1. Study of the 3He-η System in d-p Collisions
J. Smyrski
Jagiellonian University
Cracow, Poland
Results of COSY-11 measurements of:
dp  3He  close to threshold
dp  3He o production at  threshold
dp  3He X threshold excitation curve
25 August 2006
FB-18 Conf., Santos, 2006

2. Study of the  - 3He interaction
above 3He- threshold
dp 3He
(enhancement of the cross sections due to the 3He FSI)
below 3He- threshold
dp 3He  3He o
 d p o
 pp p-
 dp
 …
(resonance-like structures in the excitation functions)
bound state
25 August 2006
FB-18 Conf., Santos, 2006

3. 3He-η scattering length
dp 3He
questions:
inconsistencies between data sets
contributions from higher partial waves
to σ tot at Q <10 MeV
|aR|> aI (?) (necessary condition for bounding)
data very close to threshold (Q <1 MeV )
needed
(A. Sibirtsev et al., Eur. Phys. J. A22(2004)495)
|f|2 =
|fp|2
1+2aI q+|a|2 q2
Scattering length
a=| |+i( ) fm
25 August 2006
FB-18 Conf., Santos, 2006

4. 3He-η interaction below threshold
γ 3He  pπ0 X data from MAMI
(M. Pfeiffer et al., Phys. Rev. Lett. 92(2004)252001)
Binding energy:( -4.4  4.2) MeV
Width: 25.6  6.1 MeV
25 August 2006
FB-18 Conf., Santos, 2006

5. Structure at the  threshold
Bound state
Re(a) > 0
Virtual state ?
3He 
V. Baru, J. Haidenbauer, C. Hanhart and
J. A. Niskanen, Phys. Rev. C68(2003)035203
aR + iaI = (+3.8+i1.6)fm
- mixing
R =
ds/dW (pd  3H p+)
ds/dW (pd  3He p0) =
pp |Tp+ |2
pp0 |Tp0 + qmTh |2 ~
25 August 2006
FB-18 Conf., Santos, 2006

6. Internal COSY beam: ~ 3x1010 deuterons
Q(dp 3He )
[MeV]
Pbeam
[GeV/c]
Slow ramping
Frequency spectrum 9
3.179
3.141
-10
3.099
5 min t
Δf= 0.2 MHz 
Δp = 1.7 MeV/c
ΔQ = 0.4 MeV
25 August 2006
FB-18 Conf., Santos, 2006

7. COSY-11 detection system
T1: dp 3HeX, X= o, 
T2: dp 3H+,
T3: dp  dp 
T4: dp  dp, pp  pp (QFS)
T5: dp  dpo
T6: dp  ppp-
T7: dp  dp
25 August 2006
FB-18 Conf., Santos, 2006

8. Identification of 3He TOF - p m2 / q2 ΔE - p 25 August 2006
FB-18 Conf., Santos, 2006

9. CM momentum distribution 
25 August 2006
FB-18 Conf., Santos, 2006

10. Missing mass  
25 August 2006
FB-18 Conf., Santos, 2006

11. Beam momentum determination
Correction: Δplab =  (stat.)  0.48 (syst.) MeV/c
25 August 2006
FB-18 Conf., Santos, 2006

12. Background subtraction
3.166 GeV/c < pbeam < GeV/c Q ~ 6.5 MeV
Background:
3.134 GeV/c < pbeam < GeV/c
25 August 2006
FB-18 Conf., Santos, 2006

13. dp elastic and pp quasi-elastic scattering
25 August 2006
FB-18 Conf., Santos, 2006

14. Luminosity determination
dp elastic
pp quasi-elastic
25 August 2006
FB-18 Conf., Santos, 2006

15. TOT (dp 3He) Preliminary Transition amplitudes: L= 0 J=1/2 T0
25 August 2006
FB-18 Conf., Santos, 2006

16. dp  3He o at -threshold
Fig. from C. kerboul et al., PL B181(1986)28
COSY-11
COSY-11
3He threshold
(dp  (3He -) bound  3He o ) < 0.07 b
Further search: dp  (3He -) bound  ppp -
25 August 2006
FB-18 Conf., Santos, 2006

17. SATURNE pd  3He X threshold excitation curve
results
Spectrometer
momentum
acceptance
C. Wilkin, in “Production and Decay of Light Mesons”,
edited by P. Fleury, p.187
25 August 2006
FB-18 Conf., Santos, 2006

18. COSY-11 pd  3He X threshold excitation curve
mmax- 0.5 MeV < mm < mmax
mmax- 1 MeV < mm < mmax
3He threshold
25 August 2006
FB-18 Conf., Santos, 2006

19. dp  dp η cross sections Preliminary Experiment TOT (dp 3He)
for Q = 3.6, 6.5, 9.6 MeV
Missing mass
Preliminary
25 August 2006
FB-18 Conf., Santos, 2006

20. Search for the 4He– h bound state in d-d collisions
Princilple of measurements
Experiment - d
3He d p
p-- back-to-back emission: θcm ~180˚
3He is a spectator : pcm ~50 MeV/c,
θlab ~ 50/1500 rad = 1.9˚
25 August 2006
FB-18 Conf., Santos, 2006

21. Summary
High statistics data collected for the dp 3He very close to threshold;
strong 3He- S-wave interaction confirmed;
the cross sections will be published soon
No narrow structures observed in the excitation curve
for dp  3Heo near the  production threshold,
but 3He- bound state is still not excluded
The cusp structure observed at the SATURNE threshold excitation curve below the  peak was not confirmed
Planned search for the 4He- bound state
in the dd 3He p- reaction
25 August 2006
FB-18 Conf., Santos, 2006

22. dp elastic scattering at backward cm angles
25 August 2006
FB-18 Conf., Santos, 2006

23. Excitation curve for the dp elastic scattering
25 August 2006
FB-18 Conf., Santos, 2006

24. COSY-11 detection setup T1: dp  dp  T2: dp 3HeX, X=  o, 
T3: dp  dp, pp  pp (QFS)
pbeam Q (dp 3Heη)
[GeV/c] [MeV]
25 August 2006
FB-18 Conf., Santos, 2006

25. Missing mass distributions dp  dp X
25 August 2006
FB-18 Conf., Santos, 2006