Vera Kleber

1Bosen, 07.09.2005

PI

Λ ΛΛΛ(1405) Ph

otop

roduc

tion

at CB-ELSA

Vera Kleber

Physikalisch

es Institut

Unive

rsität Bon

n

BOSEN 2005

Vera Kleber

2Bosen, 07.09.2005

PI

Out

line

Motivation

Acc

ess to Λ(1405)

and availab

ledata

Λ(1405) at CB-E

LSA

Outlook

Vera Kleber

3Bosen, 07.09.2005

PI

What‘skno

wn…

Λ(1405)

0(1/2

- )

1406.5±4

.0

50 ±

2

Σ0π0

(33%)

Σ+ π

-(33%)

Σ- π

+(33%)

PDG

Σ0(1385)

I(J

P )1(3/2

+ )

Mass

1383.7 ±

1.0

[MeV]

Width

36 ±

5

[MeV]

Decay

Σ+ π

-( 6%)

Σ- π

+( 6%)

Λπ0

(88%)

S=-1, Σ

0= ud

sS=-1, Λ

0= ud

s

S. Eidelmanet al., Phys. Lett. B 592, 1 (2004)

Vera Kleber

4Bosen, 07.09.2005

PI

Where

doe

sit

come fro

m…

Data:

R.J. Hemingw

ay,

NP B 253 (19

85) 742

Ana

lysis:

R.H. Dalitz, A. Deloff,

JPG

17 (19

91) 289,

M-M

atrix fit

→14

06.5±4.0

50±2

Σ* (16

70)+→

π+Λ(1405)→

π+(πΣ)0

m(π+Σ

)m(K+N)

m(π

− Σ+ )

Vera Kleber

5Bosen, 07.09.2005

PI

Strang

e Particle…

•Dalitzan

d Tua

npredicted(1959) a subth

resh

oldKN resona

ncefrom

K- p sca

ttering

data

→Λ(1405) was disco

vere

da fe

wye

arslater;

only

30 M

eV belowKN thre

shold

•locatedcloseto m

anyth

resh

olds

πΛπ0Σ0 π−Σ+π+Σ−

K- p

K0n

Λ(1405)

Mass

Vera Kleber

6Bosen, 07.09.2005

PI

Lambda S

tate

sin Q

uark

Mod

el

L=1

S=1/2

Vera Kleber

7Bosen, 07.09.2005

PI

Struc

ture

of theΛ ΛΛΛ(1405)

large theoretica

leffort

•qu

arkmod

elstatewithorbital excitation

→massdege

neratedpa

rtne

rwithJ

P =3/2

-

Λ(1520): 115

MeV away

•KN m

olecu

le,dyn

amically

gene

rated

→an

otherJ

P =1/2-Λ near

theΛ(1520)

unob

served

•χ symmetry: dou

ble struc

ture

@ 1405 M

eV

Λ(1405)

Λ(1520)

JP =1/2-

JP =3/2

-

D. Jidoet al.,

Nuc

l. Ph

ys. A

725 (2003) 18

1

a.u.

Λ(?)

Λ(1520)

Vera Kleber

8Bosen, 07.09.2005

PI

Acc

ess

to Λ ΛΛΛ(1405)

aboveKN thre

shold

K- p sca

ttering

data

at KN thresh

old

kaon

ichyd

roge

n

belowKN thre

shold

πΣmassdistribution

Vera Kleber

9Bosen, 07.09.2005

PI

K-p Sca

ttering

J. A. Olle

r, U

.-G. Meissner,

Phys. Lett. B 500 (2001) 263

available

data

aboveKN thresh

old:

→KN sca

ttering

leng

th

→ H

emingw

ay data

canbedescribed

K- p →

K- p

K0n

π+Σ−

π−Σ+

π0Λ

π0Σ0

Vera Kleber

10Bosen, 07.09.2005

PI

Kaon

icHydro

gen

DEAR@DAΦNE

Kao

nicHyd

roge

n

→energysh

iftan

d width

→K- p sca

ttering

leng

th

→Con

sequ

enc

esfo

rΛ(1405) line

shap

e

DEAR

KEK

Γ[eV]

∆E [eV]

Borasoy

et al.,

arXiv:hep-ph

/0505239

M. Cargn

elliet al.,

Int. Mod

. Ph

ys. A20 (2005) 341

Vera Kleber

11Bosen, 07.09.2005

PI

πΣ πΣπΣπΣMass

Distribut

ion: L

EPS

γp→

K+ X

J.K. Ahn, N

ucl. Ph

ys. A 721 (2003) 715

c

LEPS

Vera Kleber

12Bosen, 07.09.2005

PI

πΣ πΣπΣπΣMass

Distribut

ion: L

EPS

γp→

K+ π

+/− Σ

−/+

cuton

m(X

) = m(Σ)

Σ0 (13

85) →

πΣ←

Λ(1405)

66%

12%

π+Σ-

π−Σ+

Λ(1405)

(Σ(1385))

Λ(1520)

J.K. Ahn, Nucl. Phys. A 721 (2003) 715c

Vera Kleber

13Bosen, 07.09.2005

PI

πΣ πΣπΣπΣMass

Distribut

ion: C

rystal Ball

K- p →

Σ0 π

0 π0

↑Λ(1405)

↓Λ(1520)

--ph

asespace

→7γ n

↓ Λγ

↓ π0n

p K-=

581 MeV/c

687 M

eV/c

714

MeV/c

750 M

eV/c

Σ0

Σcu

tan

d bg

subtrac

tion

Vera Kleber

14Bosen, 07.09.2005

PI

TwoΛ ΛΛΛ(1

405) Reso

nanc

es

V.K. Mag

aset al., hep-ph

/0503043

TwoΛ(1405): in expe

rimentssupe

rpositionis

seen

→diffe

rent reac

tion

sca

npick

up th

epo

leswithdiffe

rent streng

th

Vera Kleber

15Bosen, 07.09.2005

PI

Plans

for

Λ(1405) at CB-E

LSA

•massdistribution

invarian

t massof

(Σ0 π

0 ) system

or

missing

massof

K+

•t-distribution

mom

entum

tran

sferto Λ(1405)

ift-ch

anne

ldom

inan

t

→ac

cess

to pK-scattering

amplitud

ebelowth

resh

old

γp→

K+ Λ(1405) → K

+ n5γ

Λγ

Σ0π0

nπ0

Vera Kleber

16Bosen, 07.09.2005

PI

Dom

inant

Pro

duc

tion

Mech

anism

M. Lutz, M

. Soy

eur, arXiv:nuc

l-th

/0407115

Λ(1405)

Vera Kleber

17Bosen, 07.09.2005

PI

Phot

ondete

ctionwith

Cry

stal Barrel

1380 CsJ

(Tl) crystals

angu

lar rang

e12

o –16

8o

solid ang

le0.95 x 4π

δE/E

2.5% @

1 GeV

δθ/θ

∼ ±2o

Vera Kleber

18Bosen, 07.09.2005

PI

Kaon

Ident

ification

kaon

identificationvia itsmass

→expe

rimentally

difficu

lt

equ

vialent:

velocity

and m

omentum

→ve

locity

via time-of-flight(T

OF)

(and

kno

wndistanc

es)

→mom

entum

via mag

neticfield

deflection→

mom

entum

Vera Kleber

19Bosen, 07.09.2005

PI

Cry

talBarrel + M

agn

eticSpe

ctro

mete

r

MOMO:

673 scintillating

fibers

2.5 m

m diameter

3 lay

ers

TOF:

plasticscintalla

torbars

3 x 3 x 0.2 m

3

Crystal

Barre

l

Dipole

0.6 Tm

Track

Detectors

Vera Kleber

20

Bosen, 07.09.2005

PI

TOF versus

Mom

ent

um

→K+ identificationup

to 12

00 M

eV (black

line

)

Simulation: Andre Süle

Vera Kleber

21

Bosen, 07.09.2005

PI

Altern

ative

: CB +

MOMO +

TOF

MOMO:

673 fibers

2.5 m

m diameter

TOF:

plasticscintalla

torbars

3 x 3 x 0.8 m

3

Crystal

Barre

l

Vera Kleber

22

Bosen, 07.09.2005

PI

K+Ident

ification

with

TOF W

all

→K+ identificationup

to 600 M

eV (black

line

)

TOF @

5.3 m

Stefan Höffgen

Vera Kleber

23

Bosen, 07.09.2005

PI

Sum

mary

I

Λ(1405):

well estab

lish

edstateof

unk

nownstructure

3q state↔

KN m

olecu

le↔

twoΛ(1405)

notmuc

hexpe

rimental dataso far

Plan

for

CB-E

LSA: γp→ K

+ Λ(1405) → K

+ n5γ

•5γwell suitedfo

rCB

•K+ (and

n) ID withTOF / M

agn. Spe

ctr.

Vera Kleber

24

Bosen, 07.09.2005

PI

Sum

mary

II

Bene

fitof

this

measurement:

clean

chan

nel(no co

ntributionfrom

Σ(1385))

t-distribution

ift-ch

anne

ldom

inates

→ac

cess

to K

- p sca

ttering

amplitud

ebelowth

resh

old

onemorech

anne

lto test m

assdistributions