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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)





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



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