ckm unitarity problem: results from na48 experiment
DESCRIPTION
CKM unitarity problem: results from NA48 experiment. Evgueni Goudzovski (JINR) JINR Scientific Council January 20, 2005. The CKM matrix. The Cabibbo-Kobayashi-Maskawa matrix connects the eigenstates d’,s’,b’ of weak interaction with the quark flavour eigenstates d,s,b :. =. - PowerPoint PPT PresentationTRANSCRIPT
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CKM unitarity problem:CKM unitarity problem:results from NA48 results from NA48
experimentexperiment
Evgueni Goudzovski (JINR)Evgueni Goudzovski (JINR)
JINR Scientific CouncilJINR Scientific CouncilJanuary 20, 2005January 20, 2005
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The CKM matrix The Cabibbo-Kobayashi-Maskawa matrix connects
the eigenstates d’,s’,b’ of weak interaction with the quark flavour eigenstates d,s,b:
Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
d
s
b
d’
s’
b’
=
Conservation of probability: CKM matrix has to be unitary: VCKMVCKM
+=I
If unitary not fulfilled: New Physics (e.g. 4th quark generation)
E. Goudzovski JINR SC January 20, 2005
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CKM unitarity problem CKM unitarity requires for the 1st row:
|Vud|2 +|Vus|2+ |Vub|2 = 1
Particle Data Group (PDG)(PDG) 2004 review: |Vub|=(3.67 ± 0.47)∙10-3
[negligible contribution into unitarity relation, ~10-5] |Vud|=0.9738 ± 0.0005
[well measured, e.g. neutron lifetime] |Vus|= 0.2200 ± 0.0026 (≈sinCabibbo)
[old measurements: semileptonic kaon decays]
|Vud|2+|Vus|2+|Vub|2 = 1(4.3±1.9)∙10-3
(2.2 deviation from unitarity)
E. Goudzovski JINR SC January 20, 2005
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CKM unitarity: |Vus| measurement
Best way to determine |Vus|: semileptonic (neutral and charged) kaon decays Ke (Ke3);
A few recent measurements of BR(Ke3) lead to |Vus| values significantly above PDG 2004 values;
New measurements of |Vus| are desirable.
E. Goudzovski JINR SC January 20, 2005
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Determination of |Vus| from BR(Ke3)
where• Br(Ke3()) experimentally measured value;• K kaon lifetime, measured by other experiments;• f+(0) form-factor, evaluated theoretically;• SEW=1.0232 short distance enhancement factor;• IK phase space integral;• C2=1 for K0, C2=1/2 for K.
|Vus|=1283Br(Ke3())/K
C2GF2MK
5SEWIK
1f+
K(0)
f+K0+(0) = 0.981
0.010f+
K+0(0) = 1.002 0.010
Form-factor calculation(Cirigliano, Neufeld, Pichl, EPJC35,53,2004)
(evaluated with 1% precision)
PrecisionsKaon lifetimes:
• (KL)/(KL)=0.8%;• (K)/(K)=0.2%;
Desirable BR(Ke3) precision:• BR/BR<1%
E. Goudzovski JINR SC January 20, 2005
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NA48 experiment at CERN SPS
Main detector components:
• Magnetic spectrometer (4 DCHs) redundancy high efficiency; Δp/p = 0.5% + 0.009%*p [GeV/c].
• Hodoscope high granularity multiplicity trigger; precise time measurement (150ps).
• Liquid Krypton EM calorimeter (LKr) High granularity, quasi-homogenious; ΔE/E = 3.2%/√E + 9%/E + 0.42%; electron/pion discrimination; registration.
E. Goudzovski JINR SC January 20, 2005
DCH
LKrHOD
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|Vus| measurements by NA48
NA48/2NA48/2: Semileptonic K± decays: K±0e (Ke3) Data: 90k events in 8 hours of low intensity run 2003; Loose hodoscope trigger (1 charged track);
NA48NA48: Semileptonic KL decays: KLe (Ke3) Data: 6.8 mln events in 2 days of special run 1999; Trigger on 2 charged particles in DCH or hodoscope;
NA48/1NA48/1: Semileptonic 0 decays: 0+e Data: whole high intensity run 2002 (6.2k events); Approach different to the one for kaon decays; These preliminary results are not discussed in this
talk.
E. Goudzovski JINR SC January 20, 2005
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Measurement method: normalize Ke3 events to K0 events (Br=0.21130.0014);
Signal practically background free; Statistics selected from the minimum bias run:
Br(K0e) measurement
Decay Statistics
K++e 59∙103
Ke 33∙103
K++0 468∙103
K0 260∙103
E. Goudzovski JINR SC January 20, 2005
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K0e: Data/MC comparison
Without radiative corrections With radiative corrections
E. Goudzovski JINR SC January 20, 2005
Data/MCData/MC Data/MCData/MC
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Br(K0e): result
Br
Detector acceptance 0.038%
Trigger efficiency 0.004%
BR (K0) 0.034%
Radiative events 0.006%
MC statistics 0.022%
Total systematics 0.056%
Statistic uncertainty 0.017%
Preliminary NA48/2 result:
Br(K0e) = (5.140.02stat0.06syst)%
Main systematics:
PDG 2004
NA48/2BNLE865
K+
K K
… confirms the deviation from PDG observed by BNL E865!… the most precise measurement of Br(Ke3)!
E. Goudzovski JINR SC January 20, 2005
Bra
nch
ing
rati
oB
ranch
ing
rati
o
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Measurement method: Use minimum bias trigger to collect KL2-track
events; Normalization to Br(2-track) = 1.0048 Br(30)
Best input precision: ΔBr(2-track)/Br(2-track)<0.9%
Exactly the same selection for signal (Ke3) and normalization events, but electron identified by energy deposit in the LKr calorimeter;
Measured quantity:
Br(KLe) measurement
R=(KLe)
(KL all two-track) =N(Ke3)/acceptance(Ke3)
N(2-track)/acceptance(2-track)
E. Goudzovski JINR SC January 20, 2005
Phys.Lett. B602 (2004) 41Phys.Lett. B602 (2004) 41
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Data sample: ~80 million 2-track triggers taken during 2 days
of minimum bias run with pure KL beam;
Selection criteria: Conditions on track geometry and kinematics; Leave a sample of 12.6 million 2-track events;
Additional criterion for Ke3: Electron ID: E(LKr)/P>0.93
for 1 track; 6.8 mln candidates selected.
Data sample and selection
E. Goudzovski JINR SC January 20, 2005
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Background to Ke3 sample: K3/K3 with ± misidentified as e±
Estimated from Ke3 data with identified e± (E/p>1):
Prob(e)=5.8·10-3
Electron/pion separation
E. Goudzovski JINR SC January 20, 2005
Quality of electron ID can be estimated from the data itself!
Inefficiency of electron ID: Estimated from data with
identified ± (0.3<E/p<0.7):
Prob(e)=4.9·10-3
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Monte Carlo simulation To determine acceptances, Monte Carlo simulation of 5
significant 2-track modes involved (radiative corr. included):
Decay channel
BR (PDG04) Acceptance
KLe 38.8% 0.2599
KL 27.2% 0.2849
KL+-0 12.6% 0.0975
KL+- 2.1·10-3 0.5229
KL000D 7.6·10-3 0.0001 For average 2-track acceptance use ratios of BR: averages from PDG +
KTeV (B3/Be3, B3/Be3, …) Absolute BR’s are not used!
Acceptance(2-track events) = 0.2412 0.0004 Small normalization uncertainty: ΔA/A=0.16%
E. Goudzovski JINR SC January 20, 2005
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Errors on R=(Ke3)/(2-track)
Statistical errors are negligible; Dominating systematic uncertainty: due to
inexact knowledge of beam energy spectrum;
Summary of systematic errors:R/R, %
Energy spectrum 0.67
Normalization (input BR) 0.16
E/P cut (electron ID) 0.05
Trigger efficiency 0.05
DCH overflows 0.05
Magnet polarity 0.07
E. Goudzovski JINR SC January 20, 2005
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Data/Monte Carlo comparison
Profiles at drift chamberKaon energy spectrum: major uncertainty
E. Goudzovski JINR SC January 20, 2005
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Br(KLe): result Experimental result:
R =(KLe)
(KL all two-track) = 0.4978 0.0035
To compute Br(KLe) we use Br(KL30):
PDG 04: 0.21050.0023
KTeV 04 prel.:
0.19450.0018Br(KL30)=0.19920.0070
Result on Ke3 branching ratio:
Br(KLe) = 0.4010 0.0028(exp) 0.0035(norm)
= 0.4010 0.0045
(inconsistent data; scale factor applied to error)
E. Goudzovski JINR SC January 20, 2005
Phys.Lett. B602 (2004) 41Phys.Lett. B602 (2004) 41
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From BR’s to unitarity test
Br(K) = (5.14 0.06)% Br(KL) = 0.4010 0.0045
K: f+(0)|Vus| = 0.2245 0.0013 KL: f+(0)|Vus| = 0.2146 0.0016
K: |Vus| = 0.2241 0.0026 KL: |Vus| = 0.2187 0.0028
(PDG: 0.2200 0.0026)
|Vus|∙f+(0) ~
Br(Ke3)/K
[accuracy 1.1%]
[1.1%]
[0.6%][0.7%]
[1.3%][1.2%]
E. Goudzovski JINR SC January 20, 2005
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Results on |Vus|·f+(0)
0.2 0.21 0.22 0.23 0.24 0.25 0.26|Vus|
·f+(0)
NA48: KL
NA48/2: K± (preliminary)
(2003)
E. Goudzovski JINR SC January 20, 2005
PL B602 (2004) 41
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Conclusions Values of |Vus| obtained by experiments before
2003 are in poor agreement with CKM unitarity;
Recent NA48 measurements of |Vus|: From K:
In agreement with new BNL result and CKM unitarity; In disagreement with the old measurements;
From KL: In agreement with new KTeV and KLOE measurements; In better agreement with CKM unitarity than the old
measurements.
More precise calculations of f+(0) are desirable.
E. Goudzovski JINR SC January 20, 2005