1

Measurement of in with final state

Camilla Di Donato

2

Outline of the talk

• Motivations of this analysis• The data sample• Event Selection• Systematic checks• Results• Conclusions

[see C. Di Donato, KLOE Memo 327]

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Motivations of this analysis

• BRcan probe the ss and gluonium content of • The ratio R= BRBRcan be related to

the mixing parameters and determine the mixing angle in the flavor basis P, the best parameter for a description of the mixing

• The two mixing parameter, has emerged from EPT and phenomenological analyses, in the flavor basis are equal apart from terms which violate OZI-rule

4

The data sample

• MC RAD04: the clusters are weighted using the correction by S. Miscetti, optimized to solve the bug of over number artificial accidentals; we use Spadaro-Palutan efficiency curve for clusters (thanks to Simona G.)

• DATA: 2001-2002 run # 17874-26965

Lint=427 pb-1

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Signal & Background

• Two channel can contribute to the signal

[BRPDG= (6.2±0.7)·10-5]

with(charged [BR=(13.9±0.5)%])

with(neutral [BR=(4.6±0.3)%])

• Background: KSKL

KS KL

KS KL

KS KL

Process S/B

KS KL 2.3·10-4

KS KL 9 ·10-4

KS KL 3.4 ·10-2

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Trigger, Filfo and EVCL give a first level selection:• Trigger efficiency very high: 99.7% (crg); 99.9%(ntr)• Filfo efficiency for triggered events: 100%• EVCL efficiency for triggered events: 57.9% (crg);

61.45% (ntr)

Effects on the analysis• Trigger: 100%• EVCL: 99.07% (crg); 97.03% (ntr)

Ecap West Ecap West

First level selection:

Barrel Barrel

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Sample preselection and kinematic fit

Acceptance cut: • 7 neutral clusters in time window, |Tclu-Rclu/c| <

min(5T,2ns ), with Eclu > 10 MeV and clu> 21º

• One charged vertex near IP cm & |z| cm

with two opposite charged tracks

Kinematic fit: • requiring 4-momentum conservation and the promptness

of ’s ( TcluRclu/c = 0 )

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Analysis cut1. 2/Ndf< 4.54

2. KtagVeto: no double writing stream events, but only radiative one reject events from neutral kaon stream as KS KL

and KS KL

3. Eclu>20 MeV reject events from KS KL

4. cos0.84 reject events from multi-photons final state

events with photon conversion

Process KS KL KS KL KS KL

BR (4.8±0.1)% (1.28±0.03)% (3.36±0.10)·10-4

9·10-7 0.9·10-5 30·10-5

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The study of the ratio N/to choose the cut

2/Ndf cut

MC data

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Eclu>20 MeV reject events from

KS KL

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cos0.84

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The events

rad…radrad

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The events

From M(to M(invariant masssysstatN 28613405

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Signal

• We select also decay [BRPDG=(1.301±0.024)%]

with we havein the final state.It’s background free

We start from the selection done by F.A. and F.P.:• one prompt neutral cluster with 320MeV< E< 400 MeV and

EE< 550 MeV;

• same selection as for ;

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Trigger, Filfo and EVCL give a first level selection:Effects on the analysis• Trigger: 100%• Filfo-EVCL: 99.27%

Sample preselection and kinematic fitAcceptance cut: • 7 neutral clusters in time window, |Tclu-Rclu/c| < min(5T,2ns ),

with Eclu > 10 MeV and clu> 21º

• No tracks from IP

Kinematic fit: • Requiring 4-momentum conservation and the promptness of ’s

( TcluRclu/c = 0 )

A normalization sample:

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The events

radradrad

E (MeV) M (MeV)

statN 13001665000

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Systematic checks

• Filfo-EVCL: data selected from raw without Filfo-EVCL

• TRK-VTX: data from raw filtered with filfo/par=1 to select a sample for study of , the control sample to check efficiency

• Check of MonteCarlo stability

• Uncertainty on the 2/Ndf cut

• Correction due to interference between amplitudes A() and A()

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Filfo-EVCL• Using 40pb-1 selected with a minimum bias procedure and

without EVCL and Filfo (see kloe memo 365) we measure the efficiency on data

008.1010.1

%197

%10.088.97

MC

EVCLFlf

EVCLFlf

data

EVCLFlf

EVCLFlf

ntrcrg

EVCLFlf

ntr

EVCLFlf

crgEVCLFlf

EVCLFlf

BRBR

ntrBRcrgBR

•With KtagVeto(EVCL)•With E++E-<500MeV

1% from efficiency evaluation as systematic contribution to the uncertainty

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TRK efficiency

• Cut on clusters Eclu<400 MeV

• 2 prompt neutral clusters clu>25° & Eclu>50 MeV

• |M– M|<20 MeV

• 2 clusters 0.8<<0.95 & Eclu>100 MeV

• one track trk>40° & 200MeV<Ptot<400 MeV

We look if there is a track in a cone of 35° around Pmiss

trkmiss PPPPP

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TRK efficiency

+ MC

+ Data

Background contamination at level of 1%

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TRK efficiency

trk(Data)/trk(MC)

= 0.992±0.003

1%

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VTX efficiency

• Cut on clusters Eclu<400 MeV

• 2 prompt neutral clusters clu>25° & Eclu>50 MeV

• 100MeV < M< 170 MeV

• two tracks trk>40° & 50MeV<Ptot<400MeV

• 850 MeV<Etot<1200MeV

We look for a vertex as a function of the minimum momentum

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VTX efficiency

+ MC

+ Data

Background contamination at level of 1.5%

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VTX efficiency

vtx(Data)/vtx(MC)

= 0.990±0.001

1%

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Check of MonteCarlo stability

check amount

1 -1.32% -0.99% +0.006 0.4%

EMeV

+0.14%

-0.16%

+0.07%

-0.11%. 0.14%

check N/N/

2/Ndf ± 1 1.5%

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Interference between amplitudes A() and

A()• Has been evaluated in the Born approximation

• Take into account also radiative corrections at the cross section

2

2

2

3

3

23

3

12

AA

AAK

q

sq

s

mB

sD

es

V V

VVP

iV

V

01.095.0

01.194.0

K

KKK radBorn

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Interference between amplitudes A() and

A()

01.094.0 BornK

Krun

s

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Results

000

000

BRBRBR

BRBRBR

nrt

crg

KBRBR

BR

N

N

BR

BRR

ntrcrgdata

data

MC

MC

03

01.095.0

01.001.1/

;09.043.2/

;13001665000;28613405

K

BRBR

NN

datadata

systMCMC

statsysstat

RBVTXTRK 2

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Results

5

3

1028.012.024.6

10)20.009.079.4(

BR

R sysstat

5

3

1028.012.024.6

10)20.009.079.4(

BR

R sysstat

Source Syst. Err.

Filfo-Evcl 1%

TRK 1%

VTX 1%

Back. Sub.

0.1%

/´ 0.4%

2 1.5%

BR” 3%

K 1%

total 4%

Previous KLOE results: Phys. Lett. B541 (2002) 45-51

Systematics are dominated by knowledge of ’ branching ratios

5

3

1043.061.010.6

10)31.047.070.4(

BR

R sysstat

5

3

1043.061.010.6

10)31.047.070.4(

BR

R sysstat

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Pseudoscalar mixing angle

Using the Bramon approach [A.Bramon et. al. Eur. Phys. J. C7, 271(1999)]

we extract mixing angle:

• stat. uncertainty: mc extraction of R with Gaussian distribution

• syst. unc.: mc extraction of R with flat distribution

• th. unc.: difference between angle extractions using different values for parameters.

thsysstatP 6.07.03.04.41

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2

2sin

tan1cot

p

p

Z

Z

m

m

BR

BRR

P

V

S

NSsP

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Stat. and syst. uncertainty• Monte Carlo extraction of R with Gaussian distribution using the

statistical error as sigma and then evaluating the 68% confidence interval on P

• Monte Carlo extraction of R with flat distribution R±R; we get a flat distribution of P and we take the systematic as the half interval of the distribution

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Theoretical uncertainty

• VP Wave function overlaps [A.Bramon et. al. Phys. Lett. B503, 271

(2001)]: ZNS=0.91±0.05; ZS=0.89±0.07;

ZNS/ZS =1.02±0.10 ±10%

maximum variation P =±0.3º

• ms/m= (1.24-1.45)

maximum variation P=±0.5º

Theo. unc. P=±0.6º

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2

2sin

tan1cot

p

p

Z

Z

m

m

BR

BRR

P

V

S

NSsP

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Gluonium contentThe meson is a good candidate to have a gluonium content

Gluonium content means

We have 3 constraint in the plane:

1

|||2

1

222

ZYX

glueZssYdduuX

122 YX G

PG

PG

Z

Y

X

sin

coscos

sincos

cos

cos3

259

1

2

3

22

22

23

0

Y

Xm

m

mm

mmZ

Yf

fX

m

m

V

NS

s

q

XY

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Gluonium contentWe have 3 constraint

We published in 2002

008.0004.0750.0

04.062.0

02.075.025

Y

X

Yf

fX

s

q

06.093.022 YX

09.006.0

22 94.0 YX

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Gluonic content of´

Present situationBR(´→) measured by KLOE

with 2.5 fb1 (stat. error only)

Another constraint on the Y2-X2 ´ plane can be added by measuringthe decay ´→ [Kou PRD 63 (2001) 54027]

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Conclusions

• 2001-2002 data analysis in kloe memo 327

• All checks asked by referee has been done

• Agreement with published branching ratio

• We get a very accurate measurement of the BRand the determination of pseudoscalar mixing angle with uncertainty less then 1º

• The work is over

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Conclusions II

• Theoretical error to K dominated by

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Acknowledgement

• Mille grazie ai miei referee Simona e Paolo che oltre a verificare il mio lavoro, mi hanno aiutata a chiudere l’analisi e il memo.

• Grazie a Stefano, Matteo e Tommaso per il loro contributo per la parte di clustering, a Federico per la selezione da raw dei e a Fabio per i suggerimenti nello studio del contenuto gluonico e non solo

• Grazie a Tiziana per il suo sostegno e a Chiara che questa notte mi ha fatto dormire un po’ più del solito

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Background evaluation

The background study required an huge amount of events: an ad hoc production has been done with run condition from 2000 data

On the other hand we have the MC production with the simulation of right run condition

Systematics due to background subtraction has been evaluated from comparison between results from official MC w.r.t. the ad hoc production:

Background at level of 8.5% for official MC

Background at level of 9.2% for ad hoc production

We say that the background is at level of (9.2±0.7)%, which means, for the analysed sample, Nbg = 345 ±6stat ±28syst

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What we measure?

The ratio of the two branching ratio:

KBRBR

BR

N

N

BR

BRR

ntrcrg

03

RBN

NBR

000

000

BRBRBR

BRBRBR

nrt

crg

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