NA48-2 new results on NA48-2 new results on Charged Semileptonic Charged Semileptonic
decaysdecays
Anne DabrowskiNorthwestern University
Kaon 2005 Workshop14 June 2005
2 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Results to be shown todayResults to be shown today
• Br (K±π0e±ν) (ICHEP)
• Γ(π0μ±ν) / Γ(π0e±ν) (NEW)
3 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Status of extracting Vus from Status of extracting Vus from Semileptonic Kaon Decays from ICHEP Semileptonic Kaon Decays from ICHEP
20042004V
us x
f+(0
)
F. Mescia hep-ph/0411097
Input: Br(K±
e3) from NA48/2
??
Input:
Br(K±μ3) from
NA48/2 to be shown today!THEORY
4 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
K± Beam line
PK spectra, 603 GeV/c
54 60 66
5 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
NA48 Detector
Muon system:Muon system:s(t) s(t) 350 ps 350 ps
Spectrometer:pT kick ~250 (125) MeV/c(P)/P (P)/P 0.48% 0.48% 0.009 0.009 P[GeV/c]%P[GeV/c]%
LKr Calorimeter:(E)/E (E)/E 3.2%/√E 3.2%/√E 9%/E 9%/E 0.42%0.42%s(t) s(t) 265 ps for 50 GeV e- 265 ps for 50 GeV e-
6 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Data sample to measure Br (K±π0e±ν)
7 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Kaon Mass cut
Use the Kaon Mass cut and Particle IDUse the Kaon Mass cut and Particle ID
Features of selection: Electron and pion ID and Kaon mass
cutE/P > 0.95
for electronsGlobal efficiency (97.37±0.09) %
E/P < 0.95
for pions Global efficiency (99.522±0.001)%
8 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
DATA/MC for K±π0e±ν
Without radiative Without radiative correctionscorrections
With radiative With radiative correctionscorrections
Ginsberg prescription•DATA
•DATA
DATA/MCDATA / MC
(GeV)(GeV)
9 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
NA48-2 preliminary result Br (K±π0e±ν)
*Systematics will be reduced before publication *will be reduced in the future by NA48
**
**
**
PDG
**
10 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
How well can we measure (K±π0μ±ν)?
Selected Events
π0e+ν 59K
π0e-ν 33K
π0μ+ν 50K
π0μ-ν 27K
measure π0μ±ν with comparable statistics to the π0e±ν
What are the difference in the muon and electron channel?
1. Particle ID (electron ID vs muon ID)
2. Radiative corrections (Ke3 ~ 0.2% vs Kmu3 ~ 0.02%)
3. Form factor parameterization
• Ke3 (depends just on λ+ )
• K3 (depends on λ+ and λ0 )
11 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Very consistent results obtained with 2 independent for Muon ID
Method 2:Method 2:
Global efficiency: (96,16 ± 0.01) %
Signals in Calorimeters :– LKr (cluster<1.5 GeV)
& HAC (cluster<5 GeV)
Global Efficiency:(99.763 ± 0.002)%
Method 1Method 1
Using the Muon Detector,– a hit in time with the
hodoscopes of 2ns
We can cross check our muon ID with 2 different methods
1. Using Muon Detector
2. Using the minimum ionizing particle signal in calorimeters
12 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Result Γ(Kμ3) / Γ(Ke3)
NA48/2: Γ(NA48/2: Γ(KKμμ±±33) / Γ() / Γ(KeKe±±33):):
0.6749 ± 0.0035 (stat) ± 0.0011 (sys) ± 0.0021(sysλ+,λ0)
Systematics includeTrigger 0.0004
MC statistics and particle ID efficiency
0.0011
Background subtraction
< 0.0001
Stability of result under change of λ+, λ0
** overestimated – will be improved
0.0021
Improvement in the error Improvement in the error compared to previous compared to previous resultsresults
13 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Theory and experiment for Theory and experiment for Γ(Kμ3) / Γ(Ke3)
)(5646.11546.06457.0)(
)( 200
20
3
3
OK
K
e
20
2
10)16.077.1(
10)07.078.2(
Fearing, Fischbach, Smith (1970)
Measured values – PDG 2004 :
Good agreement between Good agreement between theorytheory, , λλ00 , , λλ++ & & Γ(K3)/Γ(Ke3)
KEK 2001
E246NA482005
PDG 2000
THEORY
14 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Result for the Br(KResult for the Br(K3)3)
Systematics include
Trigger 0.00003
MC statistics and particle ID efficiency
0.00035
Background subtraction < 0.00001
Stability of result under change of λ+, λ0
0.00011
Given NA48/2 result, Γ(K3)/Γ(Ke3)
0.6749 ± 0.0035(stat) ± 0.0011(sys) ± 0.0021(sys λ+,λ0 )
And using the BNL E865 result Br(Ke3) = (5.13 ± 0.10)%
Br(K3) = (3.462 ± 0.018(stat) ± 0.006(sys) ± 0.011 (sys λ+,λ0) ± 0.068(norm BNL E865 Ke3))%
PDG
15 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Result for Br (Ke3) and Br (KResult for Br (Ke3) and Br (K3)3)
)%03.005.002.014.5()( )0
(0
BrsysstateKBr
)%07.001.002.046.3()( 865)0
(0
EeBrsysstatKBr
Recall PDG:Br(Ke3) = 0.0487 ± 0.0006
Recall PDG:Br(K3) = 0.0327 ± 0.0006
PDGPDG
16 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Vus from NA48/2 resultsVus from NA48/2 results
• Assuming Kl3 decays: 0- to 0-, pure V2
)2(022
3 )1)(,(|)0(|||)( Klem
KSU
lKus
enhFl IfVGK
2.31(22) -0.10(16)
2.31(22) +0.20(20)
hep-ph/0411097 F. Mescia
(%))2(KSU (%)Kl
em3eK
3K
000459.0073684.0),(
000609.0110528.0),(
0,
0,
K
eK
I
I
Phase space integral
(Pole approximation, full region)
0015.02204.0|)0(|
0015.02192.0|)0(|
3
3
fVK
fVK
us
use
Extraction of Vus from NA48 results comparable !
17 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
SM => VSM => Vusus = 0.2265 = 0.2265 ±± 0.0022 – Assuming unitarity (@ICHEP) 0.0022 – Assuming unitarity (@ICHEP)
Leutwyler-RoosLeutwyler-Roos ff++(0)(0)KLKL=0.961 =0.961 ±± 0.008 0.008 f f++(0)(0)K+K+=0.982=0.982±± 0.008 0.008
– ThereforeTherefore• SM SM
– VVus us | f| f++(0)| = 0.2224 +/- 0.0028 (0)| = 0.2224 +/- 0.0028 – Factor of 1.022 COMPARED TO ICHEP to get KFactor of 1.022 COMPARED TO ICHEP to get K++
– Compared toCompared to• NA48/2 NA48/2
– KKe3e3 VVusus |f |f++(0)| = (0)| = 0.2192 +/- 0.00150.2192 +/- 0.0015 – KK33 VVusus |f |f++(0)| = (0)| = 0.2204 +/- 0.00150.2204 +/- 0.0015
VVus us error dominated by theoretical error dominated by theoretical
uncertaintiesuncertainties
At face value: Good agreement between NA48/2 & SM
… Details to be taken care by theorists!!!!
18 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Summer 2005 Semileptonic Kaon decay results
Vus x f
+(0
)
NA48NA48
THEORY K+
THEORY
THEORY K0
19 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Other Semileptonic Results NA48/2
• Γ (e±ν)/ Γ (μ±ν)– Sample of Ke2 from 2003 data taking larger
than the combined statistics in PDG!– Preliminary result will be shown in the
poster session by Luca Fiorini– In addition:
•2004 data sample from a dedicated special min-bias run with as large a sample as all the 2003 statistics combined
• Form factor and radiative decays for Ke3 & K3 More than 2 Million Ke3 – no ambiguity in the energy of the decaying
K+
20 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Have a reason to be suspicious of main Br for K+ … re-measurement
on-going• 1 track Analysis to
measure main Branching ratios simultaneously– Only the information
from the PT and momentum of the track, and particle ID
Momentum track (GeV)
K2
Tra
nsv
erse
Mom
entu
m (
GeV
)
KKe3e3
KKμμ33 KK33
KK33oo
Momentum track (GeV)
Tra
nsv
erse
Mom
entu
m (
GeV
)
21 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Conclusion• New Precision measurement of
Γ(K3)/Γ(Ke3) is consistent with Standard Model
• Vus from Γ(K3) and Γ(Ke3):– Consistent between themselves– Consistent with Standard model
• There will be a significant reduction in errors for the partial widths with a better measurement of Br(π+π0)
22 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
Muon Signals in the Calorimeters:
Signal in the Hadronic
Calorimeter
Signal in the Liquid Krypton
Electromagnetic Calorimeter
Energy (GeV)
Energy (GeV)
(98.58 ± 0.01) % of muons deposit cluster < 5.0 GeV in HAC
(99.71 ±0.01) % of muons have cluster<1.5 GeV in LKr
23 A. Dabrowski, June 14 2005NA48-2 new results on Charged Semileptonic decays
• Events are only generated (and corrected for radiative events) inside the dalitz plane in ke3 MC. Hence we need to correct for the acceptance of ke3(γ) for events in the data which lie outside of the dalitz plane.
• Look at data events in v.s. out of dalitz plot
• K+ – events selected out:152– Events selected in: 57550– Correction to Ke3+ acceptance:
1.0026±0.0002• K-
– Events selected out: 63– Events selected in: 31683– Correction to Ke3- acceptance:
1.0020±0.0004
• Assume that in the data, all events outside of the dalitz plot are ke3(γ) candidates, have not corrected this ratio yet for possible sources of background – but this is assumed small
Ke3γ events outside dalitz plane
Correction Ke3g K+/K-Ke3(γ) events inside dalitz plane