CKM angles measurements and New Physics at LHCb

1. V Workshop sulla Fisica pp a LHC Perugia, 1 February 2008 CKM angles measurements and New Physics at LHCb Marco Musy - University of Milano Bicocca

2. Very consistent picture… But: New particles may show up in loop diagrams, overconstrain will allow to disentangle SM components from the New Physics ones need very high precision! Motivations Current SM fit predicts • a = 91.2°± 6.1° • b = 21.9° ± 1.0° • = 66.7° ± 6.4° fs= 2.1° ± 0.2°

3.  Vub* Vtd   - - (ρ,) 0 Vcb 1 Vtb Vts* Outlook BSDSK B0D0K*0, B±DK± B0 & BSKK … B0ρ, B0ρρ, … • Measurements of b sin2b from Bd J/yKS and sin2beff from fKS • Measurements of g from various channels and extraction methods • New Physics in loops Hadronic penguin b  sssdecays (eg. Bs ff) Radiative penguin b  sgdecays (eg. Bd K*g, Lg) B0J/ψ KS B0KS

4. bfromB0 J/y Ks • The ‘gold plated’ channel at B-factories already well measured by Babar/Belle (s(sin2b)~0.019 for 2/ab) expected to be one of the first measurements in LHCb LHCb ACP(t) 2/fb (fast MC, incl. bkg) =sin 2b =0 in SM Proper time t (ps) In one year, 2/fb, with 236k events, s(sin2b)~0.02, s(b)~0.6° Try also to fit for direct CPV with higher stats LHCb • Comparing with other channels may indicate NP in penguin diagrams After 10/fb B0->fKs : Yield:0.9k, B/S<1.1 s(sin2beff) ~ 0.1

5. p+ p- B0 B0 D K- l b B0 d b d p+ u u Flavour Tagging • Knowledge of flavour at birth is essential for many of the CPV measurements • Opposite side lepton tag (bl ) • Opposite side kaon tag (bcs) - needs good Particle IDentification • Vertex charge tagging • Same side pion and kaon tag (with p coming either from B** or fragm. successfully used by CDF already) Figures: etag, w  NW/(NW+NR), eeff  etag(1-2w)2

6. Results of tagging are combined with a neural network and events are split into 5 tagging categories Cat 5 Cat 1 Fit flavour oscillations of B0J/y(mm)K*0 events in best and worse category • The mistag measured in the control channels cannot be directly used for the CP channels, due different bias introduced by trigger and selection. Need to consider trigger subsamples and possibly reweighting for different signal-B spectra to extract w • LHCb: eD2 = 4-5% for Bd eD2 = 7-9% for Bs • (precision needed: ~0.2% OS, ~1.2% SS)

7. (,) • Current experimental status: • From direct measurements withB→DK • decays:γ=(88±16)°(BaBar and Belle) • From the SM fit using all other • infos: γ=(65.1±6.5)°(UTFit) (0,0) (1,0) LHCb tree decays only σ(γ) ~5º with 2/fb, ~2.5º with 10/fb from tree

8. gfromBs Ds K Interference between direct decay and decay after oscillation • 2 same order tree level amplitudes (3) : large asymmetries, NP components unlikely! • From the measurement 4 rates and 2 time-dependent asymmetries one gets g+fs(with fs from BsJ/yf) Observed decay time Bs→DsK in 2/fb Yield: 6.2k signal events in 2/fb, B/S < 0.18 at 90% CL residual contamination from BsDsπ ~ 10% Precision: s(g) ~ 10° (Dms = 17.3/ps , |ds|<20°) Bs→ Dsπ also used in the fit to constrain other parameters (mistag rate, Δms, ΔΓs …) weak depn. of s on central values • Outlook: Bs Ds*K also sensitive to γ+fs. • Challenge: reconstruct soft photon from decay • Preliminary study: ~1.8k events per 2/fb

9. gfromB± DK± colour-allowed colour-suppressed u s u d }K- }p+ c u c u D0{ D0{ s u d u }K- }p+ Cabibbo-favoured Double Cabibbo-suppressed [Atwood, Dunietz, Soni method] • Measure relative rates of B-→ D(Kp) K- and B+→ D(Kp) K+ • Two interfering tree B-diagrams, one colour-suppressed (rB~0.08) • Two interfering tree D-diagrams, one Doubly Cabibbo Suppressed (rDKp=0.060)  large interference because of similar amplitudes Weak phase diff.: Magnitude ratio: rB Strong phase diff.: dB Magnitude ratio: rDKp Strong phase diff.:dDKp Measure: favoured ~55k evts suppressed ~0.7k evts

10. LHCb • 3 observables, 5 parameters (g, dB, rB , dDKp, rDKp) , rDKp = 0.060 known add more D-decays to constrain further: D →Kppp(Cabibbo favoured + DCS) • 3 new observables with 2 new parameters, dDK3p ; rDK3p=0.06 D →KK/pp(CP eigenstate, ~8k events) • 1 new relative rate, no new unknown: rDKK = 1 ; dDKK = 0 this may come from CLEO-c, cosd ~ ±20%  7 relative rates and 5 unknowns: g, rB, dB, dDK, dDK3 Precision: s(g) ~ 5°- 13°in 2/fb depending on dDK (|dDK|<25°) and on dDK3 (|dDK3|<180°) including background • Use of B±→ D*(Dp0,Dg) K± under study

11. m2(KS–) (770) K*(892) m2(KS+) D0 g from B±D0K± (GGSZ) [Giri, Grossman, Soffer, Zupan, PRD 68, 050418 (2003)] D0 decays into a 3-body CP eigenmode: D0KS0p+p- studying the D-Dalitz plots from B+ and B– decaysallows the extraction of rB, strong phase dB,and γ Assume no CP violation in D0 decays B decay amplitudes: A(B-DK-) AD(mKsp-2,mKsp+2)+ rBei(dB- g) AD(mKsp+2,mKsp-2) A(B+DK+) AD(mKsp+2,mKsp-2)+ rBei(dB+g) AD(mKsp-2,mKsp+2) Need to assume a D0 decay model. Current isobar model used at B factories syst() = 10 (K-matrix model approach reduces this to ~7) At LHCb: 5k signal events in 2/fb B/S = 0.24 (D0±), Bbb/S < 0.7 With more statistics plan to do a model-independent analysis and control model systematics using CLEO-c data at (3770) Depending on bkg assumptions stat() = 7–12 with 2/fb stat() = 4–6(10/fb)syst() = 3–4

12. gfromB0 D0K* 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 [ADS+GLW, Phys. Lett. B270, 75 (1991)] colour-suppressed • Measuring 6 decay rates (self-tagged and time-integrated) • allows extraction of g Precision: s(g) ~ 9°(2/fb, for 55°<g<105°, |D|<20°)

13. g from Bd pp, Bs KK p/K Bd/s p/K 2/fb stat() = 10 but fake solution 10/fb stat() = 5 decreased fake solution • Large penguin contributions, sensitive to NP • Evaluation of and parameters from time-dependent measured asymmetry depend on g, mixing phases, and ratio of penguin/tree = d eiq • Assume only 0.8< dKK/d <1.2 and let  , KKfree ~2x better than current B world average If assume U-spin symmetry dpp = dKK qpp = qKK (and fs,d from BsJ/yf, BJ/yKs) 4 measurements and 3 unknowns  can solve for  • Compare with tree level determinations • Exp. PID is a fundamental requirement!

14. Most of B decay channels require separation between final states with p and K LHCb can count on 2 RICH detectors Kaon identification: Effect on Bdp+p-:

15. αgen afrom B0 rp [Snyder,Quinn,1993] Thanks to the interferences between the transitions B rpπ-πoπ+ 14k events/year we can extract  from the time dependence of the tagged Dalitz plot. Challanging because of p0. 70 expts averaged (L=2/fb) 85% converge to the correct solution* r0p0 r+p- r-p+ Average σ(α) = 8.5º <10º in 90% of the cases • SU(2) analysis of B0→ρ+ρ–, ρ±ρ0, ρ0ρ0 • main LHCb contribution could be B0→ρ0ρ0 • with ~1k evts in 2/fb, and B/S<5 • Will need more study Da *prob. of mirror solutions decreases with stats, down to ~0.2% for 10/fb

16. s(sin2b) now s() [o] now pre-LHCb pre-LHCb with LHCb at L=10fb-1 with LHCb at L=10fb-1 with LHCbat L=2fb-1 with LHCbat L=2fb-1 year year • Reachable CKM angles precision up to year 2014 by LHCb: 2014 now s(g) [o] pre-LHCb with LHCbat L=2fb with LHCb at L=10fb-1 year Using , ,  and Dms from LHCb only

17. , in SM Radiative decays • Bd  K*ACP can be 10% - 40% in SUSY LHCb can measure it at less than 1% level. • Bs  No mixing-induced CP asymmetry in SM, up to 50% in SUSY. Sensitivity for ACP measurement under study. • Lb Right-handed component of photon polarization O(10%) in SM. Can be higher BSM. Measure photon asymmetry ag from angular distributions of g and hadron in Lb (pp,pK) decays. r = C7/C7 = ms/mb in SM 3 evidence of right-handed component to 21% with 10 fb–1 ´

18. s s  J/ Vtb Vts*   s s Vcs* Vcb bsss hadronic penguin decays In the SM penguin, cancellation of the mixing and decay phases: S  2 arg(Vts*Vtb) – arg(VtbVts*/Vtb*Vts) = 0 (CP violation in SM < 1%)  good ground to search for New Physics! Expect 3.1k signal events/year B/S < 0.8 at 90% CL Proper time resolution: 42 fs Angular analysis of decay to two vector particles  time-dependent CP asymmetries • Sensitivity • (D) ~ 6° for 2/fb • (D) ~ 3°for 10/fb

19. Conclusion • LHC experiments will allow to measure the Unitarity Triangle very precisely • LHCb is ready for data taking at 2008 LHC start-up • Very interesting results will come already with first 0.1-0.5/fb luminosity • Loop processes in the flavour sector will probe high energy scale!