LHCb-Babar Meeting 8 April Paul Soler University of Glasgow and Rutherford Appleton Laboratory A first look at B s J/ in LHCb

2 LHCb-Babar Meeting, 4 April 2005 Contents 1.Motivation 2.Physics aims 3.Angle 3.Angle from B s J/ 4.LHCb Experiment 5.Analysis of B s J/ 6.Toy Monte Carlo 7.Sensitivity 8.New Physics 9.Conclusions Work carried out in collaboration with: Stuart Paterson (Glasgow) Andrew Pickford (Glasgow) Borrowed from: G. Ravens analysis in 2003

3 LHCb-Babar Meeting, 4 April 2005 Motivation B s J/ B d J/ s B s J/ is the gold plated decay mode in the B s system, similar to the B d J/ s in the B d system o This mode is theoretically clean (very small penguin contributions). It provides a measurement of the unitarity angle, which is predicted to be very small (~0.02) in the SM. o Sensitive to new physics o Exploits the production capabilities of B s mesons at the LHC (not available at B-factories) o Exploits UK investment in the RICH and VELO detectors

4 LHCb-Babar Meeting, 4 April 2005 Physics aims o CKM matrix: CKM matrix provides link between mass eigenstates and weak eigenstates Experimentally:

5 LHCb-Babar Meeting, 4 April 2005 Physics aims _ :B d -B d Mixing Phase :Weak Decay Phase _ :B s -B s Mixing Phase Standard Model: CKM matrix in Wolfenstein parametrization ~O( 5 ): (From CKM-fit hep-ph/ )

6 LHCb-Babar Meeting, 4 April 2005 Physics aims o Two main unitarity triangles: Re Im 1 Re Im (db)(ut)

7 LHCb-Babar Meeting, 4 April 2005 Physics aims o Channels to be used to extract unitarity triangles:

8 LHCb-Babar Meeting, 4 April 2005 from B s J/ Diagrams) from B s J/ Diagrams) Decay Mixing (This is not Wolfenstein parameter!)

9 LHCb-Babar Meeting, 4 April 2005 from B s J/ Asymmetry) from B s J/ Asymmetry) o Asymmetry: (if J/ is eigenstate) But J/ is not pure CP eigenstate: CP even CP odd CP even

10 LHCb-Babar Meeting, 4 April 2005 from B s J/ Non-CP) from B s J/ Non-CP) o Change due to mixed eigenstate: The effect of the CP admixture is to dilute extraction of and to add a small coefficient in front of cos( m s ) since:

11 LHCb-Babar Meeting, 4 April 2005 from B s J/ Transversity) from B s J/ Transversity) o Extraction of CP eigenstates (transversity analysis): Three polarization states B sJ/ (l + l - ) (K + K - ) has three angles but can be put into J/ reference frame with only one angle (the transversity tr ) that comes out of (K + K - ) decay plane. J/ rest frame

12 LHCb-Babar Meeting, 4 April 2005 o Angular distribution in transversity: o Once CP eigenstates established, the analysis proceeds in the same manner to establish CP asymmetries. o References: –Durham workshop CERN-TH/ (hep-ph/ ) –LHCb notes: LHCb & G. Raven, LHCb and LHCb –B decays at the LHC: CERN-TH/ from B s J/ (Transversity) from B s J/ (Transversity)

13 LHCb-Babar Meeting, 4 April 2005 LHCb Experiment o LHCb Detector: forward single arm spectrometer at LHC Acceptance: mrad bending mrad non-bending

14 LHCb-Babar Meeting, 4 April 2005 LHCb Experiment o Exploit VELO for B s proper time measurement (B s oscillations) o Proper time resolution: ~40 fs m s sensitivity: 68 ps -1 (Standard Model ~ 20 ps -1 ) Exploit RICH for particle identification: (K + K - ) PID: -K separation GeV RICH1 RICH2

15 LHCb-Babar Meeting, 4 April 2005 B s J/ (Da Vinci Analysis) Real MC Data Combine to select Bs Select Ф Select J/ψ Calculate Transversity Write Histos & NTuples B s J/ Work flow of B s J/ analysis using Da Vinci (LHCb analysis package) First ever LHCb analysis run on the Grid (GLite) by S Paterson

16 LHCb-Babar Meeting, 4 April 2005 B s J/ (Da Vinci Analysis) B s J/ Ran with 100,000 B s J/ signal events Efficiency J/ 14.4% Energy resolution: 13 MeV Efficiency 9.8% Energy resolution: 9 MeV

17 LHCb-Babar Meeting, 4 April 2005 B s J/ (Da Vinci Analysis) B s Efficiency ~ 8.2% Energy resolution: 17 MeV Event selection quite clean Transversity distribution looks promising Contributions from CP odd (=1) & CP even ( =0,2) states

18 LHCb-Babar Meeting, 4 April 2005 B s J/ (Da Vinci Analysis) LHCb by Gerhard Raven, used a toy MC for re- optimization TDR (20% CP odd; 80% CP even) Very similar to distribution extracted. Need to fit to CP-odd versus CP-even

19 LHCb-Babar Meeting, 4 April 2005 B s J/ (G. Raven toy MC) Proper time resolution: 38 fs (G Raven LHCb ) Annual yield: Assume L int =2 fb -1 (10 7 s at 2x10 32 cm -2 s -1 ); bb =500 b; f B =10% for B s hadronization; BR vis =3.1x10 -5 Implies: 113 k events per year (with 8.2% efficiency)

20 LHCb-Babar Meeting, 4 April 2005 B s J/ (G. Raven toy MC) G. Ravens toy Monte Carlo varied a number of parameters to extract sensitivities _ q=+1(-1) for events tagged as B s (B s ) w=wrong tag fraction (=0.5 for untagged) Assumed Q= tag (1-2w) 2 =4.5% (w=35%, tag =50%). Untagged sample can be used to extract lifetime difference: One can fit for 5 parameters:

21 LHCb-Babar Meeting, 4 April 2005 B s J/ (G. Raven toy MC) Results:

22 LHCb-Babar Meeting, 4 April 2005 Sensitivity B s J/ Sensitivity B s J/ o In one year expect ~ 113 k events (negligible background) sin depending on ) In five years: sin (Standard Model: sin One year

23 LHCb-Babar Meeting, 4 April 2005 New Physics o Left-Right symmetric models (eg. SB-LR)

24 LHCb-Babar Meeting, 4 April 2005 Conclusions B s J/ is a very promising channel to study at LHCb Not accessible at B factories or Tevatron Standard Model prediction for is very small (~ 0.02) New Physics could make significantly larger than SM Started analysis of B s J/ and can achieve yields of ~100k events per year Using Toy Monte Carlo (G Raven), LHCb can probe to values very close to SM predictions, sin within 1 year