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## The dp →(pp) n Charge Exchange Channel

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**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**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**The dp→(pp)n Charge Exchange Channel**Outline • Introduction • Formalism • Experimental results • STRELA • Conclusion J. Urbán**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**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**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**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**The dp→(pp)n Charge Exchange Channel**• Formalism • The differential cross section of the • elementary pnnp CE can be represented • as sum of the spin-independent (SI) & • spin-dependent (SD) parts: • (d/dt)nppn=(d/dt)SInp→pn +(d/dt)SDnp→pn J. Urbán**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**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 nppn 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**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**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**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**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**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**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**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**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**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**The dp→(pp)n Charge Exchange ChannelExperimental results**J. Urbán**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**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**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**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**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**reconstructed track(s)**event 104, fully reconstructed 2 tracks event 104, small chamber 1X J. Urbán**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**residual**tdc : residual small chamber 3X (14 wires) residual J. Urbán**residual**small chamber 1Y n u m b e r o f i t e r a t i o n J. Urbán**iteration 1**event 122, big chamber X iteration 4 J. Urbán**σ ~ 89 μm**big chamber X iteration 1 iteration 4 σ ~ 122 μm small chamber 1X J. Urbán**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**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**Thank you for**• the attention J. Urbán