1. (Yamagata University) for COMPASS++/AMBER working group
Proton radius measurements with a high energy muon beam in the future CERN experiment
Firstly, I’d like to thank the organizers
for inviting me to give a talk.
The title of my talk is
“Experimental study with lepton scattering.”
I’ll review the recent progress
in the study of the nucleon structure
in lepton scattering experiments.
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
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
Takahiro IWATA, workshop , ELPH Tohoku University

3. Proton radius puzzle This is the outline of my talk.
The values for the proton charge radius measured with
electrons(ep & hydrogen) : ± fm muons (muonic hydrogen) : ± fm
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
arXiv:
Is it related to the violation of universality between electron and muon?
The missing piece is the muon scattering.
Takahiro IWATA, workshop , ELPH Tohoku University

4. Elastic electron(muon)-proton scattering
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
Takahiro IWATA, workshop , ELPH Tohoku University

5. Experimental method This is the outline of my talk.
precise measurement of GE(Q2) in the rage of Q2 as small as possible
extrapolation towards zero  slope at Q2=0
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
recent MAMI results
Takahiro IWATA, workshop , ELPH Tohoku University

6. New experiments This is the outline of my talk.
electrons ( GeV region, single arm): MAMI, Jlab
electrons ( GeV region, proton recoil): MAMI/GSI/PNPI using active target
electrons ( MeV ): ELPH
low energy muons ( MeV):
New idea  high energy muons ( GeV)
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
Takahiro IWATA, workshop , ELPH Tohoku University

7. Advantages of high-energy m beam
much reduced radiative corrections compared to electrons
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
much smaller Coulomb corrections compared to low energy muons
correction depending on scattering angle
small scattering angle at higher energies
Takahiro IWATA, workshop , ELPH Tohoku University

8. COMPASS at CERN - Here is the recent result for the Collins Asymmetry
obtained for proton target,
for positive and negative pions.
What we can see here is
non-zero signal is clearly visible.
Takahiro IWATA, workshop , ELPH Tohoku University

9. COmmon Muon Proton Apparatus for Structure and Spectroscopy
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
COMPASS is the similar experiment,
which is currently running at CERN.
using high energy polarized muon beam
with the energy up to 200GeV
and the polarized solid target.
Thanks to the multi-purpose spectrometer,
SI-DIS events are also measured.
Takahiro IWATA, workshop , ELPH Tohoku University

10. COMPASS at CERN COMPASS is the similar experiment,
which is currently running at CERN.
using high energy polarized muon beam
with the energy up to 200GeV
and the polarized solid target.
Thanks to the multi-purpose spectrometer,
SI-DIS events are also measured.
Takahiro IWATA, workshop , ELPH Tohoku University

11. The M2 beam line for COMPASS
Hadron absorber
(only for m beam)
Beryllium target
p (400 GeV)
p, K, p
naturally polarized m+/-(<200 GeV)
hadrons+/- (< 200GeV)
SPS
Secondary particles
p / p dominant
~600m decay pipe
positive muon case
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
components of the hadron beam
NIM A779(2015)69-115
NIM A577(2007)
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
Takahiro IWATA,
Nucleon Structure, , 2, 20-21, Sagae, Yamagata, Japan

12. Setup for muon program DIS & SI-DIS setup
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)
COMPASS is the similar experiment,
which is currently running at CERN.
using high energy polarized muon beam
with the energy up to 200GeV
and the polarized solid target.
Thanks to the multi-purpose spectrometer,
SI-DIS events are also measured.
E/HCAL
E/HCAL
SM1
SM2
MuonWall
Pol.
beam
fom SPS
GeV,
pol. = 80%
RICH
two stage spectrometer
tracking, calorimetry, PID
Takahiro IWATA, workshop , ELPH Tohoku University

13. Setup for muon program in detail
COMPASS is the similar experiment,
which is currently running at CERN.
using high energy polarized muon beam
with the energy up to 200GeV
and the polarized solid target.
Thanks to the multi-purpose spectrometer,
SI-DIS events are also measured.
Takahiro IWATA, workshop , ELPH Tohoku University

14. Data taking 2002 - 2021 2002 muon program with 160 GeV pol. muon d↑ p↑
LiD pol. target (d) L-mode: 80 / T-mode: 20
2005 no data taking
NH3 pol. target (p) 160 GeV pol. muon L: 50 / T: 50
2008, 09 hadron program with 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(-)
2021 muon program with 160 GeV pol. muon with LiD pol. target
END of COMPASS d↑ p↑ p↑ p↑
punpol p↑ d↑
Takahiro IWATA
JPS meeting, 2019, March , Kyushu University

15. “A new QCD facility at the M2 beam line of the CERN SPS”
COMPASS++/AMBER
“A new QCD facility at the M2 beam line of the CERN SPS”
Letter of intent : arXiv: v3 [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
Here is the recent result
for the Collins Asymmetry
obtained for proton target,
for positive and negative pions.
What we can see here is
non-zero signal is clearly visible.
Takahiro IWATA, workshop , ELPH Tohoku University

16. Plans for the proton radius measurement -
Here is the recent result
for the Collins Asymmetry
obtained for proton target,
for positive and negative pions.
What we can see here is
non-zero signal is clearly visible.
Takahiro IWATA, workshop , 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
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
Takahiro IWATA, workshop , ELPH Tohoku University

18. Proposed setup This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
hydrogen TPC as active target
silicon telescopes　with 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 , ELPH Tohoku University

19. Active hydrogen TPC target
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
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 , 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 % up　to 100 MeV
stereo angle of 6 degree for 3D information
readout by SiPM( Hamamatsu S or KETEK PM3325)
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
Takahiro IWATA, workshop , ELPH Tohoku University

21. Goal of measurement This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
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 , ELPH Tohoku University

22. TPC test with muon beam in 2018
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
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 , ELPH Tohoku University

23. Test setup in 2018 This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
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 , ELPH Tohoku University

24. TPC structure This is the outline of my talk.
sensitive region
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
Gas: H2
Pressure: p=1,4,8 bar
LCG=220 mm
VC=18 kV, VG=1 kV
tCG ~ 60 us
Takahiro IWATA, workshop , ELPH Tohoku University

25. Preliminary results This is the outline of my talk.
reconstructed vertices from silicon telescope tracks
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
z-cut: +24cm > z > +45 cm (active region)
only tracks pass through TPC windows
z-resolution about 3 cm
Takahiro IWATA, workshop , ELPH Tohoku University

26. Preliminary results This is the outline of my talk.
time difference: SI – TPC
width: 60 us = drift time
This is the outline of my talk.
Following a brief introduction.
I’ll talk about these topics;
Longitudinal Spin Structure
Transverse Spin Effects
GPD Studies
C.Dreisback, COMPASS collaboration meeting ( )
Takahiro IWATA, workshop , ELPH Tohoku University

27. Timelines Here is the recent result for the Collins Asymmetry
proton radius measurement ?
NOW
Here is the recent result
for the Collins Asymmetry
obtained for proton target,
for positive and negative pions.
What we can see here is
non-zero signal is clearly visible.
Long-term plan
by new collaboration
COMPASS++/AMBER
Short-term plan
by COMPASS
Takahiro IWATA,
Nucleon Structure, , 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.
Now, let me conclude my talk.
Significant progress in the study　with lepton scattering was achieved
Du and Dd are well determined
Polarized sea distributions are small
Gluon polarization is compatible with 0 in the measured range
Transversity and Sivers PDF have been extracted
The asymmetry on un-polarized nucleon gives a hint of BM PDF
Wealth of GPD data were accumulated by HERMES and Jlab-experiments
Exciting GPD programs at COMPASS-II and JLab-12GeV are planned
Takahiro IWATA, workshop , ELPH Tohoku University

29. Spares Firstly, I’d like to thank the organizers
for inviting me to give a talk.
The title of my talk is
“Experimental study with lepton scattering.”
I’ll review the recent progress
in the study of the nucleon structure
in lepton scattering experiments.
Hadron China 2017, 24-28, 2017, Nanjing

30. Scattering angle v.s. Q2 Here is the recent result
for the Collins Asymmetry
obtained for proton target,
for positive and negative pions.
What we can see here is
non-zero signal is clearly visible.
Takahiro IWATA, workshop , ELPH Tohoku University