1. Future B physics prospects at hadron colliders Olivier Schneider 5th KEK topical conference “Frontiers in Flavour Physics” November 20–22, 2001 KEK, Tsukuba, Japan Olivier.Schneider@iphe.unil.ch

2. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 2 B physics and CP violation in 2006 oExperimental results from —Tevatron Run IIa: CDF + D0, each 2 fb -1 —Asym. B factories: BABAR + Belle, each 300–500 fb -1 —“Equivalent” to several 10 8 B mesons oDirect measurements of angles of unitarity triangle: —  (sin(2  )) ≈ 0.03 from B 0  J/  K S asymmetry — no precise measurement of other angles oKnowledge on sides of unitarity triangle —  (|V cb |) ≈ few % error —  (|V ub |) ≈ 5-10 % error —  (|V td |/|V ts |) ≈ few-5 % error (assuming  m s < 40 ps -1 ) indirectly known to < 0.03

3. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 3 CKM triangle in 2006 (SM) oFirst stringent test of CKM ansatz ! —Sides dominated by theoretical uncertainties —More statistics would improve sin(2  ) (,)(,) … or CKM picture might already appear inconsistent …

4. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 4 Most extensions to SM imply …  … new physics in decays (  b =1) —Penguin loops  … new physics in mixing (  b=2) —Box diagrams —Tree diagrams oNote: SM tree processes are not affected new particles bd, s b new particles d,sb b b l or l or l

5. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 5 CKM triangle in 2006 (new physics)  In this case, a precise measurement of , independent of possible new physics in the mixing, is needed to provide evidence for the new physics (,)(,)  

6. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 6 Measuring new physics in B mixing Cannot be measured at current experiments Need much higher statistics, including B s decays, and PID  (b  u)/  (b  c) CP asym. in B s  D s  K  CP asym. in B s  D s  K  CP asym. in B s  J/   J/   CP asym. in B d  D    CP asym. in B d  D    CP asym. in B d  J/  K S  m d atan      SM values of  and       r new new physics parameters r new and  new   2  eff 2  eff   + 2  eff 2  eff = 2 atan  new 

7. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 7 (dis)advantages of hadron colliders for B physics Large bottom production cross section   bb  100–500  b (for √s  2–14 TeV)  Triggering is an issue   bb /  inelastic  0.2–0.6% (for √s  2–14 TeV) All b hadrons produced B u (40%), B d (40%), B s (10%), B c, and b-baryons (10%) Many primary particles to determine b production vertex  Many particles not associated to b hadrons  b hadron pairs don’t evolve coherently mixing dilutes tagging 10 12 bb / year at 2  10 32 cm  2 s  1

8. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 8 Hadron colliders (  2006) Tevatron LHC proton-antiprotonproton-proton √s2 TeV14 TeV  bb 100  b500  b  cc 1mb3.5 mb  inelastic 60 mb80 mb  total 75 mb100 mb  bunch crossing 7.6 MHz40 MHz  t bunch 132 ns25 ns  z (luminous region) 30 cm5.3 cm L [cm  s  ]2  10 32 2  10 32 10 33 (10 34 ) 1.60.53 ~2 (20) @LHCb@ATLAS/CMS Cross sections not measured yet: large uncertainties

9. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 9 B physics’ future at hadron colliders oHigh p T central detectors —CDF+D0 @ Tevatron  run II started See talk from V. Papadimitriou —ATLAS+CMS @ LHC  ready in 2006 Construction well underway Most B physics during LHC’s initial low luminosity period (10 33 ) o(forward) detectors dedicated to B physics —LHCb @ LHC  ready in 2006 Proposed and approved in 1998; TDR phase, some construction started Designed to do B physics at 2x10 32 (even when ATLAS+CMS at 10 34 ) —BTeV @ Tevatron  ? Proposed in 2000, more aggressive approach than LHCb (technology & funding) approved (stage I) at FNAL, R&D phase; waiting for funding decision …

10. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 10 ATLAS and CMS oCentral detectors (   2.5) oB physics trigger: —high p T leptons —no purely hadronic trigger (must rely on tagging lepton) oMostly B physics using J/  decay modes (+ rare decays with leptons, B s  +  - …) p T thresholds (GeV/c):

11. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 11 LHCb and BTeV oForward detectors (1.9    4.9) —still very good acceptance for bb pairs —large p B, use of RICH detectors for PID —vertex detectors inside beam vacuum oLeptonic and hadronic/vertex triggers

12. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 12 LHCb and BTeV calorimeters oTasks: —Level-0 E T trigger (e, , hadron) —Electron ID,   reconstruction oPreshower: —scintillator + 2X 0 Pb + scintillator oECAL: —Pb + scintillator tiles (“shashlik”) oHCAL: —Fe + scintillator tiles oTasks: — Electron ID —  ,  reconstruction oECAL only: —PbWO 4 crystals (developed by CMS) with PMT readout —2  11850 crystals of ~2.6  ~2.6  22 (25 X 0 ) cm 3 with pointing geometry —very good resolution

13. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 13 25 stations (50 Si planes) LHCb vertex locator oOnline:pile-up veto + vertex trigger oOffline:proper time resolution sufficient for B s physics oMany stations for full coverage, but only ~200k channels oInside vacuum tank oSufficiently rad-hard to be very close to beams —Active Si at 8 mm where ~10 14 n eq /cm 2 /y is expected oSensors on each side retractable during beam setup  Each half in Al box (250  m thick) acting as RF shield

14. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 14 LHCb vertex locator  r- and  -measuring small Si strips ( “striplets” ) ovarying pitch, occupancy < 1%  300  m, n-on-n, double metal layer  Analogue readout with STCA–VELO (DMIL) or BEETLE (0.25  m) r sensor  sensor shortest strip: 6.3 mm

15. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 15 BTeV pixel detector 31 stations (62 Si planes) oLocated in dipole field o“3-dimensional” hits oRadiation hard But... o30M channels ! oElectronics inside acceptance  larger radiation length (~2% per station) Heart of BTeV trigger, used at first level of triggering vacuum tank Two planes per station: one with “vertical” pixels one with “horizontal” pixels

16. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 16 BTeV pixel detector Si pixels FPIX0 chip o3 bit analogue readout  200  m thick bump bonded chip (FPIX2) Test beam  250  m thick 1  5 cm 2 pixel detector  25k rectangular 50  400  m pixels

17. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 17 Vertexing resolution Impact parameter resolution vs p T Decay length resolution [cm] for B      decays Excellent proper time resolution avoids significant damping of B s oscillations (5  measurement of  m s up to 48 ps  1 using one year of B s  D s    data with  t =43 fs)

18. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 18 Trigger schemes Final state reconstruction LHCb 40 kHz1 MHz40 MHz200 Hz Detached vertex + IP of p T candidate Medium p T hadron, ,e,  + pileup veto Decay topology BTeV 80 kHz7.6 MHz3 kHz Detached vertex + dimuon Event selection ATLAS CMS 40 MHz High p T , e p T and E T triggers (muon + calorimeters) vertex triggers (Si vertex detector) confirmation and event filters 75 kHz100 Hz

19. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 19 Low-level triggers Si pixels: 3  10 7 channels hardware+processors, asynchronous variable latency ~150  s reduction factor ~100 calo+  +pileup veto: 5  10 4 channels hardware, synchronous fixed latency =4  s reduction factor ~40 (only ~10 from p T cut) Si strips: 2  10 5 channels processors, asynchronous fixed latency =1.7 ms reduction factor ~25 1 MHz 40 MHz Detached vertex + IP of p T candidate * Medium p T hadron, ,e,  + pileup veto (12.4 MHz of inel. interactions) LHCb 40 kHz 7.6 MHz Detached vertex + dimuon BTeV 80 kHz * added since TP (LHCb event yields not updated yet for new L1 efficiencies) L0 L1

20. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 20 LHCb RICH1 Ring Imaging Cherenkov detectors oBTeV: 2 radiators in 1 RICH to cover 3 < p < 70 GeV/c oLHCb: 3 radiators in 2 RICHes to cover 1 < p < 100 GeV/c LHCb pixel HPD (baseline option) 87 mm diam. phototube with pixel detector bump-bonded to encapsulated binary electronics 1024 Si pixels (500  m x 500  m) Prototype chip available

21. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 21 Particle identification ATLAS LHCb K–  separation for true   Very important for many exclusive channels Example: B 0      LHCb

22. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 22 Flavour tagging at production oNeeded for many CP violation measurements oMethods used/studied so far: oLHCb and BTeV expected to reach similar tagging power: —LHCb TP:  D 2 =6.4% based on study of lepton and kaon tags alone —BTeV TP:  D 2 =10% assumed Still to be studied

23. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 23  from B 0  J/  K S oHuge statistics (especially ATLAS & CMS) oCan also fit for A dir (expected ≈ 0 in SM)  LHCb & BTeV: compare with Penguin decay B 0   K S ATLAS e  e  (3 years) CMS     (1 year) LHCb

24. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 24 B s mixing phase from B s  J/  , J/   oStrange counterpart of B 0  J/  K S  SM prediction of B s mixing phase is small  s = 2  = 2 2  = O(10  2 ) oSensitive probe for new physics  J/   is not pure CP final state —can reach  (  s ) ≈ 0.02 in 1 year, under assumptions on the strong phases —need angular analysis for clean extraction  J/    is pure CP=  1 —need photon detection —BTeV:  (  s ) = 0.033 in 1 year  NP-LR:left-right symmetric model with spontaneous CP viol. NP-DQ:iso-singlet down quark mixing model

25. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 25 B 0      asymmetry, etc... oA dir and A mix can be measured —e.g. ±0.08 with 1 year at LHCb but Penguin “pollution” hampers  extraction  Study of B 0  (    ,    ,     )        (time-dependent analysis of Dalitz plot) to extract , Penguin and tree terms —BTeV/LHCb claim 10.8/>3.3k untagged per year —more study needed to quote  –   Measure A dir and A mix for B s  K  K  —e.g. ±0.11 with 1 year at LHCb (if  m s =20 ps  1 ) and combine with B 0      results to extract  assuming U-spin symmetry —LHC claim  ~ 5  after 1 year proposed by Snyder&Quinn proposed by Fleischer    M 2 (     ) [GeV 2 ] M 2 (     ) [GeV 2 ]

26. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 26  from B 0  D*   , D*    oSmall interference between two tree decays, with and without prior B 0 mixing  Extract  and  strong simultaneously from the two time-dependent asymmetries  Use  from J/  K S to obtain value of  insensitive to possible new physics in mixing oLHCb study: —use both exclusive and inclusive reconstruction of neutral D from D* + strong phase difference  1 year  (degrees) error on  (degrees) 10% error on  no error on  5 years assumed amplitude ratio  = 0.02  strong   = O(10  ) depends on  and  strong (1 year)  Need 4high stats

27. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 27  from B s  D s  K , D s  K    Strange counterpart of B 0  D*   , D*     Here measure  and take  from J/   oImportant differences: —Asymmetry larger because two tree amplitudes of similar order (  3 ) —Proper time resolution more important —Background from Cabibbo-allowed D s    * using common BR assumptions (as in LHCb TP) Sensitivity on  depends on: amplitude ratio strong phase difference   m s For  m s = 20 ps  1 : (1 year, each expt)  Need very good 4hadronic trigger efficiency  K/  separation 4proper time resolution  = O(10  )

28. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 28  B      X s,d involve loop & box with V td,V ts  Ratio of inclusive rates with “non-resonant” dimuon mass allows extraction of  V td  V ts  with small theoretical error of O(1%)  After several years, this method may become competitive with  m d /  m s New preliminary LHCb study  Relative error on  V td  V ts  of ~11%  V td  V ts  from B      X s,d

29. O. Schneider, Nov 20, 2001 Future B physics prospects at hadron colliders 29 Summary oB physics at hadron colliders, currently performed at Tevatron, will get a big boost once LHC turns on (2006)  huge statistics: 10 12 bb / year at 2  10 32 cm  2 s  1 including B s mesons oDedicated detectors (LHCb, BTeV) aim for best …trigger efficiency (hadron and vertex triggers) …proper time resolution …particle identification  Clean extraction of angle  after one year  several independent measurements with O(10  ) precision oConfront with other measurements involving loops/boxes if new physics shows up, measure its parameters