Peter Kammel for the MuSun Collaboration

Peter Kammel for the MuSun Collaboration Muon Capture on the Deuteron The MuSun Experiment BV39, Feb 21, 08

Collaboration V.A. Andreev, V.A. Ganzha, P.A. Kravtsov, A.G. Krivshich, E.M. Maev, O.E. Maev, G.E. Petrov, G.N. Schapkin, G.G. Semenchuk, M.A. Soroka, A.A. Vasilyev, A.A. Vorobyov, M.E. Vznuzdaev Petersburg Nuclear Physics Institute, Gatchina 188350, Russia D.W. Hertzog, P. Kammel, B. Kiburg, S. Knaack, F. Mulhauser, P. Winter University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA M. Hildebrandt, B. Lauss, C. Petitjean Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland T. Gorringe, V. Tishchenko University of Kentucky, Lexington, KY 40506, USA R.M. Carey, K.R. Lynch Boston University, Boston, MA 02215, USA R. Prieels Universite Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium F.E. Gray Regis University, Denver, CO 80221, USA A. Gardestig, K. Kubodera, F. Myhrer University of South Carolina, Columbia, SC 29208, USA Combined forces MuCap & MuLan

Goal and Motivation m- + d  n + n + nRateLd from md() atom • MeasureLdto < 1.5 % • Simplest weak interaction process in a nucleusallowing for precise theory & experiment  nucleon FF (gP) from MuCap  model-independentcalculations with effective field theory • Close relation to neutrino/astrophysics  model-independent connection m+dto pp fusion and n+d reaction • Broader Impact on modern nuclear physics  EFT relates m+d to strong processes like p+d  g + n +n, ann

m + d  n + n + nTheory Axial current reaction Gamow-Teller 3S1 1S0 • one-body currents well defined • FF, deuteron wavefunction, ann • two-body currents not well constrained by theory (short distance physics) • Methods • Potential model + MEC • Effective field theories (EFT) • pion less (q/mp) • ChPT(q/L) • hybrid EFT (EFT operators, Pot.Model wavefct) D p MEC EFT  L1A, dR

m + d Experiment m   d • Experimental Challenges • Dalitz Plot Intensity at low Enn ChPT covers most of DP pEFT only pn< 90 MeV/c m → enn lm= 455162 s-1 mdq,d → n+n+nLq ~ 10 s-1, Ld = 400 s-1md() + d→ md() + dddm→ 3He + n + mrates ~ lm

Precise Experiment Needed Determine L1A from clean system Ramnifications for n-astro physics Quantify consistency of hybrid approach consistent ChPT pionless, needs L1A hybrid EFT Potential Model + MEC

Connection to Neutrino/Astrophysics • Basic solar fusion reaction p + p  d + e+ +  • Key reactions for Sudbury Neutrino Observatory e + d  p + p + e- (CC) x + d  p + n + x (NC) • Intense theoretical studies, scarce direct data • EFT connection to m+d capture via LEC L1A, dR • Muon capture soft enough to relate to solar reactions  with L1A ~ 6 fm3

 Quest for L1A, dR “Calibrate the Sun” • Precision m+d experiment by far the best determination of L1A in the theoretically clean 2-N system

Muon Capture, Big Picture { gP, gA, ChPT } m + p m + d m + 3He { gP, gA, ChPT, L1A, ann } { gP, gA, hybrid EFT, L1A, 3N} Final MuCap 2-3x improvement Combinedanalysis

Experimental Strategy Two main conditions • Unambiguous physics interpretation Muon kinetics  optimization of D2 conditions • Very high precision Ld to 1.2% (5 s-1) Statistics: several 1010 events Systematics !

Muon Kinetics Collisional processes density f dependent, e.g. hfs transition rate from q to d state = flqd densityf normalized to LH2 density Muon-catalyzed Fusion lq lq lqd lqd ld ld lm complicated, can one extract fundamental weak parameters ?

Optimize Muon Kinetics • Time Distributions • Sensitivities (Ld 1%, lx  2 sx) MuCap MuSun md md() md() m3He

Use Basic MuCap Technique m → enn Ldreduces lifetime by 10-3 + log(counts) - μ+ μ – te-tm • Lifetime method 1010m→enn decays measure- to 10ppm, d = 1/- - 1/+to 1% • Unambiguous interpretation at optimized target conditions • Ultra-pure gas system and purity monitoring at 1 ppb level • Clean m stop definition in active target (TPC) • 3 times higher rate with Muon-On-Request (MuLan) MuCapTPCtop TPCside

Experiment Overview e eSC ePC2 ePC1 mPC Cryo-TPC m mSC

Observables • Observables in MuSun experiment • decay electrons main observable • fusion and capture essential as kinetics and background monitors Experience from MCF experiments mN capture 1.8 1010 109 5 105

Cryo-TPC Design Criteria

Cryo-TPC Design

Technical Design Cryo-System Vibration free cooling Continuous cleaning

Detectors and DAQ Cryo-TPC special Other detectors/infrastructure from MuCap g detectors as impurity monitor DAQ from MuCap/MuLan new: full analog TPC readout (complicated energy spectrum) 10x10 pads two 8-bit waveform digitizer channels per pad (50 MHz) 15 MB/s (4 MHz/s) beforelossless compression 2006 BU digitizer

Statistics + Systematics 1.81010 events

Pad Optimization in Progress • Muon stop parameters • Fake stops by m+p scattering • Fusion interference GEANT 10x10 pad GEANT MuCap TPC

Gas Purity (Z-1)* + n • CirculatingHydrogenUltrahighPurificationSystem(CHUPS) US CRDF 2002, 2005 • New: • cryo-TPC • cryo filter before TPC • continuous getter in gas flow for gas chromatography • Particle detection in TPC much harder – fusionfor MuSun – m signal 1 MeV • excellent TPC resolution • full analog readout • tags – p after capture – X-ray • protium measurement Rare impurity capture:md + Z d + mZ  (Z-1)* + n MuCap achieved: ~ 10 ppb purity and 0.1 ppb purity monitoring MuSun needs: ~ 1 ppb purity or 0.5 ppb purity monitoring

Measuring Program Stage 1 – 300 K TPC Rebuild (spare) MuCap TPC as ionization chamber Energy resolution Identification and separation of fusion recoils Full analog readout Measure md → mZ transfer rate Optimize mN capture monitor with dedicated setup Stage 2 – Cryo-TPC ?6 Ready Fall 08 Ready Fall 09 2-3 runs in total (prep. and data taking) 4 years

Responsibilities & Budget • Budget estimates Total new equipment 350k CHF Annual running costs 100k CHF Heavily based on larger investments made for MuCap/MuLan • Already positive response from main funding agencies National Science Foundation, USA Russian Academy of Sciences, Russia • Full funding requests to agencies after PAC approval

Peter Kammel for the MuSun Collaboration