The CP-violation experiments NA48 at CERN Manfred Jeitler Institute of High Energy Physics of the Austrian Academy of Sciences RECFA meeting Innsbruck, 26 March 2004

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 overview n the original NA48 experiment –direct CP-violation: Re  ’/  n measurements in a high-intensity K S beam –K S   0  0  0 –K S   0 e + e - and K S   0  +  - n measurements of direct CP-violation with charged kaon beams –K      +  - n future ?   

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 The original aim of NA48: measuring Re  ’/  KSKS   KSKS   KLKL   KLKL    ’/   0: direct CP-violation exists ”frequent“ ”rare“ /

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 The neutral kaon beams of NA48

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 The detector of the NA48 experiment at CERN spectrometer (consisting of 4 drift chambers and a magnet) and hadron calorimeter for measuring     -decays electromagnetic liquid-krypton calorimeter for measuring     -decays magnet DCH hadron calorimeter

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 The liquid-krypton calorimeter measures decays of kaons into neutral particles: K       filled with 9 m 3 of liquid krypton part of trigger electronics built by HEPHY, Vienna

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 NA48  Re  ’/  = (14.7 ± 2.2)  NA48 (all data)  Re  ’/  : the experimental result (15.3 ± 2.6)   Re  ’/  = (16.6 ± 1.6)  new world average (13.7 ± 3.1)  10 -4

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 Re  ’/  : the shape of the theory considering the present accuracy of calculations, there is no use to further improve measurements

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004

pay one – take three:  charged kaons  charged kaons    

CP-violation in K 0 S decays: K S   0  0  0  K S   0 e + e - and K S   0  +  - 

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 The high-intensity K S -beam

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 K S   0  0  0 n CP-violating decay –no CP-conserving components such as in K S   +  -  0 counterpart to the “classical” CP-violating decay K L   0  0 –CP |  0  0  0 > = - |  0  0  0 > while –CP | K S > ~ CP | K 1 > = + | K 1 > n described by parameter

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 K S   0  0  0 : the result n result consistent with zero with 5% probability n limit on branching fraction: BR(K S   0  0  0 ) < 1.4  at 90% confidence level (one order of magnitude better than previous limit)

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 K S   0  0  0 and CPT Bell-Steinberger relation

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 K S   0 e + e - and K S   0  +  -

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March events found with a background of K S   0 e + e -

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 K S   0  +  -

CP-violation in charged K decays: K      +  - K      0  0 

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 n measure decays of K + and K – n direct CP-violation in K   (3  )  :  M( u,v )  1 + g  u + h  u 2 + k  v 2 A g  (g +  g – )/(g + + g – ) n measurement of the ratio R ( u )   d v  M + ( u,v )  2   d v  M – ( u,v )  2  constant simultaneous K + and K – beams n same acceptance, alternating magnetic field high-precision measurement of K   (3  ) 

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 asymmetry parameter A g in K   (3  )  theoretical predictions and expected experimental accuracy

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 KAon BEam Spectrometer (“Micromegas” detector)

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 KABES: KAon BEam Spectrometer (a MICROMEGAS detector)

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 charged Ke4 decays K +/-      e  n experimental observation of quark-antiquark condensate –s-wave scattering length a 0 0 in  -scattering at low energy n earlier experiments statistically and systematically limited –Rosselet et al., 1977 –Brookhaven, 2001 neutral Ke4-decay ( K 0 L      e  ) was studied by the Vienna group (Laurenz Widhalm, Heinz Dibon)

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 SM prediction: BR(K + →  + ) = 7.1 ± 1.0 × future plans: K + →  + n so far, three events seen at BNL (E787 and E949) n decay established but not enough statistics to check Standard Model n plans to collect ~100 events at FNAL (CKM experiment): financial difficulties n idea to use CKM’s expertise and parts of the NA48 detector at CERN

Conclusion: NA48 has yielded an unexpectedly large amount of valuable results..... and may still continue to do so!

backup

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 n special interest: test of CPT invariance n if CPT is conserved –and there are no transitions to I = 3, or to nonsymmetric I = 1 states: –A 1 : I=1 amplitude –real part fixed by CPT –imaginary part sensitive to direct CP-violation n Bell-Steinberger relation –connects CPT violating phase  with  parameters via unitarity: K S   0  0  0

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 K S   0  0  0 : the approach time evolution of K L,S   0  0  0 I  0 (t) ~ e -  L t + K L decay “dilution” D is momentum dependent n look for interference term |  000 | 2 e -  S t + K S decay 2 D(p) (Re (  000 ) cos  mt – Im (  000 ) sin  mt) e -(  S +  L )t / 2 K L – K S interference term

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 NA48/1: preliminary result for  000

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004

CP-violation: indirect / direct ? CP-violation first seen in K L   decays (1964) n K L and K S are mixtures of CP-eigenstates K 1 and K 2 –K L = K 2 +  K 1 –K S = K 1 +  K 2 n mixing responsible for most of the observed CP-violation –parameter  –known since long ago –see Michele Veltri’s talk for new measurement by NA48 n but longstanding question: is there “direct” CP-violation? –K 2   ?? –parameter  ’ n small effect  need high-precision measurement !

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 the NA48 approach to measuring Re  ’/  n almost collinear neutral kaon beams (K L and K S ) n same decay volume n  take all 4 modes at same time and place ! n “weighting” of K L decay events with K S lifetime –eliminate acceptance effects in first order –reduce systematic effects at expense of statistics n distinguish K L and K S by “tagging” protons to “K S target” n “second experiment” in 2001 –new drift chambers –different spill structure and instantaneous beam intensity –different beam energy

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 rare decays at NA48 n “K L ”-beam: –K L   +  - e + e - indirect CP-violation –K L   +/- e -/+  0  form factors,  – phase shifts, chiral perturbation theory –K L   0  CP-conserving contribution in K L  e + e -  0 –K L  e + e -  form factors –K L  e + e -  background for K L  e + e -  0 –K L  e + e - e + e - CP-eigenvalue of K L n “K S ”-beam:  0   0  0 mass  0   non-leptonic weak interaction  0   0   0    p  -  transversal  -polarization

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 K S / K L   0  0  0 interference dependence of interference on   (phase of   )

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004

Dalitz decays:  0  e + e - K S   0 e + e -

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004

Kl3 decays and V us n test of CKM unitarity –|V ud | 2 + |V us | 2 + |V ub | 2 =  : deviation from unity –|V us | contributes nearly 30% of uncertainty |V us | calculated from  (Ke3) and  (K  3) –K    0 e   and K    0   –precise measurement will improve CKM unitarity test

Manfred Jeitler, Institute of High Energy Physics, Vienna: The NA48 experiment Innsbruck, 26 March 2004 charged kaon decays: the NA48 approach n cancellation of systematic effects is essential n adapt NA48’s proven concept: simultaneous, collinear beams n use same detector without major modifications n beam particles are charged  measure their momentum !