KLOE - May 20, 2008 1
Experimental setup Data taking Vus CPT ahad f 0
The KLOE experiment at the Frascati -factory
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 2
The KLOE detectorMulti-purpose detector optimized for
Klong physicsKL ~51 ps c|DAFNE ~340 cm
Huge, transparent Drift Chamber in 5.2 kGauss field of a SC coil. Carbon fiber walls, 55000 stereo wires, 2m radius, 4m long, mostly He gas mixture. Momentum resolution:(pT)/pT~0.4%
Lead-Scintillating Fiber Calorimeter with excellent timing performance.24 barrel modules, 4m long + C-shaped End-Caps for covering 98% of the solid angle. Time resolution:T = 54 ps/ E(GeV) 50 ps. Energy resolution: E/E = 5.7% / E(GeV)
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 3
•2001-2005 Lint = 2482 pb-1
•2004-2005 Lint = 1990 pb-1
•Best conditions: Sept/Oct/Nov 2005 179/189/194 pb-1
stable luminosity, beam energy and backgrounds
Five years of continuous efforts to increase circulating currents maintaining low bck level at the IR and providing stable running conditions for the experiments
Continuous Beam Re-filling to obtain integrated luminosities > 150 pb-1 per month
KLOE Data Taking
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 4
min {(pmiss-Emiss)|, (pmiss-Emiss)|
e
Data
• KL e: KL vertex reconstructed in DC Fit to pmiss - Emiss spectrum
• KL Photon vertex reconstructed by
TOF• Absolute BR: (Nsig/Ntag) 1/siggeo function of L
• Using the constraint BR(KL)=1,BR(K Le) = 0.4007 0.0006stat 0.0014syst
BR(K L ) = 0.2698 0.0006stat 0.0014syst
BR(K L 000) = 0.1997 0.0005stat 0.0019syst
BR(K L +-0) = 0.1263 0.0005stat 0.0011syst
KL = (50.72 0.17stat 0.33syst ) ns
Result from direct KLOE measurement, L= (50.92 0.17stat 0.25syst ) nsAverage: L = 50.84 0.23 ns / ~ 4.510-
3
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Dominant KL’s BR and L
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 5
Semileptonic K± BR’sSemileptonic decays tagged by 2-body decays, K0 and K
Four different samples analyzed, tagged by K++0, K--0, K++ , K--
Lepton mass from p and TOF: M2lept
= p2lept [ c2/L2
lept (Tlept- T + L/c)2 – 1 ]
Consistent results, giving
BR(K±e3) = 0.0497 ± 0.0005
BR(K±3) = 0.0323 ± 0.0004
Event counting from the fit of the M2lept distribution with the MC-predicted
spectra for K±e3, K±
3 and background.
The measurements are fully inclusive ofradiative decays, whose acceptance is known from MC simulation [ C. Gatti, Eur. Phys. J., C 45 (2006) 417]
BR \ Tag K+2 K+
2 K-2 K-
2
BR(Ke3) 0.0495(7)
0.0493(10)
0.0497(8)
0.0502(10)
BR(K3) 0.0322(6)
0.0322(9) 0.0323(5)
0.0327(9)
JHEP 0802 (2008) 098
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 6
K± Lifetime
Four independent measurements of the K± lifetime, exploiting both, -the accurate vertex reconstruction (tracking) and -the excellent time resolution of the calorimeter (TOF)
All of the decay channels tagged by K± decays have been used for the Kaon vertex reconstruction, while the X0 channels have been selected for the TOF measurement.
(K±) = 12.347 ± 0.030
Efficiencies are evaluated with data control samples.From vertex measurement we obtain (K±) = 12.364 ± 0.031stat ± 0.031syst and from TOF (K±) = 12.337 ± 0.030stat ± 0.020syst Normalized correlation, from common events (systematics are pratically uncorrelated ) is 30.7%. Averaging the results, we obtain:
K-, l
K+, l
K-, t
K+, t
JHEP 0801 (2008) 073
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 7
Semileptonic form factorsForm Factor dependence from momentum transfer used in the evaluation of phase space integral
Phys.Lett.B636(2006)166
KLe
t/m2
from KL New parametrization used. Series expansion in terms of one parameter only for both, f+ and f0Combined e and results:
I(K0e3) I(K0
3) I(K±e3) I(K±
3)0.15477(35)
0.10262(47)
0.15913(36)
0.10559(48)
JHEP 0712 (2007) 105
KL
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 8
BR(e) = (7.046±0.077±0.049 )10
fractional error: 1.3% = 1.1%stat 0.7%syst
AS = (1.5 ± 9.6 ± 2.9 ) 10
first measurement
Charge asymmetry
Branching ratio
1 + 4 Re(x+) = SL
BR(KS e) L
BR(KL e) S=
6 10 3
103 4 10 3
13 103
Re x = ( 0.5 3.1 1.8) 10
Pure KS beam, tagged by KL interactions in the calorimeter. TOF e/ ID, fit to Emiss- pmiss spectrum
KS events in the same sample for KS counting
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Kse: BR, As, Re x+
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 9
(K l)C2K(G2
FM5K/192 ) f2
+(0)|Vus|2 I(t) SEW(1 + EM + SU(2) )
f+(0)|Vus| from Kl3 decays
Electromagnetic and Isospin corrections + phase space integrals to obtainindependent measurements of f+(0)|Vus| The consistency of the measurements validates isospin corrections
< f+(0)|Vus| > = 0.2157 ± 0.0006
< f2+(0)|Vus|2 >|
e < f2+(0)|Vus|2 >|
competitive with that obtained from leptonicdecays g2
e/g2 = 1.000 ± 0.008
is a test of lepton universality
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 10
Radiative corrections largely cancel out in the ratiofK /f ratio: better precision from Lattice, scale-
uncertainties reduced Using fK /f =1.189(7) (HPQCD/UKQCD Coll.,
arXiv:0706.1726))and KLOE BR(K+ +) :
|Vus/Vud|2 = 0.0541 0.0007
Tag from K-Subtract lbackground from dataEvent count in the {225, 400} MeV window of the momentum distribution in the K rest frame
BR(K+ = 0.6366 0.0009stat 0.0015syst
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BR(K++())
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 11
Unitarity test of the CKM matrix
JHEP 0804(2008)059
From KLOE average < f+(0)|Vus| > and using the recent Lattice result f+(0)=0.9644±0.0049 [ RBC/UKQCD Coll., arXiv:0710.5136],
V2us= 0.05004±0.00058
KLOE has also obtained, in agreement with Lattice results, f+(0)=0.964±0.023 from the measurement of the semileptonic form factor parameters, using Callan-Treiman relation and fk/f = 1.189±0.007
From superallowed nuclear -decay, V2
ud= 0.94903±0.00051
The fit including KLOE V2us/V2
ud determination from K++decays provide the CKM unitarity test:
1 -|Vus|2 - |Vud|2 = 0.0004 ± 0.0007
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 12
Bounds on New Physics from K decayInteresting limits in tan-MH± plane have been obtained from K decayH± exchange can compete with the W± exchangefor the helicity-suppressed mode K [G.Isidori and P.Paradisi,Phys.Lett.,B639(2006),499]The observable used is
that is unity in the SM and would be lower by the interference between W± and H± amplitudes
Rl23 = 1 - m2K+ m2
+
m2H+ m2
K+
tan20tan1 -( )
Rl23 =Vus(K2) Vud(0+0
+)Vus(Kl3) Vud(2)
From KLOE measurements, lattice calculations and Vud results reported in the previous slides,we obtain
and the limits that in the figure are compared with those from B decay
Rl23 = 1.008 ± 0.008
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 13
NEW: Re (159.6 ± 1.3) 10-5 Im (0.4 ± 2.1) 10-5
OLD: Re (164.9 ±2.5) 10-5 Im 2.4 ±5.0) 10-5
- Uncertainty on Im is now dominated by
and
- Semileptonic sector contributes by ~ 10%
Assuming no CPT violation in the decay amplitudes, ( = 0): |M| < 310-19 GeV
1. KLOE: new BR(KL
2. KLOE: A, x, S=Q from KSe
3. KLOE: new limit on KS3
4. No results already constrained byBSR have been used
2-3 improvement
CPT test from Bell-Steinberger relation
From Im and Re get limits on M= (mK0 - mK0) and = (K0 - K0)
JHEP 0612 (2006) 011
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 14
tmeeetI ttt LSSL cos12 ;, 2/
interference term modified introducing a decoherence parameter .
038.0035.0018.0
LS KK
520.018.0 1010.000
KK
Systematics x10 better, completely negligibleKSKL
< 0.085 K0K0 < 0.44 10-5 @ 90% C.L.
CPT violation could also change initial state
|| < 2.1 10-3 @ 95% C.L.
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Decoherence and CPT from neutral Kaon pairs
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 15
PLB 606(2005)12
2
The anomalous muon magnetic momenta = (g - 2)/2 = (116592080 ± 60) 10-11 E821Theory : a = a
QED + aweak
+ ahad
ahad from measurements of the ha-
dronic cross section via dispersion relation
Dominant low-energy contribution, M2< 1 GeV2
KLOE measurement from e+e- final state with at low zenithal angleWe obtained a
in the 0.35<s< 0.95 GeV2 region.Two independent data sets have been analyzed with different trigger conditions and different analysis paths, giving
Hadronic cross section
a|0.35<s<0.95 = (3844± 8stat± 35syst± 35theo) 10-11 [140 pb-1 data sample]
a|0.35<s<0.95 = (3892± 6stat± 30syst± 20theo) 10-11 [242 pb-1 data sample]
(preliminary)
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 16
Low-energy hadronic contribution to a
Consistent set of avalues from all of
the low-energy hadronic cross section measurements at e+ e- machines
The theoretical SM prediction for aincluding the e+ e- data set differs bymore than 3from the BNL measurement
New KLOE analysis confirms the discrepancyK. Hagiwara, A.D. Martin, Daisuke Nomura, T. Teubner
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 17
Search for the f0 signal as a deviation on M from the ISR + FSR shape
f0(980) region
M (MeV)
S
e+e
Two main contributionsto the final state,separated in thebi-dimensional plot Mvs M
Eve
nts/
1.2
MeV
e+e events with the photon at large angle (45<<135)Main contributions: ISR (radiative return to ) and FSR
e+e
The light scalars : f0 (980)
Experimental setup Data taking Vus CPT ahad f 0
KLOE - May 20, 2008 18
SgKK
gSKK
gS
K
K
SV gVS
gS
e+
e-
Kaon-loop
Predictions of the M distribution from Kaon-loop and direct scalar coupling to vector mesons, have been compared for both final states, , and
PLB 634 (2006) 148
EPJ C49 (2007) 473
Experimental distributions have been fitted taking into account the contributions to the final states summarized in the previous slide
Data can be described by both the models
To fit the spectrum with predictions from Kaon-loop model, a (600) contribution must be included
KK coupling, in the model with direct scalar coupling to vector mesons, results weaker from analysis than in the study.
The f0(980) structure