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

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

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:

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

Do-Do lifetime mixing

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

Mkk

Mkk

Mkk

Mkk

SAMPLE HANDLING

Do KKis CP=+1

need over10,000 ev.to reach

1% errorin

Fit spanning Fit spanning

overover ~10 ~10 !!!!

Fitting Fitting (D(Doo[K[K]) and y]) and ycpcp

10,331 events

119,738 events

MEASUREMENTS

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

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:

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

DoK+-

from D*

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.

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!

Make a total of 80 fits (wrong sign and right sign) on 40 1 MeV strips

Y=36760 ± 195 Y=148.5 ± 31.3

M

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

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

CP asymmetries

CP asymmetry for D mesonsCP asymmetry for D mesons

1623±47

18501±144

1706±53

19633±149

6860±110 7355±112

73710±29268607±282

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.

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