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ANALIZING POWER STUDY IN THE REACTIONS INDUCED BY SEVERAL GEV

POLARIZED DEUTERONS

L.S. Zolin for the SPHERA Collaboration

Joint Institute for Nuclear research (Dubna)

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Outline• Introduction• The lesson of spin effect studies at E < 1 GeV• Deuteron breakup, d(p,p)d-elastic and problems at

explanation of NMD(k), T20, ko - data at k > 0.25 GeV/c

• GeV polarized deuteron beams as tool to study a spin structure of short range NN-forces

• Study dAX in cumulative regime as means to investigate the deuteron core spin structure

• Analyzing powers Ayy(xc,Pt) and Ay(xc,Pt) in dAX • SSA in dAX and pAX ,• Azz(x) of HERMES (b1-data) & Ayy(x) of Dubna• Conclusion

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NN-forces and few nucleon systems

• the NN-forces are described by means of phenomenological NN-potentials (NNP) constructed to fit NN-scattering data at low and intermediate energies.

• A range of their applicability is tested by comparison of NNP-based calculations with behavior of observables in NA-reactions. The most powerful NNP-test should content a full set of spin observables.

• In E < 1 GeV region a high activity with study of spin observables had place in a number of laboratories ( IUCF, TRIUMF, KVI, RIKEN, RCNP); the main purpose of the latest studies with light nuclei is the search for evidence of a three nucleon forces.

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How much addition of 3NFs can improve an accordance of calculations and exp. data?

K.Sekiguchi et al., PR C70,014001(2004)

p + d elast. at 135 MeV/nucleon

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2NF calculations-data discrepancies are clearly seen in CS-minimum and at larger c.m. angles.

They become larger as an energy is increased

3NFs(2p exchange) improve the description of CS and some spin observables, but not always

3NFs are needed but their spin dependent part has some defects

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Completeness of data set of spin observables riched in the lastpd-scattering experiments can be illustrated by the IUCF-data

(B.v.Przewoski et al. nucl-ex/0411011)

• Ay for p & d, Aji and 10 of 12 spin correlation coefficients in p+d –elastic

• 2N-force Faddeev calculations with CD-Bonn & AV18 NNP’s within/without 3NFs

• IUCF-group conclusion is less optimistic comparing with the pronounced in other experiments:

• 3NFs are not successful in explanation of discrepancy between 2N-calculations and data at large angles

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Copious data at intermediate energies show that CS and the spin observables can not be satisfactory described (the discrepancies ~ 20-30%) even by means of most sophisticated suggested 2NF and 3NF potentials.

The discrepancies are most sizeable at scattering angles where the transverse momentum Pt is high and close to threshold (~ 0.4 GeV/c) where quark degrees of freedom (QDF) begin to manifest themselves (rNN<0.6 fm).

Several attempts were made to construct SR NNP in the framework of the quark cluster model (QCM). However the test of QCM approaches showed that the nonrelativistic quark models (successful in describing the static properties of single hadrons) fails to reproduce the SR part of the NN interaction quantitatively [ M.Lacombe et al., PR C65,034004 (2002) , the analysis - up to 350 MeV.].

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The lesson of spin effect study at intermediate energies (<1 GeV)

is to find theoretical approach of correct treatment of relativistic effects and QDF when one probes the

NF’s core.

A warning point is Pt>= 0.40.5 GeV/c.

At higher energies (>1GeV) the problem will gain strength.

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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 :

a) in DIS experiments with light nuclei, available rNN-scale is limited by low cross sections of (e,l)N-reactions ;

b) in reactions of nuclei fragmentation with use h-probes (NA,A), 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.

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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 internal momentum limit (rNN) for use of the nucleon model of the deuteron at disregard of nucleon substructure.

As it was demonstrated by spin experiments at intermediate energiesthe spin effects are very sensitive to structure of the short rangeNN-forces.

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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-scatt.) 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.

Some of the 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.

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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.

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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 could preserve from such a prompt conclusion. In JLAB d(e,de’) experiment t20 was measured up to Q equivalent of k=0.65 GeV/c. Rather good agreement with IA-predictions was observed at use of em-probe.

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 ona behavior of observables must be taken into account at data interpretation (FSI,3NF, rescatt.and so on)

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Xc/XF - 1< 0.1 at E= 9 CeV

Xc XF at E >> MN

Among hadrons probes a meson as mediator of NN-forces might bring a valuable information on SR NN-forces. What sign can identify that the meson is produced at short rNN ?

One can use a meson production in dNhX reaction in the cumulative region, with meson momentum above available in NN-interaction. So the cumulative meson can be produced on strong correlated NN-pair only (i.e. on the d-core).

The invariant variable xc is used for the cumulative reactions. It is defined by 4-mom. conservation: xcPd+PN=Ph+Px, Pd is 4-mom. per nucleon. So xc is min. fragmenting mass (in Mn unit) to produce h. In dNhX xc ranges up to 2. It is a some analog of xF for a case of NA-interaction.

Pbeam = 4.5 GeV/c/nucl.

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More motivations for study the reaction dAX in the cumulative regime:

1) Identify the two alternative mechanisms of the cumulative regime

a) based on Fermi motion: is produced by high momentum nucleon

NN->NN, IA can be applied to calculate T20 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 ppX in beam fragmentation region at Pt> 0.5 GeV/c (FNAL data) and at xF > 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.

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E704, 200 GeV/c BNL , 22

GeV/c

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VBLHE experimental setup for study an inclusive meson production A(d,p)X

sr,W(p/p)=2.4x10 p/p=2.2%

Acceptance of the focusing spectrometer

Momentum range 1.5 to 6 GeV/cDeuteron 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 =0.2 ns

TOF 1,2 - correlation

-5

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Tensor analyzing power Ayy in A(d,)X at Pd=9 GeV/c

The sign of Ayy at xc >1 is negative at all (contrary to DPM IA-prediction)

Magnitude of Ayy increases with rise of Ayy increases with rise of xc and reaches –0.4 at xc=1.5 (close to maximum of D-wave contrib. in DWF)

and k –dependences in A(d,)X is contrary to A(d,p)X

))(Ap21

)(Ap23

1)(()( yyzzyz0

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Transverse momentum dependence of Ayy in A(d,)X

Ayy rises in magnitude at increase of Pt from 0.4 to 0.8Ayy(Pt)-rise is ~linear at 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(ppX), it can beexplained by Collins effect (PFF).

Ayy(Pt)-effect due to D-state of 6q in the deuteron core. Sivers mechanism (PDF) can be applied to connect Ayy(Pt) with the orbital momentum of 6q (L=2)

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Ayy at fragmentation of 5 GeV/c tensor polarized deuterons

At low Pt (~0) Ayy shows weak xc-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 xc > 1with rise of Pt above ~0.4 GeV/c

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Vector analyzing power Ay in A(d,)X

Ay was measured with 9 GeV/c vectorpolarized d-beam at = 180 mrad

Ay changes monotonously from 0.1 to –0.1 at q increase from 1.5 to 4 GeV/c (0.4 < xc < 1.7, 0.25 < Pt < 0.7) crossingzero near 3 GeV/c where xc = 1

Sign of Ay is similar for both sign of due to isospin I=0 of the deuteron

The significant growth of Ay-magnitudemight be at Pt > 0.7 GeV/c as inp(p,)X at high energies- desirable to measure.

(+) , o (-) 180 mrad

(-) 135 mrad.

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b1

HERMES hep-ex/0506018, d (e.e’)X - DIS

Dubna, A( d, )X

Different x-regions in the deuteron are probed in these two experiments:x < 0.5 at HERMESx = 0.5 to 1.6 at DubnaSo far, x > 0.9 is not available in ed-

DIS

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ConclusionThe 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 shows a linear rise at increase Pt from 0.4 to 0.8 GeV/c – the threshold effect similar to AN(Pt) in ppX.Ayy(Pt)-effect is connected with the orbital momentum of 6q (D-state in deuteron core) - Sivers mechanism can be applied (PDF).Ay in dpX 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

About a future plan:a) 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 xc > 1.b) Study polarized deuteron fragmentation into cumulative kaonsdpKX could bring info on strangeness role in spin structure of 6q ( Id > 10 is required)

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BACK UP 1

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Ayy at fragmentation of 5 GeV/c tensor polarized deuterons

• Ayy at Pd=5 GeV/c was measured to clarify an energy dependence in A(d,p)X (black points)

• • A(d,p)X against A(d,p)X

Ed-dependence of Ayy -- is weak in d-breakup A(d,p)X (Ayy is defined by nucleon momentum distribution in the deuteron) -- is remarkable in A(d,p)X (contradicts with NN->NNp production mechanism)

• Ayy-sign: in A(d,p)X ds( ) > ds( ) Ayy>0 . in A(d,p)X ds( ) < ds( ) Ayy<0 -form of nucleon density distribution in D-state

Multiquark fragmentation model: the cumul. meson is produced at hadronization of quark-spectator which has a high mom.(x>1) as result of momentum randomization in 6q. Preferable direction of randomization is along spin axis: in orbit. mom. plane a constituent movement is regulated by rotation. The result is Ayy(p) < 0

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• l-probes are point like and weak-disturbing: allow one to operate with an individual nucleon in nucleus volume; their disadvantages are low cross sections

• h-probe is the strong force probe, highly effective (large cross section) but rough: its size ~ NF radius; at probing the nucleus structure at SR one needs to take into account an inner structure of h-probe as well.

• Nevertheless, the prevailing bulk of nuclear reaction data including spin physics data is obtained with use of h-pobe (,N)

NN-forces, which define the structure and features of nuclei, can be studied with use of different probes: lA-, eA-, hA-reactions.