Charm Physics Potential Charm Physics Potential at BESIIIat BESIII

Kanglin HeKanglin He

Jan. 2004, BeijingJan. 2004, Beijing

hekl@ihep.ac.cnhekl@ihep.ac.cn

OutlineOutline Charm physics at threshold Absolute Branching Ratio Leptonic Decay and Decay Constant Semileptonic Decay and CKM Matrix Physics Beyond Standard Model

D0D0 Mixing CP violation Rare Charm Decay

Summary

Charm Physics at ThresholdCharm Physics at Threshold Charm threshold

D physics @3.77GeV Ds physics @4.03GeV and @4.14GeV

Why charm threshold Pair production of charmed D and Ds mesons With less or without background

Take the advantage of BEPCII and BESIII Large data sample Better mass resolution and particle identification

Charm Cross Section and Charm Cross Section and Event Number for 1 yr runningEvent Number for 1 yr running

PhysicsC.M.S (Ge

V)Peak Lum.

1033cm-2s-1

cross section

(nb)Event Number

D 3.77 1.0 ~5 ~25M

Ds 4.03 0.6 ~0.32 ~1M

Ds 4.14 0.6 ~0.67 ~2M

Absolute Branching RatioAbsolute Branching Ratio Precision of Br(D0→Kπ), Br(D+ →Kππ), Br

(Ds→φπ) are normalization constants for Precision D, Ds physics Precision B physics

Precision of Br(D0→Kπ), Br(D+ →Kππ) , Br(Ds→φπ) are needed for Decay constants Precision of CKM elements

Model independent measurements at BESIII

Tagging Technology(1)Tagging Technology(1) Pair Production of D and Ds mesons

Large Brs (1~10%) of hadronic decay modes High tagged efficiency ~5M D tags, >0.2M Ds tags

0D

0De e

K

π

Tagging Technology(2)Tagging Technology(2) Beam Constrain MassBeam Constrain Mass

1.05MeVσM

DD++→→KKππππ Mode Mode GeV/c2

Tagging Technology(3)Tagging Technology(3)Kinematic constrain for Double tagsKinematic constrain for Double tags

D+ Double Tags D0 Double Tags

80 pb-1 Monte Carlo DATA @3.77GeV

Number of observed double tagsNumber of observed double tagsin 5fpin 5fp-1-1 Ds Data at 4.03GeV Ds Data at 4.03GeV

φπ KK*0 KK 0 0- ππKK γγ)(η

ηπ

)πηπη(

πη-

φπ 280

KK*0 697 512

KK 0 303 370 95

0- ππKK 820 1103 480 598

γγ)(η

ηπ

213 290 123 313 40

)πηπη(

πη-

173 233 100 253 67 27

~7000 double tags

Tagging Technology(4)Tagging Technology(4)

iiDDi εBN2S

ijjiDD

iiiiDDij εBBN2

εBBND

Number of expected double tags

Number of expected single tags

2

ij D

obsij

expij

i

2

s

obsi

expi2

σ

DD

σ

SSχ

Combining the single tags and double tags

Precision of Precision of Absolute Branching RatioAbsolute Branching Ratio

Now BESIII

D0→Kπ ~2.4% <1%

D+→Kππ ~6.6% <1%

Ds→φπ ~25% <2%

Improvement after BESIII

Leptonic Decay and Leptonic Decay and Decay ConstantDecay Constant

2cd(s)

2DD(s) |V|τ)Br(D

(s)(s)fl l

2cd(s) |V|

2D (s)f

l

W

c

sd

Measurement of Decay constantsMeasurement of Decay constantsat BESIIIat BESIII

Take the advantage of running at charm threshold Pair production →Double tag method, model independent

Take the advantage of BESIII detector High muon identification efficiency →suppress background

Take the advantage of BEPCII Large data sample →reduce statistic error

Information on the meson wave function Test lattice QCD Extract CKM elements

|Vcd|, |Vcs| Theory→ extract |Vtd|, |Vts|

Analysis TechniqueAnalysis Technique Double tag measurements

Tagged D(s) with hadronic decay modes muon identification Absent of isolated photons

Reconstruction of missing mass square →0

)p(ppνp

)EE(EνE

pEνM

μtagmissing

μbeammissing

222

Measurement of Measurement of ffDsDs

Precision of Precision of ffD(s) D(s) (1)(1)2

cd(s)

cd(s)2

2

D

D

D

D

|V|

|V|

B

B

2

1

2

1

(s)

(s)

(s)

(s)

f

f

1.0%τ

Δτ 0.6%

τ

Δτ

s

s

D

D

D

D

BESIII)at ( 1.6%|V|

|V|Δ1.8%

|V|

|V|Δ

cs

cs

cd

cd

BESIII)(at Level 3%~2 B

ΔB Major

Uncertainty

Precision of Precision of ffD(s) D(s) (2)(2)

Now

BESIII

100%

3.0%Δ

D

D f

f

Now

BESIII

35%

2.5%Δ

s

s

D

D f

f

Great improvement after BESIII

Semileptonic decay and Semileptonic decay and CKM MatrixCKM Matrix

lW

2

CKMV

)( 2qp

D(s)

2

CKMD(s) Vτ)Br(D(s)

plν

Form Factor

Measurement of CKMMeasurement of CKMat BESIIIat BESIII

Good performance of BESIII detector e/π/μ identification mass resolution

Extract |Vcd|, |Vcs| Form factor shape and normalization

Γ(q2) describe the contribution of form factor, it was calculated from lattice QCD.

The shape of form factor are helpful to theory.

Extract the ratio of |Vcd/Vcs|

Extract |Vub| from B physics →Theory

Analysis TechniqueAnalysis Technique

Hadronic tag PID Umiss

missmiss

tagmiss

tagbeammiss

PEU

PPPP

)E(EE

lp

e0 νeKD

e0 νeπD

Signal

Signal

Background

Background

(GeV/c)

Precision of Branching RatioPrecision of Branching Ratioof Dof D00, D, D++ Semileptonic Decay Semileptonic Decay

Precision Now BESIII

D0→Klν ~4.4% <1%

D0→πlν ~17% <2%

D+→Klν ~12% <2%

Precision of CKMPrecision of CKM 2

q

q

2

D

D

2

cq

cq

2Γ

ΔΓ

2τ

Δτ

2B

ΔB

V

VΔ

Form factor term ΔΓ/Γ ， come from theory (Lattice QCD). Supposing ΔΓ/Γ ~3% , BESIII will get

%4.1R

R

V

VR

1.8%V

VΔ1.6%

V

VΔ

cs

cd

cd

cd

cs

cs

Form FactorsForm Factors

data from α and (0)Extract

(0)e)(qfactor form Taking

Eq where,

)(q24π

VG

dq

dΓ

ratedecay the,KeDFor

2αq2

2

lv2lv

2

223

3K

2

cs2F

2

f

ff

p

fp

From semileptonic decay of charm meson, dN/dq2 will provide information on form factors

(under studying)

Physics Beyond Standard ModelPhysics Beyond Standard Model

D0D0 Mixing at ψ(3770) In SM, mixing is very small(10-6). BESIII is sensitive to 10-4

Possible to measure the phase shift CP violation in charm decays

SM predicts the ACP may be as big as 10-3.

BESIII is sensitive to ACP >10-2

Rare Charm Decay

DD00DD00 Mixing Mixing

e

e

0D

0D

K

K

π

π

D0 decays as D0

Separate Mixing from DCS

Mixing Phenomenology(1)Mixing Phenomenology(1)

0D 0D

Like the K0K0 mixing, constructing DS and DL

0D0D

K

KW W

2

yx

decays)Γ(D

decays)DΓ(Dr

virtual)( ΔMx (real) 2ΓΔΓy

22

0

00

D

Experimental SituationExperimental Situation

x0 0.1 0.2

0

-0.1

0.1y

x and y are in the orders of 10-2─10-1

Mixing Phenomenology(2)Mixing Phenomenology(2)

0D

0D

DC

S

πK

Mix

ing

CF

AArδδδ

AeDπKAeDπK

WR

iδ0iδ0 wR

Measuring the Asymmetry of CP eigenstate (K+K-(+), Ksρ0(-) …)

2rcosδ)Γ(CP)Γ(CP

)Γ(CP)Γ(CP

Α

Supposing CP violation is smallPossible to measure the phase shift

Mixing at Mixing at ψψ(3770) (3770) The D0 and D0 are produced coherently in JPC=

1-- state

DCSD (Double Cabbibo Suppressed Decay) contribution is 0 at ψ(3770)

D0 produced ~at rest, cannot measure ΔΓ (y) directly by using lifetime difference

kDkDkDkD2

1DD 000000

Useful for measuring rD

Experimental Searching forExperimental Searching forDD00DD00 Mixing Mixing

Big challenge to PID (Kπchannel) Main backgrounds come from the double mis

s-PID Searching in semi-leptonic decay modes

are experimental difficulty with 2 missing neutrino (hard to reduce background contribution to 10-4)

Monte Carlo study with different PID (TOF resolution)

Detection efficiency vs Detection efficiency vs TOF resolutionTOF resolution

Efficiency vs time resolution

30

32

34

36

38

40

60 65 70 75 80 85 90 95 100 105 110 120 130

Time resolution(ps)

effi

cien

cy(%

)

Background rates vsBackground rates vsTOF resolutionTOF resolution

Background vs time resolution

0

1

2

3

4

5

60 65 70 75 80 85 90 95 100 105 110 120 130

Time resolution(ps)

Bac

kgro

und(

10-4

)

Probing New Physics to rD~10-4

The detection efficiency is ~40%, ~20K events with D0→K+π- are expected to be found in 5fb-1 ψ(3770) data

The background contamination rate is 0.1─0.5x10-4 while the TOF resolution varies from 65ps to 100ps

BESIII is sensitive to 10-4 for the mixing rate if the TOF resolution is designed to be around 100ps.

CP Violation at CP Violation at ψψ(3770)(3770)

0D

0D

K

K

π

π

Suppose Both D0 decay to CP eigenstate f1 and f2 .

Any oberservations of CP(f1)=CP(f2) at ψ(3770) are the direct evidence of CP Violation

)ψCP(1)()CP()CP()CP(

ψ ofdecay for theL

2121

21

ffff

ff

Several hundreds events with 100% CP eigenstate will be found in 5fb-1 ψ(3770) data. The sensitivity of direct CP violation is ACP~10-2─10-1

Rare Charm DecayRare Charm Decay

......

)K , , ,( γγ,eμ μμ, )ee,K , , ,(

eμ μμ, )ee, , K, ,(

eμ μμ, ee,

D*

*

The Up limit for most modes listed above are estimated in the range of 10-6─10-5,

will update PDG data.

Summary Summary BESIII contributes to charm physics onBESIII contributes to charm physics on

Precision absolute branching ratio of charm mesons (<1% for D, <2% for Ds)

Precision decay constants (2~3%) Precision CKM Matrix (<2%) Sensitive to rD~10-4 for mixing

Sensitive to ACP~10-2─10-1 for CP violation Set the up limit of branching ratio for most rare

charm decays to 10-6─10-5 range And more, more,……

Comparison of BES3, CLEO-c and B-factories Comparison of BES3, CLEO-c and B-factories On Charm physics topicsOn Charm physics topics

MeasurementB-factories CLEO-c BES3

—2004 1yr 1yr

(2~3)% ~0.6% <1%

(3~5)% ~0.7% <1%

(5~10)% ~1.9% <2%

>10% ~2.3% ~3%

(6~9)% ~1.7% ~2.5%

Major Error Sys. Stat.

)KD(Br 0

)KD(Br

)D(Br S

Df

SDf

* D/Ds cross section over estimated by a factor of 2 this number need confirming

Thank you !Thank you !

谢谢谢谢