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D 0 Mixing and CP Violation

D 0 Mixing and CP Violation. Boštjan Golob Belle & Belle II University of Ljubljana, Jožef Stefan Institute. 1. Phenomenology 2. Measurements 3. Decays to CP eigenstates 4. Hadronic WS decays 5. t-dependent Dalitz analyses 6. Average 7. Constraints 8. Outlook. q 2. q 1.

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D 0 Mixing and CP Violation

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  1. D0 Mixing and CP Violation Boštjan Golob Belle & Belle II University of Ljubljana, Jožef Stefan Institute 1. Phenomenology 2. Measurements 3. Decays to CP eigenstates 4. Hadronic WS decays 5. t-dependent Dalitz analyses 6. Average 7. Constraints 8. Outlook

  2. q2 q1 q2 q1 1. Phenomenology P0 P0 D0 mixing is FCNC of u-type quarks P0 = K0, Bd0, Bs0 and D0 Time evolution flavor states ≠ Heff eigenstates: (defined flavor) (defined m1,2 and G1,2) SM: |x|, |y|  O(10-2) |x|, |y| << 1  Decay time distribution of experimentally accessible states D0, D0 sensitive to mixing parameters x and y, depending on final state

  3. 1. Phenomenology Oscillation frequency P(P0P0) P(P0P0) Bs BdD0 x=0.8, y=0 x=26, y=0.15 x=0.01, y=0.01 Thus the system of the world only oscillates around a mean state from which it never departs except by a very small quantity Marquis de Laplace (1749 -1827)

  4. Vus* 1. Phenomenology K+ CP violation Vcs D0 D0: first two quark generations; CKM elements ≈ real; using CKM unitarity: below current exp. sensitivity; signals New Physics K- parameterization: RD ≠1: Cabibbo suppression AD ≠0: CPV in decay AM ≠0: CPV in mixing f ≠0 : CPV in interference

  5. 2. Measurements - general Experiments Cleo-c Belle BaBar CDF II Common methods D*+ →D0ps+ charge of ps flavor of D0; dM=M(D0ps)-M(D0)  background reduction p*(D*) > 2.5 GeV/c (or impact parameter) eliminates D0 from b → c

  6. 3. Decays to CP eigenstates Belle, PRL 98, 211803 (2007), 540fb-1 D0→ K+K- / p+p- CP even final state; no CPV: CP|D1> = |D1> t=1/G1; K-p+: mixture of CP states  t=f(1/G1,1/G2) S. Bergman et al., PLB486, 418 (2000) AM, : CPV in mixing and interference exp. issues: - good S/N (tagged decays) - precise modeling of decay-t resolution needed yCP=(1.24±0.39±0.13)% BaBar, PRD78, 011105 (2008), 384fb-1

  7. t-dependent: 3. Decays to CP eigenstates CPV t-dependent t-integrated: Belle, PRL 98, 211803 (2007), 540fb-1 BaBar, PRD78, 011105 (2008), 384fb-1 --CP= -1 (fKS) -- CP= +1 (a0(980)KS) related meas. D0→ fKS t’’ t’’ t’ m(K+K-) exp. issues: un-tagged decays; worse st due to Ks ; comparison of topologically equal decays → reduced effects of resolution in <t>

  8. 4. WS decays D*+→ D0pslow+ D0 → D0 → K+ p- DCS decays  interference; t-dependence to separate DCS/mixed • CPV allowed: • separate D0 and D0 tags • (x’2,y’,RD) → (x’±2, y’±,RD±) likelihood contours d: unknown strong phase DCS/CF BaBar, PRL 98, 211802 (2007), 384fb-1 3.9s 1s 2s 3s 4s AD = (-21 ± 52 ± 15) ·10-3 5s exp. issues: - signif. background in WS; - accurate resol. f. param.; - stat. issues for x’2<0; results of similar accuracy Belle, PRL 96, 151801 (2006), 400fb-1 CDF, PRL 100, 121802 (2008), 1.5fb-1

  9. 5. t-dependent Dalitz t D0→KSp+p- different types of interm. states; CF: D0→ K*-p+; DCS: D0→ K*+p-; CP: D0→r0 KS if f = f  relative phases determined (unlike D0→ K+p-); t-dependence: regions of Dalitz plane → specific t dependence f(x, y); D0→f exp. issues: - model system.; - direct meas. x, y; - any f = f: sensitivity to x depending on a priori unknown strong phase variation Belle, PRL 99, 131803 (2007), 540fb-1 m±2 = m2(KSp±), D0→f l1,2=f(x,y); n.b.:K+p-:x’2, y’ access directly x, y

  10. 6. Average Average of results K+K- c2 fit including correlations among measured quantities K+p- RM KSp-p+ d uncertainty c2/n.d.f.= 25.3/20 CPV http://www.slac.stanford.edu/xorg/hfag/charm/ (x,y)≠(0,0): 9.8 s; CP even state heavier and shorter lived; no CPV within 1s

  11. 8. Outlook 1, 2, 3 s @ 50 ab-1 expected sensitivity only KK/pp, Kp and Kspp projected sensitivities included HFAG c2 fit 50 ab-1 E. Barberio et al. (HFAG), arXiv:0808.1297 & http://www.slac.stanford.edu/xorg/hfag/

  12. 7. Constraints on NP constraints from mixing 21 NP models considered →17 with useful constraints; improved existing constraints; examples: E. Golowich et al., PRD76, 095009 (2007) D0 D0 R couplings 4th generation fermion R SUSY: mb’ [GeV] xD=1.00%±0.08% constraint (50 ab-1) xD=1.00%±0.25% constraint [GeV] xD=1.00%±0.08% constraint (50 ab-1) xD=1.00%±0.25% constraint |Vub’Vcb’|

  13. 8. Outlook unexploited possibilities with B-factory data T-odd moments: D →KKpp charmed baryon decays: Lc→Lp, L → pp exp. issues: -unpolarized Lc; - p, p detector asymmetry • a: (KK, ppplane); • exp. issues: • Br(D →KKpp) 1/2 Br(D →KK); • - angular analysis DCPV can be induced by FSI CPV

  14. Conclusion • D mixing and CPV are a unique handle to test FCNC of • u-like quarks • Important constraints on NP models from existing results • (yet to be fully confronted with other experimental constraints) • B-factories have not yet spoken the final word • (only part of possible measurements done) • Super-B factory can reach s(x,y)  5x10-4, • s(ACP~ x sinf, AM y cosf)  5x10-4 • (possible evidence for NP) there may be hidden treasures in charm physics....

  15. Supplementary slides

  16. Vuj* Vci* Vcj Vui u c W+ D0 D0 d, s, b d, s, b W- u c K+ D0 D0 K- Phenomenology more x and y in SM 2nd order perturb.: short distance: |x| ~ O(10-5) G. Burdman, I. Shipsey, Ann.Rev.Nucl.Sci. 53, 431 (2003) DCS SU(3) breaking absorptive part (real interm. states)  y dispersive part (off-shell interm. states)  x long distance: |x|, |y| ~ O(10-2) I.I. Bigi, N. Uraltsev, Nucl. Phys. B592, 92 (2001); A.F. Falk et al., PRD69, 114021 (2004) D0 mixing: rare process in SM; possible contrib. from NP

  17. Measurements – experim. more A) Experiments continuum production s(c c)  1.3 nb (~109 XcYc pairs) e+e-→ y(3770) → D0D0, D+D- (coherent C=-1 state); ~800 pb-1 of data available at y(3770) 2.8x106 D0D0 3.5 fb-1 on tape s(D0; pt>5.5 GeV,|y|<1)≈13 mb 50x109 D0’s very diverse exp. conditions ds(D0)/dpt [nb/GeV] c g* c

  18. K-p+ Decays to CP eigenstates more Fit Belle, PRL 98, 211803 (2007), 540fb-1 simultaneous binned likelihood fit to K+K-/K-p+/p+p- decay-t, common free yCP R : ideally each si Gaussian resol. term with fraction fi; : described by 3 Gaussians  event-by-event st trec-tgen/st parameters of R depend slightly on data taking conditions t = 408.7±0.6 fs

  19. Decays to CP eigenstates more D0→ K+K- / p+p- confirmation: BaBar, arXiv:0712.2249, 384fb-1 yCP=(1.24± 0.39±0.13)% yCP currently most precisely measured param.

  20. t-dependent: 3. Decays to CP eigenstates CPV t-dependent t-integrated: Belle, PRL 98, 211803 (2007), 540fb-1 BaBar, PRD78, 011105 (2008), 384fb-1 ACPKK ACPpp t-integrated ACPmeas =Aep + AFB + ACPf Aep: comparison of tagged/untagged (D*+→D0p+),D0→K-p+ AFB: asymmetric f(cosqCMS) exp. issues: - meas. in bins of pD, cosqD due to Aep(s determined by NKptag); - Aep can be used in other meas.; |cosqCMS| BaBar, PRL 100, 061803 (2007), 386fb-1 Belle, PLB 670, 190 (2008), 540fb-1

  21. 3. Decays to CP eigenstates related meas. D0→ fKS CP odd final state; t(fKS)= 1/G2 > 1/G1= t(K+K-) exp. issues: - un-tagged decays; - worse st due to Ks - comparison of topologically equal decays → reduced effects of resol. in <t> t’’ t’ t’’ m(K+K-) --CP= -1(fKS) -- CP= +1 (a0(980)KS) Belle, preliminary, 600fb-1

  22. Decays to CP eigenstates more D0→ fKs Belle, preliminary, 600fb-1 method

  23. Decays to CP eigenstates more D0→ fKs Belle, preliminary, 600fb-1 • Dalitz model • CP=-1 • fKs • CP=+1 • a0(980)Ks • a0(1450)Ks • f0(980)Ks • f0(1370)Ks • f2(1270)Ks • flavour spec. • K-a0(980)+ • K+a0(980)- • K-a0(1450)+ model affects only fraction of CP=+1 states in individual mass interval; small model syst. uncertainty

  24. Decays to CP eigenstates more D0→ fKs Belle, preliminary, 600fb-1 syst. uncertainty on Dt from MC (stat.) data fluctuations

  25. D*+→ D0pslow+D0 → D0 → K+p- Belle, PRL 96, 151801 (2006), 400fb-1 BaBar, PRL 98, 211802 (2007), 384fb-1 WS decays more C) WS decays (non-CP) CDF, PRL 100, 121802 (2008), 1.5fb-1 NWS/NRS NWS~13x103 CDF, PRL 100, 121802 (2008), 1.5fb-1 1s CDF: trigger: h+h- from second. vtx; NWS/NRS vs. t/t from M, dM, imp. param.; 2s 3s 4s

  26. t-dependent Dalitz more Belle, PRL 99, 131803 (2007), 540fb-1 D0→KSp+p- most accurate x K*X(1400)+ K*(892)+ r/w K*(892)-

  27. t-dependent Dalitz more BaBar, Lepton Photon 07, 384fb-1 D0→KSpp0 BaBar, PRL97, 221803 (2006), 384fb-1

  28. 5. t-dependent Dalitz Belle, PRL 99, 131803 (2007), 540fb-1 D0→KSp+p- exp. issues: - model system.; - direct meas. x, y; - any f = f: sensitivity to x depending on apriori unknow strong phase variation related meas. D0→K+p-p0 separate WS/RS Dalitz distributions; t-distrib. analogous to D0 →K+ p-; RS t-integrated Dalitz analysis; WS Dalitz analysis; no mixing point 0.8% C.L. dKpp: unknown strong phase shift DCS/CF BaBar, PRL97, 221803 (2006), 384fb-1

  29. Average more Expected sensitivities from individual meas. L = 5 ab-1L = 50 ab-1L = 5 ab-1L = 50 ab-1 s(x) 0.14% 0.10% 0.08% 0.05% KsKK, ppp0 total error :3 s(y) 0.11% 0.08% 0.06% 0.04% KsKK, ppp0 total error :3 s(yCP) 0.16% 0.11% s(AG) 0.12% 0.07% s(ACP) 0.12% 0.07% s(x’2) 0.11x10-3 0.09x10-3 0.13x10-3 0.10x10-3 x’2± stat. error •2 s(y’) 0.20% 0.16%0.23% 0.17% y’± stat. error •2 s(AD) 2.1% 1.7% s(RD) 5x10-5 1.5x10-5 7x10-5 2x10-5 RD± stat. error •2 s(|q/p|)0.13 0.09 0.08 0.05 KsKK, ppp0 total error :3 s(f) 0.12 rad 0.07 rad 0.07 rad 0.04 rad KsKK, ppp0 total error :3 i.e. assuming sens. same as in Kspp for CPV allowed fit total error scaled

  30. Average more Projected sensitivities from average 5 ab-1 5 ab-1, KsKK, ppp0 50 ab-1 50 ab-1, KsKK, ppp0 + assuming ACP=ADs(AD) ~ 0.1% LHCb, 10 fb-1 (5 y): s(x’2)~6x10-5, s(y’)~0.9x10-3 s(yCP)~0.05% main sensitivity on x, |q/p|, ffrom t-dependent Dalitz analyses of Kspp, ppp0, KsKK

  31. Average more y(3770) →D0D0 • constraints • average • direct meas. • (fit w/o external input) cosd 1.0 0.5 0 -0.5 -1.0 1 0 -1 y’ measured y’=ycosd-xsind [%] d measured 0 1 2 3 4 5 d [rad] 0 1 2 3 4 5 d [rad]

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