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
Studies of L Hypernuclei Hypernuclei (L hypernuclei)
Bound state of hyperon (L) and nuclei How to study?
Emulsion and bubble chambers Discovery by Danysz and Pniewski in CR K- beams at CERN LL: KEK-PS, (BNL-AGS), J-PARC, …
Missing-mass spectroscopy CERN-PS BNL-AGS KEK-PS DAFNE JLAB, MAMI-C, … J-PARC, …
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
2
),(),stopped( ---- KK),stoped(),(),( 0 --- KKK
),(),stopped( -- KK ),stopped( -- K),( Kee
feasibility
CR
Hypernucleusweakdecay
3
Missing-Mass Spectroscopy at CERN
Heidelberg-Saclay-Strasbourg Collaboration
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
SPES II
4
Studies of L Hypernuclei (2) How to study?
g-ray spectroscopy CERN-PS (4
LH, 4LHe)
BNL-AGS, KEK-PS J-PARC, …
Invariant-mass spectroscopy in HI collisions BNL-AGS BNL-RHIC (discovery of anti-hypernuclei) GSI-SIS, FAIR, …
Weak decay of L hypernuclei Achievement in experiments?
Production of identified hypernuclei Better and better energy resolution
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
with missing-mass cutcan achieve good S/N
proton-rich L hypernuclei, …
5
Properties of L Hypernuclei Single particle picture is OK
Beautiful L shell structure Deeply bound L state Highly excited L bound state
“Glue-like role” of L hyperon L-N interaction is attractive Possible to stabilize nuclei Doorway to strange matter
Spin dependent interaction Weak spin-orbit force
What else? LN-SN mixing, …
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
glue-likerole
pn
n
n
n
pLn
n nn
Nuclear Chart with Strangeness
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
6
“glue” like role of L hyperon
Large area un-explored !
Expand hypernuclear chart by using new spectroscopic tools
7
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
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
NCX
8
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
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
SCXDCX
J-PARC E10
Production Exotic n-rich L-hypernuclei Example of “Hydrogen”
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
9
5LH No evidence
6LH Stable ?
7LH Stable ?
2LH Not bound
3LH Stable
4LH Stable
L
1H Stable2H Stable3H Stable
4H No evidence5H Resonance6H No evidence
n
pSuper Heavy Hydrogen
Hyper Heavy Hydrogen
glue like role of L
We can produce at J-PARC
10
Super Heavy Hydrogen Resonance state in 5H system
at Dubna p(6He,ppt)nn (tnn=5H) PRL 87 (2001) 092501 3H(t,p)5H PL B566 (2003) 70 2H(6He,3He)5H NP A719 (2003) 229c
Missing mass spectra (Ex of 5H(t+n+n system))
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
p(6He,pp)X
11
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
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
B.F. Gibson et al. PR C6 (1998) 433c
12
if core isospin=0
L SA(I=0) A(I=0)
if core isospin0
L SA(I0) A(I0)
OK!
SA*(I=1)Energetically
Suppressed
important in neutron-rich L-hypernuclei (large isospin)
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
NN
DN
LN
SN
290MeV77MeV
S=0 S= -1
mass diff. ~1/4 larger mixing
ordinarynuclei
hypernuclei
S= -2
LL
XN25MeV
13
Coherent LN-SN Coupling Over/under-bound problem
Hard to understand BE of light hypernuclei adjust A=4 hypernuclei 5
LHe over-bound adjust 5
LHe A=4 hypernuclei under-bound
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
Y. Akaishi PTPS 186 (2010) 378
14
Coherent LN-SN Coupling (2) Coherent LN-SN coupling
Additional attraction for 4LH 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
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
15
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
Coherent LN-SN mixing originally introduced to explain A=3-5 hypernuclei
Y. Akaishi et al. Frascati Phys. Ser. XVI (1999) 59
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
16
L-m
atte
r Int
erac
tion
(MeV
)
large mixing
Hard EoS
Soft EoS
no mixing
with mixing
p-fraction
p-fraction
S. Shinmura et al. J.Phys G28 (2002) L1
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.
17
SLL ""
large n/p asymmetry (isospin»1) strong LN-SN mixing expected study on neutron-rich hypernuclei
may provide information
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
S. Balberg and A. Gal NP A625 (1997) 435
18
Bound or Unbound ? QF production and n-decay thresholds
Systematics of BEL of known light hypernuclei
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
-4.6
MeV
from
syst
emat
icsL QF threshold
n bound threshold
mass number of core nuclei
19
Bound or Unbound ? (2) Expected 9
LHe spectrum “core” nucleus is 8He (well known halo nuclei) What kind of configuration is dominant in g.s.?
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012-8
.3M
eVfro
m sy
stem
atics L QF threshold
n bound threshold
LHe8
nHenHe 3,4 65 LL
nHe 27 L
nHeL8
?.).(9 sgHeL
~3MeV
20
Bound or Unbound ? (3) Deviation from systematics
Contribution of LN residual interaction Spin-dependent int., LN-SN coupling, …
Effect is small: Need precise measurements
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
10LLi
( E521 )
4LHe
4LH
9LBe
9LHe
6LH
21
Studies of Neutron-rich Hypernuclei KEK-PS (SKY)
K. Kubota et al. NP A602 (1996) 327 (stopped K-,+) reaction Production upper limit
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
9LHe: < 2.4x10-4 /(stopped K-)
12LBe: < 6.1x10-5 /(stopped K-)
16LC: < 6.2x10-5 /(stopped K-)
12LC g.s.: 9.8±1.2 x10-4 /(stopped K-)
H. Tamura et al. PTPS 117 (1994) 1
22
Studies of Neutron-rich Hypernuclei (2) DAFNE (FINUDA)
M. Agnello et al. PL B640 (2006) 145 (stopped K-,+) reaction
(K- abs.)-+ vertex cut reject in-flight S+ decay
Production upper limit
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
6LLi: < 2.5x10-5 /(stopped K-)
7LLi: < 4.5x10-5 /(stopped K-)
K-
-+
K-
-+
S+
Signal Background
production decay
Acce
ptan
ce C
ut?
23
Studies of neutron-rich Hypernuclei (3) DAFNE (FINUDA)
M. Agnello et al. PRL 108 (2012) 042501 6Li(stopped K-,+) reaction
measure also weak decay cut on T(+)+T(-)
3 events of candidates
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
HeH
HLiK66
66
-
L
L-
2.9±2.0x10-6 /(stopped K-)
Dalitz
Akaishi
DCX (-,K+) Reaction KEK-PS (E521)
S. Pranab et al. PRL 94 (2005) 052501 reaction Clean reaction
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
24
LiKB 1010 , L-
K6 beam line @KEK-PS SKS spectrometer
good energy resolutionDBL = 2.5MeV (FWHM) BL=0
g.s.
ds/dW~10nb/sr (1/1000 of NCX)
47 events in bound region
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)
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
25
LiKB 1010 , L-
pbeam = 1.2 GeV/cpbeam = 1.05 GeV/c
Reaction Mechanism Optimum beam momentum ~ 1.2GeV/c
E521 experiment tells
Puzzle of reaction mechanism of DCX Naïve two-step reaction
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
26
pion beam momentum 1.05 GeV/c 1.2 GeV/c10B(-,K+)10
LLi cross section 5.8 nb/sr 11.3 nb/sr
GeV/c2.1GeV/c05.1
ss
L
L-
-
Kpnp
nKpKKp00
00
,
,
pion beam momentum 1.05 GeV/c 1.2 GeV/c
Theory LanskoyHarada et al.
38 nb/sr~16 nb/sr
22 nb/sr~12 nb/sr
27
Reaction Mechanism (2) Tendency of elementary process
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
L - Kpnp 00 ,
nKpKKp L - 00 ,
Reaction Mechanism (3) Possibility of other mechanisms
One-step reaction with LN-SN mixing
Elementary cross section
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
28
)()(, npKp LSS --- GeV/c2.1GeV/c05.1
ss
S channel opensat 1.045GeV/c
pion beam momentum 1.05 GeV/c 1.2 GeV/cTheory Harada et al. 2.4 nb/sr 5.4 nb/sr
LN-SN mixing
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
Bound region → VLS
Continuum region → WS
29
VLS
WS
More yield is necessary to make
detailed discussions
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
30
Measurement over Wide Mass Range One step mechanism and mass spectra
If one step mechanism is dominant:
L(QF)/S-(QF) ratio, shape of L(QF), … Measurement and understanding of full
spectrum are quite important
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
L region
S region
Missing Mass
(-,K+)
LN-SN Mixing
interference?
31
Which is better (-,K+) or (K-,+) ? Cross-section-wise, these are competitive.
(K-,+) data exist Dibaryon search + from KS decay
Tough measurement Need KS rejection
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
DCX reaction elementary cross section beam intensityp(-,K+)S-
p(K-,+)S-70 mb/sr @ 1.2GeV/c
600 mb/sr @ 0.8GeV/c400 mb/sr @ 1.1GeV/c
~107 /spill(1)
3×105 /spill?(2)
1.5×106 /spill?(3)
(1) if beam duty factor is good (2) @K1.1, 270kW beam power (30GeV,9mA)(3) @K1.1, 270kW beam power
-- SKXKKHe ,, 03
Czech. J. Phys. 42 (1992) 1089
32
J-PARC E10 Proposal Subject
Production of neutron-rich hypernuclei higher statistics than previous experiments
Hypernuclei close to neutron drip-line 6
LH: core is 5H resonance, beyond neutron drip-line 9
LHe: core is 8He, typical neutron halo nucleus Effect of LN-SN mixing in n-rich hypernuclei
precise measurement of binding energies Reaction mechanism
two step or one step? optimum beam momentum?
Method Missing-mass spectroscopy by (-,K+) reaction
method has been established at KEK-PS E521
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
33
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
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
30GeV p D1,D2
D3 D4
ESS1
ESS2 D4
K1.8 beam line
SKS
34
Experimental Setup (2) SKS spectrometer
Good momentum resolution: Dp/p~10-3
Large acceptance: W~100msr
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
January 2010before earthquake
by K. Tanaka
35
Experimental Setup (3) SKS spectrometer
Moved from KEK-PS K6 to J-PARC K1.8 momentum acceptance enlarged: good for E10
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
SKS @KEK-PS K6 SKS @J-PARC K1.8
SDC3, 4from BNL D-line
TOF Old+New
LC Old+NewLarge AC New
36
Experimental Setup (4) SKS spectrometer
Simultaneous L and S measurement monitoring of stability also possible
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
Hypernuclei production S- production
-- SKp ,
Yield estimation for 6LH
production Cross section ~10nb/sr (~1/1000 of NCX)
Major difficulty in this experiment
About 300 events in 3 weeks of beamtime 6 times larger KEK-E521 (47 events) Discussion on level structure possible with new data
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
37
Parameters Values
- beam momentum- beam intensityPS acceleration cycle6Li target thicknessReaction cross sectionSpectrometer solid angleSpectrometer efficiencyAnalysis efficiency
1.2 GeV/c107 /spill6 s/spill
3.5 g/cm2
10 nb/sr0.1 sr
0.50.5
High intensity beams
Large acceptance
Prospects on B.E. measurement Measurement of B.E. of 6
LH
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
38L bound
6LH
simulated spectrum Assumptionsoverall energy resolution
6LH yield
6LH/QF ratio (Ex<23MeV)
MeV(FWHM)5.2
events300
Well separated from QFStatistical error of B.E. < 0.1MeVMinimize systematic errors
10/1 estimated from 4LHe and 10
LLi
39
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
LC run in June 2012 (E27)
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
40
Calibration of Absolute Missing-Mass No established calibration peak in (-,K+) Calibration in 3 or 4 steps
Calibration with 12LC (beam: +, SKS: K+)
calibration in mass range of hypernuclei Is 12
LC good for calibration? (claim by Fukuda)
Calibration with S+ (beam: +, SKS: K+) Calibration with S- (beam: -, SKS: K+)
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
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
41
Run Plan: E10 1st Step 2012 June (E27 production run)
for preparation of E10 trigger rate study (@1.2GeV/c, DCX) energy resolution study (12
LC, S-) tracking detector study (fiber tracker, etc.)
Consideration before production run 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)
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
42
Near Future Plan: E10 2nd Step Subjects
More statistics for 6LH
beams with better duty factor new tracking detectors (fiber, GEM, SSD, …)
Production of 9LHe
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?
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
43
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
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
SX power upgrade plan (mod-term)
44
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
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
45
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
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
H. Noumi , J-PARC LOI-08
46
HIHR Beam Line in Hadron Hall
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
47
Hi-PiBF in Extended Hadron Hall
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
High Intensity Pion Beam Facility (Hi-PiBF) H.Noumi, HUA WS, 23 October 2011
Challenging !
48
Hi-PiBF in Extended Hadron Hall (2)
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
K.Tanaka, HUA WS, 23 October 2011
49
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
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
50
Summary (2) J-PARC E10 experiment
new neutron-rich hypernuclei: 6LH, 9
LHe 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
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
51
第22回原子核ハドロン物理セミナー @JAEA, 15 March 2012
Fin !Thank you !