Mayda M. Velasco Northwestern University Test of Standard Model using charged kaon decays -- NA48/2 at CERN “CIPANP 2006”

Outline Direct CP violation (DCPV) K ± →  ±  0  0  “neutral” asymmetry K ± →  ±  0  0  “neutral” asymmetry 2003 data final result K ± →  ±  +  - “charged” asymmetry K ± →  ±  +  - “charged” asymmetry 2003 data final data preliminary result Test of  -e universality  (PBSM) (K ± →e ± ) / (K ± →  ± ) (K ± →e ± ) / (K ± →  ± ) Precise measurement of V us CMK parameter (K ± →  0 e ± ) / (K ± →  ±  0 ) (K ± →  0 e ± ) / (K ± →  ±  0 ) (K ± →  0  ± ) / (K ± →  ±  0 ) (K ± →  0  ± ) / (K ± →  ±  0 ) (K ± →  0 e ± ) / (K ± →  0  ± ) (K ± →  0 e ± ) / (K ± →  0  ± ) Final NEW!!

NA48/2 data taking 2003 run: ~ 50 days 2004 run: ~ 60 days Total statistics in 2 years: K      +   : ~3·10 9 K    0  0   : ~1·10 8 Rare K ± decays: BR’s down to 10 –9 can be measured Special run for semileptonics Ke3: 150K Ke3: 6000K A view of the NA48/2 beam line > 200 TB of data recorded

NA48/2 beams setup 1cm cm m He tank + spectrometer Front-end achromat Momentum selection Quadrupole quadruplet Focusing  sweeping Second achromat Cleaning Beam spectrometer (resolution 0.7%) ~7  ppp, 400 GeV K+K+ KK Beams coincide within ~1mm all along 114m decay volume focusing beams BM z magnet vacuum tank not to scale K+K+ KK beam pipe Simultaneous K + and K  beams: large charge symmetrization of experimental conditions Be target 2-3M K/spill (  /K~10),  decay products stay in pipe. Flux ratio: K + /K –  1.8 P K spectra, 60  3 GeV/c Width ~ 5mm K+/K- ~ 1mm

The NA48 detector Main detector components: Magnetic spectr. (4 DCHs): 4 views/DCH: redundancy  efficiency;  efficiency; Δp/p = 1.0% %*p [GeV/c] Δp/p = 1.0% %*p [GeV/c] Hodoscope fast trigger; precise time measurement (150ps) precise time measurement (150ps) Liq. Krypton EM cal. (LKr) High granularity, quasi- homogenious;  E /E = 3.2%/√E + 9%/E  E /E = 3.2%/√E + 9%/E % [GeV] % [GeV] Beam pipe

DCPV in K 3  decays Kinematics: s i = (P K  P  i ) 2, i=1,2,3 (3=odd  ); s 0 = (s 1 +s 2 +s 3 )/3; u = (s 3 -s 0 )/m  2 ; v = (s 2 -s 1 )/m  2. Kaon rest frame: u = 2m K ∙(m K /3  E odd )/m  2 ; v = 2m K ∙(E 1  E 2 )/m  2. Decay modes: BR(K ±  ±  +   )=5.57% BR(K ±  ±  0  0 )=1.73%. “charged” “neutral” Matrix element: |M(u,v)| 2 ~ 1 + gu + hu 2 + kv 2 “Charged (Neutral)” mode g =  ± (g n =+0.638±0.020) |h|, |k| ~ Direct CP-violating quantity: the slope asymmetry A g = (g +  g  )/(g + +g  )  0 U V DCPV: a window to physics beyond the SM  1 even  3 odd  2 even K±K±

Theoretical expectations |A g | Experimental precisions before NA48/2: SM SUSY & Newphysics Ford et al. (1970) HyperCP prelim. (2000) TNF (2005) “neutral” NA48/2 proposal [  A g ~10 -3 ] “charged” “neutral” Smith et al. (1975) “neutral” Some models beyond SM predict substantial enhancement partially within the reach of NA48/2 few … few SM estimates vary within an order of magnitude (few … few )

A g measurement strategy Project onto u axis (neglect quadratic slopes h and k (|h|, |k| << |g|) If acceptance is equal for K + and K –, A g can be extracted from a fit to the ratio R(u): For u calculation we use the energy of: odd pion in  ±  +  - odd pion in  ±  +  - the two neutral pions in laboratory frame in  ±  0  0 the two neutral pions in laboratory frame in  ±  0  0 R(u) = = n≈ n 1 += n 1 + N + (u) N - (u) 1 + g + ∙u 1 + g - ∙u g∙ug∙u 1 + g∙u 2g∙A g ∙u  g=g + -g - << 1 normalization A g =  g/2g f(u) = n∙(1+  gu) R 1 (u)=N + (u)/N  (u)

Acceptance equalization principle Z X Y Jura Saleve Achromats: K + Up Achromats: K + Down B+ BB N(A+B+K+) N(A+B-K-) R US = N(A+B-K+) N(A+B+K-) RUJ=RUJ= N(A-B+K+) N(A-B-K-) RDS=RDS= N(A-B-K+) N(A-B+K-) R DJ = Achromats (A) polarity reversed on weekly basis Spectrometer magnet (B) polarity reversed on daily basis In each ratio the charged pions are deflected towards the same side of the detector (left-right asymmetry cancels out) In each ratio the event at the numerator and denominator are collected in subsequent period of data taking (global time variations) The whole 2003 data taking is subdivided in 3 periods in which all the field configurations are present (Super Sample SS) K+K-K+K-K+K-K+K-

Acceptance cancellations (2) Double ratio: cancellation of local beam line biases effects (slight differences in beam shapes and momentum spectra): R S = R US × R DS R J = R UJ × R DJ f 2 (u)=n∙(1+ Δg S  u) 2 f 2 (u)=n∙(1+ Δg J  u) 2 R = R US ×R UJ ×R DS ×R DJ f 4 (u)=n∙(1+  g  u) 4 (3) Quadruple ratio: both cancellations The method is independent of K + /K – flux ratio and relative sizes of the samples collected Δg = 2g  A g ≈ −0.43  A g (1) Double ratio: cancellation of global time instabilities (rate effects, analyzing magnet polarity inversion): R U = R US × R UJ R D = R DS × R DJ f 2 (u)=n∙(1+ Δg U  u) 2 f 2 (u)=n∙(1+ Δg D  u) 2 Normalization Slope difference

K ± →  ±  0  0 : Selected events  +  0  0 invariant mass, GeV/c 2 Resolution: 0.9 MeV/c 2 M K PDG ± 6 MeV cut 30.3M K +    contribution 16.9M K - u v Beam Pipe The u variable is reconstructed using the LKr only K ± →  ±  0  0 )=(1.73±0.04)% BR(K ± →  ±  0  0 )=(1.73±0.04)%

NA48/2:2003 final result TNF TNF(2004) Smith et al. Smith et al. (1975) K ± →  ±  0  0 : 2003 data final result Slope difference: Δg = (2.3 ± 2.8 stat. ± 1.3 stat.(trig.) ± 1.0 syst. ± 0.3 ext. )x10 -4 = (2.3 ± 3.3)x10 -4 Charge asymmetry parameter: A g 0 =(1.8 ± 2.2 stat. ± 1.0 stat.(trig.) ± 0.8 syst. ± 0.2 ext. )x10 -4 = (1.8 ± 2.6)x10 -4 Final! The paper for the final 2003 result accepted for publication A g x10 4

Selected K ± →  ±     even pion in beam pipe 3.11x10 9 The final data sample: 3.11x10 9 events selected K + : 2.00x10 9 events  odd pion in beam pipe  M =1.7 MeV/c 2 Events  K  : 1.11x10 9 events Only spectrometer involved in the reconstruction Totally different systematics wrt the neutral analysis

K ± →  ±     : preliminary result Ford et al. (1970) HyperCP (2000) preliminary 2003 final 2003 preliminary NA48/2 (results superseding each other) A g  10 4 A g = (  1.3 ± 1.5 stat ± 0.9 trig ± 1.4 syst )  = (  1.3 ± 2.3)  data: The final result on the 2003 data has been accepted by PLB The final result on the 2003 data has been accepted by PLB (hep-ex/ ) Final

Search of Physics Beyond SM using Ke2/K  2 ? ( H ± LFV % Masiero Paradisi Petronzio hep-ph/

Search of Physics Beyond SM using Ke2/K  2 ?  (K  e )/  (K   ) = (2.416 ± stat ± syst )*10 -5  Based on 5K events taken parasitically  Same statistical error, but reduced systematic from 56h 2004-Special run  One year run - 100K events could test PBSM

TODAY: Final Ke3 & K  3 Results

Analysis from Special 8h 2003 run Simple, but Clean Selection  MC without ParticleID  Clear    after selection without condition on    mass

Final V us from NA48/2 Main uncertainty is due to Form Factor

Conclusions A g 0 = (1.8 ± 2.2 stat. ± 1.0 stat.(trig.) ± 0.8 syst. ± 0.2 ext. )x10 -4 = (1.8 ± 2.6)x10 -4 A g = (  1.3 ± 1.5 stat ± 0.9 trig ± 1.4 syst )  = (  1.3 ± 2.3)  Ke2/Kmu  4 X better … 1 year run gives 100K event … PBSM Charged Asymmetry  10 X better … still dominated by syst. Vus & Semileptonics  Better than World average… Form Factors are the limiting factor  (K  e )/  (K   ) = (2.416 ± 0.043stat ± 0.024syst)*10-5 SM like Potential window

BACKUPS

K ± →  ±  0  0 :Systematics summary ±1.3 (statistics) NTPEAK ±0.2Accidentals ±0.3 ±1.6 ±1.3 ±1.0 ±0.4 ±0.1 ±0.3 <±0.1 ±0.5 ±0.5 ±0.1 ±0.4 Effect on  g  10 4 Trigger statistical uncertainty Total systematic uncertainty L2 trigger: MBX Spectrometer alignment and Momentum scale Pion decay LKr nonlinearity External Total L1 trigger: Q1 Beam geometry Showers overlaping LKr: U calculation & fitting Systematic effect

K ± →  ±     :Systematics 0.6± ±0.7 ±0.7  0.1±0.4  0.1±0.3 ±0.3 ±0.6 ±0.3 ±0.2 ±0.4 ±0.2 ±0.1 ±0.1 Effect on  g  10 4 Systematic & trigger uncertainty Total trigger correction L2 trigger: correction Total systematic uncertainty Accidental activity (pile-up) Pion decay Momentum scale  g corrected for L2 inefficiency Raw  g L1 trigger: uncertainty only Resolution effects Acceptance and beam geometry Spectrometer alignment Systematic effect

Radiative Corrections