Particle Physics Experiments at PSI Stefan Ritt Paul Scherrer Institute, Switzerland

Sept. 8th, 2008CHIPP Plenary Lausanne2 Beyond the SM Find New Physics Beyond the SM High Energy Frontier Produce heavy new particles directly Heavy particles need large colliders Complex detectors High Precision Frontier Look for small deviations from SM (g-2) , CKM unitarity Look for forbidden decays, EDM Requires high precision at low energy

Sept. 8th, 2008CHIPP Plenary Lausanne3 Precision Experiments at low Energies UCN/nEDM (courtesy Klaus Kirch) FAST (courtesy Martin Pohl) PEN (courtesy Dinko Pocanic) MEG CHIPP Plenary 2007

Sept. 8th, 2008CHIPP Plenary Lausanne4 UCN source at PSI Latest news: UCN tank delivered at PSI on September 4 th, 2008 Complete source construction in 2009 Deliver few billion UCN every ~ 800 s ~ 1000 cm -3 UCN in typical experiment (today this is ~10 cm -3 at ILL Grenoble) p-beam 1.2 MW D2OD2O solid D 2 UCN in vacuum

Sept. 8th, 2008CHIPP Plenary Lausanne5 Neutron EDM Search Present best limit: d n < 2.9 x e cm Sussex-RAL-ILL experiment C. A. Baker et al., PRL 97 (2006) New collaboration (12 groups, 45 people) operates and improves this apparatus at ILL Grenoble (Phase I) Move to PSI beginning of 2009 Operation at PSI 2009 – 2011 (Phase II) Sensitivity goal: 5 x e cm New experiment operational 2011 Operation 2011 – 2015 (Phase III) Sensitivity goal: 5 x e cm

Muon lifetime measurement with FAST Principles of operation: Imaging scintillator target Observes  -  -e decay chain Online analysis, output 0(10 3 ) lifetime plots Highlights 2008: Stable running with mean rate of 30 kHz 1.5 x events collected so far Expect total of O(3  ) events Excellent data quality ++ ++

Sept. 8th, 2008CHIPP Plenary Lausanne7 Limiting factor in 2008 rate: Occasional “bursts” in trigger, require frequent system resets when rate exceeds 70 kHz Needs further investigations, will be done after a successful data taking period Verification of systematic error: Search for variation of the result by systematically leaving out part of the data If systematic variations are found, replace affected data with new one, which requires more statistics than what is planned for the final result It is thus likely that running in 2009 will be requested FAST Challenges for 2008 data: Verify knows sources of systematics with 30 times more statistics Understand time structure of background from beam ,  and e Look into additional sources of systematics (pile-up,  SR effects)   =[ ±0.031 (stat) ±0.015 (syst)] ns First result published in 2008 (10 10 events): Phys.Lett. B663 (2008) 172

PEN Experiment Measurement of B(  +  e + )

Sept. 8th, 2008CHIPP Plenary Lausanne9 PEN Experiment (5)  Marciano and Sirlin [PRL 71 (1993) 3629] (1)  Decker and Finkemeier [NP B 438 (1995) 17] (1)  Cirigliano and Rosell [PRL 99 (2007) ] 1.230(4)  Current PDG value PEN goal: 26 authors

Sept. 8th, 2008CHIPP Plenary Lausanne10 Motivation B e/  is given in SM with accuracy. Deviations caused by new pseudoscalar interactions (mass scale  eP ): Thus (  B/B) exp =10 -3 probes  eP ~ 10 3 TeV! This gives limits on Charged Higgs in theories with richer Higgs sector than SM R-parity violating SUSY Pseudoscalar and Vector leptoquarks in various theories with dynamical symmetry breaking Non-zero neutrino masses and mixing

Sept. 8th, 2008CHIPP Plenary Lausanne11 The PIBETA/PEN Detector

Sept. 8th, 2008CHIPP Plenary Lausanne12 Experimental Method and Status Stopped  + beam with 1.5  10 4  + /sec. Pion decays detected in 250 ns wide window Waveform digitizing of active beam counters/degraders/targets Two development runs in 2007 and 2008 to ramp up the beam rate and DAQ to design specifications Recorded in 2007 and 2008: > 8   stop > 4.7  10 6  e decays   B/B stat < 5  Detailed data analysis under way in preparation for a 2009 run Double the statistics in 2009 to reach the overall goal

MEG Experiment Search for  e 

Sept. 8th, 2008CHIPP Plenary Lausanne14 LFV in SM and SUSY While LFV is forbidden in SM, it is possible in SUSY  W-W-   e e-e-   e-e- ≈ Current experimental limit: BR(   e  ) <

Sept. 8th, 2008CHIPP Plenary Lausanne15 “Accidental” Background e     e  180º  → e  signal very clean E g = E e = 52.8 MeV   e = 180º e and  in time e    e e    e Annihilation in flight Background Good energy resolution Good spatial resolution Excellent timing resolution Good pile-up rejection

Sept. 8th, 2008CHIPP Plenary Lausanne16 Collaboration 64 People (40 FTEs) from five countries

Sept. 8th, 2008CHIPP Plenary Lausanne17 The complete MEG detector Beam Line: 10 8  + /sec small beam spot excellent background suppression designed by Peter-Raymond Kettle Beam Line: 10 8  + /sec small beam spot excellent background suppression designed by Peter-Raymond Kettle Drift Chamber: 16 radial segments Almost zero mass in spite of complicated geomety Thanks to Malte Hildebrandt Drift Chamber: 16 radial segments Almost zero mass in spite of complicated geomety Thanks to Malte Hildebrandt Xenon Calorimeter: Largest liquid xenon detector worldwide Light detected by ~900 PMTs Excellent resolutions Big effort for purification Xenon Calorimeter: Largest liquid xenon detector worldwide Light detected by ~900 PMTs Excellent resolutions Big effort for purification Timing Counter: Longitudinal bars with fine-mesh PMTS Transversal fibers with APD readout Timing resolution: 40ps (  )

Sept. 8th, 2008CHIPP Plenary Lausanne18 Waveform Digitizing Pile-up is severe problem at MEG Experiment “DRS” chip developed at PSI to digitize 8 channels at 5 GSPS/12 bit Use waveform digitization on all ~3000 channels (PMTs, Drift Chamber)  100 TB/year after compression Do signal shaping, filtering, integration in FPGA firmware or front-end PCs Pile-up is severe problem at MEG Experiment “DRS” chip developed at PSI to digitize 8 channels at 5 GSPS/12 bit Use waveform digitization on all ~3000 channels (PMTs, Drift Chamber)  100 TB/year after compression Do signal shaping, filtering, integration in FPGA firmware or front-end PCs 2000 channels waveform digitizing 40 MHz, ~20 mV, 1kHz repetition noise finally identified the liquid xenon pump as the source This noise can screw up timing for rare events Without waveform digitizing, this would have been very hard to debug DRS4 chip now available from PSI for other experiments

Sept. 8th, 2008CHIPP Plenary Lausanne19 Xenon Calorimeter Light Yield Total number of photoelectrons in Landau peak of cosmic events (  160 MeV) LN 2 coolingliquid purificationgas purification absorption length >3m

Sept. 8th, 2008CHIPP Plenary Lausanne20 Current resolution estimates all FWHM Large Prototype Simulated Measured 2007 Prospects 2008 Gamma Energy [%]4.5 – Gamma Timing [ns] Gamma Position [mm]4.5 – e+ Timing [ns] e+ Momentum [%] e+ Efficiency [%]65 Muon Decay Point [mm] Muon Rate [Hz] 0.3  10 8 Running Time [PSI week]100 Single Event Sensitivity 0.5  Accidental Rate  # Accidental Events % CL Limit1.7  Single Event Sensitivity Acc. Rate

Sept. 8th, 2008CHIPP Plenary Lausanne21 Run Schedule 2008 MayJuneJulyAugustSeptemberOctoberNovemberDecember 2008: Set-up & Calibrations: Beam Tuning Xenon Purification Xenon Calibration (CW Accel.) Detector Re-install and debugging  0 calibration physics data taking Goal 2008 with weeks of data taking: Produce “significant” result Goal 2008 with weeks of data taking: Produce “significant” result tuning + test: MEG trigger Pre-pysics data physics analysis method

Sept. 8th, 2008CHIPP Plenary Lausanne22 Long term plans Measure 2-3 years from now to obtain statistics If  e  is found Verify signal Measure polarized  e  decay If not Improve detectors (smaller PMTs) Push maybe to  eee next talk!

Sept. 8th, 2008CHIPP Plenary Lausanne23

Sept. 8th, 2008CHIPP Plenary Lausanne24 History of LFV searches Long history dating back to 1947! Best present limits: 1.2 x (MEGA)  Ti → eTi < 7 x (SINDRUM II)  → eee < 1 x (SINDRUM II) MEG Experiment aims at Improvements linked to advance in technology  → e   → eA  → eee MEG SUSY SU(5) BR(   e  ) =   Ti  eTi = 4x  BR(   eee) = 6x SUSY SU(5) BR(   e  ) =   Ti  eTi = 4x  BR(   eee) = 6x cosmic  stopped   beams stopped 

Sept. 8th, 2008CHIPP Plenary Lausanne25 Current SUSY predictions “Supersymmetric parameterspace accessible by LHC” W. Buchmueller, DESY, priv. comm. current limit MEG goal 1)J. Hisano et al., Phys. Lett. B391 (1997) 341 2)MEGA collaboration, hep-ex/ f t (M)=2.4  >0 M l =50GeV 1) tan 

Sept. 8th, 2008CHIPP Plenary Lausanne26 High pass filtering original waveform template fit after optimized high pass FIR filter integration area Get rid of baseline (low frequency) noise Improve resolution significantly Get rid of baseline (low frequency) noise Improve resolution significantly

Sept. 8th, 2008CHIPP Plenary Lausanne27 VME Board 32 channels input General purpose VPC board built at PSI 40 MHz 12 bit FADC USB adapter board USB adapter board

Sept. 8th, 2008CHIPP Plenary Lausanne28 Calibration

Sept. 8th, 2008CHIPP Plenary Lausanne29 Planned Calorimeter Calibrations Combine calibration methods different in complexity and energy: MethodEnergyFrequency LED/Laser pulser~few MeVContinuously 241 Am source on wire 5.6 MeV  Continuously p +  7 Li17.6 MeV  daily  0 production on LH 2 54 – 82 MeV  once per beam time ? LED 100  m gold-plated tungsten wire Cockroft-Walton Accelerator (1 MeV)

Sept. 8th, 2008CHIPP Plenary Lausanne30  0 Calibration NaI target 0000   Tune beam line to  - Use liquid H 2 target  - p    n Tag one  with movable NaI counter Beamline & target change take ~1 day Tune beam line to  - Use liquid H 2 target  - p    n Tag one  with movable NaI counter Beamline & target change take ~1 day 