1 Peter Kammel for the MuSun Collaboration Muon Capture on the Deuteron The MuSun Experiment BV39, Feb 21, 08
2 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 , 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
3 Goal and Motivation + d + n + n Rate d from d( ) atom Measure d to < 1.5 % Measure d to < 1.5 % n Simplest weak interaction process in a nucleus allowing for precise theory & experiment nucleon FF (g P ) from MuCap model-independent calculations with effective field theory n Close relation to neutrino/astrophysics model-independent connection +d to pp fusion and +d reaction n Broader Impact on modern nuclear physics EFT relates +d to strong processes like +d + n +n, a nn
4 + d + n + n Theory Axial current reaction Gamow-Teller 3 S 1 1 S 0 n one-body currents well defined FF, deuteron wavefunction, a nn n two-body currents not well constrained by theory (short distance physics) n Methods Potential model + MEC Effective field theories (EFT) pion less (q/m ) ChPT (q/ ) hybrid EFT (EFT operators, Pot.Model wavefct) MEC L 1A, d R EFT
5 + d Experiment n Experimental Challenges n Dalitz Plot Intensity at low E nn ChPT covers most of DP EFT only p < 90 MeV/c → e = s -1 d q, d → n+n+ q ~ 10 s -1, d = 400 s -1 d( ) + d→ d( ) + d dd → 3 He + n + rates ~ d
6 Precise Experiment Needed Potential Model + MEC pionless, needs L 1A hybrid EFT consistent ChPT Determine L 1A from clean system Ramnifications for -astro physics Quantify consistency of hybrid approach
7 n Basic solar fusion reaction p + p d + e + + n Key reactions for Sudbury Neutrino Observatory e + d p + p + e - (CC) x + d p + n + x (NC) n Intense theoretical studies, scarce direct data EFT connection to +d capture via LEC L 1A, d R n Muon capture soft enough to relate to solar reactions Connection to Neutrino/Astrophysics with L 1A ~ 6 fm 3
8 Quest for L 1A, d R Precision +d experiment by far the best determination of L 1A in the theoretically clean 2-N system “Calibrate the Sun”
9 Muon Capture, Big Picture + p + d + 3 He { g P, g A, ChPT } { g P, g A, ChPT, L 1A, a nn }{ g P, g A, hybrid EFT, L 1A, 3N} Final MuCap 2-3x improvement Combined analysis
10 Experimental Strategy Two main conditions n Unambiguous physics interpretation Muon kinetics optimization of D 2 conditions Very high precision d to 1.2% (5 s -1 ) Statistics: several events Systematics !
11 Muon Kinetics Collisional processes density dependent, e.g. hfs transition rate from q to d state = qd density normalized to LH 2 density complicated, can one extract fundamental weak parameters ? Muon-catalyzed Fusion q d qd q d
12 Optimize Muon Kinetics n Time Distributions Sensitivities ( d 1%, x 2 x ) d( ) d( ) He dd MuCapMuSun
13 Use Basic MuCap Technique n Lifetime method →e decays measure to 10ppm, d = 1/ - 1/ to 1% n Unambiguous interpretation at optimized target conditions n Ultra-pure gas system and purity monitoring at 1 ppb level Clean stop definition in active target (TPC) n 3 times higher rate with Muon-On-Request (MuLan) log(counts) t e -t μ+μ+ μ – d reduces lifetime by → e MuCap TPC top TPC side
14 Experiment Overview Experiment Overview PC SC ePC2 ePC1 eSC Cryo-TPC e
15 Observables n Observables in MuSun experiment decay electrons main observable fusion and capture essential as kinetics and background monitors n Experience from MCF experiments N capture
16 Cryo-TPC Design Criteria n Recombination n Drift Velocity n Equation of State n Specs
17 Cryo-TPC Design
18 Technical Design Cryo-System Vibration free cooling Continuous cleaning
19 Detectors and DAQ n Cryo-TPC special n Other detectors/infrastructure from MuCap detectors as impurity monitor n DAQ from MuCap/MuLan n 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) before lossless compression 2006 BU digitizer
20 Statistics + Systematics d (Hz) -- Statistics3.4 Systematics3.3 ++ from MuLan0.455 total d uncertainty 4.8 Hz 1.2 % d 10.5 ppm 1.8 events
21 Pad Optimization in Progress n Muon stop parameters Fake stops by +p scattering n Fusion interference GEANT 10x10 pad MuCap TPC GEANT
22 Gas Purity n Circulating Hydrogen Ultrahigh Purification System (CHUPS) US CRDF 2002, 2005 n New: cryo-TPC cryo filter before TPC continuous getter in gas flow for gas chromatography n Particle detection in TPC much harder – fusion for MuSun – signal 1 MeV excellent TPC resolution full analog readout tags – p after capture – X-ray protium measurement Rare impurity capture: d + Z d + Z (Z-1)* + MuCap achieved: ~ 10 ppb purity and 0.1 ppb purity monitoring MuSun needs: ~ 1 ppb purity or 0.5 ppb purity monitoring (Z-1)* +
23 Measuring Program n Stage 1 – 300 K TPC Rebuild (spare) MuCap TPC as ionization chamber Energy resolution Identification and separation of fusion recoils Full analog readout Measure d → Z transfer rate Optimize N capture monitor with dedicated setup n Stage 2 – Cryo-TPC ? 6 Ready Fall 08 Ready Fall runs in total (prep. and data taking) 4 years
24 Responsibilities & Budget n Budget estimates Total new equipment 350k CHF Annual running costs100k CHF Heavily based on larger investments made for MuCap/MuLan n Already positive response from main funding agencies National Science Foundation, USA Russian Academy of Sciences, Russia n Full funding requests to agencies after PAC approval