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Rare B decays (at the LHC) as a probe of b → s transitions

Rare B decays (at the LHC) as a probe of b → s transitions. Framework LHC & experiments b → s g b → s l + l - B (s) → m + m - LHC Schedule Summary. Gerhard Raven NIKHEF & Vrije Universiteit, Amsterdam. ITEP Meeting on The Future of Heavy Flavour Physics. Disclaimers.

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Rare B decays (at the LHC) as a probe of b → s transitions

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  1. Rare B decays (at the LHC) as a probe of b → s transitions • Framework • LHC & experiments • b → s g • b → s l +l - • B(s) →m+m- • LHC Schedule • Summary Gerhard Raven NIKHEF & Vrije Universiteit, Amsterdam ITEP Meeting on The Future of Heavy Flavour Physics Future of Heavy Flavour Physics

  2. Disclaimers • This talk heavily borrows from: • Patrick Koppenburg: Beach, Physics at LHC • Pavel Reznicek: Beach • Olivier Schneider: Flavour at the LHC • Thomas Speer: Beach, Capri workshop • Nikolay Nikitine: Capri workshop • And others… • Little new news, a lot of the attention right now is on installation, commisioning, calibrations, alignment, preparations for data-taking… Future of Heavy Flavour Physics

  3. b→s transitions & OPE… Describe b→s transitions by an effective Hamiltonian • Long Distance: • Operators Oi • Short Distance: • Wilson coef. Ci New physics shows up as modified Ci, (or as new operators) From G. Hiller [hep-ph/0308180] Future of Heavy Flavour Physics

  4. Operators & Observables From G. Hiller [hep-ph/0308180] Future of Heavy Flavour Physics

  5. e+e- @Y(4S) vs. pp @ LHC… For Rare Decay analysis, having access to large samples produced is an obvious starting requirement… Next step is collecting the data… Future of Heavy Flavour Physics

  6. The LHC Experiments ATLAS CMS (that have a B physics program) • LHCb: dedicated B physics experiment • ATLAS/CMS: general purpose experiments, optimized for high-pT discovery physics at 1034 cm–2s–1 LHCb Future of Heavy Flavour Physics

  7. Detector Acceptance 100 mb 230 mb • ATLAS/CMS: • central detectors, ||<2.5 • will do B physics using high-pT muon triggers, mostly with modes involving dimuons • purely hadronic modes triggered by tagging muon • LHCb: • designed to maximize B acceptance (within cost and space constraints) • forward spectrometer, 1.9 <  < 4.9 • more b hadrons produced at low angles • single arm OK since bb pairs produced correlated in space • rely on much softer, lower pT triggers, efficient also for purely hadronic B decays Future of Heavy Flavour Physics

  8. Luminosity & Pile-up pp interactions/crossing n=0 LHCb ATLAS/CMS n=1 • Pileup: • number of inelastic pp interactions in a bunch crossing is Poisson-distributed with mean n = Linel/f • ATLAS/CMS (f = 32 MHz) • Will run at highest luminosity available • Expect L <2  1033 cm–2s–1(n < 5) for first 3 years • At L = 1034 cm–2s–1 (n = 25), expect only Bs still possible • LHCb (f = 30 MHz) • L tuneable by defocusing the beams • Choose to run at <L> ~ 21032 cm–2s–1(max. 51032 cm–2s–1) • Clean environment (n = 0.5) • Less radiation damage • LHCb 8mm from beam, ATLAS 5 cm, CMS 4 cm • Will be available from 1st physics run L = instantaneous Luminosity inel= 80 mb f=non-empty crossing rate 10 fb–1 / year 30 fb–1 total at low L 2 fb–1 / year 1012 bb events 10 fb–1 in first 5 years (nominal year = 107 s) Future of Heavy Flavour Physics

  9. Atlas (di)muon Trigger • LVL1: • Pt(1)>6 GeV/c, Pt(2) > 4 GeV/c • L<1033: single mu • L~1033: dimuon • LVL2 • Confirm LVL1, refine pt • LVL2&EF • vertex constraints + mass Future of Heavy Flavour Physics

  10. CMS Trigger • Triggers for B-physics • Level1: • Single muon, pt>14GeV/c • Dimuon, pt>3 GeV/c • HLT: • Inclusive b,c trigger • L1: high ET jet,  5 Hz • Exclusive B decays • Partial reconstruction of detector in the region around the muons O(1Hz) per decay 40 MHz ~100 kHz ~100 Hz (total!) From T. Speer [Capri workshop on Theory, Phenomenology and Experiment in Heavy Flavour Physics] Future of Heavy Flavour Physics

  11. LHCb Trigger 10 MHz (visible bunch crossings) Hardware trigger • Fully synchronized (40 MHz), 4 s fixed latency • “High pT”, , e,  and hadron + pileup info (e.g. pT() > 1.3 GeV/c) custom electronics boards L0 1 MHz (full detector readout) Software trigger • Full detector info available, only limit is CPU time • 1st stage: ~1 ms  40 kHz (could change) • Tracks with min. impact param. and pT • (di)muon • High-Level trigger: ~ 10 ms • Full event reconstr.: excl. and incl. streams farm of~ 2000 CPUs Main changes since original design: 2003: track pT at 1 MHz 2005: increased output rate 2005: full readout at 1 MHz ≤ 2 kHz (storage) Future of Heavy Flavour Physics

  12. Trigger Summary Atlas CMS LHCb Future of Heavy Flavour Physics

  13. Expected Performance ATLAS CMS LHCb Bs  80 46 18 BsDs  46 ? 14 Bs J/  38 32 16 Bs J/  17 13 8 Mass resolutions in MeV/c2 without J/ mass constraint with J/ mass constraint Good mass resolution important for background rejection ! BsDs proper time resolution Proper time resolution: • CDF: t~ 100 fs • ATLAS: t~ 100 fs (was 70 fs) • CMS: t~ 100 fs • LHCb: t~ 40 fs st ~ 40 fs Good proper time resolution essential for time-dependent Bs measurements ! Future of Heavy Flavour Physics

  14. Back to the physics… Future of Heavy Flavour Physics

  15. b → s g From G. Hiller [hep-ph/0308180] Future of Heavy Flavour Physics

  16. b → s g • Amplitude  Vts|C7| • First evidence for penguins (’93) • WA: Br = (3.55 ±0.26) 10-4 • SM: Br = (3.7 ± 0.3) 10-4 • Sets strong constraints on charged Higgs, New Physics… Future of Heavy Flavour Physics

  17. LHCb:B → K*g, Bs →fg Charged Tracks: Consistent with req. PID Inconsistent with primary vertex Good secondary vertex Consistent K*, f mass Photons: Et > 2.8 GeV Remove B→K*p0, Bs→fp0 using K*, f polarisation From I. Belyaev, G. Pakhlova [LHCb-2003-090] Future of Heavy Flavour Physics

  18. LHCb:B → K*g, Bs →fg • Require B to point back to the Primary Vertex • Mass resolution: 65 MeV • Lifetime resolution: 62 fs Future of Heavy Flavour Physics

  19. b → s g : photon polarization • How to measure? • Virtual photons (eg. b → s l +l -) • Melinkov et al., [PLB442 381-389, 1998] • Converted photons • Grossman et al., [JHEP06 29, 2000] • B→gK** (Kpp) • Gronau & Pirjol, [PRD66 054008, 2002], Gronau et al., [PRL88 051802, 2002] • Time Dependent ACP(K*g) • Lb baryons • Hiller & Kagan , [PRD65 074038, 2002] • Photon Polarization is not well known • (New) Right-handed operators could increase this! • But gluons could also contribute O(10%) • Grinstein et al., [PRD71:011504, 2005] Future of Heavy Flavour Physics

  20. LB→Lg polarisation Expect Lb to be polarized • Can be measured with Lb L J/y at 1% level • Assume 20% for now… [E. Leader] [Hrivnac et al, hep-ph/9405231] But • Lg does not have a distinctive secondary vertex • Most L decay after escaping the vertex detector [Hiller, Kagan,PRD 65, 074038 (2002)] From F.Legger, T.Schietinger [hep-ph/0605245] Future of Heavy Flavour Physics

  21. LB→Lg Annual yields (2fb-1) @ LHCb: Approx 20% resolution on r = C7’/C7 after one year • Far from SM, but already interesting for some NP models Future of Heavy Flavour Physics

  22. b → s l +l - From G. Hiller [hep-ph/0308180] Future of Heavy Flavour Physics

  23. Radiative decays & b → s l +l - Supressed by aEM • Br(b → sl +l -) = (4.5±1.0) 10-6 • Br(B+→ K+l +l -)= (0.5 ± 0.1) 10-6 Currently rarest observed B decay Future of Heavy Flavour Physics

  24. b → s l +l - Sensitive to • Susy • Graviton exchange • … Supressed by aEM • Br(b → s l +l -) = (4.5±1.0) 10-6 • Br(B+→ K+l +l -)= (0.5 ± 0.1) 10-6 Currently rarest observed B decay Future of Heavy Flavour Physics

  25. b → s l +l -: inclusive vs. exclusive Inclusive decays well described by theory • Shape of dilepton mass distribution sensitive to NP • SM branching ratio (1.36±0.08) 10-6 (NNLL) for s = q2/mb2 < 0.25 … but hard to analyze experimentally (impossible at hadron colliders?) Exclusive decays much easier for experiment … but what about hadronic uncertainties? From Goto et al. [PRD55 4273 (1997)] Future of Heavy Flavour Physics

  26. b → s l +l -: exclusive Use ratios to cancel hadronic uncertainties • Forward-Backward asymmetry (AFB) • Zero of AFB: s0 = 2C7/C9(s0) • CP asymmetry • CP asymmetry in AFB • Ratio of e+e- to m+m- From Goto et al. [PRD55 4273 (1997)] Future of Heavy Flavour Physics

  27. Reminder: current B-factory results Belle [PRL93 061803 (2004) ] Belle [hep-ex/060318] b → s l +l - : C9 and C10 BaBar [hep-ex/0507001] b → sg : C7g C10/C7 Again: any deviation likely to be small… Likely need high precision measurement to recognize deviations from SM… C9/C7 Future of Heavy Flavour Physics

  28. Exclusive B0→m+m-K*0 • Expected signal and background for 2 fb-1 (one nominal year) • Assuming Br = 12 . 10-7 New: updated analysis expects 7.7K/year, at similar background levels… Future of Heavy Flavour Physics

  29. AFB(B0→m+m-K*0) 13% error on C7/C9 10 fb-1: s0 = 4.0 ± 0.5 GeV2 • Toy MC, based on full simulation results • Generate several experiments 2 fb-1: s0 = 4.0 ± 1.2 GeV2 Future of Heavy Flavour Physics

  30. Atlas: AFB(B0→m+m-K*0) From N. Nikitine [Capri workshop on Theory, Phenomenology and Experiment in Heavy Flavour Physics] Future of Heavy Flavour Physics

  31. Atlas: Lb→m+m-L • Very similar to B0→m+m-K* • Select L with • t > 0.5 ps • 1 < RL < 45 cm • M(Lb): 75 MeV resolution • After 3 years: ~1500 events From P. Reznicek [Flavour at the LHC] Future of Heavy Flavour Physics

  32. RK in B+→ l +l -K+ • Can get O(10%) corrections due to Higgs • boson exchanges… • RX is related to Br(Bs→mm) Hiller & Krueger [PRD69 (2004) 074020] Future of Heavy Flavour Physics

  33. RK in B+→ l +l -K+ Current Status: Currently Allowed… Future of Heavy Flavour Physics

  34. RK at LHCb… • 2 fb-1: signal yield from fit: • Addition of dedicated inclusive di-electron trigger should gain O(40%) in eeK (not included here) • Note: llK* background not yet considered… • Could complicate eeK, so maybe just do RK* instead ;-) • 10% error on RK • [ Patrick Koppenburg Beach, Physics at LHC ] Future of Heavy Flavour Physics

  35. RK & Br(Bsm+m-) with 10 fb-1 Broken lepton universality… Minimal Flavour Violation SM, or MSSM with small tanb • [ Patrick Koppenburg Beach, Physics at LHC ] Future of Heavy Flavour Physics

  36. Bd,s →m+m- From G. Hiller [hep-ph/0308180] Future of Heavy Flavour Physics

  37. Bs +– • CDF+D0 could exclude upto few times 10-8 with 10 fb-1 Bs +– • Very rare decay, sensitive to new physics: • BR ~ 3.5  10–9 in SM, can be strongly enhanced in SUSY: Br  tan6b/MH2 • Current limit from Tevatron (CDF+D0): 1.5  10–7 at 95% CL Tevatron: BR <1.5 10-7 Future of Heavy Flavour Physics

  38. Bs +– Mass Resolution (MeV/c2) ATLAS CMS LHCb Bs  80 46 18 Bs +– • Very rare decay, sensitive to new physics: • BR ~ 3.5  10–9 in SM, can be strongly enhanced in SUSY: Br  tan6b/MH2 • Current limit from Tevatron (CDF+D0): 1.5  10–7 at 95% CL • Expect CMS and Atlas to do very well • Higher luminosity, sufficiently easy to trigger on  more signal • But LHCb has also some advantages • Better invariant mass resolution, better propertime resolution  easier background rejection! Tevatron: BR <1.5 10-7 Future of Heavy Flavour Physics

  39. Bs,d→m+m-: p & K misidentification • Two body modes: • Eg. Br(B0Kp) = 2 10-5 Misid rate: need better than O(1%) • Fake rate: 2 10-5 (1%)2=2 10-9 LHCb: • 1 event/fb-1 in a 2 s mass window Does not seem to be a major problem… (but: eg. Atlas has a ~4x worse mass resolution than LHCb) Future of Heavy Flavour Physics

  40. Bs,d→m+m-: LHCb selection yields 2 fb–1 Bs + – signal (SM) 17 b+, b- background < 100 Inclusive bb background < 7500 All backgrounds ??? • Tracks with • Pt > 1 GeV • IP/s > 3 • B candidate • Vertex c2 < 9 • (momentum, decay direction) < 5 mrad Future of Heavy Flavour Physics

  41. Bs +– • LHC should have prospect for significant measurement, but difficult to get reliable estimate of expected background: • LHCb: Full simulation: 10M inclusive bb events + 10M b, b events (all rejected for M(+–)>4 GeV/c2) • ATLAS: 80k bb +– events with generator cuts, efficiency assuming cut factorization • CMS: 10k b, b events with generator cuts, trigger simulated at generator level, efficiency assuming cut factorization Future of Heavy Flavour Physics

  42. (current) LHC Startup Schedule • End of Summer 2007 • Closure of beam vacuum in August • Closure of interaction regions • “November-December” 2007 • Pilot run at injection energy (450 GeV) • Jan—April 2008 • Shutdown • Summer 2008 • Run at Full Energy… Future of Heavy Flavour Physics

  43. LHCb Installation Status March 2005 May 2006 Muon system RICH2 Magnet RICH1 Calorimeter HCAL, ECAL Trigger Tracker Vertex Locator Tracking Stations Future of Heavy Flavour Physics

  44. Summary & Conclusions • The hadronic flavour sector will surely contribute significantly to the overall LHC effort to find and study physics beyond the SM: • New physics will be chased at LHC in b→s transitions • A few superb (highly-sensitive) bs observables are accessible:Bs mixing magnitude and phase, exclusive bs, B(s) • Large phase space can already be covered with the first good year of data • LHCb will improve precision on CKM angles • Several  measurements from tree decays only: stat() ~2.5 in 5 years • May reveal inconsistencies with other/indirect measurements after several years • Looking forward to end of LHC machineinstallation and first collisions in 2007 • LHCb aiming for complete detector at end of 2006, ready to exploit nominal luminosity from day 1 Future of Heavy Flavour Physics

  45. BACKUP Future of Heavy Flavour Physics

  46. Bs→m+m-: Atlas & CMS… From N. Nikitine [Capri workshop on Theory, Phenomenology and Experiment in Heavy Flavour Physics] 4s observation with 30fb-1 (3 year low-lumi) From T. Speer [Capri workshop on Theory, Phenomenology and Experiment in Heavy Flavour Physics] Future of Heavy Flavour Physics

  47. Trigger output rates and physics Output rate Event type Physics • Output rates: • Rough guess at present (split between streams still to be determined) • Large inclusive streams to be used to control calibration and systematics (trigger, tracking, PID, tagging) • Charm physics possibilities (to be explored): • Could trigger on 500M signal D*D0(h+h–) per year, 50M D0 K+K– • D0 mixing (x and yCP) and CP violation in D0 K+K– • could reach SM levels or close • systematics ? 200 Hz Exclusive B candidates B (core program) 600 Hz High mass di-muons J/, bJ/X (unbiased) 300 Hz D* candidates Charm 900 Hz Inclusive b (e.g. bm) B (data mining) Future of Heavy Flavour Physics

  48. Particle ID: K/p separation • Fully simulated pattern recognition in two LHCb RICHes: • Reconstruct rings around reconstructed tracks • Good K- separation achievable in 2–100 GeV/c range Kaon ID: ~88% Pion mis-ID: 3% Future of Heavy Flavour Physics

  49. Flavour tagging l- K– Qvtx D B0 Bs SV PV K+ • LHCb: • Most powerful tag is opposite kaon (from bcs) • Combined D2 ~ 7% (Bs) or ~ 4% (B0) • Recent neural network approach leads to ~9% for Bs • Compare with: • CDF achieved 4% (SS) +1.5% (OS) • B factories achieved ~ 30% (Coherent Production!) Future of Heavy Flavour Physics

  50. Future of Heavy Flavour Physics

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