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Flavor Physics and CP Violation at LHC

Flavor Physics and CP Violation at LHC. LHC tunnel. LHC dipole. Vancouver, 9-12 April 2006. Cryogenic services line. Andreas Schopper (CERN). Motivation Experimental sensitivity Expected physics performance Conclusion. Motivation. CKM fitter without CDF.

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Flavor Physics and CP Violation at LHC

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  1. Flavor Physics and CP Violation at LHC LHC tunnel LHC dipole Vancouver, 9-12 April 2006 Cryogenic servicesline Andreas Schopper (CERN) Motivation Experimental sensitivity Expected physics performance Conclusion

  2. Motivation CKM fitter without CDF B-factories (BABAR&BELLE) are extremely successful in constraining the unitary triangle within the SM and Tevatron (D0&CDF) has demonstrated its Bs physics capability! LHC will act as a b-factory with large b-quark production rate including Bs, allowing to improve the CKM consistency test and to look for deviations from the SM rare processes UT fit with CDF New Physics models introduce new particles, dynamics and/or symmetries at a higher energy scale (expected in the TeV region) with virtual particles that appear e.g. in loop processes B Physics measurements are complementary to direct searches and will allow to understand the nature and flavour structure of possible New Physics Flavor Physics and CP Violation

  3. Precise measurement of B0s-B0s mixing: Dms, DGs and phase fs. Search for effects of NP appearing in suppressed and rare exclusive and inclusive B decays B(s)0Xg, B0K*0l+l-, bsl+l-, Bsm+m-... Completing the program on B Physics… BsDsp, … BsJ/yf, BsJ/yh(’) Precise g determinations including processes only at tree-level, in order to disentangle possible NP contributions Other measurements of CP phases in different channels to over-constrain the Unitarity Triangles BsDsK, B0D0K*0, B±DK±, B0pp & BsKK, … B0fKs, Bsff, ... B0rp, B0rr, … Flavor Physics and CP Violation

  4. B-factories vs.b-factory Flavor Physics and CP Violation

  5. Experimental sensitivity How to reach high sensitivities: • B production rate and detector acceptance • trigger (incl. fully hadronic decays) • background reduction • Good mass resolution • Particle Identification • Good decay time resolution for Bs • flavour tagging Flavor Physics and CP Violation

  6. Pythia production cross section 100 mb 230 mb • LHCb: dedicated to B-physics • designed to maximize B acceptance • Forward, single arm spectrometer, 1.9 <  < 4.9 • more b hadrons produced at low angles • bb pairs produced correlated in space • “lower” pT triggers, including purely hadronic modes ATLAS LHC Experiments (that will do B-physics) • ATLAS and CMS: general purpose experiments • central detectors, ||<2.5 • B physics using high-pT muon triggers, mostly with modes involving dimuon Flavor Physics and CP Violation

  7. 100K cool-down Status of detectors ECAL HCAL magnet Nov. 05 Feb. 06 Expect first collisions in summer 2007! SCT Feb. 06 Oct. 05 Flavor Physics and CP Violation

  8. pp interactions/crossing n=0 LHCb ATLAS/CMS n=1 Luminosity and pileup • Pileup • number of inelastic pp interactions in a bunch crossing is Poisson-distributed with mean n = Lsinel/f • ATLAS/CMS(f = 32 MHz) • want to 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 B still possible • LHCb(f = 30 MHz) • L tuneable by adjusting the beam focus • 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 (nominal year = 107 s) 10 fb–1 / year at low L 30 fb–1 total at low L 2 fb–1 / year 10 fb–1 in first 5 years Flavor Physics and CP Violation

  9. ATLAS trigger Full ATLAS trigger: • LVL1: hardware, coarse detector granularity, 2 s latency • LVL2: full granularity, LVL1 confirmation + partial rec., 10 ms processing • EF (event filter): full event access, “offline” algorithms 1 s processing Strategy for B physics trigger: • High luminosity (> 21033 cm–2s–1): • LVL1: dimuon, pT > 6 GeV/c each • Low luminosity (or end of) fills: • LVL1: add single muon, pT > 6–8 GeV/c • LVL2: look for objects around muon • 2nd muon (with lower threshold) in muon RoI • Single e/ or e+e– pair in EM RoI • Hadronic b decay products in Jet RoI (e.g. Bs Ds-p+ ) Flavor Physics and CP Violation

  10. CMS trigger Trigger to cover widest range of discovery physics (Higgs, SUSY, …) • Level 1: (nominal) 3.2s buffer,  100 kHz • HLT (High-Level Trigger): 1s buffer, 40 ms processing,  100 Hz Trigger on B events: • Level 1: di- with pT> 3 GeV/c each (or single  with pT> 14 GeV/c) • HLT: Limited time budget  restrict B reconstruction to RoI around  or use reduced number of hits/track (Ds) Flavor Physics and CP Violation

  11. 10 MHz (visible bunch crossings) 1 MHz (full detector readout) ≤ 2 kHz (storage) LHCb trigger Custom electronics boards Hardware trigger • Fully synchronized (40 MHz), 4 s fixed latency • “High pT”, , e,  and hadron + pileup info (e.g. pT() > 1.3 GeV/c) PC farm of ~2000 CPUs 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 reconstruction: excl. and incl. streams • exact splitting between streams can be optimized according to physics requirements • large inclusive streams to be used to control calibration and systematics (trigger, tracking, PID, tagging) Flavor Physics and CP Violation

  12. BsDs proper time resolution st ~ 40 fs Tracking performance • Proper time resolution ATLAS: t~ 95 fs CMS: t~ 100 fs LHCb: t~ 40 fs • Mass resolutions in MeV/c2 without J/ mass constraint with J/ mass constraint LHCb Good proper time resolution essential for time-dependent Bs measurements ! Flavor Physics and CP Violation

  13. No RICH Kaon ID: ~88% Pion mis-ID: 3% π π hypothesis Particle ID performance of LHCb Requirements: • Background suppression => high momentum hadrons in two-body B decays • B flavor tagging (identify K from b→c→s) => low momentum hadrons Fully simulated pattern recognition in two LHCb RICHes: • Good K- separation achievable in 2–100 GeV/c range • Reconstruct rings around tracks found in tracking Flavor Physics and CP Violation

  14. l- K– Qvtx D B0 Bs SV PV K+ Flavour tagging • LHCb: • Most powerful tag is opposite kaon (from bcs) • Combined D2 ~ 6% (Bs) or ~ 4% (B0) • Recent neural network approach leads to ~9% for Bs • Compare with: • Tevatron: D0 ~2.5% , CDF ~1.5% OS and ~4% SS • B factories achieved ~ 30% Flavor Physics and CP Violation

  15. Expected Physics Performance B-mixing: • “control channel” B0J/ KS • Dms with Bs0  Dsp • fs and Gs with Bs J/f(h) Suppressed and rare decays: • Exclusive b  s +- • Bs0  +- Measurement of g: • from Bs DsK • from B DK* • from B±  DK± • from B and BsKK Flavor Physics and CP Violation

  16. “gold-plated” decay channel at B-factories for measuring the Bd- Bd mixing phase needed for extracting γfrom B  ππand Bs  K K, or from B  D*π in SM ~0, non-vanishing value O(0.01) could be a signal of Physics Beyond SM sin(2) from B0J/ KS ACP(t) (background subtracted) One of the first CP measurements at LHC: • demonstrate CP analysis performance • study tagging systematics Expected sensitivity: • LHCb: 240k signal events/year  stat(sin(2)) ~ 0.02 (1year, 2fb-1) (s(b)~0.6°) • ATLAS: similar sensitivity for (first 3years, 30fb-1) Search for direct CP violating term… LHCb Flavor Physics and CP Violation

  17. S/B ~ 3 (derived from 107 fully simulated inclusive bb ev.) LHCb: • 5 observation forms<68ps–1 in (1year,2fb–1), for ms<40ps–1 in (~1month,0.25fb–1) ATLAS/CMS: 5s observation for Dms< 22 ps-1 in (3years, 30fb-1) Bs oscillations • Measurement of ms is one of the first LHCb physics goals • Expect 80k Bs Ds-p+ events per (1year, 2fb–1), average t ~ 40 fs LHCb Distribution of unmixed sample after 1 year (2 fb–1) assuming ms = 20 ps-1 LHCb Flavor Physics and CP Violation

  18. SU(3) analogue of B→J/yKs, measuring theBs- Bs mixing phase in SM fs = –arg(Vts2) = –22 ~ –0.04increasedsensitivity to New Physics large CP asymmetry would signal Physics Beyond SM also needed for extractinggfromBs  Ds K or from B ππandBs  K K fs and DGs from BsJ/ (η,η’…) J/ is not a pure CP eigenstate: • 2 CP even, 1 CP odd amplitudes contributing • need to fit angular distributions of decay final states as function of proper time (needs external ms) • requires very good proper time resolution Expected sensitivity:(at ms = 20 ps–1) • LHCb: 125k BsJ/ signal events/year  stat(sin s)~0.031, stat(s/s)~ 0.011 /(1year, 2fb–1)  stat(sin s)~0.013 after first 5 years, adding pure CP modes like J/η, J/η’ (small improvement) • ATLAS: similar event rate as LHCb but less sensitive  stat(sin s)~0.08 (1year, 10fb–1) • CMS: > 50k events/year, sensitivity study ongoing στ= 38 fs LHCb Flavor Physics and CP Violation

  19. AFB(s) for B0K*0 s = (m)2 [GeV2] ^ AFB(s) for b+– ATLAS expectation for (3yrs, 30 fb–1) SM MSSM C7eff>0 ^ s = (m/mb)2 Exclusive b  s +- • Suppressed decays (DB=1 FCNC), SM BR ~ 10–6 • Forward-backward asymmetry AFB(s) in the  rest-frame is a sensitive probe of New Physics [A.Ali et al., Phys. Lett. B273,505 (1991)] • Zero point can be predicted at LO with no hadronic uncertainties, known at 5% level in SM, sensitive to NP via non-standard values of Wilson coefficients Expected sensitivity: • LHCb: 4400 B0K*0m+m- events/(yr,2fb–1), S/B>0.4  determine C7eff/C9eff with 13% error (SM) • ATLAS: 1000 B0 K*0m+m- events/(yr,10fb–1), S/B>1 • Other exclusive b  s feasible (Bs, b) Flavor Physics and CP Violation

  20. Bs +– • Very rare decay, sensitive to new physics • BR ~ 3.5  10–9 in SM, can be strongly enhanced in SUSY • Current limit from Tevatron: • D0: 2.310–7 at 95% CL • CDF: 1.010–7 at 95% CL LHC has prospect for significant measurement but difficult to get reliable estimate of expected background: • LHCb: Full simulation: 10M incl. bb events + 10M b, b events (all rejected) • 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 • New assessment of ATLAS/CMS reach at 1034 cm–2s–1 in progress Flavor Physics and CP Violation

  21. 2 time dependent asymmetries from 4 decay rates: Bs (Bs)  D-sK+, D+sK- 2 tree decays (b→c and b→u) of same magnitude (~λ3) interfere via Bs mixing  insensitive to new physics  large interference effects expected CP asymmetry measures (g+ fs), with fs being determined using Bs → J/y f needs suppression of Bs Dsπ background (BR~12 higher) BsDsK BsDs g from Bs DsK Important for selection: • hadron trigger • mass resolution • proper-time resolution • K/p separation Expected LHCb signal rates and background: • 5400 signal events in (1year, 2fb-1) • residual contamination from Bs Dsπ ~ 10% • S/Bbb > 1 at 90% CL (from one MC bb event) Flavor Physics and CP Violation

  22. DsK asymmetries (5 years, ms=20 ps–1) Ds–K+ Ds+K– g from Bs DsK Fit the 4 tagged, time-dependent rates: • phase of D-sK+= D + (g + fs) • phase of D+sK-= D- (g + fs)  extract both D and (g + fs) Expected LHCb sensitivity: (at Dms = 20ps-1 , -20°<D<20°) • s(g) ~ 14° in (1year, 2fb-1) (expected to be statistically limited) • Discrete ambiguities in g can be resolved • if DGs large enough, or • using B0→Dp and U-spin symmetry Flavor Physics and CP Violation

  23. A1 = A(B0 D0K*0): bc transition, phase 0 A2 = A(B0 D0K*0): bu transition, phase + A3 = 2 A(B0 DCPK*0) = A1+A2, because DCP=(D0+D0)/2 g from B0 D0K*0 • Dunietz variant of Gronau-Wyler method [Phys. Lett. B270, 75 (1991)] • Two colour-suppressed diagrams with |A2|/|A1| ~ 0.4 interfering via D0 mixing • 6 decay rates, self-tagged and time-integrated Expected signal rates and background: (1year, 2fb-1), g=65°, D=0 Expected LHCb sensitivity: • s(g) ~ 8° in (1year, 2fb-1) for 55°<g<105°, -20°<D<20° Flavor Physics and CP Violation

  24. colour-allowed colour-suppressed u s u d }K- }p+ c u c u s u d u D0{ D0{ }K- }p+ Cabibbo-favoured Double Cabibbo-suppressed  from B±  DK± • based on Atwood-Dunietz-Soni method [Phys. Rev. Lett. 78, 3257 (1997)] • measure relative rates of B-→ D(Kp) K- and B+→ D(Kp) K+ • Two interfering tree B-diagrams, one colour-suppressed (rB ~0.15) • Two interfering tree D-diagrams, one Double Cabibbo-suppressed (rDKp ~0.06) Weak phase diff.:  Magnitude ratio: rB Strong phase diff.: dB Magnitude ratio: rDKp Strong phase diff.: dDKp Measure relative B-decay rates: 3 observables, 5 parameters (g, dB, dDKp, rB, rDKp) , but rDKp ~0.06known add more D-decays to constrain further… Flavor Physics and CP Violation

  25.  from B±  DK± Add further D-decays: • D → Kppp (Cabibbo favoured + DCS decay) • 4 new rates with 2 new parameters, one known: dDK3p ; rDK3p ~0.06 • D → KK (CP eigenstate) • 2 new rates, no new unknown: rDKK = 1 ; dDKK = 0  7 relative rates and 5 unknowns: g, rB, dB, dDK, dDK3 • Candidate for LHCb’s statistically most precise determination of g • Estimated sensitivity: s(g) ~ 5° in (1year, 2fb-1)  Studies ongoing… Further B-channel considered… • B±  D*K± with • D*→ D0p0  D* and D0have same CP • D*→ D0g D* and D0 have opposite CP Flavor Physics and CP Violation

  26. B   (95% CL) p/K p/K Bd/s d Bd/s p/K p/K Bs KK(95% CL) g()  from B and BsKK • large penguin contributions in both decays  sensitive to New Physics • measure time-dependent CP asymmetry for B and BsKK • ACP(t) = Adir cos(Dmt) + Amix sin(Dmt) • Adir andAmix depend on g, mixing phases, and ratio of penguin to tree = d eiq • exploit “U-spin” symmetry (ds) [R.Fleischer, Phys.Lett. B459, 306 (1999)] • dpp = dKK and qpp = qKK • 4 measurements and 3 unknowns, if mixing phases from B0J/KS and BsJ/ Important for selection: • hadron trigger • K/p separation • mass resolution • proper-time resolution Expected sensitivity: 26k B , 37k BsKK, 135kBK s(g) ~ 5° in (1year, 2fb-1) Flavor Physics and CP Violation

  27. After 5 years:SM expectation • s(Bs→ ccss) ~ Br(Bs→ ) ~0.7 ~DsK, DK) ~1 ~60 (tree only)) ~2 ~60 (tree + penguin) Conclusion • Experiments at LHCwill pursue an extensive program on B-physics • with high statistics • access to Bs decays • LHCb can fully exploit the large B-meson yields at LHC from the start-up • with excellent mass and decay-time resolution, and particle ID • with a flexible and robust trigger dedicated to B-physics • measure e.g. Dms with 5s in ~1month (for Dms <40 ps-1) • ATLAS and CMS will also contribute significantly • competitive for modes with muons and small BR Flavor Physics at LHC will contribute significantly to the search for NP via precise and complementary measurements of CKM angles and the study of loop decays  Flavor Physics and CP Violation

  28. Backup slides Flavor Physics and CP Violation

  29. g W b u,c,t s B0→ K0* g and Bs →f g In SM: loop-suppressed b → s g transitions BR( B0 K*0 g) = (4.30.4) 10-5 expected direct CP violation <1% for B0→ K*0 g expected CP violation in mixing ~0 for Bs→f g  sensitive to New Physics sm~ 64 MeV/c2 st~ 60 fs Preliminary study: for B→K 0*g s(ACP ) < 0.01 for one year LHCb for Bs →fg sensitivity study ongoing B→ Kp g Bs→ KK g In 1 year LHCb expects triggered and reconstructed: 35k eventsB0 K0* (K+p-)g; S/B>1.4 9.4k events Bs  f (K+K+) g ; S/B>0.4 ATLAS expected signal events/year: Bd  K*0g: ~3.3k ev. ; S/√BG > 5 Bs  f g: ~1.1k ev. ;S/√BG > 7 Flavor Physics and CP Violation

  30. Merged M2(p0p-) M2(p0p+) Resolved a from B0 p+p-p0 • Time-dependent Dalitz plot analysis of B0 rp  p+p-p0 permits extraction of a along with amplitudes + strong phases[Snyder & Quinn] • Neutral p0reconstruction with clusters unassociated to charged tracks • Annual yield ~ 14k events, S/B ~ 1.3 (LHCb)Complicated 11-parameter fit, studied with toy MCStatistical precision of s(a) ~ 10 achievable in one yearStudy of B0 rr has started, few 102r0r0 /year (for BR = 10-6) Efficiency for p0 reconstruction Flavor Physics and CP Violation

  31. LHC underground

  32. LHC status (March 2006) • All key objectives have been reached for the end of 2005. • End of repair of QRL, reinstallation of sector 7-8 and cold test of sub-sectors A and B. • Cool-down of full sector 8-1. • Pressure test of sector 4-5. • Endurance test of two full octants of power converters. • Magnet installation rate is now at 20 per week with more than 450 installed (25%). In the next month, we will ramp up to 25/week. Installation will finish end February 2007.

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