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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