E471: K-nucleus search
E549: Upgrade of E471 (K-nucleus search)
Advanced Meson Science Lab, RIKEN
M. Iwasaki
RIKEN, Tokyo U., TiTech, SNU, CMU, KEK

E471 →

observed“K-nucl. Bound state”

E549 →High resolution/statistics w/ detector upgdade

E549 cond. approved : assigned 2005 spring?
1. Motivation
2. Present Status
3. Goal for E549
１

1. Motivation

Akaishi/Yamazaki prediction
Strong attraction on I = 0 channel

E228 motivatedDeeply bound state ofK- meson and nucleus

2

K-p atom

Λ(1405)

I(JP) = 0(1/2-) Γ ~ 50 MeV---- 3 quark?

~ 330 MeV

~ Σ π thresholdpredictedΣ

I(JP) = 1(1/2+)

ΛI(JP) = 0(1/2+)

3

AMD calculation by Dote et. al.

B ~ 10 MeV

B ~ 120 MeV

B ~ 220 MeV

center ~ ρ0center ~ 10 ρ0center ~ 20 ρ0

4

Low temperature
High density52. E471 experiment6

KEK-PS Setup(2002-2003)

7

VDCtop tracking region

Charged Veto

Hyperon motion?

y^vCA . vn

Charged Veto+πmraLCNx^nΣDvnΣ

vCA+-^vnn ΣNCN

Residual

Charged VetoVDCbott. tracking region

mr-aR

Charged Veto

12

Fast π riggered neutron mass spectrum
backward mass spectrum

Need moredata!

Proton PID on neutron counter system8

4He(stopped K-, p) spectrum

Detection
threshold（due to Feplate）

9

PID on TC

10

B ~ - 200 MeV
Width < 20MeV
same as resolution
Stopped K- origin
No peak in proton-tagged→ ΣNN decay dominant
Exists in all counters
Completely independent
analysis gives the sameresult

Peak is real !!
11

4He(K-, n)

VDCtop tracking region

Charged Veto

Charged Veto4He(K-, p)y+πmraLCNx^nΣDvnΣ

vCA+-^vnn ΣNCN

Residual

Charged Veto

VDCbott. tracking region

rm-aRCharged Veto

13

K-p atom

Λ(1405)
Σ(1385)

I(JP) = 0(1/2-) Γ ~ 50 MeV---- 3 quark?

I(JP) = 1(3/2+) Γ ~ 40 MeV~ 330 MeV

~ Σ π thresholdpredicted
Λ π thresholdobserved inproton spectrum
Σ

I(JP) = 1(1/2+)

ΛI(JP) = 0(1/2+)

14

4He(K-, p) 4He(K-, n)Original Expectation

EK-pnn

K-ppn

K-ppp

110MeV
K-ppn T=0

T=1
Σπ thresholdEΣπ threshold

190MeV
K-ppn T=0??

Λπ threshold

K-pnn
T=1

K-ppn

T=0 ?

K-ppp
Result…
15

3. Goal of E549
① 4He(K-, p) peak/width determination
Energy error ~ 5MeV ? → ~ 1 MeV
Width upper limit → OK if < 10 MeV
Proton statistics
Energy resolution

100 (inclusive)
2-3 times improve

K- + 4He→ (K- + pnn)[T=1] + p| 1/2 -1/2 > |1 -1>+ |1/2 1/2>
K- + 4He→ (K- + ppn)[T=1] + n| 1/2 -1/2 > |1 0>+ |1/2 -1/2>

Formation rate 2:1② High statistics 4He(stoppedK-, n) spectrum
Confirm peak! (As present proton statistics）
T=0 contribution study
Neutron statistics
Energy resolution

10 times more
1.5 times16

4He(K-, n)Statistics 10Resolution 1.54He(K-, p)Statistics 100
Resolution 317

Lower background③ Momentum slit re-install

Direct evidence of high density state?
④ Search for excited states in 4He(K-, p)

ΔE = h ω ≈ 45MeVhω

cf. Search for (K- ppp)T=1 by3He(K-, π -) or 3He(π +, K+)€Spin (parity) and decay
I(JP) = 1(3/2+)⑤ Decay asymmetry… Nemura / Akaishi--- LS importance18

Tracking Chamber Installation(1) 4He(stopped K-, p) inclusive spectrum

w/o trigger counters
K- stop position --- must
→ Statistics 20（Width/Position error ↓↓）→ Formation Branch(2) Study of the decay
ΣNN?
SpinP =3/2+(3) 4He(K-,n) spectrum− T=1 component→

T=0 component(4) TOF prompt calibration
19

Upgrade Plan

Present setup

Improve resolution

N-counter

150ps→50ps

K−

Add N-array at least
till 7 layers

K−pnproton
4He target

Iron plate
Charged particle VETO

Both n/p
σ~300ps

Smallertarget

Proton tracking
chamber!
Proton TOF
start counter

Proton TOF stop counter
Used as charged VETO
for neutron meas.

Proton σ=100~150ps
Neutron σ=200ps
20

Prompt Calibration

Improve resolution
150ps(?) →50ps

7 layerminimum ！

K−πμMetastable state for calibration
From K- injection,
charged π/μ emission
occurs >3ns laterγ
235MeV/c μRange 60.1cm
Formation ~1.6%
1/β = 1.0953
205MeV/c π- Δ(1/β)<0.02
Range 33.4cm
Formation ~ 0.5%
1/β = 1.2109
30days >106 identified→ In-beam TOF calibration

Towards J-PARC
Really Deep-K?
check with other nuclei - DAFNE/FINUDA -Nagae?
K2 by Kishimoto?

LS?
K- 3He / K- 4He atom - DAFNE/DEAR

kaonic atom = highly excited deep-K?

Preparation of CDC / Spectrometer@ J-PARC
If Deep-K = yes … wide research area open!
spin / parity / isospin / LS / A dep. (baryon #) …

Double-K nucleus!
+KK-KKNN
N-KKK+

0KK-KKK N nN N
N NKΛ*KK

-KK

-KK
K p p
N N
N N

K
Ξ--KK
Kp
NN