Rare Kaon Decays: Opportunities for CERN

1
Rare Kaon Decays Opportunities for CERN
Short Introduction Present NA48/1 KS ? p0 ee
(mm) First Observations! NA48/2 K / K-
Data Taking in 2003/2004 Future NA48/3 K ?
p n n TODAY MAIN FOCUS NA48/4
KL ? p0 ee (mm) NA48/5 KL ? p0 n n

2
CP-Violation in SM
A phase in the CKM matrix leads to CP-Violation
Ng2 Nphase0 ? No CP-Violation Ng3
Nphase1 ? CP-Violation Possible

• Predictions
• Direct-CP Violation e/e ? 0 NA48, KTeV
• CP violation in the B meson sector ACP(J/y Ks),
  BaBar, Belle
• Paradigm shift
• Look for inconsistencies measuring the SM
  parameters using observables with small
  theoretical errors (lt 10)

3
Kaon Rare Decays and the SM
(holy grail)
CP-Violation
CP-Conservation
Kaons provide quantitative tests of SM
independent from B mesons
JCP2?(Triangle Area) is the unique measure of
CP-Violation in SM JCP
Im(VudVusVtsVtd) cosqc sinqc Im lt
Im lt A2 l5 h, Re lt A2 l5 r
4
Current Status
G. Isidori
STILL A LARGE WINDOW OF OPPORTUNITY EXISTS
5
NA48 Detector Data Taking
1996
Total 5.3M KL??0?0

• CERN SPS
• Magnetic spectrometer
• Liquid krypton EM calorimeter

NA48/2 K?
2004
6
The Past NA48
7
NA48 Re e/e14.7 2.2 ?10-4

• Top 10 articles from Physics Letters B
• 1. The hierarchy problem and new dimensions at a
  millimeter http//dx.doi.org/10.1016/S0370-2693(98
  )00466-3 Physics Letters B, Volume 429, Issues
  3-4 , 18 June 1998, Pages 263-272 Nima
  Arkani-Hamed, Savas Dimopoulos and Gia Dvali
• 2. A precision measurement of direct CP
  violation in the decay of neutral kaons into two
  pions http//dx.doi.org/10.1016/S0370-2693(02)0247
  6-0 Physics Letters B, Volume 544, Issues 1-2 ,
  19 September 2002, Pages 97-112 J. R. Batley et
  al. (NA48 Collaboration)
• 3. Has the GZK suppression been discovered?
  http//dx.doi.org/10.1016/S0370-2693(03)00105-9
  Physics Letters B, Volume 556, Issues 1-2 , 13
  March 2003, Pages 1-6, John N. Bahcall and Eli
  Waxman
• 4. Testable scenario for relativity with minimum
  length http//dx.doi.org/10.1016/S0370-2693(01)005
  06-8 Physics Letters B, Volume 510, Issues 1-4 ,
  21 June 2001, Pages 255-263 Giovanni
  Amelino-Camelia
• 5. Role of effective interaction in nuclear
  disintegration processes http//dx.doi.org/10.1016
  /S0370-2693(03)00801-3 Physics Letters B, Volume
  566, Issues 1-2 , 24 July 2003, Pages 90-97 D. N.
  Basu
• 6. Determination of solar neutrino oscillation
  parameters using 1496 days of Super-Kamiokande-I
  data http//dx.doi.org/10.1016/S0370-2693(02)02090
  -7 Physics Letters B, Volume 539, Issues 3-4 , 18
  July 2002, Pages 179-187 S. Fukuda et al.
• .

8
The Present NA48/1
9
KL? p0ee(mm)

• Before discussing KL decays later in the talk,
  one has to address
• CP-Conserving amplitude
• Very small for KL? p0ee , according to the NA48
  measurement of KL? p0 gg
• CP-Violating amplitude from K0-K0bar mixing
• A measurement of KS? p0ee(mm) is required
• ...it was exactly the goal of NA48/1

10
CERN-NA48/1 High Intensity KS
Converges to KLaxis at -0.6 mrad
11
NA48/1 KS ? p0 ee
KS ? p0 p0D?ggee(g)
KS ?p0 ee
MC
MC

• To reject the KS ? p0 p0D decays that may mimic
  KS ?p0 ee if a g is lost, a cut meegt0.165 GeV/c2
  is applied

12
NA48/1 KS ?p0 ee
e-e- (Odd Sign) DATA
e-e- DATA vs. MC
Blind Control Signal regions
meegg (GeV/c2)
mee (GeV/c2)
13
NA48/1 KS ?p0 ee
e-e- (Same Sign) DATA
e-e- DATA vs. MC
Search region
meegg (GeV/c2)
mee (GeV/c2)
14
NA48/1 KS ?p0 ee
Background from KL,S?eegg measured using NA48
KL data from 2001 N(KL?eegg, 2001) ? 10 N(KL,S
?eegg, 2002)
meegg(GeV/c2)
mgg(GeV/c2)
15
NA48/1 KS ?p0 ee
Accidental backgrounds
meegg (GeV/c2)

• DC proton beam
• Read out window 200ns
• Use time side band to measure background from
  time-overlapping fragments from different decays
• Major component
• epn p0p0(p0)
• Confirmed relaxing E/P cuts

mgg (GeV/c2)
16
NA48/1 KS ?p0 ee
SUMMARY OF BACKGROUNDS
Source Control Region Signal region
KS?p0Dp0D 0.03 0.007
KL,S ? eegg 0.11 0.075
pen2p0(p0) 0.19 0.069
Total 0.330.18-0.11 0.150.05-0.04

• Many other sources investigated and found to be
  negligible (e,g neutral cascade decays)
• Blind analysis Control and signal region
  remained masked until the study of the background
  was finished

17
NA48/1 KS ?p0 ee

• 7 candidates in the
• signal region
• 0 in control region
• Background 0.15
• The probability that all 7
• events are background
• is 10-10

meegg (GeV/c2)
mgg (GeV/c2)
First observation of KS ?p0 ee
18
The 7 KS?p0ee candidates
Meegg (GeV/c2)
t/tS
Mgg (GeV/c2)
Mee (GeV/c2)
19
NA48/1 KS ?p0 ee
PL B576 (2003) hep-ex/0309075
BR(KS?p0ee, meegt165 MeV/c2) (3.01.5-1.2(stat)
0.2(syst))10-9

• Assuming vector interaction and unity form
  factor
• In remarkable agreement with L. Sehgal
  prediction 5.5 10-9 NP B19 (1970)

BR(KS?p0ee) (5.8 2.8-2.3(stat)
0.8(syst))10-9
20
NA48/1 KS ?p0 mm

• Study of backgrounds from KL? p0pp- ? p0
  (mn)(mn)
• MC 22 times the data
• None of the simulated events falls in the signal
  box

21
NA48/1 KS ?p0 mm

• Backgrounds from Neutral Cascade decays are
  rejected using a Momentum ratio cut
• Radiative (mmgg) backgrounds
• 0.04 0.04 events

22
NA48/1 KS ?p0 mm
Study of accidental
backgrounds

• KL ?p m n KS ?p0(p0)
• KS?pp- KS ?p0(p0)
• Studied in time side band
• 6 events in 125 ns
• 0.18 0.18-0.11 background events expected in the
  in time signal region

23
NA48/1 KS ?p0 mm

• BR(KS?p0mm) ? 109 2.9 1.4-1.2(stat)
  0.2(syst) La Thuile 2004

First Observation! 6 events Expected
back. 0.22019-0.12
24
Dilepton invariant mass distributions
NA48/1
NA48/1
25
Extraction of form factor

• VMD bs/as 0.4
• Data compatible with VMD
• Too low statistics to
• extract the two parameters

• Assuming VMD
• BR(KS ?p0 ee) 5.2 as2 ? 10-9
  aspee 1.06 0.26 -0.21
  0.07
• BR(KS ?p0 mm) 1.2 as2 ? 10-9
  aspmm 1.55 0.38 -0.32
  0.05

26
Prediction using SM fit and NA48/1 result
See Buchalla,Isidori,DAmbrosio for updates
hep-ph/0308008
27
The Present NA48/2
28
NA48/2 K/K-

• Search for direct CP violation
• in Dalitz plot slope asymmetry
• in K ? ?? decay
• Ke4 decays
• Rare K decays

NA48/2 takes data also in 2004
NA48/2 Very Preliminary
K ? p ee
Simultaneous K and K- beams
29
The Future NA48/3 K?p nn
30
Importance of Villars SPSC Meeting

• From the address of R. Aymar, CERN CEO, to
• the CERN staff on 13/1/04
• 4. Another goal for 2004-2010 would be
• To define possible new fixed-target experiments,
  highly praised at another Cogne meeting in
  September 2004
• To decide in 2006 on the possible planning and
  the
• start of implementation of the Linac 4 and/or any
  
• proposed RD or experiment, depending on the
• funds available or expected at that time...

31
Implications of Villars

• Focus on a programme that can have a big impact
  (dont be modest)
• The reviewers will have a close look at the
  physics potential
• Aim to a 10 measurement of Vtd via K ? p n n
• Since the time is very tight, use what is best
  best known
• Start from NA48/2 and extrapolate to the ultimate
  experiment
• To have a proposal evaluated by a Scientific
  Committee takes time
• To seek approval in 2006 and take data in 2008
  one has to act now
• Express Interest now in order to protect assets
  such as
• Availability of ECN3 (the only high radiation
  area for SPS)
• Availability of high intensity, slowly extracted
  protons from SPS
• LKr calorimeter
• Beam test as many things as possible in 2004
  before the planned stop of the SPS in 2005
  (2006?)

32
K?p nn Theory

• The hadronic matrix element can be extracted from
  
• the well measured K? p0 e n
• No long distance contributions

QCD NLO Buchalla, Buras 1999
As an example, within the SM, using ACP(J/?KS)
and ek as input BR(K ?
pnn) 7.1 1.0 10-11
(Kettell, Nguyen, Landsberg, hep-ph/0212321 )
33
K?p nn Experiment
Region I
Region II
p
in the K CM
34
State of the artAGS-E787/E949 K?p nn
35
AGS-E787/E949 K?p nn
hep-ex/0403036
BR(K ? p nn ) 1.471.30-0.89 10-10
(SM0.7 10-10)
36
K?p nn E949

• Run 12 weeks in 2002
• Result just released
• Plans to collect more data
• to reach 10 events _at_ SM
• by 2010?
• Plans to continue with the stopped kaon technique
  at J-PARC?

37
CKM_at_FNAL-MI

• Proposal to measure 100 K? p n n in flight
• Make redundant measurements spectrometer and
  RICH
• 22 GeV/c separated kaon beam
• TURNED DOWN BY P5 HEPAP SUB-PANEL FOR COST
  REASONS (100 MUSD)

38
CKM_at_MI22 GeV/c Separated Kaon beam

p0 from K?p0p of soft energy ? not easy to
veto In addition p0 is backward in CM ?very
bulky vetoes Are required
39
NA48/3

• Build on the NA48/2 infrastructure and detectors
  to save on cost
• Use a high energy (un-separated) kaon beam to
  simplify the rejection
• of K ? pp0

40
K?p nn NA48/3 (75 GeV/c)
K? mn
Region I
K? p nn
Region II
K? ppp-
K? pp0
41
NA48/3 Layout 0.0

• Unseparated, positive beam of 75 GeV/c with
  DP/P1
• Detectors upstream of the decay region
• Differential Cherenkov counter (CEDAR) to
  positively identify kaons
• Beam spectrometer to make a redundant momentum
  measurement and to measure the kaon direction
  (KABES)
• It requires 100 ps time resolution. We are
  investigating
• Micromega-type chambers (already employed in
  NA48/2)
• Silicon micro-pixel detectors
• Detectors Downstream of the decay region
• Double magnetic spectrometer for redundancy (with
  Chinese copy of NA48 dipole)
• Charged hodoscope for timing
• Hermetic photon vetoes (upgrade NA48 ring
  anti-counters)
• High performance forward photon veto (NA48 LKr
  calorimeter)
• Finely segmented Hadron Calorimeter/Muon veto

42
NA48/3 Beam layout
43
Some documentation is available on the Web (
http//cern.ch/doble )
Beam Documentation for NA48
Please find below the updated geometry files
(Beatch) for the P42 and K12 beams to NA48
. . . . . . .
K12HIKA (dated 18/03/04) represents the latest
tentative attempt to describe the layout of a
high- acceptance, small momentum-bite (75.0?0.7
GeV/c) K beam for a possible future K -gt pi nu
nubar experiment (NA48/3). The beam is derived
from the existing target station T10 along the
present K12 beam line of length 102.0m to the
exit of the final collimator. It features
large-acceptance, radiation-resistant
quadrupoles, a front-end achromat for momentum
definition, a beam cleaning stage and a parallel
section, incorporating a CEDAR differential
Cerenkov counter to tag the K, followed by a
second achromat accommodating 3
spectrometertracking stations KABES(1),(2)(3).
For the measurement of the decay pi, the last
12m section of the decay-vacuum tank (blue tube)
has been replaced by an additional (first)
spectrometer comprising detectors WC 1,2, 4 fore
and aft of a (new) MNP33-1 magnet, followed by
the present (second) spectrometer comprising WC
3, 5,6 and the present MNP33-2 magnet, giving
pT-kicks of -210 MeV/c (deflecting the beam by
-2.8mrad.), respectively, resulting in a 35 mm
parallel displacement inside the beam tube.
Photon veto counters with radial coverage of,
respectively, 40 lt r lt 90mm (PHOT.VETO1) and r lt
90mm (PHOT.2) are shown in front of the Kevlar
window and at the end of the hall - following a
10 mrad. beam deflecting magnet (MBPL101245)
installed in place of the HAC.
44
Turtle simulations
1HISTOGRAM NO 21 DISTRIBUTION OF P IN GEVC
102.000 M FROM THE
TARGET0 INTERVAL
SCALE FACTOR.. 100 X'S EQUAL 5637
ENTRIES0LESS THAN 72.000 0 72.000
TO 72.200 0 72.200 TO 72.400
0 72.400 TO 72.600 0 72.600 TO
72.800 0 72.800 TO 73.000 1
73.000 TO 73.200 20 73.200 TO 73.400
178 XXX 73.400 TO 73.600 576
XXXXXXXXXX 73.600 TO 73.800 1210
XXXXXXXXXXXXXXXXXXXXX 73.800 TO 74.000
2068 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
74.000 TO 74.200 2870 XXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 74.200 TO
74.400 3727 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 74.400 TO
74.600 4598 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
74.600 TO 74.800 5354
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
74.800 TO 75.000 5637 XXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 75.000 TO
75.200 5596 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXX 75.200 TO 75.400 5126
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
75.400 TO 75.600 4288 XXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXX 75.600 TO 75.800 3400
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXX 75.800 TO 76.000 2623
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
76.000 TO 76.200 1820 XXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXX 76.200 TO 76.400 1068
XXXXXXXXXXXXXXXXXX 76.400 TO 76.600 552
XXXXXXXXX 76.600 TO 76.800 250
XXXX 76.800 TO 77.000 61 X 77.000
TO 77.200 8 77.200 TO 77.400
0 77.400 TO 77.600 0 77.600 TO
77.800 0 77.800 TO 78.000
00GREATER THAN 78.000 00 TOTAL
NUMBER OF ENTRIES 51031 INCLUDING
OVERFLOW AND UNDERFLOW0 MEAN 74.981
RMS HALF WIDTH 0.7100HISTOGRAM NO 21
DISTRIBUTION OF P IN GEVC
102.000 M FROM THE TARGET
Momentum distribution ltpgt 74.981 GeV/c, RMS
0.710 GeV/c
45
-60.000 -20.000 20.000 60.000
TOTALS I------------------I-
--------60.000 I
I 0-54.000 I
I 0-48.000 I
I 0-42.000 I
I 0-36.000 I
I 0-30.000 I
I 0-24.000 I 8TA
I 932-18.000 I AA
I 5407-12.000 I ZZ
I 8326 -6.000 I
I 9999 0.000 I
I 9999 6.000 I WW
I 8536 12.000 I 4G
I 5529 18.000 I 3QT2
I 787 24.000 I
I 0 30.000 I
I 0 36.000 I
I 0 42.000 I
I 0 48.000 I
I 0 54.000 I
I 0 I------------------
I-------- I
I I 134455554431
I I 15428485392461
I I 59077738177357
I TOTALS I 0000000078559573710077
00000000 I 9999 TOTAL NUMBER OF
ENTRIES 51031
-60.000 -20.000 20.000 60.000
TOTALS I------------------I-
--------60.000 I
I 0-54.000 I
I 0-48.000 I
I 0-42.000 I
I 0-36.000 I
I 0-30.000 I
I 0-24.000 I 2AQOF1
I 397-18.000 I
I 4016-12.000 I 14
I 8053 -6.000 I 22
I 9999 0.000 I 32
I 9999 6.000 I
I 8186 12.000 I 2
I 4102 18.000 I 2GSF2
I 396 24.000 I
I 0 30.000 I
I 0 36.000 I
I 0 42.000 I
I 0 48.000 I
I 0 54.000 I
I 0 I------------------
I-------- I
I I 2456666542
I I 631337614046
I I 7435062357861
I TOTALS I 00000000668218733483200000
0000 I 9999 TOTAL NUMBER OF ENTRIES
51031
KABES-2

-60.000 -20.000 20.000 60.000
TOTALS I------------------I-
--------60.000 I
I 0-54.000 I
I 0-48.000 I
I 0-42.000 I
I 0-36.000 I
I 0-30.000 I
I 0 -24.000 I 4HK5
I 603-18.000 I 3
I 5010-12.000 I HK
I 8414 -6.000 I HH
I 9999 0.000 I LH
I 9999 6.000 I AE
I 8483 12.000 I 6
I 5058 18.000 I 4LH3
I 590 24.000 I
I 0 30.000 I
I 0 36.000 I
I 0 42.000 I
I 0 48.000 I
I 0 54.000 I
I 0 I------------------
I-------- I
I I 134456555431
I I 213971951312
I I 61257420138277
I TOTALS I 00000000899915863673340000
0000 I 9999 TOTAL NUMBER OF ENTRIES
51031
KABES-1
KABES-3
46
Spot at Wire Chamber 1
1HISTOGRAM NO 29 HORIZONTAL AXIS X IN MM
204.858 M FROM THE TARGET
VERTICAL AXIS Y IN MM
204.858 M FROM THE TARGET0
-60.000 -20.000 20.000 60.000

TOTALS I------------
------I-------- -60.000 TO -54.000 I
I 0 -54.000 TO
-48.000 I I
0 -48.000 TO -42.000 I
I 0 -42.000 TO -36.000 I
I 0 -36.000 TO -30.000
I 2321 11 I 10
-30.000 TO -24.000 I 159XTSJE73
I 334 -24.000 TO -18.000 I
8U72 I 1947 -18.000 TO
-12.000 I 1ED I
4900 -12.000 TO -6.000 I
GJ1 I 8143 -6.000 TO
0.000 I 1LI2 I 9999
0.000 TO 6.000 I G82
I 9984 6.000 TO 12.000 I
GE1 I 8252 12.000 TO
18.000 I FE1 I 4901
18.000 TO 24.000 I AVX7
I 1929 24.000 TO 30.000 I
2ERYVWQSPFF5 I 254 30.000 TO
36.000 I 21 1 1 I 5
36.000 TO 42.000 I
I 0 42.000 TO 48.000 I
I 0 48.000 TO 54.000 I
I 0 54.000
TO 60.000 I I
0 I---------------
---I-------- I
I
I 1356776531 I
I 15731887723651
I I
16166042762880 I
TOTALS I 000000027056033304565390000000 I 9999
0 TOTAL NUMBER OF ENTRIES 51031
INCLUDING UNDERFLOW AND OVERFLOW AS FOLLOWS 0
UNDERFLOW
OVERFLOW ACROSS
0 0 DOWN
0 00HISTOGRAM NO 29
HORIZONTAL AXIS X IN MM
204.858 M FROM THE TARGET VERTICAL AXIS
Y IN MM 204.858 M FROM
THE TARGET
47
Possible new high-intensity K beam for NA48/3
(K?pnn)
Beam Present K12 (NA48/2) New HI K gt 2006 Factor gain wrt 2004
SPS protons per pulse 1 x 1012 3 x 1012 3.0
Duty cycle (s./s.) 4.8 / 16.8 1.0
Beam acceptance H,V (mrad) ? 0.36 ?2.4, ?2.0
Solid angle (msterad) ? 0.40 ? 16 40
Av. Kmomentum ltpKgt (GeV/c) 60 75 K 1.50 p 1.35 Total 1.35
Momentum band DpK (GeV/c) Eff. (Dp/p in ) RMS (Dp/p in ) 57 63 6 5 ? 4 73.9-76.12.25 1.5 ? 0.95 0.375 0.3 0.25
Beam size (cm) Area at KABES (cm2) 1.5 ? 7.0 2.5 ? 20 ? 2.8
Divergence RMS (mrad) ? 0.05 ? 0.1 ? 2
48
Possible new high-intensity K beam for NA48/3
- page 2
Beam Present K12 (NA48/2) New HI K gt 2006 Factor gain wrt 2004
Decay fid. length (m) (tK) 50 0.11 50 0.09 0.8
Beam flux/pulse p (x 107) K p e 0.86 0.31 3.32 0.95 49 15 150 35 50 (30) 45 (27)
Total per pulse (x 107) per Effective spill length (MHz) / / cm2 (KABES) (MHz) 5.5 18 2.5 250 800 40 45 (27) 45 (27) 16 (10)
Eff. running time / yr (days) (pulses) ½ 120 3.1 105 2/3 90 3.1 105 1.0
K decays per year inside fiducial length 1.0 1011 4 1012 ? 40
49

Detector Layout
50
(No Transcript)
51
NA48/3 Acceptance (Region I)
Not Even Preliminary!
E. Goudzovski
5 acceptance would translate into 20
events/year _at_BR10-10
52
NA48/3 Kaon Spectrometer

• Currently used in NA48/2 micromega via TPC
  read-out (KABES)

NA48/2 _at_ 2 MHz/strip Resolution strips 80
mm Risolution drift 50 mm Time resolution
0.7 ns Dead Time/strip 40 ns DP/P
0.5

• The expected rate per strip
• in NA48/3 is about 10 times larger
• New micro-mesh (25 micron)
• FADC
• smaller strip size
• New gas
• Must test all of the above (2004?)

53
CEDAR

• Db/b 1/2p (m22 m12)

54
CEDAR
55
CEDAR
56
Kinematical Rejection
F. Marchetto
mm2
pp0
mn
region 1
P(p) (GeV/c)
Region 1 -gt signal region -gt mm2 in the range
between 0 and 0.01 (GeV/c2)2
mm2 MK2 mp2 2 ( EKEp pKpp cosq) instead
of mm2 MK2 mm2 2 ( EKEm pKpp cosq) 0
57
mn
pp0
10 GeV
20 GeV
mm2
F. Marchetto

• I 1200 A
• K smeared with
• sp 0.5 GeV/c
• sq sf 15 mrad
• being the angular resolution of the spectrometer
  17 mrad

30 GeV
40 GeV
60 GeV
50 GeV
58
Double spectrometer geometry
Mag1
Mag2
Kevlar
DCH1
DCH2
DCH3
DCH4
DCH5
DCH6
x
q
z
2m
10m
10m
10m
2.5m
2.5m
2.5m
2.5m
G. Ruggiero
59
Alternative layout
Kevlar
Mag1
Mag2
DCH1
DCH2
DCH3
DCH4
DCH5
DCH6
x
z
11m
9m
9m
2.5m
2.5m
2.5m
2.5m
G. Ruggiero
DCH1

• Straw tube in vacuum X and Y view
• Compass straw tube (real)
  per view
• CKM straw tube (immaginary)
  per view

60
Square missing mass resolution

• 50 improvement at
• low momenta
• Better use of P measurement
• redundancy

7 m
Single spectrometer
9 m
Double spectrometer
G. Ruggiero
61
Photon Rejection
Energy distribution of the photon closer to beam
axis
Eg (GeV)
L. Di Lella
62
Photon Vetoes (KAMI)
63
Muon Vetoes
64
Tests in 2004

• KABES
• 25 mm Micro-mega mesh
• 1 Ghz FADC read-out (24 channels recuperated
  from the old NA48 proton tagger)
• Silicon micro-pixels in beam similar to final
  beam
• CEDAR
• Test in M2 hadron beam (Compass)
• Photon vetoes
• Install small angle calorimeter
• Drift chamber rate test (HV vs. resolution)

65
Far Future NA48/4 KL? p0ee (mm)
66
State of the art KTeV KL? p0ee
Full Statistics 19971999
1999 data
BR(KL ? p0 ee ) lt 2.8 10-10 _at_90CL

• SES 10-10
• Tantalisingly close to the SM prediction
• But progress is slow due to radiative
  backgrounds from KL?eegg

67
NA48/4 KL?p0ee(mm)

• Detector s(gg) 2
• Very ambitious, KTeV/NA48 already state of the
  art
• KS-KL time dependent interference 2
• Position experiment between 9 and 16 KS lifetimes
  
• (hep-ph/0107046)
• KS-KL time independent interference 3
• Assume constructive interference (theoretically
  preferred)
• Data Taking 5
• Run in factory mode. After all E799-II run
  only for a few months to collect 7 1011 KL
  decays
• Beam intensity 4
• Need 1012 protons/sec, slowly extracted, high
  energy, DC
• Tot 240 ? sens on BR 15 (on Im lt
  4-15)
• close the gap between current upper limit and SM

68
Far future NA48/5KL?p0nn
69
KL ? p0 n n (reminder)

• Theoretical error 2
• Purely CP-Violating (Littenberg, 1989)
• Totally dominated from t-quark
• Computed to NLO in QCD (e.g. Buchalla Buras,
  1999)
• No long distance contribution SM3 10-11

• Experimentally 2/3 invisible final state !!
• Best limit from KTeV using p0?eeg decay

BR(K0 ? p0nn) lt 5.9 10-7 90 CL
Still far from the model independent limit
BR(K0 ? p0nn) lt 4.4 BR(K ? pnn) 7 10-9
Grossman Nir, PL B407 (1997)
70
E391a_at_PS-KEK

• First dedicated experiment to search for KL? p0
  nn
• SES 3 10-10
• Based on pencil kaon beam and photon vetoes
• Scheduled for 100 days KEK PS beam in 2004
• This is a Stage I project for further study at
  J-PARC

71
KOPIO_at_BNL

• Aim to collect 60 KL? p0 nn
• events with S/B2 (Im lt to 15)
• Measure as much as possible
• Energy, Position and Angle for each photon
• Work in the Kaon Center of Mass
• Micro-bunched AGS beam
• Use TOF to measure KL momentum
• Start construction in 2005?

72
NA48/5 KL?p0nn
From KAMI proposal
E391A
J-PARC
NA48/5
CERN may become competitive if the E391A
technique works
73
A forward look.
K? p nn to 10
eK
K0-K0bar mixing
KL? p0 nn (ee,mm)
sin 2b
Vub
B tree decays
74
NA48-future_at_cern.ch