Status and future perspectives on Vcs and Vcd

Status and future perspectives on Vcs and Vcd Marina Artuso Syracuse University Marina Artuso WG 1 CKM 2006 1

Motivation: unitarity constraints weak eigenstates VCKM mass eigenstates Wolfenstein parameterization To l 3 in real part & l 5 in im. part • CKM unitary described by 4 parameters (3 real, 1 imaginary: e. g. A, l, r, h), but each quark mixing is in principle measurable highly constrained system • This talk focuses on unitary test on the second row Marina Artuso WG 1 CKM 2006 2

Vcs and Vcd from charm semileptonic decays In D rest frame l Squared 4 momentum transfer Vcq D W+ e+ K, p l Received a lot of attention in recent years because of developments in lattice QCD (see R. Van de Water presentation) Pseudoscalar hadronic final states preferred because they are stable to strong decay • We measure: Theory input Marina Artuso WG 1 CKM 2006 3

Two approaches l Assuming Vcs and Vcd known (Stone’s talk) • D K(K*)ln , D pln determine form factor shapes & distinguish among models + test lattice QCD predictions (see S. Stone talk, WG 2/3 joint session) • Note that lattice checks comparing semileptonic ff & f. D can be done independently of knowledge of CKM parameters l Assuming lattice predictions OK (this talk) • measurements of Vcd & Vcs Marina Artuso WG 1 CKM 2006 4

Experimental methods §DD production at threshold: used by Mark III, and more recently by CLEO-c and BES-II. §Unique event properties ØOnly DD not DDx produced §Large cross sections: World Ave s(Do. Do) = 3. 72 0. 09 nb s(D+D-) = 2. 82 0. 09 nb Continuum ~14. 5 nb § Ease of B measurements using "double tags“ p §B-factories (e+e-) + fixed target & collider experiments at hadron (ps) machines §D displaced vertex e+ §D*+ p+D 0 tag Marina Artuso WG 1 CKM 2006 K D 0 e 5

Theoretical Tools • § 1. 2. Lattice QCD Theory (unquenched QCD), still has moderate systematic errors; however theoretical accuracy can be improved in a controlled fashion. • QCD Sum Rules Equating phenomenological and theoretical spectral functions; Determination of theoretical spectral functions by calculating two or three-point correlators in perturbative QCD, including corrections from the OPE Many parameters, difficult to improve their accuracy in a systematic fashion. • l l Phenomenological models Important contributions to our understanding of charm decays No way to improve these predictions in any systematic way Marina Artuso WG 1 CKM 2006 6

Lattice results for D K(p) e ne semileptonic decays l l two form factors are needed to describe the vector current matrix element <P|Vm|D> : f+(q 2) and f 0(q 2), (only f+(q 2) needed if ml negligible) Lattice QCD calculates both f+ and f 0, since they can be fit simultaneously imposing the constraint f+(0)= f 0(0) Fermilab-MILC-HPQCD reported results using 2+1 flavors of improved staggered quark to implement non-quenched f. f. calculation Dominant systematic error from heavy quark discretization (7% of the overall 10% uncertainty) Marina Artuso WG 1 CKM 2006 7

A snapshot of theoretical predictions l Other predictions are available from quenched lattice QCD calculations, QCD sum rules and form factor models f+(0)[D p] 0. 64(3)(6) Ref. Nf=2+1 f+(0)[D K] 0. 73(3)(7) Nf=0 0. 71(8) 0. 62(7) Average reported in Aubin et al. , PRL 94, 011601 (2005) hep-ph/0512039 QCD sum rules 0. 79(14)(8) 0. 61(11) Khodjamirian, hep -ph/0306253 with updated inputs Marina Artuso WG 1 CKM 2006 8

CLEO-c results – tagged analysis 281 pb-1 310 K D+ 160 K D 0 K- K+ e+ Signal events: U = Emiss– |Pmiss| = 0 Tag allows to determine signal D 0 momentum Signal semileptonic decay Marina Artuso WG 1 CKM 2006 9

CLEO-c results untagged analysis l l Unspecified other side D decay, collect other showers and tracks Use neutrino reconstruction like B p/r ln Higher statistical accuracy, worse systematic error Samples overlap Marina Artuso WG 1 CKM 2006 10

D K, p en Branching Fractions D → K e+ ν FNAL-MILCHPQCD D → π e+ ν FNAL-MILCHPQCD preliminary FNAL-MILC-HPQCD precision lags experiment. Marina Artuso WG 1 CKM 2006 11

Form-Factor Parameterizations l In general l Modified Pole l Series Expansion Hill & Becher, Phys. Lett. B 633, 61 (2006) Marina Artuso WG 1 CKM 2006 12

Form factor data and FNAL-MILCHPQCD predictions CLEO-c preliminary-tagged l l FNAL-MILC-HPQCD calculation uses modified pole model to fit form factor from “measured”points [PRL 94, 011601 (2005)] FF predictions: Fnal-MILC-HPQCD • D Ken f+(0)=0. 73± 0. 07 a=0. 50± 0. 04± 0. 07 • D pen Fnal-MILC-HPQCD f+(0)=0. 64± 0. 03± 0. 06 a=0. 44± 0. 07 Marina Artuso WG 1 CKM 2006 13

Belle, Ba. Bar, FOCUS D K, pℓn form factors data + FOCUS published Kℓn BELLE: PRL 97, 061804 (2006) [hep-ex/0604049] Ba. Bar: hep-ex/0607077 FOCUS: PLB 607, 233 (2005) [hep-ex/0410037] Belle, 282 fb-1, fully reconstructed events, excellent q 2 resolution Unquenched LQCD Quenched LQCD Simple pole model Aubin et al. , PRL 94, 011601 (2005) Abada et al. , Nucl. Phys B 619, 565 (2001) Belle ~2. 5 k signal events Kℓn Belle FOCUS: ~13 k events 75 fb-1 FNAL MILC HPQCD: Aubin et al. , PRL 94, 011601 (2005) pℓn 232 signal events Marina Artuso WG 1 CKM 2006 q 2 (Ge. V 2) 14

Summary of lattice-experiment comparison D 0 K-e+ne D 0 p-e+ne Assuming Vcd=0. 2238 Assuming Vcs=0. 9745 FNAL. MILCHPQCD Belle . . Belle FNAL. MILCHPQCD Marina Artuso WG 1 CKM 2006 15

Using semileptonic width and form factors l Using the preliminary CLEO-c semileptonic widths G(D Kene) =(8. 7 0. 16) x 10 -2 ps-1 and G(D pene)= (0. 76 0. 03)x 10 -2 ps-1 and FNALMILC-HRQCD G(D Kene)/|Vcs|2 and G(D pene)/|Vcd|2 • Vcs=0. 966 ± 0. 008 [exp] ± 0. 093 [th] • Vcd=0. 225 ± 0. 004 [exp] ± 0. 022 [th] l Relies on correct shape and normalization of the form factors Marina Artuso WG 1 CKM 2006 16

CLEO-c untagged form factor analysis Combine measured |Vcx|f+ (0) with FNAL-MILC-HPQCD value for f+(0)PRL 94, 011601 (2005) Decay Mode |Vcx| c (stat) ± (sys) ± (theory) PDG 06 Value D 0 K ± e 1. 006 ± 0. 007 ± 0. 013 ± 0. 103 0. 957 ± 0. 017 ± 0. 093 (charm exclusive sl width, smaller data sample) D 0 ± e 0. 221 ± 0. 013 ± 0. 004 ± 0. 028 0. 230 ± 0. 011 (n-n interactions, later) D± K 0 e 0. 984 ± 0. 042 ± 0. 017 ± 0. 101 0. 957 ± 0. 017 ± 0. 093 D± 0 e 0. 235 ± 0. 016 ± 0. 006 ± 0. 029 0. 230 ± 0. 011 Marina Artuso WG 1 CKM 2006 17

A check on theory CLEO-c results based on 281 pb-1 (tagged) BR(D mn)=(4. 4 0. 7 0. 1) 10 -4 BR(D en) <2. 4 10 -5 50 signal candidates, 2. 8 bgd BR(D tn) <3. 1 10 -3 (more details on Stone’s talk) Ratio D+→ +n does not depend upon Vcd Missing mass 2 = (Ebeam-Emu)2 -(p. D-pm)2 (Ge. V)2 Marina Artuso WG 1 CKM 2006 18

Comparison with FNAL-MILCHPQCD predictions l . Data and theory are consistent within error Marina Artuso WG 1 CKM 2006 19

W branching ratios and Vcs l LEP-2 performed measurements sensitive to |Vcs| from on-shell W± decays: Using: |Vud|2+|Vus|2+|Vub|2+|Vcd|2+ |Vcb|2=1. 0476 ± 0. 0074 l l |Vcs| =0. 976 ± 0. 014 Error includes contributions from uncertainties on as and other CKM parameters, but is dominated by ± 0. 013 from the measurements of the W branching fractions l DELPHI tagged W+ cs analysis |Vcs| =0. 94 +0. 32 ± 0. 014 -0. 26 Marina Artuso WG 1 CKM 2006 20

Neutrino/anti-neutrino interactions and Vcd l Method: n+d c+m |Vcd|2 Bm [average semileptonic branching ratio of charm] n - |Vcd|2 <|Vcd|2 Bm>=(0. 463 0. 034)x 10 -2 Bm= 0. 0873 0. 0052 [pdg 2006] c d 0. 011 (5% accuracy) |Vcd|=0. 230 Marina Artuso WG 1 CKM 2006 21

Summary l Best Vcs direct determination, using Gexp(Ken) and lattice form factors: Tagged fit Untagged fit l l Best Vcd direct determination from n, n interactions With these inputs and |Vcb|=(41. 6 0. 6)x 10 -3 [pdg 2006] unitarity constraint on the 2 nd row gives: Error dominated by theoretical uncertainty in |Vcs| Marina Artuso WG 1 CKM 2006 22

Future prospects l l CLEO-c expects to accumulate 750 pb-1 at the y(3770) increased statistics will allow to pin down shape of form factors and constrain theoretical calculations Further refinements of lattice calculations (now dominating errors) are under way Goal to determine |Vcs| and |Vcd| down to a few % accuracy Marina Artuso WG 1 CKM 2006 23