The pp→pp00 reaction and its limiting case,

the fusion to quasibound ,

in search of ABC effect

T. Skorodko, University Tuebingen

for CELSIUS-WASA

► motivation and detector setup

► results and discussions

► summary and outlook

He2

ABC effect

M=2360 MeV

=90 MeV

(t-channel)

Roper

pre

limin

ary

WASA-at-COSY

“ABC” effect in ANKE data

pp→{pp}SX

selection:

Epp < 3 MeV,

cosθpp > 0.95

1.1 GeV

0.8 GeV

2 GeV

1.4 GeV

S.Dymov et al., PRL 102, 192301 (2009)

phase space

“ABC” effect in ANKE datapp→{pp}SX

selection: Epp < 3 MeV, cosθpp > 0.95

1100 MeV 1400 MeV

• final {pp} in

• asume S-wave in

initial protons in or

01S

01S

21D

only S-wave amplitude

only D-wave amplitude

S- and D-wave amplitudes

S.Dymov et al., PRL 102, 192301 (2009)

Mx [GeV/c2]

Oservation of an “ABC” effect in proton-proton collisions

pp→{pp}SX

S.Dymov et al., PRL 102, 192301 (2009)

“If ABC is not a resonance, it does not have to have a definite isospin …”

“… pp→{pp}SX kinematics are very similar to those of pn→d00 and

so a comparison with CELSIUS-WASA data is instructive”

“… we certainly have no evidence for an I=1 dibaryon …”

“… pp→{pp}SX kinematics are very similar to those of pn→d00 and

so a comparison with CELSIUS-WASA data is instructive”

pp→pp00 at 4 CELSIUS-WASA detector

Tp = 775, 895, 1000, 1100, 1200, 1300, 1360 MeV

p

pγ γ

γ

γ

production

CELSIUS-WASA

N* →N

N* →

L.Alvarez-Ruso et al., Nucl. Phys. A 633 (1998), 519L.Alvarez-Ruso et al., Nucl. Phys. A 633 (1998), 519

N* →N

N* →

00 production at Tp < 1 GeV

Valencia model A(tot) A(N*→N)+A(N*→)Tp=0.795 GeV COSY-TOF

1)(00*

0*

NN

NR

(PDG) 4)(00*

0*

NN

NR

At Roper mass M=1440 MeV

Tp=0.895 GeVAll theoretical curves are normalized in area to the data

00 production at Tp > 1 GeV

VC with readjusted N→ branch

Tp = 1 GeV Tp = 1.1 GeV Tp = 1.2 GeV Tp = 1.3 GeV

00 production at Tp > 1 GeV

VC with readjusted N*→ branch

VC with readjusted total N* strength (T. Skorodko et al., Phys.Lett. B 679 (2009) 30)

Tp = 1 GeV Tp = 1.1 GeV Tp = 1.2 GeV Tp = 1.3 GeV

00 production at Tp > 1 GeV

modification of the excitation

include relativistic corrections

reduce the contribution from ρ-exchange in excitation by an order of magnitude (Xu Cao et al., nucl-th:1004.0140, today plenary session)

00 production at Tp > 1 GeV

VC with readjusted N→ branch

VC with readjusted total N* strength

VC with readjusted total N* strength and with modified excitation

Tp = 1 GeV Tp = 1.1 GeV Tp = 1.2 GeV Tp = 1.3 GeV

Total pp→pp00 cross section

VC with readjusted total N* strength and with modified excitation

original VC

VC with readjusted

N→ branch

VC with readjusted

total N* strength

Comparison ANKE data with modified VC

VC with readjusted total N* strength and with modified excitation (ANKE cuts)

CELSIUS-WASA data with Mpp < 10 MeV cut

VC with readjusted total N* strength and with modified excitation (Mpp < 10 MeV cut)

Conclusions

pp00 production can be described by a conventional t-channel calculations with small contribution from ρ-exchange

no evidence is found for a significant ABC effect (no low mass enhancement in M)

since pp00 is isospin I=1 channel, it is not instructive to compare these data with isospin I=0 pn→d00 data

Outlook

pn→pn00

p+(nps) at Tp=1.0 GeV

p+(nps) at Tp=1.2 GeV

Tp Tp

ABC

WASA-at-COSY

Thank you