Institut für Kernphysik Vera Kleber1 Trento, 16.06.2005 Universität Bonn Physikalisches Institut a 0 (980) – f 0 (980) Mixing Vera Kleber Physikalisches

Institut für Kernphysik

Vera Kleber 1Trento, 16.06.2005

Universität BonnPhysikalisches Institut

a0(980) – f0(980) Mixing

Vera Kleber

Physikalisches InstitutUniversität Bonn

Institut für KernphysikForschungszentrum Jülich




Outline

Introduction

Properties of a0(980)/f0(980)

Experiments with a0(980)/f0(980)

a0(980)-f0(980) Mixing

Program at COSY

Outlook




S

I

1

-1 1

-1

The Pseudo Scalar Resonances

K+

K- K0

K0

- 0 +

Nonet of pseudo scalar mesons JP=0-




S

I

1

-1 1

-1

The Light Scalar Resonances

f0(500) (““)(800)f0(980)a0(980)f0(1370)

K0*(1430)a0(1450)f0(1500)f0(1710)

Possible candidatesNonet of light scalar mesons JP=0+

K0+*(?)

K0-*(?) K0

*(?)

K0*(?)

a0-(?) a0

0(?) f0(?) a0+(?)

f0(?)

PDG, S. Eidelman et al., Phys. Lett. B 592, 1 (2004)




a0(980)/f0(980) Nature

What is their nature?

qq stateor

4 quark state or

KK molecule

A.V. Anisovich et al., Eur. Phys. J A 12 (2001) 103D. Morgan, M.R. Pennington, Phys. Rev. D 48 (1993) 1185

N.N. Achasov et al., hep-ph/0201299R.J. Jaffe, Phys. Rev. D 15 (1977) 267

J.A. Oller, E. Oset, Nucl. Phys. A 620, (1997), 438G. Janssen et al., Phys. Rev. D 52 (1995) 2690J. Weinstein, N. Isgur, Phys. Rev. D 41 (1990), 2236




The a0(980) Resonance

a0(980)

IG(JPC) 1-0++

Mass 984.7 ± 1.2[MeV]

Width 50 – 100 [MeV]

Decaysdominant seen KK seen





The f0(980) Resonance

f0(980)

IG(JPC) 0+0++

Mass 980 ± 10[MeV]

Width 40 – 100 [MeV]

Decaysdominant seen KK seen





The a0(980) and f0(980) Resonance

E. Bratkovskaya et al., J. Phys. G 28 (2002) 2423

d

dM

√(0)Mr

Mr2-M2-iMrKK

= C

gq

ig√(K2 – (M/2)2)

g√((M/2)2 - K2)

below threshold:

above threshold:

2




Experiments: Inclusive pp→ d X+ Data

M.A. Abolins et al., PRL 25 (1970) 469

pp = 3.8, 4.5, 6.3 GeV/c

p p → d X+

LBL




Experiments: Radiative -Decays

KLOE @ DANE

75

50

25

0

dB

R/d

m x

10

8 (

MeV

-1)

400 600m() (MeV)

1000800

e+e- → →

A. Aloisio et al., Phys. Lett. B 537 (2002) 21

→ (f0(980) + )

→ f0(980)

→ Interf.




Experiments: f1(1285) Decays

L3 @ LEP

e+e- → e+e- → e+e-f1(1285) → e+e- → e+e-

L3 Collaboration, Phys. Lett. B 526 (2002) 269

BW-FitM=98546=50134

a0(980)f1(1285)




021.510.5 1 1.2 1.4

m2(KL+/KL-) / GeV2 m2(KLK+/KLK-) / GeV2

Experiments: pp annihilation

Crystal Barrel @ LEAR

pp → KLK+/--/+

a0(1450)

KLK+/-

a0(980)

a0(1320)

a0(1450)

A. Abele et al., Phys. Rev. D 57 (1998) 3860

en

trie

s /

0.0

18

6 G

eV

2/c

2

K*(892)

a0(980)

a0(1320)

200

400

600

theoretical Dalitz Plot(from bestfit of PWA)

Flatté

m=9823

=928

g1=324 15

g2/g1=1.01

m2(K

+-

/K-

+)

/ G

eV

2

2

1.5

1

0.5

1.6




Experiments: J/Ψ Decays

BES @ BEPCe+e- → J/Ψ → e+e- → J/Ψ → K+K-

M. Ablikim et al., hep-ex/0411001

f0(980) f2(1270)/f0(1370) f0(980)

f‘2(1525)

Flatté

m=96586

g1=1651015

g2/g1=4.21

0.25 0.21




a0(980)/f0(980) Nature

What is their nature?

qq stateor

4 quark state or

KK molecule

Which observable to measure at COSY?

→ a0(980) - f0(980) mixing amplitude

M g gK R

1001

0.218 0.224

1.03

999 0.445 0.516

1.16

999 0.215 0.222

1.03

995 0.389 1.414

3.63

985 0.376 0.412

1.1

1003

0.476 0.834

1.75

992 0.453 0.56 1.24

M g gK R

970 0.417 2.51 6.02

975 0.317 1.51 4.76

973 0.538 2.84 5.28

977 0.09 0.02 0.22

- 0.19 0.40 2.11

957 0.09 0.97 10.78

g=g2/8m2 R=gKK

2/g2

a0(980)

V. Baru et al., nucl-th/0410099

g=g2/8m2 R=gKK

2/g2

f0(980)

V. Baru et al., nucl-th/0410099




a0(980)-f0(980) Mixing

• idea similar to dd 0 experiment @IUCF

• search for a reaction forbidden due to isospin conservation:

dd a00(980) ( 0)

• allowed due to isospin conservation:

dd f0(980) ( )

• a0(980)-f0(980) mixing:

dd f0(980) a00(980) 0




a0(980)-f0(980) Mixing

• pilot measurement at ANKE:

our estimate: (dd f0(980) K+K–) ~ 400 pb

• strength of a0(980)-f0(980) mixing unknown

• isospin violating reaction at WASA:

our estimate: (dd a0

0(980)) ~ (50 ... 200) pb

Close & Kirk: mixing intensity = 8±3%

but critizised by Achasov & Kiselev, Oller




dd 0 vs. dd (0)

CSB inpropagationof a0/f0

productionor 0/

d d

0

d d

0

<<d d

a0

d d

f0

a0

Details: C.Hanhart, nucl-th/0306073

20Production

PropagationCSB a0/f0

mN( )≈ ( )≈

-mNma0/f0

11t ≈~

ma0/f0a0/f0

1~




a0(980) - f0(980) Mixing-Amplitude

N.N. Achasov et al., Phys. Lett. B 88, 367 (1979)

d/dm ~ |(m)|2 * |A|2

Isospin violation reaction: dd → f0→a0→

~ i gf0KK ga0KK √s(pK –pK)

→ kaonic contribution

additional measurement:

dd → K+K-

mK02 – mK+

2

mK02 + mK+

2

md – mu

(md + mu)/2+ ms

~ √( ) = √( )f0 a0

K0

K0f0 a0

K–

K+

+ others- =

m




Forschungszentrum Jülich

Aachen Köln

Bonn

~ 30 km~ 50 km

~ 70 km




COSY Jülich

Meson Production

pp → pp X m(X) < 1.1 GeV/c2

pp → d X

dd → X




COSY Jülich

Meson Production

pp → pp X m(X) < 1.1 GeV/c2

pp → d X

dd → X

Isospin I(I3)

1(½,½) → 1(½,½,0)

1(½,½) → 1(0,1)

0(0,0) → 0(0,0)




a0(980) Production near Threshold

ANKE

pp → da0+(980) → dK+K0

→ dTp =

2.65 GeV

QKK = 48 MeV

Tp = 2.83 GeV

QKK = 105 MeV




Identification of pp d

P. Fedorets et al., accepted by Yad. Fiz. (Phys. At. Nucl.)




Branching Ratio a0+ → (K+K0) / (π+η)

model dependent

BR = (2.9 ± 0.8stat ± 0.9sys) %

BR = (23 ± 5) %

A. Abele et al., Phys. Rev. D 57, 3860 (1998)

Rati

o

10-1

10-2

Q [GeV]0 0.1 0.2 0.3

ANKETp = 2.65 GeVQ = 48 MeV

P. Fedorets et al., accepted by Yad. Fiz. (Phys. At. Nucl.)




Identification of pp dK+K0




Differential Distributions for pp dK+K0

V.Kleber et al., Phys. Rev. Lett. 17, 172304

T =2.65 GeV (Q =48 MeV) tot(pp → dK+K0) = (38 ± 2stat ± 14sys) nb

→ 83% a+0

channel

Fit:Fit:[(KK)P d]S + [(KK)S d]P




pp dK+K0 at Higher Energy

T =2.83 GeV (Q =105 MeV)preliminary

black:best fit (in acc.)green:initial distrib.red:KK s-wave contrib.blue:KK p-wave distrib.

cos (pK+)

ndf2

= 2.5

→ 85% a+0

channel




Outlook

dd K+K- @ ANKE

• reaction serves as isospin I=0 filter

• isospin conservation: f0

dd → π0η @ WASA

Planned measurements:

• forbidden if isospin is conserved

• mixing f0 a0

Goals:• dσ/dm (dd → απ0η ) dσ/dm (dd → αK+K-)

→ |mixing amplitude|2

Goals:• cross section (dσ/dm)




… What You Should Have Learned …

Introduction

Properties

Experiments

a0-f0 Mixing

Program at COSY

Outlook

→ internal structure unknown

→ from mass distributions: 2 out of 3 unknowns (M and g2

2/g12 )

→ contains information on internal structure

→ another reaction to study CSB

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Institut für Kernphysik Vera Kleber1 Trento, 16.06.2005 Universität Bonn Physikalisches Institut a 0 (980) – f 0 (980) Mixing Vera Kleber Physikalisches