MUSE: The MUon proton Scattering Experiment
Evangeline J. DownieOn behalf of the MUSE Collaboration
The George Washington UniversityWashington DC, USA
Award DE-SC0012485 Awards PHY-1309130 & 1314148
Motivation for Muon Scattering
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Previous e-μ Scattering Comparisons
Ellsworth et al. Phys. Rev. 165 (1968): form factors from elastic μp
Kostoulas et al. PRL 32 (1974) parameterization of μp vs. ep elastic differences
no difference
1970's & 80's several scattering ep & mp tests
Supported universality at 10% level
Insufficient precision to test proton radius issues
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Two-photon exchange tests in μp elastics
Camilleri et al. PRL 23: No evidence for two-photon exchange effects, but very poor constraints by modern standards.
No difference between μ+p and μ-p elastic scattering
Rosenbluth plot is linear.
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MUSE Experiment
Simultaneous measurement of e+/μ+ e-/μ- at beam momenta of 115, 153, 210 MeV/c in πM1 channel at PSI allows:
➔ Determination of two-photon effects
➔ Test of lepton universality
➔ Simultaneous determination of proton radius in both ep and μp scattering
rp(fm) ep mp
spectroscopy
0.877±0.007 0.841±0.0004
scattering 0.875±0.006 ?
rp(fm) ep mp
atom 0.8779 ± 0.0094 (Pohl)
0.84087 ± 0.00039
(Antognini)
scattering 0.879 ± 0.008 (Mainz)
0.875 ± 0.009 (JLab)
?
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Paul Scherrer Institute πM1 Beam
590 MeV proton beam, 2.2mA, 1.3 MW beam, 50.6 MHz RF frequency
World's most powerful proton beam
➔ Secondary e±, m±, p± in piM1 beamline
Separate out particle species by timing relative to beam RF
Cut as many pions as possible, trigger on e±, m±
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MUSE Experiment
Low beam flux
➔ Large angle, non-magnetic detectors
Secondary beam
➔ Tracking of beam particles to target
Mixed beam
➔ Identification of beam particle in trigger
θ ≈ 20o – 100o
Q2 ≈ 0.002 - 0.07 GeV2
3.3 MHz total beam flux
≈ 2-15% μ's
≈ 10-98% e's
≈ 0-80% π's
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Scintillating SiPM Detector Array (Tel Aviv, Rutgers, PSI)
Thin, fast, scint., double-ended SiPM readout
Beam PID by RF timing diff. (~50 ps RMS)
Beam flux, TOF for beam p & reaction ID
Position & time for correlations with GEMS.
GEM Chambers (Hampton)
Built for OLYMPUS
2 mr instrinsic resolution
< 10 mr resolution with mult. scattering
Already used in PiM1 beam tests
Beam Particle Tracking / Identification
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Veto Detector (USC)
Annular 8-element veto detector (target-mounted)
Eliminate upstream scattering & beam decays
Liquid Hydrogen Target (GWU)
Advanced conceptual design (below), 6cm “coffee can”
Geant 4 implementation (lower right)
Liquid Hydrogen Target (GWU) & Veto Detector (USC)
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Forward Beam Monitor Scintillators (USC)
Array of 32 thin scintillators
Read out by SiPMs
Flanked by large scintillators
Double-ended read out
(Un)Scattered Particle Tracking / IdentificationStraw Tube Tracker (HUJI & Temple)
Position/angular res. 140μm/1mr
2850 straws, directly mounted readout
First half-chamber tested
Trigger Scintillators (USC)
Two planes on each side of beam
92 bars, double-ended readout
55 ps achieved
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Back Wall Scintillator Time Resolution
55 ps average resolution
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Relative timing test,
s = 32 ps
Measured timing differences from 2014 PSI test beam time
Readout
TRB3: trb.gsi.de
DAQ system (GWU & Montgomery College)
3000 TDC, 500 ADC chanels
TRB3-based read-out
Mesytec MQDC-32 ADCs mostly for timing correction
Trigger (Rutgers)
TRB3 FPGA-based, accept e±, m±, reject p±
SiPM PID && Scattered Particle (LUT) && NOT(veto)
PID determined by time between RF pulse and SiPM
See Poster by I. Lavrukhin & C. Collicot 12
Mechanical Assembly (ANL & PSI)
Rotating table
Retractable beam tracker
Dedicated alignment procedures
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MUSE Test Beam Times
12 MUSE Test Runs
✔ to characterize piM1 beam
✔ to test detector prototypes (scintillators, Cerenkov, straw tubes)
✔ to study and optimize GEM performance
➔ Oct 2012➔ May 2013➔ July 2013➔ Oct 2013 (Cosmics)➔ Dec 2013➔ June 2014➔ Dec 2014➔ Feb 2015 (Cosmics)➔ June-July 2015➔ Dec 2015➔ May 2016
Representation from 13 institutions
12th run scheduled for June-July 201614
First Beam Tests
Time of flight relative to RF time(Fall 2012)
Beam spot with GEM – May 23, 2013
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Composition of the πM1 secondary beam
Beam test results fromDecember 2013
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3D Beam Tomography
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Simulations (USC)
Particle vertex and scattering angle reconstruction meet MUSE requirements
Background from target walls and windows can be cleanly eliminated or subtracted
Simulations verified by test data
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TOF Beam Momentum Measurement
In the simulation
✔ Use realistic beam profile
✔ Match to experimental time resolution
✔ Match to experimental particle flux
tsimulation
– texperiment
= D(tXcm
- t0cm
)
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TOF Beam Momentum Measurement
Consistent beam momenta were extracted from muon
and pion spectra
Good agreement between simulation and data, no evidence of beam tail from collimation
p(p) ≈ p(μ) with dp / p < 0.3%
Preliminary results meet specifications 20
Simulations (USC)
Muon decays in flight can be removed with time-of-flight measurements
Moeller/Bhabba events can be effectively suppressed with veto from the beamline monitor detector
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Top:
Geant 4 sims tuned to match measured beam parameters
Left:
Neural net seperates muon scattering from muon decay reactions
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Recent Results
MUSE measuring relative cross sections
Point-to-point uncertainties, most important
Uncertainties mostly well controlled: largest from angle and radiative corrections.
Have six settings and two independent detectors, consistency check
Multiple calibration measurements / simulations planned
MUSE Error Budget
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Scintillator efficiency 0.1%
Solid angle 0.1%
Beam momentum offset
0.1%
Theta offset 0.2%
Multiple scattering 0.15%
Muon decay in flight 0.1%
Radiative corrections 0.1% m; 0.5% e
Target wall subtraction 0.3%
Beam PID mis-ID 0.1%
Projected sensitivity for MUSE
Cross sections to < 1% stat. for backward μ, <<1% for forward e and μ, absolute 2%, point-to-point realtive uncertainties to a few x 10-3
Individual radius extractions from e±, μ± each to 0.01 fm
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linear
+Q6
+Q4
Projected sensitivity for MUSE
Compare e± xsecs and μ± xsecs for TPE. Charge average to eliminate TPEeach to 0.01 fm
From e/μ xsec ratios: extract e-μ radius difference with minimal truncation error to 0.005 fm
If no difference, extract radius to 0.007 fm (2nd-order fit)
25*Note: MUSE point arbitrarily put at r
p=0.875 fm
Projected sensitivity for MUSE
Charge radius extraction limited by systematics, fit uncertainties
Many uncertainties are common to all extractions in the experiments, cancel in e+/e-, μ+/μ-, and μ/e comparisons
MUSE suited to verify 5.6σ effect (CODATA 2014) with even higher significance
Re - R
μ = 0.034±0.006 fm (5.6σ), MUSE: δr = 0.005 fm (~7σ)
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Uncertainties on radius difference ~0.005 fm (stat.) ~0.1 fm (syst.)
*Note: Difference in MUSE determined entirely by MUSE. Other differences are taken with respect to Antognini muonic hydrogen radius.
MUon proton Scattering Experiment - MUSE 55 MUSE collaborators from 24 institutions in 5 countriesA. Afanasev, A. Akmal, J. Arrington, H. Atac, C. Ayerbe-Gayoso, F. Benmokhtar, N. Benmouna, J. Bernauer, A. Blomberg, E. Brash, W.J. Briscoe, E. Cline, D. Cohen, E.O. Cohen, C. Collicott, K. Deiters, J. Diefenbach, B. Dongwi, E.J. Downie, L. El Fassi, S. Gilad, R. Gilman, K. Gnanvo, R. Gothe, D. Higinbotham, Y. Ilieva, L. Li, M. Jones, N. Kalantarians, M. Kohl, G. Kumbartzki, I. Lavrukhin, J. Lichtenstadt, W. Lin, A. Liyanage, N. Liyanage, Z.-E. Meziani, P. Monaghan, K.E. Mesick, P. Moran, J. Nazeer, C. Perdrisat, E. Piasetzsky, V. Punjabi, R. Ransome, D. Reggiani, P.E. Reimer, A. Richter, G. Ron, T. Rostomyan, A. Sarty, Y. Shamai, N. Sparveris, S. Strauch, V. Sulkosky, A.S. Tadepalli, M. Taragin, and L. Weinstein
George Washington University, Montgomery College, Argonne National Lab, Temple University, College of William & Mary, Duquesne University, Massachusetts Institute of Technology, Christopher Newport University, Rutgers University, Hebrew University of Jerusalem,Tel Aviv University, Paul Scherrer Institut, Johannes Gutenberg-Universität, Hampton University, University of Virginia, University of South Carolina, Jefferson Lab, Los Alamos National Laboratory, Norfolk State University, Technical University of Darmstadt, St. Mary’s University, Soreq Nuclear Research Center, Weizmann Institute, Old Dominion University 27
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Ron consulted closely with wise, experienced project managers...
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MUon proton Scattering Experiment - MUSE
Since initial proposal in February 2012, 12 beam tests, and counting...
➔ Determine beam line properties
➔ Prototyped most of needed technology for the experiment
Series of NSF funding reviews: R & D funding from NSF, DOE, BSF
Successful funding and project management review concluded May 2016
NSF mid-scale funding should enable:
➔ Funding & construction 2016–2017
➔ Production running 2018–2019 (2x 6 months)
MUSE will be the first muon scattering measurement with the required precision to address the PRP! 29
Backup Slides
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Relative timing test, s = 32 ps
Readout
DAQ system (GWU & MC)
Multiple TRB3s running in synch with VMEs
Inter-TRB3 synch issues resolved
Trigger (Rutgers, Krakow, GW)
Trigger splitter time resolution tested
No significant difference in time resolution
● after splitting
without splitting
copy resolution
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George Washington & Rutgers work very closely together...
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