|Vus| and KS decays from KLOE

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Vus and KS decays from KLOE
Gaia Lanfranchi, LNF/ INFN On behalf the
KLOE Collaboration XL Rencontres de Moriond
5-12 March, 2005
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Kaon physics at KLOE
KL????,?e?,??-?0,3?0 this talk
KL lifetime this talk
KL ???/KL ?3?0 Phys. Lett. B566 61 (2003)
K0 mass KLOE Note 181 (http//www.lnf.infn.it/kloe)
KS???e? Phys. Lett. B535 37 (2002) Preliminary update with 01-02 data
KS ? p?? First observation
KS ??0?0?0 this talk
KS ?pp-p0 In progress
KS ???-(?) KS ??0?0 Phys. Lett. B538 21 (2002) Update with 01-02 data in progress
Vus from K In progress
K ???0?0 Phys. Lett. B 597 139 (2004)
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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The KLOE Detector
Drift Chamber
sp/p 0.4 (tracks with q gt 45) sxhit 150 mm
(xy), 2 mm (z) sxvertex 1 mm s(Mpp) 1 MeV
s(E)/E 5.7/?E(GeV) s(t) 54
ps/?E(GeV) ? 50 ps
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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• Vus is a fundamental parameter of SM
• PDG 2004 violation of unitarity?
• To measure Vus we need GLe3 .
• We need to measure
• BR(KLe3), tL

Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL lifetime direct measurement

• ? KL lifetime is hard to measure !
• Last measurement 30 years ago (Vosburgh et
  al, PRD 6 (1972), 1834)
• ? Cant stop KLs!
• ? Knowledge of the KL momentum spectrum is
  required.
• ? Measure KL lifetime _at_ KLOE is possible
  because
• ? KLs are slow (ß??0.22, ?L ? 340 cm)
• ? KLs are (almost) monochromatic (P(KL)?110
  MeV)
• ? KLs are background free (unambiguously
  tagged ).

Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL lifetime statistical error vs fit region
Number of events in the fit region
T fit region in lifetime units
Statistical error
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL dominant BRs present experimental situation
KL ????
KL ??e?
NA48 0.40100.0045 KTeV 0.40670.0011 PDG
2004 0.38810.0027
KTeV 0.2701 0.0009 PDG 2004 0.27190.0022
KL ?3?0
KL ?pp-?0
KTeV 0.12520.0007 PDG 2004 0.12580.0019
KTeV 0.19450.0018 PDG 2004 0.21050.0023
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL dominant BRs
What is KLOEs role in this scenario? KLOE can
measure ? absolute branching fractions
(instead of ratios!) ? KL lifetime. Therefore
KLOE can provide a complete and self-consistent
set of measurements of the dominant KL decay
widths without relying on external inputs.
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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The KLOE KL beam
2) Low energy, monochromatic beam P (KL)
? 110 MeV, ß??0.22, ?L ? 340 cm ? a big
fraction of KL (50) decays inside
the detector ? We can measure KL lifetime.
p ?110 MeV
?
KS
KL
BR 34
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL absolute BRs and lifetime
DATA SAMPLE 20012002 data sample 400 pb-1
statistics, 50?106 tagged KL ? 13 million
tagged KL used to evaluate the absolute BRs
? 40 million tagged KL used to evaluate
systematic uncertainties ? 15 million of KL?
3p0 for the direct measurement of the lifetime.
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL absolute BRs
For each KL decay mode (ip??,pe?,3?0,??-?0) we
count the number of events in a given fiducial
volume
Tagging efficiency Depends on the channel Can
introduce a BIAS

• Reconstruction efficiencies
• KL ?p??, pe? e (rec) ? 60
• KL ? pp-p0 e (rec) ? 45
• KL ? 3p0 e (rec) ? 100

Integral over the fiducial volume e (FV, tL) ?
26, depends on tL
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL absolute BRs tag bias
Slightly different tagging efficiencies
for different KL topologies
etagi / etagall ?
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1) Different trigger efficiency for KL decays
in FV / KL interactions in calo / KL
punch-through ? require that KS pions
satisfy trigger conditions by themselves
? trigger efficiency cancels out
2) Interference effect between KS and KL
tracks lowers reconstruction efficiency
for KS?pp- decays at small RL
? cut on the opening angle of KS pions


Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL absolute BRs KL ?charged

• Charged decays selected by closing the
  kinematics at the vertex Pmis- Emiss.
• Fit data with linear combination of 3 MC shapes.
• Large statistics, accuracy is dominated by
  systematics .

Lesser of Pmiss ? Emiss in ?? or ?? hyp. (MeV)
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL absolute BRs KL ? charged

• Pmiss - Emiss distribution very sensitive to
  radiation and momentum resolution
• Check data/MC agreement via independent PID
  e/µ/p from TOF and shower shape
• Radiative corrections properly included in the
  Monte Carlo generators.

Enriched sample of KL?pe? events
Enriched sample of KL?p?? events
Pmiss ? Emiss (MeV) (pe hypothesis)
Pmiss ? Emiss (MeV) (pµ hypothesis)
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL absolute BRs KL ? ?0?0?0
? The photon vertex of KL ? 3p0 is reconstructed
by TOF, using cluster time/position and KL
momentum (from K S ? pp- ) .
(X?,Y?,Z?,T?)
L
L?
p
? solved for the two variables L?, LK
?
LK
e
e-
p -
? Use events with ? 3 photons clustering a
vertex ? 99.2 selection efficiency ? Residual
background (1.3, mainly pp-p0 events) is
subtracted..
Vus and KS decays from KLOE, G. Lanfranchi
LNF/INFN
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KL absolute BRs final results
? Absolute BR's results (tKL 51.54 ? 0.44 ns,
PRD 6 (1972), 1834)
BR(KL? ?e?) 0.4049 ? 0.0010stat ?
0.0031syst BR(KL? ???) 0.2726 ? 0.0008stat ?
0.0022syst BR(KL? 3??) 0.2018 ? 0.0004 stat ?
0.0026 syst BR(KL? ??????) 0.1276 ? 0.0006 stat
? 0.0016 syst
?Systematics
Vus and KS decays from KLOE, G. Lanfranchi
LNF/INFN
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KL dominant BRs unitarity and lifetime

• The sum of the dominant branching fractions (plus
  KL rare decays from PDG) gives

Vus and KS decays from KLOE, G. Lanfranchi
LNF/INFN
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KL dominant BRs results imposing unitarity
BR(KL? ?e?) 0.4007 ? 0.0006 ? 0.0014 BR(KL?
???) 0.2698 ? 0.0006 ? 0.0014 BR(KL? 3??)
0.1997 ? 0.0005 ? 0.0019 BR(KL? ??????) 0.1263
? 0.0005 ? 0.0011
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL dominant BRs comparison
KL ??e? (no PDG) 0.40450.0009 ?2 5.1
KL ???? 0.27020.0007 ?2 0.3
KLOE NA48 KTeV PDG04
KLOE KTeV PDG04
KL ?pp-?0 0.12550.0006 ?2 0.4
KL ? 3?0 (no PDG) 0.19680.0012 ?21.9
KLOE NA48 KTeV PDG04
KLOE KTeV PDG04
Presented by L.Litov _at_ICHEP04
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KL lifetime direct measurement
?We use KL?p0p0p0 events tagged by KS?pp-
events ? tagging and tagged
events are fully decoupled. ?
trigger efficiency is 100, almost flat in the
fiducial volume ? The KL vertex is reconstructed
by TOF, using cluster time/position and KL
momentum (from K S ? pp-) .
(X?,Y?,Z?,T?)
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL lifetime control sample
We use KL ?pp-p0 events to measure ? EmC
time scale calibration ? Vertex
resolution ? Vertex reconstruction
efficiency.
?
?-
? (vertex,pp-) ? 1 mm
KL
?
?
e
?
e-
KS
?
p-
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL lifetime EmC time scale and vertex resolution
EmC Time Scale
Plot di time scale
L(??) L(pp-) (cm)
set at 0.1 level
L(pp-) (cm)
L(pp-) (cm)
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL lifetime final result
Events/0.3 ns
data
Yes, its going down!!
? 14 x 106 events Fit region 6 -26 ns (
40 tL)
t LK/ß?c (ns)
tL (KLOE) (50.87 0.16 (stat) 0.26 (syst))
ns
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL lifetime comparison
average tL (50.98 0.21) ns
KLOE direct
KLOE indirect
Vosburgh et al, PRD 6 (1972), 1834
PDG 2004 (51.8 0.4) ns
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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Vus from Ke3 decays and tL
Most precise test of CKM unitarity comes
from 1st row
Vud2 Vus2 Vub2 Vud2 Vus2 ? 1
D
where it can be tested at 10-3 level
2VuddVud 0.0015 from super-allowed 0?
0 Fermi transitions, n b-decays 2VusdVus
0.0011 from semileptonic kaon decays (PDG
2002 fit)
Vus from neutral Kl3 partial decay widths
½
128 p3 GKl3
1
K0p-
Vus f (0)
G2m M5K Sew Il (l,l0 l,...)
1 dem,l
f Kp(0) form factor at zero momentum transfer,
pure theory calculation (?PT, lattice) I(l)
phase space integral, Sew short distance
corrections (1.0232) l, l0 momentum
dependence of vector and scalar form factors
(f(t), f0(t),t q2) dem electromagnetic
correction (amplitude and phase space)
0.5Ke3-0.8Kmu


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Vus from Ke3 decays and tL
Prescription from hep-ph/0411097 (F. Mescia
_at_ICHEP04) 1) Quadratic parametrization of the
form factor momentum dependence
2) KL lifetime from KLOE (average of the two
measurements)
tKL (50.81 ? 0.23) ns
3) BRs from KLOE set the sum 1 4) Form
factor
fK?(0) from Leutwyller-Roos
0.961(8) confirmed by D.
Becirevic et al (LatticeCHPT) 0.960(9)
M. Okamoto et al. (MILC) (LatticeCHPT)
0.962(11)
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Vus from Kl3 decays and tL
Vus?fKp(0)
KLOE
PRD 6 (1972), 1834
KLOE results Vus?fK?(0) (KSe3)
0.2169? 0.0017
Vus?fK?(0) (KLe3) 0.2164? 0.0007
Vus?fK?(0)(KLm3) 0.2174?
0.0009 From Unitarity (1-Vud2)1/2fK?(0)
0.2177? 0.0028
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KS physics first observation of KS?p?? decay

• Selection à la KS ?pe?
• Kcrash tag 2 tracks from IP with Mpplt 490
  MeV (reject KS?pp(?))
• TOF identification compare pµ expected flight
  times, reject pp,pµ bkg

Kinematic closure use KL to obtain KS momentum
PK and test for presence of neutrino
Vus and KS decays from KLOE G.
Lanfranchi LNF/INFN
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The KLOE KS beam
KL crash ß?? 0.22 , TOF ? 30 ns
KS tagged by KL interaction in EmC ?
efficiency ? 30 ? KS angular resolution? 1?
(0.3? in ?) ? KS momentum resolution 1 MeV ?
3 105 tags/pb-1
KS ?pe?
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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Direct search for KS ?p0p0p0 decay
KS ? 3p0 is pure CP violating decay, never
observed SM prediction GS000
GL000ee?0002, giving BR(KS ? 3p0) 1.9 10-9
Best result BR(KS ? 3p0 ) lt 7.4 10-7 (90
CL) (NA48, hep-ex/0408053)
Vus and KS decays from KLOE G.
Lanfranchi LNF/INFN
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KS ?p0p0p0 upper limit final result
A factor 5 better than the previous limit!
Using the PDG values and our limit we have
h000 lt 1.8 10-2 , 90 CL
90 CL
NA48 (hep-ex/0408053)
Vus and KS decays from KLOE G.
Lanfranchi LNF/INFN

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KS ?p0p0p0 decay and Bell-Steinberger relation
? Uncertainty on KS ? 3p0 amplitude enters in
the Bell-Steinberger relation KS,L K1,2(?
d) K2,1
A limit on BR(KS?p0p0p0) ? 10-7 ? error on Im
d ? 2 10-5
(dominated
now by ?- )
Vus and KS decays from KLOE G.
Lanfranchi LNF/INFN
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Summary
What we have now ? Measurements of all the
dominant KL BRs at 0.5 accuracy ?Two
measurements of the KL lifetime at 0.6
accuracy ? Best upper limit on KS?p0p0p0
decay ? First Observation of KS?p?? decay
Coming soon ? Final result on KS
semileptonic BR ? Analysis of KL semileptonic
form factor slopes ? Analysis of K, BRs and
lifetime.
Vus and KS decays from KLOE G.
Lanfranchi LNF/INFN
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BACKUP SLIDES
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The present data taking
Luminosity collected since may 2004
L ? 770 pb-1

• goal is 2 fb-1 within december 2005
• a factor 4 more than the present
  statistics

Next in line

• ? Limit on KS -gt 3p0 at the 10-8 level
• ? KS semileptonic asymmetry to 4 10-3
• ? First interferometry studies of KSKL
  system

Vus and KS decays from KLOE G.
Lanfranchi LNF/INFN

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The KLOE detector
Be beam pipe (0.5 mm thick) Instrumented
permanent magnet quadrupoles (32 PMTs) Drift
chamber (4 m ? ? 3.3 m) 90 He 10 IsoB, CF
frame 12582 stereo sense wires Electromagnetic
calorimeter Lead/scintillating fibers 4880
PMTs Superconducting coil (5 m bore) B 0.52 T
( ? B dl 2 Tm)
Vus and KS decays from KLOE, G. Lanfranchi
LNF/INFN
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KL lifetime vertex reconstruction efficiency
vertex efficiency for 3p0 MC ()
vertex efficiency for pp-p0 (data MC) ()
MC
DATA
LK (true) (cm)
LK ( pp-) (cm)
Vus and KS decays from KLOE G. Lanfranchi
LNF/INFN
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KL absolute BRs KL ? ?0?0?0
KLOE photons are very low energy photons!
Photon efficiency measured on data using
KL?pp-p0 events
Photon energy spectrum
DATA - Monte Carlo
Plot dellenergia totale per 6 fotoni O della
massa totale.
7 MeV ltE? lt 250 MeV
Vus and KS decays from KLOE, G. Lanfranchi
LNF/INFN
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Effect of the tag bias
Before cuts
After cuts
e (tagging)
e (tagging)
LK (cm)
LK (cm)
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The t0 of the event
T(measured) T(stop)-T(start) T(stop) T
?1(cablesFEE) T(start) Ttrg ?2(cablesFEE)
?rephasing T(measured) T (?2 - ?1) -
(Ttrg ?rephasing ) T T0
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The t0 of the event
T(measured) T(stop)-T(start) T(stop) T
?1(cablesFEE) T(start) Ttrg ?2(cablesFEE)
?rephasing T(measured) T (?2 - ?1) -
(Ttrg ?rephasing ) T T0 In the simplest
case of a photon we have T L/c ?
Tmeasured-L/c T0 For each event we have to
find one particle that can fix the T0 for that
event !
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KS ? p0p0p0 search background calibration
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