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Charm Physics Potential at BESIII. Kanglin He Jan. 2004, Beijing [email protected]. Outline. Charm physics at threshold Absolute Branching Ratio Leptonic Decay and Decay Constant Semileptonic Decay and CKM Matrix Physics Beyond Standard Model D 0 D 0 Mixing CP violation - PowerPoint PPT Presentation
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Charm Physics Potential Charm Physics Potential at BESIIIat BESIII
Kanglin HeKanglin He
Jan. 2004, BeijingJan. 2004, Beijing
[email protected]@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