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Вторые Марковские чтения
Дубна-Москва, 12-13 мая 2004 г.
Редкие распады каонов
Ю.Г. Куденко
Институт ядерных исследований РАН
CKM матрица: K pnn и B распады
KL p0nn
K+ p+nn
Дубна, 12 мая 2004
1
CKM matrix
K and B decays as a test of the SM and CP-violation in the SM
- CP violating parameter
2
KL p0nn and K+ p+nn in SM
Flavor – changing neutral current decays
Br(KLp0nn) Im(VtdVts)2 1.8•10-102A4X2(xt) 2
Br(K+p+nn) e,,,|VcdVcsXlNL + VtdVtsX2(xt)|2 [(0 )2 + 2]
From isospin symmetry
Br(KLp0nn) 4.4Br(K+p+nn) 2x10-9
Theory SM
Br(KLp0nn) = (2.6 ± 1.2)x10-11
Br(K+p+nn) = (7.7 ± 1.1)x10-11
3
Unitarity triangle from B and K
Comparison of |Vtd| from K+p+nn and Ms/ Md
important test of SM
Comparison of sin2 from Br(KLp0nn)/Br(K+p+nn) and A(BJ/Ks)
definitive test of CP- violation in SM
4
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
A.Buras, hep-ph/0109197
review
G.Isidori, hep-ph/0101121
SUSY
T.Yanir, hep-ph/0205073
4th generation of fermions
M.S.Chanowitz, hep-ph/9905478
SU(2)Lx SU(2)R Higgs
C.-H.Chen, hep-ph/0202188
SUSY gluino exchange
A.Buras et al., hep-ph/0402112
non-SM
H.G.He, G.Valencia, hep-ph/0404229 right-handed Z’
Br(K pnn) x 1011
SM and beyond
27 (K+), 40 (K0)
60 (K+), 400 (K0)
2.8 – 10.6
15 (K+)
30(K0)/7.7(K+)
14(K0)/15(K+)
5
K+ p+nn
Measurement of K+ p+nn
Physics backgrounds
Decay
Region 2
BR
PID
K+ p+p0
K+ +n
K+ +n
K+ +p0n
K+ e+p0n
K+ p+p- p+
0.21
0.63
0.005
0.032
0.048
0.056
K+ p+nn
310-11 (SM)
+
+
+
+
-
veto
kinematics
++
+
++
++
+
+
+
++
Region 1
Only K+ p+nn produces pions with momentum 205 MeV/c
6
E787/E949 detector
7
Method
Experimental method
- 700 MeV/c K+ beam p/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 p+ in range stack
- detection p+ + e+ chain in RS
- veto photons and charge particles
8
Suppression of neutrals
GOAL: Observation of p+ in the momentum region
211 < p <229 MeV/c
+
no other detector activity
Average photon inefficiency 10-3 – 10-4
E949
E787
Suppresion of Kp K Ke3 K
Region 1
p0 detection inefficiency 10-6 for
photon threshold = 1 MeV
Supression: 1 10-3
p0 10-6
9
Backgrounds
K, K …
K
Signal box
Kp
10
p e chain
Suppression factor 10-5
Sample pulse height
every 2 ns
p+ stops in RS (2cm/layer)
p++n E = 4.1 MeV
R 1mm p = 26 ns
+ e+ nn Ee 53 MeV
= 2.2 s
11
K+ p+nn acceptance
E949 acceptance = 0.0022
12
Event display
No other concidence signal in detector
K+ p+nn event
range stack
p
T-counter
drift chamber
target
kaon pulse
13
Signal
all cuts applied
Signal region
Kp background
14
Result K+ p+nn
E949
Stopped kaons
1.8 1012
Total acceptance
0.22 0.02 %
Signal
1
Background
0.30 0.03
E949 + E787
K+ p+nn
1 + 2 (from E787) = 3
Br(K+p+nn) = (1.47 + 1.30 – 0.89) x 10-10 (hep-ex/0403036)
consistent with the SM predictions
0.006 < |Vtd| < 0.027 t = Vts Vtd = A25(1--i) 0.2410-3 <|t|< 1.0810-3
analysis below Kp peak is under way
15
KL p0nn
KL p0nn from kTeV
kTeV at FNAL: “pencil” KL beam
Dalitz decay mode p0 e+e- signal: pt > 160 MeV/c
Phys.Rev.
Br(KLp0nn) 5.9x10-7 (90% c.l.)
Phys.Rev.D61:072006,2000
16
KEK E391a
Expected sensitivity of 10-9 - 10-10
pencil beam
high acceptance
high PT for Kpnn selection
extreme photon veto efficiency
photon calorimetry
17
KOPIO
KOPIO experiment at BNL: Canada, USA, Russia (INR, IHEP), Japan, Italy, Switzerland
KL p0nn
at BNL
- Work in KL center of mass system using TOF
- Microbunched, large angle, low energy beam
- Measure photon direction
- Efficient photon detection
pK 0.7 GeV/c
flat beam
18
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
19
Photon and charged particle veto
Main backgrounds
KL p0 p0 and KL p e+n
Br 10-3
Two photons missed
Br 1.3x10-2
charged particle missed
second photon created
p0 inefficiency 10-4 x 10-4 = 10-8
20
KOPIO acceptance and backgrounds
Acceptance to KL p0nn
1%
KL p0nn at the SM rate
40
KL p0 p0
KL pen
KL p+ pp0
KL pen
KL p0 n
nA p0 X
Accidentals
Total background
12.4
4.5
1.7
0.02
0.02
0.01
0.2
0.6
19.5
KOPIO goal: B/B 20% 10% at S/B = 2
21
KOPIO 3D
22
Conclusion and perspectives
K pnn - a useful probe of new physics
K+ p+nn
KL p0nn
Theory
Experiment
(7.7 ± 1.1)x10-11
(14.7 + 13.0 – 8.9) x 10-11
(2.6 ± 1.2)x10-11
5.9x10-7 (90% c.l.)
CKM at FNAL
doubles sensitivity next year
final result 10 events (?)
100 events (?)
KOPIO
40 events
Perspectives:
E949
23
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