DD00DD00bar Mixing and bar Mixing and CP Violation at BESIIICP Violation at BESIIIDD00DD00bar Mixing and bar Mixing and CP Violation at BESIIICP Violation at BESIII

Kanglin HeKanglin HeJune 2006, BeijingJune 2006, Beijing

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OutLine• D0D0bar Mixing• CKM γ/ϕ3 measurements• CP violation• Dalitz Plot analysis • Time-Independent measurements using Th

e Quantum Correlation Analysis (TQCA)• Summary

3

D0D0bar Mixing• Flavor eigenstate == mass eigenstate• Expected to be very small in Standard Mod

el• Sensitive to New Physics • x, y =0 in the SU(3) limit• Experiments are beginning to probe interes

ting region of mixing parameter space (x, y ~10-3)

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Mixing in the Standard Model and Beyond

0D 0D

,K,,K

K,,,K

Standard Model

New Physics

Common hadronic final states

2

y

m

x

(real, on-shell)

(virtual, off-shell)

Loops provide sensitivity new physics via xFSI may enhance both x and y in SM

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Mixing Parameters 22

mix yx2

1R

KK

KK

cosysinxy

sinycosxx

)CP()CP(

)CP()CP(yCP

sinxcosyyCP

Mixing rate

Strong phase difference of CF decayand DCS decay, important to measure

CP eigenstate lifetime difference

CP violation phase

2222qpqp

sinx2 CP violation in mixing/decay interference

If CP is conserved, ϕ=0, Δ=0, yCP=y

CPV in mixing

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Theoretical Predictions

Theoretical predictions are very variable

x, y in range of 10-7-10-2

From A. PetrovCharm Physics: Theoretical Revie

whep-ph/0311371

New Physics

Standard Model

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Mixing in High Energy Experimentflavor tag by D*π+D0

fitting the time distribution

0S0 KD

Wrong-sign semileptonic decays(K(*)ev), measure Rmix

(E791, FOCUS, BELLE, BaBar, etc)

Decay to CP eigenstates(KK), measure yCP

(E791, FOCUS, BELLE, BaBar, CLEO, etc)

Wrong-sign Kπ decays, measure x ’2 and y ’

(CLEO, FOCUS, Belle, BaBar, etc)

Dalitz plot analysis 00 KD

(CLEO, Belle, BaBar, etc)

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Experimental Situation

No evidence of mixing has been reported in the charm sectorHopefully to be found in near future

yCP measurements

(Close to confirm)

PD

G0

6

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D0D0bar Mixing at BESIII

• Charm events at threshold are very clean– Ratio of signal to background is optimum– Lots of systematic uncertainties cancellation while apply

ing double tag method• Mixing at threshold

– Bad news: no time-dependent information– Good news: Quantum coherence, CP tags– The coherence of two initial D allows simple methods to

measure DDbar mixing, strong phase and CP violation– Sophisticated methods combining semileptoinc, CP and

hadronic modes provide additional sensitivity

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D0D0bar Mixing (Kπ)

e

e

0D

0D

K

K

π

π

D0 decays as D0barKey Point: Separate Mixing from

DCSD

）（3770

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Separate Mixing from DCSD

D0

D0

K+π-

DC

SD

mix

ing

CF

Two path to D0D0bar decay final state: 1. D0K+π- (DCSD)2. D0D0bar － >K+π- (MIX)

In the case of no mixing, (K+π- )(K+π - ) is forbidden by Bose-Einstein statistics

D0Kπ and D0barKπ require L even, but for Ψ(3770) decay, L = 1

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Challenge to PID• BESIII PID system

– dE/dx, resolution (6-7)%– Two layer barrel TOF, time resolution ~1

00ps, ~83% solid angle coverage– 1 layer endcap TOF, ~110ps

• Selection efficiency is >20% with a K/π double mis-identification rate at < 10-4 level

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Mixing in double semi-leptonic decays (Kev channel) at BESIII

• Two missing neutrinos in events• Electron PID can suppress background• The selection efficiency is similar as the Kπ

channel• Background level is also negligible while ru

nning a small MC data sample (~1% of 20fb-

1). More detail study is needed.

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Rmix sensitivity at BESIII

• With 20fb-1(4-5 years running) Ψ(3770) data sample, we may get– ~20,000 right sign Kπ events– ~20,000 right sign Kev events– If more electronic channels and muonic channe

ls are applied (need further MC studies), more right sign events will be obtained

• BESIII will probe

Rmix <10-4

in combined Kπ and semileptonic channels

(At least)

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CP eigenstate Tags• CP +

– K+K- (3.89X10-3 )– π+π- (1.38X10-3 )– Ks π0π0

– π0π0 (8.4X10-4)– KSKS (7.1X10-4)– ρ0 π0 (3.2x10-3)

• CP –– KSπ0(0.012)– Ksη (3.9X10-3)– KS η’ (0.0094)– KSρ0 (0.0078)– Ksω (0.012)– KSφ (4.7X10-3)

In 20fb-1 Ψ(3770) data, we can get> 4.5x105 CP+ tags and > 3.6x105 CP- tags

With large sample of CP tags, we may improve the measurementsof strong phase, probe the direct CP, and other mixing parameters

Dalitz Analysis

KL modes canalso be applied

partially

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CKMγ/ϕ3 measurement

*cbcd

*ubud

3

*tbtd

*cbcd\

1

*ubud

*tbtd

2

VV

VVarg

VV

VVarg

VV

VVarg

UnitarityTriangle

Extract γ/ϕ3 from BDK decays, where D decays to

1. D to CP eigenstates (GLW): improved constraints on charm mixing amplitude

2. D to flavor eigenstates Kπ (ADS): measurement of relative rate and strong phase

3. D to Ksππ(Dalitz plot analysis): studies of charm Dalitz plots tagged by flavor or CP eigenstates

Need help from charm sector

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Asymmetry =

0D

0D

K+

K+

CP+ eigenstate

0D

0D

K+

KS

CP- eigenstate

0D

0D

K+

K+

CP+ eigenstate

0D

0D

K+

KS

CP- eigenstate

Useful for probing r & = 2 r cos

Strong Phase (I)

w0

R0

iexpADK

iexpADK

WRK DrA

Ar

If CPV=0Mixing is

small

Ratio of DSCD/CF

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Strong Phase (II)

cosr2)CP()CP(

)CP()CP(A

Nr2

1cos

In 20fb-1 Ψ(3770) data, we can get> 10,000 CP+ vs Kπ double tags> 10,000 CP- vs Kπ double tags

The precision of cosδ < 0.06 level is expected at BESIII,Be helpful to improve the precision of γ/ϕ3 measurement

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CP Violation

)fD()fD(

)fD()fD(A

qq

qq

)Xl)t(D()Xl)t(D(

)Xl)t(D()Xl)t(D(A

0phys

0phys

0phys

0phys

)f)t(D()f)t(D(

)f)t(D()f)t(D(A

CP0physCP

0phys

CP0physCP

0phys

1. Direct CP Violation (in decay)

2. Indirect CP Violation (in mixing)

3. CP violation in the interference between decays with/without mixing

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CP violation in Charm decays• In SM, no Direct CP asymmetry in CF and DCS mod

es. New physics• Buccella et al. predict CP asymmetries in decay in

the range of 0.002%0.14%, may up to 10-3 level • Indirect CPV due to mixing is a possibility for D0 de

cays• CP studies in charm transitions represent an almo

st 0-background search for New Physics (Bigi and Sanda)

• If New Physics intervenes through DCSD, then it would have the cleanest impact on D+KS,Lπ+ (Bigi and Sanda)

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Direct CP ViolationNeed two paths (CKMweak +FSIstrong) fr

om initial D to final state fD

f

22

ieA11

ieA

D

f

2*2

ieA1i*1eA

Compare D f to D f

21 *2

*1

iif

eAeAA

2121

iif eAeAA

)cos()Re(2

)sin()Im(2

212*1

2

2

2

1

212*1

22

22

AAAA

AA

AA

AAA

ff

ff

CPFind:

Singly Cabbibo Suppressed decays (SCSD)should be the good choice to measure a sizeable asymmertry

Not too diff.

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Experimental search CP Violation in Charm decays

• A Cabbibo allowed reference states is needed to calibrate the known production/detection asymmetries

Define )D()D(

)D()D(ACP

Where η is the ratio of N (searched) / N (referenced)

D0: K-π+, D+: K-π+π+, Ds: K-K+π+

D0: K-K+, π-π+, Ksπ0, etcD+: K-K+π+, Ksπ+, KsK+, etcDs: KsK+, Ksπ+, etc

DCSD mode: D+K+π+π-

D0K+π-π-π+ Probe New Physics

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CP asymmetry measurement

1% level reached for some decay modes, no evidence of CP Violation

Experiment Decay mode ACP(%) comments

BaBar

D+K-K+π+ 1.4±1.0±0.8

D+ϕπ+ 0.2±1.5±0.6 Resonant substruct of D+K-K+π+

D+K*0K+ 0.9±1.7±0.7

CLEO D0π+π-π0 1+9-7±8 Dalitz Analysis

CDFD0K-K+ 2.0±1.2±0.6

Direct CPVD0π-π+ 1.0±1.3±0.6

FOCUS

D0K-K+π+π- 1.0±5.7±3.7T Violation through triple product correlations

D+K0K+π+π- 2.3±6.2±2.2

DsK0K+π+π- -3.6±6.7±2.3

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CP Violation at BESIII• Quantum Coherence

– Psi(3770) -- D(CP+)D(CP+), D(CP-)D(CP-)• CP asymmetry in D+ and Ds decays

– Lots of modes, include DCSD• CP asymmetry in D0 decays

– Have to pay price for tag – Flavor tag with semileptonic mode at Ψ(3770)– Flavor tag with D-K+π-π- modes above DD* thr

eshold (4.03GeV / 4.17 GeV)• Indirect CP asymmetry is too hard to BESIII

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Quantum Coherence

0D

0D

K

K

π

π

Suppose Both D0 decay to CP eigenstate f1 and f2 .

)ψCP(

1)()fCP()fCP()ffCP(

ffψ ofdecay for the

L2121

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Thus if a final state such as (KK)(ππ) observed, we immediately have evidence of CP violation

In 20 fb-1 Ψ(3770) data, > 1000 double CP+ and CP- tags can be obtained. if 100%CPV, it lead to ACP~10-3 level

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CP Violation in Charm decays (I)

D+K-K+π+ ~3x105

D+Ksπ+ ~5x105

D+KsK+ ~1x105

DsK+π+π- ~105(20fb-1 @4.17GeV)

D0K+π-/K+π-π-π+ 300/500(DT)

D+K+π+π- ~3x104

3CP 103A

In 20fb-1 data, BESIII can obtainthe precision of CP asymmetry in decays of charmed mesons

for the DCSD modes, BESIII can probe New Physics at ACP ~(10-2 10-4) level

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CP Violation in Charm decays (II)

Xsec ExpD*+D- + D*-

D+ D*+D*-

4.03GeV BES I 2.31nb 0.87nb

4.14GeV Mark III 0.7nb 1.8nbIf 20fb-1 data taking at 4.03GeV, ~9,000 D0 CP tags4.17GeV, ~5,000 D0 CP tags

Expected to be obtained

Flavor tagged by D-K+π-π-

2CP 105.10.1A ）（

The precision of CP asymmetry will be

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CPV interference with Mixing

sinxcosy)CP()CP(

)CP()CP(yCP

sinxcosy)CPD()CPD(

)CPD()CPD(A

00

00

sinxAcosyyCP

Two interesting case with semileptonic tag + CP tags

CPV in Mixing is small, Δ=0

In 20fb-1 psi(3770) data, 10,000 SL+CP(+) tags 10,000 SL+CP(-) tags

ΔyCP and ΔAΓ~ 1% level

Applying the inclusive semileptonic tag Can improve the measurements

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Dalitz Plot Analysis• Developed by CLEO, BaBar, Belle, etc • Modes: Ksπ+π-, K-π+π0, K-K+π+, π-π+π0, etc• Time-dependent Mixing measurements• DCSD branching ratio measurement (including phase)• CP Violation studies• Measurements of γ/ϕ3 in BD(*)K(*)

• Strong phase measurement

The powerful tool will be applied in BESIII

What will we do next?1. Understanding the ππ or Kπ S-wave scattering (learn fro

m BESII J/Psi analysis and other experiments, such as: applying K-matrix formulism etc)

2. Currently, we have a piece of FORTRAN code. Develop a OO version PWA package for charm decays in future

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CPV in Dalitz Analysis

iii

iii

2bc

2ab

2bc

2ab22

22

CPdmdm

dmdmMM

MM

A

Strong phase, do not change sign under CP conjugation

CPV phase, change sign under CP conjugation

Phase difference hints that CP is violated

CP asymmetry across Dalitz plots

Advantage of using Dalitz plot Analysis:1. Measure CP asymmetries2. Direct access to the phase

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Dalitz Analysis at BESIIIInteresting topic (I)

• K-π+π0, Ksπ+π- vs CP tags, measure strong phase of Kρ, K*π

• K-π+π0, Ksπ+π- vs flavor tags, measure Br of DCSD

• Ksπ+π-, π-π+π0 vs CP tags, search for CP Violation (via same sign CP Tags)

• CP asymmetries across Dalitz Plots– Ksπ+π-, π-π+π0 vs flavor tags– D+ K-K+ π+

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Dalitz Analysis at BESIIIInteresting topic (II)

• Simultaneously fit two Dalitz plots of K-π+π0 vs K-

π+π0 and Ksπ+π- vs Ksπ+π- , search for Mixing in Kρ, K*π modes

• PWA analysis to DVV vs CP Tags, search for CP violation and measure the strong phase

• more and more, ……

Lots of interesting modes can be applied, to improve the measurements of Mixing parameters

and search for CP violations in charm decays

Key point: Quantum Coherence

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Time-independent Quantum Coherence

• The Quantum Coherence Analysis (TQCA)• Ψ(3770)D0D0bar C=-1• Ψ(4040)/Ψ(4160)(mγ)(nπ0)D0D0bar C=(-1)

m+1

• measure RM, r, cosδKπ, y and xsinδKπ (at Ψ(4040) or Ψ(4160))

• Suggested by D. Asner and Sun etc, part of CLEO-c physics program

• Will be applied at BES III

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TQCA at psi(3770)

f l+ CP+ CP-

f RM

l+ r2 RM

l- 1 1 1

CP+ 1+2rcosδ 1 0

CP- 1-2rcosδ 1 2 0

X 1+2yrcosδ 1 1-y 1+y

DT

ST

RM = (x2+y2)/2

r = Amp DCS/Amp CFSee PRD 73 034024 (2006) [hep-ph/0507238]

by Asner and Sun

Measure RM, r, cosδKπ and decay fractions

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TQCA (C=+1)

f l+ CP+ CP-

f 4r(r+ycosδ-xsinδ)

l+ r(r+2(ycosδ-xsinδ)) 3RM

l- 1+2r(ycosδ+xsinδ) 1

CP+ 1-2rcosδ-2y 1-2y 2(1-2y)

CP- 1+2rcosδ+2y 1+2y 0 2(1+2y)

X 1+2yrcosδ 1 1-y 1+y

DT

ST

Have a chance to measure y and xsinδKπ

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Estimated uncertainties (stat.) of

Mixing parameters using TQCA

parameter

valueCLEO-c (3x106D0D0b) BESIII(20fb-1)

C=-1 C=+1 C=-1 C=+1

y 0 ±0.015 ±0.007 ±0.003 ±0.002

x2 0 ±0.0006 ±0.0003 ±0.00013 ±0.0001

cosδKπ 1 ±0.15 ±0.13 ±0.035 ±0.04

xsinδKπ 0 ─ ±0.010 ─ ±0.003

From PRD 73 034024 (2006) by Asner and Sun Scale to

BESIII

Have to identify C=+1 of γD0D0bar and γD0D0barπ0

from D*Dbar and D*D*bar decays

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Summary• Mixing parameters

– Rmix < 10-4 in Kπ and Kev channels– ΔcosδKπ < 0.05 – Probe y: yCP ~ 10-4, ΔyCP ~ 1%, Probe x: 4.03/4.17 GeV – Possible to probe CPV phase ϕ if x is sizeable

• CP Violation– ΔACP~10-3 in D+ decays, – Probe new physics at ACP<10-2 level in DCSD– Probe ACP<10-3 level with DT CP tags

• Dalitz Plot Analysis are expected to improve the measurements

• TQCA method can improve the measurements• A lot of work need to do in future

Excited results can be produced at BESIII in Mixing and CP Violation in Charm sector!!!

Thank You !Thank You !Thank You !Thank You !