(Scuola Normale Superiore & INFN Pisa) Recent NA48 results: |+–| from KL+–, DCPV in K3 decays, |Vus| from K0l. Evgueni Goudzovski (Scuola Normale Superiore & INFN Pisa) on behalf of the NA48/2 Collaboration: Cambridge, CERN, Chicago, Dubna, Edinburgh, Ferrara, Firenze, Mainz, Northwestern, Perugia, Pisa, Saclay, Siegen, Torino, Vienna EPS HEP Conference 2007 Manchester / July 19-25, 2007

Overview Presentation of several recent NA48 results: Measurement of BR(KL+–) and the indirect CP violation parameter || with NA48 data (run 1999); Study of the K3 decays: a search for direct CP violating charge asymmetries Ag with NA48/2 data (runs 2003/04); Study of the semileptonic K0l decays, and measurement of the CKM matrix element |Vus| with NA48/2 data (run 2003). NA48 NA48/1 NA48/2 NA62 (first phase) 2007 Ke2/K2 run … E. Goudzovski / Manchester, July 19th, 2007

NA48 experiments @ CERN A fixed target experiment  modern CERN kaon physics program Jura mountains France NA48; NA62 SPS LHC Geneva airport Switzerland N E. Goudzovski / Manchester, July 19th, 2007

The NA48 detector Main detector components: Magnetic spectrometer (4 DCHs): 4 views/DCH: redundancy efficiency; used in trigger logic; Δp/p = 1.0% + 0.044%*p [GeV/c]. Hodoscope fast trigger; precise time measurement (150ps). Liquid Krypton EM calorimeter (LKr) High granularity, quasi-homogenious; E/E = 3.2%/E1/2 + 9%/E + 0.42% [GeV]; x=y=0.42/E1/2 + 0.6mm (1.5mm@10GeV). Hadron calorimeter, muon veto counters, photon vetoes. Beam pipe Beams E. Goudzovski / Manchester, July 19th, 2007

Indirect CP violation parameter || in KL+– decays E. Goudzovski / Manchester, July 19th, 2007

CP violation parameter || Definition: (a fundamental observable of CP violation) A(KL+–)  =  + ’ = A(KS+–) Measurement method: The quantity measured directly is BR(KL+–)/BR(KLe):  normalization to the largest decay mode; Then || is computed as BR(KL+–) KS || = KL BR(KS+–) External input: best single measurements KS lifetime: KS = (0.895980.00070)10–10 s (NA48 ’02); KL lifetime: KL = (5.0840.023)10–8 s (KLOE ’06); BR(KLe) = 0.40220.0031 (NA48 ’04 + improved KL30: KTeV, KLOE); BR(KS+–) = 0.691960.00051 (KLOE ’06). E. Goudzovski / Manchester, July 19th, 2007

E/p for pions and electrons ||: event selection Dedicated 2-days run in 1999: ~80 million 2-track events recorded KL+– KLe CP-violating process: suppression of the main channels by 4-5 orders of magnitude required; Small background well understood in terms of simulation achieved: 0.5%; Events selected: 47,142. Selection based on electron identification by LKr energy deposit: electrons have E/p  1; Equally small background achieved: 0.5%; Events selected: 4,999,126. E/p for pions and electrons Events E. Goudzovski / Manchester, July 19th, 2007

||: results || = = (2.223 0.012) 10–3 Phys. Lett. B645 (2007) 26 The directly measured value: R = BR(KL+–) / BR(KLe) = (4.835  0.022stat.  0.016syst.)  10–3 Corrections and uncertainties on R Uncertainty source Correction Uncertainty Particle ID +1.34% 0.05% K2 background –0.49% 0.03% Muon ID +0.48% 0.18% Trigger –1.29% 0.11% Energy spectrum 0.20% Radiative corrections 0.10% MC statistics Totally +0.04% 0.33% Branching fraction: BR(KL+–) = (1.941  0.019)  10–3 Includes the +– (IB) component; Direct emission (CP conserving) component was subtracted. The CP violation parameter: BR(KL+–) KS || = = (2.223 0.012) 10–3 KL BR(KS+–) E. Goudzovski / Manchester, July 19th, 2007

||: comparison of results BR(KL+–) / BR(KLe), 10–3 |+–|, 10–3 Good agreement with KTeV and KLOE results; These new measurements contradict the PDG’04 value E. Goudzovski / Manchester, July 19th, 2007

2. Direct CP violation parameter Ag in K3 decays E. Goudzovski / Manchester, July 19th, 2007

CP violation parameter Ag Two decay modes: BR(K±±+)=5.57%; BR(K±±00)=1.73%. Matrix element: |M(u,v)|2 ~ 1 + gu + hu2 + kv2 Kinematics: si = (PKPi)2, i=1,2,3 (3=odd ); s0 = (s1+s2+s3)/3; u = (s3-s0)/m2; v = (s2-s1)/m2. V “Charged” mode g = (21.134±0.017)% |h|, |k| ~ 10-2 Kaon rest frame: u = 2mK∙(mK/3Eodd)/m2; v = 2mK∙(E1E2)/m2. U Direct CP-violating quantity: the slope asymmetry Ag = (g+g)/(g++g)  0 E. Goudzovski / Manchester, July 19th, 2007

Theory & experiment |Ag| Experimental precisions before NA48/2: E. Gámiz et al., JHEP 10 (2003) 42 [Ag~10-3, dominated by systematics] SM estimate (NLO ChPT): Agc = (–1.41.2)10–5; Agn = (1.10.7)10–5. Smith et al. (1975) “neutral” 10-2 Ford et al. (1970) |Ag| HyperCP prelim. (2000) TNF (2005) “neutral” 10-3 NA48/2 proposal G. D’Ambrosio et al., PLB480 (2000) 164 Models beyond the SM predict substantial enhancement partially within the reach of NA48/2. “neutral” 10-4 “charged” SUSY & 10-5 SM New physics Asymmetry of integrated decay widths is strongly suppressed. 10-6 E. Goudzovski / Manchester, July 19th, 2007

K3 asymmetry: method M=1.7 MeV/c2 Time stability of Ag Events Control 3.11x109 events selected Control M(3), GeV/c2 Measurement method: Observable: the ratio of u-projections of reconstructed K+ and K– kinematic distributions; Achieve cancellation of major systematic effects by combining data collected with opposite beam line/spectrometer polarities; Monitor residual fake instrumental asymmetries with control quantities. E. Goudzovski / Manchester, July 19th, 2007

K3 asymmetry: result arXiv:0707.0697, submitted to EPJC g = (0.6 ± 0.7stat ± 0.4trig ± 0.5syst)  10-4 g = (0.6 ± 0.9)  10-4 Ag = (1.5 ± 1.5stat ± 0.9trig ± 1.1syst)  10-4 Ag = (1.5 ± 2.1)  10-4 FINAL RESULT based on the full statistics accumulated in 2003 and 2004 runs Measurements of Ag A factor ~20 better precision than the previous measurements; Uncertainties dominated by those of statistical nature; Result compatible with the Standard Model predictions, no evidences for New Physics; NA48/2 design goal reached! Ag  104 preliminary 2003 final 2003+2004 final 2003 HyperCP (2000) Ford et al. (1970) NA48/2 (results superseding each other) E. Goudzovski / Manchester, July 19th, 2007

K00 asymmetry: result arXiv:0707.0697, submitted to EPJC M=1.1 MeV/c2 Events Control Control M(3), GeV/c2 |V| Statistical precision in Ag0 similar to “charged” mode: Ratio of “neutral” to “charged” statistics: N0/N±~1/30; Ratio of slopes: |g0/g±|3/1; A favourable Dalitz-plot distribution (gain factor f~1.5). Final result with 2003+2004 sample (based on 91106 events) Ag0 = (1.8±1.8)10-4 U E. Goudzovski / Manchester, July 19th, 2007

3. CKM matrix element |Vus| with the K0l decays E. Goudzovski / Manchester, July 19th, 2007

Extraction of |Vus| from Kl3 GF2 (Kl3) = BR(Kl3)/K = mK5 SEW |Vus|2 |f+(0)|2 IK (1+K) 3843 Short-distance radiative correction The measured quantity Phase space integral containing form-factor parameterization Long-distance correction (isospin symmetry breaking) Analysis method: measurement of BR(Ke3)/BR(K0), BR(K3)/BR(K0)  normalization to a large and well-know mode with a similar signature. Data sample: ~3 days of dedicated running (very soft trigger) in 2003 Event samples collected Decay channel K+ K– Background level K0e 56,195 30,898 ~10–4 K0 49,364 27,525 ~0.2% K0 461,837 256,619 E. Goudzovski / Manchester, July 19th, 2007

Kl3 and |Vus|: results |Vus|f+(0) = 0.21930.0012 [Ke3] Eur. Phys. J. C50 (2007) 329 + erratum BR(Ke3) measurements BR(Ke3)/BR(K0) = 0.24700.0009stat.0.0004syst. % ISTRA+ 2007 BR(K3)/BR(K0) = 0.16370.0006stat.0.0003syst. BNL E865 2003 NA48/2 2007 BR(Ke3) = (5.1680.019stat.0.008syst.0.030norm.)% BR(K3) = (3.4250.013stat.0.006syst.0.020norm.)% Both measurements above the PDG’06 average, but agree with other experiments normalizing to 0; Comparison to KLOE: a hint that the PDG’06 value of BR(0) is biased (waiting for KLOE 0!) KLOE (2007 absolute measurement) PDG’06 % BR(K3) measurements |Vus|f+(0) = 0.21930.0012 [Ke3] NA48/2 2007 = 0.21770.0013 [K3] Errors dominated by those of long-distance corr. PDG’06 |Vus| = 0.22770.0013other0.0019th. = KLOE (2007 absolute measurement) = 0.22770.0023 Combined Ke3 and K3 result: compatible to CKM unitarity Error dominated by the theoretical uncertainty of f+(0) E. Goudzovski / Manchester, July 19th, 2007

Conclusions A selection of new NA48 kaon physics results obtained in 2007: Precise |+–| measurement:  in agreement with KTeV and KLOE results Precise search for direct CP violating charge asymmetry in the 3-pion decays of the K:  order of magnitude improvement in precision  in agreement with the SM predictions Precise measurement of |Vus| with semileptonic K decays:  agreement with other experiments normalizing to 0  disagreement with absolute measurements  slight disagreement with the PDG E. Goudzovski / Manchester, July 19th, 2007