The K +   + experiment at CERN Monica Pepe INFN Perugia Europhysics Conference on High Energy Physics Manchester, England - July

HEP Monica Pepe – INFN Perugia CP Standard Model predictions BR(K +  + )  (1.6×10 -5 )|V cb | 4 [  2 +(  c -  ) 2 ]  (8.0 ± 1.1)× BR(K L  0 )  (7.6×10 -5 )|V cb | 4  2  ± 0.6  × Golden modes  FCNC loop processes  Short distance dynamics dominated  One semileptonic operator, hadronic matrix element related to measured quantities K + →    : decisive test of SM sensitive to new physics Present measurement (E787/949): BR(K +   ) = 1.47 × 10  10 (3 events)

HEP Monica Pepe – INFN Perugia CERN-SPSC SPSC-P-326 September 2005: presented at CERN SPSC December 2005: R&D endorsed by CERN Research Board Start of test beams at CERN in : 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 as NA48 CERN, Dubna, Ferrara, Firenze, Frascati, Mainz, Merced, Moscow, Napoli, Perugia, Pisa, Protvino, Roma, Saclay, San Luis Potosi, Sofia, Torino, Triumf P326 a 10% new measurement (100 events)  Proposal to Measure the Rare Decay K    at the CERN SPS

HEP Monica Pepe – INFN Perugia O (100) K +  +  events ~ 10% background Kaon decay in flight technique Intense proton beam from SPS High energy K (P K = 75 GeV/c)  Kaon ID (CEDAR)  Kinematical rejection Kaon 3-momentum: beam tracker Pion 3-momentum: spectrometer KK K+K+  m 2 miss =(P K  P  ) 2 P326 guidance principles  Veto and particle ID  /  detection: calorimeters Charged veto: spectrometer  /  /e separation: RICH  BR(SM) = 8×  Acceptance 10%  ~ K + decays in 2 years

HEP Monica Pepe – INFN Perugia 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 vetoes Kinematically constrained Not kinematically constrained 8% of total background Kinematics and Backgrounds

HEP Monica Pepe – INFN Perugia Background Rejection K + →   (K  )  Largest BR: 63.4%  Need ~ rejection factor Kinematics: Muon Veto: MAMUD Particle ID: 5×10 -3  RICH K + →     ( K  )  2nd Largest BR: 20.9%  Need ~ rejection factor Kinematics: 5×10 -3 Photon Veto: per photon Large angle: 13 ANTIs (10 < acceptance < 50 mrad) Medium angle: NA48 LKr (1 < acceptance < 10 mrad) Small angle: IRC1,2 SAC (acceptance < 1 mrad) Assuming the above veto inefficiencies and an acceptance of 10%, a S/B > 10 is obtained if (  m miss ) 2 ~ 8×10 -3  GeV 2 /c 4 Resolution requirements: P     < 1 % P K  0.3 %  K   μrad

HEP Monica Pepe – INFN Perugia P Kaon = 75 GeV/c (  P/P ~ 1.1%) Fraction of K + ~ 6.6% Negligible amount of e + Beam acceptance = 12  str (×25 NA48/2) beam tracker = 58×24 mm 2 Integrated average rate = 760 MHz K + decays / year = 4.8 × P proton = 400 GeV/c Proton/pulse 3.3×10 12 (×3.3 NA48/2) Duty cycle 4.8/16.8 s Primary beam Secondary beam The Beam Vertical view DECAY VOLUME VOLUME (~100 m) K+ decay rate: ~11 MHz p Achromat 1 Quadrupoles Radiator Achromat 2 Cedar Scraper Gigatracker 20 mm 5 m Target

HEP Monica Pepe – INFN Perugia The P326 layout ++ VACUUM mbar 50 MHz 800 MHz11 MHz K + ~ 75 GeV Technical Design Report in preparation

HEP Monica Pepe – INFN Perugia 6 chambers with 4 double layers of straw tubes each (  9.6 mm) The Gigatracker (i.e. the beam spectrometer) The Double Spectrometer (i.e. the downstream tracker) 3 Si pixel stations across the 2 nd achromat: (60 × 27 mm 2 ) The tracking system  Rate: ~ 45 KHz per tube (max 0.8 MHz beam halo)  Low X/X 0 0.1% X 0 per view in vacuum  Good hit space resolution 130  m per view  Redundant p measurement 2 magnets (270 and 360 MeV/c pt kick)  Veto for charged particles 5cm radius beam hole displaced in the bending plane according to beam path m 2 miss resolution ~ 1.1×10  3 GeV 2 /c 4 main contribution from θ  K measurement θKθK pp pKpK θKθK θθ m 2 miss resolution 8.8 m 7.2 m 2.1 m Time resolution (ps) Signal/Background  (P K )/P K ~ 0.22%  (  K ) ~ 16  rad ( (  Rate 760 MHz (charged particles) ~ 60 MHz / cm 2  300×300  m 2 pixels  200 Si  m sensor Si  m chip Low X/X 0  Readout chip bump-bonded on the sensor (0.13  m technology) Excellent time resolution needed for K + /  + association  (t)~200 ps / station

HEP Monica Pepe – INFN Perugia CEDAR: existing Cerenkov counter at CERN 18 m long tube (  2.5 m ), 17 focal lentgh mirrors The CEDAR (i.e. the kaon ID) The RICH (i.e. the pion ID )  Adapted to P326 need:  Vary gas pressure and diaphragm aperture to select Kaons H 2 instead of Nitrogen New PMs and electronics  1 atm (  thr = 13 GeV/c)  >3   /  separation up to 35 GeV/c  High granularity (2000 PMTs)  Small pixel size (18 mm PMT)  Disentangle pileup in Gigatracker  (t)~100 ps PMTs tested in 2006 Prototype Test Beam in 2007 p K  Beam composition 2006 Test The particle ID system

HEP Monica Pepe – INFN Perugia Large angle (10-50 mrad): 13 ANTIS Two options under test: Lead-scintillator tiles or Lead-scintillator fibers (KLOE-like) Photon vetoes Muon veto MAMUD The Veto system Rings calorimeters (in vacuum) Rate: ~ 4.5 MHz (  ) + ~ 0.5 MHz (  ) (OR 12) inefficiency for 0.05 < E  < 1 GeV inefficiency for E  > 1 GeV Medium angle (1-10 mrad): NA48 LKr Calorimeter New Readout Rate: ~ 8.7 MHz (  ) + ~ 4 MHz (  ) + ~ 4 MHz (  ) inefficiency for 1 < E  < 5 GeV inefficiency for E  > 1 GeV Inefficiency for E  > 10 GeV tested on NA48/2 data ( K + →     ) Small angle (< 1 mrad): Shashlik technology Rate: ~ 0.5 MHz (  ) inefficiency for high energy (>10GeV) photons Sampling calorimeter + Magnet for beam deflection Rate: ~ 7 MHz (  ) + ~ 3 MHz (  ) inefficiency for  detection Sensitivity to the MIP em/hadronic cluster separation 5Tm B field in a 30×20cm 2 beam hole: deviate the beam out from the SAC The NA48 LKr calorimeter ANTI ring Shashlik calorimeter

HEP Monica Pepe – INFN Perugia  A possible scheme: TRIGGER LevelL0 “hardware”L1-L2 “software” Input~10 MHz1 MHz Output1 MHz O (KHz) ImplementationDedicated hardwareTDAQ farm ActionsRICH 1Track, μ veto, LKr (  ) veto L1 = single sub-detectors L2 = whole event  Software trigger reduction ~ 40

HEP Monica Pepe – INFN Perugia Acceptance (60 m fiducial volume):  Region I: 4%  Region II: 13%  Total: 17% could be reduced after analysis cuts (losses due dead time, reconstruction inefficiencies…) Simulation of the P-326 apparatus Acceptance ~ 10% is achievable Preliminary sensitivity studies Region I and II Momentum range: 15 < P  < 35 GeV/c  Against muons  RICH operational reasons  Plenty of energy in photon vetoes Remind: K  m 2 miss = GeV 2 /c 4 K  m 2 miss < 0 0 < m 2 miss < < m 2 miss < GeV 2 /c 4

HEP Monica Pepe – INFN Perugia Events/yearTotalRegion IRegion II Signal (acc=17%) K++0K++ K +  <0.1 K +  e +  +   ~2negligible~2 Other 3 – track decays ~1negligible~1 K++0K++0 1.3negligible1.3 K++K++ K +  e + (  + )  0, others negligible  Total bckg  S/B ~ 8 (Region I ~5, Region II ~9) Signal and Backgrounds

HEP Monica Pepe – INFN Perugia Conclusions  P326 experiment: Search for new physics using rare Kaon decays  A new experiment (~ sensitivity per event) at an existing machine and employing the infrastructures of an existing experiment  General design mostly defined. Overall simulation and performance under review  R&D program: construction of detector prototypes and test in progress. Important results by end of 2007  P-326 proposed for K +  + but Kaon Flux ~100 times wrt NA48/2 many other physics opportunities can be addressed

HEP Monica Pepe – INFN Perugia Back-up Slides

HEP Monica Pepe – INFN Perugia Irradiated test diode itc-IRST wafer, 200µm 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 (started in 2006) 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 Si diode characterization with pulsed IR laser system Towards a Technical Proposal

HEP Monica Pepe – INFN Perugia 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 Spectrometer: R&D program

HEP Monica Pepe – INFN Perugia CEDAR W-type filled with N tested at CERN in November 2006, using a 100 GeV hadron beam with 10 5 – 10 7 ppp (CERN, Firenze, Perugia) Test in 2006 mainly devoted to study time capability Test of fast photomultipliers using Cerenkov light. CEDAR upgrade program CEDAR: R&D program

HEP Monica Pepe – INFN Perugia pK+pK+ Simulation FWHM ps t ns November 2007: prototype integration in the NA48 set up and test with beam RICH: R&D program 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/Perugia (with laser) – Hamamatsu R7400-U Measured FWHM per single  per phototube 380ps (150 ps electronics and 110 ps laser included) PM size is the main limitation to Cerenkov angle resolution Design, construction and test of a RICH prototype (CERN, Firenze, Perugia)

HEP Monica Pepe – INFN Perugia October 2006 test: Tagged photon beam Using the existing NA48 setup vacuum Electron beam (25 GeV/c) Bremsstrahlung Kevlar window Drift chambers Magnet Calorimeter  e- X LKr cm  Energy deposition in LKrelectron Energy GeV 2×10 8 electrons collected 10  ineff.sensitivity below 10 GeV Liquid Kripton Calorimeter Consolidation of the readout Custom boards (FPGA based) sending data directly to PC Farm Test of the new electronics in 2007 NA48 run

HEP Monica Pepe – INFN Perugia KLOE-type lead/scintillating fiber: prototype built 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 e-beam 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 Large angle photon vetoes: R&D program (1) Lead glass counters from OPAL e.m. calo a possible alternative under study (counters in vacuum and PMs outside)

HEP Monica Pepe – INFN Perugia eeee  Test beam activity at BTF in Frascati (Frascati, Napoli, Pisa, Roma) e - beam ( 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) Large angle photon vetoes: R&D program (2)

HEP Monica Pepe – INFN Perugia MAgnetized MUon Detector Sampling calorimeter (Fe-Sci 20X 0, 2λ 0 ) + Magnet for beam deflection Em/hadronic clusters separation Sensitivity to MIP 10   detection inefficiency Muon Veto: MAMUD

HEP Monica Pepe – INFN Perugia 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: TRIGGER 1 track ×  ×  → 1 MHz L1 trigger input → PC farm Software trigger reduction ~ 40

HEP Monica Pepe – INFN Perugia 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 spectroscopy … Other physics opportunities