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KLOE GM Capri 23-25 May 2003 K charged status report DE/Dx development vs PiD (next talk by E.De Lucia) →K e3 studies: initial design of efficiency measurement from data →K l4 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

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KLOE GM Capri 23-25 May 2003 K e3 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 ± ± 0 0 analysis. We started to develop methods to extract efficiency and systematics for the other steps (possibly from the data)

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KLOE GM Capri 23-25 May 2003 K e3 :tracking & vertex efficiency We study a method to measure on data the efficiency to identify a K charged decay in the DC: decay = track K x track daughte r x vert in different kinematical region of the Ke3 spectrum using other K ± decay with overlapping spectrum p(MeV/c) K l3 ( segnale ) K + K + 0 0 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

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KLOE GM Capri 23-25 May 2003 K e3 : decay @ low charged momentum by meand of ’s Tof (K ± 00 00 K tag tt tt tt 00 00 tt tt tt tt ±± In the K ± 0 0 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 k e3 spectrum few pb r vertex (cm) Dx vertex (cm)

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KLOE GM Capri 23-25 May 2003 00 tt tt ±± tt K tag tt pKpK pKpK K e3 : 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 E cl > 50 MeV The 4 ’s Tof method cannot be applied to the high end of the K e3 → 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. t0t0

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KLOE GM Capri 23-25 May 2003 K e3 : 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 K e3 : decay & K momentum extrapolation position resolution

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KLOE GM Capri 23-25 May 2003 K e3 : 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 tt Ehm.. failed fit with 2 gaussian !!

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KLOE GM Capri 23-25 May 2003 K e3 : 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

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KLOE GM Capri 23-25 May 2003 K e3 : 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 momentum Reject the k l3 decay using the position and the time of the 4th cluster ( should be the charged one…) Dpx ± (Mev/c) 00 tt tt ±± tt K tag tt pKpK pKpK p0p0 p ± = p K - p 0 To be continued…..

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KLOE GM Capri 23-25 May 2003 K e3 : possible Pid for e ± P* (MeV/c) Mass from ToF (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.

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KLOE GM Capri 23-25 May 2003 BR(K 0 0 ) Update of BR(K 0 0 ) 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 to better take into account the effect of nuclear interactions.

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KLOE GM Capri 23-25 May 2003 Results and conclusions BR(K 0 0 ) = ( 1.781 0.013 stat 0.016 syst )% KLOE Memo # 279 KLOE Note # 187 A preliminary version of the draft is ready PDG fit 2002: (1.73 0.04)% Event yield N ’ ( 0 tag ) =30798±100, N °tag =(1275±4) 10 3 N ’ ( tag ) =52253±230, N tag =(1992±4) 10 3 L int = 441 pb –1

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KLOE GM Capri 23-25 May 2003 The K e4 ’ decay analysis PDG PDG: BR = (2.1 0.4) 10 –5 Ljung 73 2 evts /K e3 + Bolotov 8625 evts /K e3 – Barmin 8810 evts /K + all Very preliminary The Ke4’ BR can be measured using the absolute t’ BR obtained at KLOE and measuring the Ratio: (K e4 ’) / ( ’) K e4 ’ K e 0 0 e ’ K 0 0

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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 t2v<50 cm Helix distance between the two tracks’ first/last hit and V: t2v<50 cm 4 “ontime” neutral clusters with E i >15 MeV, such that: t ij | t i –t j –(r Vi –r Vj )/c |<4 t (E i,E j ) t ij <10 ns t ij | t i –t j –(r Vi –r Vj )/c |<4 t (E i,E j ) i,j=1,..,4 and t ij <10 ns Pairing of the two 0 ’s by minimizing ij [ (m ij – m ° )/ m ° ] 2 80 MeV < m 12, m 34 < 190 MeV 4 LEVEL Preselection : 4 LEVEL 0000 Ch track

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KLOE GM Capri 23-25 May 2003 ’ ’ selection |p dau | < 135 MeV |p dau | < 135 MeV in K ± frame 450 MeV < m 3 < 540 MeV KPP0P0FIT based on 6 contributions: E, p, s 0. 2 ’ /6 < 5 2 ’ /6 < 5 s 0 (s 1 +s 2 +s 3 )/3, s i (p K – p i ) 2 K e4 ’ K e4 ’ selection A cluster associated to the daughter track |s 0 ( ’ hyp.) – 10 5 MeV 2 | < 8 10 3 MeV 2 KEP0P0NUFIT based on: E conservation in mass hypothesis, missing mass 0, daughter: p/E 1, daughter: t.o.f. compatible 2 e4’ /4 1

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KLOE GM Capri 23-25 May 2003 Measuring BR(K e4 ’) N obs = selected events in the final K e4 ’ sample N bckg = background events expected in the final data sample N ’ = finally selected ’ events ’ = background contamination in ’ events 4 LEVEL trig, filt, K, vtx, clu = “ 4 LEVEL ” efficiencies for K e4 ’ and ’ events ’ 135 = cut |p dau |<135 MeV in K frame, m hyp. ’ K e4 ’ ac = e ± track-to-cluster efficiency K e4 ’ fit x = kinematic fit efficiency x = ’, K e4 ’ BR( ’) = ( 1.781 0.013 stat 0.016 syst )% KLOE note # 187 From ’ ~ 1 at %1 (MC check) new

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KLOE GM Capri 23-25 May 2003 Data : 441 pb –1 (June 2001 – September 2002) Data and Monte Carlo samples MC : 2.6 10 7 all (~9 pb –1 ) 2.0 10 5 K + K –, K ± e ± 0 0 e,K Ŧ all (~3.2 fb –1 ) 2.0 10 7 K + K –, K ± ± 0 0,K Ŧ all (~380 pb –1 ) 1.2 10 7 K + K –, K ± e ± 0 e,K Ŧ all (~82 pb –1 ) 1.2 10 7 K + K –, K ± 0, e 0 e, 0 (~100 pb –1 )

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KLOE GM Capri 23-25 May 2003 K e4 ’ K e4 ’ efficiencies Kinematic fit (MC) e track to cluster association = 0.359 0.011 = 0.359 0.011 ac (p e ) obtained from K e3 and integrated over p e distribution in K e4 ’’ fit e4’ = 0.237 0.006 Systematics include the choices of the 2 e4’ cut and definitions. The efficiency includes the effect of the s 0 cut (in ’ hyp.) : (98 1)%

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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 K 2 K l3 5 K 2 and K l3 : 5 evts ’ = 0.6 0.1 % ’ = 0.6 0.1 % K2K2 – K2K2 – 10 7 ––– K e3 – 3333 – 6464 K3K3 –<3– 9595 <4 ’’ 43 1019 6424216 511 5 2.2 1.5 K2K2 K2K2 K e3 K3K3 ’’ N bckg = 120 17 N bckg = 152 18 N bckg ( ’) = 117 15 (MC and Data) N bckg (non- ’) = 35 9 (MC and Data)

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KLOE GM Capri 23-25 May 2003 Preliminary results tot ’ / tot e4’ = 4.80 0.03 BR(K e4 ’) = (2.43 0.20 stat 0.22 syst ) 10 –5 PDG fit PDG fit: (2.1 0.4) 10 –5 Barmin 88 Barmin 88: (2.54 0.89) 10 –5 N obs = 407 20 N bckg = 152 18 N ’ = 899020 950 6300 N sig = 255 27 VERY PRELIMINARY NO DE/Dx applied !!!

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KLOE GM Capri 23-25 May 2003 Summary and ’ analysis finalized K e3 analysis started K l4 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 vertex 3 pb -1 sample Capri analysis

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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 PhD thesis Analysis status will be reported (July) in PhD thesis Studies on the charged kaon decays K 0 0 and K e 0 0 e ( e ) with the KLOE experiment –

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KLOE GM Capri 23-25 May 2003 4 LEVEL 4 LEVEL efficiencies (I) Trigger (Data) Event Classification (MC) filt ’ / filt e4’ = 1.006 0.011 trig ’ / t rig e4’ = 1.02 0.02 0.01 MC Kaon identification (MC) K ’ / K e4’ = 0.992 0.013 trig ’ / trig e4’ |1 – trig ’ / trig e4’ | < selftrig ’ / selftrig e4’ |1 – selftrig ’ / selftrig e4’ |

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KLOE GM Capri 23-25 May 2003 4 LEVEL 4 LEVEL efficiencies (II) Vertexing (MC) Clustering (MC) vtx ’ / vtx e4’ = 1.016 0.005 clu ’ / clu e4’ = 1.007 0.007 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’’

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KLOE GM Capri 23-25 May 2003 ’ ’ efficiencies 135 = 0.972 0.002 |p dau |<135 MeV requirement Kinematic fit (Data and MC) fit ’ = 0.403 0.002 Computed on data at 4 LEVEL ( 99.3% ’ ) Includes the cut on m 3 Already studied for ’ in KLOE Note # 187

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