Review of NA48
CP violation measurementswith Neutral and Charged KaonsMonica Pepe - INFN Perugia
on Behalf of the NA48 and NA48/2 Collaborations
Cagliari Cambridge
Cagliari,
Cambridge, CERN
CERN, Chicago,
Chicago Dubna,
Dubna Edinburgh,
Edinburgh Ferrara,
Ferrara Firenze,
Firenze Mainz,
Mainz
Northwestern, Orsay, Perugia, Pisa, Saclay, Siegen, Torino, Warsaw, Wien

KAON09 , Tsukuba , Japan - June 9 – 12, 2009

OUTLINE
 Introduction
 NA48: the CP violation experiment
 History
 Detector
 NA48:

Direct and Indirect CPV in K0 2 decaysy NA48/2: Direct CPV in K± 3 decays
 Conclusions

KAON09, June 9-12, 2009

Monica Pepe - INFN Perugia

2

CP Violation in Kaons
Kaons remain a privileged observatory for flavour physics phenomena:
all the features of flavour physics are present (CPV of same size as in B)• Very simple (minimal) system• Very nicely accessible experimentally All 3 types of CPV can be observed in K0 decays
 in K0-K0 mixing (ΔS=2, Indirect CPV: Re(ε))
 in the decay amplitudes (ΔS=1, Direct CPV: Re(ε )) in the interference between decays with and without mixing (Im(ε) and Im(ε )) Only Direct CP Violation occurs in K± decays (no mixing) Complementary observables to measure Direct CPV in Kaons ε/ε, Ag , Ultra-Rare decays

KAON09, June 9-12, 2009

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3

The NA48 experiment @ CERNThe CERN Accelerator Complex

NA48

The SPS at CERN produces 400 GeV/cprotons using either a fast or slow
extraction system

A fixed target experiment at the CERN SPS
d di t d to
dedicatedt theth studyt d off CP violationi l tiandd raredecays in the Kaon sector

The SPS is used as well as
injector for the LHC accelerator

Juramountains

LHC
NA48  NA62

FranceNote:
NAYY ≡ YYthexperimentinstalled in the
North Area on abeam extracted
from the SPS
accelerator

SPS

Geneva airport

KAON09, June 9-12, 2009

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NA48/NA62:
at the heart of the LHC!

LHC

SwitzerlandN4

NA48: history……
Data taking periods

NA48 (1997-2001)
 Direct CP violation in neutral kaon decays
R ( '/ ) = (14Re('/)(14.7
7 ± 2.2)
2 2) x 10-44
 Measurement of CP violation parameter |+− |NA48/1 (2002)
 Rare KS decays• BR (KS → 0 e+ e-) = (5.8+2.8-2.3 ± 0.8) x 10-9
• BR (KS → 0 + -) = (2.8+1.5-1.2 ± 0.2) x 10-9
(not presented here
here….))

NA48/2 (2003-2004)
 Search for direct CP violation in K±→ 3 decays
Final resultand many other rare decay results!
KAON09, June 9-12, 2009

Monica Pepe - INFN Perugia

5The NA48 detector
M i d
Main
detectort t components:t Magnetic spectrometer (4 DCHs):
4 views/DCH:i/DCH redundancyd d efficiency
ffi iσ(p)/p = 1.02% + 0.044% p [GeV/c]
σx,y ~ 90 μm
 Hodoscope: fast trigger andprecise time measurement (150ps)
 Liquid Krypton e.m. calorimeter:
High granularity, quasi−homogeneousσ(E)/E = 3.2%/√E + 9%/E + 0.42% [GeV]
σx = σy = 0.42/√E
0 42/√E + 0.6
0 6 mm (1.5
(1 5 mm @ 10 G
GeV)V) Hadron calorimeter, photon vetos,
muon veto counters
KAON09, June 9-12, 2009

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6

CP Violation in Neutral Kaon decays(NA48)
1)

/
/

Direct CP violation

2) |+− | The CP violation parameter

KAON09, June 9-12, 2009

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71) / Direct CP violation in K0→ 2 decays
/ derived from the double ratio

N(KL  00 ) / N(KS  00 )R =   Re(/ )N(KL  +- ) / N(KS  +- )Experiment designed to exploit cancellations of systematic effects

Simultaneous K beams:• split same proton beam (~1012 ppp)
• convergent KL-KS beams• KS from protons on near target• KS identification via proton tagging
KAON09, June 9-12, 2009

• 4 decay modes collected simultaneously• SameSddecay regioni ffor allll modesd• KL events weighted by a function of their lifetime• KS events weighted by KL/KS intensity ratio• KS decays distinguished from KL events by time
coincidence
i id
off d
decay titime andd titime off protons
t
on
+
0
0
the tagger (same for   and   decays)• Analysis performed in 20 bins of kaon energy
Monica Pepe - INFN Perugia

8'/ Result
Re('/) = (14.7 ± 2.2) x 10-4
Average: (16.3± 2.2) · 10-4((before KTeV new result..…))
KTeV New!
(19.2 ± 2.1) 10-4

Observation of Direct CP Violationin K0→ 2 decays

Tiny particle - antiparticle
asimmetry
Theoretical predictions (SM)New measurements
KAON09, June 9-12, 2009

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92) +− Direct and Indirect CPV in KL→  decays
The CPV parameter +− : a fundamental observable of CP violation

A( K L    )      ' A( K S     )Indirect CPV

CPV decay

Direct CPV

CP = 1
1

CP = +1

KL ~ K2 +  K1
KS ~ K1 +  K2
CP(+–) = +1

Experimental Method:

((KK L     ) Measure the ratio of the decay rates
( K L    e  )( K L      )  Compute
BR
(
K


e )
BR(KL → ) = L( K L   e  ) Extract ( K L      ) ( K S    )BR(KL → )  KS BR( K S    )  KL

Using the best single KS (NA48’02) and KL (KLOE’06) lifetime measurements
and BR(KL→e ) (NA48’04 + KTeV’04, KLOE’06) and BR(KS→ ) (KLOE’06)
KAON09, June 9-12, 2009

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10K2/Ke3 event selection
Dedicated 2-day
2 day run in 1999 with a pure low intensity KL beam: ~80
80 million 2
2-track
track events

KL → KL → e• CP violatingg process:need to suppress dominant background(Ke3 , Kμ3 , KL →  ) by 4-5 orders ofmagnitude• Acceptance = (58.26 ± 0.04)%• Small background ~0.5%• Data well described by MC• Select Ke3 decays
y byy e-ID using
g the ratio E/p1(energy in electromagnetic calorimeter overtrack momentum)• Acceptance = (29.86 ± 0.02)%• Small background ~ 0.5%

Events selected ~ 47000
entrietries / 0.01

2

entries / 0.002
en
02 GeV/c

10

4

Data, selected K2π
K2 π MC103

K μ3 MCKe3 MC10

2

Events selected ~ 5 million

x103
1500

Data, selected Ke3electrons

1000

MC sum

pions

10
500

1
0.4 0.42 0.44 0.46 0.48 0.5 0.52 0.54 0.56 0.58 0.6
2

0
0

0.2

invariant π+π- mass [GeV/c ]Monica Pepe - INFN Perugia
KAON09, June 9-12, 2009

0.4
0.6
0.8
1
1.2
E/p: energy deposited in Lkr / track momentum11

Result on | | The directly
y measured value:

R = (KL+–) / (KLe) = (4.835  0.022stat.  0.016syst.)  10–3
Corrections and systematicsyon R
Uncertainty source Branching fraction:
BR(KL+–) = (1.941  0.019)  10–3
Radiative corrections:• Includes +–

IB componentp• DE component (CP conserving) is subtracted| +− | =Uncertainty

Particle ID+1.34%

0.05%

K2 background–0.49%
0 49%

0 03%
0.03%

Muon ID+0.48%

0.18%

Trigger–1.29%

0.11%

Energy spectrum

0 20%
0.20%

Radiative corrections

0.10%

MC statistics

0.10%

Total

 The CP violation parameter:

Correction

BR(KL+–)

KS

BR(K
( S+–)KL+0.04%0.33%= (2.223  0.012) 10–3

Published in Phys. Lett. B645 (2007) 26
KAON09, June 9-12, 2009

Monica Pepe - INFN Perugia12|+− |

Comparison to world data

K2/Ke3|+− |

 Good agreement between NA48, KTeV and KLOE results Recent measurements led to revision of the Particle Data Group average(PDG 2008 : |+− | = 2.233 ± 0.012)
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13Direct CP Violation inK and K00 decays(NA48/2)

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CP violation in K±→3decays Only direct CPV in K± possible – mixing is not allowed Potentially large statistics:
BR ((K±  ±+ ) = 5.57%

BR ((K±  ±00 ) = 1.73%

 Simple selection
 Low
L
b
backgroundkdMethod: No absolute kaon flux measurement is required Compare only Dalitz plot shapes between K+/KKAON09, June 9-12, 2009

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15

The CP violation parameter Ag
Kinematics:

Matrix element:si = (PKPi)2, i=1,2,3 (3=odd )
s0 = (s1+s2+s3)/3|M(u,v)|2 ~ 1 + gu + hu2 + kv2 + …
1evenu = (s3-s0)/m2
v = (s( 2-s1)/m
)/ 2

K±

2even3odd

K±±+ NA48/2 Slopes:

Kaon rest frame:g = (-21.134 ± 0.017)%
h = ( 1.848  0.040 )%k = ( –0.463  0.014)%
Phys. Lett. B649 (2007) 349-358

u = 2mK·(mK/3Eodd)/m2
v = 2mK·(E1EE2)/m2

Dalitz Plot forK±  ±+

K±±00 PDG value:g = (62.6 ± 0.7)%

Direct CP-violating quantity:
the slope asymmetry
Ag = (g( +g)/(g)/( ++g) = Δg/2g/
KAON09, June 9-12, 2009

SM predictions:|Ag| : 10-5 - 10-6

If Ag ~ 10-4  New Physics !
If Ag  0  Direct CP Violation

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16Experiments & Theory
Experimental precisions before NA48/2:
E. Gámiz et al., JHEP 10 (2003) 42[Ag~10-3, dominated by systematics]

SM estimate (NLO ChPT):
Agc = (–1.41.2)10–5
Agn = (1.10.7)10–5

Smith et al. ((1975))

|Ag|

10-2

Ford et al. (1970)
HyperCP prelim. (2000)
TNF (2005)

10-3

NA48/2
proposal

G. D’Ambrosio et al., PLB480 (2000) 164

ModelsMd l beyondbd theth SM predict
di t
substantial enhancement partiallywithin the reach of NA48/2“neutral”

10-4“charged”

SUSY
&

10-5
SM

New
N
physics

10-66
KAON09, June 9-12, 2009

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Asymmetry of integrated
decay rates is strongly
suppressedpp17

NA48/2 Goal and method• Primary NA48/2 goal:– Measure slope asymmetries in “charged” and “neutral” modes withhigh accuracy (few 10-4)• Strategy
gy– To measure a tiny asymmetry one must guarantee perfect charge
symmetrization in the experimental setup and eliminate the remaining
acceptance differences by a smart analysis technique• NA48/2 method:− TwoTsimultaneousi l
K+ andd K– beams,bsuperimposedid ini space, withih
similar narrow momentum spectra− Equalise averaged K+ and K– acceptances by frequently alternating
the polarities of the relevant magnets− Measure asymmetry exclusively considering slopes of ratios ofnormalized
li d u distributions
di t ib ti
KAON09, June 9-12, 2009

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18

The K+/K- simultaneous beam setup
SPS Spill Length : 4.8 s
Cycle Time : 16.8 s
Proton momentum : 400 GeV/c

20 MHz (π/K ~ 12) π decay
products stay inside pipe
Beams coincideB
i id within
ithi ~1mm
1
all along the 114m decay volume,always in vacuum

Pπ spectra(60 ± 3) GeV/c

K+/K- flux ~ 1.8(stable in 1%)

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19NA48/2 data taking completedView of the NA48/2 beam line
2003 run: ~ 50 days
2004 run: ~ 60 days
Statistics:K   +: ~ 4 x 109
K   00 : ~ 1 x 108
Sensitivity to K± decays with
branching ratios down to 10–9

More than 200 TBytes recorded !

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20

Method to extract Ag Build
B ild u projections
j ti
off ththe Dalitz
D lit plotl t ffor K+ andd K-: N+(u),N( ) N-(u)( ) Make the ratio of these two distributions: R(u) Fit a function to this ratio to extract g(This holds only if the acceptance for K+ and K- is the same)K      + 

N  (u )g  uR(u )  
 1N (u )
1  gu  hu
h 2

BUT!
There are experimental asymmetries that do not cancel in the simple ratio R(u)To cancel the charge asymmetry in the detector and beam optics:
Beam line (achromat) polarity (A) is reversed on weekly basis
Spectrometer magnet polarity (B) is reversed on few hours basis
KAON09, June 9-12, 2009

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21

Acceptance cancellation
Detector left/right asymmetry cancels in 4 ratios of K+/K U-spectra corresponding
to the four possible combinations of the magnetic fields:

A B K  )RUS  N(
N( A B K  )RUJ N( A B K  )N( A B K  )RDS N( A B K  )N( A B K  )RDJ N( A B K  )N( A B K  )Spectrometer
field

Y

X

Beam line: K+ Up

B+

K+
K−
Beam line: K+ Down

Jura(left)B−
B

Z

SaleveSaleve(right)Indexes correspond to: beam line polarity (U/D)
g direction of kaon deviation in spectrometerp((J/S))
left/rightK samples in numerator and denominator illuminate the same parts of the detector
KAON09, June 9-12, 2009

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22Quadruple Ratio Use a quadruple ratio for maximum cancellation of systematic biases

R4 = RUS · RUJ · RDS · RDJ
 Cancellation of global time instabilities + local beamline biases(K+,K
K- simultaneously
i lt
l recorded)d d) Cancellation of left-right detector asymmetries
 Cancellation of effect of p
permanent strayy fields ((earth, vacuum tank magnetization)g) Extract Δg by fitting the quadruple ratio:



 gu

f ( u )  n   1 
2 
1  gu  hu  Advantages:
 Result sensitive only to time variation of asymmetries in short time intervals(smaller than corresponding field alternating period) The method is independent of K+/K- flux ratio and relative sizes of the samples
 The analysis does not rely on a detailed MC to calculate acceptances
KAON09, June 9-12, 2009

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23

4

K3 event selection• Trigger selection based on Hodoscope and Magnetic Spectrometer• Offline reconstruction based on Magnetic Spectrometer only :event kinematics from track momenta and directions extrapolated to decay vertex• Acceptance limited mostly by beam pipe through DCHs
• Negligible background

Data

|v|

2.5
Odd pionin beam pipe

Even pionin beam pipe

2
1.5
1

Eve
ents

3.11109 fully reconstructed eventsfrom 2003+2004 sample
M=1.7=1 7 MeV/c2

MC K3MCK3 +  decay
MC K3

K+/K–  1.8
18

0.5
0
-1.5

Ke4 background
g
-1

-0.5

0

0.5

KAON09, June 9-12, 2009

1

u 1.5

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24

K3 asymmetry: result
g = (0.7 ± 0.7stat ± 0.4trig ± 0.6syst)  10-4
= (0.6 ± 0.9)  10-4

 A factor ~20 better precision thanprevious measurements

Ag = (1.5 ± 1.5stat ± 0.9trig ± 1.3syst)  10-4

 Uncertainties of statistical nature
dominates= (1.5 ± 2.2)  10-4
Published: Eur. Phys. J. C52 (2007) 875

 Result compatible with SM
N evidence
No
id
for
f New
N
Ph
Physicsi NA48/2 design goal reached.

Measurements of Ag

-40
-60
-800

final 20003+2004

Time stability of results
12

Slope
pe differencee × 104-20

Ford et al. (1970)
F

0HyperCPP (2000)

20

final 20003

prelim. 2003×10
4
Ag Δxg1040

NA48/2(results superseding
each other)

g
gΔg
8

MC
MC

1

2

3

4

5

Control:Beam line Asym

0

-4

6

Δg
g
gup
UD
up-down
down

4

χ2/ndf = 9.7/8

KAON09, June 9-12, 2009

Δg
g
gleft
SJ
left-rightrightControl:
Detector Asym

-8 0 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8Supersample

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25

K00 event selection
 Based on Charged Spectrometer and LKR El
El. Magn
Magn. Calorimeter|v|

 Charge-symmetric procedure:- no geometrical information from the ± track- computation of u variable from the 00 invariant mass only3

Odd pionin beam pipe

2.52

 Two 0→ decays define K± decay vertex position- 00 longitudinal vertex position in decay volume

1.5

For each photon pair (i,k),(l,m) a decay vertex is reconstructedalong the beam axis under the assumption of 0→ decay

0.5

1

0

-1.5

-1

-0.5

0

0.5

1

1.5

u
M3 spectrum
E
EventsM(0)2 = 2EiEk(1-cosα )  EiEk (Dik)2/(Zik)2

K±
91 3  106 events
91.3

Events with nohits in μ detector

m = 0.9 MeV/c2

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M(3) [GeV/c2]

26

K00 asymmetry: result
g0 = (2.2 ± 2.1stat ± 0.7syst)  10-4
= (2.2 ± 2.2)  10-4

 Statistical precision in Ag0 similar
to K± → ± mode

 Ratio of charged to neutral event
statistics N±/N0 ~ 34

Ag0 = (1.8 ± 1.7stat ± 0.6syst)  10-4
= (1.8 ± 1.8)  10-4

 Ratio of slopes |g±/g0| ~ 0.34

Published: Eur. Phys. J. C52 (2007) 875

 Final result consistent withStandard Model predictionsTi
Timestabilityt bilit off resultslt
Slolope differenc
nce × 104

20

Δg
g

Δg
gUD

Δg
gSJL-R

U-D

12♦ 7 super-samples
give consistent results♦ Detector and beam line
asymmetry effects at
a few 10-4 level,
reproduced by MC

4

-4

MC
-12

Control:
DetectorMC
Asym

χ2/ndf = 1.5/6-20 I

II III IV V VI VII I

KAON09, June 9-12, 2009

II

Control:Beam line Asym

III IV V VI VII I

II III IV V VI VII
Supersample
Monica Pepe - INFN Perugia

27Conclusions
Over 10 years
years, the NA48 experiment at CERN has carried out an
extensive physics programme devoted to the study of CP violation(and rare decays) in both neutral and charged Kaon sectors
NA48: Observation of Direct CP Violation in K0 2 decays
Re('/) = (14.7 ± 2.2) x 10-4
 Precise |+− | measurement (0.5% accuracy)|+–| = (2.223 0.012) 10–3
 in agreement with recent KTeV and KLOE results, PDG average has been revised

NA48/2:
 Search for direct CP violating charge asymmetry in K± 3 decays
Ag = (-1.5 ± 2.2) x 10-4 K±→ 
Ag = ( 1.8 ± 1.8) x 10-4 K±→ No evidence of direct CPV
at the level of 2 x 10-4

 orderd off magnitude
it d iimprovementt iin precisioni i results in agreement with the SM expectation
KAON09, June 9-12, 2009

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28

SPARE SLIDESKAON09, June 9-12, 2009

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29

KAON09, June 9-12, 2009

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30

Acceptance for weighted KS and KL

KAON09, June 9-12, 2009

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Results
(R) (x 10-4)

98+99
35.9  12.6

2001
35.0  11.0

Statistics (x 106)97

98+99 2001

KL  00 : 0.49

3.3

1.5

Contributions to corrections and syst: (x 10-4)

K S   0 0 : 0
0.98
98

5
5.2
2

2
2.2
2

+- trig. Ineff. -3.6  5.2.0
00 bkg-5.9  2.0
+- bkg+16.9  3.0
Beam scattering -9.6  2.0
Accidental Tagg +8.3  3.4
Tagging ineff--  3.0
Accept. stat.
+26.7  4.1
Accept. syst.
 4.0

KL  +- : 1.1

14.5

7.1

KS  +- : 2.1

22.2

9.6

+5.2  3.6-5.6  2.0+14.2  3.0-8.8  2.0+6.9  2.8 (stat)--  3.0+21.9  3.5 (stat) 4.0

In 97: Syst. Error on (R)  35
(trigg +- , reconstr 00 , LS , accidentals)
NA48 (97,98-99,2001)(14.7 ± 2.2) x 10-4

KTEV (96(96, 97)(20 7 ± 2.8)
(20.72 8) x 10-4

KTEV (new)(19.2 ± 2.1) x 10-4

KAON09, June 9-12, 2009

Monica Pepe - INFN Perugia

NA48 beam line for p
pure KL beam
Special run (2 days in 1999) with pure KL beam at low intensity
intensity.
Minimum bias trigger to select only events with 2 charged tracks~ 80 million events recorded

KAON09, June 9-12, 2009

Monica Pepe - INFN Perugia

33

K2
K2
/Ke3 event selection
Basic two track selection :1 Two tracks with opposite charge
1.
2. CDA  3 cm
3 Vertex longitudinally between 8 m and 33 m from the final collimator3.
4. 15 GeV/c  ptrac  100 GeV/c selection :1. M compatible with the K mass
2 p2tK <3x10-4 GeV/c22.
3. E/p < 0.93
4. No muons (to reject Ke selection :1. E/p > 0.93  electron

KAON09, June 9-12, 2009

Monica Pepe - INFN Perugia

34




eesystematics
systematics

KAON09, June 9-12, 2009

Monica Pepe - INFN Perugia

35

CP violation parameter   BR( K L    )  KS BR( K S    )  KL

• External input: best single measurements
 KS lifetime: KS = (0.895980.00070)10–10 s (NA48 ’02);
 KL lifetime: KL = (5.0840.023)10–8 s (KLOE ’06);
 BR(KLe) = 0.40220.0031 (NA48 ’04
04 + improved KL30: KTeV, KLOE); BR(KS+–) = 0.691960.00051 (KLOE ’06).

KAON09, June 9-12, 2009

Monica Pepe - INFN Perugia

36  Comparison of results

For comparisonp
it is importantp
to pointpout the treatment of radiative
decays (IB and DE)
KAON09, June 9-12, 2009

Monica Pepe - INFN Perugia

37

K± → ± : Ag final result (2003+2004)
Δg = (0.7 ± 0.7stat. ± 0.4stat. (trig.) ± 0.6syst.)  10-4
Time stability of result
Slope differenc
nce × 104

12

g K+Δ/K

8ΔgΔgKLeft/KRight KUp/KDown
SJ

UD

MC

4

♦ 9 super-samples
give consistent
results♦ Detector and beam
li asymmetry
line
t
-4
effects at a few 10-4
χ /ndf = 9.7/8-8 0 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8level, reproduced
Supersample
Detector
Beam lineby MCΔgasymmetry asymmetry
0

2

Ag

= (-1.5(-1 5 ± 2.2)
2 2)  10-4

A factor ~ 20 better precisionth previous
thaniexperimentsitResult compatible with SM predictions
No evidence for New Physics
KAON09, June 9-12, 2009

Monica Pepe - INFN Perugia

Systematic effects on ΔgΔg(10-4)

Spectrometer alignment± 0.1

Spectrometer magnetic
field

± 0.3

Beam geometry andstray magnetic fields± 0.2

Kaon production spactra± 0.3

Resolution and fitting± 0.2

Accidental activity(pile-up)± 0.2

Total systematics± 0.6

L1 trigger efficiency± 0.3

L2 trigger efficiency-0.1 ± 0.3

38

K± → ±00 : Ag0 final result (2003+2004)
7 super-samples

Slope ddifference × 104

20g KΔ+/K

ΔgUD

ΔgSJ

Systematic effects on Δg12

Δg(10-4)

4

Overlap of LKr showers

± 0.5
05

-4

L1 HOD trigger efficiency± 0.1

L1 LKr
LK trigger
tiefficiency
ffi i

± 0.1
01

L2 trigger efficiency± 0.3

Stray magnetic fields± 0.1

Kaon production spectra± 0.3

Accidental activity (pile-up)± 0.2

KLeft/KRight-12
χ2/ndf = 1.5/6-20 I

II III IV V VI VII I

Δg

KUp/KDown

MC
II

III IV V VI VII I

II III IV V VI VII
Supersample

Detector
asymmetry

Beam line
asymmetry

Statistical precision in Ag0 similar to K± → ± mode
despite 34 times less events: |g0/g±| ~ 3.

Final result consistent with SM predictions:

Ag0 = (1.8 ± 1.8) x 10-4
KAON09, June 9-12, 2009

Monica Pepe - INFN Perugia

Total

± 0.7

39

K± → ±00 : Fit of the quadruple ratio Quadruple ratios of different supersamples averaged in u-bins after corrections
 Fitted with f(u) using g and h measured by NA48/2

f(u)=n(1+gu/(1+gu+hu2))4
χ2 / ndf
26.69 / 26
p0n10.41 ± 0.01
p1
gΔ
0.0002225 ± 0.0002079

R4(u)

10.7
10.6
10.5
10.4
10.3
10.2
10.1
-1.5

KAON09, June 9-12, 2009

-1

-0.5

0

Monica Pepe - INFN Perugia

0.5

1 u 1.540