Yu. Potrebenikov LHEP, STS section, March 19, 2009 ИЗМЕРЕНИЕ РЕДКОГО РАСПАДА K +   НА УСКОРИТЕЛЕ SPS ЦЕРН MEASUREMENT OF THE RARE DECAY K +   AT THE CERN SPS P326 – NA48/3 – NA62 Предложение новой темы: «Изучение редких распадов заряженных каонов в экспериментах на SPS CERN» NA62 Project, /2014

Сотрудничество: Берн: Бирменгем, ЦЕРН, Дубна, Феррара, Фаирфакс, Флоренция, Фраскати, Лоувайн, Майнц, Мерсед, Москва, Неаполь, Перуджа, Протвино, Пиза, Рим, Сан Луис Потоси, СЛАК, София, ТРИУМФ, Турин Лаборатория физики высоких энергий Шифр темы: /2014. ОИЯИ: Геворкян С., Глонти Л.Н., Гудзовский Е.А., Зинченко А.И., Калинников В.А., Кекелидзе В.Д., Кирюшин Ю.Т., Кравчук Н.П., Кучинский Н.А., Мадигожин Д.Т., Мовчан С.А., Молоканова Н.А., Поленкевич И.А., Потребеников Ю.К., Самсонов В.А., Шкаровский С.Н. НИФиЯЭ (Румыния): Кока К., Думитриу Л., Орландеа М., Теодореску Е. Руководитель проекта:- Кекелидзе В.Д. (ЛФВЭ) Зам. руководителя проекта: - Потребеников Ю.К. (ЛФВЭ)

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, hadronic matrix element can be related to measured quantities ( 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  × 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 Setting the bar for future  experiments P326 SM E787/949 BR(K +   ) = 17.3 ×10  events Mean: E787/949 K +   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 + Search for new low mass particles: K +    (light RH neutrinos) K +    (light RH neutrinos) K +  +  0 P (pseudoscalar sGoldstino) K +  +  0 P (pseudoscalar sGoldstino) Hadron spetroscopy …

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 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 Base of the NA62 (NA48/3) O (100) K +  + events ~ 10% background 1) Physics: BR(SM) = 8× 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 NA48 infrastructures Be pragmatic 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) 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 ++ Beam acceptance = 12 mstr (25× NA48/2) beam tracker = 58×24 mm 2 Kaon decays / year = 4.8 × SPS primary p: 400 GeV/c Unseparated beam: 75 GeV/c (DP/P = 1.1%) 800 MHz p/K/  (~6% K + ) duty cycle 4.8/16.8 s

14 Principles of the NA62 High momentum kaon beam to improve the rejection of the  0 induced backgrounds High momentum kaon beam to improve the rejection of the  0 induced backgrounds Decay in-flight to avoid the scattering and the backgrounds introduced by the stopping target Decay in-flight to avoid the scattering and the backgrounds introduced by the stopping target The experimental technique exploits: 1. Precise timing to associate the outgoing  + to the correct incoming parent particle (K + ) 2. Kinematical Rejection of two- and three-body backgrounds 3. Vetoes (  and  ) 4. Particle Identification (K/ ,  /  ) To achieve the required background suppression, these techniques will be combined together minimizing the correlations

15CEDAR CEDAR: existing differential Cerenkov counter at CERN to be placed on the beam 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) 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). Plan: to test of fast photomultipliers using Cerenkov light. pion kaon proton

Gigatracker station 16 R-O chip Si sensor pixel matrix mechanical support Requirements: Track and time each beam particle Time resolution: 200 ps / station 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

Large angle veto design 1717 CABLING SUPPORTS MAN HOLE LEAD GLASSES HANDLING VETO 1-5 LNF-SPAS C.Capoccia Mechanics For the first full ring was ordered

Vetoes 18 Preliminary time resolution with kaons s t = 1.02 ns OPAL LEAD GLASS BEING PROCESSED FOR USE IN NA62 in Building 904 (CERN) 2008 tests at CERN

19 Measurement of the inefficiency K + data taken in a dedicated NA48 test run in 2004 using K +  +  0 LKr calorimeter Tagged  using an SPS electron beam (2006) Inefficiency measured for E  > 2.5 GeV > 10 GeV,  10 GeV,  < 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

RICH detector 2020 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

21 CERN ECN3 Cavern K12 beam line (NA48-NA62) 200 GeV/c negative hadron beam from CERN SPS (mainly pions) 96 PMT Hamamatsu R m long 60 cm wide vessel, filled with Neon at atm. pressure 17 m focal, 50 cm wide, 2.5 cm thick glass mirror by MARCON 2007 test RICH-100 prototype at CERN

2007 test RICH-100 prototype results 22  c ≈ 50  rad (biased by PM geometry) N Hits ≈ 17Dt Event ≈ 70 ps

A tracking system 23 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

24 The Tracking system: 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

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 80%+CF4 14%+Isobutene 6%) 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

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

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

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

Cosmic test in Dubna cm Residuals Resolution about 210  m

30 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

Spatial resolution estimation R, cm 25 d, cm Gap=1.2 mm d, cm Residual Distance to track  = 60  m  = 54  m Resolution

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

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)

Different electronics connections Straw termination scheme Electronics connection in 2008

Test of electronics RT dependence Time distribution Residuals  = 60  m  = 72  m HV,kV ASDQ, no termination CARIOCA, no termination

Straw view design

Detector design: square shape with glued straws 1 atm overpressure – tension reduce by 300 g for 2 m straw

Detector design: independent straw design

Detector design: movable straw fixation

Detector design: straw fixation like in CREAM 2200 straws is produced in a half of year

Detector design: ring shape Max deformation mm Advantages compensation of perpendicular forces low amount of material 20% less of total straw length Problems precise hole production different lengths of straws

Combination design: ring + square shape

Manifolds and WEB connections to the FEE

Schedule of the Project realization

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

Spares

Precise timing 50 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)

51 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

52 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

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.

Project X 2015

57 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

58 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)

59TriggerLevel 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:

60Conclusions To search for new physics using rare Kaon decays P-326 experiment is proposed and prepared for measurement of the Br(K +  + ) with a ~10% accuracy (& for other physics opportunities ) Overall simulation and performances are under review. General design is mostly defined. Overall simulation and performances are under review. The R&D program is well advanced: construction of detector prototypes and tests are in progress (in some cases - completed). Important results should be obtained by the end of 2007 The new experiment should be able to reach a ~ sensitivity per event at an existing machine and employing the infrastructures of an existing experiment.