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Physics Introduction Rare Kaon Decays in the SM…. …and Beyond

A proposal to Study Rare Kaon Decays at the CERN SPS Augusto Ceccucci/CERN. 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

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Physics Introduction Rare Kaon Decays in the SM…. …and Beyond

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  1. A proposal to Study Rare Kaon Decays at the CERN SPS Augusto Ceccucci/CERN • 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 Lausanne

  2. Quark Mixing and CP-Violation • Cabibbo-Kobayashi-Maskawa (CKM) matrix: • Non-diagonal (e.g. Vus≠0) •  Flavour Violation • 3 or more quark generations •  CP-Violation in SM (KM) Ng=2 Nphase=0  No CP-Violation Ng=3 Nphase=1  CP-Violation Possible GIM mechanism  No FCNC at tree level Violation at one loop depending on quark masses and CKM couplings e.g., Im lt= Im Vts*Vtd ≠ 0  CPV Lausanne

  3. 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”: VudVub*+VcdVcb*+VtdVtb*=0 It is customary to employ the Wolfenstein parameterization: Vus ~lVcb ~ l2 A Vub ~ l3 A(r- ih) Vtd ~ l3 A(1-r- ih) Sensitive to |Vtd| Im lt = A2l5h Re lt = A2l5r Lausanne

  4. Status of Unitarity Triangle • 95% confidence regions extracted using| Vub|/| Vcb|, εK, ΔmBd, ΔmBs and sin2β ρ = 0.214 ± 0.047 η = 0.343 ± 0.028 • Constraints from | Vub|/| Vcb|, ΔmBd and ΔmBs compared with constraints from CP violating quantities in the kaon (εK) 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 Lausanne

  5. The four golden modes of Kaon Physics • 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 Adapted from G. Isidori @ Flavour in the LHC era, 5-7 Nov 05, CERN Lausanne

  6. K→pnn : Theory in Standard Model charm contribution top contributions The Hadronic Matrix Element is measured and isospin rotated Lausanne

  7. 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. Nierstehep-ph/0508165) • Standard Model predictions • BR(K+p+nn)  (1.6×10-5)|Vcb|4[sh2+(rc-r)2]  (8.0 ± 1.1)×10-11 • BR(KLp0nn)  (7.6×10-5)|Vcb|4h2  (3.0 ± 0.6)×10-11 The errors are mostly due to the uncertainty of the CKM parameters and not to the hadronic uncertainties Lausanne

  8. Theory vs. Experiment Adapted from U. Haisch @ Flavour in the LHC era, 6-8 Feb 06, CERN Lausanne

  9. Intrinsic theory error Combining information from BR(K+→p+nn) and BR(K0→p0nn) one obtains: (Buras et al. hep-ph/0508165) So for a 10% uncertainty on Pc, one can extract, in priciple, a 3.4%exp. determination of sin2b from kaon decays. It is currently 4.6% from B decays Lausanne

  10. 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 Lausanne

  11. MFV: Sensitivity to Z0 Penguinfrom Bobeth et a. (2005) Lausanne

  12. Generic MSSM Enhanced EW Penguins New Sources of Flavour Symmetry Breaking Lausanne

  13. Experimental State-of-the-art Lausanne

  14. K+→p+nn hep-ex/0403036 PRL93 (2004) AGS Stopped K+ ~0.1 % acceptance • BR(K+→ p+ nn ) = 1.47+1.30-0.89 × 10-10 • Compatible with SM within errors Lausanne

  15. Setting the bar for the next generation of K+→p+nn experiments E787/E949: BR(K+→ p+ nn ) = 1.47+1.30-0.89 × 10-10 Current constraint on r,hplane ? 100 events Mean=SM 100 events Mean=E787/949 Lausanne

  16. K0Lp0nn :E391a Upper Limit • 10% of RUN I • Pencil beam • Expected background • from K0Ldecays: 0.02 • Acceptance: 0.73% • BR(K0Lp0nn)<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 Lausanne

  17. K0S,L→p0 e+e-and K0S,L→p0m+m- BR(KS→p0ee)  10-9 = 5.8 +2.8-2.3(stat) ± 0.8(syst) PLB 576 (2003) BR(KS→p0mm)  10-9 = 2.9 +1.4-1.2(stat) ± 0.2(syst) PLB 599 (2004) KS→p0mm NA48/1 NA48/1 6 events, expected back. 0.22 7 events, expected back. 0.15 BR(KL→ p0 ee ) < 2.8 × 10-10 @90%CL KTeV PRL93, 021805 (2004) BR(KL→ p0 mm ) < 3.8 × 10-10 @90%CL KTeV PRL86, 5425 (2001) Lausanne

  18. K0L→p0ee (mm) in SM With the KS measurements, the KLBR can be predicted * Interference between short- and long-distance physics* (Isidori, Unterdorfer, Smith, EPJC36 (2004)) Constructivenow favored by two independent analyses* 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 * Lausanne

  19. Summary • K+p+nn • 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 • K0Lp0nn • 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 • K0Lp0ee(mm) • Long distance contributions under good control • Measurement of KSmodes has allowed SM prediction • KS rates to be better measured • Background limited (study time dep. Interference?) • 100-fold increase in kaon flux to be envisaged Lausanne

  20. CERN-SPSC-2005-013 SPSC-P-326 Proposal to Measure the Rare Decay K+p+ n n at the CERN SPS CERN, Dubna, Ferrara, Florence, Frascati, Mainz, Merced, Moscow, Naples, Perugia, Protvino, Pisa, Rome, Saclay, San Luis Potosi, Sofia, Turin Lausanne

  21. NA48: ’/ 1997 ’/ 1998 ’/ 1999 no spectrometer 2000 KL NA48/1 KS ’/lower inst. intensity 2001 2002 NA48/1: KS 2003 NA48/2: K NA48@CERN Direct CP-Violation established 1996 Re e’/e = 14.7 ± 2.2 10-4 Ave: Re e’/e = 16.7 ± 2.3 10-4 + KLRare Decays First observation of K0S→p0 e+e-and K0S→p0m+m- • Search for Direct CP-Violation • in charged kaon decays • pp scattering: PLB 633 (2006) • (a0-a2)m+= 0.268 +/- 0.017 NA48/2: K 2004 Lausanne

  22. 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 Lausanne

  23. Background rejection • Guidance: S/B = 10~10-12 rejection 1) Kinematical Rejection 2) Photon vetoes and PID (p-m) Basic idea to reject K+ p+p0 P(K+)= 75 GeV/c Require P(p+) < 35 GeV/c P(p0) > 40GeV/c It cannot be missed in the calorimeter/photon veto Lausanne

  24. Backgrounds kinematically constrained Allows us to define the signal region 92% of K+ decays K+p+p0forces us to split it into two parts • Region I: 0 < m2miss < 0.01 GeV2/c4 • Region II: 0.026 < m2miss < 0.068 GeV2/c4 Lausanne

  25. Backgrounds not kinematically constrained They span accross the signal regions Must rely on Particle ID and veto 8% of K+ decays Lausanne

  26. P-326 Detector Layout K+p+ n n Gigatracker p+ K+ ~11 MHz n 75 GeV/c 800 MHz beam p/K/p n (KABES) Lausanne

  27. P-326 Detector Layout K+p+p0 Gigatracker p+ g K+ ~11 MHz g 75 GeV/c 800 MHz beam p/K/p (KABES) Lausanne

  28. Signal & backgrounds from K decays / year 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=10-10to account for some reconstruction and deadtime losses Lausanne

  30. New high-intensity K+ beam for P-326 Already Available Lausanne

  31. 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 existingdecay tankcan be used Lausanne

  32. qp PK Pp qK Gigatracker 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) • Two Silicon micro-pixel detectors (SPIBES) • Timing • Pattern Recognition • FTPC (Improved KABES) • To minimise scattering in the last station SPIBES: X/X0 << 1% Pixel size ~ 300 x 300 mm s(p)/p ~ 0.4% excellent time resolution to select the right kaon track Dependence of the signal to background (from K+p+p0) ratio as a function of the gigatracker time resolution Lausanne 32

  33. y 2mm/bin x 2mm/bin Station 1(pixels) 2(pixels) 3(FTPC) SPIBES (Hybrid Pixel) G. Anelli, M. Scarpa, S. Tiuraniemi • 200 mm Silicon sensor (>11 000 e/h mip) • Following Alice SPD • Bump-bonding • Read-out chip • Pixel 300 mm x 300 mm • Thinned down to ~100 mm (Alice SPD 150 mm) • Beam surface ~ 14 cm2 • Adapted to the size of the SPIBES r-o chips • ~125 mm Cfibre for cooling & support Front End and R/O considerations based on the experience of the CERN-PH/MIC and PH/ED Groups with the ALICE SPD Lausanne MeV

  34. KABES principle: TPC + micromegas Tdrift2 Micromegas Gap 25 μm Micromegas Gap 25 μm Tdrift1 FTPC (KABES) 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 Lausanne

  35. Straw Tracker 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% X0 per view) but no previous large straw system has been operated in high vacuum Lausanne

  36. 12.5 m 0.2 m Al Glue – 5m 9.6 mm 25 m Gold plated Tungsten wire 30 m 2300 mm 3 coordinates 4 coordinates 2 coordinates 1 coordinate 5.4 m 5.4 m 10 cm 186.3 m from T0 8.8 m 7.2 m 7.2 m Straw Elements and Design 12 ns rise time 100 ns total width Polycarbonate spacer, 25 mg Two double layers form a view Gas mixture: 20%Ar+80%CO2 To fit easily into decay volume an octagonal shape is proposed k12hika+ (Niels)  About 2000 * 6 -> 12000 straws in total Lausanne

  37. RICH Layout Lausanne

  38. RICH as velocity spectrometer…. Resolution of a 17m P-326 RICH (CKMGEANT) Lausanne

  39. …and RICH for p-m separation Lausanne

  40. Energy of photons from K+ p+p0 hitting LKr: > 1 GeV GeV NA48 LKr as Photon Veto Consolidation of the safety/control system and read-out under way Lausanne

  41. Photon E=11 GeV Pion P=42 GeV/c Cluster not reconstructed Eg = 22 GeV Expected position LKr efficiency measured with data K+p+ p0 collected by NA48 in 2004 Events are kinematically selected. p+ track and lower energy g are use to predict the position of the other g K+p+p0p0 Lausanne

  42. Example: “hadronic” cluster of a photon Expected energy: ~29 GeV Deposited energy: ~9 GeV Maximum energy ~300 MeV Expected g position • Measured LKr inefficiency per photon (Eg > 10 GeV): • h = (2.8 ± 1.1stat ± 2.3syst) × 10-5 (preliminary) Lausanne

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

  44. 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 Lausanne

  45. MAMUD • To provide pion/muon separation and beam sweeping. • Iron is subdivided in 150 2 cm thick plates (260  260 cm2 ) • 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 Pole gap is 2 x 11 cm V x 30 cm H Coils cross section 10 cm x 20cm Lausanne

  46. 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 Lausanne

  47. Other Physics Opportunities • The situation is similar to NA48, which was designed to measure “only” e’/e but produced many more measurements • Accumulating ~100 times the flux of NA48/2 will allow us to address, for instance: • Cusp like effects (p-p scattering) • K+ p0 p0 e+n • Lepton Flavour Violation K+ p+ m+ e- , K+p- m+ e+, (Ke2/Km2) • Search for new low mass particles • K+ p+ X • K+p+ p0 P (pseudoscalar sGoldstino) • Study rare p+ & p0 decays • Improve greatly on rare radiative kaon decays • Compare K+ and K- (alternating beam polarity) • K+/- p+/-p0g(CPV interference) • T-odd Correlations in Kl4 • And possibly, given the quality of the detector, topics in hadron spectroscopy Lausanne

  48. 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 e’/e  NA48/1 KS rare decays  NA48/2 Dg/g in K  3p P-326 K+p+nn • 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! Lausanne

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