KLOE GM Capri 23-25 May 2003

K charged status report

• DE/Dx development vs PiD (next talk by E.De Lucia)

→ Ke3 studies: initial design of efficiency measurement from data

→ Kl4 analysis skeleton

→ K± ± analysis refinement

• Improvement of kk by means of K± ± (already presented by

M.Dreucci on Friday)

• K studies: kk by means of K± and Br(K)/Br(K)

(very early stage yet)

P.Branchini, E.De Lucia, P.De Simone, E.Gorini, A.Ferrari M.Martemianov, L.Passalacqua, M.Primavera, B.Sciascia, A.Ventura, R.Versaci, V.Patera

KLOE GM Capri 23-25 May 2003

Ke3 analysis steps:

K decay vertex

0 in EMC

Triggering tag on one side

e± id :ToF,Kin,De/Dx

The first and the third steps have been studied in the context of the KK and K± ±00 analysis.We started to develop methods to extract efficiency and systematics for the other steps (possibly from the data)

KLOE GM Capri 23-25 May 2003

Ke3 :tracking & vertex efficiency

We study a method to measure on data the efficiency to identify a K charged decay in the DC:

decay= trackKx track

daughter x vert

in different kinematical region of the Ke3 spectrum using other K± decay with overlapping spectrum

p(MeV/c)

Kl3 (segnale)

K+

K+00

K+0

fit tracce + vertice

The aim is to select a sample of events where the vertex in the DC can be detected by means of ECAL quantities. We select a sample of tagged events and look at the other side

KLOE GM Capri 23-25 May 2003

Ke3: decay @ low charged momentum by

meand of ’s Tof (K±

0

0

K tag

tt

t

0

0

K tag

tt

t

t

±

In the K±00 decay, the times of the 4 clusters from 2 0 give the decay vertex position with fair accuracy

The method has been successfully used in K analysis but has low efficiency and gives only the

integrated decay on the low end of ke3 spectrum

few pb r vertex (cm)

Dx vertex (cm)

KLOE GM Capri 23-25 May 2003

0

t

t

±

t

K tag

t

pK

pK

Ke3: decay @ high momentum with K

momentum extrapolation (K±

From the tag side by means of extrapolation of the Kaons momentum with we obtain:

Timing of the signal K in the DC Position of the signal K in DC Momentum of the signal K in the

DC

Only events with 4 clusters and Ecl > 50 MeV

The 4 ’s Tof method cannot be applied to the high end of the

Ke3 → only one 0 !

We are exploring the possibility to use the info from the tag side. A REFINED DE/DX (!!) is required by K crossing the DC wall and BP.

t0

KLOE GM Capri 23-25 May 2003

Ke3: decay & K momentum extrapolation

position resolution

~ 4 pb-1 ; 2002 data

< 1 cm

Dx at first hit (cm)

Dr at first hit (cm)

The check on the resolution achieved on the extrapolated position of the signal K has been made on double tag event (K→-K→0). The extrapolation from the tag side is compared with the fitted position and momentum of the signal (0) kaon at first hit in DC.

Tails are expected mainly due to Landau fluctuations in dc wall energy loss

Ke3: decay & K momentum extrapolation

position resolution

Ke3: decay & K momentum extrapolation

position resolution

KLOE GM Capri 23-25 May 2003

Ke3: decay & K momentum extrapolation

momentum resolution

The extrapolation can be further optimized. Up to now it has been made using solenoidal constant B field…Must be taken into account that errors on signal K momentum and position are correlated.

Dp at first hit (MeV/c)

Dpx at first hit (MeV/c)

D at first hit (deg)

= 6 Mev/c

= 4 Mev/c

t

Ehm.. failed fit with 2 gaussian !!

KLOE GM Capri 23-25 May 2003

Ke3: decay & K momentum extrapolation: vertex resolution

The unknown decay path of the signal K along the extrapolated helix can be found imposing the consistency on the 0 invariant mass, on the K and s tof. Found the vertex, the cluster energy and position gives the 0 momentum. Then, with the K momentum at the vertex we obtain the ± momentum.

Dr vertex (cm)

Dx vertex (cm)

Z (cm)

R (cm)

Vertex position

KLOE GM Capri 23-25 May 2003

Ke3: decay & K momentum extrapolation: ± momentum resolution

The results obtained are based on a toy 2 evaluation without using the info from the charged cluster:Starting point for a fit constrained.

good resolution on p± is needed to:

Correctly evaluate the decay with

respect of charged pion momentumReject the kl3 decay using the position and the time of the 4th cluster ( should be the charged one…)

Dpx ± (Mev/c)

0

t

t

±t

K tag

t

pK

pK

p0

p± = pK - p0

To be continued…..

KLOE GM Capri 23-25 May 2003

Ke3 : possible Pid for e±

P*

(MeV

/c)

Mass

fro

m T

oF

(Mev**

2)

Possible strategies for electron ID relies on kinematic cuts, Tof, De/dx , different behaviour in ECAL ( see M.Testa talk) or a mixture of some of them.The approach is to use an ECAL based separation method to extract the signal and a DC driven separation method to check systematics, or vice versa with no use of MC.For more details on possible use of DE/Dx I refer to Erika presentation.

KLOE GM Capri 23-25 May 2003

Update of BR(KBR(K0000)) analysis

The work done until December 2002 (112 pb–1) was reported in full detail in KLOE Memo # 279 Referee’s comments have brought to revise some of the requirements/techniques used in the analysis. A larger data sample (all 2001-02 statistics) has been used 1) to improve final uncertainty ; 2) to avoid statistical correlations between control samples. Now 240 out of 411 pb-1 are now used for the control samples and the rest for the signal measurement. The control sample for estimating K has been

redefined tobetter take into account the effect of nuclear

interactions .

KLOE GM Capri 23-25 May 2003

Results and conclusions

BR(K00) = (1.781 0.013stat 0.016syst)%

KLOE Memo # 279 KLOE Note # 187 A preliminary version of the draft is ready

PDG fit 2002: (1.73 0.04)%

Event yield

N’(0tag)=30798±100, N°tag=(1275±4)103

N’(tag)=52253±230, Ntag=(1992±4)103

Lint = 441 pb–1

KLOE GM Capri 23-25 May 2003

The Ke4’ decay analysis

PDGPDG: BR = (2.10.4)10–5

Ljung 73 2 evts /Ke3+

Bolotov 86 25 evts /Ke3–

Barmin 88 10 evts /K+all

132

004 sec1080.0)'( FVK use

Very preliminary

The Ke4’ BR can be measured using the absolute t’ BR obtained at KLOE and measuring the Ratio:

(Ke4’) / (’)

Ke4’ K e00e ’ K 0 0

KLOE GM Capri 23-25 May 2003

Trigger: EMC + Cosmic Veto Event Classification: kpmstream (all the 5 algo’s) A 2-track vertex V in DC volume with a K track Helix distance between the two tracks’ first/last hit

and V: t2v<50t2v<50 cmcm 4 “ontime” neutral clusters with Ei>15 MeV,

such that: ttij ij ||ttii–t–tjj–(r–(rViVi–r–rVjVj)/c)/c|<4|<4tt(E(Eii,E,Ejj)) i,j=1,..,4 and

ttijij<10<10 nsns

Pairing of the two 0’s by minimizing ij [(mij – m°)/m°]2

80 MeV < m80 MeV < m1212 , m , m3434 < 190 MeV < 190 MeV

Preselection : 44LEVELLEVEL

00Ch track

KLOE GM Capri 23-25 May 2003

’’ selection

|p|pdaudau| < 135 MeV| < 135 MeV in K± frame

450 MeV < m450 MeV < m33 < 540 MeV < 540 MeV

KPP0P0FIT based on 6 contributions: E , p , s0 .

22’ ’ /6 < 5/6 < 5 s0 (s1+s2+s3)/3 , si (pK – pi)2

KKe4e4’ ’ selection A cluster associated to the daughter track ||ss00

((’ hyp.) ’ hyp.) – 10– 1055 MeV MeV22| < 8| < 8101033 MeV MeV22

KEP0P0NUFIT based on: E conservation in mass

hypothesis, missing mass 0, daughter: p/E1, daughter: t.o.f. compatible

with e (not or ). 22e4’ e4’ /4 < 3.75/4 < 3.75 , 2

’ /6 > 1

KLOE GM Capri 23-25 May 2003

Measuring BR(Ke4’)

)'(|

|

)1()'(

'4

'

135'4

'

''4

BRN

NNKBR

efit

fit

ace

cluvtxKfilttrig

cluvtxKfilttrigbckgobse

Nobs = selected events in the final Ke4’ sample

Nbckg = background events expected in the final data sample

N’ = finally selected ’ events

’ = background contamination in ’ events

trig , filt , K , vtx , clu = “44LEVELLEVEL” efficiencies for Ke4’ and ’ events

135 = cut |pdau|<135 MeV in K frame, m hyp. ’’ac = e± track-to-cluster efficiency KKe4e4’’

fitx = kinematic fit efficiency x = ’ , Ke4’

BR(’) = (1.781 0.013stat 0.016syst)%

KLOE note # 187

From ’

~ 1 at %1 (MC check)

new

KLOE GM Capri 23-25 May 2003

Data : 441 pb–1 (June 2001 – September 2002)

Data and Monte Carlo samples

MC : 2.6 107 all (~9 pb–1)

2.0 105 K+K–, K±e±00e,KŦall (~3.2 fb–1)

2.0 107 K+K–, K±±00,KŦall (~380 pb–1)

1.2 107 K+K–, K±e±0e,KŦall (~82 pb–1)

1.2 107 K+K–, K±0, e0e, 0 (~100 pb–1)

KLOE GM Capri 23-25 May 2003

KKe4e4’’ efficiencies

Kinematic fit (MC)

e track to cluster association

<<acac> = 0.359 > = 0.359 0.0110.011

• ac (pe) obtained from Ke3 and integrated over pe distribution in Ke4’’

fitfite4’ e4’ = 0.237 = 0.237 0.006 0.006

• Systematics include the choices of the 2

e4’ cut and definitions.• The efficiency includes the effect of the s0 cut (in ’ hyp.) : (981)%

KLOE GM Capri 23-25 May 2003

Background evaluation

In 441 pb–1 the following contaminations from K+K– are expected (MC) :

Additional bckg from KK22 and KKl3l3 : 55 evts

’’ = 0.6= 0.60.1 %0.1 %

K2 –

K2 – 107

– – –

Ke3 – 33 – 64

K3 – <3 – 95 <4

’ 4310

196 42 165 115 2.21.5

K2 K2 Ke3 K3 ’

Nbckg = 12017

Nbckg = 15218

Nbckg (’) = 11715 (MC and Data)

Nbckg (non-’) = 359 (MC and Data)

KLOE GM Capri 23-25 May 2003

Preliminary results

tottot’’

//tottote4’e4’ = 4.80 = 4.80 0.030.03

BR(Ke4’) = (2.43 0.20stat 0.22syst ) 10 –5

PDG fitPDG fit: (2.10.4)10–5

Barmin 88Barmin 88: (2.540.89)10–5

NNobsobs = 407 = 407 20 20

NNbckgbckg = 152 = 152 18 18

NN’’ = 899020 = 899020 950 950 6300 6300

NNsigsig = 255 = 255 27 27

VERY PRELIMINARY

NO DE/Dx

applied !!!

KLOE GM Capri 23-25 May 2003

Summary

• and ’ analysis finalized

• Ke3 analysis started

• Kl4 analysis on the way

• Help from DC ADC’s can be there

• The K → sector must still be exploited

K = 12.8 ns PDG = 12.4ns

Tof K (ns)

K±→±0 vertex3 pb-1 sample

Capri analysis

KLOE GM Capri 23-25 May 2003

Perspectives

Increase Monte Carlo generation to improve the knowledge of background Perform data-extracted efficiencies to correct the MC predictions A KLOE memo will be ready by summer 2003

Analysis status will be reported (July) in PhD thesisPhD thesis

Studies on the charged kaon decays K 00 and K

e00e (e) with the KLOE experiment

–

KLOE GM Capri 23-25 May 2003

44LEVELLEVEL efficiencies (I)

Trigger (Data) Event Classification (MC)

filtfilt’’

//filtfilte4’e4’ = 1.006 = 1.006 0.0110.011trigtrig

’’ //ttrigrig

e4’e4’ == 1.021.02 0.020.02 0.010.01

MC

Kaon identification (MC)

KK’’

//KKe4’e4’ = 0.992 = 0.992 0.0130.013

• |1 – trigtrig’’

//trigtrige4’e4’ | <

|1 – selftrigselftrig’’

//selftrigselftrige4’e4’ |

KLOE GM Capri 23-25 May 2003

44LEVELLEVEL efficiencies (II)

Vertexing (MC)

Clustering (MC)

vtxvtx’’

//vtxvtxe4’e4’ = 1.016 = 1.016 0.0050.005

cluclu’’

//cluclue4’e4’ = 1.007 = 1.007 0.0070.007

• Small dependence of vtx on the angle between K and daughter’s directions

• The efficiencies of “ontime” and m cuts have been checked to coincide at % level for ’ and Ke4’’

KLOE GM Capri 23-25 May 2003

’’ efficiencies

135135 = 0.972 = 0.972 0.0020.002

|pdau|<135 MeV requirement

Kinematic fit (Data and MC)

fitfit’ ’ = 0.403 = 0.403 0.002 0.002

• Computed on data at

4LEVEL (99.3% ’)• Includes the cut on m3

• Already studied for ’

in KLOE Note # 187