Two-proton simultaneous emission from 29 S C.J. Lin 1, G.L. Zhang 1, F. Yang 1, H.Q. Zhang 1, Z.H. Liu 1, C.L. Zhang 1, P. Zhou 1, X.K. Wu 1, X.X. Xu 1, G.P. An 1, H.M. Jia 1, N. Yu 1, and C.L. Bai 1 H.S. Xu 2, G.Q. Xiao 2, W.L. Zhang 2, Z.Y. Guo 2, Z.Y. Sun 2, and Z.G. Hu 2 1. China Institute of Atomic Energy, P.O. Box 275(10), Beijing , China 2. Institute of Modern Physics, The Chinese Academy of Science, Lanzhou 73000, China 中国原子能科学研究院 China Institute of Atomic Energy

June 6, 2007C.J. Lin / CIAE2 I.Introduction II.Two-proton halo/skin in 29 S III.Experimental procedure IV.Experimental results and 2 He emission from 29 S V.Discussion and summary Outline 中国原子能科学研究院 China Institute of Atomic Energy

I. Introduction Two-proton halo/skin:  found: 17 Ne, 29 S  candidate: 27,28 S … Two-proton emitter:  found: 45 Fe, 17,18 Ne, 29 S  candidate: 48 Ni, 54 Zn, 19 Mg, 27,28 S … Figure: Halo structures currently found in experiment this work

II. Two-proton halo/skins in S Figure: Density distributions of valence particlesFigure: Contributions of valence particles For the proton-rich sulfur isotopes, Z=16, 2p in the 2s 1/2 orbit. Calculated by single-particle potential model. c.f. C.J. Lin et al., Phys. Rev. C 66, (2002). S 2p = 0.9 MeV 2p

Experimental signature of 2p halo/skin in 29 S Figure: Z dependence of the d valueFigure: Experimental total reaction cross sections compared with theoretic calculations. Z.H. Liu et al., Chin. Phys. Lett. 21, 1711 (2004). Experiment: 29 S+ 28 Si, 42 MeV/u & 34 MeV/u modified Glauber model

III. Experimental procedure Primary beam: 36 Ar, 80.7 MeV/u Primary target: 9 Be, 512  m Degrader: 27 Al, 942  m Secondary beam: 29 S, 46.0 MeV/u, intensity  10 pps, purity  1% Secondary target: 12 C, 280  m Experiment was done at HILF-RIBLL of Institute of Modern Physics, Lanzhou.

RIBLL Experiment 2005 PPAC2PPAC1 12 C X1Y1StopX2Y2 CsI+PIN p p EE Collimators 27 Si 29 S Collimators:  30mm  &  20mm.  E: 150  m Si  E detector, combined with TOF (upstream) for particle identification. 12 C: target, 300  m. X1, Y1, X2, Y2 : 300  m Si strip  E detectors, 18 strips each, 1.2mm/strip with 0.1 mm interval. Stop: 300  m Si  E detector, for stopping all the heavy fragments. CSI: CSI(Tl)+PIN array, 24 segments, for light particle (p, d, etc.) identification. Target Chamber Z(mm)

CIAE-RIBLL-2005 detector array

Secondary beam identification 29 S 28 P 27 Si 26 Al 25 Mg 24 Mg 25 Al 26 Si 27 P 23 Na 22 Ne 28 Si 29 P 30 S 27 Al Beam time: 280 hours 1  S was accumulated

Proton removal cross sections 29 S:  1p = 3.15  0.32 b  2p = 1.85  0.20 b 28 P:  1p = 2.13  0.22 b IMP data: without any coincidence, M. Wang et al., High Energy Physics and Nuclear Physics 26, 803 (2002). CIAE data: coincide with heavy fragments this work. IV. Experimental results and 2p emission from 29 S Yields of light particles in 28 P, 29 S+ 12 C( 28 Si) reactions preliminary

Two-proton angular correlation function preliminary

Two-proton relative momentum distribution q = |p 1 -p 2 |/2 Relative momentum correlation function: 2p singlet s state c.f. M.A. Bernstein et al., Phys. Rev. Lett. 54, 402 (1985). preliminary 2p sequentially emitted

June 6, 2007C.J. Lin/CIAE13 V. Discussion and summary Preliminary results clearly show the signature of 2 He cluster emission. need more work:  eliminate the contribution of Si detectors  M-C simulations  HBT analysis for 1+R(q) to understand the source characteristics  invariance mass spectrum  …… 中国原子能科学研究院 China Institute of Atomic Energy

Thank you ! 中国原子能科学研究院 China Institute of Atomic Energy