Two-pion program at WASA

Mikhail BashkanovEncounters with Di-Baryons from the ABC-effect to a Resonance in the Proton-Neutron System

Wasa-at-COSY1Content2Double-pionic fusion3npnpppThe ABC-effect4npnpppHistory of the ABC effectLow mass enhancement in M

Alexander Abashian, Norman E. Booth Kenneth M. Crowe, Phys. Rev. Lett. 5, 258 (1960)

M.Bashkanov et. al, Phys. Lett. B637 (2006) 223-228

P. Adlarson et. al, Phys. Rev. C86 (2012) 032201P. Adlarson et. al, Phys. Rev. Lett. 106 (2011) 242302Two-pion production6N*DDDN*sDD(1600)Tp < 1.5 GeV

Isospin Decomposition

T. Skorodko et al.,PLB 679 (2009) 30N*(1440)DDD(1600)7Expectations in total cross section

89

ABC resonance70 MeVTotal cross section pn d00 P. Adlarson et. al Phys. Rev. Lett. 106:242302, 2011NN*(1440)10

Angular distribution in the peak

J=1J=3Quantum numbers of the structureAntisymmetrization: Jp=1+or 3+ : if L=0

pn d* d 00 pn d 00I=0,1I=0I=0,2I=01+3+

1+ excluded by ().3+ assigned 1112

t-channel ABC effectM for different energies13Status of Theoretical Descriptionpn R DD dp0p0

dpnI(Jp) = 0(3+)Isospin relations14I=0I=115Total cross section pN d P. Adlarson et. al Phys. Lett. B721 (2013) 229

16M in pN d

17M in pN d

18M in pN d

Isospin violation

19+-00Non-fusion channel2021

pn pp-0ABC expectedPreliminaryConventional processConventional process +ABCP. Adlarson et al., arXiv: 1306.5130v1Elastic channel22233+ Resonance in npnpL=2npL=424Total pn cross-section

SAIDDevlin et al, PRD8, 136 (73) LisowskI et al, PRL49, 255(82)25

Expectationspnnp

SAIDSAID with resonance

26Expectationpnnp

SAID

27Realitypnnp

SAID

28pn Vector Analysing Power

SAIDVery PreliminaryConclusion29Thank youMultiplet1010=35282710**Y()=2I()=0Kim Maltman, Nucl. Phys. A501 (1989) 843Mirror dibaryon32DDI(Jp) = 0(3+)d*uuudddI(Jp) = 3(0+)DDuuuuuuMirror Multiplet1010=35282710***+***+**+**++++--Beam polarization0Polarization 2Polarization 1

35Total cross section pp d+0 Shimizu et al.F. Kren et al.

36Total cross section pn d00

37Total cross section pn d+-

38Total cross section pn d+- Kinematics

39Proton spectatorprotonneutrondpnp + psp40Status of the ABC Resonancedecay channel branching status------------------------------------------------------------------------d p0p0 15 % observedd p+p- 25 % observed ppp0p- 7 % observednpp0p0 (12 %, predicted*) data analysis WASAnpp+p- (31 %, predicted*) data analysis HADESnp (10 %, predicted) data analysis WASA

* Fldt & Wilkin, PLB 701 (2011) 619 Albaladejo & Oset, arXiv:1304.7698 [nucl-theor]