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

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, …


2

),(),stopped( ---- KK),stoped(),(),( 0 --- KKK

),(),stopped( -- KK ),stopped( -- K),( Kee

feasibility

CR

Hypernucleusweakdecay

3

Missing-Mass Spectroscopy at CERN

Heidelberg-Saclay-Strasbourg Collaboration


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


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, …


glue-likerole

pn

n

n

n

pLn

n nn

Nuclear Chart with Strangeness


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


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


SCXDCX

J-PARC E10

Production Exotic n-rich L-hypernuclei Example of “Hydrogen”


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))


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


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)


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


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


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


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


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


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


-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


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


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


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


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


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)


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


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


L - Kpnp 00 ,

nKpKKp L - 00 ,

Reaction Mechanism (3) Possibility of other mechanisms

One-step reaction with LN-SN mixing

Elementary cross section


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


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


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


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


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


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


January 2010before earthquake

by K. Tanaka

35


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, 4from BNL D-line

TOF Old+New

LC Old+NewLarge AC New

36


Simultaneous L and S measurement monitoring of stability also possible


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


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


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)


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


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)


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?


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


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


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


H. Noumi , J-PARC LOI-08

46

HIHR Beam Line in Hadron Hall


47

Hi-PiBF in Extended Hadron Hall


High Intensity Pion Beam Facility (Hi-PiBF) H.Noumi, HUA WS, 23 October 2011

Challenging !

48

Hi-PiBF in Extended Hadron Hall (2)


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


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


51


Fin !Thank you !

Documents

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

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