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

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

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=|3.8+0.6|+i(1.6+1.1) fm 25 August 2006 FB-18 Conf., Santos, 2006

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

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

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

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

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

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

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

Beam momentum determination Correction: Δplab = -2.013  0.002 (stat.)  0.48 (syst.) MeV/c 25 August 2006 FB-18 Conf., Santos, 2006

Background subtraction 3.166 GeV/c < pbeam < 3.170 GeV/c Q ~ 6.5 MeV Background: 3.134 GeV/c < pbeam < 3.138 GeV/c 25 August 2006 FB-18 Conf., Santos, 2006

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

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

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

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

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

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

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

Search for the 4He– h bound state in d-d collisions Princilple of measurements Experiment WASA@COSY - 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

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

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

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

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] 3.165 5.7 3.179 9.1 3.191 12.0 3.204 15.1 25 August 2006 FB-18 Conf., Santos, 2006

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