Recent Charm Results From CLEO
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Transcript of Recent Charm Results From CLEO
Recent Charm Results From CLEO
• Searches for D0-D0 mixing
• D0 -> K0s+-
• D0->K*+l-• Conclusions
Alex SmithUniversity of Minnesota
1) Large |x| 2) |x| >> |y| 3) CP violation of any kind
D0 – D0 Mixing Analyses: Preliminaries
Use D0’s from D* decays to tag flavor of D0
D*+ D0+
Categorize D0 decays according to flavor of D0 and of K:
“Right sign (RS)”:
“Wrong sign (WS)”:
*0
00
0
KD
KD
KD
*0
00
0
KD
KD
KD
Cabibbo-favored (CF) decays
x, y, or doubly Cabibbo-suppressed decays (DCSD)
Complication: Strong phase s due to final state interactions:
SS
SS
xyy
yxx
sincos
sincos
x and y are what we really want
Current Status of D0-D0 MixingRecent Experiments:
CLEO, FOCUS, Belle, BaBar, E791Recent Predictions:
= x = y = non-SM
(|x|,
|y|,
etc.
)
(1/2|Am
plitude| 2)
Motivation to Study D0->Ks0+-
• Measure x and y rather than x’2 and y’
• RS and WS occupy the SAME Dalitz plot:
• First measurement of relative strong phase between D0 and D0 to to K0
s+- final state
• Only mode with sensitivity to sign of x!
• Doubly-Cabibbo-suppressed modes
• Comparable sensitivity to y as CP eigenstate (eg., D0->K+K-) analyses
• Better scaling of sensitivity to x with int. luminosity than D0->K+- analysis
• Low backgrounds ~1%!
• ~Flat efficiency in e+e- collisions
D0->Ks0+-: Dalitz Formalism
Visualize as pseudo-two-body
decay:
rBAABrABr
CDDr FPPqiMMM
PPF
22
*
0M
nr
nn
rr i
rr
i
rr
i
rr eAeAeA MMMM 2
22
1
11
Amplitude for each resonance given by a relativisticBreit-Wigner, with angular distribution determined by J. For J = 1 we have:
Total amplitude is the sum with a complex coefficient:
We consider 18 resonant and non-resonant decay modes:
resonant-non ,1430 ,
,1710 ,1500 ,1370 ,1270 ,980
,500 ,1700 ,1450 , , ,1780
,1680 ,1430 ,1430 ,1410 ,
0*
00020
0003
*20
**
KK
fffff
K
KKKKK
Con
trib
utio
ns to
the
Dal
itz
Plo
t
K*-
K0(
1430
)-K
2(14
30)-
K* (
1680
)-
0
f 0(98
0)
f 2(12
70)
f 0(13
70)
0(1
700)
/ 0
(145
0)
K*+
K0(
1430
)+
Dalitz Plot
Data
Fit Result
Component Amplitude Phase (0) Fit Fraction
K*(892)+
(770)0
(792)
K*(892)-
f0(980)
f2(1270)
f0(1370)
K0(1430)-
K2(1430)-
K*(1680)-
Non-res.
Results of Dalitz Plot Fit
054.0030.0
050.0016.0 029.0131.0
4
1158 11152
0.00200041.0
0.011227.0 005.0006.0 0.01 006.0055.0
38 4 7117
0.003013.0 05.007.0 0.04 05.068.1
35
32 2149
0.014672.0
0.005040.0
0.002006.0
0.0107.0
0.009080.0
0.002015.0
0.006023.0
0.016027.0
06.002.0
06.003.0 02.036.0
8.02.0
2.03.0 2.08.0
(fixed) 0(fixed) 0.1
199
13 5185
271321368
7.05.0
24.0010.0 14.056.1
0.4 1.02.2 1.02.0
0.4 1.09.0 3.00.0
8.22.4 0.9 8.06.5
4.19.0
6.04.0 6.09.1
2111
217 674
1022
65 511
1911 6847
1820 128173
169
167 1130
syst. modelingsyst. exp.stat.result
D0->Ks0+- Summary
• First observation (4.5) of WS D0->K0+-
• We observe 5 new submodes (10 total) of this decay
• First measurement of strong phase shift s between D0->K0+- and D0->K0+- = (-3 +/- 14)0
• Time-dependent analysis can measure sign of x (coming soon!)
• This is the best mode in which to search for mixing:
• y is likely to be comparable to or larger than x => must measure strong phase
D0->K*+e-• Reconstruct K*+ in Ks
0+, Ks0-> + - mode
• Advantages of this mode:• Only mixing contributes to WS signal
• Distinct proper time distribution of mixing: t2e-t
• K* mass cut rejects backgrounds
• Drawbacks of this mode:• Low momentum tracks due to e final state
• Soft e momentum due to forward neutrino favored by V – A coupling
• Must “pseudo-reconstruct” the undetected neutrino
• Only sensitive to x
D0->K*+e-: Fit to the “Right-sign” Data
candidates 51638
Distributions from Monte Carlo
D0->K*+e-: Fit to the “Wrong-signed” Data
candidates 99.100.0
Fit distributions from Monte Carlo
D0->K*+e-• Systematic uncertainties:
• Signal and background shapes• MC Statistics
• Resolution and background parameters
• Differences in RS and WS efficiencies
C.L. %95@ 0087.0
10(syst) 0.32(stat) 31.000.0
mix
2mix
R
R
2221
mix yxR
• Results to be combined with D0->K+l- analysis• Comparable sensitivity
Other CLEO Charm Analyses in Progress:
Summary• First observation (4.5 statistical
significance) of DCSD D0->K0+-
(prelim.)
• We observe 5 new submodes of this decay
• First measurement of strong phase shift s between D0->K0+- and D0->K0+- = (-3 +/- 14)0 (prelim.)
• First analysis that can measure sign of x (coming soon!)
• Best channel in which to search for mixing
C.L. %95@ 0087.0
10(syst) 0.32(stat) 31.000.0
mix
2mix
R
R
D0->K0+-:
D0->K*+l-:
• CP-even and CP-odd intermediate states provide sensitivity to 1 and 2, thus y
• Sensitivity to sign of x = M/ through sin term in |M|2
•
• Interference between Cabibbo-favored and DCSD may enhance sensitivity to x
D0->Ks0+-: Time Evolution of the Dalitz Plot
xofsign tosensitivex y tosensitivit
y y tosensitivit
2
y y tosensitivit
22sinsincoscos221 xtexteee ttttM
odd
002
even
001
CP
CP
DqDpD
DqDpD
22110
22110
2
1
where, 2
12
DteDteq
tD
eteDteDtep
tD ttiMi
ii
Mass eigenstates are also eigenstates of CP:
Time evolution is given by:
Evaluating <f | D1> and <f | D2>, collecting terms with similar time-dependence, and squaring the amplitude gives:
measured becan
and between phase strong Relative 0000s
KDKD