CP Violation Results From the NA48 Experiments Giuseppina Anzivino University of Perugia and INFN on Behalf of the NA48/2 Collaboration Cambridge, CERN,

CP Violation Results From the NA48 Experiments Giuseppina Anzivino University of Perugia and INFN on Behalf of the NA48/2 Collaboration Cambridge, CERN, Chicago, Dubna, Edinburgh, Ferrara, Firenze, Mainz, Northwestern, Perugia, Pisa, Saclay, Siegen, Torino, ViennaPASCOS-07 Imperial College, London, 2-7 July 2007 July, 6th 2007 Giuseppina 07 2 Outline NA48: the CP violation experiment Brief history The NA48 detector NA48 - The CP violation parameter +- NA48/2 - Direct CP violation in K 3 decays NA48/3 (P326/NA62) Measure the BR of the rare decay K + + Testing -e universality with K l decays Conclusions July, 6th 2007 Giuseppina 07 3 Data taking periods NA48 ( ) Direct CP violation in neutral kaon decays Re( / ) = (14.7 2.2) x Measurement of CP violation parameter | +-| New result NA48/1 (2002) Rare K S decays BR (K S 0 e + e - ) = ( 0.8) x BR (K S 0 + - ) = ( 0.2) x NA48/2 ( ) Search for direct CP violation in K 3 dacays Final result and many other rare decay results! July, 6th 2007 Giuseppina 07 4 The NA48 detector Main detector components: Magnetic spectrometer (4 DCHs): 4 views: redundancy efficiency (p)/p 1.0% % p [GeV/c] Hodoscope: fast trigger and precise time measurement (150ps) Liquid Krypton e.m. calorimeter: High granularity, quasihomogeneous (E)/E = 3.2%/E + 9%/E % [GeV] Hadron calorimeter, photon vetos, muon veto counters July, 6th 2007 Giuseppina 07 5 CP violation parameter | +-| NA48 July, 6th 2007 Giuseppina 07 6 CP violation parameter +- The parameter +- fundamental observable of CP violation defined as the ratio of K L to K S CPV decay amplitudes related to indirect and direct CPV parameters How we determine | +-| Measure the ratio of the decay rates Compute Extract | +-| July, 6th 2007 Giuseppina 07 7 (K2 )/ (Ke3): event selection dominant background (K e3, K 3, K L + - 0 ) need to be suppressed by 4-5 order of magnitude data well described by MC about + - events selected select K e3 decays via the ratio E/p (energy in electromagnetic calorimeter over track momentum) about 5 million K e3 events selected with small background Data sample: special run with pure K L beam, low intensity two days in 1999, ~ 80 million events collected K L + - K L e July, 6th 2007 Giuseppina 07 8 Results published in Phys.Lett.B 645:26-35,2007 + - in data sample (IB) included (DE) subtracted (mostly CPC) used NA48 updated result for BR(K L e ) Phys.Lett.B 602:41-51,2004 INPUT: most precise mesurements KS NA48 KL KLOE BR(K S + - ) KLOE July, 6th 2007 Giuseppina 07 9 Comparison of results Good agreement with results from KTeV and KLOE Experiments contradict PDG 2004 (K 2 )/ (K e3 ) | +-| July, 6th 2007 Giuseppina Comparison of results For comparison it is important to point out the treatment of radiative decays (IB and DE) July, 6th 2007 Giuseppina CP violation in K 3 decays NA48/2 July, 6th 2007 Giuseppina CP violation in K 3 decays Look for direct CP violation in K decays (only direct CPV in K possible no mixing) Complementary CP observables in Kaons: neutral and charged slope asymmetries BR (K + )= 5.57% BR (K 0 0 ) = 1.73% Kinematics: u = (s 3 -s 0 )/m 2 v = (s 2 -s 1 )/m 2 s i = (P K P i ) 2, i=1,2,3 (3=odd ) s 0 = (s 1 +s 2 +s 3 )/3 2even 1even 3odd KK |M(u,v)| 2 ~ 1 + gu + hu 2 + kv 2 Matrix element as a function of the Dalitz variables u, v Large statistics Linear slope g dominates over quadratic terms h and k |h|, |k| ~ 35 Gev electron identification P326/NA62 is performing a dedicated run to measure R K 4 months of data taking (June-October) Collect 100K-150K Ke2 decays Overall expected precision ~ 0.3% Sensitivity to LFV in SUSY July, 6th 2007 Giuseppina Conclusions The NA48 experiments have produced important results providing fundamental contributions in the field of CP Violation both in neutral and in charged kaon systems Presented at this conference: The measurement of the CP parameter | +-| A much improved limit on direct CP violation in K 3 decays A very rich program in the near future Testing -e universality with K l decays Measure BR of the rare decay K + + Stay tuned!!