Present Status and Future Prospects of COMET to Search for -e - PowerPoint PPT Presentation

Present Status and Future Prospects of COMET to Search for μ -e Conversion at J-PARC Y. Fujii KEK on behalf of the COMET Collaboration CLFV2016, Charlottesville, 21st June 2016

Outline Physics COMET Experiment Overview R&D and Construction Status Summary & Prospects Y. Fujii @ CLFV2016 2

Physics Quarks u c t Flavors are mixed through CKM matrix in the Standard Model, Already confirmed d b s Leptons Flavors are mixed through PMNS matrix, ν e ν μ ν τ Already confirmed (extension of SM) ? Charged Lepton Flavor Violation Forbidden in the Standard Model, e μ τ ? ? B( μ → e γ )~O(10 -54 ) for SM+ ν oscillation, Not observed so far Y. Fujii @ CLFV2016 3

μ -e Conversion • Muon to electron conversion in nuclei " (TeV) Andre de Gouvea (2013) w/o neutrino emission -54 ) in SM + ν -oscillation • ~O(10 B( µ # e conv in 27 Al)=10 -18 • Enhanced in many BSMs 10 4 • Observation → New Physics • Simple kinematics: E e =M μ -B μ ~104MeV B( µ # e conv in 27 Al)=10 -16 • LHC, other CLFV searches, muon g-2 are complementary B( µ # e $ )=10 -14 B( µ # e $ )=10 -13 10 3 EXCLUDED (90% CL) nucleus -2 -1 2 10 10 1 10 10 μ - ! photonic dominant four-fermion dominant e - Y. Fujii @ CLFV2016 4

Requirements • High statistics 17 of stopping muons are required • >10 • → High intensity proton beam @J-PARC • → π / μ collection using capture solenoid • Background suppression • Intrinsic BG : Muon DIO (Decay In Orbit) • → Excellent momentum resolution Extinction = Number of protons between 2 bunches • Beam BG : Radiative pion capture, Muon Number of protons in a bunch decay in flight, Antiproton, Proton leakage, etc. 1.17 μ s • → Pulse beam + delayed time window proton bunch -9 ) • → Good extinction factor (less than 10 Beam BG • → Curved solenoid DIO BG Signal • Other BG : Cosmic ray • → Add detector for cosmic ray veto Measurement time window Y. Fujii @ CLFV2016 5

COMET Collaboration composed of 175+ researchers of 33 institutes from 15 countries 7 • International collaboration

J-PARC MR Synchrotron * *design value Y. Fujii @ CLFV2016 8

COMET Overview Pion Capture Solenoid 8GeV Proton Beam Muon Stopping Target Electron Spectrometer Muon Transport Solenoid • Aiming O(10 -17 ) sensitivity • 10,000 times better than the current limit • C-shaped μ - transport solenoid Detector Solenoid • For suppress beam BG • Additional C-shaped e - spectrometer • Suppress DIO+beam BG Y. Fujii @ CLFV2016 9

COMET Phase-I Cylindrical Drift Chamber Muon Stopping Target Trigger Hodoscope CyDet Straw Tube Tracker ECAL StrECAL • Construct the first 90 degree of the muon transport solenoid -15 using CyDet • Perform the μ -e conversion search with a sensitivity of 10 • Measure the beam directly using StrECAL as a Phase-II prototype detector Y. Fujii @ CLFV2016 10

Beam and Facility

Proton Beam filled � Bucket'A � filled � Overview of Hadron Beam RCS' Facility MR' � B � d h=2' e l l fi h=9' 4'filled'and'5'empty � Bucket'B � A � • Bunched slow extraction with a 3.2(56) kW operation in Phase-I(Phase-II) • Beam pulsing with a 1.17 μ s interval using “Single Bunch Kicking” method • Accelerate protons up to 8GeV in MR → Deliver them to COMET hall @ Hadron Beam Facility -11 • Extinction factor already measured to be 3 × 10 even in the worst case Y. Fujii @ CLFV2016 12

COMET Hall Jan. 2015 April 2015 Oct. 2015 • COMET hall • Construction completed in last year • High-p/COMET beam line • Construction and Engineering design ongoing Y. Fujii @ CLFV2016 13

Proton Monitor/Target • Proton monitor • Measure the beam profile/extinction in front of the capture solenoid • Use the innovative diamond detector • High radiation tolerance & Fast time response Geometry of proton monitor • First beam test for diamond prototype is ongoing @J-PARC MR • Clear signals synchronized with beam bunch observed • Proton target • Graphite(or SiC)/Tungsten target for Phase-I/Phase-II • Geometry optimized to increase the stopping muon yields, R=13mm, L=700mm Diamond prototype detector Abort line @J-PARC MR Scintillator signal inside beam pipe Target prototype Y. Fujii @ CLFV2016 14

Magnets/Cryogenics • Pion capture solenoid • Coil winding almost done • Mechanical design completed • Muon transport solenoid • Completed, detailed tests are ongoing • Detector solenoid Al stabilized SC wire Coil winding • All 14 coils assembled as one • Cryogenics • Engineering design is in preparation Transport Solenoid Detector Solenoid Y. Fujii @ CLFV2016 15

Muon Beam/Target • Muon transported in a curved solenoid w/ a dipole field • Reduce pions which can produce high momentum secondaries • Momentum and charge selection • Muons stopped inside the series of thin aluminum disks - / π - are ~5 × 10 -4 /3 × 10 -6 / POT • Stopping rate for μ μ - stopping distribution projected on the target plane - µ Longitudinal Distribution -6 10 h05 h05 × + count/p 35 Entries Entries 51033 51033 Mean Mean 5933 5933 RMS RMS 242.8 242.8 30 25 Saddle type coil is put 20 outside of each solenoid 15 Collimators … coil to generate dipole field 10 5 0 5500 5600 5700 5800 5900 6000 6100 6200 6300 6400 z position (mm) Keep the vertical position of low momentum muons μ - stopping distribution along the beam axis Y. Fujii @ CLFV2016 16

CyDet

CDC Position resolutions of CDC prototype obtained in the beam test @Spring-8 • C ylindrical D rift C hamber • Main tracker for Phase-I physics measurement • All stereo wires enable to reconstruct 3D hit positions • 20 layers consists of ~5,000 sense wires + ~15,000 field wires • Gas mixture, He:iC 4 H 10 =90:10 or He:C 2 H 6 =50:50 • Both gas mixtures show good performance • Required momentum resolution, σ p ~ 200 keV/c @p=105MeV/c, is achievable • Mass production/test of readout boards done @IHEP RECBE Board Mass Test @IHEP Y. Fujii @ CLFV2016 18

Detector Construction June 2016 Dec. 2015 June 2016 • CDC construction completed this month • All wires are fine • Inner wall installed • Leak check has just begun • Cosmic-ray test will be done soon Y. Fujii @ CLFV2016 19

CTH • C herenkov T rigger H odoscope • Each Module consists of an acrylic Cherenkov radiator and a plastic scintillator • 64 modules arranged both upstream/downstream sides • Require the 4 hits coincidence to suppress the accidental trigger due to γ rays • Better than 1ns time resolution obtained by using the prototype detector for 100MeV/c electrons • Preamplifier prototype produced and irradiation tests to be done Fine mesh PMT 4 coincidence trigger Analog FE prototype TOP: Plastic Scint. Bottom: Acryl To digitizer Y. Fujii @ CLFV2016 20

StrECAL

StrawTracker gas outlet front-end boards signal lines anode gas manifold optical fi bre-link front-end boards feedthrough signal lines feedthrough 1st straw plane ( x 1 ) HV lines 2nd straw plane ( x 2 ) 3rd straw plane ( y 1 ) 4th straw plane ( y 2 ) gas inlet Beam 1560 gas outlet anode optical fi bre-link front-end boards feedthrough feedthrough gas manifold signal lines gas manifold gas inlet 390 1950 • Straw Tube Tracker consists of ~2500 straw tubes • Main tracker for Phase-I beam measurement / Phase-II physics measurement • Operation in vacuum • 20/12um thick, 9.8/5mm Φ straw tube for Phase-I/Phase-II • Gas mixture candidates: Ar:C 2 H 6 =50:50, Ar:CO 2 =70:30 • Complete the mass production of Phase-I straw tube Y. Fujii @ CLFV2016 22

R&D and Construction Status • Many tests carried out using full-scale prototype Straw Tube × 16 × 2 • Establish the construction procedure • Evaluate out-gas rate of straw tubes • No leak, no significant out-gas • Beam test w/ 105MeV/c electron was done • σ x ~150um obtained → σ p ~180keV/c • Operation in vacuum performed in success • All Phase-I straw tubes have been built already Vacuum Less than 200um σ x everywhere Sigma vs Position for Ar/C2H6=50/50, 2000V 300 Sigma um 250 200 150 100 50 0.1Pa achieved ! 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Position mm Y. Fujii @ CLFV2016 23

Comparisons of scintillator characteristics ECAL NaI(Tl) GSO LYSO Density, g/cm 3 3.67 6.71 7.1 Att. length, cm 2.6 1.38 1.12 Decay const., ns 230 30-60 41 Max emission, nm 415 430 420 Relative LY 100 20 70-80 20mm 120mm 20mm • ECAL is an array of ~2,000 scintillator crystals to cover ~1m of radius • Choose LYSO because of the higher light yield and faster time response than GSO • Use in both Phase-I & Phase-II • Measure the energy deposit and trigger the event • 10mm × 10mm APD sensor attached to the back of each LYSO crystal • Crystals and APDs inside vacuum Y. Fujii @ CLFV2016 24

R&D Status ECAL Prototype overview ECAL modules Vacuum gauge Vacuum Pump May 19, 2016 19th COMET CM : ECAL Prototype Status 4 • Single crystal optimizations 2 → 10 × 10mm 2 , × 3 photon yield } × 4 larger • APD: 5 × 5mm • Wrapping: Teflon+Al-mylar → ESR+Teflon, × 1.3 photon yield • Vacuum test using 8 × 8 prototype detector newly manufactured • Reach ~1Pa vacuum level • Two candidates • Saint-Gobain and OXIDE, performance comparison ongoing Y. Fujii @ CLFV2016 25