NA48-2 new results on Charged Semileptonic decays Anne Dabrowski Northwestern University Kaon 2005...

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)


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


K± Beam line

PK spectra, 603 GeV/c

54 60 66


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-


Data sample to measure Br (K±π0e±ν)


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)%


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)


NA48-2 preliminary result Br (K±π0e±ν)

*Systematics will be reduced before publication *will be reduced in the future by NA48

**

**

**

PDG

**


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 )


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


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


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


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


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


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 !


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!!!!


Summer 2005 Semileptonic Kaon decay results

Vus x f

+(0

)

NA48NA48

THEORY K+

THEORY

THEORY K0


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+


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

)


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)


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


• 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

NA48-2 new results on Charged Semileptonic decays Anne Dabrowski Northwestern University Kaon 2005...

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