Charged Kaons Analysis

• Ratio K±±0/K±±• K± Life Time

• K±0e± Branching Ratio

• K±±00 Branching Ratio

• K±±+– Branching Ratio

KLOE Elba Meeting 23-25/05/2001

http://www.fisica.unile.it/~ventura

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.

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)

Cuts on momentum distribution of secondary particles

K

K0

+ – , e±0± 0, 0 0

Corrections for K

-peak : 225 MeV/c < PCM < 245 MeV/c

-peak : 195 MeV/c < PCM < 215 MeV/c

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

Wrong secondary vertex association

Correct Vertex

Corrections for wrong vertex selection

| PK - Psec | < 40 MeV

0.14 < | – |K - sec| | < 3.0

o and Branching Ratios(preliminary estimation)

0

• Exp. ratio = 0.19160.0006• MC ratio = 0.19720.0024• Exp. data corrected by MC = = 0.20560.0026 (stat.) + (?) (sys.)

• Exp. ratio = 0.55870.0011• MC ratio = 0.57880.0047• Exp. data corrected by MC =

= 0.61300.0050 (stat.) + (?) (sys.)

0/= 0.33060.0012(stat.) + (?) (sys.)

Other tasks

• Estimation of trigger efficiency

• Background / track reconstruction dependency

• Investigations of systematic errors

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

• Few information at r < 25 cm

• Energy losses

• Fake 2-tracks vertices

• Large K± statistics• Good momentum and spatial resolution• Wide fit region (~30 ns)• Systematics independent from trigger,

event classification, timing (?)

Advantages and problems in K± measurement

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)

O : vertex

P : DC walls crossing

F : track first hit

L : track last hit

V : K± decay vertex

O PF

L

V

xy view

A B

C

D

K path length

A DVFS*B DHIT*C DTFSD DVFS

t (ns)

MC rec

MC pro

Time of flight distributions on MC

MCpro: Geanfi

MCrec: DataRec

• Times convertedin K rest frame

MC

Data

# MC # Data

t (ns)

K time distributionsMC – Data comparison

Efficiency (t) of K± selection on MC

Fiducial region [12,40] nst (ns)

12 ns 28+45 cm40 ns 28+210 cm

MCpro

MCrec

#

#

Normalized K time distribution

# Data / (t)

(ns)=12.400.08(stat)+(?)(sys)

supposing =0 stat 0.030 ns

t (ns)

17.5 pb–1

(end 2000)

Facing systematics and beyond

• Momentum Spatial

• dependency on K decay channel to be tested

CPT measurement ? :

}

averageKK /)(

resolutions and offsets vs t

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)

K±±0 tagging

• K+K– events selection and K± tracks identification with KPMFILT filter

• K decay vertex (2tracks)

• |psec – 205| < 10 MeV/c at decay vertex (K frame)

• at least 2 neutral clusters in EMC• back to back neutral clusters (0 frame) (* selection)• recovering of splitted clusters

} ±

} 0

K±±0 tagging

=205Mev/c

=2Mev/c

=132Mev/c2

=5Mev/c2

Momentum of secondaries(K frame in m hypothesis)

0 massin K0 tag

Efficiencies after K±±0 tagging

Requirements Data MCK± track (from EvCl) 38% 52%K± decay vertex (2tracks) 73% 79%After fake vertices rejection ( |p| cut )

90% 89%

K±± selection

Momentum of secondaries(K frame in m hypothesis)

( pmissc – Emiss ) vs psec

• | pmissc – Emiss | < 10 MeV

Efficiency of K selection ~30% (from MC)

=235Mev/c

=3Mev/c

K±±0 selectionMomentum of secondaries

(K frame in m hypothesis)0 mass

for K0 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 K0 selection ~20% (from MC)

K±0l± selection

=131Mev/c2

=20Mev/c2

• No K nor K0 selection• K decay track (lepton)• at least 2 neutral clusters ( from tag)• (Tcl1 – L1/c) – (Tcl2 – L2/c) minimum

• recovering of splitted clusters

0 massfor K0l signal

K±0e± and K±0±

Efficiency of Kl3 selection ~ 4–8 % (from MC)

me

mml

2 < 6000 MeV2 Ke3ml

2 > 6000 MeV2 K3

ml2 obtained imposing 0 = T

)/()/( cLTcLT clcllll

ml2

K±±00 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)

Preliminary cuts• K+K– events selection and K± tracks identification with KPMFILT filter• CALO + Cosmic Veto trigger • at least 4 neutral clusters in EMC• K decay vertex at rV>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

Correct 2 vertex selection

Rejected for high ± momentum

K±-± Charged Vertices(MC r vs z distributions)

Wrong charge Vertex K±- Correct Vertex K±-±

Momentum distribution of secondary particles (K frame)

DataMC

DataMC

4 clus, rv>40cm 4 clus, rv>40cm,

no FakeVtx + Kinematical cuts

K±±00 physical topics

Invariant mass of selected secondary particles triplets

=490.5 MeV/c2

=19 MeV/c2

=488.9 MeV/c2

=19 MeV/c2

Invariant mass of selected clusters couples

g1+g2 fit performed

1=131.5 MeV/c2

1=18 MeV/c2

1=130.5 MeV/c2

1=16 MeV/c2

Statistics analized

3.16 pb-1 (July 2000, DBV4)Experimental Data

Selection: 1099682 K± , 869 K±±00

MC stream1 K3p0

Generated K±all 980k 560k

Generated K±±00 16.9k 285k

Selection: 299880 K± , 347 K±±00

Selected Kaons on MC

)%05.050.30()(

)(

generated

selected

allKN

allKNK

)%025.0826.1()(

)(00

00

3

generated

selected

KN

KNK

±±00 Branching Ratio

3 )(

)( 00

K

K

data

data

allKN

KNBR

(stat.) )%03.032.1(

* Background contamination subtracted (~0.3% in MC preliminary)** 0.34% subtraction KPMFILT selecting nonK+K– events (MC)

(very preliminary estimation)

*

**

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(?)

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)

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

Wrong 4 vertex association

Fake 4 Vertex(other K)

K±±+– physical topics

DataMC

DataMC

Momentum of selected secondary particles

Invariant mass of selected secondary particles triplets

85MeV/c

85MeV/c=493.6 MeV/c2

=0.9 MeV/c2

=494.2 MeV/c2

=1.2 MeV/c2

Present statistics

Experimental Data

Selection: 1099682 K± , 1075 K±3

MC stream1 K3p

Generated K±all 980k 800k

Generated K±±+– 54.8k 422k

Selection: 299880 K± , 352 K±3

3.16 pb-1 (July 2000, DBV4)

Selected Kaons on MC

)%012.0635.0()(

)(3

generated

selected

KN

KNK

)%05.050.30()(

)(

generated

selected

allKN

allKNK

±±+– Branching Ratio

3

K

K

selectedallK

selectedKBR

(stat.) )%17.071.4(

* Background contamination negligible (<0.3% from MC)

** 0.34% subtraction KPMFILT selecting nonK+K– events (MC)

(preliminary estimation)

*

**

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