1. Prospect for  s measurement at LHC Alessia Satta on behalf of the LHCb collaboration + some Atlas and CMS results Physics at LHC, 3 rd october 2008

2. 10/03/2008 Alessia Satta INFN 2 Content Introduction Introduction Analysis strategy Analysis strategy LHC prospects LHC prospects

3. 10/03/2008 Alessia Satta INFN 3  s angle in one slide the CKM unitarity triangle in Bs system the CKM unitarity triangle in Bs system Possible to extract from CPV in Bs if b  ccs decay GOLDEN MODE J/ Possible to extract from CPV in Bs if b  ccs decay GOLDEN MODE J/ SM predicts a very small value: 2 s =0.037±0.002 SM predicts a very small value: 2 s =0.037±0.002 B0sB0s B0sB0s u, c, t W, ? B0sB0s b s b s W s b c c s s + Bs f=CP(f) mixing decay Ψ,cΨ,c Φ, 

4. 10/03/2008 Alessia Satta INFN 4 Interesting ! Tevatron result is larger that SM prediction by 2.2 (arXiv:0808.1297) Tevatron result is larger that SM prediction by 2.2 (arXiv:0808.1297) Exciting for NP searches but not easy to settle down by tevatron alone: room for LHC Exciting for NP searches but not easy to settle down by tevatron alone: room for LHC CDF Probability of 5  observation ss 6 fb (2009) 8 fb (2010)

5. 10/03/2008 Alessia Satta INFN 5 Formulas of decay rate Bs  J/sum of CP +/- Bs  J/sum of CP +/- Angular analysis to decouple the eigenstatesAngular analysis to decouple the eigenstates A 0, A ║, A ┴ : transition amplitudes in a given polarization state f(ρ): angular distribution for a given polarization state T U V :Time dependence Tagged analysis sensitive to cos(2) sin(2) If P  anti P (U,V) +  (U,V) – =1  -1 Untagged analysis still some sensitive to  s

6. 10/03/2008 Alessia Satta INFN 6 Analysis in a nutshell Fit time dependent angular distribution Fit time dependent angular distribution Large statistics is mandatoryLarge statistics is mandatory Large  bb, good trigger Large  bb, good trigger Good signal background separationGood signal background separation –benefit a lot for dimuon in final state –benefit a lot for dimuon in final state Good time resolutionGood time resolution Good tracking (angular resolution)Good tracking (angular resolution) Good tagging (for tagged analysis)Good tagging (for tagged analysis)

7. 10/03/2008 Alessia Satta INFN 7 Beauty in LHC experiment B dedicated experiment B dedicated experiment Forward spectrometer to max. bb in acceptance Forward spectrometer to max. bb in acceptance 1.9<<4.5 =230b 1.9<<4.5 =230b Locally reduced L to maximize events with one interaction Locally reduced L to maximize events with one interaction General purpose experiment General purpose experiment ||<2.5, =100b ||<2.5, =100b B physics mainly first years (L=10 33 ) B physics mainly first years (L=10 33 )  =100  b 230  b Gain in low Pt

8. 10/03/2008 Alessia Satta INFN 8 Trigger Crucial since only 1% of  tot is b production and decay chain of interest has BR 3*10 -5 Crucial since only 1% of  tot is b production and decay chain of interest has BR 3*10 -5 Hardware and sw levels for all experiments: Hardware and sw levels for all experiments: L0 rate 1MHz (LHCb) ~100kHz (ATLAS CMS)L0 rate 1MHz (LHCb) ~100kHz (ATLAS CMS) HLT rate 2kHz (LHCb) ~100Hz (ATLAS CMS)HLT rate 2kHz (LHCb) ~100Hz (ATLAS CMS) ATLAS and CMS general purpose so limited bandwidth for b physics ( O(10%)) ATLAS and CMS general purpose so limited bandwidth for b physics ( O(10%)) All experiments have a dimuon trigger to select signal events All experiments have a dimuon trigger to select signal events ATLAS /CMS Pt and Mass based cut + IP, rate ~HzATLAS /CMS Pt and Mass based cut + IP, rate ~Hz LHCb : 600Hz of IP unbiased dimuon trigger  signal recostruction as offline (loser cut) noIP. Very high efficiency on selected events of trigger ( ~ 70%)LHCb : 600Hz of IP unbiased dimuon trigger  signal recostruction as offline (loser cut) noIP. Very high efficiency on selected events of trigger ( ~ 70%)

9. 10/03/2008 Alessia Satta INFN 9 Signal reconstruction Standard cuts : Pt, invariant mass, PID, vertex quality, B pointing to primary vertex, B decay length (only ATLAS & CMS) Standard cuts : Pt, invariant mass, PID, vertex quality, B pointing to primary vertex, B decay length (only ATLAS & CMS) PID PID Similar muon ID performance for ATLAS CMS and LHCbSimilar muon ID performance for ATLAS CMS and LHCb ATLAS and CMS no Kaon pid capability, LHCb has 2 Riches that ensures good K identification (K  K)~80% e(->K)~ 3%ATLAS and CMS no Kaon pid capability, LHCb has 2 Riches that ensures good K identification (K  K)~80% e(->K)~ 3%

10. 10/03/2008 Alessia Satta INFN 10 Signal and background L (fb -1 ) evB/SBackgroundATLAS1090k0.18 long lived B CMS10109k0.25 LHCb2114k2.0 1.8 prompt* 1.8 prompt* +0.2 long lived * Selection with no bias in IP to avoid acceptance in proper time and angle

11. 10/03/2008 Alessia Satta INFN 11 Proper time resolution Need to resolve fast Bs oscillation: s extraction sensitivity ~ exp(-0.5* t 2 m s 2 ) Need to resolve fast Bs oscillation: s extraction sensitivity ~ exp(-0.5* t 2 m s 2 ) Atlas 83fs CMS 77fs LHCb 39fs Atlas 83fs CMS 77fs LHCb 39fs LHCb vertex detector close to IP (0.8cm wtr 4.4cm)LHCb vertex detector close to IP (0.8cm wtr 4.4cm) LHCb P resolution a factor 2 betterLHCb P resolution a factor 2 better LHCb trigger collects 600Hz unbiased dimuon (also) to calibrate proper time on dataLHCb trigger collects 600Hz unbiased dimuon (also) to calibrate proper time on data

12. 10/03/2008 Alessia Satta INFN 12 Tagging (1-2w) 2 Muon0.8 Electron0.4 K (OS) 1.5 K (SS) 2.1 Q vertex 1.1 Combined6.2 Sensitivity goes as (1-w) 2 Sensitivity goes as (1-w) 2 ATLAS : e,  Qjet 4.6% ATLAS : e,  Qjet 4.6% CMS : NA CMS : NA lepton (  ±, e ± ) “Same side” “Opposite side” Signal B Tagging B Primary vertex kaon (K ± ) D Kaon from fragmentation vertex charge ~1cm

13. 10/03/2008 Alessia Satta INFN 13 Tagging from data LHCb plans to extract the mistag fraction from control sample with large statistics LHCb plans to extract the mistag fraction from control sample with large statistics Opposite Side is extracted from B +  J/ K + or Bd  J/ K* Opposite Side is extracted from B +  J/ K + or Bd  J/ K* Common selection as much as possible with signal sample to avoid phase space bias to opposite bCommon selection as much as possible with signal sample to avoid phase space bias to opposite b Large statistics is expected:in 2 fb -1Large statistics is expected:in 2 fb -1 650k Bd  J/ K* 650k Bd  J/ K* 1 million for B +  J/ K* 1 million for B +  J/ K* Same Side Same Side From Bs->D s From Bs->D s 

14. 10/03/2008 Alessia Satta INFN 14 Acceptance proper time and angles No bias from selection Theory Selected events Theory Selected events Theory Selected events A common selection with Bd  J/Y K* allows to test the acceptance on data (650kev/2fb)

15. 10/03/2008 Alessia Satta INFN 15 Systematic studies (s) vs Prompt bkg fraction (s) vs long lived bkg fraction (s) vs proper time resoltuion (s) vs mistag fraction Crucial : mistag and proper time Angular resolution is very good and has negligible impact on s error

16. 10/03/2008 Alessia Satta INFN 16 Sensitivity ATLASCMSLHCb L (fb-1) 10102.0 Yield (k) 90109114 B/S0.180.252.0 (M Bs ) (MeV) 16.51417  t (fs) 837739 Eff(tag) (%) 4.6NA6.2 (2s) 0.08NA0.03 Even with fraction of one year nominal luminosity good sensitivity

17. 10/03/2008 Alessia Satta INFN 17 More channels in LHCb Other b  ccs decay can be added Other b  ccs decay can be added Low yield, experimental signature more difficult, larger background, degradation of proper time resolution for Ds DsLow yield, experimental signature more difficult, larger background, degradation of proper time resolution for Ds Ds No angular analysis is requiredNo angular analysis is required Decay mode Events in 2fb -1 (2s) J/  8.5 k 0.109 J/  3 k 3 k0.142 J/’  2.2 k 0.154 J/’  4.2 k 0.08 cccc 3 k 0.108 Ds Ds 4 k 0.133 All0.046

18. 10/03/2008 Alessia Satta INFN 18 Summary All experiments will collect large sample of golden mode decay for s measurement All experiments will collect large sample of golden mode decay for s measurement Great potential to improve significantly the existing measurement Great potential to improve significantly the existing measurement even with fraction of nominal year even with fraction of nominal year

19. Spares

20. 10/03/2008 Alessia Satta INFN 20 CPV in Bs  ccs (s) Golden mode :J/     Golden mode :J/     Large BRLarge BR Clean experimental signatureClean experimental signature Easy to triggerEasy to trigger Sum of even and odd CP eigenstatesSum of even and odd CP eigenstates  angular analysis Other modes J/, J/ ’,  C , Ds Ds Other modes J/, J/ ’,  C , Ds Ds Low yield, experimental signature more difficult, larger background, degradation of proper time resolution for Ds DsLow yield, experimental signature more difficult, larger background, degradation of proper time resolution for Ds Ds No angular analysis is requiredNo angular analysis is required total even odd background

21. 10/03/2008 Alessia Satta INFN 21 Sensitivity study Due to limited MC statistics we use the full Monte Carlo to estimate all the relevant quantities: yield, background fraction, mass, proper time/ angle distributions, resolutions and acceptances and plug them in hundreds of toy MC to estimate the sensitivity to 2 bs (and the others parameters), through an unbinned maximum likelihood fit: 6 observables:: proper time,, 3 angles,, tagging answer =0,,+1,,1,mass 8 physical parameterrs:: 2s,, s, s,  R(T) R(0), (T),(0) + detector parameters (resolutions, acceptances, tagging)

22. 10/03/2008 Alessia Satta INFN 22 CMS time and angular acceptance