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

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Peter kammel for the musun collaboration

Peter Kammel

for the MuSun Collaboration

Muon Capture on the Deuteron The MuSun Experiment

BV39, Feb 21, 08


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
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 n theory
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




    L1A, dR

    M d experiment
    m + d Experiment





    • 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
    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
    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 l 1a d r

    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
    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


    Experimental strategy
    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
    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








    complicated, can one extract fundamental weak parameters ?

    Optimize muon kinetics
    Optimize Muon Kinetics

    • Time Distributions

    • Sensitivities (Ld 1%, lx  2 sx)







    Use basic mucap technique
    Use Basic MuCap Technique

    m → enn

    Ldreduces lifetime by 10-3





    μ –


    • 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)



    Experiment overview
    Experiment Overview










    • 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


    5 105

    Technical design cryo system
    Technical Design Cryo-System

    Vibration free cooling

    Continuous cleaning

    Detectors and daq
    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


    BU digitizer

    Statistics systematics
    Statistics + Systematics

    1.81010 events

    Pad optimization in progress
    Pad Optimization in Progress

    • Muon stop parameters

    • Fake stops by m+p scattering

    • Fusion interference

    GEANT 10x10 pad


    MuCap TPC

    Gas purity
    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
    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


    Ready Fall 08

    Ready Fall 09

    2-3 runs

    in total (prep. and data taking) 4 years

    Responsibilities budget
    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