1. Praha-Spin-20051 SPIN EFFECTS IN FRAGMENTATION OF GEV POLARIZED DEUTERONS L.S. Zolin Joint Institute for Nuclear research Dubna

2. Praha-Spin-20052 Outline Introduction Study deuteron breakup and backward dp-elastic at Saclay and Dubna facilities and problems at explanation of Nd(k ), T 20, k o - data at k > 0.25 GeV/c GeV polarized deuteron beams as tool to study a spin structure of short range NN-forces Study d  A  p X in cumulative regime as means to investigate the deuteron core spin structure Analyzing powers Ayy(xc,Pt) and Ay(xc,Pt) in d  A  p X Comporision SSA in d  A  p X and p  A  p X Conclusion

3. Praha-Spin-20053 E >1GeV - the region of accelerator physics where interests of particle physicists and NN-force physicists are overlapped: The structure of the short-range NN-force cannot be understood without knowledge of nucleon substructure. Information on SR NN-forces can be extracted : in DIS experiments with light nuclei, available rNN-scale is limited by low cross sections of (e,l )N-reactions ; a)in the reaction of nuclei fragmentation with use h-probes (NA,piA), very low rNN are available (~ 0.2 fm) but interpretation is difficult due to distortion carried in by strong interacting probe. We will discuss here results obtained at fragmentation of polarized deuterons with energies from 1 to 3.65 GeV/nucleon.

4. Praha-Spin-20054 GeV polarized deuteron beams is effective tool to study the deuteron spin structure in the region of deuteron core Single spin asymmetry (SSA) in the reaction with polarized deuterons can be studied without use of expensive polarized target with the large dilution factor. At fragmentation of high momentum deuterons one can test what is k - limit (rNN) for use of the nucleon model of the deuteron with disregard of nucleon substructure. As it was demonstrated by spin experiments at intermediate energies the spin effects are very sensitive to a structure of the short range NN-forces.

5. Praha-Spin-20055 A.P.Kobushkin, Proc. of the Int.Symp. “Dubna Deuteron-93”,p.71,Dubna,1993 GeV deuteron beams permit to extract information of deuteron structure at internal momentum up to k =1 GeV/c In 1982-83 Dubna (dp-breakup) and SLAC (ed-scattering) data showed that the nucleon mom. distribution in the deuteron deviates from IA-predictions based on standard DWF at k higher 0.25 GeV/c. The some models were successful at explanation this discrepancy but they encountered a difficulty at description of spin effects in the same region of internal momentum k/ 0.25 GeV/c.

6. Praha-Spin-20056 Deuteron breakup N(d,p)X and backward elastic scattering p(d,p)d are the reactions where a pole mechanism (ONE) should dominate and IA calculations seems to be well based. However, Saclay and Dubha measurements of the tensor analyzing power T20 and the polarization transfer ko revealed significant deviations from IA at k / 0.25 GeV/c.

7. Praha-Spin-20057 What is the reason of these discrepancies? Is DWF constructed with realistic NNP not correct at rNN [ 0.4 fm? Comparison of data with different probes at study the same subject can preserve from hasty conclusion. In JLAB d(e,de’) experiment t 20 was measured up to Q equivalent of k =0.65 GeV/c. At use of em-probe a rather good agreement with IA-predictions was observed. Q So dN-reactions give a chance to probe the deuteron at very high k ( k of 1 Gev/c is reached) but a number of mechanisms affecting on a behavior of observables must be taken into account at data interpretation (FSI,3NF, rescatt. and so on)

8. Praha-Spin-20058 Xc/X F - 1< 0.1 at E= 9 CeV Xc  X F at E >> M N Among hadrons probes a meson as mediator of NN-forces might bring a rich information on SR NN-forces. What sign can identify that the meson is produced at short rNN ? One can use a meson production in dN  hX reaction in the cumulative region, with mom. above available in NN-interaction. So the cumulative meson can be produced on strong correlated NN-pair only (in the d -core). The invariant variable x c is used for the cumulative reactions. It is defined by 4-mom. conservation: x c Pd+P N =Ph+Px, Pd is 4-mom. per nucleon. So x c is min. fragmenting mass (in Mn unit) to produce h. In dN  hX x c ranges up to 2. It is a some analog of x F for a case of NA -interaction. Pbeam = 4.5 GeV/c/nucl.

9. Praha-Spin-20059 More motivations for study the reaction dA  pX in the cumulative regime: 1)Identify the two alternative mechanisms of the cumulative regime a) based on Fermi motion: p is produced by high momentum nucleon NN->NN p, IA can be applied to calculate T 20 and the prediction can be compare with data; b) based on fragmentation 6q-component in the deuteron with hadronization of struck quark into the meson; no theoretical recipe to predict a behavior spin observables, but one can try to apply Collins or/and Sivers mechanisms to 6q fragmentation for data interpretation; 2) The large SSA were observed in pp  pX in beam fragmentation region at Pt> 0.5 GeV/c (FNAL data) and at x F > 0.5 (BNL data). One can wait a remarkable spin effects at d -fragmentation into high momentum pions with high Pt if similar mechanisms dominate at fragmentation of 3q- and 6q-system.

10. Praha-Spin-200510 E704, 200 GeV/c BNL, 22 GeV/c

11. Praha-Spin-200511 VBLHE experimental setup for study an inclusive meson production A(d, p )X sr, DW ( D p/p)=2.4x10 D p/p=2.2% Acceptance of the focusing spectrometer Momentum range 1.5 to 6 GeV/c Deuteron beam intensity Id = 2x10 d/spill Pzz(+) = 0.640 +- 0.033 +- 0.026 (sys ) Pzz(-) = -0.729 +- 0.024 +- 0.029 (sys) TOF-bases: Ls1-s5 =28m Ls2-s5 = 21m TOF-resolution s =0.2 ns TOF 1,2 - correlation -5 9

12. Praha-Spin-200512 Tensor analyzing power Ayy in A(d, p )X at Pd=9 GeV/c The sign of Ayy at x c >1 is negative at all Qp (contrary to DPM IA-prediction) Magnitude of Ayy increases with rise of Qp Ayy increases with rise of x c and reaches –0.4 at x c =1.5 (close to maximum of D-wave contrib. in DWF) Q and k –dependences in A(d, p )X is contrary to A(d,p)X

13. Praha-Spin-200513 Transverse momentum dependence of Ayy in A(d, p )X Ayy rises in magnitude at increase of Pt from 0.4 to 0.8 Ayy(Pt)-rise is linear at Qp of 135 and 180 mrad to find the limit of linear rise a study of higher Pt is desirable Pt-threshold effect near 0.5 GeV/c is known for An(pp  pX ) - Collins effect (PFF). Ayy(Pt)-effect is connected with D-state of 6q in the deuteron core. Sivers mechanism (PDF) can be applied to connect Ayy(Pt) with the orbital momentum (L=2) of 6q

14. Praha-Spin-200514 Ayy at fragmentation of 5 GeV/c tensor polarized deuterons At low Pt ( Qp ~0) Ayy shows weak x c -dependence varying from +0.1 to –0.1 when Pd ranges from 5 to 9 GeV/c The large tensor effects (D-wave) become apparent at x c > 1 with rise of Pt above ~0.4 GeV/c

15. Praha-Spin-200515 Vector analyzing power Ay in A(d, p )X Ay was measured with 9 GeV/c vector polarized d -beam at Qp = 180 mrad Ay changes monotonously from 0.1 to –0.1 at q p increase from 1.5 to 4 GeV/c (0.4 < x c < 1.7, 0.25 < Pt < 0.7) crossing zero near 3 GeV/c where x c = 1 Sign of Ay is similar for both sign of p due to isospin I=0 of the deuteron The significant growth of Ay-magnitude might be at Pt > 0.7 GeV/c as in p(p, p )X at high energies  p (+), o p (-) 180 mrad [ p (-) 135 mrad.

16. Praha-Spin-200516 Comparison Ay(dA  p X) and An(pp  pX) At high energies An(pp  p X) has opposite sign for p (+) and p (-) and show linear rise at Pt > 0.5 GeV/c (accordance with Collins effect) At moderate energies a behavior An(+) is the same but An(-) is small and Pt- indefinite If SSA mechanisms for 3q- and 6q- systems are the same than the similar tendencies have to be observed for Ay in dp  p X and pp  p X. One can note: Ay(+) tends to increase its magnitude at xc > 1; Ay(-) shows more flat form. “-”sign of AY(+) seems due to opposite spin directions for the deuteron and for nucleons in D-wave Lower Ay comparing with AN could be expected: SU(6) approach leads to Ay(d)<<An(p) due to diff. quark content : p(  ) [u(  )u(  )d(  )]  2u of 3q contribute to An[p  p (+)] d(  ) [u(  )u(  )d(  )][u(  )d(  )d(  )]  1u of 6q contributes to Ay[d  p (+)] ANL, pp 11GeV/c Dubna, dp 4.5GeV/c/n E704, pp 200GeV/c

17. Praha-Spin-200517 Conclusion The vector Ay and tensor Ayy analyzing powers were studied at 5 and 9 GeV/c d -fragmentation into cumulative pions. Those pions permit to probe the deuteron core structure up to rNN ~ 0.2 fm where two correlated nucleon can be studied as 6q-system Ayy at Qp =180 mrad shows a linear rise at increase Pt from 0.4 to 0.8 GeV/c – the threshold effect similar to An(pp  p X). Ayy(Pt)-effect is connected with the orbital momentum of 6q (D- state in deuteron core) - Sivers mechanism can be applied (PDF). Ay in dp  p X is small due to isospin I=0 (u,d-symmetry of pn-pair). Ay(Pt) can be explane just as An(Pt) in the framework of Collins effect Precision measurements at Pt > 0.7 GeV/c are desirable to find a limit of Ayy(Pt) linear rise and to clarify Pt-dependence of Ay at x c > 1. Study polarized deuteron fragmentation into cumulative kaons dp  K X could bring info on strangeness role in spin structure of short range NN-forces. 

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