CKM%20???????:%20K%20?%20pnn%20?%20B%20???????

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?????? ?????????? ?????? ?????-??????, 12-13 ???
2004 ?.
?????? ??????? ??????

?.?. ???????

???????? ??????? ???????????? ???
CKM ??????? K ? pnn ? B ??????? KL ? p0nn
K ? pnn
?????, 12 ??? 2004
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CKM matrix
K and B decays as a test of the SM and
CP-violation in the SM
? - CP violating parameter


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KL ? p0nn and K ? pnn in SM
Flavor changing neutral current decays
Br(KL??0??) ? Im(VtdV?ts)2 ? 1.810-10?2A4X2(xt)
? ?2 Br(K????) ? ?e,,?,?VcdV?csXlNL
VtdV?tsX2(xt)2 ? (?0 ? ?)2 ?2
From isospin symmetry Br(KL??0??) ?
4.4Br(K????) ? 2x10-9
Theory SM Br(KL??0??) (2.6
1.2)x10-11 Br(K????) (7.7 1.1)x10-11
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Unitarity triangle from B and K


Comparison of Vtd from K???? and ?Ms/ ?Md
important test of SM Comparison of sin2? from
Br(KL??0??)/Br(K????) and A(B?J/?Ks)
definitive test of CP-
violation in SM
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K ? pnn beyond the SM
(Nir and Worrah, Phys. Lett. B319, 1998) Low
energy SUSY, Minimal Flavor Violation, Multiple
Higgs
K ? pnn beyond the SM Model
Br(K ? pnn) x 1011
A.Buras, hep-ph/0109197
review
SM and beyond G.Isidori, hep-ph/0101121
SUSY
? 27 (K), ? 40 (K0) T.Yanir,
hep-ph/0205073 4th generation
of fermions ? 60 (K), ? 400
(K0) M.S.Chanowitz, hep-ph/9905478
SU(2)Lx SU(2)R Higgs 2.8
10.6 C.-H.Chen, hep-ph/0202188
SUSY gluino exchange 15 (K)
A.Buras et al., hep-ph/0402112 non-SM

30(K0)/7.7(K) H.G.He, G.Valencia,
hep-ph/0404229 right-handed Z
14(K0)/15(K)
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Measurement of K ? pnn
K ? pnn
Physics backgrounds
Decay BR PID ??veto
kinematics K ? ??0 0.21 -
K ? ?? 0.63
- K ? ???
0.005 - K ?
??0? 0.032
- K ? e?0? 0.048
- K ? ??- ? 0.056 -
K ? ??? ? 3?10-11 (SM)

Region 1
Region 2
Only K ? ??? produces pions with momentum ?
205 MeV/c
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E787/E949 detector
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Method
Experimental method

• - 700 MeV/c K beam ?/K ? 1/3
• stop K in active target
• delay 2 ns for K decay
• momentum measurement in drift chamber
• ?p/p ? 2.5
• measurement of range R and energy E
• in target and range stack RS
• stop ? in range stack
• detection ? ? ? ? e chain in RS
• veto photons and charge particles

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Suppression of neutrals
GOAL Observation of ? in the momentum
region 211 lt p? lt229 MeV/c no other detector
activity
Average photon inefficiency ? 10-3 10-4
Suppresion of K?? K?? Ke3 K???
E949
Region 1
E787
?0 detection inefficiency ?10-6 for photon
threshold 1 MeV
Supression 1? ? 10-3
?0 ? 10-6
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Backgrounds
K??
K??, K???
Signal box
K??
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? ? ? ? e chain
Suppression factor 10-5
Sample pulse height every 2 ns ? stops in RS
(2cm/layer) ???? E? 4.1 MeV R? ? 1mm ??
26 ns ? ? e??? Ee ? 53 MeV ?? 2.2 ?s
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K ? pnn acceptance
E949 acceptance 0.0022
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Event display
No other concidence signal in detector
K ? pnn event
range stack
? ? ?
T-counter
drift chamber
kaon pulse
target
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Signal
all cuts applied
Signal region
K?? background
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Result K ? pnn
E949
Stopped kaons 1.8 ? 1012
Total acceptance 0.22 ? 0.02
Signal
1 Background 0.30 ? 0.03
E949 E787
K ? pnn 1 2 (from E787) 3
Br(K????) (1.47 1.30 0.89) x 10-10
(hep-ex/0403036)
consistent with the SM predictions 0.006 lt Vtd
lt 0.027 ?t V?ts? Vtd A2?5(1-?-i?) 0.24?10-3
lt?tlt 1.08?10-3
analysis below K?? peak is under way
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KL ? p0nn from kTeV
KL ? p0nn
kTeV at FNAL pencil KL beam
Dalitz decay mode p0 ? ee- ?
signal pt gt 160 MeV/c
Phys.Rev.
Br(KL??0??) ? 5.9x10-7 (90 c.l.)
Phys.Rev.D61072006,2000
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KEK E391a
Expected sensitivity of 10-9 - 10-10
pencil beam high acceptance high PT
for K???? selection extreme photon
veto efficiency photon calorimetry
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KOPIO
KOPIO experiment at BNL Canada, USA, Russia
(INR, IHEP), Japan, Italy, Switzerland
- Work in KL center of mass system using TOF -
Microbunched, large angle, low energy beam -
Measure photon direction - Efficient photon
detection
KL ? p0nn at BNL
pK ? 0.7 GeV/c
flat beam
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KOPIO detector
?? 500 ?sr, ?E (2-3)/?E(GeV), ?? 20-30
mrad, ?z ? 15 cm, ?t ? 50ps/?E(GeV), photon
veto ? 18X0,, ? inefficiency ? 2x10-4
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Photon and charged particle veto
Main backgrounds KL ? p0 p0 and KL ? p-
eng
Br ?? 10-3
Br ?? 1.3x10-2
Two photons missed
charged particle missed second photon created
?0 inefficiency ? 10-4 x 10-4 10-8
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KOPIO acceptance and backgrounds

• KL ? p0nn at the SM rate 40
• KL ? p0 p0
  12.4
• KL ? p?e??
  4.5
• KL ? p p-p0
  1.7
• KL ? p?e?
  0.02
• KL ? ? ?
  0.02
• ? p0 n
  0.01
• nA? p0 X
  0.2
• Accidentals
  0.6
• Total background 19.5

Acceptance to KL ? p0nn ?1
KOPIO goal ?B/B ? 20 ? ???? ? 10 at S/B 2
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KOPIO 3D
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Conclusion and perspectives
K ? pnn - a useful probe of new physics
Theory
Experiment K ? pnn (7.7
1.1)x10-11 (14.7 13.0 8.9) x
10-11 KL? p0nn (2.6 1.2)x10-11
? 5.9x10-7 (90 c.l.)
Perspectives E949 doubles sensitivity
next year
final result 10 events (?) CKM at FNAL
100 events (?)
KOPIO 40 events
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