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The CP-violation experiments NA48 at CERN
Manfred Jeitler
Institute of High Energy Physics
of the
Austrian Academy of Sciences
RECFA meeting
Innsbruck, 26 March 2004
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
overview
the original NA48 experiment – direct CP-violation: Re ’/
measurements in a high-intensity KS beam– KS 0 0 0
– KS 0e+e- and KS 0+-
measurements of direct CP-violation with charged kaon beams– K + -
future ?
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
Re61/00
00
S
L
S
L
K
K
K
KR
The original aim of NA48: measuring Re ’/
KS
KS
KL
KL
’/ 0:
direct CP-violation
exists
”frequent“ ”rare“
/
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
The neutral kaon beams of NA48
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
The detector of the NA48 experiment at CERN
• spectrometer (consisting of 4 drift chambers and a magnet) and hadron calorimeter for measuring -decays
• electromagnetic liquid-krypton calorimeter for measuring -decays
magnet
DCH
DCH
DCH
DCH
hadron calorimeter
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
The liquid-krypton calorimeter
• measures decays of kaons into neutral particles: K
• filled with 9 m3
of liquid krypton
• part of trigger electronics built by HEPHY, Vienna
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
NA48
Re’/= (14.7 ± 2.2) 10-4 NA48 (all data)
Re’/: the experimental result
(15.3 ± 2.6) 10-4
Re’/= (16.6 ± 1.6) 10-4 new world average
(13.
7 ±
3.1)
1
0-4
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
Re ’/: the shape of the theory
considering the present accuracy of calculations, there is no use to further improve measurements
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
pay one – take three:
charged kaons
charged kaons
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
The high-intensity KS-beam
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
KS 000
CP-violating decay– no CP-conserving components such as in KS +-0
counterpart to the “classical” CP-violating decay KL 0 0
– CP | 000 > = - | 000 > while
– CP | KS > ~ CP | K1
> = + | K1 >
described by parameter )3(
)3(0
0000
L
s
KA
KA
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
KS 000 : the result
result consistent with zero with 5% probability
limit on branching fraction:
BR(KS 000) < 1.410-6 at 90% confidence level
(one order of magnitude better than previous limit)
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
KS 000 and CPT
Bell-Steinberger relation statesfinal
fSW ii )]Im())[Re(tan1(
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
KS 0e +e - and KS 0+-
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
7 events found with a background of 0.15 +0.10
-0.04
KS 0e +e -
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
KS 0+-
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
measure decays of K+ and K–
direct CP-violation in K (3) :
M(u,v) 1 + gu + hu2 + kv2
Ag (g+ g– )/(g+ + g–)
measurement of the ratio
R (u) dvM+(u,v)2 dvM–(u,v)2
constant simultaneous K+ and K– beams same acceptance, alternating magnetic field
high-precision measurement of K (3)
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
Bel'kov '99Shabalin '98
SUSY D'Ambrosio '99
SM
asymmetry parameter Ag in K (3)
theoreticalpredictions
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
NA48KLOE
Hyper CP
BNL
and expectedexperimental
accuracy
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
KAon BEam Spectrometer(“Micromegas” detector)
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
KABES: KAon BEam Spectrometer(a MICROMEGAS detector)
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
charged Ke4 decays K+/- e
experimental observation of quark-antiquark condensate– s-wave scattering length a0
0 in -scattering at low energy
earlier experiments statistically and systematically limited– Rosselet et al., 1977
– Brookhaven, 2001
neutral Ke4-decay (K0L e ) was studied by the
Vienna group (Laurenz Widhalm, Heinz Dibon)
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
SM prediction: BR(K+ → +) = 7.1 ± 1.0 × 10-
11
future plans: K+ → + so far, three events
seen at BNL (E787 and E949)
decay established but not enough statistics to check Standard Model
plans to collect ~100 events at FNAL (CKM experiment): financial difficulties
idea to use CKM’s expertise and parts of the NA48 detector at CERN
Conclusion:
NA48 has yielded an unexpectedly large amount of valuable results
.....
and may still continue to do so!
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
special interest: test of CPT invariance if CPT is conserved
– and there are no transitions to I = 3, or to nonsymmetric I = 1 states:
– A1 : I=1 amplitude
– real part fixed by CPT
– imaginary part sensitive to direct CP-violation
Bell-Steinberger relation– connects CPT violating phase with parameters via unitarity:
statesfinal
fSW ii )]Im())[Re(tan1(
KS 000
)Re(
)Im(
1
1000
A
Ai
)2
arctan(SL
SW
m
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
KS 000 : the approach
time evolution of KL,S 000
I0 (t) ~
e-Lt + KL decay
“dilution” D is momentum dependent
look for interference term
35.0)()(
)()()(
00
00
KNKN
KNKNpD
| 000 |2 e-St + KS decay
2 D(p) (Re (000 ) cos mt – Im (000 ) sin mt) e-(S+ L)t / 2
KL – KS interference term
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
NA48/1: preliminary result for 000
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
CP-violation: indirect / direct ?
CP-violation first seen in KL decays (1964)
KL and KS are mixtures of CP-eigenstates K1 and K2
– KL = K2 + K1
– KS = K1 + K2
mixing responsible for most of the observed CP-violation– parameter – known since long ago
– see Michele Veltri’s talk for new measurement by NA48
but longstanding question: is there “direct” CP-violation?– K2 ??
– parameter ’
small effect need high-precision measurement !
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
the NA48 approach to measuring Re ’/
almost collinear neutral kaon beams (KL and KS )
same decay volume take all 4 modes at same time and place ! “weighting” of KL decay events with KS lifetime
– eliminate acceptance effects in first order
– reduce systematic effects at expense of statistics
distinguish KL and KS by “tagging” protons to “KS target”
“second experiment” in 2001– new drift chambers
– different spill structure and instantaneous beam intensity
– different beam energy
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
rare decays at NA48
“KL”-beam:– KL + - e+ e- indirect CP-violation
– KL +/- e-/+ 0 form factors, – phase shifts, chiral perturbation theory
– KL 0 CP-conserving contribution in KL e+ e- 0
– KL e+ e- form factors
– KL e+ e- background for KL e+ e- 0
– KL e+e- e+e- CP-eigenvalue of KL
“KS”-beam: 0 00 mass 0 non-leptonic weak interaction 0 0 0p- transversal -polarization
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
KS / KL 000 interference
dependence of interference on (phase of )
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
Dalitz decays: 0 e+e-
KS 0 e+e-
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
Kl3 decays and Vus
test of CKM unitarity– |Vud|2 + |Vus|2 + |Vub|2 = 0.9957 0.002 : deviation from unity
– |Vus| contributes nearly 30% of uncertainty
|Vus| calculated from (Ke3) and (K3)– K 0eand K 0– precise measurement will improve CKM unitarity test
Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck,
26 March 2004
charged kaon decays: the NA48 approach
cancellation of systematic effects is essential
adapt NA48’s proven concept:
simultaneous, collinear beams
use same detector without major modifications
beam particles are charged measure their momentum !