1
Search for η′ mesic nuclei in GSI/FAIR
Y. Ayyad, J. Benlliure, K.-T. Brinkmann, S. Friedrich, H. Fujioka**, H. Geissel, J. Gellanki, C. Guo, E. Gutz, E. Haettner, M. N. Harakeh, R. S. Hayano, Y. Higashi, S. Hirenzaki, C. Hornung, Y. Igarashi, N. Ikeno, K. Itahashi*, M. Iwasaki, D. Jido, N. Kalantar-Nayestanaki, R. Kanungo, R. Knoebel, N. Kurz, V. Metag, I. Mukha, T. Nagae, H. Nagahiro, M. Nanova, T. Nishi,H. J. Ong, S. Pietri, A. Prochazka, C. Rappold, M. P. Reiter, J. L. R. Sánchez, C. Scheidenberger, H. Simon, B. Sitar, P. Strmen, B. Sun, K. Suzuki, I. Szarka, M. Takechi, Y. K. Tanaka, I. Tanihata, S. Terashima, Y. N. Watanabe, H. Weick, E. Widmann, J. Winfield, X. Xu, H. Yamakami, J. Zhao
*spokesperson, ** co-spokesperson !
!for Super-FRS collaboration
!Osaka University, Universidade de Santiago de Compostela, Universitaet Giessen, Kyoto University, GSI, University of Groningen, Beihang University, The University of Tokyo, Nara Women's University, KEK, RIKEN, Tokyo Metropolitan University, Saint Mary’s University, Technische Universitaet Darmstadt, Comenius University Bratislava, Stefan Meyer Institut, Niigata University
Nagahiro, Jido, Fujioka, KI, Hirenzaki, PRC87(13)045201. KI, Fujioka et al., PTP 128 (12) 601.
Kenta Itahashi Advanced Meson Science Laboratory, RIKEN
for η-PRiME collaboration
RIKEN Nishina Center, Kenta Itahashi 2
M=548 MeV/c2
M=498 MeV/c2
M=140 MeV/c2
0
250
500
750
1000
[MeV/c2]
η′
η′ and other PS mesons
ηK
π
M=958 MeV/c2
RIKEN Nishina Center, Kenta Itahashi 3
M=140 MeV/c2
0
250
500
750
1000
[MeV/c2]η′ and other PS mesons
π
M=958 MeV/c2
mη′ < √3mπ (Weinberg, 1975)
√3mπ
η problem
η′
RIKEN Nishina Center, Kenta Itahashi 4
Kobayashi, Maskawa, PTP44(70)1422 ‘t Hooft, PRD14(76)3432.
T. Kunihiro, Phys. Lett. B219(89)363. Klimt, Lutz, Vogl, Weise, NPA516(90)429.
Large η′ mass can be explained
�q̄q�
q
q̄
q̄
q
timeKobayashi-Maskawa-’t Hooft-type interaction
UA(1) quantum anomaly × χ-symmetry breaking
6-point vertex
5
η′ Meson
Hirenzaki
6
0
250
500
750
1000
[MeV/c2]
η′
η
K
π
In-medium PS mesonsPartial restoration of dynamical breaking of χ symmetry
Nagahiro et al., PRC 87 (2013) 045201 Jido et al., NPA 914 (2013) 354
Nagahiro et al, PRC 74, 045203 (2006)
ρ/ρ0
NJL model
7
0
250
500
750
1000
[MeV/c2]
η′
η′ mesic nuclei search
11CQ. Mass shift of
~ 150 MeV/c2 can be observed in experiment?
Naive estimation shows 30% reduction
of |mη′−mη|
30 %
Jido, Nagahiro, Hirenzaki, PRC85(2012)032201(R)
η
η′
8
η′ Mesic Nuclei in (p,d) Reaction
η′ × 11C mesic nuclei
12C η′ 11C
η′ transfer reaction + missing mass measurement
Tp = 2.50 GeV → q ~ 400 MeV/c
KI, Fujioka et al., PTP 128 (12) 601.
9
Theoretical Prediction
Nagahiro et al., PRC87(13)045201.
η′-nucleus potential:
12C(p,d) at Tp = 2.50 GeV
ρ: nucleon density V0: Real potential depth
W0: Imaginary potential depth
10
p dη′Signal
Spectrum in Inclusive Measurement at GSI
12C(p,d)11C ⊗ η′
Nagahiro et al., PRC87(13)045201.
11
p dη′
p d
ππ
π
12C(p,d)11C ⊗ η′
Background
Signal
Spectrum in Inclusive Measurement at GSI
)=<(150, 5) MeV0
, W0
(V
Excitation Energy [MeV]-40 -20 0 2
cou
nts/
2MeV
260000
265000
270000
275000
280000
285000
0
multi-π
BK
Simulation
KI, Fujioka et al., PTP 128 (12) 601.
ρ0
ρ(r) Vη’ = (V0+iW0)
V0, W0 : real, imaginary part of optical potential
)=−(150, 5) MeV0, W0(V
)=−(150, 10) MeV0, W0(V
)=−(150, 20) MeV0, W0(V
Excitation Energy [MeV]-40 -20 0 20
)=−(100, 5) MeV0, W0(V
)=−(100, 10) MeV0, W0(V
)=−(100, 20) MeV0, W0(V
Excitation Energy [MeV]-40 -20 0 20
coun
ts/2M
eV
260
265
270
275
280
285 )=−(200, 5) MeV0, W0(V×103
coun
ts/2M
eV
260
265
270
275
280
285 )=−(200, 10) MeV0, W0(V
Excitation Energy [MeV]-40 -20 0 20
coun
ts/2M
eV
255
260
265
270
275
280
285 )=−(200, 20) MeV0, W0(V
background (e.g.,p+N→d+πʼ’s)
285000
280000
275000
270000
265000
260000
285000
280000
260000
coun
ts/2
MeV
275000
270000
265000
285000
280000
coun
ts/2
MeV
255000
260000
275000
270000
265000
-40 0-20 20 -40 0-20 20 -40 0-20 20Excitation Energy [MeV] Excitation Energy [MeV] Excitation Energy [MeV]
Simulation
ηʼ’ production
coun
ts/2
MeV
Simulated spectra of inclusive measurement assuming 4.5 day DAQ
!S/N ratio ~ O(1/100) at most
K. Itahashi et al., PTP 128,601(2012)
(V0 = Δm(ρ0), W0 = −Γ(ρ0) / 2)
Simulation of inclusive measurement
13
Excitation Energy [MeV]-40 -20 0 20
)=<(100, 20) MeV0
, W0
(V
cou
nts/
2MeV
255000
260000
265000
270000
275000
280000
285000
60 80 100 120 140 160 180 200
6
8
10
12
14
16
18
20
0
10
20
30
40
50
60
70
80
90
100
|VԾ| [MeV]
|WԾ|
[MeV
]
Structure-finding Probability
for 95 % C.L.
in 4.5 days DAQ
)=<(150, 5) MeV0
, W0
(V
Excitation Energy [MeV]-40 -20 0 2
cou
nts/
2MeV
260000
265000
270000
275000
280000
285000
0
14
-50-100-150
-10
-20
V0 [MeV]
W0 [MeV](=-Γ/2)
NJL linear σ QMC
COSY-11
0
chiralunitary
theory
exp. (η′A int.)exp. (η′N int.)
COSY-11
CBELSA/TAPS
COSY-11
Structure-finding Probability for First Step (GSI)
H. Fujioka
15
6080100120140160180200
6
8
10
12
14
16
18
20
-50-100-150
-10
-20
V0 [MeV]
W0 [MeV](=-Γ/2)
NJL linear σ QMC
COSY-11
0
chiralunitary
theory
exp. (η′A int.)exp. (η′N int.)
COSY-11
CBELSA/TAPS
COSY-11
Structure-finding Probability for First Step (GSI)
H. Fujioka
NUSTAR 2015
16
Measurement Objectives S/N
GSI step 1
(p,d) inclusive
extremely good statistics for overall structure + BK study poor
GSI/FAIR step 2
(p,dp) exclusive*
extended sensitivity for excited + ground states good
FAIR step≧2
(p,dx) exclusive*
exclusive + decay mode studies good
Step-by-step approach
17
p
p
d
d
d
η
p
π
p
N
Background
Principles of Exclusive Measurement at GSI/FAIR
Signals
p d
ππ
π
pη′→pη
Nη′→pπ
η′NN→pN
p dη′Signal
NUSTAR 2015
18
Measurement Objectives S/N
GSI step 1
(p,d) inclusive
extremely good statistics for overall structure + BK study poor
GSI/FAIR step 2
(p,dp) exclusive*
extended sensitivity for excited + ground states good
FAIR step≧2
(p,dx) exclusive*
exclusive + decay mode studies good
Step-by-step approach
19
First step Inclusive measurement GSI SIS-S437 in 2014/Aug
C target12 (4 g/cm )2
MWDC×2
SC
Aerogel Cherenkov (AC)
20
d ~ 4 k/spill at S4 (signal)
Scintillator (SC)
ACS4
S2
p beam (Tp = 2.5 GeV)
p′~ 800 k/spill at S4 (background)
Fragment Separator (FRS)
18m
Achromatic
Dispersive (3.6cm/%)
Production setup at FRS
C target12 (4 g/cm )2
MWDC×2
SC
Aerogel Cherenkov (AC)
21
d ~ 4 k/spill at S4 (signal)
Scintillator (SC)
ACS4
S2
p beam (Tp = 2.5 GeV)
p′~ 800 k/spill at S4 (background)
Fragment Separator (FRS)
18m
Achromatic
Dispersive (3.6cm/%)
Production setup at FRS
perfect PID
MWDC Analysis
time[day]2 3 4 5 6 7 8
drift
lengt
h [m
m]
0.5
0.55
0.6
0.65
0.7
0.75
0.8
- MWDC(XX’XX’UU’VV’)×2 were used. !- Tracking : drift time (measured) → drift length → χ2 fitting for 2 MWDCs !- Iterative analysis for calibration : temporary drift length → tracking → evaluate and update drift length !- Time dependence of relation between drift time and drift length !!
Drift length calibration
Aug
. 2
0:0
0
Aug
. 4
for drift time=1555 (TDC channel)
14001420 1440 14601480 1500 15201540 1560 15801600-3
-2
-1
0
1
2
3
Drift Time [channel]
Drift
Leng
th [m
m]
Measured drift time [TDC channel]
Eval
uate
d dr
ift le
ngth
[m
m]
Dri
ft le
ngth
[m
m]
Time dependence of drift time to drift length relation
Aug
. 3
Aug
. 5
Aug
. 6
Aug
. 7
Aug
. 8
~1day
22
-100 -50 0 50 100Eex - E0 [MeV]
0%
FRS scaling -2%
+2%
23
Production run (~ 5 days) - 7 settings of FRS Bρ from -2% to 2% → -90 MeV < Eex-E0 < +40 MeV covered - spectrometer calibration every 6 hours
Region in excitation energy
Spectrometer settings for wide mass region
CD2 target(1 g/cm )2
24
d (Pd = 2.82 GeV/c) ~mono-energetic at 0 degree
S4
S2
p (Tp = 1.6 GeV )
Calibration Run
D(p,d)p elastic scattering for ~mono-energetic d
Fragment Separator (FRS)
dispersive (3.6cm/%)
18m
a
X at Focal Plane [mm]-100 -50 0 50 100
Cou
nt
0
1000
2000
3000
4000
5000
6000
as4cor_xFocal plane position (online, ion-optics roughly corrected)
! - energy loss and straggling calculation - spectrometer momentum resolution - beam momentum spread
σX = 2.7 mm (CD2 calibration run)
preliminary
Expected mass resolution : σ ~ 2 MeV/c2 (production run) 25
FRS scaling by -2%
0%
2%
1%
-1%
Calibration Run
26
MM-M(11C)-M(etaprime) [MeV/c2]-150 -100 -50 0 50 100 1500
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
Sample spectrum of a very small part of accumulated data
~ 1 % of statistics for a FRS setting.
Acceptance uncorrected
12C(p,d) Td = 2.5 GeV
run864
)=<(150, 5) MeV0
, W0
(V
Excitation Energy [MeV]-40 -20 0 2
cou
nts/
2MeV
260000
265000
270000
275000
280000
285000
0
cf. simulation
coun
ts /
2 [M
eV/c
2 ]preliminary
NUSTAR 2015
27
Measurement Objectives S/N
GSI step 1
(p,d) inclusive
extremely good statistics for overall structure + BK study poor
GSI/FAIR step 2
(p,dp) exclusive*
extended sensitivity for excited + ground states good
FAIR step≧2
(p,dx) exclusive*
exclusive + decay mode studies good
Step-by-step approach
28Proton Kinetic Energy [MeV]
0 100 200 300 400 500 600 700 8000
10
20
30
40
50
60
70
80
90
100310×
Y.K. Tanaka and Y. Higashi
η′p→ηpη′p→πp
η′p→ππp η′pN→pN
p
p
d
d
d
η
p
π
p
N
Signals
Tagging high-momentum protons (300-600 MeV)
pη′→pη
Nη′→pπ
η′NN→pN
Principles of Exclusive Measurement at GSI/FAIR
29
MWDCD1 D4
D3D2
Target 12C 20 g
Scintillators
10cm
1cm-thick PS
high-refractive-index (n~1.2) aerogelbrass
5cm-thick PS
10cm
1cm-thick PS
high-refractive-index (n~1.2) aerogel
brass
5cm-thick PS
Beam Tp = 2.5 GeV Ip > 108/spill
10cm
1cm-thick PS
high-refractive-index (n~1.2) aerogel
brass
5cm-thick PS
beam dump trigger~400/spill
bk 80k/spill
p d
ππ
π
Background suppression by signal tagging
For next step
Pilot run for exclusive measurement at GSI
p
p
d
d
d
η
p
π
p
N
30
Roadmap for η′
2015 2020 2025
S437 analysis
Construction of proton detector
Better stat./Pilot exclusive measurement
Detector test
Production exclusive measurement
4pi detector development
4pi installation
Systematic study Decay mode study
10cm
1cm-thick PS
high-refractive-index (n~1.2) aerogel
brass
5cm-thick PS
FAIR GSI
unofficial roadmap (or wishes)
31
Summary
• Search for η′ meson bound states in 11C by missing mass
spectroscopy at GSI/FAIR • η′ is interesting in relation to UA(1) anomaly × χ-symmetry • Just finished first physics run for inclusive (p,d) • PID perfect • Successfully accumulated targeted statistics with good
resolution ~ 2 MeV/c2 • Preparation for semi-exclusive measurement