1. Radiative Decays @ LHCb Vanya BELYAEVVanya BELYAEV (NIKHEF/Amsterdam & ITEP/Moscow) Vanya BELYAEV On behalf of LHCb Collaboration

2. Outline Radiative penguins & photon polarization in Radiative penguins & photon polarization in b→ s  transitions b→ s  transitions Event Selection Event Selection Probing for the photon polarization in B s →  Probing for the photon polarization in B s →  Early data Early data Summary Summary 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 2

3. Loops and Penguins Rare ( ≡ “loop-induced” ) and especially penguin-mediated decays are essential part of LHC(b) physics program: Rare ( ≡ “loop-induced” ) and especially penguin-mediated decays are essential part of LHC(b) physics program: Electroweak penguin B 0 →K *0  +  - Electroweak penguin B 0 →K *0  +  - talk by Will Reece talk by Will Reece Gluonic penguin B s →  Gluonic penguin B s →  Talk by Olivier Leroy, also charmless B-decays, talk by Lorence Carson Talk by Olivier Leroy, also charmless B-decays, talk by Lorence Carson Hunting for “ SUSY/Higgs penguin”: B s →  +  - Hunting for “ SUSY/Higgs penguin”: B s →  +  - talk by Diego Martinez Santos talk by Diego Martinez Santos And the radiative penguins are here … 10.9.2k+9 LHC(b) penguinarium LHC(b) penguinarium Vanya Belyaev: Radiative decays @ LHCb 3

4. Radiative penguins Radiative penguin decays of B + &B 0 mesons have been discovered by CLEO and both inclusive b→s  and exclusive decays have been intensively studied by CLEO, BaBaR and Belle Radiative penguin decays of B + &B 0 mesons have been discovered by CLEO and both inclusive b→s  and exclusive decays have been intensively studied by CLEO, BaBaR and Belle Br(b →s  ) is one of the most efficient killer for New Physics Models Br(b →s  ) is one of the most efficient killer for New Physics Models Belle has observed B s →  Belle has observed B s →  10.9.2k+9 Belle : O(1 B s →  )/day at Y(5S) Vanya Belyaev: Radiative decays @ LHCb 4

5. Why penguins are attractive? The clear picture in SM: The clear picture in SM: One diagram dominance One diagram dominance One Wilson coefficient C 7 eff (  ) One Wilson coefficient C 7 eff (  ) Reliable theoretical description at (N)NLO allows the numerically precise predictions Reliable theoretical description at (N)NLO allows the numerically precise predictions Loops Loops New Physics contribution can be comparable and even dominating to (small) SM amplitudes New Physics contribution can be comparable and even dominating to (small) SM amplitudes NP appears not only in modifications of Br, but also in asymmetries and the angular effects NP appears not only in modifications of Br, but also in asymmetries and the angular effects “Sensitive also to spin structure of NP” “Sensitive also to spin structure of NP” 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 5

6. Not so rare decays Br(B→K *0  ) = (4.3±0.4)x10 -5 Br(B s →  ) = (3.8±0.5)x10 -5 1-amplitude dominance strong phase appears at order of  s or 1/m b → “Direct” asymmetries are small (<1%) for b → s  & a bit larger O(10%) for b → d  Photons are polarized Mixing asymmetries vanishes, *BUT* Exclusive radiative penguins 10.9.2k+9 Suppressed by :  s, 1/m b or |V CKM | Vanya Belyaev: Radiative decays @ LHCb 6

7. Mixing asymmetries are vanished, but … B→ f CP  is not CP eigenstate!  R /  L ≈m s /m b B→ f CP  is not CP eigenstate!  R /  L ≈m s /m b Take it into account: Take it into account: SM: SM: C = 0 direct CP-violation C = 0 direct CP-violation S = sin2  sin  S = sin2  sin  A  = sin2  cos  A  = sin2  cos  10.9.2k+9 not suppressed! Vanya Belyaev: Radiative decays @ LHCb 7

8. B 0 → K S  0  BaBarBelle  (sin2  ) ~ 0.4 8

9.  s /  s ≠ 0 C is practically zero C is practically zero 1 diagram dominance 1 diagram dominance S is a product of CP-eigenstate fraction and (small) phase difference of B s oscillation and b→s  penguin S is a product of CP-eigenstate fraction and (small) phase difference of B s oscillation and b→s  penguin double smallness is SM double smallness is SM A  is just a fraction of CP-eigenstate A  is just a fraction of CP-eigenstate ≡ Fraction of wrongly polarized photons ≡ Fraction of wrongly polarized photons No “other” suppression factors, only  s /  s No “other” suppression factors, only  s /  s Essentially we study CP-violation in B s →  as an instrument to probe Lorentz structure of b→s  transitions F.Muheim, Y.Xie & R.Zwicky, Phys.Lett.B664:174-179,2008 F.Muheim, Y.Xie & R.Zwicky, Phys.Lett.B664:174-179,2008 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 9

10. Expected performance for B s →  at LHCb What we “know” now: What we “know” now: The yield is 11k per 2 fb -1 (and 70k of B 0 → K *0  ) The yield is 11k per 2 fb -1 (and 70k of B 0 → K *0  ) Background is Background is <6k @ 90%CL <6k @ 90%CL The mass resolution ~96 MeV/c 2 The mass resolution ~96 MeV/c 2 Ecal resolution Ecal resolution The proper time resolution:  ~78fs The proper time resolution:  ~78fs 50/50  1 =52fs,  2 =114fs 50/50  1 =52fs,  2 =114fs L.Shchutska et al, CERN-LHCb-2007-030 L.Shchutska et al, CERN-LHCb-2007-030 10.9.2k+9 LHCb : O(3 B s →  )/hour at 2x10 32 Full Monte Carlo simulation Vanya Belyaev: Radiative decays @ LHCb 10

11. Trigger Hardware L0 trigger for photons with high E T Hardware L0 trigger for photons with high E T Next trigger levels (software) : Next trigger levels (software) : Photon confirmation (& suppression of merged   ) and single (or pair) detached track reconstruction Photon confirmation (& suppression of merged   ) and single (or pair) detached track reconstruction  ~ 70%  ~ 70% Full reconstruction of B s →  candidate Full reconstruction of B s →  candidate Reconstruction of  -candidate Reconstruction of  -candidate “inclusive  ” trigger “inclusive  ” trigger More details in dedicated talk by Leandro de Paula 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 11 Large overlap, high redundancy & robustness:  ~ 95%

12. Event selection B -decay products do not point to reconstructed primary vertices Exclusively reconstructed B -candidate does point to primary vertex B -candidate is associated with the primary vertex with minimal impact parameter (significance) 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 12

13. Signal proper time resolution 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 13

14. Sensitivity to sin2  To evaluate our sensitivity to sin2  To evaluate our sensitivity to sin2  toy Monte Carlo (10 4 experiments) toy Monte Carlo (10 4 experiments) Unbinned maximum likelihood fit Unbinned maximum likelihood fit Proper lifetime & error Proper lifetime & error Reconstructed mass Reconstructed mass Per-event proper time errors Per-event proper time errors Resolutions & Efficiencies from full MC Resolutions & Efficiencies from full MC Parameterize the background from mass-sidebands Parameterize the background from mass-sidebands Important ingredient – proper time acceptance function Important ingredient – proper time acceptance function L.Shchutska et al, CERN-LHCb-2007-147 L.Shchutska et al, CERN-LHCb-2007-147 10.9.2k+9 m(B s ) = 5.367 GeV/c 2  (B s ) = 1.43 ps  s = 0.084 ps -1  m s = 17.77 ps -1 Vanya Belyaev: Radiative decays @ LHCb 14

15. Proper time acceptance 10.9.2k+9 a = 0.74 ps -1 a = 0.74 ps -1 c = 1.86 c = 1.86 dN/dt  s (t)  s (t) Vanya Belyaev: Radiative decays @ LHCb 15

16. Proper time acceptance It is a vital to know it with very high precision It is a vital to know it with very high precision 5% bias in “ a ” -> bias in sin2  ~ 0.2 5% bias in “ a ” -> bias in sin2  ~ 0.2 We are planning to calibrate it using three techniques: We are planning to calibrate it using three techniques: B 0 → K *0  B 0 → K *0  B s →  J/  B s →  J/  “per-event-acceptance” (“swimming” method) “per-event-acceptance” (“swimming” method) The acceptance could be extracted from data for all cases The acceptance could be extracted from data for all cases E.g. with ~O(1%) precision for B 0 → K *0  E.g. with ~O(1%) precision for B 0 → K *0  10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 16

17. Background parameterization Fit separately left and Fit separately left and right sidebands right sidebands 10.9.2k+9 LeftRight Vanya Belyaev: Radiative decays @ LHCb 17

18.  (A ,C,S) Results:  (A ,C,S) 10.9.2k+9  (A  )=0.22  (S)=  (C)=0.11 Vanya Belyaev: Radiative decays @ LHCb 18 2fb -1

19. Already with “early” data the measurements of direct CP-asymmetry in B→ K *0  Already with “early” data the measurements of direct CP-asymmetry in B→ K *0  Double ratio: Double ratio: Measurement of B→  K  Measurement of B→  K  “early measurements” 10.9.2k+9 Vanya Belyaev: Radiative decays @ LHCb 19 The first 13 minutes @ nominal luminosity nominal luminosity B→ K *0 

20. Conclusions LHCb has good potential for measurement of photon polarization in B s →  decay LHCb has good potential for measurement of photon polarization in B s →  decay For 2 fb -1 : For 2 fb -1 :  (A  )=0.22,  (S)=  (C)=0.11  (A  )=0.22,  (S)=  (C)=0.11 The determination of proper time acceptance function from data in under the study: The determination of proper time acceptance function from data in under the study: Three methods Three methods The result has moderate dependency on B/S The result has moderate dependency on B/S Stay tuned and wait for more news Stay tuned and wait for more news 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 20

21. Backup slides 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 21

22. Example of models Anomalous right-handend top couplings J.P.Lee’03 Anomalous right-handend top couplings J.P.Lee’03 10.9.2k+9  = -cos 2   = -cos 2  Vanya Belyaev: Radiative decays @ LHCb 22

23. B: proper-time in sidebands Fit separately left and right sidebands Fit separately left and right sidebands 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 23

24. Signal proper time resolution as function of cos  10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 24

25. Signal proper time resolution as function of cos  10.9.2k+9 -1.0 : -0.5 -0.5 : -0.15 -0.15 : 0.3 0.3: 1.0 Vanya Belyaev: Radiative decays @ LHCb 25

26. The shape of background Vary the “short/long”-lived components Vary the “short/long”-lived components 10.9.2k+9 Relative change Absolute change Vanya Belyaev: Radiative decays @ LHCb 26

27. Stability tests: B/S There is some dependency on B/S level: There is some dependency on B/S level: 10.9.2k+9 Conservative UL @ 90% CL Vanya Belyaev: Radiative decays @ LHCb 27

28. Results: pulls 10.9.2k+9 AAAA CS Vanya Belyaev: Radiative decays @ LHCb 28

29.  s /  s Resolution and  s /  s Vary the proper time resolution Vary the proper time resolution Use simple model with two Gaussians and vary the proportion Use simple model with two Gaussians and vary the proportion 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 29

30. Acceptance function 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 30

31. Background parameterization 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 31

32. Likelihood 10.9.2k+9Vanya Belyaev: Radiative decays @ LHCb 32