Quantum-correlated D-decays at CLEO-c HEP 2009 16-22 July 2009, Krakow, Poland Quantum-correlated D-decays at CLEO-c Stefania Ricciardi (RAL) for the CLEO Collaboration - Content - First measurement of the strong-phase difference DdD between D0 and D0 decays to KSp+p- Preliminary results on DdD between D0 and D0 to KSK+K- Including their impact on the CKM angle g (f3)

Quantum-correlation at CLEO-c 818 pb-1 accumulated in e+e- →y(3770) Just above open-charm threshold Coherent decay of y(3770) → D0D0  Reconstructing one D decay in a CP eigenstate (CP-tag) allows one to infer CP of the other D (decay mode of interest) CP(signal) = -1 x CP(tag) e.g., decay mode of interest is D0 → KSp+p- (mixed CP) CP(KSpp vs CP-even tag) = -1 CP(KSpp vs CP-odd tag) = +1 KSpp vs CP+ Ksr KSpp vs CP- Coherence in CLEO-c data: CP+ and CP- show different resonant structures EPS HEP 2009 Stefania Ricciardi

Cleo-c clean environment  useful kinematic constraints, e.g.: Mbc  excellent signal purity KSpp Mbc = (E2beam-pD2) M2missing for reconstruction of KL KSpp vs K-p+ Threshold running advantages: very clean environment no fragmentation particles efficient reconstruction of both D decays KLpp EPS HEP 2009 Stefania Ricciardi

DdD from quantum-correlated data: the principle D0 → K+ e- ne D0 → KS p+ p- DCP+ → K+ K- DCP- → KS p+ p- Y(3770) Y(3770) Flavour tagged |D0|2 or |D0|2 CP-tagged |D0|2 + |D0|2 ±2|D0||D0| cos(DdD) cos(DdD) from CP-tagged decays without model assumptions on the intermediate resonances In addition, mixed CP-tagged decays, sensitive to both cos(DdD) and sin(DdD) EPS HEP 2009 Stefania Ricciardi

Crucial role of DdD in the measurement of the CKM-angle g B- D0K- D0K- B± decay rates depend on the relative phase differences between the two interfering amplitudes, therefore on and on (KSpp)K- Unbinned fit used to extract g, rB and dB from B→D(Ksh+h-)K distributions in the D Dalitz plane. Relies on a model of the D-decay amplitude Model introduces a systematic uncertainty of BaBar [PRD 78(2008)034023]: KSππ ~7º Belle [ArXiv:0803.3375[hep-ex]]: KSππ ~9º BaBar [PRD 78(2008)034023]: KSππ + KSKK ~5º Model Systematic hard to quantify Will limit LHCb and future B-experiments EPS HEP 2009 Stefania Ricciardi

Model-independent method Discrete measurements of DdD in Dalitz plane bins are sufficient to extract g in a model-independent way [GGSZ, PRD 68(2003)054018] Ti = i |AD(x,y)|2 dxdy from flavour specific D decays ci and si are weighted averages of cosine and sine of DdD in bin I (flavour-amplitude weighted) These coefficients are simple functions of CP, mixed-CP, and flavour-tagged D→Kshh decay yields in bin i (and –i) EPS HEP 2009 Stefania Ricciardi

DdD between D0 and D0 decays to K0p+p- ArXiv:0903.1681 [hep-ex] accepted by PRD

D0→KSp+p-: DdD binning Bins of equal size in DdD give best sensitivity for g Bin boundaries assume a D0 decay model (BaBar isobar model, PRL 95 (2005)121802) ..but NO model error! [Bondar & Poluektov, EPJ C 55(2008) 51; EPJ C47 (2006) 347] No bias in g extraction with binned method and phase binning. Limited model accuracy may affect the g statistical precision only Phase binning of the D0→ Kspp plane EPS HEP 2009 Stefania Ricciardi

KSp+p- and KLp+p- Data Samples (Cleo-c, 818 pb-1) Both KSpp and KLpp are used in the measurement to reduce statistical error Data yields: ~ 20,000 Flavour-tags → Ti ~1,600 CP-tags → ci ~1,300 KSp+p- → ci and si Signal to background ~10 to ~100 depending on mode EPS HEP 2009 Stefania Ricciardi

KSp+p- and KLp+p- vs CP-tags Kshh vs CP ~ KLhh vs CP O(tan2qc) corrections to approximate equality introduce a small model systematic error EPS HEP 2009 Stefania Ricciardi

Broad agreement between Results on ci and si Two sets of coefficients extracted ci, si for KSpp ci,’ si’ for KLpp Broad agreement between measured values and predicted values from BaBar model Central values ± stat.±syst. ± (KLpp Kspp syst) Separate systematic uncertainty to account for KLpp Kspp model difference (model predicted differences Dci = ci’-ci and Dsi=si’-si used as constraint in the simultaneous fit) Statistic uncertainty dominant EPS HEP 2009 Stefania Ricciardi

Impact on CKM angle g Impact estimated with toy MC study Large sample of B+→D(KSp+p-)K+ data generated with g = 60 ° dB =130° rB =0.1 ~1.7° residual error on g due to finite knowledge of ci and si [Instead of model error (~7°-9°)] G.Wilkinson, Charm09 Extrapolated total error for B+→D(KSp+p-)K+ at LHCb After 10 fb-1, if rB=0.1 Unbinned fit with model assumptions: 8.5° (systematic dominated) Binned fit with Cleo-c input: 6° (statistics dominated) EPS HEP 2009 Stefania Ricciardi

DdD between D0 and D0 decays to K0K+K- Preliminary Results (new)

ΔδD (K0K+K-) binning ΔδD bins boundaries defined using the BaBar model for D0→KSK+K- decay amplitude Simpler resonant structure than D0 → Ksp+p- predicted, but branching fraction ~1/6 BaBar model [PRD 78, 032023 (2008)] EPS HEP 2009 Stefania Ricciardi

ΔδD (K0K+K-) binning ΔδD bins boundaries defined using the BaBar model of D→KSK+K- decay amplitude Toy MC predicts good sensitivity to g for 3 bins [PRD 78, 032023 (2008)] BaBar model 1 2 3 C.M.Thomas’ courtesy EPS HEP 2009 Stefania Ricciardi

KsK+K- and KLK+K- data samples Tag Modes KSKK KLKK K+K- , π+π, KSπ0π0  KSπ0, KSη(γγ), KSη(π+π-π0), KSω(π+π-π0), KSη’(π+π-η) KLπ0, KLη(γγ), KLη(π+π-π0), KLω(π+π-π0), KLη’(π+π-η) KLπ0π0 Total CP ± tags 96 123 KSππ KLππ Total Mixed CP tags (K0hh) 200 126 KSKK vs KLKK 10 K0KK vs Flavour 497 887 Many different CP- and CP+ tagging decay modes reconstructed in order to mitigate statistics limitations Raw data yields: ~ 550 CP/CP-mixed tags ~1,400 Flavour tags Background/Signal 5-10% for KSKK ~30% for KLKK EPS HEP 2009 Stefania Ricciardi

KSK+K- vs flavour-tags (Cleo-c, 818 pb-1) Flavour tags: K+π- and K+π-π0 EPS HEP 2009 Stefania Ricciardi

K0K+K- vs CP-tags (Cleo-c, 818 pb-1) Ksf KsKK CP tag - CP tag - CP tag + KLf KLKK EPS HEP 2009 Stefania Ricciardi

ci and si (KSK+K-) preliminary results and impact on g + Cleo-c preliminary (statistical error only) Model predictions [BaBar, PRD 78, 032023 (2008)] Good agreement of measured values with BaBar model predictions Errors bigger than KSpp due to smaller yields, especially in third (red) bin ~5-6° projected uncertainty on g from B→ D0(KSKK)K± due to Cleo-c statistical uncertainty RMS =5.5° Preliminary EPS HEP 2009 Stefania Ricciardi

KS,LK+K- all results: ci, si and ci’,si’ + Cleo-c preliminary (statistical error only) Model predictions [BaBar, PRD 78, 032023 (2008)] KSK+K- KLK+K- No significant difference between the two sets of measurements Good agreement with predictions overall - KSKK and KLKK model predictions differ visibly only in bin 3 where yields are small, but measured difference not significant EPS HEP 2009 Stefania Ricciardi

Conclusions Charming quantum-correlation effects in Cleo-c data y(3770) coherent decay exploited to measure DdD in 8 bins of the D0 →KS,Lp+p- Dalitz planes (PRD to appear soon) and 3 bins of the D0 → KS,LK+K- Dalitz planes (preliminary) Other DdD measurements by Cleo-c (not presented here) D0→K-p+ [PRL 100 221801 (2008), PRD 78,012001 (2008)] D0→K-p+p0, D0→K-p+p-p+ (coherence factor and average DdD) [arXiv: 0903.4853[hep-ex]] Crucial role of DdD in the precision of the extraction of CKM-angle g, especially important for future measurements at LHCb and super-B Fine example of synergy between charm and B-physics programme and of global science in the collaboration among different experiments Many thanks to BaBar, Belle and LHCb collaborators for sharing Dalitz plot bitmaps, expertise and fruitful discussions EPS HEP 2009 Stefania Ricciardi

Additional material

From yields to ci(`) and si(`) Observables Normalisations Mi = Number of KShh vs CPtag in bin i Mij = KShh in bin i vs Kshh in bin j Mi =KLhh vs CPtag in bin i Mij = KShh in bin i vs KLhh in bin j Ki = ADTi number of flavour-tagged decays in bin i EPS HEP 2009 Stefania Ricciardi

KLhh vs KShh and Residual Model Uncertainty DCS Correction to approximate equality between KSpp and KSKK Minus sign introduce a 180 degrees shift for all DCS resonances CP eigenstate resonances acquire a factor  -2reid [r = tan2(qc)] Residual model dependence due to uncertainty on this small correction small effect EPS HEP 2009 Stefania Ricciardi

KLpp ci’ –ci Measured and predicted (from D0-decay model) difference in the range 0.1-0.4, depending on bin EPS HEP 2009 Stefania Ricciardi

EPS HEP 2009 Stefania Ricciardi