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The dp →(pp) n Charge Exchange Channel

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  1. The dp→(pp)n Charge Exchange Channel V.V.Glagolev, G.Martinská, J.Mušinský,N.M.Piskunov, J.Urbán Joint Institute for Nuclear research, 141980 Dubna, RUSSIA P.J. ŠafárikUniversity, Jesenná 5, Košice, Slovak Republic J. Urbán

  2. The dp→(pp)n Charge Exchange Channel ABSTRACT An estimate of the spin dependent part of the np→ pnexchange amplitude was made on the basis of thedp→(pp)n data, taken at 1.67 AGeV/c in a full solid angle geometry. The np →pnamplitude turned out tobe predominantly spin dependent. To extend these studies to higher energies the designed experiment STRELAis well on the way to data taking and processing. J. Urbán

  3. The dp→(pp)n Charge Exchange Channel Outline • Introduction • Formalism • Experimental results • STRELA • Conclusion J. Urbán

  4. The dp→(pp)n Charge Exchange Channel • np→ pn charge exchange • dp →ppn reaction channel: - d is a fast system - the break-up predominantly processes as a quasi NN - charge exchange either np→ pn or via inelastic intermediate state Introduction J. Urbán

  5. The dp→(pp)n Charge Exchange Channel Introduction • dp →(pp)n charge exchange: - 2 protons in the same spin state - Pauli principle - What will come out of this state ? comparison : np →pn and dp →(pp)n J. Urbán

  6. The dp→(pp)n Charge Exchange Channel • Connects the dp →(pp)n charge exchange with the elementary np →pn process • The formalism is based on Pomeranchuk and Chew ideas, published in 1951 I. Pomeranchuk, Sov. JETF 21, 1113 (1951) G.F. Chew, Phys. Rev. 84, 710 (1951) Formalism J. Urbán

  7. The dp→(pp)n Charge Exchange Channel • The mathematical formalism elaborated by Dean is based on two assumptions, on the validity of: - impulse approximation and - closure approximation. N.W. Dean, Phys. Rev. D5, 1661(1972) and D5, 2832(1972) • R. Lednický and Lyuboshitz showed that at relativistic energies these two assumptions are justified Formalism J. Urbán

  8. The dp→(pp)n Charge Exchange Channel • Formalism • The differential cross section of the • elementary pnnp CE can be represented • as sum of the spin-independent (SI) & • spin-dependent (SD) parts: • (d/dt)nppn=(d/dt)SInp→pn +(d/dt)SDnp→pn J. Urbán

  9. The dp→(pp)n Charge Exchange Channel • Formalism • The differential cross section for dp→(pp)n CE break up in the framework of the impulse approximation and small t is (Dean, Wilkin): • (d/dt)dp(pp)n = [1-S(t)] (d/dt)SInp→pn+ [1-1/3S(t)] (d/dt)SDnp→pn • where S(t) is the deuteron form factor, • t is the 4-momentum transfer squared • from initial proton to neutron J. Urbán

  10. The dp→(pp)n Charge Exchange Channel • Formalism • At 0 scattering angle t=0, S(0)=1 and the formula reduces to • (d/dt)dp(pp)n = 2/3(d/dt)SDnp→pn • The CE break-up reaction of the unpolarizeddeuteron on the unpolarizedproton-target in the forward direction is determined by the spin-flip part of the nppn CE process at 0 scattering angles. Deuteron acts as a spin filter. This result also remains valid when the deuteron D-state is taken into account. J. Urbán

  11. The dp→(pp)n Charge Exchange Channel Formalism • To extract the information we compare our experimental data ( CE differential cross section at t=0) with the np→pn(CE cross section) data at the same energy available in the literature J. Urbán

  12. The dp→(pp)n Charge Exchange ChannelExperimental results The 1m HBC LVE JINR irradiated in beams of deuterons pd= 3.35 GeV/c. 17 dp channels identified About half of the statistics dp→ppnpionless break- up In total 237 413 events J. Urbán

  13. The dp→(pp)n Charge Exchange ChannelExperimental results d p →p p n: • Charge retention d p →(p n) p ~ 83 % • Charge exchange d p →(p p) n ~ 17 % • Neutron is the fastest secondary nucleon in deuteron rest frame • 17 512 events 5.85 ± 0.05 mb • This cross section include some part of quasi-pp events with intermediate Δ-isobaric state. J. Urbán

  14. The dp→(pp)n Charge Exchange ChannelExperimental results For IA and at higher energies the role of FSI ! Asymmetry A α= acos(psq) sensitive to FSI ps -spectator momentum d RF q - 3-momentum transfer from incident to scattering nucleons. FSI suppression J. Urbán

  15. The dp→(pp)n Charge Exchange ChannelExperimental results The basic part intermediate isobars is consequence quasi-рр and quasi- np collisions going through Δ0,Δ+ and Δ++ - isobars J. Urbán

  16. The dp→(pp)n Charge Exchange ChannelExperimental results In connection with the appreciable contribution of events with intermediate Δ - isobar it is necessary to enter the amendment on quasi-proton collisions Enhancement occurs above momenta of 0.2 GeV/c J. Urbán

  17. The dp→(pp)n Charge Exchange ChannelExperimental results For approximation of dp→(pp)n dσ/dt(t = 0) θLAB < 5° is safe. The 2 protons in LAB have practically identical momenta p1= p2 = pd/2 J. Urbán

  18. The dp→(pp)n Charge Exchange ChannelExperimental results Extrapolation of the dp→(pp)n differential cross section to t=0 : dσ/dt|t=0= 30.2±4.1 mb/(GeV/c)2 Be compared with that of np→pn . J. Urbán

  19. The dp→(pp)n Charge Exchange ChannelExperimental results • CE np→pn dσ/dt|t=0 using • G.Bizard et al: Nuclear Physics B85(1975) 14-30 • J.Bystricky, F.Lehar: Nucleon-Nucleon Scattering data, editors H. Behrens and G. Ebel, Fachinformationszentrum Karlsruhe,1978 Edition,N 11-1, p.521 • (dσ/ dt)|t = 0 = • 54.7 ± 0.2 mb/(GeV/c)2 J. Urbán

  20. The dp→(pp)n Charge Exchange ChannelExperimental results J. Urbán

  21. The dp→(pp)n Charge Exchange ChannelExperimental results Livermore, Moscow, Ruthefrord, UCRL, Harvard U., Harwell, JINR DLNP, PSI, INP Dubna, LAMPF, LRL, JINR J. Urbán

  22. The dp→(pp)n Charge Exchange Channel STRELA Drift chambers D1-D7 D1 - D5 125x125 mm2 D6 - D7 250x250 mm2 D xy, D uv 22.5° B= 1.7 T , 0.85 T rmax= 2.1 cm, tmax~ 450 ns J. Urbán

  23. The dp→(pp)n Charge Exchange Channel STRELA • new VME crates and modules tested • the basic characteristics of the drift chambers established • from irradiation of a polyethylen target with a deuteron • beam of 3.5 GeV/c momentum • the drift time tmin and tmax determined for each wire • drift time → radius r(t) transformation carried out: • - linear (on-line) • - cumulative/integral (off-line) J. Urbán

  24. The dp→(pp)n Charge Exchange Channel STRELA Track finding and reconstruction • track projection for each block of DC, block defined dymanically, 1block > 3 planes • track candidates : pairs fired hits from different planes are selected and combinations of tangentials computed • for tangetials the distance d to all fired wires is tested if d > dmincandiadate refused; dmin>> cham resolution • if the number of fired wires obeying previous step Nhit≥Nmin = 4 then the tangential → track candidate; if more than 1 candidate then that with min∑d used J. Urbán

  25. The dp→(pp)n Charge Exchange Channel STRELA Track finding and reconstruction • xz-track candidate parametrizedz=ax + b • distance from all Nhitis minimized and a,bdetermined usually in 2-3 iteration steps J. Urbán

  26. reconstructed track(s)‏ event 104, fully reconstructed 2 tracks event 104, small chamber 1X J. Urbán

  27. The dp→(pp)n Charge Exchange Channel STRELA Autocalibration • crucial role of r(t) for the track reconstruction • iterative correction to r(t) using reconstructed tracks • criterion: ∆r = residuals = distance of the reconstructed track to the wire, should have a Gaussian distribution with 0 mean • ∆r vs t constructed, divided into small t intervals, projected to ∆r and the mean is computed and the transformation t →r is corrected for this value … • usually 4 iteration steps are needed J. Urbán

  28. residual tdc : residual small chamber 3X (14 wires)‏ residual J. Urbán

  29. residual small chamber 1Y n u m b e r o f i t e r a t i o n J. Urbán

  30. iteration 1 event 122, big chamber X iteration 4 J. Urbán

  31. σ ~ 89 μm big chamber X iteration 1 iteration 4 σ ~ 122 μm small chamber 1X J. Urbán

  32. The dp→(pp)n Charge Exchange Channel Conclusion • The obtained ratio of the charge exchange differential cross sections at t=0 for d p →(p p) nandnp → pn reactions R = 0.55 ± 0.08 testifies the prevailing contribution of the spin-dependent part to the np →pncross sectionscattering • Continuation of researches at higher energieson STRELA set up is important • STRELA electronics (VME + modules) tested • Track reconstruction for STRELA drift chambers tested • Auto-calibration improves the reconstruction quality • STRELA is ready for data taking and processing J. Urbán

  33. The dp→(pp)n Charge Exchange Channel Acknowledgement This work was supported by the Slovak Grant Agency VEGA under number VEGA 1/4010/07 J. Urbán

  34. Thank you for • the attention J. Urbán

  35. J. Urbán