K pp bound state search at LEPS2 experimentlambda.phys.tohoku.ac.jp/nstar/content/files/NSMAT2016/... · 2016. 12. 1. · Kaonic nuclei ☆K-N interaction Low energy Kp scattering

K− pp bound state search

at LEPS2 experiment

A. O. Tokiyasu

ELPH, Tohoku University

NSMAT2016 @ Tohoku Universiyt

21th. Nov. 2016

Index

2

1. Physics Motivation

2. LEPS2 experiment

3. Schedule

4. Summary

Kaonic nuclei

☆K-N interactionLow energy Kp scattering

Kaonic hydrogen level shift

(KEK-PS E228)

strongly attractive (I = 0)

☆Kaonic nucleiKaon bound states with a few nucleons

(Akaishi-Yamazaki prediction)

B.E. ~several tenth MeV

Phys. Rev. C 65, 044005 (2002)

Study on K-pp bound state

Information on K–N interactionIf K-N interaction is very strong,

Kaon condensation inside NS

KK

K

KK

K

K

K

Lect. Notes Phys. 578 (2001) 175-202

Previous experiment

Experiment Reaction B.E. G

FINUDA

(Italy, 2005)

stopped K-

on Li, C

115±6±4 MeV 67±14±3 MeV

DISTO

(France, 2010)

p + p K+ + L + p 105±2±5 MeV 118±8±10MeV

J-PARC E15

(Japan, 2015)

3He(K-, n )X

X = L + p

event enhancement below K-pp threshold

J-PARC E27

(Japan, 2015)

d(p+, K+)X 95+18-17+30

-21 MeV 162+87

-45+66

-78 MeV

Measured B.E. and G are inconsistent!

Threoretical prediction

0

50

100

150

200

250

300

-140 -120 -100 -80 -60 -40 -20 0

■ exp● Chiral● non-chiral

J-PARC E27

DISTO

FINUDA

Almost all theoretical models

predict the existence of

the K-pp bound state!

- B.E. and Γ depends on models.

- inconsistent with exp results.

but

-B.E. (MeV)

Γ (

MeV

)

Situation is still controversial…

Other experiments are awaited.

Ref. NPA914(2013)270

Search for K-pp in LEPS

g + d K+ + p- + X

g beam ( Eg = 1.5 – 2.4 GeV) by Backward Compton Scattering methods.

K+ p- were detected at forward angles (cosΘ > 0.95)

Peak Structures were searched for in missing mass spectrum.

K-pp search via g + d K+ + p- + X

1.8 1.9 2 2.1 2.2 2.3 2.4 2.5 2.6 2.70

0.5

1

1.5

2

2.2 2.25 2.3 2.35 2.4

0.5

1

1.5

MMd(K+π-) [GeV/c2]

d3σ

/dco

sΘla

b

K+d

cosΘ

lab

π-/dM

(μb

/ 2

0 [

MeV

/c2])

K-pp

threshold

Search

Region

2.22 2.24 2.26 2.28 2.3 2.32 2.34 2.360

0.5

1

1.5

2

2.5

3

3.5

= 20 MeVΓ

= 60 MeVΓ

= 100 MeVΓ

Upp

er L

imit

of

K- p

p p

rod

uct

ion

(d2σ

/dco

sΘla

b

K+d

cosΘ

lab

π-[μ

b])

MMd(K+π-) [GeV/c2]

(a) (b)

From likelihood ratio method;

G = 20 MeV : 0.17 - 0.55 mb

G = 60 MeV : 0.55 - 1.7 mb

G = 100 MeV : 1.1 - 2.9 mb

n

L

S

L*/S*

Search region 2.22 – 2.36 GeV/c2

Significant peak cannot be observed.

MM(K+p-) Upper limit of cross section (95% C.L.)

~10% of Q.F. processes

Lesson from LEPS experiment

SPring-8/LEPS2 experiment!

☆1st search results by the photo-induced reaction.

☆

LEPS2 project

K-pp search

Θ+ search

Study of Λ(1405) K* photo-production

Missing resonance search

η’-nuclei search

meson photo-production mechanism

Y-N scattering

dark photon search

high intensity g beam large acceptance detector

New field in hadron physics

Large acceptance

spectrometer

5 – 120° (charged)40 – 110° (photon)

multi laser

injection

+

low emittance

e- beam

~107 cps(LEPS x10)

SPring-8/LEPS2

LEPS2 spectrometer system

2.22 m

g

TPC DC

g counter RPC

AC

Magnet (BNL-E949)

B=1 T

11

☆ Acceptance5 – 120° (charged particle)

30 – 110° (γ)

☆ Momentum measurement- sideway (50– 120°)

TPC Δp/p ~ 0.04 (1 GeV/c)

- forward (5 – 50°)DC Δp/p ~ 0.01 (1 GeV/c)

☆ Particle Identification3σ separation up to 2.7 GeV/c

- sideway (5 – 50°)RPC (TOF)

- middle (30 – 60°)AC, RPC

11

SC


2.22 m

g

TPC DC

g counter RPC

AC

Magnet (BNL-E949)

B=1 T

12

12

SC

Scintillator + MPPC

Time Resolution σ ~ 200ps

TDC_ch [ch](1ch = 50 ps)800 900 1000 1100 1200 1300 1400

co

un

t/ch

0

20

40

60

80

100

120

140

160

TDC_Mean-TDC_RF w/ CorrectionTDC_Mean-TDC_RF w/ Correction


2.22 m

g

TPC DC

g counter RPC

AC

Magnet (BNL-E949)

B=1 T

13

13

• R=655 mm, 24 layer• σrφ=150 μm, σz=2 mm

SC


2.22 m

g

TPC DC

g counter RPC

AC

Magnet (BNL-E949)

B=1 T

14

14

SC

1.3m


2.22 m

g

TPC DC

g counter RPC

AC

Magnet (BNL-E949)

B=1 T

15

15

SC

K/π

20 cm

20 cm 16

cm

4 cm

PMT

6.5 cm

6.5 cm

6 cm

4 cm

n=1.03, 1.05

Efficiency > 99% for π+/-


2.22 m

g

TPC DC

g counter RPC

AC

Magnet (BNL-E949)

B=1 T

16

16

SC

200 cm

25 cm

gas tight body

preamp

Long RPC 200 mm

σ < 70 ps


2.22 m

g

TPC DC

g counter RPC

AC

Magnet (BNL-E949)

B=1 T

17

17

SC

Lead + Scintillator :14.3 X0

ΔE/E ~ 20 %

(100 MeV)


2.22 m

g

TPC DC

g counter RPC

AC

Magnet (BNL-E949)

B=1 T

18

18

SC

☆Data Acquisition system

- Software

DAQ-Middleware

- Trigger system

1 charged particle

(min bias trigger)

J-PARC MTM

K-pp bound state search at LEPS2

• Minimum bias trigger (1 charged particle hit)

Search in many reactions

19


• Minimum bias trigger (1 charged particle hit)


– γ + d K-pp + K+ + π-

– γ + d K-pp + Ks

– γ + d K-pp + K*0

– γ + d K-pn + K+

20


• Minimum bias trigger


• Highly polarized γ

Select exchanged particle in t-channel.

21




22

E g K*K

p

unatural parity ex.P= -(-1)J

kaons

Parity filter

(γ、K*0)






• 4π Spectrometer for charged particles and γ

All decay particles will be detected

23


• 4π Spectrometer

production and decay particles will be detected

24

K-pp Λ p

Σ p

Λ p π0

Σ p π0

non-mesonic decay mode

mesonic decay mode






• 4π Spectrometer

production and decay particles will be detected

25

But…

The photo-production cross section is very small

How many yield is expected?

Yield estimation

• in case γ + d Ks0 + K-pp Ks

0 + Λ + p

• Y(K-pp)

= photon number

* target number

* cross section

* BR(YP)

* Acceptance

26


0 + Λ + p

• Y(K-pp)

= photon number

2 * 1014

* target number

8 * 1023

* cross section

20 nb

* BR(YP)

10 %

* Acceptance

30 %27

☆Assumption 1:Λ(1405) door-way

K-pp / Λ(1405) ~ 1%

☆Assumption 2:σ (γ p K+ Λ(1405))

σ (γ p Ks Λ(1405))

10 7cps γ, 200 days (optimistic)

Yield estimation


0 + Λ + p

• Y(K-pp)

= photon number

2 * 1014

* target number

8 * 1023

* cross section

20 nb

* BR(YP)

10 %

* Acceptance

30 %28

~103 ev / year

- differential cross section

(t-dep, Eγ-dep…)

reaction mechanism

- Polarization Observable

Spin, Parity

(under study)

Yield estimation

Schedule• 2016 Oct.

– Trigger Study

• 2016 Nov. Detector install

– SC, TPC, DC, AC, RPC (not full setup)

• 2016 Dec. Commissioning run start

– Performance check of Spectrometer by using the γp pπ+π- reaction

29

DC

e+/e-

veto AC

BeamProfile Monitor

K/π ID AC

SC

TPC

γ beamCH2

p

π-

π+DAQ

supported byKAKENHI No.15H00839新学術公募研究「実験と観測で解き明かす中性子星の核物質」

Summary

☆K-pp bound state is a good probe to extract the information on

the structure inside neutron stars.

☆ LEPS2 : 107 cps γ beam, 4π spectrometer

Search for K-pp bound state via various reactions.

(g + d Ks0 +X, g + d K*0 + X…)

☆ LEPS2 Commissioning run starts from 2016 Dec.

☆ Collaboration is open. Let’s work together!

30

Back UP

31

K-pn, K-pn search

2 2.1 2.2 2.3 2.4 2.5 2.6 2.70

0.2

0.4

0.6

2.2 2.25 2.3 2.35 2.40

0.2

0.4

0.6

0.8

MMd(K+π+) [GeV/c2]

d3σ

/dco

sΘla

b

K+d

cosΘ

lab

π+/d

M

(μ

b /

20

[M

eV/c

2])

K-nn

threshold

Search

Region

preliminary

2 2.1 2.2 2.3 2.4 2.5 2.6 2.70

0.5

1

1.5

2

2.2 2.25 2.3 2.350

0.5

1

1.5

K-pn

threshold

Search

Region

d2σ

/dco

sΘla

b

K+

-/dM

(μ

b /

10

[M

eV/c

2])

MMd(K+) [GeV/c2]

preliminary

- large background from QF process in the inclusive measurement.

- Identification of Final state is indispensable (KNN Y N)

K-pn search

via γ + d K+ + X

K-nn search

via γ + d K+ + π+ + X

32

Documents

K pp bound state search at LEPS2 experimentlambda.phys.tohoku.ac.jp/nstar/content/files/NSMAT2016/... · 2016. 12. 1. · Kaonic nuclei ☆K-N interaction Low energy Kp scattering