1

Peter Kammel

for the MuSun Collaboration

Muon Capture on the Deuteron Muon Capture on the Deuteron The MuSun ExperimentThe MuSun Experiment

BV39, Feb 21, 08

2

CollaborationCollaboration

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

3

Goal and MotivationGoal and Motivation

+ d + d + n + n + n + n RateRate dd from from d(d() atom) atom

MeasureMeasure dd to < 1.5 %to < 1.5 %

Simplest weak interaction process in a nucleusSimplest weak interaction process in a nucleusallowing for precise theory & experiment allowing for precise theory & experiment

nucleon FF (gnucleon FF (gPP) from MuCap) from MuCap

model-independentmodel-independent calculations with effective field theorycalculations with effective field theory

Close relation to neutrino/astrophysicsClose relation to neutrino/astrophysics model-independent connection model-independent connection +d+d to pp fusion and to pp fusion and +d +d

reaction reaction

Broader Impact on modern nuclear physicsBroader Impact on modern nuclear physics

EFT relates EFT relates +d+d to strong processes like to strong processes like +d +d + n +n, a + n +n, annnn

4

+ d + d + n + n + n + n TheoryTheoryAxial current reaction

Gamow-Teller 3S1 1S0

one-body currents well definedFF, 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/m)

ChPT(q/)

• hybrid EFT (EFT operators, Pot.Model wavefct)

MEC

L1A, dR

EFT

5

+ d Experiment+ d Experiment Experimental Challenges

Dalitz Plot

Intensity at low Enn

ChPT covers most of DP

EFT only p< 90 MeV/c

→ e= 455162 s-1

dq,d → n+n+ q ~ 10 s-1, d = 400 s-1

d() + d→ d() + d

dd → 3He + n + rates ~

d

6

Precise Experiment NeededPrecise Experiment Needed

Potential Model + MEC

pionless, needs L1A

hybrid EFT

consistent ChPT

Determine L1A from clean system

Ramnifications for -astro physics

Quantify consistency of hybrid approach

7

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 +d capture via LEC L1A, dR

Muon capture soft enough to relate to solar reactions

Connection to Neutrino/AstrophysicsConnection to Neutrino/Astrophysics

with L1A ~ 6 fm3

8

Quest for LQuest for L1A1A, d, dRR

Precision +d experiment by far the best determination

of L1A in the theoretically clean

2-N system

“Calibrate the Sun”

9

Muon Capture, Big PictureMuon Capture, Big Picture

+ p

+ d + 3He

{ gP, gA, ChPT }

{ gP, gA, ChPT, L1A, ann } { gP, gA, hybrid EFT, L1A, 3N}

Final MuCap 2-3x improvement

Combinedanalysis

10

Experimental StrategyExperimental Strategy

Two main conditions

Unambiguous physics interpretation

Muon kinetics optimization of D2 conditions

Very high precision d to 1.2% (5 s-1)Statistics: several 1010 events

Systematics !

11

Muon KineticsMuon Kinetics

Collisional processes density dependent, e.g.

hfs transition rate from q to d state = qd

density normalized to LH2 density

complicated, can one extract fundamental weak parameters ?

Muon-catalyzed Fusion

q

d

qd

q

d

qd

12

Optimize Muon KineticsOptimize Muon Kinetics Time Distributions

Sensitivities (d 1%, x 2 x)

d()d()

He

d MuCap MuSun

13

Use Basic MuCap TechniqueUse Basic MuCap Technique Lifetime method

1010 →e 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 stop definition in active target (TPC)

3 times higher rate with Muon-On-Request (MuLan)

log

(co

un

ts)

te-t

μ+

μ –

d reduce

s lifetime by 10-3

→ e

MuCapTPCtop

TPCside

14

Experiment OverviewExperiment Overview

PC

SC

ePC2

ePC1

eSC

Cryo-TPC

e

15

ObservablesObservables Observables in MuSun experiment

• decay electrons main observable

• fusion and capture essential as kinetics and background monitors

Experience from MCF experiments

N capture

1.8 1010

109

5 105

16

Cryo-TPC Design CriteriaCryo-TPC Design Criteria Recombination Drift Velocity

Equation of State Specs

0

2

4

6

8

10

12

24 26 28 30 32 34 36

T (K)

p(b

ar)

SVP

10% LH25% LH2

2.5% LH27.5% LH2

liquid

gas

17

Cryo-TPC DesignCryo-TPC Design

Aluminum shell

Rear neon collector

Front neon collector

Be window flange Be window

18

Technical Design Cryo-SystemTechnical Design Cryo-System

Vibration free cooling

Continuous cleaning

19

Detectors and DAQDetectors and DAQ Cryo-TPC special

Other detectors/infrastructure from MuCap

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) before

lossless compression

2006

BU digitizer

20

Statistics + SystematicsStatistics + Systematicsd (Hz)

- Statistics 3.4

Systematics 3.3

+ from MuLan 0.455

total d uncertainty 4.8 Hz

1.2 % d

10.5 ppm

1.81010 events

21

Pad Optimization in ProgressPad Optimization in Progress Muon stop parameters

Fake stops by +p scattering

Fusion interference

GEANT 10x10 pad

MuCap TPC

GEANT

22

Gas PurityGas Purity

Circulating Hydrogen Ultrahigh Purification System (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 – 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 ProgramMeasuring 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 d → Z transfer rate

• Optimize N capture monitor with dedicated setup

Stage 2 – Cryo-TPC

? 6Ready Fall 08Ready Fall 09

2-3 runs

in total (prep. and data taking) 4 years

24

Responsibilities & BudgetResponsibilities & 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 agenciesNational Science Foundation, USA

Russian Academy of Sciences, Russia

Full funding requests to agencies after PAC approval