B 0 s  J/   LHC review Nicolò Magini University and INFN, Firenze For the ATLAS, CMS and LHCb collaborations Oxford, 28 th September 2006 Beauty 2006 The 11 th International Conference on B-Physics at Hadron Machines

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 2Outline  B 0 s mesons and the B 0 s  J/   decay  Reconstruction and selection with LHC detectors  Analysis and parameter extraction

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 3 s s B0sB0sB0sB0s B0sB0sB0sB0s 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 4 sss  s  s    different masses & lifetimes First hint of non-zero difference at CDF and D0:  s  s  s  s 

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 5 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)

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 6 B s  J/     +  - K + K - CP violating weak phase SM predicts  s = 2  s ~ O(0.03) 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 7 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 8 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 9 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 10 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 11 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 12 B Physics at LHC b production at LHC Luminosity 2x10 33 cm -2 s -1 (ATLAS, CMS 2009) 2x10 32 cm -2 s -1 (LHCb)  0.5 mb  about 10 6 (10 5 ) bb pairs/sec

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 13 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 14 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 15 The detectors CMS LHCb  Dedicated forward detector  RICH for PID  Triggering VELO ATLAS  Multipurpouse central detectors

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 16 Trigger selection  Di-muon trigger at L1  Decay chain reconstruction with fast/regional tracking at HLT (lifetime biased) ATLAS/CMS Details in talks by J. Kirk and E. Rodrigues ATLAS : p T (  ) > 6,3 GeV/c CMS : p T (  ) > 3,3 GeV/c LHCb  Di-muon trigger at L0  L1/HLT: lifetime unbiased single & di-muon streams + lifetime biased J/  stream LHCb :  p T (     ) > 1.5 GeV/c

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 17 K+K+K+K+ K-K-K-K- s Offline reconstruction   reco with tracker + ID with muon detector  K reco with tracker - ID only in LHCb  Common 4-track vertex  p(B 0 s ) // L  Flavour tagging

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 18 Offline reconstruction  Full reconstruction of tracks in tracker  p T min = 0.8 GeV/c  Extrapolation of  to muon detector  Combinatorial decay chain reconstruction  K mass assignment  Loose mass/p T cuts to reduce number of combinations  Kinematic fitting

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 19 Kinematic fitting Constraints applied  Common 4 track vertex  J/  mass constraint  Vertex pointing constraint CMS Mass resolution = 14 MeV/c 2

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 20 Proper time resolutions CMS -  t = 77 fs LHCb - = 36.0 fs ATLAS -  t = 84 fs

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 21 Event yields SignalBackground (B/S) ATLAS (10 fb -1 ) CMS (10 fb -1 ) LHCb (2 fb -1 ) Background is mostly combinatorial for LHCb, combinatorial + B 0  J/  K *0   +  - K ±  + for ATLAS/CMS ( )

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò 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.

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 24 Selection efficiency   (t,  )  As a function of proper time  As a function of angles

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 25 Results – untagged analysis  Statistical error for 100k evts (N SEL with L int = 10 fb -1 )  Systematical errors 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 27 Next step: tagged fit  Example: LHCb one-angle distribution analysis  Flavour tagging methods used:  OS l, OS K, OS Vtx charge, SS K  Performance  =57%,  tag =33%   eff =6.6%   m s and  tag determined using B s  D s  as control sample

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 28 Results: tagged analysis  LHCb also combines other lower statistics decays to CP eigenstates (no angular analysis)  Could also add J/   e + e - channel (not included here, statistics 1/6 of J/    +  - )

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 29 Results - summary  s /  s (stat err)  s (stat err) ATLAS (10 fb -1 ) CMS (10 fb -1 ) (untagged) LHCb (2 fb -1 ) Results for one year at nominal low luminosity

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 30Conclusions  Any large NP effect will be seen “soon”  SM value of  s will be found at 3  within 5 years data taking at LHCb  ATLAS & CMS can also give good contributions to the measurement

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò 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  J. Van Hunen, L. Fernandez for the LHCb collaboration

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 32References  CMS-NOTE 2006/121  LHCb NOTE 2006/047 and L. Fernandez, PhD Thesis  ATLAS Physics and detector performance TDR. Vol. II

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 34 B-Physics generators  SIMUB – CMS  Developed by Dubna group (Bel’kov, Shulga)  EVTGEN – ATLAS, LHCb

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò 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

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 37 ATLAS sensitivity

Beauty 2006, Oxford 28 th September 2006 B 0 s  J/  LHC reviewNicolò Magini 38 Resolutions - CMS Mass -  M = 14 MeV/c 2 Proper decay time -  t = 23  m/c  m  < 8 MeV/c 2