Download - STARTING POINT Budapest july 2001
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CHARM MIXING CHARM MIXING AND CP VIOLATION AND CP VIOLATION
IN FOCUS IN FOCUS AT FERMILABAT FERMILAB
CHARM MIXING CHARM MIXING AND CP VIOLATION AND CP VIOLATION
IN FOCUS IN FOCUS AT FERMILABAT FERMILAB
EPS-HEP2001Budapest, , july 12-18, 2001
SERGIO P. RATTISERGIO P. RATTIINFN and Dipartimento di Fisica Nucleare e Teorica - PAVIA
for the FOCUS COLLABORATIONfor the FOCUS COLLABORATION
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Outline of the talkBasic phenomenolgy: Do-Do mixing:lifetime mixing: yCP=DCS decay Do K+- (from D*)Comparison with other experimentsD-D asymmetries: search for CPConclusions
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2yxR
22
unmixed
mixmix
INTEGRATING |AINTEGRATING |Amixmix||22 OVER TIME, MIXING IS DESCRIBED BY: OVER TIME, MIXING IS DESCRIBED BY:
Do-Do MIXING
)]cos(21[)( 2/)(2
00 1 mteeetDD ttt
THE MIXING AMPLITUDE SQUARE IS:THE MIXING AMPLITUDE SQUARE IS:
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2yxR
22
unmixed
mixmix
For a HADRONIC DECAY Do K+-
RRWSWS=(Do K+- )/(Do K-+ )ee--tt[R[RDCSDCS+R’/2 t+R’/2 t22 +y’ t +y’ t RRDCSDCS]
Do K-+ is C.F.Do K+- is WRONG SIGNWRONG SIGN
D.C.SD.C.S. orfrom mixing box diagrammixing box diagram
STRONG PHASE STRONG PHASE y’= y cos x sin
x’= x cos y sinR’=(x’2+y’2)/2
KDD 00
KD0
0* DD
cu u
d
us
KcdV
usV
0D
DCS
0D Kuss
uc s
du
c
csV
udV
BOX
or
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Do-Do lifetime mixing
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LIFETIME MIXING
and 2
)]([;)]([ 0 KDKKD o
assuming CP conserved :
CP|k+k->=+1; CP |k-+>=equal mixture. Therefore:
Thus:
1)]([)]([y CP
KKK
o
o
DD
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Mkk
Mkk
Mkk
Mkk
SAMPLE HANDLING
Do KKis CP=+1
need over10,000 ev.to reach
1% errorin
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Fit spanning Fit spanning
overover ~10 ~10 !!!!
Fitting Fitting (D(Doo[K[K]) and y]) and ycpcp
10,331 events
119,738 events
MEASUREMENTS
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Results
Mass (GeV)
Phys. Lett. B485, 62 (2000)Phys. Lett. B485, 62 (2000)
yCP= 3.42 1.39 0.74 %=409.40 1.34 ?? fs
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SPECULATIONS
(KK)= =(395.8±5.5) fs 2= (415.5 ± 11.5) fs
Purely speculative: ns
Just for the fun of it!!! From: 2 1
(K) = and yCP get (KK)= ; 1
+ 2 1
1 - 2
ycp= get -=1/ 2 ; get .
1 + 2
From:
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1
E791 0.82.91 %
(CLEO mixing) ( 5.8<y<1 %)
FOCUS 3.421.390.74 %
BELLE prel. 1.671.651.16
%
CLEO prel -1.12.51.4 %
1.81.0 %Average yCP 2 = 2.3 for 3
Conclusion: BELLE, CLEO, E791 and FOCUSThe comparison to CLEO mixing analysis isvaild only if one assumes a small strongphase difference .
95% CL
FOCUS
CLEO
E791
BELLE
CLEO
E791
x
y
Comparison of yCP measurements
semileptonic
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DoK+-
from D*
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The CLUE of the WRONG SIGN STUDIESWRONG SIGN STUDIES when the nature of the Do meson is identified by the parent D*
is the RESPONSE OF THE CERENKOV COUNTERS to solve the K K AMBIGUITY AMBIGUITY
MORE SO since we have to directly compare KK-- ++ to K to K++ --
single misidentification implies “regular background”DOUBLE MISIDENTIFICATION WOULD RETAIN THE DOUBLE MISIDENTIFICATION WOULD RETAIN THE
EVENT EVENT BUT BUT IN THE WRONG CATEGORY!!!!IN THE WRONG CATEGORY!!!!
STARTING FROM OVER 200,000 D* EVENTS,this study required a sistematic Montecarlo
investigation to sort out the wrong sign K+- signal (either DCS decay or BOX diagram decay)
from the overwelming background.
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Simulate 3 different types of background, i.e.:Do+-; DoK+K-; partially reconstructed D’sand DoK double misidentified; double misid.Do‘shandled with adequate Cerenkov cuts. Subdivide the M distribution into 1 MeV bins and fit the remaining backgrounds plus signal to M(K).
When the wrong K havemass around the right K!M=MD*-MD is at the peak!
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Make a total of 80 fits (wrong sign and right sign) on 40 1 MeV strips
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Y=36760 ± 195 Y=148.5 ± 31.3
M
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We obtain: RWS=(0.405 ± 0.085 ± 0.025)%Of course -as we have seen- RWS becomes
a function of t in presence of mixing
Consistent with SM Cabibbo tg4
Phys. Rev. Lett. Phys. Rev. Lett. 8686,2955,2001,2955,2001
19342145
0.77 ± 0.25 ± 0.250.68 ± 0.071.77 ± 0.31
0.332 ± 0.040
CLEOCLEOE791E791ALEPHALEPHCLEO II.VCLEO II.V
EventsEventsRRDCSCDCSC(%)(%)
+0.34-0.33
+0.063-0.065
+0.60-0.56
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with mixing assumption and
22'2'
' /4
/ tyxtyRRR DCSDDCSDWS
t/=1.578±.008(t/=3.61±.03estimate t/ and (t/ using MC
Rws=(0.404 ±.085 ±.025
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CP asymmetries
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CP asymmetry for D mesonsCP asymmetry for D mesons
1623±47
18501±144
1706±53
19633±149
6860±110 7355±112
73710±29268607±282
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Parameter A for D mesonsParameter A for D mesons
Comparison to other experimentss
No evidence for CP violation so far. Our limit on No evidence for CP violation so far. Our limit on KK++KK- - needs tagged Dneeds tagged Doo ‘s from D ‘s from D**, which cuts our , which cuts our
sample bysample by ~80%.~80%. Our limits: most precise published Our limits: most precise published
measurements reflecting our large statistics.measurements reflecting our large statistics.
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ConclusionsConclusions
can we speculate that Do-Do mixing is 0?yCP=(3.42±1.39±0.74)% has a 90% CL limit 0.
Rws=(0.404 ±.085 ±.025)% would beRDCSD in absence of mixing
if mixing Rws compatible with CLEO IINo evidence for CP violation at 1% level semileptonic decays still to be tackled
CP=-1 states still to be adressed