Experimental Setup – Simultaneous K+/K- beams

1. 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 B+ magnet TAX 17 TAX 18 FDFD K+ K+ focusing beams K- K- DFDF Quadrupole 2nd Quadruplet ACHROMAT 10 cm vacuum tank He tank + spectrometer FRONT-END ACHROMAT 1cm not to scale Vus x f+(0) 200 250 m 50 100 beams coincide within <1mm 114m decay volume Data sample from a special low intensity run 2003 NA48/2 Detector Experimental Setup – Simultaneous K+/K- beams Data Sample: • 8 h K+/K- with min bias trigger ... no cut at trigger level on Dalitz plot, & εtrig ~ 99.8% Ke3 Br measurement: • Normalize Ke3 events to π ±π0 events • Br(π ±π0) = 0.2113±0.0014 • Selected Events: • Ke3+ ..... 59k Ke3- ..... 33k • π ±π0 ..... 468k π ±π0 ..... 260k • 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± Vusfrom Ke3 Status of Vus from Km3data Data/MC Comparison for Br( Km3) measurement Muon ID efficiency using muonsfrom K±→μ±ν • Similar Analysis, Normalize Km3 to π ±π0 • Particle ID … 2 Methods for muon ID • Using the Muon Veto for Muon ID (global 99.92% efficient) • 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 Mom. of Track Energy π0 Data/MC looks good! Br(Km3) available soon!! CKM matrix – Unitary Problem? Patera New Determinations of Vus Inputs into extracting Vus from Ke3 • Unitarity of CKM matrix requires: |Vud|2 +|Vus|2+ |Vub|2 = 1 • PDG 2004 data: |Vud| = 0.9738 ± 0.0005 - well measured |Vub| = (3.67 ± 0.47).10-3 - ( |Vub|2 ≈ 10-5 negligible) • SM prediction |Vus| = 0.2274 ± 0.0021 • Experimental value (begining 2003) |Vus| = 0.2200 ± 0.0026  |Vus|= 0.0074 ± 0.0033 ~2.2  discrepancy • 1 % Measurement needed • (limited by theory) New Preliminary NA48/2 Br(Ke3) Data/MC Comparison for Br(Ke3) measurement Br(Ke3) = (5.14 ± 0.02 stat± 0.06 syst)% pipi0 Ke3 Mom. of Track Energy π0 Mom. of Track Energy π0 Data/MC Data/MC Data/MC Data/MC 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