Prospect of L-spin-flip B(M1) measurementat K1.8 beam line
Mifuyu Ukai
Dept. of Phys. Tohoku Univ.

Contents
Physics motivation of L-spin-flip B(M1) measurement
Feasibility of B(M1) measurement of 19L F(3/2+→1/2+)
Summary and request

Physics Motivation
Medium effect of Baryon
Change of Baryon properties
in the nuclear medium from the free space
magnetic moment of L in nuleus
L-spin-flip B(M1) value++

Jcp =1

lifetime t

Jup =3/2

B(M1)=3/8p (2Jlow+1)/(2Jc+1)(gc-gL)2
B(M1); reduced transition probability of M1

L-spin-flip M1 transition

6Li37
L Li

Jlow =1/2 +G =BR/ t =16p/9 E g B(M1)

Example of spin-doublet structure; L in 0s (7L Li)

L-spin-flip B(M1) value

t and Eg of the transitiontransition energy(Eg), lifetime(t) from peak shape analysis
Only g-ray spectroscopy of Ge detector can measure
One of the main purpose of J-PARC E13

Doppler-shift attenuation method
AZ(K,- p-), AZ(p +, K+)

recoil bb' at deexcitation
ALZGeGeGestopping time ～2 ps, initial b ~ 3%t >> stopping time

E meausred = E 0 /g(1-b' cosq)

sum upt = 1.5 pst ~ 0 ps-40-20

lifetime (t) can be obtained by peak shape fitting E

200meausred40- E 0 (keV)

Privious trials of B(M1) measurement
BNL-E930('01)
10KEK-E518

B(K - ,p-)2-1B

Motivated to measure B(M1)
KEK-E566 12C(p+, K+)
2+B(p+ ,K+)
+
3/2?
1/2 +

262 7/2 ++-10L

11?
11LB

7/2
5/2 +11L

BgL = -1.226 in free space
BNL-E930('01)

gL= -1.1 +0.4-0.6
preliminary

10692 3/2++7
LLi1/2

KEK-E566

B(K -,p - )3+BR(0.2±0.1)
10LB

12L

12L

Ctransition was identified
but spacing energy is too small(target density too high)many g-rays observed
can not identify the transitions

M1 not observed

5/2 +B(M1) measured, unexpectedly-not accurate but finite value
1
gL = -1.03 ± 0.41
preliminary
Derived from2competetition with1
M1 and weak decay(missing yield)

Cweak-1

Gg.s. = (228 ps)
べ・・別にこんなの測りたかった実験じゃないんだからね！

7
L

Lifetime of the 3/2+ state in Li
partly doppler-broadendt= 0.58 -+0.38[ps ](stat. only)
by DSAM
0.20
2B(M1)= 0.30 -+0.12[m]N
0.16+0.4
gL= -1.1 -0.6
[m N]
(g L=-1.226 free space )Unfortunately, using hot-pressed powder target
density NOT uniform for traveling HN=> syst. error

B(M1) and lifetime of light hypernuclei
7LgB(M1)

1/G (ps)

0.692

0.82200.334

0.51+0.262

0.6002

0.341

9.26+

0.3 ~ 0.4(0.566)(0.256)

8.23~3.47

transition

Eg (MeV)+B (7/2 → 5/2+)

Li (3/2 →1/2+)

11L

19LF (3/2 → 1/2+)

Extream rough estimation,target material density of p-shell region ~ 1 ~ 2 g/cm
stopping time by (K,p), (p,K) reaction ~ 2 ps

Too fast / Too slow

Gamma-ray spectroscopy of light hypernuclei; E13SMF

Inor

w

all

TOF

SDC3, 4

7L4L

10L

11L

19L

He, Li, B, B, F
First stage of E13SK4LSMs

2.5Tinu/cVe /c)
G.4 GeV
1~ .7(1SP0SDC1,219L

He and FMotivation
LN spin-spin interaction study
for sd-shell hypernuclei
Teflon R ;(C2F4 )n as F target in proposal(Very easy to handle)

BC3,4
1.5 GeV/c(1.8 GeV/c)Hyperball-J

How reliable for B(M1) measurement
using low intensity target?

Level scheme of0.572(6)0.59(4)234 ns27.6 fs
2.6 fs

1.121
1.081
1.042

67.7 ps

0.937

19LF

DL=1
DL=05+0-0+3++1018g [mN]

(0d5/2)p x (0d5/2 )nt

E x(MeV)

FDS=01/2+1/2+7/2
5/2++

158.40 m

DL=2}

19LF

3/2 0.3 ~ 0.4
01/2+

LN spin-spinfor sd-shellE x(MeV)main motivation of F

g-facotor of the g.s. of F NOT measured
g-factor of N=Z odd-odd nucleus (jp = jn)
well reproduced by Schmit value of jj-coupling scheme (except for Li)

g = [g (0d5/2)p+ g(0d5/2)n]/2= 0.576= 0.566(Shmit value)(extraporation from 17O and 17F)

Stopping time and expected lifetimeFluoromethane

CH3F

boiling point
0.557 g/cm3-78.2

Hydrofuloride

HF

1.002 g/cm3(C2 F4)n2.17 g/cm 3F3HCHF

Tefloncalculated lifetime (ps)pK = 1.8 GeV/cstopping time (ps)recoil momentum (MeV)

Teflon R

19.5

1210schmit value g = 0.576

extraction from 17O and 17F g =0.566

8schmit x 0.9 g=0.518

642reaction angle qKp (deg)initial momentum (MeV)

500
400
300
E g (3/2+→ 1/2+ ) [keV]

Larger momentum transfer, lower target density are feasibleDemonstrate;19F(K- ,p- ) @ pK = 1.8 GeV/c, CH3 F target

Yield estimation@p = 1.8 GeV/c-DL=1
DL=0∫ds/dW ・dW ~ 7.5 mb

DL=2(cross section ; from calculation for 20Ne )1/2+1/2+7/2
5/2+

SksMinus

Target; CH3F 30 cm: 17.3 g/cm2
BR (1/2 -→ 3/2+ )/(1/2-→ 1/2,+ 3/2+)~ 0.3 @ (3/2, 1/2) = 400 keVeg @ 400 keV ~ 10 %+

3/2
19LF

1/2+0.3 ~ 0.4
0E x(MeV)

Kaon yield by rough scan
~ 45 k /spill @ 3 kW
(narrow IFV slit 2mm)
ESS1,2 = ± 200 kV

4.5 counts/ hour / (200k/spill)(spill cycle = 6 s )1000 counts /10 days for 200 k/spill(direct production of 3/2+ are not included)

Sensitivity of lifetime

E g1 Eg2
E1

1/2

-

error of lifetime fitting

t = 8 ps
1500 counts

fit onlylarge reaction angle(q> 10°) events-10%-20%(Background; not take account )+3/2

t = 3.5 ps1000 counts

20%
10%

E1+t = 5 ps
1200 counts+

lower E(3/2 )-E(1/2 ) energy:
Longer lifetime , Branching ratio+

1/2, Efficiency

g-ray yield
33

BRg1/ BRg2 ∝ E g1 / Eg2

lifetime~ 10 % (g ~ 7 %) accuracy acheivable
10 days beam time (if 200 k/spill)Other B(M1) product using CH3F target~ low density Carbon target

stopping time (ps)}q > 15°expected t ~ 9.3 ps+e
7/2
anthemdi
qui
L
3FHC

11L B

DL = 2 12C(K- , p- )

+

2+
5/2
DL = 1 Y(1- →2-)
1~100 counts/ 10 days
@200 k/spill, 6 s cycle

aloso possible?

recoil momentum (MeV)

2Kaon yield by rough scan
~ 45 k /spill @ 3 kW
(narrow IFV slit 2mm)
ESS1,2 = ± 200 kV-(E566 ~ g = -1.03± 0.41 [mN]for 50 counts/month)

1weak

-1

Gg.s. = (228 ps)

Summary and Request
g-ray spectroscopy of 4LHe and 19
L F will be perfomed at 1st stage of E13
Feasibility of L-spin-flip B(M1) in 19
L F measurement is simulated
Lifetime accuracy~ 10 % will be achiebable using 10 days (200 k/spill)

We need theoretical support!
+g-factor information of F(1 )Spacing energy19LF(3/2 , 1/2+ )+12

realistic cross sections of 19L F and L C states