1. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
DEAR
Status of KLOE
DANE
B. Valeriani
Institut für Experimentelle Kernphysik-Universität Karlsruhe
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2. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
KLOE & DANE
DANE and KLOE have been
conceived with the primary goal of
studying CP and CPT violation in the
neutral kaon system
Two different methods are used
to investigate these symmetries :
 Double Ratio fixed target
experiments
Quantum Interferometry, unique
a  factory*, since
kaon pairs are collinear and
monochromatic
* DANE facility:
e+ - e- collider working at the  mass
s = 1.02 GeV
Design philosophy:
 L(single bunch) = 5x1030 cm-2s-1
( LVEPP-2M)
high collision frequency
(up to 120 bunches)
 two independent beam lines to avoid
beam-beam interaction
Maximum achieved Luminosity
L ~ 3  1031 cm-2s-1
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3. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
KLOE
Int. Lum. (pb-1) 20
100
1000
2000
now
CP and CPT studies
Rare and not rare Ks decays
(, ee, , ),
Kaon form factor,
Hadronic cross-section
measurement at 1% accuracy
radiative decays,
BR(Ks  +-)/BR(Ks  00),
BR of semileptonic Ks decays,
upper limit on BR(Ks  000)
 10-5, dN/dE (Ks  +-)
Arbeitstreffen "Hadronen und Kerne", Pommersfelden

4. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
KLOE detector
Superconducting Coil B=0.6 T
Be beam pipe
(0.5 mm thickness)
permanent Quad’s
instrumentation
Pb / Scintillating Fibers
Iron Yoke
Cylindrical Drift Chamber
4 m , 3.3 m length 90% Helium, 10% Isobutane all
stereo wires
Electromagnetic Calorimeter
Pb / Scintillating Fibers
Endcap - Barrel - Modules
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5. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
KLOE performances: EmC & DC
P/P = 0.4% (for 90o tracks)
XY  150 m, Z  2 mm DC
E/E = 5.7% / E(GeV)
T = 54 ps / E(GeV)  50 ps
(bunch length contribution subtracted)
EmC
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6. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
Ks decays studies with 2000 data
BR(Ks  +-)/BR(Ks  00)
N(KL  00) / N(KS  00)
N(KL  +) / N(KS  +) R=
N(KL  00) / N(KL  +)
N(KS  00) / N(KS  +)
@ fixed
target
@ KLOE
KL interacting in
EMC (KLCRASH)
The KS is tagged by a KL in the EmC.
The measurement of BR(Ks  +-)/BR(Ks  00) is already competitive:
PDG 2000: Ratio =  [1 ± 1.2  10-2 (stat) ± 0.6 10-2 (syst)]
KLOE 2000: Ratio =  [1 ± 0.35  10-2 (stat) ± 1.5  10-2 (syst)]
preliminary systematics under study
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7. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
Ks decays studies with 2000 data
Ks  e decay
KS  e and KS  +-MC FIT
Data: 2000  11.5 pb-1
TOT = (21.80.3)%
N(KS pen)=283 19 events p- e+ n
KL interacting in
EMC (KLCRASH)
Emiss-Pmiss
PDG2000 (CMD2) : BR(KS e ) = [7.2 ± 1.2]  10-4
KLOE preliminary result: BR(KS e ) = [7.47 ± 0.51(stat)]  10-4 (systematics under evaluation)
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8. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
 radiative decays studies with 2000 data
Scalar sector:
BR(  f0  00) = [7.9  0.2 (stat)]  10-5
BR(  a0  0) = [5.8  0.5 (stat)]  (  )
BR(  a0  0) = [6.7  0.9 (stat)]  (  0)
Assuming BR(  f0)  3  BR(  f0  00) and
BR(  a0)  BR(  a0  0) :
BR(  f0) / BR(  a0) = 4.1  0.4 (stat)
Pseudoscalar sector:
BR(  ’) / BR(  ) = [5.3  0.6]  10-3
M’ = [958.0  0.6] MeV/c2
BR(  ’) = [6.8  0.8]  10-5 (PDG2000: BR= [6.7  1.5]  10-5 )
mix = [40+1.7–1.5]o (flavour basis)
= [ –1.5]o (singlet-octet basis)
In both cases the analysis is going on to evaluate systematic errors
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9. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
  0
~0.3M events
3 contributions to Dalitz plot
E0 – mo GeV
Preliminary
 r ,0 p 0, 
f  p +p -p 0 (direct)
e+e-  wp 0
in the fit the mass and width of
the , the M(,0) and the direct
decay contribution are left free
(E+ - E-)/3 GeV
A1 (10-2) f1 (deg) M(r+,-) M(r0) G DM(+,-)
KLOE       0.3 (*)
PDG 11 (CMD-2)  0.9 (**) 
(*) CPT test at < 5 x 10-4
(**) mixed charges (t decay and e+e-) average: M(r0) - M(r+,-) = 0.4 0.8
Efficiency (X,Y) from Montecarlo: fine tuning in progress to reduce systematic effects on
M(r0) (now at 2 MeV level)
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10. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
Measurement of (e+e  s<1 GeV
KLOE measures hadronic cross-section as a function of the  center of mass energy M2 in the fixed energy environment of DANE by using the RADIATIVE RETURN METHOD.
A hard photon radiated in the initial state (Initial State Radiation, ISR) lowers the available energy, allowing to exploit the full energy range 4m2 < M2 < 1 GeV2, without any energy scan.  
M2 = M2 - 2M E
Why are we interested in measuring (e+e  s<1 GeV?
A precise measurement of (e+e  +) as a function of M2 in this
energy range is relevant for the theoretical estimation of the
hadronical contribution both to the muon anomalous magnetic moment
a and to the fine structure constant at the Z mass (M2Z).
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11. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
(ee  ) & a
The reduction of the present error on the hadronical contribution to a becomes extremely important with the new results of the BNL g-2 experiment
aexp
Czarnecki,Marciano 2000
Czarnecki, Krause,Marciano 1998
(g-2)/2 = ( ± )  10-10
E821, hep-ex/
amexp - amtheor,SM = 2.5  2.9  difference
aQED = ( ± )  10-10
aweak = ( ± )  10-10
= ( ± )  10-10
= ( ± )  10-10
(g-2)/2 = aQED + ahad + aweak (+ anew physics ?)
atheor
ahad
Davier, Höcker 1999,
 decays
Jegerlehner 2001,
without  decays,new CMD
and BES data
Reducing ahad allows to isolate possible new physics contributions!
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12. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
KLOE contribution to the measurement
a can be expressed in terms of (ee  hadrons) via the dispersion integral:
Since low energy contributions are enhanced in the
dispersion integral, ca. 77% of ahad comes in the
energy region 2m < M < 1.4 GeV.
61% of ahad is covered by the  resonance:
0.28 GeV < M < 0.81 GeV
An accuracy of 1% in (ee  hadrons) up to 1.4 GeV results in
a =  7  10-10
The same accuracy in the measurement of (ee  hadrons) up to 3.1 GeV
would result in
a =  1.5  10-10
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13. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
The    final state
Three processes contribute to the    final state:
 Initial State Radiation (ISR)*
 Final State Radiation (FSR)
   f0  
The relative contribution of the three processes depends strongly on
the photon polar angle and on the two pions invariant mass value:
 ISR contribution is peaked at small photon polar angle
 FSR and  direct decay contributions are mainly concentrated in the
high M region (M2 > 0.8 GeV2)
*S. Binner, J.H. Kühn, K. Melnikov, Phys. Lett. B 459, 1999
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14. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
ee   selection
Event Display DIDONE
 events are selected by
asking for two tracks connected
to a vertex in the IR
Some background channels are
selected together with the
signal:
 ee  ee 
 ee   
 ee    0
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15. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
Fiducial volume definition
Two fiducial volumes are currently studied:
small angle: <21o  >169o
highest cross section; small background from ; small
contribution from FSR; no photon tagging required
large angle: 60o<<120o
large background from , especially at low M2; photon detected in the EmC
The pions must be central (55o-125o)
to cut down the background (ee ,
 )
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16. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
Signal selection:1
Bhabha events are rejected with a likelihood function based on the
TOF and the shape of the energy deposit in the EmC:
eff. on pions
 
* 0  ee
450MeV< Ptr<500MeV
eff. on electrons
log(Relative Likelihood)
Track momentum
  and radiative bhabhas are used as control samples
 different likelihood functions are defined for each track
momentum range (50 MeV bin)
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17. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
Signal selection:2
25°< qg < 155°, 50°< qp <130°
Mtrk is defined by the following
relation:
After the likelihood cut the signal
peak is clearly visible in the Mtrk
variable
The signal is selected by cutting
10 MeV around the pion mass
Before Likelihood
( Rad. Bhabhas )
After
Likelihood
mmg
p+p-p0
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18. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
ee   cross-section
Integrated luminosity
 = acctrgsel
 the acceptance eacc is evaluated from MC (large angle; small angle)
 the global selection efficiency esel is evaluated from DATA+MC
 the trigger efficiency etrig is evaluated from DATA
 the Luminosity is measured using the Bhabha scattering at large angles
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19. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
Pion form factor
The pion form factor is extracted from
ISR cross-section using the relation:
H=radiation function in Born approximation
(no radiative corrections)
Experimental points have been compared
with Kühn-Santamaria parametrization*
for F (fixed parameters, no fit has been
performed so far)
|F(M2)|2 =
d(, M2)
d M2 H(M2 ,cosmin,cosmax)
|F(M2)|2
 large angle
 small angle
Ldt = 16.5 pb-1
M
*Z. Phys. C48 (1990) 445
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20. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
Pion polar angle asymmetry
FSR parametrization in the MC has been checked by looking at the pion pair asymmetry in the polar angle
distribution
small angle
large angle
Asymmetry (%)
Asymmetry (%)
 DATA
 MC
 DATA
 MC 
A(i)=
N(,i)  N(,i)
N(,i)  N(,i) 
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21. Arbeitstreffen "Hadronen und Kerne", Pommersfelden 24-28.9.2001
Conclusion
 KLOE has collected ~25pb-1 by the end of year 2000
 Preliminary studies show the good performances of the detector
 Competitive results have already been achieved on the analysis of KS decays
(BR(KS  +-)/BR(KS  00), KS semileptonic decays) and of  radiative
decays (BR(  S), -’ mixing)
 KLOE is expected to collect 200 pb-1 by the end of 2001
 With these statistics a measurement of (e+e  s<1 GeV at 1%
level can be performed
 This result would play an important role in the reduction
of the present error on the hadronical contribution to a
 First results obtained from the analysis of the 2000 statistics
(16.5 pb-1) look promising
 In parallel a theoretical work is going on (Kühn and collaborators)
in order to evaluate the radiative corrections to the process to the
NLO (hep-ph/ )
Arbeitstreffen "Hadronen und Kerne", Pommersfelden