1. 6 th International Conference on Hyperons, Charm and Beauty Hadrons July 2, 2004 Rare B Decays at LHC Sébastien VIRET Laboratoire de Physique Subatomique et de Cosmologie, Grenoble ATLASATLAS 1. Presentation 2. Not so rare: B  X  3. Rare: B  X     4. Very rare: B  +  - 5. Conclusions Outline

2. ATLASATLAS 1. Presentation 2. Not so rare: B  X  3. Rare: B  X     4. Very rare: B  +  - 5. Conclusions 1 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret

3. 2 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS Rare B-Decays From ‘not so rare’ to ‘very rare’ 10 -5 10 -6 10 -7 10 -8 10 -9 10 -10 Branching ratio Radiative penguins: B d  K  , B s  B d  Electroweak penguins: B d  K   B d  B s  B d  Many interesting observables inaccessible to classic B-factories Not accessible to B-factories (No B s at B-factories) (No precision measurements at B-factories) Need a rare B-factory LHC  first results in 2008 Super-BaBar? Super-BELLE?

4. 3 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS The Detector LHCb Since 2003: reoptimized detector (VELO, RICH, TT, tracking stations)  Main characteristics: 4.6x10 11 Acceptance 1.9<  <4.9 p T b >2GeV 230  barn  bb Acceptance Lumi.( in cm -2 s -1 ) 2x10 32 bb pairs/year

5. 4 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS The Detector ATLAS & CMS ATLAS CMS Acceptance |  <2.5 p T b >10GeV 100  barn  bb Acceptance Lumi.( in cm -2 s -1 ) 2x10 33 & 10 34 2x10 12 & 10 13 bb pairs/year

6. 5 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS B production at LHC Rare B Factory ? LHC = Rare B factory LHCbATLAS/CMS Luminosity (in cm -2 s -1 ) 2x10 32 2x10 33 & 10 34 bb pairs/year4.6x10 11 2x10 12 & 10 13  But trigger challenging   inelastic  = 80 mbarn  rare B  ~ picobarn  femtobarn

7. 6 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS LHCb Trigger Strategy For Rare B decays Electromagnetic triggerMuon & Di-Muon Rate (in Hz) 10 7 10 6 10 5 10 4 10 3 10 2 L0 L1 HLT 1 MHz 40 kHz 200 Hz Radiative decaysOther decays Vertex reconstruction, topological cuts (IP, displaced vertex,…) Full B reconstruction Trigger entirely dedicated to B decays  Low P t thresholds

8. 7 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS ATLAS & CMS Trigger Strategy For Rare B decays Single Muon + Electromagnetic trigger Di-Muon Rate (in Hz) 10 7 10 6 10 5 10 4 10 3 10 2 L1 L2 EF 75 kHz 3 kHz 100 Hz Radiative decaysOther decays ID reco. + Photon identification ID reco. + Di-Muon confirmation Full B reconstruction Bandwith constraints: 200 Hz at L2, 20 Hz at EF (ATLAS)  High P t thresholds

9. ATLASATLAS 1. Presentation 2. Not so rare: B  X  3. Rare: B  X     4. Very rare: B  +  - 5. Conclusions 8 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret

10. 9 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS Radiative penguins Physics interest & observables Isospin Violation bs  u bs  d CP Violation bs  bs  bs  ? Branching ratio enhancement by new contributions Interesting Channels (only exclusive at LHC): B d  K * , B d , B d , B s ,… Interesting measurements: B s radiative penguins accessible at LHC

11. 10 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS Radiative penguins LHCb  Estimations for one year @ 2x10 32 cm –2 s -1 (2fb -1 ): 9300 B s  35000 B d  K *0   Study done with reoptimized detector & realistic trigger simulation: Specific background under control B        also studied, lots of accessible channels  =65 MeV/c 2  =64 MeV/c 2

12. 11 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS Radiative penguins ATLAS BdK*BdK* B s  Preliminary results Non-optimized offline cuts, resolution (>100 MeV/c 2 ) could be improved.  Estimations for one year @ 2x10 33 cm –2 s -1 (20fb -1 ): [2500,3200] B s  [4200,8500] B d  K *0  Trigger strategy dependent

13. 12 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS Radiative penguins ATLAS/LHCb comparison after 1 year ATLAS LHCb ATLAS LHCb BdK*BdK* B s  S/B >1.3 >0.4 >0.04 >0.01 Int. lumi. 20 fb -1 2 fb -1 S/√B >5 >7 >210 >60 Results limited by background statistics, S/B might be much better (particularly for B s ) Significant amount of statistics after just one year of LHCb Parallel measurements possible with ATLAS if radiative penguin trigger accepted

14. ATLASATLAS 1. Presentation 2. Not so rare: B  X  3. Rare: B  X     4. Very rare: B  +  - 5. Conclusions 13 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret

15. 14 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS B  K *     Experimentally speaking… Branching ratio enhancement by new contributions bs  ?  CP Violation bs  bs    Forward-Backward Asymmetry (Dimuon-cms system)    K *0 BdBd  Many interesting observables: … and also the di-muon mass spectrum,etc…

16. 15 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS B  K *     Hunting New Physics Phys.Rev. D61 (2000) 074024  Differences between SM and models predicting C 7  eff >0 (SM predicts C 7  eff <0) FB Asymmetry Large differences for small s if C 7  eff >0 SUSY 1, 2, and SM with C 7 eff <0 SUSY 1 & 2 with C 7 eff >0 Di-muon mass spectrum Large theoretical uncertainties SUSY 1 & 2 SM w/uncert.

17. 16 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS B  K *     LHCb Estimation with reoptimized detector & trigger simulation: B d mass resolution√S resolution Integrated on whole di-muon mass spectrum  BA resolution For Forward-Backward asymmetry measurement  Estimations for one year @ 2x10 32 cm –2 s -1 (2fb -1 ): 4400 B d  K *0  Precise measurements possible if enough statistics

18. 17 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS B  K *     ATLAS ATLASATLAS ATLASATLAS Interesting area for New Physics reach 1999 TDR results: 1.5 year @ low lum, ancient detector layout…. … but small modifications expected with initial layout (~15% worse) Expected mass spectra for 30 fb -1  Estimations for one year @ 2x10 33 cm –2 s -1 (20fb -1 ): 1400 B d  K *0   =50 MeV/c 2

19. 18 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS B  K *     Comparison ATLAS CMS LHCb B d  K *  S/B ~9 >0.4 ~7 Int. lumi. 20 fb -1 2 fb -1 100 fb -1 S/√B ~97 >42 ~194 High Lum. estimation only  Expected results after one year of running: …New Physics evidence only if C 7  eff >0 Precise A FB measurements possible but…

20. 19 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS B  X     Only for LHCb  Partial semi-inclusive branching ratios could give theoretically clean constraint on CKM matrix parameters ( Eur.Phys.J. C8 (1999) 619-629 ): √  R ~ Experimentally accessible to LHCb  a good accuracy could be obtained after 5 years of running Old LHCb geometry ſ B (B  X d l  l   ſ B (B  X s l  l   = V td V ts 2 1+ o (1)  R = s s

21. ATLASATLAS 1. Presentation 2. Not so rare: B  X  3. Rare: B  X     4. Very rare: B  +  - 5. Conclusions 20 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret

22. 21 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS B     Physics & experimental interest Very-rare decay (10 -9, 10 -10 ):  large New Physics effects possible Very clean signature even at high-luminosity  observable with a sufficient amount of bb pairs Current experimental limits:  Br(B s     ) < 9.5x10 -7 (CDF)  Br(B d     ) < 1.6x10 -7 (Belle)

23. 22 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS B s     LHCb  Estimations for one year @ 2x10 32 cm –2 s -1 (2fb -1 ): 17 B s   120 background events Analysis using reoptimized detector:

24. 23 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS B s     ATLAS/CMS CMS background rejection significantly better  Estimations for one year @ 10 34 cm –2 s -1 (100fb -1 ) (1999 TDR results): 92 B s  14 B d  660 background events 26 B s  4 B d   6 background events ATLASATLAS

25. 24 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS B     Comparison ATLAS CMS LHCb B s  S/B >4 >0.2 ~0.14 Int. lumi. 100 fb -1 2 fb -1 100 fb -1 S/√B ~3.6 >1.7 >10 Results after one year of running at high luminosity:  Difference between ATLAS & CMS due to: Better resolution on muon impulsion Calo isolation not yet implemented in ATLAS

26. ATLASATLAS 1. Presentation 2. Not so rare: B  X  3. Rare: B  X     4. Very rare: B  +  - 5. Conclusions 25 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret

27. 26 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS  After one year of LHC (2008):  Significant statistics in B  X  and B  X  (ATLAS/CMS & LHCb)  First precision measurements (A FB & A CP for B  X , A CP for B  X ,…) (ATLAS/CMS & LHCb)  First evidence of B  ? (ATLAS?/CMS) Conclusion What could we expect?  At LHC high luminosity era (2008  …):  &  to be continued in LHCb & ATLAS/CMS (except B  X  in ATLAS/CMS)  Precise observation of B  (CMS, ATLAS & LHCb) Thanks to S.Amato, G.Pakhlova, P.Koppenburg, N.Nikitin, L.Silvestris & S.Sivoklokov

28. Backup Material

29. B2 6 th International Conference on Hyperons, Charm and Beauty Hadrons S. Viret ATLASATLAS BK*BK* B  K *     FB asymmetry measurement will give C 7  eff sign in any case. Difference is not model dependent