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

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

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 = ± 0.10 ± 0.07 ps ps -1 <  m s < 21 ps 90% CL

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)

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 = ± 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

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

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

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

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

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

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

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 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

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(  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

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

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

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%

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

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

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

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

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

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

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.

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

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

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

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%

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

CKM 2006, Nagoya 15 th December 2006 B 0 s  J/  with ATLAS and CMSNicolò Magini 29 Results - summary  s /  s (stat) (untagged)0.017*CMS (30 fb -1 ) ATLAS (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

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

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

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)

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

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

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

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

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

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

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

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)