CHARM 2007, Cornell University, Aug. 5-8, 20071Steven Blusk, Syracuse University D Leptonic Decays near Production Threshold Steven Blusk Syracuse University

CHARM 2007, Cornell University, Aug. 5-8,CHARM 2007, Cornell University, Aug. 5-8, 2007 2007

11 Steven Blusk, Syracuse Steven Blusk, Syracuse UniversityUniversity

D Leptonic Decays D Leptonic Decays nearnear

Production ThresholdProduction Threshold

Steven BluskSteven BluskSyracuse UniversitySyracuse University

(on behalf of the CLEO Collaboration)(on behalf of the CLEO Collaboration)



Introduction: D Introduction: D ++

Partial width measurement probes the hadronic vertexPartial width measurement probes the hadronic vertex Soft-gluon effects Soft-gluon effects Non-perturbative QCD Non-perturbative QCD Decay constant, Decay constant, ffDD describes the hadronic vertex, and is proportional to the describes the hadronic vertex, and is proportional to the

wave-function overlapwave-function overlap (Prob (Prob cd(s) cd(s)W annihilation)W annihilation)

General solution (SM) for partial widthGeneral solution (SM) for partial width

_ 22+ 2 2 2

221

(P ) 1 | |8 F P P Q

Pq

mG m M Vf

M

Calculate, or measure if VQq known

(s)

or cs



Leptonic Decays in SMLeptonic Decays in SM

Measurement provides critical test of theory to Measurement provides critical test of theory to compute compute ffBB, f, fBsBs..

In a few years, we will have a precision measurement In a few years, we will have a precision measurement (~5(~5oo))of of ((33) by LHC) by LHCbb.. Expect Expect (()~5)~5oo

with 2 with 2 fbfb-1-1

Could provide signsCould provide signsof NP if of NP if measurement measurementdoesn’t coincide withdoesn’t coincide withmm(s,d)(s,d) band. band.

B B gives Vgives VububffB,B, but buthard to measurehard to measure

directly. directly.

Constraints from Vub, md, ms & B



New Physics in DNew Physics in D(s)(s) leptonic leptonic decaysdecays

Deviations from lepton universality possible if tan large Hewett [hep-ph/9505246] & Hou, PRD 48, 2342 (1993).

2 2 2 2( )

2 2 2

[1 tan ( / )( / )]

[1 ( / )]

s Dq q cHSM

Dq q c

r m m m m

R m m m

Interference between H± and W± suppresses Dsl, but NOT Dl Akeroyd, hep-ph/0308260

22 2 2+

2+ 2 2 2

1 /(P )

(P ) 1 /

P

P

m m M

m m M

HR=tan /m

Deviations of this ratio from SM value of 9.72 would signal New Physics



D and DD and Dss Landscape near Landscape near thresholdthreshold Produce DD at (3770).

No additional particles Coherent 1– state Ideal for absolute BF measurements Measurements from 281 pb-1

(Phys. Rev. Lett. 95, 251801 (2005))

Not reviewed in this talk

0.09 40.12

2.83.4

( ) (4.40 0.66 ) 10

(222.6 16.7 ) MeVD

B D

f

Ds Leptonic Decays Dedicated scan to find optimal energyfor Ds physics (see talk by B. Lang)

At Ecm = 4170 MeV (DsDs*)~0.9 nb Additional photon, ~100 MeV to contend with.



Reconstructed DReconstructed Dss “Tags” at 4170 “Tags” at 4170 MeVMeV

Leptonic analyses requireLeptonic analyses requireone one fully reconstructedfully reconstructed D Dss decay (“tag”).decay (“tag”). 8 tag modes8 tag modes

Signal region: Signal region: |M|Mrecrec-M-MDsDs| < 2.5 | < 2.5

Sidebands:Sidebands: 5.0<|M5.0<|Mrecrec-M-MDsDs| < 7.5 | < 7.5

Total # of Tags Total # of Tags

= 31,302 ± 472 (stat)= 31,302 ± 472 (stat)K*K* from KsK



Measurements of Measurements of ffDsDs

Dtag

Ds*

Ds

or

e+ e-

Dtag

Ds

Ds

or

e+ e-

Dtag

Ds

Ds

e

e+ e-

“Missing Mass” Analyses (314 pb-1)Accepted to PRD arXiv:0704.0437v2

“Missing Energy” Analysis (195 pb-1)Preliminary

Only one additional track, K± rejection using PID No additional with E>300 MeV

Use (missing) mass recoiling against (Ds*+)

Ds() from Ds*Ds() from Ds

Only one additional track, consistentwith electron hypothesis

Signal discriminant: Remaining energy in calorimeter after tag and electron are removed.



Anatomy of Missing Mass Anatomy of Missing Mass Analyses Analyses

*( )

( )cand back

stag

N NB D

N

Dtag

Ds*

Ds

or

e+ e-

Ds() from Ds

Dtag

Ds

Ds

e+ e-

Ds() from Ds*

or

* * *( ) including from decay

muon detection efficiency

# of candidates

expected background

tag s s s

cand s

back

N N D D D

N D

N



Missing Mass Analyses – Missing Mass Analyses – NNtagtag

**

Take each DTake each Dss tag and photon tag and photon candidate and compute the candidate and compute the recoil mass against (Drecoil mass against (Dss

tagtag++). ).

regardless of whether Dregardless of whether Dss++ forms D forms Dss**, ,

recoil mass peaks at M(Drecoil mass peaks at M(Dss))22

NNtagtag**= 18645±426(stat) tags= 18645±426(stat) tags, ,

after 2.5after 2.5 selection on MM* selection on MM*22..

s s

2 2*2CM D γ CM D γMM = E -E -E - p -p -p

( )( )

cand backs

N NB D

*

tagN

All 8 Modes

Dtag

Ds*

Ds

or

e+ e-

Ds() from Ds

All 8 Modes

Dtag

Ds*

Ds

or

e+ e-

Ds() from Ds

*

All 8 modes combined



Missing Mass Analyses – Signal Missing Mass Analyses – Signal SideSide

*( )

( )back

stag

NB D

N

candN

All 8 Modes

Dtag

Ds*

Ds

or

e+ e-

Ds() from Ds

All 8 Modes

Dtag

Ds*

Ds

or

e+ e-

Ds() from Ds

*

For each Ds* candidate, perform a

kinematic fit,imposing the following constraints:*

*

*

*

*

*

2 2

0

143.6 MeV

( )

2 2

s s

s s

ss

ss

s

D D

D CMD

DD

tag s

DDcmD

cm

p p

E E E

M M

M M D

M MEE

E

Two solutions for each Ds

* candidate belongs with Ds tag belongs with Ds(try both)



Missing Mass Analyses – Signal Missing Mass Analyses – Signal SideSide

All 8 Modes

Dtag

Ds*

Ds

or

e+ e-

Ds() from Ds

All 8 Modes

Dtag

Ds*

Ds

or

e+ e-

Ds() from Ds

*

s

s

22CM D γ

2

CM D γ

MM = E -E -E -E

- p -p -p -p

For each Ds* candidate, perform a

kinematic fit,imposing the following constraints:

Choose solution with lowest 2 (but no cut), and compute:

Signal Ds Signal Ds→

Two possibilities for each Ds

*

candidate belongs with Ds tag belongs with Ds(try both)

Signal MC

*

*

*

*

*

*

2 2

0

143.6 MeV

( )

2 2

s s

s s

ss

ss

s

D D

D CMD

DD

tag s

DDcmD

cm

p p

E E E

M M

M M D

M MEE

E

*( )

( )cand back

stag

N NB D

N



MMMM22 from CLEO-c Data from CLEO-c Data

Electron Sample

92 events

31 events

Return to 3 separate cases:i. Etrk

CC<300 MeV “D-like”: (~99%)

-0.05<MM2<0.05 GeV2

“D-like”: (~60%) 0.05<MM2<0.20 GeV2

ii. EtrkCC>300 MeV

“D-like”: (~40%) -0.05<MM2<0.20 GeV2

iii.Electron-like

EtrkCC > 0.3 GeV in CC

EtrkCC < 0.3 GeV in CC

25 events

*( )

( )back

stag

NB D

N

candN



Backgrounds Backgrounds Combinatoric background under Combinatoric background under

peaks:peaks: Use DUse Dss cand. mass sidebands cand. mass sidebands

DDssbackgrounds from real Dbackgrounds from real DSS decaysdecays

Signalregion

High SBregion

Low SBregion

SampleSample SignalSignal Comb. Comb. Back.Back.

(i) EtrkCC<300 MeV, “D-

like”9292 3.53.5±1.4±1.4

(ii) EtrkCC<300 MeV, “D-

like”3131 2.52.5±1.1±1.1

(iii) EtrkCC>300 MeV, “D-

like”2525 3.03.0±1.3±1.3

TotalTotal 148148 9.0 9.0 ±1.3±1.3Background BFBF

(%)(%)Etrk

CC<300 MeV,

“D-like”

EtrkCC<300 MeV,

“D-like”

DsX 00+1.8+1.8-0-0 00

DsX 1.01.0 0.030.03±0.04±0.04 0.080.08±0.03±0.03

Ds

1.51.5 0.550.55±0.22±0.22 0.640.64±0.24±0.24

Ds

1.01.0 0.370.37±0.15±0.15 00

TotalTotal 1.01.0+1.8+1.8-0.3-0.3 0.70.7±0.2±0.2

Negligible real Ds decay background to DsSince B(Ds ) <1.1x10-3 @ 90% CL

*( )

( )cand

stag

NB D

N

backN



Branching fractionsBranching fractions

[ ( ; )( ) ]ag st sN N BB D D

Ntag =18645±426±1081 = efficiency for reconstructing = 80.1% = efficiency for ECC<300 MeV + |MM2|<50 MeV = 91.4% = efficiency for ECC<300 MeV(60%) + |MM2|<50 MeV(13%) = 13.2%N = 92 – (3.5±1.4) = 88.5±9.7

B(DS+→+(0.597±0.067±0.039)%

B(DS+→+

B(DS+→+

Type (i)Type (i) Type (ii)Type (ii)

NNcandcand 3131 2525

NNbackback 3.53.5+1.7+1.7-1.1-1.1 5.15.1±±1.61.6

(EtrkCC) 60%60% 40%40%

(MMMM22)req.)req. 32%32% 45%45%

B(DS+→+(8.0±1.3±0.4)%

( ; ) 1.059 ( ) ( / )s sB D B D SM PDG



Combined Combined ffDsDsCombine (i) and (ii).

= 91.4% = 45.2%N = 148 – (10.7+2.9

-

2.3)

[ ( ; )( ) ]ag st sN N BB D D (still applies)

Beff(DS+→+

(0.638±0.059±0.033)%

fDs= 274 ± 13 ± 7 MeV

B(DS+→e+x10-4 @90%CL

Signalregion

Results



Missing Energy AnalysisMissing Energy Analysis DDSS

++→→++++→→ee++

Xe+

Use 195 pb-1 at Ecm=4170 MeV

Reconstruct Ds tag, use recoil from Ds to get N(DsDs*)

Require one extra electron candidate + no other tracks.

No need to find from DS*

Main backgrounds from DS+→Xe+

Discriminant is ECCextra: extra energy in CC

left over after showers associated to reconstructed particles are removed.

Signal region: ECCextra < 400 MeV

Background obtained by scaling MC

B(DS+→+(6.29±0.78±0.52)%

fDs= 278 ± 17 ± 12 MeV

(Preliminary)(Preliminary)

400400 600

600

MeVMeV MeVMC

data dataMeVMC

NN N

N



Combined resultsCombined results

Weighted Average: Weighted Average: ffDsDs=275±10±5 MeV, =275±10±5 MeV, the the (systematic errors are mostly uncorrelated between (systematic errors are mostly uncorrelated between the measurements)the measurements)

Previously CLEO-c measuredPreviously CLEO-c measured

M. Artuso et al., Phys .Rev. Lett. 95 (2005) 251801M. Artuso et al., Phys .Rev. Lett. 95 (2005) 251801

Thus Thus ffDsDs//ffDD++=1.24±0.10±0.03=1.24±0.10±0.03 (D(DSS

++→→++(D(DSS++→→++

11.5±2.0, SM=9.72, 11.5±2.0, SM=9.72, consistent with lepton universalityconsistent with lepton universality

++2.3-3.4D

f =(222.6±16.7 ) MeVD+→

pbat

K0+

†



Comparisons with theoretical Comparisons with theoretical expectationsexpectations

CLEO-c data CLEO-c data consistent with consistent with most models, most models, more precision more precision neededneeded

Using Lattice Using Lattice ratio find ratio find |V|Vcdcd/V/Vcscs||=0.2166±0.020 =0.2166±0.020 (exp) (exp) ±0.0017(theory±0.0017(theory))



Comparison to previous Comparison to previous measurementsmeasurements

CLEO-c is most precise result to date for CLEO-c is most precise result to date for both both ffDsDs & & ffDD++

275±10±5

-2

-2



Decay constants from CLEO-c are most precise to dateDecay constants from CLEO-c are most precise to date

Expect to reach a precision of ~4.0-4.5% onExpect to reach a precision of ~4.0-4.5% onthese decay constants with full CLEO-c (through Apr these decay constants with full CLEO-c (through Apr 2008).2008).

SummarySummary

++2.3-3.4D

=(222.6±16.7 ) MeVfsD =(275±10±5) MeVf



BackupsBackups



Missing Mass Distributions - MCMissing Mass Distributions - MCCheck of resolution, procedure using DsKsK- Remove extra track/shower/K± veto

MC resolution consistent w/ data Find BF=(2.90±0.19±0.18)%,

Result from double tags: (3.12±0.16±0.10)%

This background is wiped out by the PID requirement on the stiff .

Documents

CHARM 2007, Cornell University, Aug. 5-8, 20071Steven Blusk, Syracuse University D Leptonic Decays near Production Threshold Steven Blusk Syracuse University