Yu. Potrebenikov PAC on particle physics, June 10, 2009 MEASUREMENT OF THE RARE DECAY K +   AT THE CERN SPS P326 – NA48/3 – NA62 New theme: «Study of rare kaon decays in the experiments at the CERN SPS» MEASUREMENT OF THE RARE DECAY K +   AT THE CERN SPS P326 – NA48/3 – NA62 New theme: «Study of rare kaon decays in the experiments at the CERN SPS» NA62 Project, /2014 (R&D – OCAPI Project, OSCAR (1016) theme)

Collaboration: Bern ITP, Birmingham, Bristol, CERN, JINR, Ferrara, Fairfax, Florence, Frascati, Glasgow, IHEP, INR, Liverpool, Louvain, Mainz, Merced, Naples, Perugia, Pisa, Rome I, Rome II, San Luis Potosi, SLAC, Sofia, TRIUMF, Turin Laboratory of High Energy Physics JINR: S. Gevorkian, L. Glonti, E. Goudzovski, V. Kalinnikov, V. Kekelidze, Yu. Kiryushin, N. Kravchuk, N. Kuchinsky, D. Madigozhin, N. Molokanova, S. Movchan, I. Polenkevich, Yu. Potrebenikov, V. Samsonov, S. Shkarovskiy,A. Zinchenko IFIN-HH:L.Dumitru, C.Coca, M.Orlandea, E.Teodoresku (Romania) Project leader: - Kekelidze V.D. (LHEP) Project leader deputy: - Potrebenikov Yu.K. (LHEP)

3 The     decays: a clean test of SM Flavor Changing Neutral Current loop process: s  d coupling and highest CKM suppression Very clean theoretically: short distance contributions dominate in the matrix element; hadronic matrix element can be related to measured quantities ( +   0+ . ( K +   0 e + . SM predictions (uncertainties from CKM elements): 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  × Unique in K and B physics and extremely sensitive to New Physics Present measurement (E787/949): BR(K +   ) = 17.3 × 10  11 ( events) Golden modes

4 Effects of new physics on  decays Br(K +   ) Br(K 0   )

5 P326 SM E787/949 BR(K +   ) = 17.3 ×10  events Mean: E787/949 Br(K +   )

6 Other physics opportunities P-326 Kaon Flux ~100 times NA48/2 Kaon Flux P-326 Kaon Flux ~100 times NA48/2 Kaon Flux Other physics opportunities can be addressed: Lepton – flavor violation ( started with a run 2007 ): K e2 /K  2,K +  +  + e -, K +  -  + e + K e2 /K  2,K +  +  + e -, K +  -  + e + Hadron spetroscopy Search for new low mass particles: K +  +  0 P (pseudoscalar sGoldstino) K +  +  0 P (pseudoscalar sGoldstino)…

7 Task for Dubna group Search for a light sgoldstino in K +   +  0 P (P   ; P   ) If HyperCP 3 events of  -> p  +  - are P ->  +  -,P mass is MeV. (Sum of 2  mass is MeV, so  is almost in rest) For K + decay it also means rather small free energy: — — — = 4.83 MeV So  + may escape into the beam hole as well as muons. But in NA62 precise K + momentum measurement is foreseen, so lost  + is not a problem for the complete reconstruction in the case of P-> . « On sgoldstino interpretation of HyperCP events». D.S. Gorbunov, V.A. Rubakov. Phys.Rev.D73:035002,2006. «Search for light pseudoscalar sgoldstino in K - decays». O.G. Tchikilev et al. Phys.Lett. B602: ,2004. (ISTRA) In models with spontaneous symmetry breaking the superpartners of Goldstone fermion, pseudoscalar P and scalar S goldstinos, should exist. P may be light enough to be found in K + decays. Moreover, for P-> 2  and lost  + track one can use after-magnet half-track (<20 GeV) and RICH momentum. For Br= we will have ~80 events for 10% acceptance.  +  0 P is compatible with  +  0  0 (5% acceptance). If we will have even 1%-downscaled triggers, we will have 40 events for Br=10 -8

8 The experimental precision few The experimental precision is at the level of few in both decay modes (NA48/2) SM estimates SM estimates vary within an order of magnitude few …8x10 -5 (few …8x10 -5 ). There will be real possibility to improve precision level up to one order of magnitude with a modernize experimental set-up SM SUSY & Newphysics Ford et al. (1970) “charged” HyperCP (2000) “charged” TNF-IHEP (2004) “neutral” NA48/2 “charged” “neutral” Smith et al. (1975) “neutral” |A g | Future task

9 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 : prototypes construction and test at CERN and Frascati beams November SPSC decided to recommend NA62 for approval. The SPSC Recommendation was endorsed by the CERN Approved by the CERN Research Board (December 5, 2008) 2009 – 2012: Technical design and construction Start of data taking Proposal to Measure the Rare Decay     at the CERN SPS (P326) CERN-SPSC SPSC-P-326 Schedule Located in the same hall of NA48

10 Goal and Principles of the NA62 O (100) (55 ev/year) K +  + events ~ 10% (<7.5 ev/year) background Physics: BR(SM) = 8× Acceptance 10% K decays ~10 13 (4.8*10 12 /year) Kaon decay in flight technique Intense proton beam from SPS High energy K (P K = 75 GeV/c) Kinematical rejection Veto and particle ID Kaon 3-momentum: beam tracker (2 time) and precise timing (100 ps in GTK) Long vacuum decay region Pion 3-momentum: spectrometer and RICH  /  detection: calorimeters Charged veto: spectrometer K/  CEDAR  /  /e separation: RICH Use as much as possible the existing NA48 infrastructures KK K+K+  m 2 miss =(P K  P  ) 2

11Backgrounds 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) Hermetic span across the signal region Rejection must rely on veotes Kinematically constrainedNot kinematically constrained 8% of total background

12 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 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 Largest background rejection

13 Layout of the experiment SPS primary p: 400 GeV/c Unsepared beam: 75 GeV/c 800 MHz  /K/p (~6% K + ) ++ ~11 MHz of K + decays K     Needs ~same amount of protons on target as NA48 (GTK) (DP/P = 1.1%) Kaon decays / year = 4.8 × 10 12

14 NA62 Event Display GTK ANTI STRAW LKR RICH MUV Vacuum tank not shown

A tracking system 15 Straw Tracker Setup: Current Setup He vacuum ~120 m vacuum ~2.5 m KK  KK  The Straw Tracker is essential to study ultra-rare-decays in flight The Straw Trackers operated in vacuum will enable us to: Remove the multiple scattering due to the Kevlar Window Remove the acceptance limitations due to the beam-pipe Remove the helium between the chambers LKr RICH Kevlar Window Beam Pipe Straw Trackers

16 Magnetic Spectrometer 4 chambers with 16 layers of straw tubes each Low X/X 0 Good space & angle resolution & angle resolution Veto for charged particles particles 130  m per hit The Magnetic Spectrometer (i.e. the downstream tracker) Rate: ~ 40 KHz/cm 2 (max 0.8 MHz per  10 mm straw) 5 cm radius beam hole displaced in the bending plane In vacuum, X/X 0 ~0.1% per view 10 cm

Straw production and quality Seam 0.85 mm Seam 0.40 mm , mm 17

Simulation From 2006 – GEANT4 + VMC for detector simulation From 2007 – GARFIELD for simulation processes into drift volume: threshold = 4 fC threshold = 6 fC threshold = 12 fC Electron drift lines in a straw Signal shape from ASD-8 chip 18

Design and assembling of the first straw prototype 48 straws: 36 - Al 12 - Cu+Au 19

Cosmic test in Dubna cm Residuals Resolution about 210  m 20

21 Test run 2007 Main goal: estimation of a straw spatial resolution Statistics: Muon beam - 160M Pion beam- 60M Kaon beam- 550M Total- 770M ~127 m from a beam target ~90 m to DCH Trigger condition: Q1 x 1-track ~10 5 triggers/burst (burst /4.8 s) TDC resolution – ps ASD-8 chip in FEE

Test run 2008 Non-inflammable gas mixture: CO 2 +isoC 4 H 10 +CF 4 (82%:5%:13%) Burst /4.8 s TDC resolution – ps CARIOCA and ASDQ chips in FEE Statistics: HVTh reshold Run numberStat istics in M 2400 V4 - 6 fCfrom 21146till V4 - 6 fCfrom 21157till V4 - 6 fCfrom 21162till V fC V4 - 6 fCfrom 21169till

Electronics choosing Electronics choosing New FEE - based on ASDQ chip (120 Ohm; 8-10 mV/fC; ns peaking time, 4200 e noise) - based on CARIOCA chip (45 Ohm; 14 mV/fC; ns peaking time, 2000 e noise) 23

Spatial resolution & efficiency Th=6 fCTh=12 fC Efficiency R=4.7 mm 99.98% 2400V 2600V 2500V 2400V 2600V 2500V 24

New straw prototype 25

Straw view design 26

Autonomous straw 27

Straw fixation like in CREAM Straw fixation like in CREAM 2200 straws is produced in a half of year 28

Combination design: ring + square shape 29

Schedule of the Project realization 30

Costs and requests №Expenses itemUnit1-st year 2-nd year 3-rd year 4-th year 5-th yea 2006 – 2010 years Direct costs for the project 0.Operational costs Acceleratorshours 2.Design officehours Workshopshours Materials and consumablesK USD EquipmentK USD Payments for R&D works performed according contracts Travel expenses, including:K USD a) to countries outside the ruble zone K USD b) to the ruble zone countriesK USD c) according to protocols Total direct expensesK USD

Units.Requirement resources in The offer of the Laboratory on distribution of resources 1-year2-year3-year4-year5-year The basic units and the equipment: Necessary resources: a) Mechanical works at the JINR Experimental Workshop b) Electronics at the JINR Experimental Workshop c) Laboratory Fabric d) DB of laboratory norm-hour e) The accelerator f) The reactor g) Computers hour. Working coststhousand US $ Source of financing: budget including foreign currency means thousand US $ Contributions of collaborants Grants (INTAS+ISTC) Sponsors Contracts Other sources thousand US $ Costs and requests

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Spares 34

Project X

36 Main detectors: CEDAR & Gigatracker Tagging the kaon to keep the beam background under control Minimal material budget Good time resolution H 2 instead of Ne New phototubes The CEDAR (kaon ID) R-O chip Si sensor pixel matrix mechanical support The GIGATRACKER (kaon measurement) Requirements: Track and time each beam particle Time resolution: 200 ps / station Momentum resolution: 0,22% relative error Material Budget: < 0.5 % X 0 / station Pattern: 300 x 300 mm 2 Two options for the Read-Out: On-Pixel TDC End-of-Column TDC Both Designs in 130 nm IBM CMOS Technology (submitted in March 09)

Main detectors: Large angle veto 37 CABLING SUPPORTS MAN HOLE LEAD GLASSES VETO 1-5 Mechanics for the first full ring was produced 2008 tests at CERN Preliminary time resolution with kaons s t = 1.02 ns OPAL LEAD GLASS

38 Measurement of the inefficiency K + data taken in a dedicated NA48 test run in 2004 using K +  +  0 Main detectors: LKr calorimeter Tagged  using an SPS electron beam (2006) Inefficiency measured for E  > 2.5 GeV > 10 GeV,  10 GeV,  < confirmed  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 New Read-Out system is necessary

Main detectors: RICH detector 3939 Neon Gas at atmospheric pressure Mirror Mosaic (17 m Focal Length) 2×1000 PMT (hex packing 18 mm side) Vessel: 17 m long, 3 m dd Beam Pipe Beam RICH-100 has been Tested in 2007 at CERN SPS Dt Event ≈ 70 ps RICH-400 is tested now at CERN SPS

Main parameters Material: Mylar, 36  m with Al (0.75  m at both side) or Cu+Au: (  m ) Material budget ( per view ): Straws – (0.93% – 0.95) %X 0 (450 straws) Wires %X 0 (Luma 861) Gas mixture %X 0 (CO2 90%+CF4 5%+Isobutene 5%) Inner supports %X 0 (Ultem bushes and twisters) Straw dimensions and quality:   0.5 mm (9.2 mm effective area) Length mm (2100 mm active area) Straightness mm Elongation- 2.0 mm per m  increasing mm per 1 atm overpressure Gas flow cm 3 /min (70 cm 3 /min per view) Production technology and rate: Ultrasonic weld, up to 400 mm straw per 1 minute 40

Precise timing 41 Unseparated beam, in-flight decay: How do you associate the parent kaon to the daughter pion in a ~1 GHz beam? K + : Gigatracker (pixel detector) with very good time resolution (~ 100 ps) p + : RICH (Neon, 1 atm) read out by Photomultipliers K+K+ p     Gigatracker (rate ~ 1 GHz) RICH (rate ~ 10 MHz) ~120 m CEDAR (rate ~ 50 MHz)

42 The Tracking system: Gigatracker Low X/X 0 not to spoil the beam Good space resolution to match the downstream tracker resolution 200 Si  m sensor 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) The Gigatracker (i.e. the beam tracker) Rate: 760 MHz (charged particles) ~60MHz/cm 2 3 Si pixel stations across the 2 nd achromat: size 60 × 27 mm 2 Readout chip: 1st MPW in 0.13  m technology Readout chip: 1st MPW in 0.13  m technology is ready to test (results by September) is ready to test (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

43 The Veto system Large angle (10, 50 mrad): Rings calorimeters (in vacuum) Rate: ~4.5 MHz (  ) + ~0.5 MHz (  ) inefficiency for E  in 0.05,1 GeV 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 (  ) inefficiency for E  in 1,5 GeV inefficiency for E  >5 GeV Small angle (<1 mrad): Shashlik technology Rate: 0.5 MHz (  ) inefficiency (high energy photons) New Readout Extruded scintillator – lead sampling calorimeter 6 m long + magnet for beam deflection Rate: ~7 MHz (  )+~3 MHz (  ) 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

Spatial resolution estimation – 1 algorithm d, cm R, cm  2 =   7 2  = 65 – 67  m for R = 2.5 mm Gap=1.2 mm

Spatial resolution estimation – 2 algorithm T-T sc, ns T, ns T 0 fit T, ns Drift time vs X from DCH RT-dependence from the symmetric straw tube 45

Manifolds and WEB to the FEE 46

47 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

48 Analysis: background rejection Events/yearTotal Region I Region II Signal (acc=17%) K++0K++0K++0K++ K +  + K +  <0.1 K +  e +  +   K +  e +  +   ~2negligible~2 Other 3 – track decays ~1negligible~1 K++0K++0K++0K++01.3negligible1.3 K++K++K++K++ K +  e + (  + )  0, others negligible Total bckg. <93.0<6 S/B ~ 8 (Region I ~5, Region II ~9)

49TriggerLevel L0 “hardware” L1-L2 “software” Input ~10 MHz 1 MHz Output O (KHz) Implementation Dedicated hardware TDAQ farm Actions RICH 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:

Presentations 1.NA62/P-326 Status report. CETN-SPSC CERN, pp. 2.P-.L. Frabetti, S.A. Movchan. Preliminary Results of the Dubna Straw Drift-Tubes Test - Sept NA internal note. 15 May, Yuri Potrebenikov. The K + to  + bar( ) experiment at CERN. 13th Lomonosov conference on elementary particle physics. 23 to 29 Aug. 2007, Moscow State University, Moscow, Russia. 2.S. Movchan. Precise measurement of the very rare decay K +   +. PSD08. Glasgow, Scotland, 1-5 of September Spasimir Balev: Measurement of K +   + decay branching ratio at NA62 experiment. PIC08, Perugia, Italy, June Evgueni Goudzovski: Searches for physics beyond the Standard Model by NA48 and NA62 at CERN. DIS2008,, University College, London, UK, 7-11 April 2008, proceedings due by June reports have been presented at the NA48/NA62 meetings, including 6 – by videoconference service. 50