Two pion production in protonproton collisions

1
Two pion production in proton-proton collisions
T. Skorodko, Physikalisches Institut,
Univ.Tuebingen for WASA
collaboration

• Motivation
• Data at Tp lt 1GeV
• Data at Tp gt 1Gev
• Conclusion and outlook

2
Motivation
pp ? pppp- PROMICE/WASA,
CELSIUS-WASA pp ? ppp0p0 PROMICE/WASA,
CELSIUS-WASA pp ? pnpp0 PROMICE/WASA,
CELSIUS-WASA pp ? nnpp
CELSIUS-WASA pp ? dpp0
CELSIUS-WASA
3
Motivation
pp ? pppp- pp ? ppp0p0 pp ? pnpp0 pp ?
nnpp pp ? dpp0
4
Experimental and theoretical situation
5
Roper excitation
Phys.Rev.Lett. 88, 192301(2002) Phys.Rev. C 67,
052202(R)(2003)
6
Dynamic s formation
20 (2005) 674
7
Dynamic s formation
20 (2005) 674
8
Dynamic s formation Total cross section
20 (2005) 674
PROMICE/WASA
CELSIUS-WASA
9
WASA 4p detector
10
Roper excitation
pp-?p0p0
Roper parameters optimized for pp-
Roper parameters optimized for p0p0
11
Tp gt 1 GeV
pp?pppp-
(DD)0
(DD)0-3
12
Tp gt 1 GeV
pp?ppp0p0
1000 MeV
1100 MeV
1200 MeV
13
Measurement of p-p?p0p0n from threshold to pp750
MeV/c
Crystal Ball
Phys.Rev. C 69, 045202(2004)
14
pp ? nnpp ? Bose-Einstein Correlations ?
p
D
(p0)
pp ? nnpp
(ppp0p0)
D
p
(p0)

• two identical bosons in final state
• DD intermediate state

15
pp ? nnpp Tp 1100 MeV
p r e l i m i n a r y
(DD)0
no
Bose-Einstein correlations
?
16
Conclusions and Outlook
?
Tp lt 1 GeV
?
Roper excitation ? dynamic s formation

pp ? pppp

• Tp 1 GeV
• ? dominant
• ? p0p0 unexpected enhancement in Mpp
• not BEC, since no enhancement in
• pp channel !
• dynamic isospin violation in I0 channel ?
• connection to 3He case( see next talk)?
• ??

Outlook

• WASA_at_COSY
• quasifree pp production on neutron

17
One pion production
895 MeV
pn?ppp-
(p)
(p)
pp?ppp0