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Proton radius measurements with a high energy muon beam in the future CERN experiment

Proton radius measurements with a high energy muon beam in the future CERN experiment. Takahiro Iwata, (Yamagata University) for COMPASS++/AMBER working group. Workshop, 2019/3/20-21, 25-30, ELPH Tohoku University. OUTLINE. Introduction: Proton radius puzzle COMPASS at CERN

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Proton radius measurements with a high energy muon beam in the future CERN experiment

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  1. Proton radius measurementswith a high energy muon beamin the future CERN experiment Takahiro Iwata, (Yamagata University) for COMPASS++/AMBER working group Workshop, 2019/3/20-21, 25-30, ELPH Tohoku University

  2. OUTLINE • Introduction: Proton radius puzzle • COMPASS at CERN • COMPASS++/AMBER • Plans for proton radius measurement • Experimental challenges • Proposed set-up • 2018 test measurements Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  3. Proton radius puzzle The values for the proton charge radius measured with electrons(ep & hydrogen) : 0.8751 ±0.0061 fm muons (muonic hydrogen) : 0.8409 ±0.0004 fm arXiv:1706.00696 Is it related to the violation of universality between electron and muon? The missing piece is the muon scattering. Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  4. Elastic electron(muon)-proton scattering Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  5. Experimental method • precise measurement of GE(Q2) in the rage of Q2 as small as possible • extrapolation towards zero  slope at Q2=0 recent MAMI results Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  6. New experiments • electrons ( GeV region, single arm): MAMI, Jlab • electrons ( GeV region, proton recoil): MAMI/GSI/PNPI using active target • electrons ( 20-60 MeV ): ELPH • low energy muons (100-200 MeV): MUSE@PSI • New idea  high energy muons (50-200 GeV) Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  7. Advantages of high-energy m beam • much reduced radiative corrections compared to electrons • much smaller Coulomb corrections compared to low energy muons • correction depending on scattering angle • small scattering angle at higher energies Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  8. COMPASS at CERN - Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  9. COMPASS COmmon Muon Proton Apparatus for Structure and Spectroscopy • About 230 physicists from 13 countries • To study hadron structure and spectroscopy • Using the secondary beam from SPS at CERN • With the versatile common spectrometer Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  10. COMPASS at CERN Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  11. The M2 beam line for COMPASS Hadron absorber (only for m beam) Beryllium target p (400 GeV) naturally polarized m+/-(<200 GeV) p, K, p hadrons+/- (< 200GeV) SPS Secondary particles p / p dominant ~600m decay pipe positive muon case components of the hadron beam NIM A779(2015)69-115 NIM A577(2007) 455-518 NB:hadrons can be tagged by a differential Cherenkov counter installed in the beam line NB:nominal spill 4.8s within a 16.8 s long SPS cycle ＝＞　instantaneous muon flux : 4x107/s Nucleon Structure, 2019, 2, 20-21, Sagae, Yamagata, Japan

  12. Setup for muon program Straws SDC MWPC W45 DIS & SI-DIS setup with muon beam & polarized target SciFi Silicon Micromegas GEMs MuonWall Polarised Target (NH3 for p, 6LiD for d) E/HCAL E/HCAL SM2 SM1 MuonWall Pol. • beam fom SPS 160-200 GeV, pol. = 80% RICH two stage spectrometer tracking, calorimetry, PID Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  13. Setup for muon program in detail Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  14. Data taking 2002 - 2021 • 2002 muon program with160 GeV pol. muon • 2002-066LiD pol. target (d) L-mode: 80 / T-mode: 20 • 2005 no data taking • 2007NH3 pol. target (p) 160 GeV pol. muon L: 50 / T: 50 • 2008, 09 hadron programwith p/p/K beam at 190 GeV • 2010 NH3 pol. target (p/T-mode) 160 GeV pol. muon • 2011 NH3 pol. target (p/L-mode)200 GeV pol. muon • 2012 hadron program & GPD pilot run • 2013 GPD-program with muon beam & LH2 target • 2014 DY-pilot run • 2015 DY prog. with NH3 pol. target (p/T-mode)190 GeV pion(-) • 2016 GPD-program with muon beam & LH2 target • 2017 GPD-program with muon beam & LH2 target • 2018 DY prog. with NH3 pol. target (p/T-mode)190 GeV pion(-) • 2021muon program with 160 GeV pol. muon with LiD pol. target • END of COMPASS d↑ p↑ p↑ p↑ punpol p↑ d↑ JPS meeting, 2019, March. 14-17, Kyushu University

  15. COMPASS++/AMBER “A new QCD facility at the M2 beam line of the CERN SPS” Letter of intent : arXiv:1808.00848v3 [hep-ex] 15 Oct 2018 Proposal to be submitted in 2019 Proton radius measurement with a muon beam hadron physics with standard muon and hadron beams hadron physics with RF-separated hadron beams Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  16. Plans for the proton radius measurement - Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  17. Elastic muon-proton scattering measurement • scattering of high energy muons off proton target • measurement of Q2 dependence of elastic cross section • no GE-GM separation possible at high energies  GE2+tGM2 measured • At small values of Q2(i.e. small t) of interest, contribution from GM is small • experimental challenges : identify elastic reaction at very low Q2 • very small scattering angles( ～ 100 m rad) and energy same as incoming energy • low energy recoil proton with angles of about 90 degree • experimental requirements • detection of muon with very low scattering angles • muons at scattering angle > 100 m rad (10-4 (GeV/c)2 ) are selected • muons at scattering angle < 5 mrad (99% ) are vetoed to suppress triggers • detection of recoil proton with low energy • active proton TPC target mandatory at least for low Q2 < 0.02 (GeV/c)2 • SciFi detector inside TPC volume for higher Q2> 0.02 (GeV/c)2 Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  18. Proposed setup ~10m • hydrogen TPC as active target • silicon telescopeswith resolution < 10um up- and downstream of target • muon ID provided by the spectrometer • trigger on recoil proton and kink in muon track Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  19. Active hydrogen TPC target • high pressure hydrogen TPC developed by PNPI (Gat china) • measurement of recoil proton energy ( resolution 60keV) • necessary rage from 0.5 MeV to 100 MeV (Q2>10-4 (GeV/c)2) • use different pressure from 4 to 20 bar Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  20. SciFi detector in TPC volume • At higher Q2( > 0.02 (GeV/c)2), recoiling protons do not stop in TPC • SciFi detector installed in gas volume of TPC inner layers : 2 mm x 2mm outer layers: 4 mm x 4mm to 8 mm x 8 mm dE/dx, E analysis available energy resolution of a few % upto 100 MeV stereo angle of 6 degree for 3D information readout by SiPM( Hamamatsu S13360-3025 or KETEK PM3325) Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  21. Goal of measurement • assuming one year of data taking (at least 2x106 muons/s ) • measurement between 10-3(GeV/c)2 < Q2 < 0.1(GeV/c)2 TPC :10-3 < Q2 < 0.02(GeV/c)2 SciFi : 0.02 < Q2 < 0.1(GeV/c)2 • Q2 resolution : DQ2 =1.4x10-4 (GeV/c)2 • goal : uncertainty of √　<rE2> is 0.01 fm Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  22. TPC test with muon beam in 2018 • Study TPC performance with the muon beam • TPC between 4 tracking stations downstream COMPASS-DY setup • Tracking via Si microstrip detectors ( Dx ~ 10 um) • Muon beam : Em= 190 GeV, sxxsy=81x84 mm, up to 2 MHz Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  23. Test setup in 2018 • Trigger scintillators (BT) 64x48 mm x3 • Si microstrip detectors (SI) 70 x 40 mm x 4(XY) • Short baseline (~4m) limits Q2~ 3x10-3 (GeV/c)2 • TPC as active target with D=200 mm Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  24. TPC structure sensitive region • Gas: H2 • Pressure: p=1,4,8 bar • LCG=220 mm • VC=18 kV, VG=1 kV • tCG ~ 60 us Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  25. Preliminary results reconstructed vertices from silicon telescope tracks z-cut: +24cm > z > +45 cm (active region) only tracks pass through TPC windows z-resolution about 3 cm Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  26. Preliminary results time difference: SI – TPC width: 60 us = drift time C.Dreisback, COMPASS collaboration meeting (15.11.2018) Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  27. Timelines proton radius measurement ? NOW Long-term plan by new collaboration COMPASS++/AMBER Short-term plan by COMPASS Nucleon Structure, 2019, 2, 20-21, Sagae, Yamagata, Japan

  28. Summary • Measurement in muon proton elastic scattering is a missing piece in order to solve the proton radius puzzle • A measurement with a high energy muon beam at CERN M2 beam line is proposed by the COMPASS++/AMBER. • The high energy muon beam gives advantages from the point of view of radiative correction and Coulomb correction. • Required active hydrogen TPC target is under development with the muon beam at CERN. • The measurement is expected to be done in 2022. Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

  29. Spares Hadron China 2017, 24-28, 2017, Nanjing

  30. Scattering angle v.s. Q2 Takahiro IWATA, workshop 2019 20-21, ELPH Tohoku University

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