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Charged Kaons Analysis

KLOE Elba Meeting 23-25/05/2001. Charged Kaons Analysis. http://www.fisica.unile.it/~ventura. Ratio K ±  ±  0 / K ±  ±  K ± Life Time K ±  0 e ±  Branching Ratio K ±  ±  0  0 Branching Ratio K ±  ±  +  – Branching Ratio. Introductory notes.

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Charged Kaons Analysis

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  1. KLOE Elba Meeting 23-25/05/2001 Charged Kaons Analysis http://www.fisica.unile.it/~ventura Ratio K±±0/K±± K± Life Time K±0e± Branching Ratio K±±00 Branching Ratio K±±+– Branching Ratio

  2. Introductory notes • Experimental Data collected can ensure • small statistical errors on measurements. • There are some MC–Data mismatches • and several technicalities which need to • be taken into account in order to improve • measurements and understand systematics.

  3. Ratio K±±0/K±± M. Martemianov , V. Kulikov • World Data • 0.3331  0.0028 (fit), 0.3316  0.0032 (average) (PDG) • 0.339  0.007  0.007 (CMD-2 preliminary, 2000) • 0.3329  0.0047 (USHER - 1992) • 0.3355  0.0057 (WEISSENBERG - 1976) • 0.305  0.018 (ZELLER - 1969) • 0.3277  0.0065 (AUERBACH - 1967)

  4. Cuts on momentum distribution of secondary particles -peak : 225 MeV/c < PCM < 245 MeV/c -peak : 195 MeV/c < PCM < 215 MeV/c  + – , e±0 ± 0,  0 0 K K0 Corrections for K

  5. Main problem for K± tracks Kaon track splitting (15 %) • RED - momentum distribution of secondary particles from KINE bank, if presents vertex from DVFS bank, MC data • PINK - momentum distribution of secondary particles from DVFS bank, MC data

  6. Wrong secondary vertex association Correct Vertex

  7. Corrections for wrong vertex selection | PK - Psec | < 40 MeV 0.14 < | – |K - sec| | < 3.0

  8. oand Branching Ratios (preliminary estimation) • 0 • Exp. ratio = 0.19160.0006 • MC ratio = 0.19720.0024 • Exp. data corrected by MC = • = 0.20560.0026 (stat.) + (?) (sys.) •  • Exp. ratio = 0.55870.0011 • MC ratio = 0.57880.0047 • Exp. data corrected by MC = • = 0.61300.0050 (stat.) + (?) (sys.) • 0/ • = 0.33060.0012(stat.) + (?) (sys.)

  9. Other tasks • Estimation of trigger efficiency • Background / track reconstruction dependency • Investigations of systematic errors

  10. K± Life Time A. Ventura , E. Gorini , M. Primavera • World Data (in ns) • 12.386  0.024 (fit), 12.385  0.025 (average) (PDG) • 12.451  0.030 (KOPTEV - 1995) K at rest • 12.368  0.041 (KOPTEV - 1995) K at rest • 12.380  0.016 (OTT - 1971) K at rest • 12.272  0.036 (LOBKOWICZ - 1969) K in flight • 12.443  0.038 (FITCH - 1965) K at rest

  11. Advantages and problems in K±measurement • Large K± statistics • Good momentum and spatial resolution • Wide fit region (~30 ns) • Systematics independent from trigger, event classification, timing (?) • Few information at r < 25 cm • Energy losses • Fake 2-tracks vertices

  12. K track requirements and cuts • K+K– events selection and • K± tracks identification with KPMFILT filter • CALO + Cosmic Veto trigger • K decay vertex at rV>25 cm (2tracks) • Kaon track “refit” in K mass hypothesis • fake vertices rejection (  angle + |p| cuts) •  vertex at rV<5 cm • | pK – 127 | < 13 MeV/c ( frame)

  13. K path length V A  DVFS* B  DHIT* C  DTFS D  DVFS xy view D L C O :  vertex P : DC walls crossing F : track first hit L : track last hit V : K± decay vertex A B F O P

  14. Time of flight distributionson MC • Times converted • in K rest frame MCpro: Geanfi MCrec: DataRec MC pro MC rec t (ns)

  15. K time distributionsMC – Datacomparison Data MC # MC # Data t (ns)

  16. Efficiencye(t) of K± selection on MC t (ns) 12 ns  28+45 cm Fiducial region=[12,40] ns 40 ns  28+210 cm

  17. Normalized K time distribution # Data / e(t) 17.5 pb–1 (end 2000) • (ns)=12.40±0.08 (stat)+(?)(sys) t (ns) supposing de=0stat  0.030 ns

  18. Facing systematics and beyond • Momentum • Spatial •  dependency on K decay channel to be tested } resolutions and offsets vst • CPT measurement ? :

  19. K±0e± Branching Ratio B. Sciascia • World Data ( 10 -2 ) • 4.82  0.06 (fit), 4.85  0.09 (average) (PDG) • 4.86  0.10 (CHIANG - 1972) • 4.7  0.3 (SHAKLEE - 1964) • 5.0  0.5 (ROE - 1961)

  20. K±±0tagging • K+K– events selection and • K± tracks identification with KPMFILT filter • K decay vertex(2tracks) • |psec – 205| < 10 MeV/cat decay vertex(K frame) • at least 2 neutral clusters in EMC • back to back neutral clusters (0 frame) • (* selection) • recovering of splitted clusters }± } 0

  21. K±±0tagging Momentum of secondaries (K frame in m hypothesis) 0 mass in K0 tag =132Mev/c2 =5Mev/c2 =205Mev/c =2Mev/c

  22. Efficiencies after K±±0 tagging

  23. K±±selection Momentum of secondaries (K frame in m hypothesis) ( pmissc – Emiss ) vspsec =235Mev/c =3Mev/c • |pmissc – Emiss|< 10 MeV Efficiency of K selection ~30% (from MC)

  24. K±±0selection Momentum of secondaries (K frame in m hypothesis) 0 mass for K0 signal =205Mev/c =3Mev/c =133Mev/c2 =18Mev/c2 • |psec – 205| < 10 MeV/c • at least 2 neutral clusters ( from tag) • * selection • recovering of splitted clusters Efficiency of K0 selection ~20% (from MC)

  25. K±0l±selection 0 mass for K0l signal • No K nor K0 • selection • K decay track (lepton) • at least 2 neutral clusters • ( from tag) • (Tcl1 – L1/c) – (Tcl2 – L2/c) minimum • recovering of • splitted clusters =131Mev/c2 =20Mev/c2

  26. K±0e±and K±0± ml2obtained imposing 0 = T me  m ml2 < 6000 MeV2Ke3 ml2 > 6000 MeV2K3 ml2 Efficiency of Kl3 selection ~ 4–8 % (from MC)

  27. K±±00 Branching Ratio C. Lecci , E. Gorini , M. Primavera • World Data ( 10 -2 ) • 1.73  0.04 (fit), 1.77  0.07 (average) (PDG) • 1.84  0.06 (CHIANG - 1972) • 1.53  0.11 (PANDOULAS - 1970) • 1.8  0.2 (SHAKLEE - 1964) • 1.7  0.2 (ROE - 1961)

  28. Preliminary cuts • K+K– events selection and • K± tracks identification with KPMFILT filter • CALO + Cosmic Veto trigger • at least 4 neutral clustersin EMC • K decay vertex atrV>40 cm (2tracks) • fake K±K± , ±± vertices rejection (angle cut) Kinematical cuts • |p| < pmax at decay vertex (K frame) • 2 on-time clusters couples with inv. mass  [100,170] MeV/c2 • Momentum-Energy conservation in decay vertex • |pT| < 50 MeV/c , |E| < 50 MeV

  29. Correct 2 vertex selection Rejected for high ± momentum

  30. K±-± Charged Vertices(MC r vs z distributions) Wrong charge Vertex K±- Correct Vertex K±-±

  31. Momentum distribution of secondary particles (K frame) Data MC Data MC 4 clus, rv>40cm, no FakeVtx + Kinematical cuts 4 clus, rv>40cm

  32. K±±00 physical topics g1+g2fitperformed =490.5 MeV/c2 =19 MeV/c2 1=131.5MeV/c2 1=18MeV/c2 1=130.5MeV/c2 1=16MeV/c2 =488.9 MeV/c2 =19 MeV/c2 Invariant mass of selected clusters couples Invariant mass of selected secondary particles triplets

  33. Statistics analized Experimental Data Selection: 1099682 K± , 869 K±±00 3.16 pb-1(July 2000, DBV4) Selection: 299880 K±, 347 K±±00

  34. Selected Kaons on MC

  35. ±±00Branching Ratio (very preliminary estimation) * ** *Background contamination subtracted (~0.3% in MCpreliminary) **0.34% subtraction KPMFILT selecting nonK+K– events (MC)

  36. Present studies and future plans • Understand the disagreement with PDG results • and look for systematics (background,trigger,EVCL,MC-Data,…) • Possible tagging with K±± • Dalitz plots’ parameters for K+,K– & asymmetries(?)

  37. K±±+– Branching Ratio V. Casavola , E. Gorini , M. Primavera • World Data ( 10 -2 ) • 5.59  0.05 (fit), 5.52  0.10 (average) (PDG) • 5.34  0.21 (PANDOULAS - 1970) • 5.71  0.15 (DEMARCO - 1965) • 6.0  0.4 (YOUNG - 1965) • 5.54  0.12 (CALLAHAN - 1964) • 5.1  0.2 (SHAKLEE - 1964) • 5.7  0.3 (ROE - 1961)

  38. Preliminary cuts • K+K– events selection and • K± tracks identification with KPMFILT filter • CALO + Cosmic Veto trigger • at least 4 tracks apart from identified Kaon track(s) • K decay vertex at rV>40 cm (4tracks) Kinematical cuts • Charge conservation in decay vertex • Momentum-Energy conservation in decay vertex • |p| < 40 MeV/c , |E| < 30 MeV

  39. Wrong 4 vertex association Fake 4 Vertex (other K)

  40. K±±+– physical topics Data MC Data MC 85MeV/c 85MeV/c =493.6 MeV/c2 =0.9 MeV/c2 =494.2 MeV/c2 =1.2 MeV/c2 Momentum of selected secondary particles Invariant mass of selected secondary particles triplets

  41. Present statistics Experimental Data Selection: 1099682 K± , 1075 K±3 3.16 pb-1(July 2000, DBV4) Selection: 299880 K±, 352 K±3

  42. Selected Kaons on MC

  43. ±±+–Branching Ratio (preliminary estimation) * ** *Background contamination negligible (<0.3% from MC) **0.34% subtraction KPMFILT selecting nonK+K– events (MC)

  44. Present investigations and perspectives • Comprehension of incompatibility with PDG results • and study of systematics (trigger efficiency,EVCL,MC-Data,…) • Optimization of fake vertices rejection • Possible tagging with K±±0 • Dalitz plots’ parameters & asymmetries(?) • Background rejection in K±e4 , K±4 channels

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