 GeV/c CMS : p T (  ) > 3,3 GeV/c Inner Detector Muon Trigger Chambers (RPC) Muon Precision Chambers (MDT) Muon Trigger Chambers (TGC) ATLAS LVL1 MUON Efficiency ~85%

17 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 17 Trigger selection - HLT  Decay chain reconstruction with fast/regional tracking in inner tracker at HLT (lifetime biased) J/ψ  mass distribution (HLT)  = 51 MeV/c 2 Signal *10 3 Inclusive b→J/ψ X Prompt J/ψ Transverse decay length significance CMS: HLT starts with J/y reco & prompt decay suppression, can also perform full decay chain reco

18 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 18 K+K+K+K+ K-K-K-K- s Offline reconstruction   reco with tracker + ID with muon detector  K reco with tracker  Common 4-track vertex  p(B 0 s ) // L  Flavour tagging

19 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 19 Kinematic fitting Constraints applied  Common 4 track vertex  J/  mass constraint  Vertex pointing constraint CMS  (m) = 14 MeV/c 2 ATLAS  (m) = 18 MeV/c 2

20 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 20 Proper time resolutions CMS -  t = 77 fs ATLAS -  t = 84 fs

21 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 21 Event yields 0.33109000CMS (10 fb -1 ) 0.30106000ATLAS (10 fb -1 ) Background (B/S)Signal Background composition  combinatorial  B 0  J/  K *0   +  - K ±  Ŧ ( )

22 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 22 Angular analysis  Goal: extract from the angular distributions of the decay products the parameters of interest (e.g.  s /  s,  s )  In principle: single maximum likelihood fit to extract the parameters simultaneously from all available data  In practice: many parameters, complicated distributions  use different multi-step approaches to fitting

23 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 23 First step: untagged fit  Example: CMS measurement of  s /  s,  s Angular distributions to extract signal B d  J/  K* bkg Combinatorial bkg  t  – selection efficiency as function of proper time & angles G s (m,m s  s  – mass resoultion (gaussian) Maximum likelihood fit with P.D.F.

24 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 24 Selection efficiency   (t,  )  As a function of proper time  As a function of angles

25 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 25 Results – untagged analysis  Statistical error for 100k evts (N SEL with L int = 10 fb -1 )  Syst. errors on  s for 13k evts (N SEL with L int = 1.3 fb -1 ) Main source is modeling of proper time bias  need control samples to measure in data CMS also evaluated Angular Moments analysis, results only slightly worse than MLH fit

26 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 26 Method of angular moments  The angular distributions of interest are complicated: define a set of 6 weighting functions w i to separate the 6 b i components

27 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 27 Next step: tagged fit  Example: ATLAS full angular analysis  Flavour tagging methods used:  SS jet-charge  Performance  =63%,  tag =38%  OS muon charge  Performance  =2.5%,  tag =24%

28 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 28 Results – ATLAS tagged analysis 0.080.03ATLAS (10 fb -1 )  s (stat err)  s /  s (stat err) correlations

29 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 29 Results - summary 0.009 0.018  s /  s (stat) (untagged)0.017*CMS (30 fb -1 ) 0.0460.01ATLAS (30 fb -1 )  s (stat)  s /  s (syst) Ultimate results for three years at nominal low luminosity * CMS syst. evaluated with 1.3 fb -1 sample

30 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 30Conclusions  ATLAS & CMS will be able to measure  s /  s with good precision  ATLAS & CMS can give good contributions to the evidence of a large NP effect  SM value of  s out of reach  that’s a job for LHCb

31 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 31Acknowledgements  M. Smizanska, J. Catmore for the ATLAS collaboration  V. Ciulli, N. Magini, L. Wilke, T. Speer, K. Prokofiev, S. Shulga, T. Ilicheva for the CMS collaboration

32 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 32References  CMS-NOTE 2006/121  ATLAS Physics and detector performance TDR. Vol. II, J. Catmore talk at BEACH2006, M. Smizanska (private communication)

33 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 33 prompt J/    +  -  Old PYTHIA (color singlet) underestimates pp  J/  X cross section by orders of magnitude (ref. CDF)  Modified PYTHIA version including color octet processes

34 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 34 B-Physics generators  SIMUB – CMS  Developed by Dubna group (Bel’kov, Shulga)  EVTGEN – ATLAS, LHCb

35 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 35 CMS -Offline reconstruction strategy  J/  reco  MuonReconstructors + MuonID on TkTracks  Combinatorial  + B s reconstruction  CombinatorialTrackFinder (p T min = 0.8 GeV/c)  No particle ID  K mass assignment  Loose mass/p T cuts to reduce combinations  Kinematic fitting

36 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 36 CMS - Muon Identification  Now available - MuonIdentification with outside propagation of tracker tracks searching for compatible hits in muon chambers  Assigns a “score” to track based on energy in calo & number of compatible mu hits

37 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 37 ATLAS sensitivity

38 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 38 ATLAS sensitivity

39 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 39 Resolutions - CMS Mass -  M = 14 MeV/c 2 Proper decay time -  t = 23  m/c  m  < 8 MeV/c 2

40 CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 40 Misalignment - CMS Proper decay time -  t = 32  m/c HLT Efficiency loss = -17% Short term alignment scenario: 1 fb -1 data (~ 2009)

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