Transcript Kaon Physics: Experimental Status and Perspectives

Kaon Physics:
Experimental Status and
Perspectives
Marco S. Sozzi
CERN and
Scuola Normale Superiore, Pisa
FPCP 2003, Paris – June 5th 2003
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Outline
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Re(’/): the quest for direct CP violation
Rare KL decays and CP violation
Rare KS decays and CP violation
T-odd correlations: beyond the SM
Loop-induced decays and unitarity triangle
Future projects
Conclusions ?
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Still kaons?
• The “minimal” flavourlaboratory
• An amazing interferometric
system
• Long lifetime, few decay
modes, large mixing
• Both mass and flavour
eigenstates accessible
• All kinds of CP violation
present
• Difficulties in linking
measurements to theory
(not always!)
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
The Quest for
Direct CP Violation
Indirect CP violation in
the mixing:

Direct CP violation in
the decay: ’
A fascinating 30-year long
enterprise: “Is CP violation a
peculiarity of kaons? Is it
induced by a new superweak
interaction?”
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
E832 (KTeV) at FNAL
Double KL beams (<p>=70 GeV/c)
Regenerator for KS
Pure CsI calorimeter
Tagging by event position
MC acceptance correction
Maximize statistics
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
NA48 at CERN
Simultaneous near/far targets
Converging beams (<p>=100 GeV/c)
Liquid Kr calorimeter
Tagging by time-of-flight
Lifetime weighting to minimize
acceptance correction
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Data Taking Periods
Total: 5.3M KL00
1996
NA48: ’/
1997
’/
1998
’/
KS 1999
no spectrometer
KL
’/
KS
low intensity KS
’/
’/
Rare
Rare
2000
FNAL-KTeV
2001
Total: 7.1M KL00
NA48/1: KS
2002
NA48/2: K
2003
CERN-NA48
June 5th, 2003
’/
Rare
M. Sozzi - Kaon physics
= ’/ results
FPCP 2003, Paris
Ways towards direct CPV
NA48:
TOF tagging
KTeV: MC
incoherent
regeneration
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Re(’/) Results
( K 0     )  ( K 0     )
 (5.04  0.82) 106
0
 
0
 
 ( K    )  ( K    )
Final result (1997-2001)
Half statistics (1997)
Direct CP violation
proved at >7 level…
after 36 years!
Wait for further results from
KTeV and KLOE
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Re(’/) and the SM
SM theoretical predictions
Exp. value
Date of exp. measurement
Despite huge efforts, ’/ not yet computed reliably
Measured value is roughly compatible with the SM
Expect improvements from lattice
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Other kaon Parameters
KTeV
m = (5261  15)  106 ħ s-1
S = (89.65  0.07)  10-12 s
+SW = (0.61  1.19)º
00 += (0.39  0.50)º
Im(’/) = (22.9  29.1)  10-4
CPT
NA48: S = (89.60  0.07)  10-12 s
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Semileptonic Charge Asymmetry
Measure of indirect CP violation in the
mixing () and limits on CPT and S=Q
NA48
2  108 events in 2001 run
L(e) = (3.317  0.070  0.072)  10-3
KTeV
3  108 events in 2001 run
L(e) = (3.322  0.058  0.047)  10-3
CPT test using  data: Re(y+x/2+a) = ( 5  31)  10-6
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KLOE at DANE
(KS +())/(KS 00) = (2.236  0.003  0.015)
from which 0   2  (48  3)
(2000 data)
BR(K   00) = (1.807  0.008  0.018)%
Good prospects for rare KS decays, interferometry, new IR
Peak luminosity:
81031 cm-2 s-1 in 2002
Goal: 51032 cm-2 s-1
500 pb-1 (1.5 109 )
collected so far
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KLOE results
Using KL-crash tagging of KS:
(2001 data)
KS semileptonic charge asymmetry
S = (1.9  1.7  0.6)  10-2
Re(x+) = (3.3  5.2  3.5)  103
Preliminary
S=Q in CPT-conserving amplitudes
BR(KSe) = (6.81  0.12  0.10)  10-4
K+e3 K0e3 K+m3 K0m3
Vus
E865
QM interference
KLOE KS
KS KL  
|Vus|f+(0)
t
June 5th, 2003
M. Sozzi - Kaon physics
KLOE KL
FPCP 2003, Paris
E799-II (KTeV): Rare KL decays
Intense KL flux allows sensitive searches; checks of PT
KLe+e- (1997, 93K events – norm. 000D):
Preliminary
BR(KL  e+e-) = (10.13  0.04  0.06  0.29norm)  10-6
KL e+e- e+e- (1997+1999, 1K events – norm 00D0D):
Preliminary
BR(KL  e+e-e+e-) = (4.07  0.12  0.11  0.16norm)  10-8
no CP violation found in decay plane asymmetry
KLe+e-m+m- (1997+1999, 132 events – norm +-0D):
BR(KL  e+e- m + m-) = (2.69  0.24  0.12)  10-9
New results expected soon with full 1997+1999 data sample:
KL e+e- e+e- and KLe+e- form factors, KL +- e+e- update
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KL,S  ee : why?
CPV inner bremsstrahlung
CPV direct emission
June 5th, 2003
CPC direct emission
Charge radius
M. Sozzi - Kaon physics
For KL: interference gives
indirect CP-violating
asymmetry in the
orientation of  and
ee decay planes
Easier access to
polarization asymmetry in
K  
Large ( 14%)
asymmetries predicted
FPCP 2003, Paris
KL,S  ee
A = (13.3  1.7)%
1.5K events
BR = (3.63  0.18)  10-7
[NA48:
A = (14.2  3.6)%]
[NA48: BR = (3.08  0.2)  10-7]
BR = (4.69  0.30)  10-5
No asymmetry:
A = (1.1  4.1)%
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
NA48/1 – Rare KS decays
First measurement of KS  0
31 events, 13.6 background
BR(KS  0)z>0.2 = (4.9  1.6  0.8)  10-8
30% higher than PT prediction
Not yet sensitive to
chiral structure of
weak vertex
BR(KS  ) = (2.78  0.02  0.04)  10-6
For both: first contribution at O(p4) in PT
Indications of large O(p6) terms
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
NA48/1 - Search for KS  0e+eDetermines indirect
CP-violating contribution to
KL  0e+e- decay
Signal region
Published limit from 1999 data:
BR(KS  0e+e-) < 1.410-7
(90% CL)
2001 KS run data analyzed - Result available very soon
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Search for KS  30
000
A( K S  3 0 )

A( K L  3 0 )
CPLEAR (1999)
Re(000) = 0.18  0.15
Im(000) = 0.15  0.20
I 3 0 (t )  e
L t
Expectation  
Im (000) sensitive to direct CPV
SND, Novosibirsk (1999)
BR(KS30) < 1.410-5
 000 e S t 
2
2 D( p)Re(000 ) cos(m t)  Im(000 ) sin(m t)e ( S L )t / 2
Hadron machines: search for interference term
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
NA48/1: KS  30
Re(000) = (2.6  1.0  0.5)  10-2
Im(000) = (3.4  1.0  1.1)  10-2
•Data from 2000 run
•Use near-target data:
6.5M 30 events
•Normalize to far-target data:
155M 30 events
•Correct residual acceptance
difference with MC
June 5th, 2003
Im(000) = (1.2  0.7  1.1)  10-2
BR(KS30) < 1.410-6 (90% CL)
M. Sozzi - Kaon physics
FPCP 2003, Paris
CPT Test From KS  30
Bell-Steinberger relation (unitarity) connects
indirect CPT violation  to CP-violating decays
(1  i tanSW )Re( )  i Im( )   f
tanSW 
2m
S  L
f
 f  1/ S  A(KL  f ) A* (KS  f )
Largest contribution to the error from f = 30
After NA48/1: Im() = (1.2  3.0)  10-5
Assuming no CPT violation in the decay:
m(K0)  m(K0) = (1.7  4.2)  10-19 GeV/c2
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KEK E246: T-violation in K+  0m
Search for PT(m) orthogonal to (m) decay plane
FSI in SM give PT < 10-5: probe of New Physics
660 MeV/c kaons stopped in absorber
Combined result from 8.3M decays (1996-2000):
PT(m) = (-1.12  2.17  0.9)  10-3
LOI to reach 10-4 accuracy at J-PARC
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
NA48/2 – K decays
0º prod. angle
60 GeV/c  5%
Beam
spectrometer
New simultaneous K+ and K- narrow band beam
Kaon momentum spectrometer
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
NA48/2 – K physics
Search for direct CP violation in K  + and 00
Dalitz plot slope asymmetries:
(g/2g)  210-4
(SM, SUSY: 10-4 to 10-6)
Exploit “double ratio” cancellations
Precise measurement of  interaction in Ke4 decays (>106)
(a00)  0.01
Rare K decays and CP violation
1011 K decays expected
Currently taking data
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
OKA @ Protvino - K
New RF-separated beam at U-70 PS in construction
15 GeV/c kaons, alternating K+ or KMagnetic detector evolved from ISTRA+, GAMS
In preparation, expected 2004
Measurement of 3 Dalitz plot asymmetries @ 1 10-4
T-odd correlations, search for New Physics in Kl2 decays
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
HyperCP: K  mm
Main goal: CP violation in hyperon decays
Collected large samples of K decays
K  mm: FCNC
GIM-suppressed loops
Dominated by longdistance effects
From 1997
statistics (1/5):
June 5th, 2003
BR(K  mm) = (9.8  1.0  0.5)  10-8
A(K  mm) = 0.02  0.11  0.04
M. Sozzi - Kaon physics
FPCP 2003, Paris
The golden modes: K  
FCNC, loop-induced,
GIM-suppressed in SM
Sensitive to New Physics
MOREOVER:
No long-range contributions
QCD corrections under control
Single Heff operator with
matrix element linked to Ke3
BUT:
BR  10-11, unconstrained kinematics, huge backgrounds
Dedicated efforts required!
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Kaons and the unitarity triangle
Comparison to B
constraints (10% on BR):
•Errors on , Vtd:
better from B
•Errors on , sin2:
similar to B-factories
•Error on t:
always better from K
A. Buras, hep-ph/9905437
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
The rare decays KL  0l+lThree contributions:
1) CP-conserving through KL  0**
estimate from KL  0 (KTeV/NA48
disagreement?)
2) Indirect CP-violating through KS  0l+lNot suppressed, unlike the  case:
measure from KS  0l+l- (NA48 for e+e- )
3) “Direct” CP-violating, short-distance, reliably predicted and
interfering with (2): BR=4.310-12 (e+e-), 0.910-12 (m+m-).
(3) is smaller by  5 for the m+m- case
“Greenlee” background KL  l+l- : BR=610-7 (e+e-), 1 10-7 (m+m-)
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Exp. Limits from KTeV
(90% CL):
BR(KL  0e+e-) < 2.810-10
BR(KL  0m+m-) < 3.810-10
Measurement requires
accurate background
subtraction
Measured BR 10-12
KL  0e+e
L. Littenberg, hep-ex/0212005
BR(Direct CPV) 10-12

BR(KL   0ee )CPV  1012 15.3aS2  6.8aS Im(t ) 104  2.8 Im(t )2 108
t  Vts*Vtd
June 5th, 2003
aS  1 expected
M. Sozzi - Kaon physics
FPCP 2003, Paris

BNL E787: K+  +
Theoretical prediction in the SM:
BR(K+  +) = 7.2 10-11
with small ( 7%) uncertainty
Stopped K, redundant measurements
Detection of me chain
Momentum region between  and m peaks
Final result: 2 events (0.15 bkg.)
BR(K+  +) = 1.56+1.750.82 10-10
Improved successor BNL E949 ran in 2002
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Future: CKM at FNAL
In-flight measurement
RF-separated 22 GeV/c K+
beam
Redundant measurements
to overconstrain kinematics
(spectrometers + RICHs)
Progress on RF-cavities,
photon vetos, straws in
vacuum
Goal: 100 SM events in
2 years (S/B  10)
Data taking in 2007
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KL  0
No CP-conserving term
Indirect CP-violating term
negligible
Theoretical prediction within
the SM:
Model independent bound
BR(KL  0) = 2.710-11
With tiny ( 2%) uncertainty
Current KTeV limit:
BR(KL  0) < 5.9 10-7 (90% CL)
Using 0  e+e- decay
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KEK E391a: KL  0
Pilot project at KEK-PS
2 GeV/c “pencil” beam: PT cut against 00
to reduce veto requirement to 10-4
Double decay chamber, 10% acceptance
“Engineering run” in fall 2002:
CsI calibration, KL00, 000
First data run in 2004 (4 months)
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KL  0 at J-PARC
J-PARC schedule: physics start in 2008
50 GeV (30-40 at start) 21014 p/3.42 s
2 beam lines foreseen in K-hall
2 GeV/c KL (1.1109/pulse)
16% acceptance
Goal: 1000 SM events
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KOPIO at BNL : KL  0
800 MeV/c microbunched
kaon beam
Pb-scint. veto system (10-4)
complemented by:
KL momentum from TOF
 direction from pre-radiator
(wires+scint. layers)
“Pancake” beam
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KOPIO at BNL
Several feasibility results achieved:
Beam bunching performance proved
(280 ns, goal: 200 ns)
25 mrad resolution with preradiator
Veto efficiency performances
Construction from 2006
Expect 40 SM events (S/B  2)
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
How is kaon physics?
CERN: NA48 (KL) NA48/1 (KS) analysis, NA48/2 (K) running
FNAL: KTeV (KL) and HyperCP (K) analysis, CKM (K+) in
preparation
BNL: E949 (K+) analysis, KOPIO (KL) in preparation
KEK: E246 (K+) analysis, E391a (KL) ready to run
Frascati: KLOE (KL,S, K) running, upgrades?
Protvino: OKA (K) in preparation
Novosibirsk: VEPP-2000 machine (KL,S, K) in preparation
J-PARC: Neutral K beam line foreseen
Alive and kicking!
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Conclusions?
Once upon a time, kaons delivered many surprises
and precious insight…
CPV
… they are still doing so today,
and they will in the near future!
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
Spare slides
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KL  ee
KTeV: KL
A = (13.3  1.7)%
BR = (3.63  0.18)  10-7
Large CP-violating asymmetry seen
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KS  ee
NA48: KS
A = (-1.1  4.1)%
First measurement
BR = (4.69  0.30)  10-5
No asymmetry for KS
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KTeV limits on KL  0
BR(KL  0) < 5.9 10-7 (90% CL)
Using 0  e+e- decay
(0.12 events bkg.)
BR(KL  0) < 1.6 10-6 (90% CL)
Using 0   decay
(3.7 events bkg.)
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris
KTeV: ’/ improvements
Several improvements in
the analysis to reduce
systematic errors:
DCH simulation,
alignment, reconstruction
Use of angles and
improvements for
overlapping showers in
CsI reconstruction
Stat. Error  110-4
June 5th, 2003
M. Sozzi - Kaon physics
FPCP 2003, Paris