Transcript kaon rev - INFN

Latest results on kaon physics
In spite of a long history the K system is still a laboratory for interesting
physics: flavour physics, CP violation. It can be a sensitive probe for NP.
Most of the recent results come from KLOE, KTEV, NA48
Vus
KS rare and “semi” rare decays
CP violation in charged kaon
pp scattering length
Future programs
Outlook & Conclusions
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Unitarity test of CKM: Vus Saga
Unitarity (or lack thereof) of CKM matrix tests existence of further quark
generations and possible new physics (eg. Supersymmetry)
Most precise test of unitarity possible at present comes from 1st row:
|Vud|2 + |Vus|2 + |Vub|2 = 1
2|Vud|dVud = 0.0010
PDG
2|Vus|dVus = 0.0011
Vud2 = 0.9482±0.0010 (nuclear decays)
Vus2 =
0.0484±0.0011 ( from e.g.
K+p0e+n
e
)
2004
Vub2 = 0.000011±0.000003 ( B meson decays)
|Vud|2 + |Vus|2 + |Vub|2 = 0 9972±0.0015
Latest results on kaon physics
(~ 2 s deviation)
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Vus from Kl3 decays
|Vus| is extracted from Kl3 partial decay widths
where i runs over the four modes K±,0(e3), K±,0(m3)
• Ni =
G2m M5Ki
192p3
C2i
few 10-2
[Ci=1(2-½) for neutral (charged kaon decays)]
• f+K0p-(0) form factor at zero momentum transfer: pure theory calculation (PT, lattice)
•



I(l , l0 ,0) phase space integral, Sew short distance corrections (1.0232)
di SU(2) ,de2p2 form factor correction due to isospin breaking (strong and electromagnetic)
DIi (l,l0) ) phase space electromagnetic correction
l,l0 slopes (momentum dependence of the vector and scalar form factors)
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Unitarity test of CKM: Vus Saga
2003: First hint: BNL E865
Br(K+→π0e+ν) =(5.13±0.02stat±0.10sys)%
PDG(<2004): (4.87±0.06)%
Vus consistent with unitarity but 2.7σ above existing Br(K ± →π0e±ν) value.
 Key issue is systematic control of the Branching Ratio.
Detector not optimized for photons (designed for π+μ-e+)
Require: π0 e+e-γ in signal and normalization (
K+→p+π0)
2004: KLOE KTEV, NA48 experiments measure Kl3 branching ratio for
Ks and KL , lifetime and form factors with different techniques
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KLOE:Tagging of neutral kaons
KL “crash”
= 0.22 (TOF)
KS  ppKS  p-en
KL  2p0
KL tagged by KSp+pEfficiency ~ 70%
KL momentum resolution ~ 1 MeV
Latest results on kaon physics
KS tagged by KL interaction in EmC
Efficiency ~ 30%
KS momentum resolution ~ 1 MeV
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KLOE:Measurement of KL BR’s
Tagging

Precisely measure absolute branching ratios
Ni
1
BR(KL  i) 

N tag  (i) rec   FV ( L )   tag (i) /  tag (all)
Tagging efficiency
Reconstruction efficiencies:
KL pmn, pen
 (rec)  55%
KL  pp-p0
 (rec)  40%
KL  3p0
 (rec)  100%
Integral over the fiducial volume:
ε (FV, L)  26%, depends on L
Trigger required on the KS side
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KLOE:KL
0
3p
KS  pp-
At least 3 neutral clusters
Neutral vertex reconstructed along KL direction using Tof
Efficiency close to 100%, bkg 1%
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KLOE:KLcharged
KS  pp-
2 tracks forming a vertex along the
KL direction.
Vertex and tracking efficiency
55% for Kl3 and 40% for 3p
Latest results on kaon physics
P-E(pm) (MeV)
Events counted by fitting missing
momentum minus missing energy
in the pion-muon hypothesis
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KLOE: KLcharged
Pmiss - Emiss distribution very sensitive to radiation and momentum resolution
Check data/MC agreement via independent PID
Radiative corrections properly included in the Monte Carlo generators (IR-finite
treatment of radiative effects (no energy cutoff))
KL pen control sample
Latest results on kaon physics
KL pmn control sample
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KLOE: Absolute BR's results
• Absolute BR results with (KL= 51.54  0.44 ns):
¾ of 2001-2002 data has been used for efficiency evaluation and
¼ for BR measurement corresponding to 13106 tagged KL.
BR(KL pen() ) = 0.4049  0.0010  0.0031
~8105 events
BR(KL pmn() ) = 0.2726  0.0008  0.0022
~ 5105 events
BR(KL 3p0) = 0.2018  0.0004  0.0026
~ 7105 events
BR(KL pp-p0() ) = 0.1276  0.0006  0.0016
~ 2105 events
Latest results on kaon physics
330 pb-1
2001-2002
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KLOE: BR results
BR(pen + pmn + pp-p0 +3p0 + rare decays from PDG) = 1.0104  0.0076
KL FV acceptance depends on the lifetime :
Assuming S BR(KL X) =1
independent measurement of KL
KL= 50.72  0.14  0.36 ns
BR(KL pen() ) = 0.4007  0.0006  0.0014
BR(KL pmn() ) = 0.2698  0.0006  0.0014
BR(KL 3p0) = 0.1997  0.0005  0.0019
BR(KL pp-p0() ) = 0.1263  0.0005  0.0011
Latest results on kaon physics
Systematics evaluated
including
full error matrix from all
sources.
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
• Large acceptance for KL decays
0.4 l  high statistical accuracy
•KL momentum measured from
KSp+p• KL3p0 efficiency >99% little
variation along the KL path
•KLp+p-p0 as a control sample for
the estimate of efficiency, resolution
and time scale
Events/0.3 ns
KLOE: KL lifetime from KL3p0
+ data
6 -26 ns
(40% L)
t*= LK/c (ns)
 (PDG) (fit) = (51.7 ± 0.4) ns
 (Vosburg, 1972) = (.4 ± 0.44) ns - 0.4 Mevents
L (KLOE) = (50.87 ± 0.16 ± 0.26 ) ns - 14.5 Mevents – 440 pb-1
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
NA48 & KTeV Measurements
NA48
Both experiments measures ratio of BR
(sample sizes 105-106)
(~6 million reconstructed Ke3)
BR(KL
pen)
BR(2 track)
= 0.4978  0.0035
Using PDG-KTeV average
for BR(KL  3p0)
KTeV
KTeV measure 5 KL ratios
Ge3 / Gm3 , G+-0/ Ge3 , G000/ Ge3
G+- / Ge3 , G00 / G000
BR(KL pen) = 0.401 
These 6 decay modes account for
0.0045
99.93% of KL decays and the ratio
They also have a preliminary measurement
can be combined to extract BR
0
of BR(KL  3p ) = 0.19660.0035
BR(K  pen )=0.05140.0006
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
BR comparison
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Vus from Kl3 decays and L
hep-ph/0411097 (F. Mescia @ICHEP04)
1) Quadratic parametrization of the form factor momentum dependence:

t
l t 2 
f (t )  f (0) 1  l 2 
2 
mp  2 mp  

l  0.0226  0.04
l  0.0023  0.0004
l0  0.04  0.0008
from KTeV
+ ISTRA
2) KL lifetime from KLOE (average of the two measurements) :
KL= (50.81  0.23) ns
3) BRs from KLOE
(setting the sum =1):
4) Form factor
BR(KL pen) = 0.4007  0.0006  0.0014
BR(KL pmn) = 0.2698  0.0006  0.0014
f+Kp(0) from Leutwyler-Roos: 0.961(8)
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Vus from Kl3 decays and L
|Vus|f+Kπ(0)
KLOE results:
|Vus|f+Kp(0) (KSe3) = 0.2169 0.0017
|Vus|f+Kp(0) (KLe3) = 0.2164 0.0007
|Vus|f+Kp(0)(KLm3) = 0.2174 0.0009
From Unitarity:
(1-|Vud|2)1/2f+Kp(0) = 0.2177 0.0028
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KLOE:
+
+
BR(K m n())
Combining the experimental value of
Particle momentum in K rest frame
G(Kmn())/G(pmn())
with the ratio
fK/fp obtained from lattice calculations
we can extract the ratio |Vus|/|Vud|
(Marciano hep-ph/0406324)
pp
pen pmn
mn
Selection
• Tag from K-m-n
• 2002 data 175 pb-1 (2/3 is used as
efficiency sample)
• Background events identified by
the presence of a neutral pion.
P(p)*(MeV)
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KLOE: BR(K+m+n())
• Event counting performed by
fitting the P* distribution with
signal and background shapes
obtained from data control
samples: bkg-sample selected
by looking for 2 photons from
neutral pion; control sample
for signal shape selected by
identifying the muon cluster in
the Emc.
•Systematics are dominated by
efficiency estimate.
mn
pp
P(p)*(MeV)
BR(K+  m+n()) = 0.6366 ± 0.0009 (stat.) ± 0.0012 (syst.)
Chiang = 0.6324  0.0044
Latest results on kaon physics
PDG fit = 0.6343  0.007
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Vus from K+m+n()
Following the method from Marciano hep-ph/0406324 :
• fK /fp =1.210±0.014
(MILC Coll. hep-lat/0407028)
• Vud=0.9740±0.0005
(superallowed -decays)
Vus=0.2223±0.0025
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KS p0p0p0 – test of CP and CPT
Observation of KS  3p0 signals CP violation in mixing and/or in decay:
SM prediction: GS000 = GL000|+000|2
Best limit from: direct search SND ’99 :
interference NA48 ’05:
BR(KS  3p0) = 1.9 x 10-9
BR(KS  3p0) < 1.4 x 10-5
BR(KS  3p0) < 7.4 x 10-7
Uncertainty on KS  3p0 amplitude limits precision of CPT test:
from unitarity
(1 + i tanfSW)Re  - Sf A*(KSf) A(KLf)/GS = (-i + tanfSW) Im d
(S,L =   d)
A limit on BR(KS  3p0) at 10-7 level translates into a 2.5-fold improvement on
the accuracy of Im d, i.e.
_
_
d(MK0 - MK0)
d(MK0 - MK0)
-8
 2 10 
MK
MK
Latest results on kaon physics
 8 10-9
(MK/MPlanck = 4 10-20)
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KLOE: Search for KS p0p0p0
22p
Signal selection
•KS’s tagged by of Kcrash
Data
MC 3p0 BR 10-5
80
•6 photons clusters, no tracks from IP 60
•Kinematic fit to improve cluster
parameter
Background rejection
40
KS p0p0 + 2 fake ’s
•Signal box in 23p, 22p plane
20
2
3p
0
- pairing of 6 clusters with better
p0
10
20
mass estimates
30
23p
40
22p - pairing of 4’s out of 6: p0 masses, E(KS), P(KS), c.m. angle
between p0’s
•Final cut on residual Ks energy: E(Ks )- SEp
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KS p0p0p0 – Final Results
KLOE: 450 pb-1 ’01+’02 data
Nsel(data) = 2 events selected as signal
3p = 24.5%
Nsel(bkg) = 3.130.82stat0.37sys
bkg events expected from MC
Can state: N3p < 3.45 with a 90% CL
Normalize signal counts to KS  p0p0 count in the same data set:
BR(KS  p0p0p0) =
N3p / 3p
N2p / 2p
Latest results on kaon physics
BR(KS  p0p0) < 1.2 10-7,
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KLOE: KS p0p0p0 – Final Results
Using PDG value and our limit we obtain:
NA48
|h000| =
A(KS  p0p0p0)
A(KL  p0p0p0)
< 1.8 10-2
@ 90% CL
2 fb-1 Prospect
KLOE
•Increased statistics: x 6.5 improvement
•Increased background rejection
UL will decrease by ~ 10
Latest results on kaon physics
Accepted for publication
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KS pen decays – Physics issues
Sensitivity to CPT violating effects through charge asymmetry:
_
+
+
G(KS,L  p e n) - G(KS,L  p e n)
AS,L =
_
+
+
G(KS,L  p e n)  G(KS,L  p e n)
If CPT holds, AS=AL
ASAL signals CPT violation in mixing and/or decay with DSDQ
_
Sensitivity to CP violation in K0-K0 mixing:
AS = 2Re  (CPT symmetry assumed)
AS never measured before
Test of the DS = DQ rule, G(KS  pen)/G(KL  pen) = 1 + 4 Re(x)
Can extract |Vus| via measurement of BR(KS  pen)
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KS pen decays: Results
•
Kinematic closure: use KL to
obtain KS momentum PK and test
for presence of neutrino:
Emiss =
MK2
+
PK2
 Data
— MC sig + bkg
– Ep – Ee
Pmiss = |PK – Pp – Pe |
• Further rejection of KS  pp
background from TOF identification
• Obtain number of signal events from a
constrained likelihood fit to multiple data
distributions
• Normalize to KS  pp in the same data
set
Emiss-cPmiss(MeV)
Use BR(KS  pp) to calculate BR(KS  pen)
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KS pen decays: Results
BR(KS  p-e+n) = (3.54  0.06stat  0.04syst) 10-4
BR(KS  pe-n) = (3.55  0.05stat  0.02syst) 10-4
BR(KS  pen) = (7.09  0.08stat  0.05syst) 10-4
Published result: (6.91  0.34stat  0.15syst) 10-4, KLOE ’02
Dependence of efficiencies on charge mainly due to TOF
effects, estimated using data control sample of KL  pen
AS = (-2  9stat  5syst) 10-3
AL = (3.322  0.058  0.047) 10-3 [KTeV 2002]
AL = (3.317  0.070  0.072) 10-3 [NA48 2003]
Uncertainty in charge asymmetry still dominated by statistics
With data for an integrated luminosity of 2.5 fb-, dAS  3 10-3  2 Re()
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KS pen decays: Results
Compare G(KS  pen) with G(KL  pen): test of the DS  DQ rule
Use average of KTeV and NA48 measurement of the KS lifetime: S = (89.62  0.05) ps
Use new measurement of the KL lifetime: L = (50.89  0.23) ns KLOE ’05
4Re(x) = G(KS  pen)/G(KL  pen) - 1
Re(x) = (-2.7  3.0stat  1.8syst) 10-3
KTeV04
Use BR(KL  pen)  (40.67 ± 0.)% [KTeV04]
Re(x) = (0.1  3.2stat  1.8syst) 10-3
Use BR(KL  pen)  (40.07 ± 0.7)% [KLOE05]
Most precise measurement of Re(x) (in
CPT conserving transitions): compare
with CPLEAR99, dRe(x) = 6 x 10-3
Latest results on kaon physics
KLOE05
KLOE KS
PDG04
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005

Direct CP-violation in K3p
Charged kaon: direct CP violation only
BR(K±p±p+p-)=5.57%; BR(K±p±p0p0)=1.73%.
• Kinematics
u=
(s3-s0)/mp2
• Matrix element
=2mK∙(mK/3-Eodd)/mp2;
v = (s2-s1)/mp2= 2mK∙(E1-E2)/mp2
parameterized in terms of slopes
|M(u,v)|2 ~ 1 + gu + hu2 + kv2
si = (PK-Ppi)2, i=1,2,3 (3=odd p);
s0 = (s1+s2+s3)/3.
• Measured quantity sensitive to direct CP violation:
Ag = (g+-g-)/(g++g)≠0
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Theoretical expectations
Experimental precisions by 2005:
[dAg~10-3]
Ford et al. (1970)
|Ag|
10-2
10-3
10-4
HyperCP prelim. (2000)
TNF prelim. (2002)
“neutral” mode
NA48/2
proposal
• Models beyond SM predict
substantial enhancement
partially within the reach
of NA48/2
“neutral”
“charged”
10-5
10-6
Theory
• SM estimates vary within
an order of magnitude
(few 10-6… 8×10-5)
• Asymmetry in decay
widths expected to be
smaller than in Dalitz
slopes
New
(SM: ~10-7… 10-6)
SM SUSY physics
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
NA48/2 goals and method
M.S. Sozzi
• Primary NA48/2 goals:
– Measure slope asymmetries in “charged” and “neutral”
modes with accuracies δAg<2.2∙10-4, and δAg0<3.5∙10-4,
respectively. Requires >2∙109 decays in “charged” mode
and >108 in “neutral” mode.
• NA48/2 method:
– Two simultaneous K+ and K– beams, superimposed in
space, with narrow momentum spectra;
– Detect asymmetry exclusively considering slopes of ratios
of normalized U distributions. If acceptance is equal for K+
and K–,
R(u) = N+(u)/N–(u) ≈
≈ n∙(1+g+u)/(1+g–u) ≈
≈ n∙(1+2Dgu)
Δg = 2g∙Ag
– Equalize K+ and K– acceptances by frequently alternating
polarities of relevant magnets.
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
NA48/2:Selected statistics 2003
sM=1.7
M.S. Sozzi
|V|
Events
Data-taking 2003:
1.61x109 events selected
MeV/c2
pmn
K+ : 1.03x109 events
M(3p)
GeV/c2
U
Ag = (0.5±2.4stat.±2.1stat.(trig.)±2.1syst.)x10-4 =
(0.5±3.8)x10-4
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Cusp-like effect in K+p+p0p0
Two diagram contribute: direct emission, pp re-scattering
M0 = 1+gu/2
M1  (a0 -a2)
dG/dmpp  |M0 + M1|2
Interference generate a cusp in the pp spectrum next to pp- threshold, not seen earlier
by lower precision experiments
One loop calculation: cusp located at mpp = 2mp+ N. Cabibbo hep-ph/0405001
Recent two loops calculation: dG/(dmpp)2  F (a0 -a2 , a2 , g, h, mpp) allows to extract
scattering lengths a0 -a2 from mpp spectrum N. Cabibbo ,G. Isidori hepph/0502130
To be compared to precise (2%) PT prediction
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK
Conversano June 2005
Cusp-like effect in K+p+p0p0
NA48/2 2x108 K+p+p0p0
4x109 K+p+p –p +
2003-2004
50 days-2003
m2pp
Best fit obtained with 2 loops and a small
contribution from pionium fixed to:
BR(Kp pionium)/ BR(K3p) 0.8 10-5
(a0 -a2)·mp = 0.281 ± 0.007 (stat.) ±0.014 (syst.) ± 0.014 (theor.) NA48/2 p
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Rare Kaon Decays and the SM
Rare Kaon decays mediated by Flavor Changing Neutral Currents are the
main experimental tool to probe the flavour structure of physics beyond the
SM independent from B mesons.
• No SM tree-level contribution
• Strong suppression within the SM because
of CKM hierarchy
• Predicted with high precision within the SM
G. Isidori
if dominated by short-distance dynamics
(holy grail)
Im lt =ImVt*s Vtd =h A 2 l 5
Standard Model (Buras ):
|Vtd|
B(K L0
 p 0nn )  1.8 x 10-10  Im 5lt X ( xt ) 
 l
2

4.1 x10 -10 A4h 2  3.0  0.6 x 10-11
B(K   p nn )
Latest results on kaon physics
2
1.0 x 10-10 A4 h 2  ( 0 -  )   7.8  1.2 x 10-11


A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Status & Future programs
•K0L  p0nn
–Upper limit is 4 order of magnitude from the SM prediction,
KTEV@FNAL
–Expect results from data collected by E391a@KEK (proposed SES~3 1010)
–Next experiment KOPIO@ BNL (>100 signal events), JPARC (180 signal
events)
•K+ pnn
–3 clean events are published (in agreement with SM)
–Next experiment: NA48/3@CERN (O(100 ) signal events), JPARC (> 50
signal events)
–Move from stopped to in flight experiments (increased acceptance)
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Outlook & Conclusions
• In spite of a long history the K system is still a laboratory for interesting
physics: flavour physics, CP violation etc..
• “Unitarity Crisis” in first row of CKM matrix seems resolved.
• In the next year we will have new results on KL and KS K decays from
KLOE ( 2fb-1 will be collected by the end of 2005) and NA48.
• Many experiment proposed (not yet approoved) on rare kaon decays will
probe the flavour structure of physics beyond the SM
Is kaon physics still interesting???
Answer is YES!!!
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
KS semileptonic decay
•Selected using Tof technique
•Event counting obtained by
fitting the E(pe)-P distribution
•The two charge modes are
measured independently
• selected ~104 signal events per
charge in the 2001-2002 data
sample.
 Data
— MC sig +
bkg
Emiss–Pmiss(MeV)
0-60 -40 -20
0
20
40
60
BR(KS  pen) = (7.09  0.07stat  0.08syst) 10-4
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
80
DAFNE
W = mf
(1019.4 MeV)
Ldesign
51032 cm-2 s-1
2002:
270 pb-1
2001:
170 pb-1
2000:
20 pb-1
2004 best Lpeak 1.2×1032 cm-2s-1
2004 avg L ~6×1031cm-2s-1
Collected 770 pb-1 since May 2004
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Conclusion
With the data collected in the year 2001-2002 KLOE has measured:
•The dominant KL BR’s with 0.5% accuracy
• The KL lifetime with 0.6% accuracy
• BR(KS pen) with 1% accuracy
• BR(K+ m+n) with 0.2% accuracy
• All BR’s are inclusive of the radiation
Final papers are under review by the Collaboration
A large number of K semileptonic decays has been collected and identified
will allow us to measure all the BR’s with better than 1% accuracy
KLOE is now measuring:
• K± lifetime
• Kl3 form factor
• KSpmn BR
Coming soon the update of G(KSp+p-())/G(KSp0p0) measurement
We expect to collect 2fb-1 for the end of December 2005
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Unitarity test of CKM: Vus Saga
exp
th
d Vus 1  d BR  1  d  1  dl  1  dl0  df  (0)
 
  
 
     
Vus
2  BR  2    20  l  30  l0  f  (0)
K0 pen
K pen
0.3 %  0.4%  0.3%
0.8%
0.6%  0.1%  0.3%
0.8%
K0
pmn
K
0.5%  0.4%  0.8%  0.6%  0.8%
0.9%  0.1%  1.5%  0.2%
 0.8%
pmn
EXP: Need to measure BR, lifetime, and slopes with good accuracy
TH : Need to improve estimate on f(0)
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
The KLOE detector
Calorimeter
s(E)/E = 5.7%/E(GeV)
s(t) = 54 ps/E(GeV)  100 ps
Latest results on kaon physics
sp/p  0.4 % (tracks with q > 45°)
sxhit  150 mm (xy), 2 mm (z)
sxvertex ~ 1 mm
s(Mpp) ~ 1 MeV
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Radiative corrections
P-E(pe) (MeV)
P-E(pm) (MeV)
IR-finite treatment of radiative effects in MC (no energy cutoff)
The E-P shape is checked using Ke3/Km3 enriched samples obtained from an
independent calorimetric selection: Tof, E/p, and cluster centroid position.
The Ke3 BR changes by 2% neglecting the radiative tail.
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Semileptonic decays of
±
K
Absolute BR measurement.
K±mn,pp decays used to tag the events.
Kl3 selection:
 kaon decay vertex in FV
 Reject two-body decays: P*(p)  195 MeV
 Cut on missing momentum to reject
pppmn decays.
 p0 search: 2 neutral clusters in EmC,
prompt wrt the K vertex.
 Spectrum of charged daughter mass, m2,
from TOF measurement.
mK
K
e

m2=p2 [(cT/L)2-1]
 Ratio of data and MC efficiency is used to
correct MC acceptance.
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Semileptonic decays of
ml2=pTRK2 [(c(tl-t)/LTRK )2-1]
±
K
K+p+p0 Tag
Tag K+m2
Tag K+p2
Tag K-m2
Tag K-p2
NKe3
67 022  331
26 774  215
71 188  345
25 942  211
NKm3
42 096  282
16 586  179
44 925  293
16 465  180
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Tagging of charged kaons
• Tag performed selecting K± m±n,
p±p0 decays (85% of K±) by
measuring the charged particle
momentum in the K rest frame (P*).
• In the following analyses the
trigger is required on the tag side.
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Generators for radiative K decays
Motivation: acceptance evaluation with accuracy
better than 1%, shape of kinematic variables (e.g.
Emiss-pmiss spectrum)
New MC generators for pp and Kl3 decays
including radiated photon, without any cutoff on
the energy. The fraction of events in the tail is in
agreement with present experimental knowledge:
BR( K L  pen , E  30 MeV q e  20)
BR( K L  pen )
kTeV
(0.908 0.015) 10- 2
Bijnenset al
0.9310- 2
MC
0.9310- 2
BR( K S  pp , E  50 MeV )
BR( K S  pp )
Latest results on kaon physics
 b -1
dG
2
E
 Ao    b   
dE
M 
pp

-3
E731 (2.560.09)10
-3
 (2.59  0.07) 10
MC
2.6 10-3
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Vus from Kl3 decays and L
|Vus|f+Kπ(0)
New Vud
KLOE results:
|Vus|f+Kp(0) (KSe3) = 0.2169 0.0017
|Vus|f+Kp(0) (KLe3) = 0.2164 0.0007
|Vus|f+Kp(0)(KLm3) = 0.2174 0.0009
From Unitarity:
(1-|Vud|2)1/2f+Kp(0) = 0.2181  0.0022 New Vud
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Vus from Kl3 decays and L
1-|Vud|2)1/2f+Kp(0) = 0.2181  0.0022
new vud=0.9739(3) old vud 0.9740(5)
new vus 0.2269(13) old vus 0.2265(22)
Latest results on kaon physics
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Kaons at KLOE
• The  decays at rest allow us to
select monochromatic
(p ~ 110 MeV/c) pure beams of Kaons
• Observation of KL,S signals
presence of KS,L
• KS decays near IP: lS ~ 0.6 cm
• ~50% of KL decays inside the
detector: lL ~ 340 cm
• l± ~ 95 cm
• Events per pb-1:
K+K- 1.5 106/pb-1
KLKS
106/pb-1
Latest results on kaon physics
~4 m
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005
Kaon Rare Decays and the SM
(holy grail)
Vtd
Kaons provide
quantitative tests
of SM independent
from B mesons…
…and a large window
of opportunity
exists!
Im lt = A2 l5 h
Re lt = A2 l5 
Latest results on kaon physics
G. Isidori
A.Antonelli LNF-INFN - QCD@WORK Conversano June 2005