Measurement of the Cabbibo-Kobayashi-Maskawa Quark-Mixing matrix element Vus from 2003 data from NA48/2 experiment at CERN

Anne Dabrowski

(work done in collaboration with advisor Prof. Mayda Velasco, research assistant Michal Szleper and the NA48/2 Collaboration at CERN)

Northwestern University, Evanston, Il

Measurement of the Cabbibo-Kobayashi-Maskawa Quark-Mixing matrix element Vus from 2003 data from NA48/2 experiment at CERN

Anne Dabrowski

(work done in collaboration with advisor Prof. Mayda Velasco, research assistant Michal Szleper and the NA48/2 Collaboration at CERN)

Northwestern University, Evanston, Il

Experimental Setup – Simultaneous K+/K- beams

1cm

50 100

DFDFQuadrupole 2nd

Quadruplet ACHROMATFRONT-END ACHROMAT

10 cm

200 250 m

vacuum tank

He tank+ spectrometer

magnetB+

K+

K-

K+

K-

focusing beams

114m decay volumebeams coincide within <1mm

FDFD

not to scale

TAX 17 TAX 18

NA48/2 Detector

•Main detector components● Magnet spectrometer

➢Two drift chambers before and two after spectrometer magnet

➢Momentum resolution < 1% for 20 GeV/c momentum

● Anti-counters ● Liquid Krypton Calorimeter ● Hadron Calorimeter● Muon Veto system● Beams K±

Data sample from a Data sample from a special low intensity runspecial low intensity run 20032003

Data SampleData Sample::• 8 h K8 h K++/K/K-- with min bias trigger with min bias trigger

... no cut at trigger level on Dalitz ... no cut at trigger level on Dalitz plot, & plot, & εεtrigtrig ~ 99.8% ~ 99.8%

KKe3e3 Br measurement: Br measurement:

• Normalize KNormalize Ke3e3 events to events to π π ±±ππ00 events events

Br(Br(π π ±±ππ00) = 0.2113) = 0.2113±±0.00140.0014• Selected EventsSelected Events::

• KKe3e3++ ..... 59k K ..... 59k Ke3e3

-- ..... 33k ..... 33k• π π ±±ππ00 ..... 468k ..... 468k π π ±±ππ00 ..... 260k ..... 260k

Data/MC Comparison for Br(KBr(Ke3e3) )

measurement

Data/MC

Mom. of Mom. of TrackTrack

pipi0 pipi0

Energy Energy ππ00

Data/MC

Mom. of TrackMom. of Track Energy Energy ππ00

KKe3e3

Data/MC Data/MC

New Preliminary NA48/2 Br(KNew Preliminary NA48/2 Br(Ke3e3))

Br(KBr(Ke3e3) = (5.14 ) = (5.14 ±± 0.02 0.02 statstat ± ± 0.06 0.06 systsyst)%)%

Systematics: σsys

variation of reconstruction cuts ±0.038%

Br(K→ π ±π0) ±0.034%

Radiative events ±0.006%

Trigger efficiency ±0.004%

MC statistics ±0.022%

Total Systematics ±0.056%

Statistical uncertainty ±0.017%

VVusus fromfrom K Ke3e3

Inputs into extracting Vus from Ke3CKM matrix – Unitary Problem?

• Unitarity of CKM matrix requires:Unitarity of CKM matrix requires:

|V|Vudud||2 2 +|V+|Vusus||22+ |V+ |Vubub||22 = 1 = 1• PDG 2004 data:PDG 2004 data:

|V|Vudud| = 0.9738 ± 0.0005 - well measured| = 0.9738 ± 0.0005 - well measured

|V|Vubub| = (3.67 ± 0.47).10| = (3.67 ± 0.47).10-3 -3 - ( |Vub|- ( |Vub|22 ≈ 10 ≈ 10-5-5 negligible) negligible)• SM prediction SM prediction

|V|Vusus| = 0.2274 ± 0.0021| = 0.2274 ± 0.0021• Experimental value (begining 2003)Experimental value (begining 2003)

|V|Vusus| = 0.2200 ± 0.0026 | = 0.2200 ± 0.0026 |V|Vusus|| = 0.0074 ± 0.0033 ~2.2 discrepancy= 0.0074 ± 0.0033 ~2.2 discrepancy

1 % Measurement needed 1 % Measurement needed (limited by theory)(limited by theory)

Vu

s x

f+(0

)

Patera New Determinations of Vus

• Similar Analysis, Normalize Km3 to π ±π0

– Particle ID … 2 Methods for muon ID1. Using the Muon Veto for

Muon ID (global 99.92% efficient)

2. Using the Electromagnetic and Hadronic calorimeters for 1-MIP signal (max 98.% efficient, but momentum dependent)

– Number of events:• μ+π0ν (μ-π0ν ) 60 k (33 k) –

Statistical error comparable to Ke3

Status of VStatus of Vusus from from K K33 datadata

Muon ID efficiency using muonsMuon ID efficiency using muons fromfrom K K±±→→μμ±±νν

Radiative correction in Measurement of Br(Ke3)

Ginsberg Implementation OK in MC generated events

– see paper (Ginsberg Phys Rev vol 162 Num 5 25 October 1967)

Data/MC, radiative corrections on

Data/MC, radiative corrections off

Data/MC Comparison for Br( KData/MC Comparison for Br( Km3m3) measurement

Data/MC looks good! Br(KData/MC looks good! Br(K33) available soon!!) available soon!!

Mom. of TrackMom. of Track Energy Energy ππ00