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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.

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Presentation on theme: "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."— Presentation transcript:

1 KLOE GM Capri 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

2 KLOE GM Capri 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)

3 KLOE GM Capri 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

4 KLOE GM Capri May 2003 K e3 :  low charged momentum by meand of  ’s Tof (K   ±      00 00 K  tag tt tt tt 00 00 tt tt tt tt ±± 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)

5 KLOE GM Capri May 2003 00 tt tt ±± tt K  tag tt pKpK pKpK K e3 :  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

6 KLOE GM Capri 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

7 KLOE GM Capri 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 tt Ehm.. failed fit with 2 gaussian !!

8 KLOE GM Capri 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

9 KLOE GM Capri 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) 00 tt tt ±± tt K  tag tt pKpK pKpK p0p0 p  ± = p K - p  0 To be continued…..

10 KLOE GM Capri 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.

11 KLOE GM Capri 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 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.

12 KLOE GM Capri May 2003 Results and conclusions BR(K     0  0 ) = (  stat  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

13 KLOE GM Capri 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

14 KLOE GM Capri 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 0000 Ch track

15 KLOE GM Capri 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  

16 KLOE GM Capri 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(  ’) = (  stat  syst )% KLOE note # 187 From  ’ ~ 1 at %1 (MC check) new

17 KLOE GM Capri 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 )

18 KLOE GM Capri May 2003 K e4 ’ K e4 ’ efficiencies Kinematic fit (MC) e  track to cluster association =  =   ac (p e ) obtained from K e3 and integrated over p e distribution in K e4 ’’  fit e4’ =  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)%

19 KLOE GM Capri 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 % K2K2 – K2K2 – 10  7  ––– K e3 – 3333 – 6464 K3K3 –<3– 9595 <4 ’’ 43  1019  6424216  511   1.5 K2K2 K2K2  K e3 K3K3 ’’ N bckg = 120  17 N bckg = 152  18 N bckg (  ’) = 117  15 (MC and Data) N bckg (non-  ’) = 35  9 (MC and Data)

20 KLOE GM Capri 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  ’ =  950  6300  N sig = 255  27 VERY PRELIMINARY NO DE/Dx applied !!!

21 KLOE GM Capri 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

22 KLOE GM Capri 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 –

23 KLOE GM Capri May  LEVEL 4  LEVEL efficiencies (I) Trigger (Data) Event Classification (MC)  filt  ’ /  filt e4’ =   trig  ’ /  t rig e4’ = 1.02  0.02  0.01 MC Kaon identification (MC)  K  ’ /  K e4’ =   trig  ’ /  trig e4’ |1 –  trig  ’ /  trig e4’ | <  selftrig  ’ /  selftrig e4’ |1 –  selftrig  ’ /  selftrig e4’ |

24 KLOE GM Capri May  LEVEL 4  LEVEL efficiencies (II) Vertexing (MC) Clustering (MC)  vtx  ’ /  vtx e4’ =   clu  ’ /  clu e4’ =  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’’

25 KLOE GM Capri May 2003  ’  ’ efficiencies  135 =  |p dau |<135 MeV requirement Kinematic fit (Data and MC)  fit  ’ =  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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