Studies of charmed particle decays at Belle Manmohan

Studies of charmed particle decays at Belle Manmohan Dash, Virginia Tech For Belle Collaboration DPF/JPS-2006, 29 Oct - 03 Nov 2006, Honolulu, Hawaii 1

Branching Fraction(BF) and Form Factor(FF) measured in the charm sector by Belle recently… q D 0 + - 0: Relative BF q D 0 ( -/K- )l+ : Absolute BF & FF q c+ p+ K- + : Absolute BF q Ds+ K- K+ +: Absolute BF Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 2

These BF measurements were motivated by the fact that… q Many B-meson decay analyses and CPV studies rely on the knowledge of D-meson BF q Double tag BF measurement method uses charm production at the threshold. (BES-III, CLEO-c) q The high luminosity of B-factories provides competitive results in charm q Quasi 2 -body e+e- annihilation processes at 10. 5 Ge. V allow us to obtain clean samples of tags Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 3

The measurements were carried out at the Belle Detector situated in the KEKB B-Factory. 3. 5(e+) × 8(e−) Ge. V 3 km circumference 11 mrad crossing angle ∫L dt = 630 fb− 1 Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Hawaii 4

D 0 + - 0 BF, measured relative to the D 0 K- + 0 BF hep-ex/0610062 PID efficiencies = 93%, K = 86 K misidentification = 9% misidentification = 4% Lower cut rejects fake combinatorial D* from B-mesons Event Selection q tagged by D*+ D 0 slow+ or cc mode q 3. 5 Ge. V/c < p. D* in (4 s) cm frame < 4. 3 Ge. V/c q Likelihood ratio cut for charged K/ selection q 0’s from photon pairs, selection on invariant mass and energy of the pair. MC M( + - 0) q D 0 Ks 0 0 rejected by veto on ( + -) inv. mass Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 5

Efficiency calculation D 0 + - 0, Relative BF 3 resonance model for + - 0 ( +, -, 0 and non-resonance contribution) 7 resonance model for K- + 0 ( +, K*-, K 0*, K 0(1430)-, K 0(1430)0, (1700)+, K*-(1680) and non-resonance contribution) D. Cronin-Hennessy et al. (CLEO Collaboration), Phys. Rev. D 72, 031102 (2005), 3 -resonance S. Kopp et al. (CLEO Collaboration), Phys. Rev. D 63, 092001 (2001), 7 -resonance q 1. 2 million phase space MC, each decay mode q Events weighted by resonance models from CLEO q Efficiency ( + - 0) = 13. 433%, (K- + 0) = 13. 065% Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 6

D 0 + - 0, Relative BF Backgrounds Misid K 0 Random slow D 0 + - 0 Kn Random slow Misid 0 D 0 K- + 0 q Nontrivial features coming from misidentified kaons or pions, peaks under the signal from random slow and true D 0 combination or D 0 K n , n≥ 3 in case of K- + 0 q Has been fitted to Gaussians and�polynomial and polynomial X error function. Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 7

Signal fit and yield in data D 0 + - 0, Relative BF q + - 0 signal is fitted to a bifurcated Gaussian and a regular Gaussian. q K- + 0 signal is fitted to two bifurcated Gaussian Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 8

Systematic uncertainties D 0 + - 0, Relative BF 0 and tracking efficiency uncertainties cancel Leading sources of systematics q Data/MC PID efficiency difference q Decay model q Ks veto requirement Error estimated by varying this requirement Recalculate efficiency + - 0 : 3 model resonance without interference. K- - 0 : 3 model resonance Correction estimated using large independent sample of D 0 K- +, tagged by D* D 0 Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 9

Summary & conclusion D 0 + - 0, Relative BF 357 fb-1 data at Belle detector BF(D 0 + - 0)/BF(D 0 K- + 0) = 0. 0971 ± 0. 0009 stat ± 0. 0030 syst Our preliminary result 0. 0971± 0. 0031 World Average 0. 0929± 0. 0054 Our result is compatible with WA but more precise. Known BF(D 0 K- + 0), for Belle, Known BF(D 0 K- +), for CLEO A High Statistics Dalitz Plot Analysis is Underway Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 10

D 0 ( -/K- )l+ : Absolute BF & FF Method of Reconstruction (Event Topology) additional primary mesons IP 3. 5 Ge. V e+ e- 8 Ge. V D*- D Ktag K Tag side p(D*(tag)), slow mass-constrained vertex fits K p(e+e-), All possible combinations included D 0 „inverse“ p( (sig)) slow fit p(D*(sig)) K + e/µ- Signal side 11

D 0 ( -/K- )l+ : Absolute BF & FF Inclusive D 0 Signal =0. 0006 Ge. V signal D 0 invariant mass / Ge. V/c 2 PRL 97, 061804 (2006) Result 282 fb-1 of BELLE data Yield After cuts 95250 Background 38789 830 Signal 56461 309 830 WS events used to estimate amount of fake D 0 12

D 0 ( -/K- )l+ : Absolute BF & FF Signal, Background Decomposition Similar for D 0 K m D 0 Ke data remaining signal 0 data fake-D bkg data hadronic bkg data Kl bkg MC K* l bkg D 0 e mass via recoil of K/ and lepton(e/m) on signal side, m ² / Ge. V² v Fake D 0: estimated from the side bands using WS events v Kl (in l Simulated Kl , reweighted to the observed number in data v Hadronic: Opposite sign of lepton, slow ensures no semileptonic background or signal events. Positively identified K and in MC assigned a lepton mass, distributions fitted to the OS data sample Result 282 fb-1 Ke Km e m Signal 1318 ± 37 ± 7 1249 ± 37 ± 25 126 ± 12 ± 3 106 ± 12 ± 6 13

D 0 ( -/K- )l+ : Absolute BF & FF Form Factors – q² distribution D 0 Ke D 0 e signal q² non-D bkg hadronic bkg (q²) = 0. 0145 Ge. V²/c² (width of red line) no unfolding necessary! background shapes from data semileptonic bkg D 0 Km D 0 m 14

D 0 ( -/K- )l+ : Absolute BF & FF Form Factors and Comparison with Models two form factors f+(q²) and f(q²), f-(q²) suppressed by ml² three models in literature simple pole D 0 Kl modified pole model lattice calculation ISGW 2 model pole mass (Ge. V) Kl 1. 82 ± 0. 04 stat ± 0. 03 syst l 1. 97 ± 0. 08 stat ± 0. 04 syst modified pole f+(0) (poles fixed at theo. values) Kl 0. 695 ± 0. 007 stat ± 0. 022 syst l 0. 624 ± 0. 020 stat ± 0. 030 syst D 0 l Kl 0. 52 ± 0. 08 stat ± 0. 06 syst l 0. 10 ± 0. 21 stat ± 0. 10 syst 15

D 0 ( -/K- )l+ : Absolute BF & FF Summary & Conclusion v Four D 0 semiletonic absolute BF measurements, D 0 � / K� m being the first such measurement. v Measurement of q 2 dependent decay widths with very good q 2 resolution v Absolute BRs of better accuracy than previous experiments, good agreement with recent CLEO measurements v Form factor measurements, good agreement with theory and other experiments, competitive with recent CLEO-c measurements 16

c+ p+ K- + : Absolute BF q This is a poorly measured BF, all other c BFs are measured wrt this decay, use e+e- c p. D* q Reconstruct D, p, and look at c/ c* mass in the recoil mass distribution, yield measured BF q Reconstruct c, p, and look at the D(*) mass in the recoil mass distribution, yield known D(*) BFs 17

c+ p+ K- + : Absolute BF 18

Ds+ K+ K- + : Absolute BF Double Partial Reconstruction q Use e+e- Ds 1 Ds*, Ds*+ Ds+ , Ds 1 - DK(D*0 K- / D*K s 0 ) q 1 st tag: full D s 1 reconstruction, from Ds* Ds+ , yield absolute D* BF q 2 nd tag: full Ds*+(in Ds+ ) and K from Ds 1 - DK, yield related + + - + Mrecoil(Ds 1) Mrecoil(Ds*) 19

Ds+ K+ K- + : Absolute BF Recoil mass difference, Mrecoil Narrow signal peak, no peaking background, similar for Ds* q much better resolution than Mrecoil q Reduce background to negligible level, most systematics cancel out 20

Ds+ K+ K- + : Absolute BF Perform fit in Mrecoil, reduce residual background 21

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Backup slides 23

D 0 + - 0, Relative BF Comparison with Ba. Bar Belle: ß(D 0 + - 0)/ß(D 0 K- + 0) = 0. 0971 ± 0. 0009 stat ± 0. 0030 syst. Bar: 0. 1059 ± 0. 0006 ± 0. 0013. The Belle result differs by ∼ 2. 8 REF. B. Aubert et al. (BABAR Collaboration), hep-ex/0608009. 24

D 0 + - 0, Relative BF measurement, hep-ex/0610062 �� q A high statistics Dalitz plot analysis is underway 1. Insight into s wave + - contribution in these decays 2. Sensitive CP violation study in neutral D Mesons Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 25

Event selection PID efficiencies = 93%, K = 86 K misidentification = 9% misidentification = 4% D 0 + - 0, Relative BF data/MC agreement. Rejects fake combinatorial D* from B-mesons q tagged by D*+ D 0 slow+ or cc mode q 3. 5 Ge. V/c < p. D* in (4 s) cm frame < 4. 3 Ge. V/c q PID Likelihood ratio cut for K/ selection q energy of photons forming 0 > 0. 06 Ge. V q 0. 124 Ge. V/c 2 < photon pair invariant mass < 0. 148 Ge. V/c 2 q 0 lab momentum > 0. 3 Ge. V/c q 0. 1442<M( slow + - 0)-M( + - 0)<0. 1448 q 0. 1440<M( slow K- + 0)-M(K- -+ 0)<0. 1470 q 0. 21 Ge. V 2/c 4 < M 2( + -) < 0. 29 Ge. V 2/c 4: vetoes D 0 Ks 0 0 MC M( + - 0) Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 26

Efficiency calculation D 0 + - 0, Relative BF 3 resonance model for + - 0 ( +, -, 0 and non-resonance contribution) 7 resonance model for K- + 0 ( +, K*-, K 0*, K 0(1430)-, K 0(1430)0, (1700)+, K*-(1680) and non-resonance contribution) q 1. 2 million phase space distributed MC events for each decay mode restricted to D* momentum region, 3. 5 Ge. V/c to 4. 3 Ge. V/c in (4 s) cm frame q Events for both samples weighted by resonance models from CLEO q Obtained yield normalized to same MC data before detector simulation or event selection q ( + - 0) = 13. 433± 0. 077 %, (K- + 0) = 13. 065± 0. 074 % Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 27

Background description D 0 + - 0, Relative BF q 250 fb-1 generic MC and corresponding data for comparison. q 1 st order polynomial x error function + 1 st order polynomial (combinatoric background) + Gaussian peak in the signal region q sum of a 2 nd order polynomial and a 2 nd order polynomial X an error function + two Gaussians. Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 28

Signal fit and yield in data D 0 + - 0, Relative BF q For + - 0 background shape in MC with floating normalizations and partially fixed MC signal shape with floating normalization and ’s. MC signal function is a bifurcated hyperbolic Gaussian and a regular Gaussian. q For K- + 0 background shape in MC with floating normalizations and sum of 2 bifurcated hyperbolic Gaussians and a regular Gaussian with floating parameters(background is low and statistics is high) Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 29

Systematic uncertainties Pipipi 0: 3 model resonance with and Without interference. Kpipi 0: 7 model and 3 D 0 + - 0, Relative BF Correction to BF gives uncertainty, estimated using large independent sample of D 0 K- + model resonance q Uncertainty on tracking efficiency ( + - or K- +) and 0 and slow reconstruction efficiencies cancel out q Possible data/MC PID efficiency difference q Systematics due to decay model q Alternative background fitting function q Alternative signal fitting function q Change in PID requirement: negligible error q Change in p. D* requirement q Change in Ks veto requirement Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 30

Summary D 0 + - 0, Relative BF q Using 357 fb− 1 of data collected with the Belle detector first direct measurement of the relative branching fraction ß(D 0 + - 0) / ß(D 0 K- + 0) = 0. 0971 ± 0. 0009 stat ± 0. 0030 syst. has been performed. q Our preliminary result 0. 0971± 0. 0031 is compatible with the world average 0. 0929± 0. 0054 but more precise. q Using 2006 world average the D 0 + - 0 absolute BF is compared with CLEO’s value. Manmohan Dash, DPF/JPS-2006, 31 Oct 2006, Honolulu, Hawaii 31