Post on 19-Jan-2016
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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
)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 !