Atsushi - PowerPoint Presentation

Slide1

Atsushi

Tokiyasu

(for LEPS collaboration)

Experimental Nuclear and

Hadronic Physics Laboratry,Department of Physics, Kyoto University

Search for

Kaonic nuclei at SPring8/LEPS

GCOE Symposium

12

th

– 14

th

.Feb.2013 @ Kyoto University Slide2

strangeness in nuclei2013/2/13

GCOE Symposium @ Kyoto University1 / 11

d

s us,

SU(3) octet baryon

SU(3)

nonet meson

L

K

?

Hyper nuclei

Shrinkage

 impurity effect.

nuclear force in SU(3)

Kaonic

nuclei

new form of the nuclei

whether exist or not?

What happens in nuclei?

ud

s

hyperon

kaonSlide3

dependent on

the models of KN interaction the calculation methods.

Formation of Cold (T=0) and Dense (r

> 2r0) nuclei.

2013/2/13GCOE Symposium @ Kyoto University2 / 11K can be bound in the nuclei by strong interaction. K N interaction (I=0) is strongly attractive !X-ray shift of

Kaonic HydrogenK-

p scattering data 2-body: KN : L(1405) ?3-body: KNN : lightest nucleus. K-pp  the strongest bound state in 3-body systemsTheoretical prediction (All theory support the existence)B.E. = 20-100 MeV

G = 40- 110

MeV

If

G

> B.E, it is difficult to observe experimentally.

Ref: Particle Data Group

Kaonic

nucleiSlide4

Experiments2013/2/13

GCOE Symposium @ Kyoto University3 / 11

FINUDA @ DA

F

NE (2005)

DISTO@ SATURNE(2010)

stropped K

-

on (

6

Li,

7

Li,

12

C,

27

Al and

51

V)

p

p



L

p K

+

B.E. =

B.E. =

G

=

G

=

invariant mass (

L

+ p)

Missing mass (

K+)

MeV

MeVMeV

MeV

M.Agnello

,

Nagae

and

Fujoka

et

al.,

PRL

94, 212303 (2005)

T.Yamazaki

et al.,

PRL

104, 132502 (2010)

K

-

pp



L

p

,

S

0

p,

S

+

n (non-

mesonic

decay)  easy to identify experimentally



S

p

p

(

mesonic

decay)Slide5

Summary of the introductionK-

pp is the lightest kaonic nuclei.Existence of K-pp is not established.

Experimental search using different reactions are awaited!Forthcoming experiments3He(

K-, n)X  E15 @ J-PARC D(p+

, K+)X  E27 @ J-PARCg D K+ p- X

 LEPS @ SPring-8

2013/2/13GCOE Symposium @ Kyoto University4 / 11 Prof.Nagae’s talkSlide6

g D  K+

p - X reaction2013/2/13

GCOE Symposium @ Kyoto University5 / 11

K

+

p

-

g

“K” exchanged in t-

chanel

 unique for

g

-induced reaction

( J = 1)

polarization observables are available.

K

-

pp is “soft” object.

 small momentum transfer

 detect K

+

and

p

-

at forward angle

Search for a bump structure

in the missing mass spectrum

M

x

2

=

(

E

g

+ M

D

– E

K

-

E

p

)

2

- (p

g

–

p

K

- p

p

)

2

 independent of decay

chanel

.

K, K*

Y*

p

n

p

K

-

p

Y*

(

E

g

, p

g

)

(E

K

,

p

K

)

(

E

p

, p

p

)

(M

D

,0)

Y* door-way.Slide7

SPring-8 “Super Photon ring-8

GeV”2013/2/13GCOE Symposium @ Kyoto University

6 / 11

Data take:

2002/2003, 2006/2007 7.6 x 1012 photons on LD2 targetSPrin

g-8: 8 GeV electron storage-ringLEPS : hadron

physics using g beamBack-word Compton Scatteringe

e

Detect with

Tagging counter

E

g

=1.5 - 2.4

GeV

experimental

hatch



355nm laser

8

GeV

LEPS

D

E

g

=12

MeVSlide8

LEPS spectrometer2013/2/13

GCOE Symposium @ Kyoto University7 / 11

TOF

Dipole Magnet　

0.7 [Tesla]

Target

Start Counter

DC2

DC3

DC1

SVTX

AC(n=1.03)

SSD

(SVTX)

Drift Chamber

(DC 1~3)

position

Start Counter

(SC)

Time of flight wall

(TOF)

time

Aerogel

Cherencov

counter

(AC)

Start Counter (SC)

trigger

g

(1.5-2.4

GeV

)

p

-

K

+Slide9

particle identification2013/2/13

GCOE Symposium @ Kyoto University8 / 11

K

+

p-Dp/p ~ 6 MeV/c

@ 1 GeV/c

TOF (Time of flight)m2 = p2(1/β2 - 1)

line tracking

+

Runge-Kutta

method.

mass p = 938.3

MeV

mass K

+

= 493.7

MeV

mass

p

-

= 139.6

MeV

c.f.

p

p

+

K

-

0Slide10

Missing Mass Spectrum2013/2/13

GCOE Symposium @ Kyoto University9 / 11

Error Bar : statistical uncertainty (~5%)

Red Box : systematic uncertainty (~20%)Hatched : discrepancy between datasets (~12%)

preliminaryNo bump structure was observed!upper limit of cross section

L

Snsearch region: Mass = 2.22 - 2.36 GeV/c2

B.E. = 150 - 10 MeV

acceptance was corrected with Monte-Carlo simulation

expected signalSlide11

Upper Limits of differential cross section2013/2/13

GCOE Symposium @ Kyoto University10 / 11

preliminary

-

G= 20 MeV 0.05 - 0.25 mb-G = 60 MeV 0.15 - 0.6 mb

-G =100

MeV 0.15 - 0.7 mba few % of typical hadron production cross section.g N L K p (~8

mb

)

g

N



S

K

p (~4

m

b

)

B.E.



15 points (10-150

MeV

)

G



3 points

upper limits of cross section were determined

log likelihood ratio methodSlide12

Conclusion and future prospectThe existence of Kaonic

nuclei is not established.K-pp was searched for using g D

 K+ p - X reaction

No bump structures were found, and the upper limits of differential cross section were determined to be a few % of typical hadron production cross section.Future prospectdetect the decay products from K

-pp.  increase S/Nsearch for other charge states using gDK+ K-pn ,

gDK

+p+ K-nn2013/2/13GCOE Symposium @ Kyoto University11 / 11Slide13

Collaborators2013/2/13

GCOE Symposium @ Kyoto University12 / 15Slide14

Appendix2013/2/13

GCOE Symposium @ Kyoto University13 / 15Slide15

AppendixMeritdeuteron

 small nuclear effect(FSI).additional p- emission reduce the momentum transfer.K can be exchanged.polarization observable is available.

Demeritsmall cross section (~nbarn).many background sourcelimited information on hadron resonance.

necessary to detect the decay product.2013/2/13GCOE Symposium @ Kyoto University

14 / 15Slide16

Calculation of Upper Limits2013/2/13

GCOE Symposium @ Kyoto University15 / 15

preliminary

preliminary

Upper Limit was calculated with log Likelihood ratio methodBackground proces - g p  K

+ p-

L - g p  K+ p- S - g p  K+ p- S

(1385) - g p

 K

+

p

-

S

(1385)-

- g

p

 K

+

p

-

p L

constant offset

Signal

Breit

Wigner distribution

-2

D

lnL = 3.841

 upper limit (95% C.L.)

Signal YieldSlide17

Theoretical calculation2013/2/13

GCOE Symposium @ Kyoto University16 / 15

Binding EnergyDecayWidth

MethodYamazaki and Akaishi48 MeV

61 MeVPhenomenologicalVariatioal MethodDote, Hyodo and Weise20±3 MeV

40-70 MeVChiral

SU(3)Variational MethodIkeda and Sato60 – 95 MeV45 - 80 MeVChiral SU(3)Fadeev CalculationShevchenko,

Gal and Mares50 – 70

MeV

90 – 110

MeV

Phenomenological

Fadeev

Calculation

S.

Wycech

and

A. M. Green

56.5~78

MeV

39~60

MeV

Uchino

,

Hyodo

and Oka

depend on

L

* N

Variational MethodAll calculations predict that K

-pp can exist!!However… B.E. = 20 – 100 MeV G = 40 – 110 MeV Depending on the K N interaction model and Calculation Method.Slide18

Background processes2013/2/13

GCOE Symposium @ Kyoto University17 / 15

preliminary

15 quasi- free processes were considered for fitting.N

 Y K+ Y K+ p- Y* K+ p- Y K+ p- pThe main background (~20 %)n

 K+

L(1520)  Sp  Lpp g N  K+

p-

X

MM(K

+

)

MM(

K

+

,

p

-

)

MM(K

+

)

MM(

K

+

,

p

-

)

c

2

/

ndf

~ 1.3

Y

hyperon

(

L,S

)

Y*

hyperon

resonance (

L(1405),S(1385)

…)