NA48-2 new results on Charged Semileptonic decays Anne Dabrowski Northwestern University Kaon 2005 Workshop 14 June 2005

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 2 Results to be shown today Br (K ±  π 0 e ± ν ) (ICHEP) Γ(π 0 μ ± ν ) / Γ(π 0 e ± ν ) (NEW)

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 3 Status of extracting Vus from Semileptonic Kaon Decays from ICHEP 2004 V us x f + (0) F. Mescia hep-ph/ Input: Br(K ± e3 ) from NA48/2 ? Input: Br(K ± μ3 ) from NA48/2 to be shown today! THEORY

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 4 K± Beam line P K spectra, 60  3 GeV/c

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 5 NA48 Detector Muon system: s(t)  350 ps Spectrometer: p T kick ~250 (125) MeV/c  (P)/P  0.48%  P[GeV/c]% LKr Calorimeter:  (E)/E  3.2%/√E  9%/E  0.42% s(t)  265 ps for 50 GeV e-

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 6 Data sample to measure Br (K ±  π 0 e ± ν )

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 7 Kaon Mass cut  Use the Kaon Mass cut and Particle ID Features of selection: Electron and pion ID and Kaon mass cut E/P > 0.95 for electrons Global efficiency (97.37±0.09) % E/P < 0.95 for pions Global efficiency (99.522±0.001)%

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 8 DATA/MC for K ±  π 0 e ± ν Without radiative corrections With radiative corrections Ginsberg prescription DATA DATA/MC (GeV)

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 9 NA48-2 preliminary result Br (K ±  π 0 e ± ν ) *Systematics will be reduced before publication *will be reduced in the future by NA48 * * * PDG *

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 10 How well can we measure (K ±  π 0 μ ± ν) ? Selected Events π0e+νπ0e+ν 59K π0e-νπ0e-ν 33K π0μ+νπ0μ+ν 50K π0μ-νπ0μ-ν 27K measure π 0 μ ± ν with comparable statistics to the π 0 e ± 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 + ) K  3 (depends on λ + and λ 0 )

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 11 Very consistent results obtained with 2 independent for Muon ID Method 2: Global efficiency: (96,16 ± 0.01) % Signals in Calorimeters : –LKr (cluster<1.5 GeV) & HAC (cluster<5 GeV) Global Efficiency: ( ± 0.002)% Method 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

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 12 Result Γ(Kμ3) / Γ(Ke3) NA48/2: Γ(K μ ± 3) / Γ(Ke ± 3): ± (stat) ± (sys) ± (sys λ +,λ 0 ) Systematics include Trigger MC statistics and particle ID efficiency Background subtraction< Stability of result under change of λ +, λ 0 ** overestimated – will be improved Improvement in the error compared to previous results

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 13 Theory and experiment for Theory and experiment for Γ(Kμ3) / Γ(Ke3) Fearing, Fischbach, Smith (1970) Measured values – PDG 2004 : Good agreement between theory, λ 0, λ + & Good agreement between theory, λ 0, λ + & Γ(K  3)/Γ(Ke3) KEK 2001 E246 NA PDG 2000 THEORY

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 14 Result for the Br(K  3) Systematics include Trigger MC statistics and particle ID efficiency Background subtraction< Stability of result under change of λ +, λ Given NA48/2 result, Γ(K  3)/Γ(Ke3) ± (stat) ± (sys) ± (sys λ +,λ 0 ) And using the BNL E865 result Br(Ke3) = (5.13 ± 0.10)% Br(K  3) = (3.462 ± 0.018(stat) ± 0.006(sys) ± (sys λ +, λ 0 ) ± 0.068(norm BNL E865 Ke3))% PDG

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 15 Result for Br (Ke3) and Br (K  3) Recall PDG: Br(Ke3) = ± Recall PDG: Br(K  3) = ± PDG

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 16 Vus from NA48/2 results Assuming K l3 decays: 0 - to 0 -, pure V 2.31(22)-0.10(16) 2.31(22)+0.20(20) hep-ph/ F. Mescia Phase space integral (Pole approximation, full region)  Extraction of Vus from NA48 results comparable !

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 17  SM => V us = ± – Assuming unitarity  Leutwyler-Roos f + (0) KL =0.961 ±  f + (0) K+ =0.982 ± –Therefore SMSM –V us | f + (0)| = / –Factor of COMPARED TO ICHEP to get K + –Compared to NA48/2NA48/2 –K e3  V us |f + (0)| = / –K  3  V us |f + (0)| = / V us  error dominated by theoretical uncertainties At face value: Good agreement between NA48/2 & SM … Details to be taken care by theorists!!!!

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 18 Summer 2005 Semileptonic Kaon decay results V us x f + (0) NA48 THEORY K + THEORY THEORY K 0

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 19 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 & K  3  More than 2 Million Ke3 –no ambiguity in the energy of the decaying K+

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 20 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) K2K2  Transverse Momentum (GeV) K e3 Kμ3Kμ3Kμ3Kμ3 K3K3K3K3 K3oK3oK3oK3o Momentum track (GeV) Transverse Momentum (GeV)

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 21 Conclusion New Precision measurement of Γ(K  3)/Γ(Ke3) is consistent with Standard Model Vus from Γ(K  3) 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 + π 0 )

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 22 Muon Signals in the Calorimeters: Signal in the Hadronic Calorimeter Signal in the Liquid Krypton Electromagnetic Calorimeter 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

A. Dabrowski, June NA48-2 new results on Charged Semileptonic decays 23 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: –Correction to Ke3+ acceptance: ± K- –Events selected out: 63 – Events selected in: –Correction to Ke3- acceptance: ± 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 K e3γ events outside dalitz plane Correction Ke3g K+/K- K e3(γ) events inside dalitz plane