1. February 27, 2006Lausanne1 Physics Introduction –Rare Kaon Decays in the SM…. –…and Beyond Flavour as a probe of New Physics complementary to the high energy frontier Experimental state-of-the-art –Recent Results and world-wide perspectives Description of the CERN proposal P-326 –Technique –Status A proposal to Study Rare Kaon Decays at the CERN SPS Augusto Ceccucci/CERN

2. February 27, 2006Lausanne2 Quark Mixing and CP-Violation N g =2 N phase =0  No CP-Violation N g =3 N phase =1  CP-Violation Possible Cabibbo-Kobayashi-Maskawa (CKM) matrix: Non-diagonal (e.g. V us ≠0)  Flavour Violation 3 or more quark generations  CP-Violation in SM (KM) e.g., Im t = Im V ts *V td ≠ 0  CPV GIM mechanism  No FCNC at tree level Violation at one loop depending on quark masses and CKM couplings

3. February 27, 2006Lausanne3 CKM Unitarity and Rare Kaon Decays The unitarity of the CKM matrix can be expressed by triangles in a complex plane. There are six triangles but one is more “triangular”: V ud V ub *+V cd V cb *+V td V tb *=0 It is customary to employ the Wolfenstein parameterization: V us ~ V cb ~   V ub ~   i  V td ~   i  Sensitive to |V td | Im t =  2 5  Re t =  2 5 

4. February 27, 2006Lausanne4 Status of Unitarity Triangle 95% confidence regions extracted using| V ub |/| V cb |, ε K, Δm Bd, Δm Bs and sin2β ρ = 0.214 ± 0.047 η = 0.343 ± 0.028 Constraints from | V ub |/| V cb |, Δm Bd and Δm Bs compared with constraints from CP violating quantities in the kaon (ε K ) and in the B (sin2β) sectors ρ = 0.181 ± 0.060 η = 0.404 ± 0.035 Rare kaon decays are loop-dominated. Assuming SM they provide strong independent constraints to the UT

5. February 27, 2006Lausanne5 The four golden modes of Kaon Physics Short-distance contrib (  sd /  ) Irreducible theory err. on amplitude Total SM BR K  L    >99%1% 3  10 -11 K     88%3% 8  10 -11 KLeeKLee 38%15% 3.5  10 -11 K  L       28%30% 1.5  10 -11 Adapted from G. Isidori @ Flavour in the LHC era, 5-7 Nov 05, CERN Short distance dynamics: – W-top quark loops constitute the dominant contribution: The EW short-distance amplitude is common in the SM… …but potentially different beyond SM Important to address all these decays

6. February 27, 2006Lausanne6 K→  : Theory in Standard Model charm contribution top contributions The Hadronic Matrix Element is measured and isospin rotated

7. February 27, 2006Lausanne7 Predictions in SM This used to be the largest theoretical error (+/- 0.037). It was reduced by a NNLO calculation A. Buras, M. Gorbahn, U. Haisch, U. Nierste hep-ph/0508165) The errors are mostly due to the uncertainty of the CKM parameters and not to the hadronic uncertainties Standard Model predictions BR(K +  + )  (1.6×10 -5 )|V cb | 4 [  2 +(  c -  ) 2 ]  (8.0 ± 1.1)×10 -11 BR(K L  0 )  (7.6×10 -5 )|V cb | 4  2  ± 0.6  ×10 -11

8. February 27, 2006Lausanne8 Theory vs. Experiment SM ObservableTheoretical errorExperimental error B(K  L    ~3%?? B(K     ~6%~75% A FB (B  X s l  l  ) ~8%?? B(B  X s  ) ~10%~9% B(B  X s l  l  ) ~13%~20% A FB (B  K ( * ) l  l  ) ~15%~30% B(B  (K ( * )  )  ) ~25%~40% B(B s      ) ~30%?? B(B  K*l  l  ) ~35%~13% Adapted from U. Haisch @ Flavour in the LHC era, 6-8 Feb 06, CERN

9. February 27, 2006Lausanne9 Intrinsic theory error Combining information from BR(K  →   ) and BR(K  →   ) one obtains: (Buras et al. hep-ph/0508165) So for a 10% uncertainty on P c, one can extract, in priciple, a 3.4%  exp. determination of sin2  from kaon decays. It is currently 4.6% from B decays

10. February 27, 2006Lausanne10 Beyond Standard Model Compare two scenarios: –Minimal Flavour Violation All mixing governed by universal CKM matrix –No Extra Complex Phases Same operators as in SM Different coefficients Stringent correlation with B rare decays –New sources of Flavour Symmetry Breaking ~ TeV scale Extra phases can lead to large deviations from SM predictions, especially for the CP-Violating modes

11. February 27, 2006Lausanne11 MFV: Sensitivity to Z 0 Penguin from Bobeth et a. (2005)

12. February 27, 2006Lausanne12 New Sources of Flavour Symmetry Breaking Generic MSSM Enhanced EW Penguins

13. February 27, 2006Lausanne13 Experimental State-of-the-art

14. February 27, 2006Lausanne14 K + →  + BR(K + →  + ) = 1.47 +1.30 -0.89 × 10 -10 Compatible with SM within errors hep-ex/0403036 PRL93 (2004) Stopped K + ~0.1 % acceptance AGS

15. February 27, 2006Lausanne15 Setting the bar for the next generation of K + →  + experiments 100 events Mean=SM 100 events Mean=E787/949 Current constraint on  plane ? E787/E949: BR(K + →  + ) = 1.47 +1.30 -0.89 × 10 -10

16. February 27, 2006Lausanne16 K 0 L     E391a Upper Limit BR(K 0 L    )<2.86  10 -7 90%CL Preliminary (Ken Sakashita@KAON2005)  6 improvement over KTeV one day special run  2 improvement over published limit (KTeV Dalitz technique) For the future: JPARC LOI-05 Recently, J-PARC made a call for proposals 10% of RUN I Pencil beam Expected background from K 0 L decays: 0.02 Acceptance: 0.73%

17. February 27, 2006Lausanne17 K 0 S,L →  0 e  e  and K 0 S,L →  0     K S →  0  BR(K S →  0 ee)  10 -9 = 5.8 +2.8 -2.3 (stat) ± 0.8(syst) PLB 576 (2003) 7 events, expected back. 0.15 BR(K S →  0  )  10 -9 = 2.9 +1.4 -1.2 (stat) ± 0.2(syst) PLB 599 (2004) 6 events, expected back. 0.22 NA48/1 BR(K L →  0 ee ) < 2.8 × 10 -10 @90%CL KTeV PRL93, 021805 (2004) BR(K L →  0  ) < 3.8 × 10 -10 @90%CL KTeV PRL86, 5425 (2001)

18. February 27, 2006Lausanne18 Constructive now favored by two independent analyses* (Isidori, Unterdorfer, Smith, EPJC36 (2004)) Destructive *G. Buchalla, G. D’Ambrosio, G. Isidori, Nucl.Phys.B672,387 (2003) *S. Friot, D. Greynat, E. de Rafael, hep-ph/0404136, PL B 595 * K 0 L →  0 ee (  ) in SM With the K S measurements, the K L BR can be predicted * Interference between short- and long-distance physics*

19. February 27, 2006Lausanne19 Summary K +    –Already 3 clean events are published (E787/E949) –Experiment in agreement with SM within errors –Next round of exp. need to collect O(100) events to be useful –Move from stopped to in flight technique (FNAL Proposal turned down by P5) –Proposal for in-flight decays: CERN P-326 –Letter of Intent at J-PARC to continue the study with decays at rest K 0 L    –Large window of opportunity exists. –Upper limit is 4 order of magnitude from the SM prediction –First results E391a (proposed SES~3 10 -10 ) –LOI to continue at J-PARC –KOPIO TERMINATED K 0 L    ee(  ) –Long distance contributions under good control –Measurement of K S modes has allowed SM prediction –K S rates to be better measured –Background limited (study time dep. Interference?) –100-fold increase in kaon flux to be envisaged

20. February 27, 2006Lausanne20 Proposal to Measure the Rare Decay K     at the CERN SPS CERN, Dubna, Ferrara, Florence, Frascati, Mainz, Merced, Moscow, Naples, Perugia, Protvino, Pisa, Rome, Saclay, San Luis Potosi, Sofia, Turin CERN-SPSC-2005-013 SPSC-P-326

21. February 27, 2006Lausanne21 NA48@CERN 1997 1998 1999 2000 2001 2002 2003 NA48:  ’/   ’/   ’/  lower inst. intensity NA48/1 K S NA48/1: K S KLKL no spectrometer NA48/2: K  1996 2004 NA48/2: K  Re  ’/  = 14.7 ± 2.2  10 -4 First observation of K 0 S →  0 e  e  and K 0 S →  0     Ave: Re  ’/  = 16.7 ± 2.3  10 -4 + K L Rare Decays Search for Direct CP-Violation in charged kaon decays  scattering: PLB 633 (2006) (a 0 -a 2 )m + = 0.268 +/- 0.017 Direct CP-Violation established

22. February 27, 2006Lausanne22 Status of P-326 (a.k.a. NA48/3) Presented at the CERN SPSC in September 2005 R&D Endorsed by CERN Research Board on December 2005 (subject to funding) Beam Test foreseen in August 2006 Still seeking groups to fund the RICH counter Seeking full approval by end of 2006…. …to be able to start data taking some time in 2009-2010

23. February 27, 2006 Lausanne 23 Background rejection Guidance: S/B = 10 ~10 -12 rejection 1) Kinematical Rejection 2) Photon vetoes and PID (  ) Basic idea to reject K +  +  0 P(K  ) = 75 GeV/c Require P(   ) < 35 GeV/c P(   ) > 40  GeV/c It cannot be missed in the calorimeter/photon veto

24. February 27, 2006 Lausanne 24 Backgrounds kinematically constrained DecayBR K +    K  2 )0.634 K +  +  0 0.211 K +  +  +  - K +    0  0 0.070 92% of K + decays Allows us to define the signal region K   +  0 forces us to split it into two parts Region I: 0 < m 2 miss < 0.01 GeV 2 /c 4 Region II: 0.026 < m 2 miss < 0.068 GeV 2 /c 4

25. February 27, 2006 Lausanne 25 Backgrounds not kinematically constrained Decay BR K +  0 e + (K e3 ) 0.049 K3K3K3K3 0.033 K2K2K2K2 5.5×10 -3 +0K++0+0K++0 1.5×10 -3 K e4 4×10 -5 K4K4K4K4 1×10 -5 8% of K + decays They span accross the signal regions Must rely on Particle ID and veto

26. February 27, 2006Lausanne26 P-326 Detector Layout 75 GeV/c 800 MHz beam  /K/p K+K+ ++ ~11 MHz Gigatracker (KABES) K    

27. February 27, 2006Lausanne27 P-326 Detector Layout 75 GeV/c 800 MHz beam  /K/p K+K+ ++   ~11 MHz Gigatracker (KABES) KK

28. February 27, 2006 Lausanne 28 Signal & backgrounds from K decays / year TotalRegion IRegion II Signal651649 K++0K++0 2.7±0.21.7±0.21.0±0.1 K2K2 1.2±0.31.1±0.3<0.1 K e4 2±2negligible2±2 K   +  +   and other 3-tracks bckg. 1±1negligible1±1 22 1.3±0.4negligible1.3±0.4 K2K2 0.4±0.10.2±0.1 K e3, K  3,others negligible  Total bkg9±33.0±0.26±3

29. February 27, 2006 Lausanne 29 Summary Signal events expected per year@BR=8 10 -11 65 (16 Region I, 49 Region II) Background events ~9 (3 Region I, ~6 Region II) Signal/Background ~ 8 S/B (Region I) ~5 S/B (Region II) ~ 9 For Comparison: In the written proposal we quoted 40 events/year@BR=10 -10 to account for some reconstruction and deadtime losses

30. February 27, 2006Lausanne30 Beam: Present K12 (NA48/2) New HI K + > 2006 Factor wrt 2004 SPS protons per pulse on T101 x 10 12 3 x 10 12 3.0 Duty cycle (s./s.)4.8 / 16.8 1.0 Solid angle (  sterad)  0.40  16 40 Av. K + momentum (GeV/c)6075 K + ~ 1.5 Mom. band RMS: (  p/p in %)  4  1 ~0.25 Area at Gigatracker (cm 2 )  7.0  14  2.0 Total beam per pulse (x 10 7 ) per Effective spill length MHz MHz/cm 2 (gigatracker) 5.5 18 2.5 250 800 60 ~45 (~27) ~24(~15) Eff. running time / yr (pulses)3 x 10 5 1.0 K + decays per year1.0x10 11 4.8x10 12  48 New high-intensity K + beam for P-326 Already Available

31. February 27, 2006Lausanne31 Decay Tank Specification: 10 -6 mbar –Study performed with Monte Carlo using Fluka and Gheisha to simulate the hadronic interactions with the residual gas. Measurements: –Vacuum test performed on the existing tube of NA48. –A 10 -5 mbar level reached with only 1 pump. –With a few 50000 l/s diffusion or cryogenics pumps the requested vacuum level can be achieved Conclusions: –The existing decay tank can be used

32. February 27, 2006Lausanne32 Gigatracker 32 X/X 0 << 1% Pixel size ~ 300 x 300 mm  (p)/p ~ 0.4% excellent time resolution to select the right kaon track Provide precise measurements on all beam tracks (out of which only ~6% are K + ) Provide very good time resolution Minimise mass (multiple scattering and beam interactions) Sustain high, non-uniform rate ( 800 MHz total) PP PKPK   Two Silicon micro-pixel detectors (SPIBES) Timing Pattern Recognition FTPC (Improved KABES) To minimise scattering in the last station SPIBES: Dependence of the signal to background (from K +      ) ratio as a function of the gigatracker time resolution

33. February 27, 2006Lausanne33 SPIBES (Hybrid Pixel) 200  m Silicon sensor (>11 000 e/h mip) –Following Alice SPD –Bump-bonding Read-out chip –Pixel 300  m x 300  m –Thinned down to ~100  m (Alice SPD 150  m) Beam surface ~ 14 cm 2 –Adapted to the size of the SPIBES r-o chips ~125  m Cfibre for cooling & support y x 2mm/bin Station 1(pixels) 2(pixels) 3(FTPC) G. Anelli, M. Scarpa, S. Tiuraniemi Front End and R/O considerations based on the experience of the CERN-PH/MIC and PH/ED Groups with the ALICE SPD MeV

34. February 27, 2006Lausanne34 FTPC (KABES) T drif t1 T drift2 Micromegas Gap 25 μm Micromegas Gap 25 μm KABES principle: TPC + micromegas Pioneered in NA48/2 Tested in 2004 at high intensity with 1 GHz FADC In NA48/2 KABES has achieved: Position resolution ~ 70 micron Time resolution ~ 0.6 ns Rate per micro-strip ~ 2 MHz New electronic + 25µm mesh strip signal occupancy divided by 3

35. February 27, 2006Lausanne35 Advantages: can (in principle) operate in vacuum decay volume can be designed without internal frames and flanges can work in high rate of hits good space resolution (~130  m/hit for  9.6 straw) small amount of material (~0.1% X 0 per view) but no previous large straw system has been operated in high vacuum Straw Tracker

36. February 27, 2006Lausanne36 Glue – 5  m 12.5  m 0.2  m Al 9.6 mm25  m Gold plated Tungsten wire 30  m Straw Elements and Design 8.8 m186.3 m from T0 5.4 m 7.2 m k12hika+ (Niels)  About 2000 * 6 -> 12000 straws in total 3 coordinates 4 coordinates 2 coordinates 1 coordinate 10 cm 2300 mm To fit easily into decay volume an octagonal shape is proposed Two double layers form a viewGas mixture: 20%Ar+80%CO 2 12 ns rise time 100 ns total width Polycarbonate spacer, 25 mg

37. February 27, 2006Lausanne37 RICH Layout

38. February 27, 2006Lausanne38 RICH as velocity spectrometer…. Resolution of a 17m P-326 RICH (CKMGEANT)

39. February 27, 2006Lausanne39 …and RICH for  -  separation

40. February 27, 2006Lausanne40 NA48 LKr as Photon Veto Energy of photons from K       hitting LKr: > 1 GeV GeV Consolidation of the safety/control system and read-out under way

41. February 27, 2006Lausanne41 LKr efficiency measured with data Cluster not reconstructed E  = 22 GeV Pion P=42 GeV/c Photon E=11 GeV Expected position K +      collected by NA48 in 2004 Events are kinematically selected.   track and lower energy  are use to predict the position of the other  +00+00

42. February 27, 2006Lausanne42 Example: “hadronic” cluster of a photon Expected  position Maximum energy ~300 MeV Expected energy: ~29 GeV Deposited energy: ~9 GeV Measured LKr inefficiency per photon (E g > 10 GeV):  = (2.8 ± 1.1 stat ± 2.3 syst ) × 10 -5 (preliminary)

43. February 27, 2006Lausanne43 Beam test 2006 Idea for measuring inefficiency in the range 2 GeV < E  < 10 GeV –Use of the NA48 set-up. –Photons produced by bremsstrahlung. –SPS can provide a suitable electron beam. vacuum Electron beam (25 GeV/c) Bremsstrahlung Kevlar window Drift chambers Magnet Calorimeter  e- Calorimeter inefficiency below E  < 5 GeV is not critical Beam test foreseen during the 2006 SPS run

44. February 27, 2006Lausanne44 ANTI-Photon Rings From: Ajimura et al., NIMA 552 (2005) Two designs under test: –spaghetti (KLOE) –lead/scintillator sandwich (CKM) Extensive simulation under way A tagged photon beam is available in Frascati to test existing prototypes

45. February 27, 2006Lausanne45 MAMUD Pole gap is 2 x 11 cm V x 30 cm H Coils cross section 10 cm x 20cm To provide pion/muon separation and beam sweeping. –Iron is subdivided in 150 2 cm thick plates (260  260 cm 2 ) Two coils magnetise the iron plates to provide a 5 Tm field integral in the beam region Active detector: –Strips of extruded polystyrene scintillator (as in Opera) –Light is collected by WLS fibres with 1.2 mm diameter

46. February 27, 2006Lausanne46 Trigger & DAQ Total input to L0: 11 MHz L0 (example): – > 1 hit hodoscope  73% – muon veto  24% – Photon Veto  18% – <2 EM quadrants & E<50 GeV  3% L0 output: –3% x 11 MHz = 330 KHz Keep: L0 + Control + Calibration + Spin-offs < 1 MHz L1 in PC farm (à la LHCb) to keep as much flexibility as possible Software trigger reduction ~40 Important synergies with LHC to be exploited: for instance, the LHCb TELL1 board

47. February 27, 2006Lausanne47 Other Physics Opportunities The situation is similar to NA48, which was designed to measure “only”  ’/  but produced many more measurements Accumulating ~100 times the flux of NA48/2 will allow us to address, for instance: 1.Cusp like effects (  scattering) –K       e  2.Lepton Flavour Violation K        e , K       e +, (K e2 /K  2 ) 3.Search for new low mass particles –K      X –K       P (pseudoscalar sGoldstino) 4.Study rare     decays 5.Improve greatly on rare radiative kaon decays 6.Compare K + and K - (alternating beam polarity) –K        (CPV interference) –T-odd Correlations in K l4 7.And possibly, given the quality of the detector, topics in hadron spectroscopy

48. February 27, 2006Lausanne48 Summary Clear physics case –The discovery of New Physics will dramatically increase the motivation for searches of new flavour phenomena Healthy competition worldwide: – J-PARC   SPS Exploit synergies and existing infrastructures NA48  ’ /   NA48/1 K S rare decays  NA48/2  g/g in K  3   P-326      SPS –SPS used as LHC injector (so it will run in the future) –No flagrant time overlap with CNGS –P-326 fully compatible with the rest of CERN fixed target because P-326 needs only ~1/20 of the SPS protons Join us!