{CLEO-c Charm Leptonic & Semileptonic Decays}

Transcription

1 Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} Chul Su Park University of Rochester (for the CLEO Collaboration) March 5, 8

2 Charm Leptonic and Semileptonic ecays Careful studies of charm leptonic and semileptonic decays calibrates theory, so more reliable values of V td, V b, can be obtained from B factories. Leptonic decays b tv td d B W W + B d V t b td c + +, s ƒ (s) V cd(s) W + l + Rate ƒ B V td experiment LQC Rate ƒ (s) V cd(s) LQC predicts ƒ B /ƒ and ƒ B /ƒ Bs w/ small errors precise ƒ gives precise ƒ B and V td ƒ /ƒ s checks ƒ B /ƒ Bs and allows precise V td / V ts d( s) l Semileptonic decays c W + V cd ƒ(q ) d l + l π known to <1% from the CKM unitarity Rate V cd ƒ + (q ) Test theory calculations of ƒ + (q ) in the system and apply them to the B system for V b Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 / 4

3 CLEO-c Open Charm Program Precision measurements of benchmark branching fractions of, +, and s., i.e., those decay modes used by B factories and hadron colliders : K π +, + K π + π +, s + π + K + K, and others. Measurements to test, calibrate, validate Lattice QC calculations, other calculations of strong interaction effects. +, s + l + l, exclusive semileptonic decays. General-purpose symmetric detector Particle I...(dE/d,Ring Imaging Cherenkov)...excellent in our momentum region Tracking: δp/p=.6% at 1 GeV CsI calorimeter:...δe/e 5% at 1 MeV CLEO-c SC Quadrupole Pylon SC Quadrupoles Rare Earth Quadrupole Solenoid Coil Barrel Calorimeter 314- Ring Imaging Cherenkov etector rift Chamber Inner rift Chamber / Beampipe Endcap Calorimeter Iron Polepiece Barrel Muon Chambers Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 3 / 4 Magnet Iron

4 ata Samples R J/ψ Mark I Mark I + LGW Mark II PLUTO ASP Crystal Ball BES ψ(s) s s ψ 377 ψ 44 ψ 416 PG 6 ψ 4415 c : 8 pb 1 (56 & 81 pb 1 in this talk); 81 pb s 417 : 314 pb 1 (will double the sample) 314 pb s s Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 4 / 4

5 Charm at ψ(377) K π + π K π + π + π - K π + - K π + π 1 ψ(377) : just above threshold, no additional particles ΔE=E E beam M bc = E beam p tagging efficiency: 1% + 15% Clean experimental environment ( low multiplicity & -tagging) K π+ S K π + π + π - S M bc (GeV/c ) + KS π + π K K π K π + π π 5 1 K π + π - S K S π M bc (GeV/c ) Absolute branching fraction measurement ( tagging) CLEO-c has largest data set at K π + π + π - K π + π - S + - K K π Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 5 / 4

6 Absolute Branching Fractions ψ(377) K + π K e + e - K e + N SL 7 S/N 3/1 π - e + N SL 7 S/N 4/1 Semileptonic event can be fully reconstructed (except neutrino) B( Xe + e )= N SL/ε SL N tag K e + e U=E miss p miss (GeV) K π + π Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 6 / 4

7 Introduction : Leptonic ecays Q V Qq +, + s, B + ƒ P W + q l + l (P Q q l + l )= G F V Qq ƒ P m Q q m 8π l 1 m l m Q q Measure rates to extract decay constant ƒ P (V Qq ). Check lattice calculations of decay constants. ƒ at CLEO-c and(ƒ B /ƒ ) LQC ƒ B for precise V td. ƒ /ƒ s checks(ƒ B /ƒ Bs ) LQC for V td / V ts. Sensitive to new physics, e.g. H + can mediate. Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 7 / 4

8 + μ + μ Use 158k tags (81 pb Require only one additional track, μ + Reject event if substantial energy in calorimeter Compute missing mass Events /.1 GeV signal events.8 estimated background Result: Phys. Rev. Lett. 95, 5181 (5) K L π+.5.5 MM (GeV ) B( + μ + μ )=(4.4± ) 1 4 ƒ =(.6± ) MeV (using V cd =.38) Unquenched LQC ƒ +=(1±3±17) MeV, Exp/Theory agree to 1%. Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 8 / 4

9 s + μ + μ s + τ + τ (τ + π + τ ) Case Region (GeV ) Signal Background A -.5<MM < ±1.4 B.5<MM <. 31.5±1.1 C -.5<MM <. 5 3.±1.3 Sum -.5<MM < ± pb 417 e + e s s Find a s (8 tag modes used), 31k tag candidates Nowincludeaγ,lookingfor s γ s decay γ Calculate mass recoiling against s - tag+γ, to find events with detected decay γ Select events with only one additional track, oppositely charged, consistent with μ or π Reject events with energetic neutral energy clusters Calculate missing mass. Results : Phys. Rev. Lett. 99, 718 (7) A:... B( s + μ + μ )=(.594±.66±.31)% B and C:... B( s + τ + τ )=(8.±1.3±.4)% A, B, and C: by summing all cases, w/ SM τ/μ ratio... B eff ( s + μ + μ )=(.638±.59±.33)%... ƒ s =(74±13±7) MeV ( V cs =.9738) Track consistent with μ + (E CC <3 MeV) mostly s + μ + μ (accepts 99% of μ and 6% of π) A B C Track consistent with e + Track consistent with π + (E CC >3 MeV) mostly s + τ + (π + τ ) τ (accepts 1% of μ and 4% of π) Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 9 / 4

10 s + τ + τ (τ + e + e τ ) 98 pb 417 e + e s s Finda s (3cleanesttagmodesused), 13k tag candidates Find an electron on the other side Require no other charged tracks on the other side Plot the energy in the calorimeter, not due to tag side or the electron E extra <4 MeV is the signal region Extrapolate background from s semileptonic decays (mainly + s ηe + e ) from region above 4 MeV + s K L e+ e background from s + K S e+ e measurement, B( + s K S e+ e )=(.14±.6±.1)% Backgroundis 1%ofyieldinsignal region Result : arxiv: B( s + τ + τ )=(6.17±.71±.34)% This is the most precise determination.. of B( s + τ + τ ) ƒ s =(73±16±8)MeV( V cs =.9738) E extra <4 MeV N T =13±11.3 N S =11.6±11.5 N B =1.4±1. Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 1 / 4

11 ƒ s & ƒ s /ƒ Combining s + μ + μ, s + τ + (π + τ ) τ, and s + τ + (e + e τ ) τ : Phys. Rev. Lett. 99, 718 (7); arxiv: ƒ s =(74±1±5)MeV Using ƒ =(.6± ) MeV ƒ s ƒ =1.3±.1±.3 CLEO-c is the most precise result to date for both ƒ and ƒ s ([94±7] MeV, PG 6). R= ( s + τ + τ ) ( s + μ + μ ) =11.±1.4±.6 (consistent with lepton universality, SM 9.7). Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 11 / 4

12 Comparison with Theory CLEO ƒ is consistent with LQC calculations. CLEO ƒ s is 3σ above the most recent & precise LQC calculation (HPQC) this discrepancy needs to be studied, LQC or Exp error? conflicts with the suppression expected from a HM (Phys. Rev. 75, 754 (7) ) there is new physics that interferes constructively with the SM? HPQC[arXiv:76.176] Fermilab/MILC[Phys. Rev. Lett. 95, 1 (5)] BaBar[Phys. Rev. Lett. 98, (7)] Comparing measured ƒ s /ƒ with HPQC M H +/t nβ>. GeV at 9% C.L. Using HPQC ƒ s /ƒ V cd / V cs =.17±.19 exp ±. theory Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 1 / 4

13 Introduction : Semileptonic ecays Cleanest (and simplest, both experimentally & theoretically) way to determine magnitudes of CKM elements d V dq cs(d) ƒ K(π) + (q ) Assuming theoretical form factor determine V cs and V cd Assuming V cs and V cd we can check theoretical calculations of the form factors Test theory calculations (e.g. LQC) of ƒ + (q ) in the system and apply them to the B system, e.g. for V b. K(π) l π l Experiment HQS Theory (LQC) Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 13 / 4 B π l

14 Inclusive Semileptonic ecays Historically : interesting due tothelargedifferencein vs + lifetimes (spectator model inadequate) Inclusive vs Sum of Exclusive : room for new modes? Mode Branching Fraction Xe + e (6.46±.17±.13)% Sum of B SL ( ) (6.1±.±.)% + Xe + e (16.13±.±.33)% Sum of B SL ( + ) (15.1±.5±.5)% [ Phys. Rev. Lett. 97, 5181 (6)] 8% extrapolation below momentum cutoff Consistent with isospin symmetry : the lepton cannot interact strongly with the final-state hadrons and the two mesons differ only in the isospin of the light quark SL + SL = B SL +/τ + B SL /τ =.985±.8±.15 Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 14 / 4

15 First Observations [Phys. Rev. Lett. 99, (7)] + η(γγ)e + e [Preliminary] 3.7±6.7 3 CBall_mean =.3 ±.18 CBall_sigma HHHHHHH =.15 ±.16 5 CBall_yield = 131 ± 13 cmbn_yield = 13 ± ρ e + e [Preliminary] 131±13 K π + π e + e 1 signal candidates on background 4σ significance η(π + π π )e + e [Preliminary] 13.3±4. CBall_mean = -.41 ±.31 1 CBall_sigma HHHHHHH =.134 ±.4 CBall_yield = 37.3 ± poly_yield = 1.7 ± ωe + e [Preliminary] 37.3±6.7 K 1 (17)e+ e 8 signal consistent with K 1 (17) K π + π on 1 background U=E miss p miss (GeV) U=E miss p miss (GeV) Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 15 / 4

16 K(π)e (1) Tagged Analysis : () Untagged Analysis :...neutrino reconstruction [arxiv:71.998] [Preliminary] π - e + e - K e + e 699±8 6796±84 135± ±13 + π e + e + K e + S e 95± 91±55 447±9 5846± U = E miss - P miss (GeV) The untagged analysis has larger signal yields but larger backgrounds and systematic uncertainties. Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 16 / 4

17 Branching Fraction Summary - + π e - ρ - K(17) + X e ρ e + K K *- K π K * K e *- (K ω e η e + (K S e + e + e + S + + X e (K π + ) e π ) e + π - ) e e + + PG 4 * CLEO-c (81 pb BES -1 1 * K * e + branching fractions are for 56/pb -1 ) L (pb 1 ) B( ) SL (%) B( + ) SL (%) K e + e K e + e 81 tagged 3.58±.5± ±.17±. 81 -recon 3.56±.3± ±.13±.3 K (89) e + e K (89) e + e 56.16±.15± ±.7±.3 π e + e π e + e 81 tagged.39±.1±.6.397±.7± recon.99±.11±.9.373±.±.13 ρ e + e ρ e + e 81 tagged.156±.16±.9.3±.±.1 ωe + e 81 tagged.149 ±.7 ±.5 ηe + e 81 tagged.133 ±. ±.6 K 1 (17)e+ e 81 tagged ±.6±.7 exclusive 6.8±.16 stat 15.33±.4 stat Xe + e Xe + e 81 tagged 6.46±.17± ±.± tagged η e + e < tagged ϕe + e < pb 1 numbers are preliminary, except Xe, K (17)e, and K/πe (-recon). 1 4% overlap, do not average tagged/-recon K/ πe. Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 17 / 4

18 Semileptonic ecay Form Factor q =(p p X ) =m +m X m E X c ( d) V cs(d) s(d) X ( d) ƒ(q ) Amplitude factorizes M( Xl + l ) = G F V cs(d) L μh μ Hadronic currents : in the limit m l P P l + l : single form factor, H μ =ƒ + (q )(p P +p P ) μ (gold-plated for both theory and experiment) e.g. semileptonic decays to a pseudoscalar can be written as d ( Ke e) dq = G F V cs p 3 K 4π 3 ƒ + (q ). The messy hadronic physics is contained in the form factor. The full test of LQC is its ability to calculate ƒ(q ), both the shape vs q, and the absolute value. Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 18 / 4

19 Form Factor : parametrizations In general : ƒ + (q )= ƒ +() 1 α 1 1 q /m pole + N k=1 Single pole : ƒ + (q )= ƒ +() 1 q /m pole Modified pole : ƒ + (q ƒ )= + () (1 q /m pole )(1 αq /m pole ) (allows for additional poles). ρ k 1 1 q γ k m pole Series expansion : [T. Becher and R. J. Hill, Phys. Lett. B 633, 61 (6)] with z(q,t )= ƒ + (q )= 1 P(q )ϕ(q,t ) k= k(t )[z(q,t )] k, t + q t+ t t+ q + t+ t, t ± (M ±m P ), and P(q ) 1 ( π) or z(q,m s ) ( K). With current CLEO-c data we only resolve the first 3 terms in the series expansion. Experiment probes both the form factor magnitude & parametrization. Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 19 / 4

20 Ke : high statistics test of shape & absolute normalization of ƒ + (q ) ) f + (q.5 + K e e 1.5 LQC mean LQC Statistical LQC Systematic CLEO-c (tag) CLEO-c (no tag) BELLE BaBar 1 FNAL/MILC/HPQC (Curve courtesy Andreas Kronfeld) FOCUS (Param) CLEO III Belle (6) BABAR (7) LQC CLEO-c (tag) CLEO-c (no tag) α K e.5 Assuming V cs = q (GeV )/M Modified pole model used for comparison : ƒ + (q ƒ )= + () (1 q /m pole )(1 αq /m pole ) Shape parameter: CLEO-c prefers smaller value Normalization: experiment (%) consistent with LQC (1%) * s LQC (Abada) QC SR (Ball) LCSR (KRWWY) LCSR (WWZ) Quark Model LQC (FNAL-MILC-HPQC) -1 Belle (8 fb ) -1 BaBar (75 fb ) -1 CLEO-c (tag, 81 pb ) -1 CLEO-c (no tag, 81 pb ) CLEO-c (tag) Preliminary CLEO-c (no tag) arxiv: Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 / 4 K f+ ()

21 πe : high statistics test of shape & absolute normalization of ƒ + (q ) ) f + (q π e e Fit to Quenched LQC (Abada et al.) Quenched LQC (Abada et al.) CLEO-c (tag) CLEO-c (no tag) BELLE π e + e 1 3 q (GeV Modified pole model used for comparison : ƒ + (q ƒ )= + () (1 q /m pole )(1 αq /m pole ) Shape parameter: experiments compatible with LQC Normalization: experiment (4%) consistent with LQC (1%) CLEO-c (tag) Preliminary CLEO-c (no tag) arxiv: Assuming V cd =.38±.9 ) Belle (6) CLEO-c (tag) CLEO-c (no tag) α π e LQC (Abada) QC SR (Ball) LCSR (WWZ) Quark Model Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 1 / 4 CLEO III LQC LCSR (KRWWY) LQC (FNAL-MILC-HPQC) -1 Belle (8 fb ) -1 CLEO-c (tag, 81 pb ) CLEO-c (no tag, 81 pb FNAL/MILC/HPQC -1 ) π f+ ()

22 Form Factor : Pe which parametrization? [arxiv:71.1] We use the model independent Becher-Hill series parametrization for V c (determine ƒ + () V c then use theory value of ƒ + ()). Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 / 4

23 V cs & V cd Results PG Γ (Ke) LEP W cs BESII Γ (Ke) CLEO-c (tagged) CLEO-c (untagged).5 1 V cs PG/HF CLEO-c (tagged) CLEO-c (untagged) Combined measured V c ƒ + () values using Becher-Hill parameterization with FNAL/MILC/HPQC for ƒ + (). CLEO-c : the most precise direct determination of V cs σ( V cs )/ V cs 1.5% (exp) 1% (theory) CLEO-c V cs (tagged) 1.14 ±.13 ±.9 ±.16 (untagged) 1.15 ±.1 ±.11 ±.16 stat syst theory CLEO-c : σ( V cd )/ V cd 4.5% (exp) 1% (theory) N remains most precise determination (for now). CLEO-c V cd (tagged).34 ±.1 ±.4 ±.4 (untagged).17 ±.9 ±.4 ±.3 stat syst theory V cd Tagged and untagged are consistent. 4% overlap, O NOT AVERAGE. CLEO-c (tag) Preliminary CLEO-c (no tag) arxiv: Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 3 / 4

24 Summary Leptonic : ƒ measured to±7.6%, statistical error dominates. ƒ s measured to±4.1%, statistical error dominates. B( + s τ + τ )/B( + s μ + μ ) consistent with theory. For ƒ s, a suggestion of a disagreement with LQC 3σ. Semileptonic : Inclusive, + semileptonic widths equal. Sum of measured exclusives almost saturates inclusives. Ke, πe form factors in general agreement with LQC. With CLEO-c full data : 8 pb & 6 pb Expect errors in ƒ & ƒ s decreased to a few % level. More stringent tests of theory for K(π)e + e form factor ƒ + () & shape. Rencontres de Moriond EW 8 {CLEO-c Charm Leptonic & Semileptonic ecays} March 5, 8 4 / 4