1. 25/5/2007Giuseppe Ruggiero, Kaon 20071 The K +  + experiment at CERN Giuseppe Ruggiero SNS & INFN, Pisa “Kaon 2007” Frascati, 25/05/2007

2. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 2 The K  decays: a theoretical clean environment sensitive to new physics FCNC loop processes: s  d coupling and highest CKM suppression Very clean theoretically: SD contributions dominate, hadronic matrix element can be related to measured quantites. SM predictions (uncertainties from CKM elements): 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 Sensitive to NP: clean probe up to  ~100 TeV scale

3. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 3 Effects of new physics on K  decays F. Mescia CKM 2006

4. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 4 Setting the bar for future K  experiments P326 100 events Mean: E787/949 E787/949 BR(K +   ) = 1.47 ×10  10 +1.30 -0.89 SM F. Mescia CKM 2006

5. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 5 Proposal to Measure the Rare Decay K    at the CERN SPS (P326) CERN, Dubna, Ferrara, Florence, Frascati, Mainz, Merced, Moscow, Naples, Perugia, Protvino, Pisa, Rome, Saclay, San Luis Potosi, Sofia, Triumf, Turin CERN-SPSC-2005-013 SPSC-P-326 September 2005: presented at CERN SPSC December 2005: R&D endorsed by CERN Research Board Start of the Gigatracker project Start of test beams at CERN in 2006 2007: prototypes construction and test beams at CERN and Frascati 2008 – 2010: Technical design and construction Start of data taking 2011 Schedule Located in the same hall of NA48

6. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 6 NA48/3 guidance principles O (100) K +  +  events ~ 10% background 2 Enemies 1) Physics: BR(SM) = 8×10 -11 Acceptance 10% K decays ~10 13 Kaon decay in flight technique Intense proton beam from SPS High energy K (P K = 75 GeV/c)  Kaon ID Kinematical rejection Veto and particle ID Kaon 3-momentum: beam tracker Pion 3-momentum: spectrometer  /  detection: calorimeters Charged veto: spectrometer  /  /e separation: RICH 2) Budget: … Use as much as possible the existing infrastructures  NA48 Be pragmatic KK K+K+  m 2 miss =(P K  P  ) 2

7. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 7 Kinematics and Backgrounds 92% of total background Allows us to define a signal region K +   +  0 forces us to split it into two parts (Region I and Region II) Span across the signal region Rejection must rely on veotes Kinematically constrainedNot kinematically constrained 8% of total background

8. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 8 The experimental layout ++ 10 -6 mbar

9. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 9 The Beam p DECAY VOLUME VOLUME (~100 m) K+ decay rate: ~11 MHz P proton = 400 GeV/c Proton/pulse 3.3×10 12 (×3.3 NA48/2) Duty cycle 4.8/16.8 s Primary beam P Kaon = 75 GeV/c (  P/P = 1.1%) Fraction of Kaons ~ 6.6% Negligible amount of e + Beam acceptance = 12  str (×25 NA48/2) Area @ beam tracker = 58×24 mm 2 Integrated average rate = 760 MHz Kaon decays / year = 4.8 × 10 12 Secondary beam Vertical view

10. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 10 The tracking system 6 chambers with 4 double layers of straw tubes each Low X/X 0 not to spoil the beam Good space resolution not to spoil the downstream tracker resolution 200 Si  m sensor + 100 Si  m chip 300×300  m pixels  (P K )/P K ~ 0.22%  (  K ) ~ 16  rad ( ( Excellent time resolution needed for K+/  + association:  (t)~200 ps per station Readout chip bump-bonded on the sensor (0.13  m technology) Low X/X 0 Good space resolution Redundant p measurement Veto for charged particles 130  m per hit 2 magnets The Gigatracker (i.e. the beam tracker) The Double Spectrometer (i.e. the downstream tracker) Rate: 760 MHz (charged particles) ~50MHz/cm 2 Rate: ~ 45 KHz per tube (max 0.8 MHz) In vacuum, X/X 0 ~0.1% per view 5 cm radius beam hole displaced in the bending plane 8.8 m 7.2 m 2.1 m 3 Si pixel stations across the 2 nd achromat: size 60 × 27 mm 2

11. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 11 The particle ID system CEDAR: existing Cerenkov counter at CERN to places on the beam Tag the kaon to keep the beam background under control Minimal material budget Good time resolution H 2 instead of Ne New phototubes 18 m long tube (2.5 m diamater) filled with Ne @ 1 atm, 17 focal lentgh mirrors >3  pion/muon separation @ 35 GeV/c (13 GeV/c threshold for  ) Time resolution 100 ps (track timing) Velocity spectrometer (redundancy) High granularity (2000 PMTs) Small pixel size (18 mm PMT) Phototubes with very good  (t) The CEDAR (i.e. the kaon ID) The RICH (i.e. the pion ID)

12. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 12 The Veto system Large angle (10, 50 mrad): Rings calorimeters (in vacuum) Rate: ~4.5 MHz (  ) + ~0.5 MHz (  ) (OR 12) 10 -4 inefficiency for E  in 0.05,1 GeV 10 -5 inefficiency for E  >1 GeV 20 X/X 0 Lead scintillator tiles or Lead scintillator fibers (KLOE-like) Medium angle (1, 10 mrad): LKr calorimeter Rate: ~8.7 MHz (  )+~4 MHz (  ) )+~3 MHz (  ) 10 -4 inefficiency for E  in 1,5 GeV 10 -5 inefficiency for E  >5 GeV Small angle (<1 mrad): Shashlik technology Rate: 0.5 MHz (  ) 10 -5 inefficiency (high energy photons) New Readout Extruded scintillator – lead sampling calorimeter 6 m long + magnet for beam deflection Rate: ~7 MHz (  )+~3 MHz (  ) 10 -5 inefficiency for  detection Deviate the beam out from the SAC em/hadronic cluster separation. Sensitivity to the MIP 5Tm B field in a 30×20cm 2 beam hole Photon vetoes Muon veto

13. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 13 Preliminary sensitivity studies Acceptance (60 m fiducial volume) : Region I: 4% Region II: 13% Total: 17% To be reduced because of losses due dead time, reconstruction inefficiencies… Simulation of the P-326 apparatus Acceptance ~ 10% is achievable Region I and II Momentum range: 15 < P  < 35 GeV/c Against muons RICH operational reasons Plenty of energy in photon vetoes

14. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 14 Analysis: background rejection Events/yearTotalRegion IRegion II Signal (acc=17%) 651649 K++0K++0 2.71.71.0 K +  + 1.21.1<0.1 K +  e +  +   ~2negligible~2 Other 3 – track decays ~1negligible~1 K++0K++0 1.3negligible1.3 K++K++ 0.50.2 K +  e + (  + )  0, others negligible  Total bckg.93.06 S/B ~ 8 (Region I ~5, Region II ~9)

15. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 15

16. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 16 Gigatracker: R&D program Readout chip: 1st MPW submission in 0.13  m Submitted in February 07 Analogue FE blocks for the "CFD" option (Torino ) FE amplifier discriminator NINO, LVDS driver (CERN) Wafers delivery ≈ end May 07 ASICs characterization (t resolution, jitter, time walk) Tests card in progress (results by September) Si diode irradiation tests Prototype wafers (200µm thick) produced by itc-IRST using ALICE pixel layout 3 mm × 3 mm and 7 mm × 7 mm test-diodes Test diodes irradiated with n and p (Ljubljana, CERN) Fluences: 1E12 to 2E14 1MeV n cm -2 (range P326) Pre and post irradiation measurements (annealing) to study diode characteristics Irradiated test diode itc-IRST wafer, 200µm Si diode characterization with pulsed IR laser system Towards a Technical Proposal

17. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 17 Spectrometer: R&D program Chosen technology: tube of mylar (25  m, D=1 cm, L=2.1 m) 100 straws produced in Dubna Tests on gas leakage Tests on tube expansion in vacuum Prototype assembled & cosmic ray tests October 2007: Prototype integration in NA48 set-up and test on beam

18. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 18 CEDAR: R&D program CEDAR W-type filled with Ne tested at CERN in November 2006, using a 100 GeV hadron beam with 10 5 – 10 7 ppp (CERN, Firenze, Perugia). Test of fast photomultipliers using Cerenkov light. CEDAR upgrade program pion kaon proton

19. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 19 RICH: R&D program Design, construction and test of a RICH prototype (CERN, Firenze, Perugia) Full length prototype (17 m, 0.6 m diamater, stainless steel tube at CERN) Mirror built, delivered and under test in Firenze Endcap with 96 Hamatsu PMs readout through Winston’s cones PMs tested at SPS (2006) and Firenze (with laser) Measured FWHM per single  per phototube: 390ps (150 ps electronics and 110 ps laser included) pK+pK+ Simulation FWHM 0.375 ps t ns November 2007: prototype integration in the NA48 set up and test with beam

20. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 20 Large angle photon vetoes: R&D program KLOE-type lead/scintillating fiber: prototype constructed in Frascati 1 mm diameter scintillating fibers, 0.5 mm thick lead foils. Readout granularity: 18 cells Very well known and tested technology Under test at the Frascati BTF 16.8 cm8.2 cm All fiber: 8 X 0 Fibers+lead wires: 9 X 0 Studies of the efficiency of detectors built with this technology available Fermilab prototype under test at BTF  Outgassing tests performed at CERN on detectors built with same technology: they can be placed in the vacuum of the decay region (10 -6 mbar) Lead scintillators tiles Aijimura et al. NIM in press

21. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 21 Large angle photon vetoes: R&D program eeee  Test beam activity at BTF in Frascati (Frascati, Napoli, Pisa, Roma) e - beam (300-500 MeV/c) Both calorimeter prototypes under test 1 st step: test with electrons 2 nd step: test with photons Test beam periods in March, April, June 2007 Work carried on up to now using electrons: Understanding the beam background Calibration of the prototypes First data analysis (efficiency, energy and time resolution)

22. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 22 Measurement of the inefficiency K+ data taken in a dedicated NA48 test run in 2004 using K +  +  0 LKr calorimeter: R&D program Tagged  using an SPS electron beam (2006) Inefficiency measured for E  > 2.5 GeV > 10 GeV,  < 10 -5 confirmed < 10 GeV analysis in progress Consolidation of the readout Custom boards (FPGA based) sending data directly to PC Farm Test of the new electronics in 2007 NA48 run  10 GeV) electron  Energy deposition in LKr X LKr cm Energy GeV z x vacuum e beam 25 GeV/c Bremsstrahlung Kevlar window Drift chambers Magnet LKr  e- He

23. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 23 Trigger LevelL0 “hardware”L1-L2 “software” Input~10 MHz1 MHz Output1 MHz O (KHz) ImplementationDedicated hardwareTDAQ farm ActionsRICH minimum multiplicity, Muon vetoing, LKr vetoing L1 = single sub-detectors L2 = whole event Main work on possible solutions for the L0 hardware TELL-1 board (LHCb) based implementation for all non FADC sub detectors Design of a new 100 ps TDC daughter-card (RICH, Straws, MAMUD,…) Two prototypes under study (Mainz and Pisa) A possible scheme:

24. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 24 Other physics opportunities P-326 Kaon Flux ~100 times NA48/2 Kaon Flux Other physics opportunities can be addressed: Lepton – flavor violation: K e2 /K  2,K +  +  + e -, K +  -  + e + Tests of CPT K +  +  - e + Search for new low mass particles: K +    (light RH neutrinos) K +  +  0 P (pseudoscalar sGoldstino) Hadron spetroscopy …

25. 25/5/2007 Giuseppe Ruggiero, Kaon 2007 25 Conclusions Near future: Search for new physics using rare Kaon decays. P-326 experiment: Measurement of the Br(K +  + ) with a ~10% accuracy (+ other physics opportunities) General design: Mostly defined. Overall simulation and performances under review. R&D program: Well advanced: construction of detector prototypes and test in progress (in some cases completed). Important results by the end of 2007. We propose a new experiment able to reach a ~10 -12 sensitivity per event at an existing machine and employing the infrastructures of an existing experiment. [CERN-SPSC-P-326, 11/06/2005]