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Recent results on D 0 m ixing from Belle. Lepton Photon Interactions 2007. B. Golob University of Ljubljana Belle Collaboration. Outline Introduction Phenomenology Measurement s K + K - / p + p - K S p + p + CPV 4. Prospects & Summary. B. Golob, Belle.
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Recent results on D0mixing from Belle Lepton Photon Interactions 2007 B. Golob University of Ljubljana Belle Collaboration • Outline • Introduction • Phenomenology • Measurements • K+K-/p+p- • KSp+p+ • CPV • 4. Prospects & Summary B. Golob, Belle D0 Mixing 1 Lepton Photon ‘07, Daegu
→ D0-D0 Mixing Introduction U(4S): s(c c) 1.3 nb (Belle luminos.:~850·106 XcYc pairs) Dual role of charm - experimental tests of theor. predictions (most notably of (L)QCD); improve precision of CKM measurements (B physics); - standalone field of SM tests and search for new phenomena (SM and/or NP) E. Golowich et al., arXiv:0705.3650 mb’=500 GeV 21 different NP models: 17 of those→ constraints in parameter space from established D0 mixing rate <~10-4 example: mixing ampl. mb’=200 GeV 4th fermion family (severly constrained from other measurements as well) |Vub’Vcb’| B. Golob, Belle D0 Mixing 2 Lepton Photon ‘07, Daegu
Central Drift Chamber e+3.5 GeV 3(4) layer Si det. e-8 GeV Aerogel Cherenkov (n=1.015-1.030) m and KL Counter (14/15 layers RPC+Fe) EM calorimeter CsI (16X0) 1.5T SC solenoid Introduction 700 fb-1 Ldt 2000 2007 D0→ K-p+ D*+→D0p+slow, D0→K-p+ e(K±) ~ 85% e(p±→K±) 10% for p < 3.5 GeV/c <st>/t(D0) ~ 1/2 st/ t(D0)=1/3 st/t(D0) DM=M(Kppslow)-M(Kp) B. Golob, Belle D0 Mixing 3 Lepton Photon ‘07, Daegu
q2 q1 Decay time distribution of experimentally accessible states X0, X0sensitive to mixing parameters |x|, |y| <O(10-2) ~ D0 - D0 Phenomenology q2 q1 X0 X0 Mixing phenomena X0 = K0, Bd0, Bs0 and D0 t-dependent Schrödinger eq.: mass eigenstates: decay time evolution: CP eigenstates if q/p=1; propagate in t according to distincteigenvalues; I.I. Bigi, N. Uraltsev, Nucl. Phys. B592, 92 (2001);A.F. Falk et al., PRD69, 114021 (2004) B. Golob, Belle D0 Mixing 4 Lepton Photon ‘07, Daegu
Measurements Belle measurements - semileptonic decays, D0→ K(*) l n - hadronic decays to non-CP final state D0→ K+p- - hadronicdecays to multi-body final state, D0→ KSp+p- - decays to CP final state, D0→ K+K-/p+p- PRD72, 071101 (2005), 253 fb-1 common: D*+ →D0ps+ charge of ps tags the flavor of initially produced D0; p*(D*) > 2.5 GeV/c eliminates D meson production from b → c selection determined “blindly” PRL96, 151801 (2006), 400 fb-1 arXiv: 0704.1000, 540 fb-1, subm. to PRL PRL 98, 211803(2007), 540fb-1 B. Golob, Belle D0 Mixing 5 Lepton Photon ‘07, Daegu
PRL 98, 211803 (2007), 540fb-1 Measurements K+K- / p+p- D0→ K+K- / p+p- CP even final state; in the limit of no CPV: CP|D1> = |D1> measure 1/G1 side band S. Bergman et al., PLB486, 418 (2000) AM, : CPV in mixing and interference Signal M(K+K- ) , Q=M(K+K- ps)- M(K+K- )- M(p), st, selection optimized on MC B. Golob, Belle D0 Mixing 6 Lepton Photon ‘07, Daegu
K-p+ PRL 98, 211803 (2007), 540fb-1 MeasurementsK+K- / p+p- Fit simultaneous binned likelihood fit to K+K-/K-p+/p+p- decay-t, common free yCP constructed using event-by-event st M sideband event-by-event st parameters of R depend slightly on data taking conditions t = 408.7±0.6 fs tPDG=410.1±1.5 fs B. Golob, Belle D0 Mixing 7 Lepton Photon ‘07, Daegu
K+K-/p+p- and K-p+ratio PRL 98, 211803 (2007), 540fb-1 MeasurementsK+K- / p+p- c2/ndf=1.084 (ndf=289) Result + difference of lifetimes visually observable negligible CPV, yCP=y ±1 s 3.2 s from zero (4.1 s stat. only) evidence for D0 mixing (regardless of possible CPV) B. Golob, Belle D0 Mixing 8 Lepton Photon ‘07, Daegu
arXiv: 0704.1000, 540 fb-1, subm. to PRL < f | D0 > M= < f | D0(t)> analogous Measurements KSp+p- t-dependent Dalitz analysis different decays identified through Dalitz analysis; CF: D0→ K*-p+ DCS: D0→ K*+p- CP: D0→r0 KS their relative phases determined (unlike D0→ K+p-); t-dependence: m±2 = m2(KSp±) l1,2=f(x,y); n.b.:K+p-:x’2, y’ < f | D0 > sum of intermediate states B. Golob, Belle D0 Mixing 9 Lepton Photon ‘07, Daegu
arXiv: 0704.1000, 540 fb-1, subm. to PRL M signal rnd slow p combin. Measurements KSp+p- t Fit no CPV: fit M(m-2,m+2,t) to data distribution x, y Signal M(KSp+p- ) and Q= M(KSp+p-ps)- M(KSp+p-)- M(p); 3 s signal region in M, Q Nsig= (534.4±0.8)x103 P95% Dalitz model 13 BW resonances, non-resonant contr.; comb. bkg.: from M sideband B. Golob, Belle D0 Mixing 10 Lepton Photon ‘07, Daegu
arXiv: 0704.1000, 540 fb-1, subm. to PRL Measurements KSp+p- K*X(1400)+ Dalitz projection of fit K*(892)+ r/w K*(892)- test of S-wave pp contr. (f0, s1,2): K-matrix formalism Results (fit fractions, phases) in agreement with (measurement of f3) PRD73, 112009 (2006) B. Golob, Belle D0 Mixing 11 Lepton Photon ‘07, Daegu
t [fs] 2-d 68% C.L. region arXiv: 0704.1000, 540 fb-1, subm. to PRL Measurements KSp+p- Decay-t projection of fit most sensitive meas. of x; comb. bkg. x = 1.8 ± 3.4 ± 0.6% y = -1.4 ± 2.5 ± 0.9 % Cleo, PRD72, 012001 (2005) 2-d 68% C.L. region t = 409.9±0.9 fs tPDG=410.1±1.5 fs D0→ K(*)ln D0→ K+K-/p+p- D0→ K+p- PRL 98, 211803 (2007), 540fb-1 PRL96, 151801 (2006), 400 fb-1 PRD72, 071101 (2005), 253 fb-1 B. Golob, Belle D0 Mixing 12 Lepton Photon ‘07, Daegu
Measurements CPV CPV in D0 system first two generations involved: Wolfenstein parameter. CPV expected to be small in SM (singly Cabibbo supp. decays only) CPV in decay: CPV in mixing: CPV in interf. mix./decay: t distributions depend also on CPV parameters; x, y at upper limit of SM expectation →search for CPV; at current level of sensitivity positive signal clear indication of NP; B. Golob, Belle D0 Mixing 13 Lepton Photon ‘07, Daegu
separate t for D0, D0 95% C.L. Measurements CPV CPV in D0 → K+K- / p+p- CPV in D0 → KSp+p- include |q/p|(AM) and as additional free param. B. Golob, Belle D0 Mixing 14 Lepton Photon ‘07, Daegu
D0 →p+p-p0 D0 →p+p-p0 540 fb-1, preliminary Measurements CPV CPV in D0 →p+p-p0 CPV in decay, integrated over t and Dalitz space Belle preliminary Cleo, PRD 72, 031102 (2005) B. Golob, Belle D0 Mixing 15 Lepton Photon ‘07, Daegu
Measurements average Combination, no CPV all available meas.; observables (yCP, x, ...) → x, y, dKp , RD sum of likelihood curves, non-Gaussian shapes accounted for HFAG charm, http://www.slac.stanford.edu/xorg/hfag/charm/index.html B. Golob, Belle D0 Mixing 16 Lepton Photon ‘07, Daegu
Measurements average Combination, CPV observables (AG, x, ...) → |q/p|, , AD, x, y, RD, dKp c2 minimization, non-Gaussian shapes not accounted for HFAG charm, http://www.slac.stanford.edu/xorg/hfag/charm/index.html B. Golob, Belle D0 Mixing 17 Lepton Photon ‘07, Daegu
Prospects & Summary L = 5 ab-1L = 50 ab-1 s(x) 0.1% 0.07% s(y) 0.1% 0.07% s(AM)0.1 0.07 s(f) 0.1 rad 0.07 rad Super-B factory extrapolation of existing Belle results LHCb, 10 fb-1 (5 y): s(x’2)~6x10-5, s(y’)~0.9x10-3 s(yCP)~0.05% • Summary • 2007: D0 mixing established (slowest of all neutral mesons) • Belle presented first evidence for D0 mixing (yCP), most precise x meas.; confirmation in D0→ K+K-, KSp+p-,other sensitive modes? (esp. x, from Dalitz analyses, sign)? • combination of existing D0 mixing results: • established at ~5 s; x,y ~ O(10-2); s(x,y) ~ 0.3%; • observed mixing may (not) be arising from SM → • important CPV search • existing facilities: any CPV indication of NP • Super-B: allows to test CP asymmetries to few 10-4 (SM expectations) B. Golob, Belle D0 Mixing 18 Lepton Photon ‘07, Daegu
→ D0-D0 Mixing Introduction (bckup) √s = M(U(4S))c2= 10.58 GeV Physics of c-hadrons increased interest at B-factories in recent years B-factory, c-factory s(c c) 1.3 nb (~850·106 XcYc pairs) s(B B) 1.1 nb (~750·106 BB pairs) Dual role of charm standalone field of SM tests and search for new phenomena (SM and/or NP) experimental tests of theor. predictions (most notably of (L)QCD); improve precision of CKM measurements (B physics); B. Golob, Belle D0 Mixing 19 Lepton Photon ‘07, Daegu
q2 q1 Phenomenology bckup q2 q1 Mixing phenomena in course of life neutral meson X0 can transform into anti-meson X0 X0 = K0, Bd0, Bs0and D0 t-dependent Schrödinger eq.: mass eigenstates: eigenvalues: X0 X0 CP eigenstates if q/p=1 B. Golob, Belle D0 Mixing 20 Lepton Photon ‘07, Daegu
Vuj* Vci* Vcj Vui u c W+ D0 D0 d, s, b d, s, b W- c u if mi = mj due to CKM unitarity: no D0 D0 mixing D0 - D0 Phenomenology(bckup) Mixing description observation of K0: 1950 (Caletch) mixing in K0: 1956 (Columbia) observation of Bd0: 1983 (CESR) mixing in Bd0: 1987 (Desy) observation of Bs0: 1992 (LEP) mixing in Bs0: 2006 (Fermilab) observation of D0: 1976 (SLAC) mixing in D0: 2007 (KEK, SLAC) (evidence of) 6 years 4 years 14 years 31 years d-like quarks in loop |Vcb*Vub|<< |Vcs*Vus|, |Vcd*Vud| mainly d,s contrib.; md ~ ms mixing small (as opposed to Bd0, where term with mt2 |Vtb* Vtd|2 dominates) B. Golob, Belle D0 Mixing 21 Lepton Photon ‘07, Daegu
Vuj* Vci* Vcj Vui u c W+ D0 D0 d, s, b d, s, b W- u c K+ D0 D0 K- D0 - D0 Phenomenology(bckup) 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 B. Golob, Belle D0 Mixing 22 Lepton Photon ‘07, Daegu
D0 - D0 Phenomenology(bckup) Oscillations ~ Bs0 more difficult to observe oscillations within t visually unobservable deviation from pure exponential B. Golob, Belle D0 Mixing 23 Lepton Photon ‘07, Daegu
right sign (RS) PRD72, 071101 (2005), 253 fb-1 Semileptonic (bckup) • Semileptonic decays • Wrong charge combinations (WS): • D*+→ D0pslow+D0 → D0 → K(*)+e-n • no “DCS” decays NWS/NRS = RM (x2+y2)/2 • Reconstruct n: • missing momentum with • kinematic constraints • Signal: • DM = M(Kenpslow) - M(Ken) NRS = (229.45 ± 0.69) ·103 B. Golob, Belle D0 Mixing 24 Lepton Photon ‘07, Daegu
PRD72, 071101 (2005), 253 fb-1 Semileptonic (bckup) • Decay time: • reduce bkg., increase sensitivity; • <t >(bkg., RS) < <t >(mix. signal) • 6 bins in 1 < t < 10 Result: allowed RM = (0.20 ± 0.47 ± 0.14) ·10-3 RM < 1.2 · 10-3 95% C.L. dominating systematics from limited bkg. statistics (embedded pslow) B. Golob, Belle D0 Mixing 25 Lepton Photon ‘07, Daegu
PRL96, 151801 (2006), 400 fb-1 D*+→ D0pslow+D0 → D0 → K+p- K+p-(bckup) 3s Q interval Wrong charge combinations (WS): WS DCS decays interference t-dependence to separate DCS/mixed 3s M interval • Signal: • M=M(Kp) • Q = M(K p pslow) - M(Kp) - M(p) • 2D M-Q fit: WS NWS = 4024 ± 88 B. Golob, Belle D0 Mixing 26 Lepton Photon ‘07, Daegu
PRL96, 151801 (2006), 400 fb-1 K+p-(bckup) WS t dist. Decay time: resol. function from RS t(D0) = 409.9 ± 0.7 fs x’2, y’, RD free parameters Results: RD = (3.64 ± 0.17 ) ·10-3 x’2 = (0.18 ±0.210.23) · 10-3 y’= (0.6 ±4.03.9) · 10-3 95% C.L. (x’2, y’) contour frequentist, FC ordering B. Golob, Belle D0 Mixing 27 Lepton Photon ‘07, Daegu
PRL96, 151801 (2006), 400 fb-1 x’2 < 0.72 ·10-3 -0.99% < y’ < 0.68% no signif. CPV Measurements K+p-bckup 95% C.L. (x’2, y’) contour frequentist, FC ordering Results: RD = (3.64 ± 0.17 ) ·10-3 x’2 = (0.18 ±0.210.23) · 10-3 y’= (0.6 ±4.03.9) · 10-3 AD = (23 ± 47) ·10-3 AM = (670 ± 1200) ·10-3 no CPV CPV • CPV allowed: • separate D0 and D0 tags • (x’2,y’,RD) → (x’±2, y’±,RD±) (0,0) lies on 96.1% C.L. contour largest syst. due to p*(D*) selection B. Golob, Belle D0 Mixing 28 Lepton Photon ‘07, Daegu
1 s 2 s 3 s BaBar, hep-ex/0703020, 384fb-1, acc. to PRL K+p-BaBar comp. (bckup) Result RD = (3.03 ± 0.19) ·10-3 x’2 = (-0.22 ±0.37) · 10-3 y’= (9.7 ± 5.4) · 10-3 3.9 s including sys. error Comparison evidence for (x,y) (0,0) consistent B. Golob, Belle D0 Mixing 29 Lepton Photon ‘07, Daegu
3 s Prospects bckup 1 s perspective (1 ab-1) x, y at upper limit of SM expectation search for CPV; at current level of sensitivity positive signal clear indication of NP; s(x) ~ ±0.21% s(y) ~ ±0.17% B. Golob, Belle D0 Mixing 30 Lepton Photon ‘07, Daegu
arXiv: 0704.1000 KSp+p-syst. (bckup) D0→ KSp+p- M(KSp+p- ) and Q= M(KSp+p-ps)- M(KSp+p-)- M(p); 3 s signal region in M, Q B. Golob, Belle D0 Mixing 31 Lepton Photon ‘07, Daegu
arXiv: 0704.1000 KSp+p-syst. (bckup) D0→ KSp+p- model dependence [10-4]: Dx Dy -10.3 +0.1K*0(1430) DCS/CF -15% + 6.9 -2.5K*2(1430) DCS/CF -30% -1.6 -0.9 K*(1410) DCS & CF -20% -5.1 -4.1G(q2) const. --------------------------------- +10+6 Total model dep. -14-8 experimental: Dx Dy +7.6 -7.8 p* variation -5.6 -5.7 Dalitz pdf for bkg. from different t bins ----------------------- +9+8 Total experimental-7 -12 Largest systematics observed discrepancy from input in MC statistical uncertainty: s(x)=29x10-4 s(y)=24x10-4 B. Golob, Belle D0 Mixing 32 Lepton Photon ‘07, Daegu
arXiv: 0704.1000 KSp+p-syst. (bckup) D0→ KSp+p- Largest systematics model dependence [10-4]: Dx Dy -10.3 +0.1K*0(1430) DCS/CF -15% +12.5 -4.4K*2(1430) DCS/CF fixed to K*(892) -6.4 +5.0 K*(1410) DCS & CF fixed to K*(892) --------------------------------- +15 +8 +10+6 Total model dep. -16 -9-14-8 B. Golob, Belle D0 Mixing 33 Lepton Photon ‘07, Daegu
arXiv: 0704.1000 KSp+p-param. (bckup) D0→ KSp+p-parameterization B. Golob, Belle D0 Mixing 34 Lepton Photon ‘07, Daegu
arXiv: 0704.1000 KSp+p-param. (bckup) D0→ KSp+p- CP=+1 states parameterization as in Cleo, PRD 63, 092001 (2001) B. Golob, Belle D0 Mixing 35 Lepton Photon ‘07, Daegu
arXiv: 0704.1000 KSp+p-param. (bckup) D0→ KSp+p- CP= -1 states parameterization as in Cleo, PRD 63, 092001 (2001) B. Golob, Belle D0 Mixing 36 Lepton Photon ‘07, Daegu
arXiv: 0704.1000 KSp+p-K-matrix (bckup) BW formalism: M(s1) = 527 ±6 MeV/c2 G(s1) = 442 ±10 MeV M(s2) = 1031 ±11 MeV/c2 G(s2) = 94 ±6 MeV D0→ KSp+p- scalar pp K-matrix formalism: unit. relat. for 2-body scatt. trans. operator: T: NchxNch matrix for Nch coupled chann.; r: density of final states product. ampl.: product. process (init. state non-interacting with channel j); trans. ampl. unitarity: satisf. by defining parameters taken from: unitarity satisf. if V.V. Anisovich, A.V. Sarantev, Eur.Phys.J. A16, 229 (2003) BaBar, hep-ex/0507101 B. Golob, Belle D0 Mixing 37 Lepton Photon ‘07, Daegu
arXiv: 0704.1000 KSp+p-eff., resol. (bckup) D0→ KSp+p- efficiency and resol. in M(pp) rnd ps bkg.: Prnd [(1-fw) M(m-2,m+2,t) +fwM(m+2,m-2,t)] R(t) fw from fit to Q side band: fw= 0.452 ± 0.005 diff. w.r.t. fw=0.5 in systematic error comb. bkg.: Pcmb B(m-2,m+2) * ([ d(t) + Exp(t) ]R’(t) parameters from fit to Dalitz and t distrib. of M(KSp+p- ) sideband (systematics: Dalitz distrib. in different t intervals) B. Golob, Belle D0 Mixing 38 Lepton Photon ‘07, Daegu
arXiv: 0704.1000 KSp+p-toy MC (bckup) D0→ KSp+p- MC tests, correct reconstruction of input; t-projection; PsigM(m-2,m+2,t) R(t) Prnd [(1-fw) M(m-2,m+2,t) +fwM(m+2,m-2,t)] R(t) Pcmb Msideband(m-2,m+2,t) * [ d(t) + Exp(t) ]R’(t) B. Golob, Belle D0 Mixing 39 Lepton Photon ‘07, Daegu
hep-ex/0703036v2 K+K-/ p+p-, M, Q (bckup) D0→ K+K-/ p+p- M [GeV/c2] B. Golob, Belle D0 Mixing 40 Lepton Photon ‘07, Daegu
hep-ex/0703036v2 K+K-/ p+p-, systematics (bckup) D0→ K+K-/ p+p- systematics K+K- only: yCP=(1.25 ±0.39)% AG=(0.15 ±0.35)% p+p- only: yCP=(1.44 ±0.57)% AG=(-0.28 ±0.52)% B. Golob, Belle D0 Mixing 41 Lepton Photon ‘07, Daegu
K-p+ PRL 98, 211803 (2007), 540fb-1 K+K- / p+p-resolution (bckup) Fit 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 tPDG=410.1±1.5 fs B. Golob, Belle D0 Mixing 42 Lepton Photon ‘07, Daegu
hep-ex/0703036v2 K+K-/ p+p-, t fit (bckup) < t > D0→ K+K-/ p+p- systematic checks running periods w/ diff. conditions robust to resol. f. shape; R(t): single Gauss → Dt=3.5%, DyCP=0.01%; no bias, reweigted MC: yCP(out) - yCP(in) < 0.04%; background P=98% (KK), 99% (Kp), 92% (pp); changing data side band/MC signal, DyCP = -0.04%; bkg. subtracted / no bkg. subtraction, DyCP = -0.07%; bkg. subtracted / MC signal subtr., DyCP= -0.03%; fitted t0 of R for Kp B. Golob, Belle D0 Mixing 43 Lepton Photon ‘07, Daegu
hep-ex/0703036v2 K+K-/ p+p-, t0 (bckup) D0→ K+K-/ p+p- fitted t0 of R in diff. run periods and diff. decay modes B. Golob, Belle D0 Mixing 44 Lepton Photon ‘07, Daegu
hep-ex/0703036v2 K+K-/ p+p-, t0 (bckup) D0→ K+K- / p+p- equal t0 assumption DyCP=t0CP - t0Kp / tKp from MC cocktail, including running periods with slight misalign. of SVD B. Golob, Belle D0 Mixing 45 Lepton Photon ‘07, Daegu
hep-ex/0703036v2 K+K-/ p+p-, bkg t distr. (bckup) D0→ K+K-/ p+p- background comparison small tail of signal present in side band, only visible in Kp sample; fraction of rnd ps negligible: 0.3%, 0.3%, 0.2% KK Kppp B. Golob, Belle D0 Mixing 46 Lepton Photon ‘07, Daegu
K+K-/ p+p-,KSp+p-comparison (bckup) Results KSp+p- : (x,y)=(0,0) has C.L. 2.6% K+K- / p+p-:y=0 has C.L. 6x10-4 B. Golob, Belle D0 Mixing 47 Lepton Photon ‘07, Daegu
Measurements average (bckup) Combination, no CPV sum of likelihood curves, non-Gaussian shapes accounted HFAG charm, http://www.slac.stanford.edu/xorg/hfag/charm/index.html x yCP B. Golob, Belle D0 Mixing 48 Lepton Photon ‘07, Daegu
Measurements average (bckup) Combination, no CPV sum of likelihood curves, non-Gaussian shapes accounted HFAG charm, http://www.slac.stanford.edu/xorg/hfag/charm/index.html dKp y B. Golob, Belle D0 Mixing 49 Lepton Photon ‘07, Daegu
Measurements average (bckup) Combination, no CPV sum of likelihood curves, non-Gaussian shapes accounted HFAG charm, http://www.slac.stanford.edu/xorg/hfag/charm/index.html y D0 → K+ p- y’ x’2 x CPV: AD = (-0.76 ± 3.10)% B. Golob, Belle D0 Mixing 50 Lepton Photon ‘07, Daegu