Wiener Charm-Physik bei BELLE Laurenz Widhalm HEPHY Wien Belle in a nutshell Absolute Formfaktoren von semileptonischen D0-Zerfällen Absolute Formfaktoren von semileptonischen Ds-Zerfällen Inklusive & exklusive Verzweigungsverhältnisse bei D0-Zerfällen located at KEK / Japan KEKB Collider B-Factory at (4s) resonance peak luminosity 16.270 1/nb/s integrated luminosity 600 1/fb (as of June 2006; 280 1/fb used in this analysis) main physics goal: observation of CPV in B meson Decays e- 8GeV e+ 3.5GeV bg = 0.425 Laurenz Widhalm HEPHY Wien Belle Collaboration KEK 高エネルギ

I. Bigi @ Charm2006

Semileptonic D0 Decays q² single form factor fD(q2) calculable in LQCD, but needs checking from data D-System ideal for experimental input results can be applied in B-physics (extraction of CKM parameters)

Method of Reconstruction (Event Topology) additional primary mesons  IP 3.5 GeV e+ e- 8 GeV p K recoil n D0 pslow e/µ- K/p+ D*- „inverse“ fits D* p g mass-constrained vertex fits D p p note: all possible combinations tried in parallel cuts after complete reconstruction equal weight for remaining combinations  no event loss due to particle exchanges! Ktag p  tag side signal side 

result D0 Signal and Background* after cuts background signal * from decays without a D0 , or combinatorial background control region signal region same sign Ktag/pslow s=0.0006 GeV! signal D0 invariant mass result (282 fb-1 of BELLE data) yield after cuts 95250 background 38789 signal charge correlation signal subtraction stats bkg sample 56461 ± 309stat ± 776syst ± 233syst ± 194syst opposite sign Ktag/pslow note: data used for bkg subtraction, MC shown only for comparison MC charm (D°) MC B0 data (normalized) MC charm, no D° MC uds MC B± MC wrong sign D°

Summary of Signal / Background Decomposition D0  Ken remaining signal D0  pen data data fake-D0 bkg D0  Kmn D0  pmn hadronic bkg data Kln bkg data MC K*/rln bkg mn² / GeV² Results (282 fb-1 of data) Ken Kmn pen pmn signal events 1318 ± 37stat ± 7syst 1249 ± 37stat ± 25syst 126 ± 12stat ± 3syst 106 ± 12stat ± 6syst fake D0 bkg 12.6 ± 2.2 12.2 ± 4.8 12.3 ± 2.2 12.5 ± 4.5 semileptonic bkg* 6.7 ± 2.6 10.0 ± 2.5 11.7 ± 1.2 12.6 ± 1.9 hadronic bkg** 11.9 ± 5.6 62.1 ± 23.9 1.8 ± 0.7 9.7 ± 3.7 * error dominated by MC statistics ** error dominated by fit errors & bias special bkg sample

Absolute Branching Ratios ratio to total number of recoil D0 tags efficiency correction corrected for bias due to differences data/MC (1.9%±3.9%) BRs (%) this analysis PDG (2005) CLEO-c (hep-ex/0505035) K-e+n 3.45 ± 0.10stat ± 0.19syst 3.62 ± 0.16 3.44 ± 0.10stat ± 0.10syst K-m+n 3.45 ± 0.10stat ± 0.21syst 3.20 ± 0.17 p-e+n 0.279 ± 0.027stat ± 0.016syst 0.311 ± 0.030 0.262 ± 0.025stat ± 0.008syst p-m+n 0.231 ± 0.026stat ± 0.019syst 0.24 ± 0.04

 no unfolding necessary! Form Factors – q² distribution D0  Ken D0  pen signal q² non-D bkg hadronic bkg semileptonic bkg s(q²) = 0.0145 GeV²/c² (width of red line)  no unfolding necessary! D0  Kmn D0  pmn background shapes from data

(poles fixed at theo. values) Form Factors – Comparison with Models modified pole model D0  Kln lattice calculation ISGW2 model fit results simple pole pole mass (GeV) Kln 1.82 ± 0.04stat ± 0.03syst pln 1.97 ± 0.08stat ± 0.04syst D0  pln modified pole (poles fixed at theo. values) f+(0) Kln 0.695 ± 0.007stat ± 0.022syst pln 0.624 ± 0.020stat ± 0.030syst a Kln 0.52 ± 0.08stat ± 0.06syst pln 0.10 ± 0.21stat ± 0.10syst

Semileptonic Ds Decays PDG:Ds

... Reconstruction Method for Ds  3.5 GeV e+ e- 8 GeV p p K g g D Ds- additional primary particles IP  3.5 GeV e+ e- 8 GeV Ds*- recoil p p K ... g recoil g mass-constrained vertex fits D „inverse“ fits Ds- p p recoil µ- n Ktag p  tag side signal side 

DATA (Exp7-Exp49) Ds in BELLE data ~20000 events measurements of inclusive & exclusive channels planned reconstruction of decay products of Ds, e.g. muon and neutrino of Ds  mn or Ds F m n will further reduce ambiguity Ds invariant mass / GeV

inclusive & exclusive BRs of D0 KK-Spectrum for D0(KK) X Missing Mass for D0(KK) X M(K+K-) M(X) D0 F X K0 D0K+K- D0K+K-K0 D0K+K-p0 p0 p misidentified as kaon p misidentified as kaon

Summary & Outlook events searched in e+e-  D(*)D*cX and e+e-  DDs*KX (X=np/K/g) new full-reconstruction-recoil method absolute D0 BRs of better accuracy than previous experiments, in good agreement with recent CLEO measurements high q² resolution, no unfolding necessary absolute multi-bin measurement of f+(q²) measured form factor in good agreement with theoretical predictions and other experiments new Ds analysis will yield inclusive BR measurements and better knowledge of Ds form factor improvements of various inclusive and exclusive BRs of D0  (KK)X (future: (Kp)X, (pp)X) Phys.Rev.Lett.97:061804,2006 (hep-ex/0604049) Laurenz.Widhalm@oeaw.ac.at

Spares

Best Candidate Selection (MC check) Ds invariant mass Ds invariant mass no best candidate selection largest “slow” pion energy taken signal / no ambiguity signal / several associations signal / lost because wrong candidate selected background

additional primary mesons Method of Reconstruction (Event Topology) tag side: reconstruction & fit of D0,±  Kp, K2p, K3p reconstruction & fit of D*0,±  Dp, Dg use either D or D* as primary meson signal side: reconstruction & fit of inclusive D*0,± via recoil from e+e-  D(*) D*np/K reconstruction & fit of inclusive D0 via recoil from D*  Dp reconstruction & fit of neutrino via recoil from D  mpn additional primary mesons e+ e- p K ( ) D* D* D p g D p p p K p e/µ p n tag signal

Method of Reconstruction (Event Topology) D*-sig m/GeV m/GeV D*+tag D*0 tag D0sig m/GeV

List of Cuts unstable particle selection: stable particle selection: gammas: p > 40 MeV charged tracks (general): p > 100 MeV trk_fit.nhits(3) > 0 dr < 2 cm, dz < 4 cm electron: p > 500 MeV eid.prob(3,-1,5) > 0.9 muon: prerejection != 1 Muon_likelihood > 0.9 kaon / pion: atc_pid (3,1,5,3,2) prob*(1-prob_e-prob_mu) > 0.5 for meson in hlnu: > 0.9 List of Cuts unstable particle selection: pi0: PDG mass ± 10 MeV fit CL > 0.1 K0: only via decay pi+pi- PDG mass ± 25 MeV D_tag: channels Knpi, n=1-3 PDG mass ± 20 MeV D*_tag: channel Dpi, Dg PDG mass ± 5 MeV mass/vertex fit CL > 0 D*_signal: via recoil from D*_tag+n pi/K, n=0-5 mass/vertex fit CL > 0.001 D_signal: via recoil from D*_signal  Dpi n: via recoil from D_signal  hlnu |m²| < 0.05 GeV² additional Klnu / pilnu cuts: E_leftover < 700 MeV, no leftover charge E_nu > 100 MeV right charges of slow pions & lepton

Bias by mass-constrained Fits on Background? no real D0   with real D0 after fit of D* before fit of D*  D0 invariant mass very sharp mass peak after fit no bias on background 

D0 Signal and Background* * from decays without a D0 , or combinatorial background cuts confidence level of all mass-constrained vertex fits >0.1% (released on D0 fit for righthand plot) right charge correlation between slow pion and tag side kaon (right sign, RS) control region same sign Ktag/pslow signal D0 invariant mass procedure to measure background: select wrong charge correlation data (WS) to get shape of background correct for small WS signal component normalize to RS data in region 1.84-1.85 GeV signal region opposite sign Ktag/pslow charm MC B0 MC data (normalized) charm, no D° uds MC result (282 fb-1 of BELLE data) yield selected D0 events 95250 subtracted background 38789 signal 56461 ± 309stat ± 830syst B± MC wrong sign true D° systematics breakdown events charge correlation RS/WS 776 WS signal subtraction 233 statistics of WS sample 194

Measurement of Semileptonic Background (for pln)* procedure to measure background: 1. crosstalk from Kln: prepare special background sample, with K intentionally misidentified as p normalize to standard Kln sample then reweight the sample using known** efficiencies / fake rates (in p,) 2. background from vector mesons: get shapes for K*ln and rln from MC (simulated ratio K*/r from PDG) normalize to data in region m²n > 0.3 GeV² recoil neutrino mass control region for K*/r bkg measurement D0  pln signal region data non-D° bkg (measured as described previously) * background for Kln is very small, and is handled the same way ** measured independently in data measured bkg from Kln measured bkg from K*ln measured bkg from rln

Measurement of Hadronic Background (for pmn)* procedure to measure background: prepare special background samples, with K(p) intentionally misidentified as m (subtract fake D0 background in these samples with the method described above) separate into same sign (SS) and opposite sign (OS) samples, with respect to the charges of the lepton and the slow pion semileptonic channels are highly suppressed in OS  clean sample of hadronic background perform a 2-parameter fit in the standard OS sample, using the shapes from the OS background samples for K and p, to measure the effective fake rates then apply these fake rates in the background SS sample to obtain the backgrounds in the signal sample same sign SS signal: D*  D0p+  p-m+n SS both signs D*  D0p+  p-p+p0/K0 p-m± n opposite sign OS D*  D0p+  K-p+p0 p+m-n SS OS OS D*  D0p+  K-p+p0/K0 p-m+ n * significant background only for this channel; other channels are handled likewise

Fit of Hadronic Background (for pmn)* D0  pmn comparison with MC SS MC true composition use result of fit here  green = particle seen in recoil mass D0  p-p+p0 D0  K-p+p0 D0  K0p-p+ fit in this sample  OS signal region bkg from misidentified kaons bkg from Kmn bkg from misidentified pions bkg from K*/rmn * background for pen and Kln are much smaller remaining events in signal region fake-D0 bkg

Form Factors - Theory    f+(q²) = 1-q²/m² in principle, two form factors f+(q²) and f-(q²) kinematically only f+(q²) relevant, f-(q²) suppressed by ml² three different models that are frequently discussed in literature: simple pole f+(q²) = 1-q²/m²   f+(0) m......pole mass = m D*s  2.11 GeV (Kln) = m D*  2.01 GeV (pln) modified pole f+ (q²) = (1-q²/m²) (1-aq²/m²)  0.50 (Kln)  atheor. G. Armoros, S. Noguera, J. Portoles, Eur. Ph. J. C27, 243 (2003)  0.44 (pln) ISGW2 f+ (q²) = (1-a(q²-q²max))² N. Isgur and D. Scora, Phys. Lett. B 592 1(2004) 

Measured Absolute Form Factors as function of q² D0  Ken D0  pen D0  Kmn D0  pmn extracted by dividing q² distribution by kinematical factor no unfolding necessary due to very good q² resolution