J-PARC での中性子過剰ラムダハイパー核生成実験

J-PARC での中性子過剰ラムダ
ハイパー核生成実験
Production of Neutron-Rich
L Hypernuclei at J-PARC
大阪大学理学研究科阪口篤志
Atsushi Sakaguchi
(Dep. of Physics, Osaka Univ.)
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
CR
Studies of L Hypernuclei

Hypernuclei (L hypernuclei)


Bound state of hyperon (L) and nuclei
How to study?

Emulsion and bubble chambers




Hypernucleus
weak
decay
Discovery by Danysz and Pniewski in CR
K- beams at CERN
LL: KEK-PS, (BNL-AGS), J-PARC, …
Missing-mass spectroscopy
(stopped K - ,  - ) ( K - ,  - )  feasibility
 CERN-PS
( K - ,  - ) (  , K  ) (stoped K - ,  0 )
 BNL-AGS
(stopped K - ,  - ) (  , K  )
 KEK-PS
(
stopped
K
,

)
 DAFNE
(e, eK  )
 JLAB, MAMI-C, …

J-PARC, …
2
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Missing-Mass Spectroscopy at CERN

Heidelberg-Saclay-Strasbourg Collaboration
SPES II
3
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Studies of L Hypernuclei (2)

How to study?

g-ray spectroscopy




Invariant-mass spectroscopy in HI collisions





CERN-PS (4LH, 4LHe)
BNL-AGS, KEK-PS
with missing-mass cut
can achieve good S/N
J-PARC, …
BNL-AGS
BNL-RHIC (discovery of anti-hypernuclei)
proton-rich L hypernuclei, …
GSI-SIS, FAIR, …
Weak decay of L hypernuclei
Achievement in experiments?


Production of identified hypernuclei
Better and better energy resolution
4
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Properties of L Hypernuclei

Single particle picture is OK




“Glue-like role” of L hyperon




L-N interaction is attractive
Possible to stabilize nuclei
Doorway to strange matter
Spin dependent interaction


Beautiful L shell structure
Deeply bound L state
Highly excited L bound state
Weak spin-orbit force
What else?

LN-SN mixing, …
n p n
n n
glue-like
role
p
n L n
n n
5
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Nuclear Chart with Strangeness
“glue” like role of L hyperon
Expand hypernuclear
chart by using new
spectroscopic tools
6
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Production Reactions

Emulsion experiment



K- beams stopped in target
Produce “hyperfragment”
Information of BE of g.s.



precise energy determination
but low statistics
Missing-mass spectroscopy



“identified” hypernuclei
K- or - beams
Obtain level structure


high statistics
Mainly Non Charge-eXchange (NCX)

available targets restricted
7
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Production Reactions

Missing-mass spectroscopy 2


Charge exchange reactions
Single CX reactions (SCX)

(e,e’K+)
 thin target available

(K-,0), (-,KS)
 new spectrometer

Double CX reactions (DCX)


(-,K+), (K-,+)
access neutron-rich hypernuclei
 L. Majling NP A585 (1995) 211c


possible with existing setup
very low cross section !
 roughly 1/1000 of NCX
J-PARC E10
8
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Production Exotic n-rich L-hypernuclei

Example of “Hydrogen”
Super Heavy Hydrogen
p
n
1H
Stable
2H Stable
3H Stable
4H
No evidence
5H Resonance
6H No evidence
glue like role of L
L
2
LH Not bound
3 H Stable
L
5
LH
4
7
LH
LH Stable
We can produce at J-PARC
No evidence
6 H Stable ?
L
Stable ?
Hyper Heavy Hydrogen
9
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Super Heavy Hydrogen

Resonance state in 5H system

at Dubna

p(6He,ppt)nn (tnn=5H)
3H(t,p)5H
2H(6He,3He)5H

Missing mass spectra (Ex of 5H(t+n+n system))


p(6He,pp)X
PRL 87 (2001) 092501
PL B566 (2003) 70
NP A719 (2003) 229c
10
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Super Heavy Hydrogen (2)

at GSI


p(6He,2He)5H
NP A723 (2003) 13
at LAMPF
 9Be(-,pt)5H
EPJ A24 (2005) 231
 9Be(-,dd)5H
 6LH

structure  5H structure
Some feedback to structure of normal nuclei
11
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
LN-SN Mixing in L Hypernuclei

ordinary
nuclei
B.F. Gibson et al. PR C6 (1998) 433c
hypernuclei
XN
25MeV
DN
SN
LL
A(I=0)
A(I=0)
L
S
Energetically
Suppressed
77MeV
290MeV
if core isospin=0
A*(I=1)
S
LN
if core isospin0
NN
S=0
A(I0)
S= -1
S= -2
L
A(I0)
OK!
S
important in neutron-rich L-hypernuclei (large isospin)
12
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Coherent LN-SN Coupling

Over/under-bound problem

Hard to understand BE of light hypernuclei


adjust A=4 hypernuclei  5LHe over-bound
adjust 5LHe  A=4 hypernuclei under-bound
Y. Akaishi PTPS 186 (2010) 378
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第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Coherent LN-SN Coupling (2)

Coherent LN-SN coupling

Additional attraction for



4
LH
and
4
LHe
(I=1/2)
Y. Akaishi et al. PRL 84 (2000) 3539
a kind of LNN 3-body force
Strongly state dependent?

important to understand structure of L hypernuclei
14
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Mixing in Neutron-rich Hypernuclei

LN-SN mixing effect important
Coherent LN-SN mixing
originally introduced to
explain A=3-5 hypernuclei
Normal LN interaction
BL ~ 4.4 MeV
Coherent LN-SN mixing effect
BL ~ 4.4 + 1.4 MeV
Precise measurement of B.E.
 Estimation of mixing effect
Y. Akaishi et al. Frascati Phys. Ser. XVI (1999) 59
15
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Mixing and EoS in Neutron Stars

Hyperon content in core of neutron stars
Degree of LN-S0N mixing and EoS
L-matter Interaction (MeV)

S. Shinmura et al. J.Phys G28 (2002) L1
no mixing
Hard EoS
p-fraction
p-fraction
with mixing
Soft EoS
large
mixing
16
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Mixing and EoS in Neutron Stars (2)

Strangeness degree of freedom inevitable


What kinds of strangeness appear ?
Controlled by mass, charge and interaction.
large n/p asymmetry (isospin»1)
 strong LN-SN mixing expected
" L"   L   S
study on neutron-rich hypernuclei
may provide information
S. Balberg and A. Gal NP A625 (1997) 435
17
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Bound or Unbound ?
QF production and n-decay thresholds
Systematics of BEL of known light hypernuclei
L QF threshold
n bound threshold
from systematics

-4.6MeV

mass number of core nuclei
18
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Bound or Unbound ? (2)

Expected

from systematics
-8.3MeV

9 He
L
spectrum
“core” nucleus is 8He (well known halo nuclei)
What kind of configuration is dominant in g.s.?
L QF threshold
8
He  L
5
6
L He  4n, L He  3n
7
L He  2n
n bound threshold 8
L He  n
~3MeV
9
L He( g.s.) ?
19
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Bound or Unbound ? (3)

Deviation from systematics

Contribution of LN residual interaction


Spin-dependent int., LN-SN coupling, …
Effect is small: Need precise measurements
9
LBe
10
9
4
LHe
4 H
L
6
LLi
（E521）
LHe
LH
20
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Studies of Neutron-rich Hypernuclei
KEK-PS (SKY)




9
12
K. Kubota et al. NP A602 (1996) 327
(stopped K-,+) reaction
Production upper limit
LHe:
< 2.4x10-4 /(stopped K-)
12
LBe:
< 6.1x10-5 /(stopped K-)
16
LC:
< 6.2x10-5 /(stopped K-)
LC
g.s.: 9.8±1.2 x10-4 /(stopped K-)
H. Tamura et al. PTPS 117 (1994) 1
21
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Studies of Neutron-rich Hypernuclei (2)
DAFNE (FINUDA)


M. Agnello et al. PL B640 (2006) 145
(stopped K-,+) reaction


production
(K- abs.)-+ vertex cut
reject in-flight S+ decay
+
-
KSignal

+
decay
S+
-
KBackground
Production upper limit
6
LLi:
< 2.5x10-5 /(stopped K-)
7
LLi:
< 4.5x10-5 /(stopped K-)
Acceptance Cut?

22
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Studies of neutron-rich Hypernuclei (3)

DAFNE (FINUDA)


M. Agnello et al. PRL 108 (2012) 042501
6Li(stopped K-,+) reaction
- 6
 6
K

Li


L H
 measure also weak decay


cut on T(+)+T(-)
3 events of candidates
6
LH
  -  6He
2.9±2.0x10-6 /(stopped K-)
Dalitz
Akaishi
23
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
DCX (-,K+) Reaction

KEK-PS (E521)



S. Pranab et al. PRL 94 (2005) 052501
10
B  - , K  10
L Li reaction
Clean reaction
g.s.


K6 beam line @KEK-PS
SKS spectrometer
good energy resolution
DBL = 2.5MeV (FWHM)
47 events in bound region
ds/dW~10nb/sr
(1/1000 of NCX)
BL=0
24
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
DCX (-,K+) Reaction (2)

KEK-E521 data


Beam momenta: 1.05GeV/c and 1.2GeV/c
ds/dW(1.05GeV/c) < ds/dW(1.2GeV/c)
10

B  -, K 
pbeam = 1.05 GeV/c
 10L Li
pbeam = 1.2 GeV/c
25
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Reaction Mechanism

Optimum  beam momentum ~ 1.2GeV/c

E521 experiment tells
pion beam momentum
10B(-,K+)10
LLi

cross section
1.05 GeV/c
1.2 GeV/c
5.8 nb/sr
11.3 nb/sr
Puzzle of reaction mechanism of DCX

Naïve two-step reaction
 -  p  K 0  L, K 0  p  K   n
 -  p   0  n,  0  p  K   L
pion beam momentum
Theory
Lanskoy
Harada et al.
s 1.05 GeV/c 
 s 1.2 GeV/c 
1.05 GeV/c
1.2 GeV/c
38 nb/sr
~16 nb/sr
22 nb/sr
~12 nb/sr
26
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Reaction Mechanism (2)

Tendency of elementary process
 -  p  K 0  L, K 0  p  K   n
 -  p   0  n,  0  p  K   L
27
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Reaction Mechanism (3)

Possibility of other mechanisms

One-step reaction with LN-SN mixing
s 1.05 GeV/c 
 s 1.2 GeV/c 
 -  p  K   S- , (S- p)  (Ln)
LN-SN mixing
pion beam momentum
Theory

Harada et al.
1.05 GeV/c
1.2 GeV/c
2.4 nb/sr
5.4 nb/sr
Elementary cross section
S channel opens
at 1.045GeV/c
28
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
One Step DCX Mechanism


LN-SN coupled channel calculation for the DCX
reaction by Harada et al.
Spectrum is sensitive to mixing interaction VLS
and S-N interaction WS
VLS


WS
Bound region → VLS
Continuum region → WS
29
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Measurement over Wide Mass Range

One step mechanism and mass spectra

If one step mechanism is dominant:
(-,K+)
S region
L region
interference?
Missing Mass
LN-SN Mixing


L(QF)/S-(QF) ratio, shape of L(QF), …
Measurement and understanding of full
spectrum are quite important
30
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Which is better (-,K+) or (K-,+) ?

Cross-section-wise, these are competitive.
DCX reaction
elementary cross section
beam intensity
p(-,K+)Sp(K-,+)S-
70 mb/sr @ 1.2GeV/c
600 mb/sr @ 0.8GeV/c
400 mb/sr @ 1.1GeV/c
~107 /spill(1)
3×105 /spill?(2)
1.5×106 /spill?(3)
(1) if beam duty factor is good
(3) @K1.1, 270kW beam power

(K-,+) data exist


3
(2) @K1.1, 270kW beam power (30GeV,9mA)

Dibaryon search
+ from KS decay

He K - , K0 X , K S      
Tough measurement

Need KS rejection
Czech. J. Phys. 42 (1992) 1089
31
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
J-PARC E10 Proposal

Subject

Production of neutron-rich hypernuclei


higher statistics than previous experiments
Hypernuclei close to neutron drip-line
 6LH: core is 5H resonance, beyond neutron drip-line
 9LHe: core is 8He, typical neutron halo nucleus

Effect of LN-SN mixing in n-rich hypernuclei


Reaction mechanism



precise measurement of binding energies
two step or one step?
optimum beam momentum?
Method

Missing-mass spectroscopy by (-,K+) reaction

method has been established at KEK-PS E521
32
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Experimental Setup

K1.8 beam line



1.2 GeV/c - beams
Good momentum resolution: Dp/p~10-4
5kW beam is enough to obtain 107 /spill
SKS
D3
ESS1
30GeV
D1,D2
p
ESS2
D4
D4
K1.8 beam line
33
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Experimental Setup (2)

SKS spectrometer


Good momentum resolution: Dp/p~10-3
Large acceptance: W~100msr
January 2010
before earthquake
by K. Tanaka
34
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Experimental Setup (3)

SKS spectrometer

Moved from KEK-PS K6 to J-PARC K1.8

momentum acceptance enlarged: good for E10
SKS @KEK-PS K6
SKS @J-PARC K1.8
SDC3, 4
from BNL D-line
TOF Old+New
Large AC New
LC Old+New
35
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Experimental Setup (4)

SKS spectrometer

Simultaneous L and S measurement
p  - , K  S monitoring of stability also possible
Hypernuclei production


S- production
36
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Yield estimation for 6LH production

Cross section ~10nb/sr (~1/1000 of NCX)

Major difficulty in this experiment
Parameters
Values
- beam momentum
- beam intensity
PS acceleration cycle
6Li target thickness
Reaction cross section
Spectrometer solid angle
Spectrometer efficiency
Analysis efficiency

1.2 GeV/c
107 /spill
6 s/spill
3.5 g/cm2
10 nb/sr
0.1 sr
0.5
0.5
High intensity beams
Large acceptance
About 300 events in 3 weeks of beamtime


6 times larger  KEK-E521 (47 events)
Discussion on level structure possible with new data
37
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Prospects on B.E. measurement

Measurement of B.E. of
simulated spectrum
6 H
L
Assumptions
overall energy resolution
 2.5 MeV(FWHM)
6
6
LH
6
LH/QF
LH
yield
 300 events
ratio (Ex<23MeV)
estimated from
 1 / 10
4
L bound
LHe
and
10
LLi
Well separated from QF
Statistical error of B.E. < 0.1MeV
Minimize systematic errors
38
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Prospects on B.E. measurement (2)

Energy resolution affects S/N

good energy resolution is essential

Study of energy resolution in progress
 1H(-,K+)S
runs in February 2012 (E19-2)
12C(+,K+)12 C run in June 2012 (E27)
L
39
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Calibration of Absolute Missing-Mass
No established calibration peak in (-,K+)
 Calibration in 3 or 4 steps


Calibration with




LC
(beam: +, SKS: K+)
calibration in mass range of hypernuclei
Is 12LC good for calibration? (claim by Fukuda)
Calibration with S+ (beam: +, SKS: K+)
Calibration with S- (beam: -, SKS: K+)



12
correct mass and/or estimate systematic error due to
beam polarization change
80MeV/c2 away from mass range of hypernuclei
Monitoring with S- (beam: -, SKS: K+)

test of stability of missing-mass in production runs
40
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Run Plan: E10 1st Step

2012 June (E27 production run)

for preparation of E10




Consideration before production run




trigger rate study (@1.2GeV/c, DCX)
energy resolution study (12LC, S-)
tracking detector study (fiber tracker, etc.)
Energy resolution good enough?
How high beam intensity we can handle?
Optimum target thickness?
2012 Autumn (E10 production run)

Beam intensity at least 3x106 -/spill


5x106 -/spill might be possible
Production of
6
LH
(at least 100 events)
41
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Near Future Plan: E10 2nd Step

Subjects

More statistics for




6
LH
beams with better duty factor
new tracking detectors (fiber, GEM, SSD, …)
Production of
9
LHe
At where and how?

We need beam momentum around 1.2 GeV/c



K1.8 beam line is only candidate at present
If extended K1.1 beam line accepts beam momentum
close to 1.2 GeV/c, it is also a candidate
We need spectrometer with good momentum
resolution


S-2S at K1.8? Resolution better than SKS?
SKS at extended K1.1?
42
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Future Plan

Dilemma of experiments with pion beams

Primary beam intensity does not limit - beam
intensity even at 5kW beam power



We can’t handle very high intensity - beams
Beam power increases year by year
Improvement of slow-extraction technique
SX power upgrade plan (mod-term)
43
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Future Plan (2)

Need new spectrometer to use full beams



HIHR and Hi-PiBF proposed by H.Noumi
Quite suitable for DCX reactions
Beam line and spectrometer with dispersion
matching technique



Established technique at lower energy
EPICS@LAMPF, Grand-RAIDEN@RCNP
Avoid to measure beam to achieve 109 -/spill
or higher beam intensity


Measure only scattered K+
Dispersion matching technique improves also
momentum resolution: 1.5 MeV → a few 100 keV
44
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
HIHR Beam Line and Spectrometer

Handle high intensity and high resolution

Beam line


Vertical dispersion on target
Spectrometer





Tracking only at exit
Horizontal position
 mom. of scattered particle
Vertical position
 beam momentum
H. Noumi , J-PARC LOI-08
45
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
HIHR Beam Line in Hadron Hall
46
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Hi-PiBF in Extended Hadron Hall

High Intensity Pion Beam Facility (Hi-PiBF)

H.Noumi, HUA WS, 23 October 2011
Challenging !
47
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Hi-PiBF in Extended Hadron Hall (2)

K.Tanaka, HUA WS, 23 October 2011
48
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Summary

We wish to expand hypernuclear chart






“glue-like role” of L hyperon
possibility of production of n-rich hypernuclei
LN-SN coupling effect is more important
hypernuclei close to neutron drip-line
close relation with normal neutron-rich nuclei
DCX reaction is promising



new tool of missing-mass spectroscopy
the (-,K+) reaction has been established
also reaction mechanism may provide a hit of
LN-SN coupling
49
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Summary (2)

J-PARC E10 experiment






new neutron-rich hypernuclei: 6LH, 9LHe
6 times higher statistics than KEK-E521
precise measurement of binding energy of
neutron-rich hypernuclei
measurement of wide mass range at a time
preparation in progress at J-PARC K1.8 beam
line → production run in 2012 Autumn
Future


higher statistics with better beam duty factor
HIHR or Hi-PiBF is ideal beam line for
measurement of the DCX reaction
50
第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012
Fin !
Thank you !
51

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