Muon Capture on the Deuteron The MuSun Experiment PSI Experiment R-08-01 physics update overview run 2011 analysis progress systematics of impurities beam request 2012 Claude Petitjean μ-stop signals showing pileup of fusion events BV43, Feb 22, 2012

physics update μ- + d  ν + n + n measure rate Λd in μd() atom to <1.5% simplest weak interaction process in a nucleus allowing for precise theory & experiment nucleon FF (GP) from MuCap ab initio QCD calculations with effective field theory close relation to neutrino/astrophysics solar fusion reaction p+p  de+ ν+d scattering in SNO exp. model independent connection to μd by a single Low Energy Constant (LEC) μ + d determines this LEC in clean 2 N system  “Calibrates the Sun”

recent calculations of ΛD ΛD year authors method [sec-1] 386 2001 Ando et al., P. Lett. B533, 25 EFT* 416±6 2009 Ricci et al., N.P. A837, 110 SNPA/EFT* 392.0±2.3 2010 Marcucci et al., P.Rev.C83:014002 EFT* 399.0±3 2011 Marcucci, arXiv:1109.5563 [nucl-th] EFT 410-417 2011 Adam, arXiv:1110:3183 [nucl-th] EFT SNPA … Standard Nuclear Physics Approach (Potential Model + MEC) EFT* … Hybrid Eff. Field Theory Calculation (Pot. Model, EFT op.) EFT … full Effective Field Theory Calculation

experimental update Λd = 1/τμ-d - 1/τμ+ use lifetime method ≥ 1010 μ→eνν decays measure τμ-d to 10ppm Λd = 1/τμ-d - 1/τμ+ low temperature ~34K D2 gas, density φ ~ 6% spin state & hf transition observable via ddμ3He+n fusion reaction new Cryo-TPC with ultra-pure deuterium gas at high density full WFD readout to cope with small signals and fusion reactions purity requirements ~ 1 ppb

the upgraded Cryo TPC vertical drift field 11 kV/cm Vdrift = 5mm/μs h = 72 mm D2 density 6.4% of lq.H2 (5.6 bar) liquid Neon cooling circuit T ~34K HV -80kV grid -3 kV 0.4 mm Be window 48 anode pads (Au-plt) 12 x 9 cm2

setup of MuSun at the πE3 beamline e detector & n counters cold box lq. Neon cooling TPC wfd‘s HV D2 circulation & cleaning system

beam rates (kHz) with kicker overview of run 2011 12 weeks incl. setup & tests 4.8 x 109 good μ- stops in fiducial vol. with decay electron & 4 x 108 μ+ stops 21.2 TB μ- & 2.5 TB μ+ of clean data improvements since run 2010b: upgraded cryo-TPC op. at T = 34K-50K produced new hydrogen-depleted deuterium gas (cp < 10-4) stable HV at 80 kV (no sparks) better frontend electronics gas chromatography w. online sampling new X-ray detectors (Ge, NaJ) clean neutron spectra by liq. detectors new on-/offline analyzer programs  new analysis framework („roadmap“) drifttime effect  impurity control beam rates (kHz) with kicker μSC scint. Trigger 24.3 μSC & μPC pileup-protected 17.8 @ good TPC stop in fiducial vol. 5.6 @ good decay-electron track 3.0

MuSun analysis roadmap

muon beam μ→ z-x stopping distribution in TPC beamspot μSC & μPC only  beamspot μSC & μPC &TPC track  1 pixel ~ 2 mm z-x stopping distribution in TPC 8x6 pixels, first two used for muon track identification  μ→

the accoustic problem in 2010 was solved with base line restorer TPC signals the accoustic problem in 2010 was solved with base line restorer typical example of a muon stop event the pulses are fitted with a template close to a Gaussian 

ES is a measurement of signal strength! energy spectra of muon signals red: muon energy of preceeding anode to stop (Eo) blue: muon energy of stopping anode (E1) black: S-energy ES = Eo + 2 E1  very important! ES is a measurement of signal strength!

fusion events fusion channels in deuterium ddμ → 3He(0.82 MeV) + μ + n(2.5 MeV) 88% R3He = 0.18 mm E3Heobs ~ 0.40 MeV ddμ → 3Heμ(0.80 MeV) + n(2.5 MeV) 12% R3Heμ = 0.6 mm E3Heμobs~ 0.64 MeV ddμ → p(3.0 MeV) + t(1.0 MeV) + μ Rp = 16 mm, Rt = 1 mm Etotobs ~ 3.7 MeV total fusion yield ~5% at density φ = 0.06 (well known from former μCF exp.) μ + separated 3He-fusion μ + separated hor. / vert. (p+t)-fusion examples of muon stop events followed by dd fusion (separated in drift time)

fit of separated 3He fusion-recoils  calibration of pads E ~ 1.6 keV/ch energy resolution of TPC & analysis σE ~ 50 keV 3He↑ ↑μ3He

energy depositions on stopping anode many p+t fusions overlap with μ signal on stop anode!

fit of ~1 shift of μ- (μ+) data shows clean spectra (no bad stops) lifetime spectra fit of ~1 shift of μ- (μ+) data shows clean spectra (no bad stops)

Cs137 calibration spectrum neutron spectra liquid scint. detector w. improved magn. shield Cs137 calibration spectrum neutron time distribution at 2 diff. densities slope shows depopulation of μdF=3/2 hf state 8 liquid scint. detectors with PSD electronics PSD spectrum

spectra of muonic X-rays germanium time spectra: black: μSC trigger red: μ-stop in fid. volume germanium energy spectra (time prompt to the μSC): black: requirement of a delayed electron red: no electron requested (allows high-Z stops)

systematics: the problem with impurities the distorting effect on the lifetime allows only ppb admixtures: Element λdZ ΛdZ (s-1) Δλ (s-1) N 1.45 x 1011s-1 9.3 cZ/ppb 2.7 cZ/ppb O 0.63 x 1011s-1 4.0 cZ/ppb 1.2 cZ/ppb vapor pressures of calculated equilibrium concentrations selected elements of N2 & O2 gases vs temperature

drift time effect ES drops with drift time slope temperature dependent chromatography at 50K: 5 ppb N2 0.6 ppb O2 ↓ drift time effect S-energy vs drift time at 50K ES drops with drift time slope temperature dependent reduced after gas cleaning!  handle on impurities drift time effect vs temperature

search for optimal TPC condition P-T diagram of cryogenic deuterium higher density  higher P,T  more impurities ↔ faster spinflip smaller density  smaller P,T  less impurities ↔ slower spinflip

work plan & beam request 2012 2012 is analysis and commissioning year: further development of analysis programs and Monte Carlo. analyze run 2011. repair and upgrade electron wire chamber system. overhaul CHUPS circulation system. improve cryo-TPC system - remove heat leaks. new & improved frontend electronics. prepare setup and beam tests in new (extended) πE1 area. 2 weeks (end September 2012) for πE1 commissioning. 2012 beam time request: one 4-week cycle (October 2012) in πE1 area. study impurity issues test upgrades of apparatus. final production runs in 2013/2014

top view of extended πE1 area (ready in fall 2012) old πE1 Dolly muSR