11

SPIN EFFECTS AT FRAGMENTATION OF GEV SPIN EFFECTS AT FRAGMENTATION OF GEV POLARIZED DEUTERONS INTO PIONS WITH LARGE POLARIZED DEUTERONS INTO PIONS WITH LARGE

TRANSVERSE MOMENTUMTRANSVERSE MOMENTUM

L.S. Zolin for the SPHERA collaborationL.S. Zolin for the SPHERA collaboration ( ( Dubna – Nagoya - SofiaDubna – Nagoya - Sofia))

Prehistory and motivation: dppX & SSA in ppX

Study dAX in cumulative regime – tool to investigate . spin structure of 6q-configuration in the deuteronAnalyzing powers Ayy(xc,Pt) & Ay(xc,Pt)

Future plan: higher Pt, lower errors, study dAKX

Study the deuteron spin structure at short distances in Study the deuteron spin structure at short distances in dd-breakup -breakup A(d,p)A(d,p) and in backward elastic and in backward elastic H(d,p)dH(d,p)d with GEV polarized with GEV polarized dd-beams -beams

Several GeV pol. deuteron beams in Several GeV pol. deuteron beams in Saclay and Dubna permitted to examine Saclay and Dubna permitted to examine the predictions of IA-calculations with the predictions of IA-calculations with realistic NN-potentials for realistic NN-potentials for spinspin observables observables in A(d,p)X and H(d,p)d at in A(d,p)X and H(d,p)d at internal momenta internal momenta up to k=1 GeV/cup to k=1 GeV/c. . Study of Study of spin observables, Tspin observables, T2020 and and showed considerable showed considerable deviations from IAdeviations from IA--predictions at k> 0.25predictions at k> 0.25 GeV/c GeV/cA lot of different modelsA lot of different models were proposed were proposed to explain this phenomena. The some of to explain this phenomena. The some of them permit to improve description of them permit to improve description of the data. However those of them the data. However those of them ignoring QE- mechanism ignoring QE- mechanism cannot explaincannot explain satisfactory Tsatisfactory T2020 and and behavior behavior in all in all examined k-region up to 1 GeV/c.examined k-region up to 1 GeV/c.

22

2

2

2

2

2

w – uw sqrt(2)

U + W

T20= -

u – w –uw/sqrt(2)u + w

2

- Tensor analyzing power

- Polarization transfer

The The hadron probing experimentshadron probing experiments revealed revealed significant deviationssignificant deviations of spin observables of spin observables behavior from expected in accordance with behavior from expected in accordance with standard potentialstandard potential models models (for instance, T(for instance, T2020 does not change sign as was expected). does not change sign as was expected).

Hadron probesHadron probes permit to probe the deuteron permit to probe the deuteron structure at very high internal momentum structure at very high internal momentum (k=1. (k=1. GeV/cGeV/c is reached), however a is reached), however a number ofnumber of mechanismsmechanisms influencing on behavior of influencing on behavior of observables observables should be taken into should be taken into considerationconsideration ( ( -, NN -,N N –components in -, NN -,N N –components in DWF, P-wave admixture, FSI, 3NF DWF, P-wave admixture, FSI, 3NF and so on) and so on)

EM-probeEM-probe permitted to probe the deuteron permitted to probe the deuteron spin structure in non-destroying regime spin structure in non-destroying regime up to up to Q=6.5Q=6.5 fm ( fm (kkeqveqv= 0.65= 0.65 GeV/cGeV/c): JNAL –data for ): JNAL –data for ed-ed-elast.elast. Rather Rather good agreement with IA-good agreement with IA-predictionspredictions show that distortion-sources show that distortion-sources peculiar to hadron probe is not active in this peculiar to hadron probe is not active in this regime.regime.

It seems among strong interacting probes It seems among strong interacting probes nucleon one is too rough to study the nucleon one is too rough to study the deuteron core region. One can hope a deuteron core region. One can hope a meson meson probeprobe can permit to extract more detail can permit to extract more detail information.information. Q(fm )

-1

k (GeV/c)0

JLAB d(e,de’)

* * *

T20

h-probe

Hadron and EM probes at study of the deuteron spin structure

e-probe1

-1

44

Cumulative hadron production is tool to study of Cumulative hadron production is tool to study of nucleon clusters in nuclei (6q-component in the nucleon clusters in nuclei (6q-component in the

deuteron)deuteron)

Cumulative hadron hCumulative hadron hcc is defined as a high is defined as a high momentum hadron produced outside the kinematical momentum hadron produced outside the kinematical limit for free NN collisions. At deuteron fragmentation limit for free NN collisions. At deuteron fragmentation hhcc can be produced off correlated nucleon pair only (off can be produced off correlated nucleon pair only (off the deuteron core) which can be analyzed as 6q-the deuteron core) which can be analyzed as 6q-configuration.configuration.

To describe To describe hhcc- - spectra the spectra the cumulativecumulative variablevariable xxcc can be used defined by 4-mom. conservation at lower can be used defined by 4-mom. conservation at lower limit of Mx: xcPb + Pt = Phc+Px, limit of Mx: xcPb + Pt = Phc+Px, Pb(Pt) –Pb(Pt) – 4-mom. per beam 4-mom. per beam (target)(target) nucleon.nucleon. xxcc is min. fragmenting mass ( is min. fragmenting mass (in Min MNN unit unit) to ) to produceproduce h hcc. . For NN->h For NN->hccX xX xcc ranges to 1, for ranges to 1, for dp->hdp->hccXX xxcc-range from 1 to 2 corresponds to the cumulative -range from 1 to 2 corresponds to the cumulative regime.regime.

In In dp->dp->XX at at ppdd = 9 GeV/c = 9 GeV/c the pions with momentum the pions with momentum pp = 3.3 to 6.1 GeV/c = 3.3 to 6.1 GeV/c are produced in cumulative are produced in cumulative regime .regime .

Pbeam = 4.5 GeV/c/nucl.

Xc XF at E >> MN

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

To study in explicit form the To study in explicit form the spin effects due to spin effects due to meson- and meson- and quark-exchange mechanisms quark-exchange mechanisms atat deuteron deuteron fragmentation the reaction withfragmentation the reaction with cumulative mesoncumulative meson production production dA->hcX dA->hcX can be used .can be used .

55

Motivation for study the reaction dAMotivation for study the reaction dAX in the X in the cumulative regimecumulative regime

Two alternative mechanismsTwo alternative mechanisms can be considered to explain can be considered to explain hhcc - - production: 1) the production: 1) the firstfirst is based on is based on Fermi Fermi motionmotion , 2) , 2) the the secondsecond is based on consideration of is based on consideration of multi-quark multi-quark configurations configurations in nuclei ( in nuclei (6-quark6-quark component component in the in the deuterondeuteron).).

The numerical The numerical calculations forcalculations for T20 T20 in A(d, in A(d,)) were were performed in IA-approach (Fermi motion) supposing the performed in IA-approach (Fermi motion) supposing the direct production mechanism direct production mechanism DPMDPM:: NN->NNNN->NNpp . .

At At DPMDPM TT2020 in both A(d, in both A(d,) and A(d,p) should be) and A(d,p) should be similarsimilar ( (with extremum around k =0.25 GeV/cwith extremum around k =0.25 GeV/c) because it is defined ) because it is defined by asymmetry of nucleon momentum distribution in D-by asymmetry of nucleon momentum distribution in D-state (state (obviously, obviously, DPMDPM disregards disregards MECMEC in the deuteron in the deuteron).).

Test of validity of Test of validity of DPMDPM-hypothesis-hypothesis was one of motivations was one of motivations to study spin effects into study spin effects in A(d,A(d,)X with use of cumulative )X with use of cumulative regime to probe the deuteron core spin structure – it will regime to probe the deuteron core spin structure – it will be shown the test brought a be shown the test brought a negative answernegative answer..

66

E704, 200 GeV/cE704, 200 GeV/c

The The second second motivating fact: motivating fact: the large single spin the large single spin asymmetries asymmetries (SSA) A(SSA) ANN in in p(p())+p+p++X X in beam fragmentation in beam fragmentation region at Pt>0.5 GeV/c (FNAL) region at Pt>0.5 GeV/c (FNAL) and xand xFF >0.5 (BNL). >0.5 (BNL). Pt=0.5 is a typical threshold where Pt=0.5 is a typical threshold where quark degrees of freedom manifest quark degrees of freedom manifest themselvesthemselves..

Thus,one could wait a Thus,one could wait a remarkable remarkable spin effects at deuteron spin effects at deuteron fragmentation into high fragmentation into high momentum mesons with high Ptmomentum mesons with high Pt and/or and/or high xhigh xcc ( (if the sameif the same mechanismsmechanisms dominate at dominate at fragmentation of 3q- and 6q-systemfragmentation of 3q- and 6q-system).).

A detail study of analyzing powerA detail study of analyzing power AyAy and and AyyAyy at fragmentation of 5- at fragmentation of 5-10 GeV polarized deuterons was 10 GeV polarized deuterons was started started atat Dubna 10 GeV Dubna 10 GeV acceleratoraccelerator..

BNL , 22 GeV/c

77

Experimental Setup

sr,(p/p)=2.4x10 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: = 0.2 ns

TOF 1,2 - correlation

-5

9

Tensor analyzing power Ayy in Tensor analyzing power Ayy in A(d,A(d,)X)X

The The sign of Ayysign of Ayy in cumulative in cumulative region (xc>1) is region (xc>1) is negative negative at at all angles of pion emissionall angles of pion emission ((contrary to IA-predictions (DPM ) contrary to IA-predictions (DPM ) andand Ayy-behavior in Ayy-behavior in A(d,p)XA(d,p)X ) )

Magnitude of Magnitude of Ayy(Ayy() increases) increases with rise of emission anglewith rise of emission angle ((contrary to contrary to A(d,pA(d,p))).).

AyyAyy reaches a value of reaches a value of –0.4 –0.4 atat xc=1.5xc=1.5 where D/S-ratio in where D/S-ratio in DWF is close to its maximum.DWF is close to its maximum.

Some Some large D-state effectslarge D-state effects were were revealed at fragmentation of 9 revealed at fragmentation of 9 GeV tensor polarized deuterons GeV tensor polarized deuterons into cumulative pions.into cumulative pions.

A(d,p)X

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

As the pion transverse momentum As the pion transverse momentum increases from increases from Pt=0.4 to 0.8 GeV/cPt=0.4 to 0.8 GeV/c the the tensor analyzing powertensor analyzing power Ayy rises Ayy rises from from magnitude of near zero magnitude of near zero to –0.4.to –0.4.Starting point of Ayy(Pt)Starting point of Ayy(Pt) -rise-rise corresponds tocorresponds to Pt=0.4-0.5 GeV/c and Pt=0.4-0.5 GeV/c and xc=1xc=1 – the beginning of cumulative – the beginning of cumulative regime.regime.Ayy(Pt)-rise is linearAyy(Pt)-rise is linear at both angles of at both angles of pion emission, 135 and 180 mrad. pion emission, 135 and 180 mrad. At further study of Ayy it is desirable to At further study of Ayy it is desirable to measure Ayy at higher Pt to put limit of linear measure Ayy at higher Pt to put limit of linear rise.rise.Remind: the sameRemind: the same Pt-threshold Pt-threshold is reviled is reviled for Afor ANN(pp(ppX) and explanation can be X) and explanation can be done on base of Collins effect (PFF). But done on base of Collins effect (PFF). But here it appears for the tensor analyzing here it appears for the tensor analyzing power Ayy, it is connected to D-state of power Ayy, it is connected to D-state of 6q-system (L=2).6q-system (L=2).Origin of Ayy(Pt)-rise is another, Origin of Ayy(Pt)-rise is another, it dueit due toto 6q orbital momentum 6q orbital momentum most likely instead most likely instead of Collins effect.of Collins effect.

Vector analyzing power Ay in Vector analyzing power Ay in A(d,A(d,)X)X

AyAy was measured with 9 GeV was measured with 9 GeV vector polarized deuterons beam vector polarized deuterons beam at at =180 mrad=180 mrad..Ay Ay monotonously changes from monotonously changes from 0.1 to –0.10.1 to –0.1 with increase of with increase of qq from from 1.5 to 4 GeV/c1.5 to 4 GeV/c (0.4< xc <1.7) (0.4< xc <1.7) crossing crossing zero near xc=1.zero near xc=1.Sign-similaritySign-similarity forfor and and can be can be due to due to isospin I=0isospin I=0 of fragmenting of fragmenting system.system.

The significant growth of Ay might The significant growth of Ay might be observed, presumably, at be observed, presumably, at Pt>0.7 GeV/cPt>0.7 GeV/c as it takes place in as it takes place in p( p,p( p,)X)X at at high energies – high energies – to beto be measured.measured.

- pos. pions, 180 mrad. o - pos. pions, 180 mrad - neg. pions, 135 mrad.

1111

More about AyMore about Ay

At high energies (E704, 200 GeV/c) AN in ppgpX At high energies (E704, 200 GeV/c) AN in ppgpX has opposite sign for p and p and at Pt>0.5 a linear has opposite sign for p and p and at Pt>0.5 a linear approximation can be applied AN=a+bPt. approximation can be applied AN=a+bPt. Signs Signs of of AN(+) and AN(-) are AN(+) and AN(-) are in accordancein accordance with prediction with prediction of of Collins effectCollins effect (PFF). (PFF). At more moderate energies AN(+) demonstrate the At more moderate energies AN(+) demonstrate the same behavior but AN(-) is small and its Pt-same behavior but AN(-) is small and its Pt-dependence is indefinite (ANL, 11.75 GeV/c). If one dependence is indefinite (ANL, 11.75 GeV/c). If one supposes that mechanisms of SSA at supposes that mechanisms of SSA at fragmentation of 3q- and 6q-systems are the same fragmentation of 3q- and 6q-systems are the same the similar tendencies has to be observed for Ay in the similar tendencies has to be observed for Ay in dpdpX.X.Comparing ANL(ppgpX) and Dubna(dpgpX)Comparing ANL(ppgpX) and Dubna(dpgpX) data data one can note: 1) Ay(+) tends to increase its one can note: 1) Ay(+) tends to increase its negative value (in D-state nucleon spins are negative value (in D-state nucleon spins are opposite to deuteron spin) beyond the typical opposite to deuteron spin) beyond the typical threshold Pt=0.5 GeV/c. 2) Ay(-) demonstrates threshold Pt=0.5 GeV/c. 2) Ay(-) demonstrates more flat form. more flat form.

Evidently, Evidently, precision of dgpprecision of dgp data has to be i data has to be improved mproved and and Pt-intervalPt-interval should be increased up to should be increased up to 0.8-0.9 0.8-0.9 GeV/cGeV/c at least. It has to be done in the next runs. at least. It has to be done in the next runs.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(+)]d() [u()u()d()][u()d()d()] only 1u of 6q contributes to p n Ay[d(+)]

1212

Ayy at fragmentation of 5 GeV/c tensor polarized deuteronsAyy at fragmentation of 5 GeV/c tensor polarized deuterons

To clarify an energy dependence of spin effects in To clarify an energy dependence of spin effects in dpdpX the measurement of Ayy at Pd=5 GeV/c was X the measurement of Ayy at Pd=5 GeV/c was performed.performed.

In deuteron breakup In deuteron breakup dpdppX Ed-dependencepX Ed-dependence is is weak weak because Ayy is defined by nucleon momentum because Ayy is defined by nucleon momentum distribution in the deuteron (DWF).distribution in the deuteron (DWF).In In dpdpX Ed-dependenceX Ed-dependence demonstrate a demonstrate a threshold threshold behaviorbehavior in Pt-scale: Ayy shows a steep rice at in Pt-scale: Ayy shows a steep rice at Pt>0.5 GeV/c – deconfinement threshold (QDF Pt>0.5 GeV/c – deconfinement threshold (QDF manifestation). One can conclude: to study manifestation). One can conclude: to study effectively 6q-conf. spin structure effectively 6q-conf. spin structure one needsone needs polarized deuterons with Ed>6-8 GeVpolarized deuterons with Ed>6-8 GeV (Nuclotron (Nuclotron design upper limit is Ed=11 GeV).design upper limit is Ed=11 GeV).

About About Ayy-signAyy-signinin dpdppX dpX d( )>d( )>d( ) Ayy>0 ( ) Ayy>0 . in dp . in dpX dX d( )<d( )<d( ) Ayy<0( ) Ayy<0 . -form of nucleon density distribution in D-state . -form of nucleon density distribution in D-statePos. explanation in the model of multiquark config. Pos. explanation in the model of multiquark config. fragmentation: the cumul. meson is produced at fragmentation: the cumul. meson is produced at hadronization of quark-spectator which has a high hadronization of quark-spectator which has a high mom.(x>1) as result of mom. randomization in 6q. mom.(x>1) as result of mom. randomization in 6q. Preferable directionPreferable direction of randomization is of randomization is along spinalong spin axis: in orbit. mom. plane a constituent movement axis: in orbit. mom. plane a constituent movement is regulated by rotation. The result is is regulated by rotation. The result is Ayy(Ayy()<0 )<0

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ConclusionConclusion

The vector Ay and tensor Ayy analyzing powers were studied at fragmentation of 5 and The vector Ay and tensor Ayy analyzing powers were studied at fragmentation of 5 and 9 GeV/c polarized deuterons into high momentum pions (q9 GeV/c polarized deuterons into high momentum pions (q up to 5.3 GeV/c) produced up to 5.3 GeV/c) produced in cumulative regime (xc >1). Those pions permit to probe the deuteron core structure in cumulative regime (xc >1). Those pions permit to probe the deuteron core structure (strong correlated NN-pair can be analyzed as 6q-configuration).(strong correlated NN-pair can be analyzed as 6q-configuration).

At pion emission at non-zero angles the At pion emission at non-zero angles the Ayy demonstrates a steep rise beyond Pt =0.5Ayy demonstrates a steep rise beyond Pt =0.5 GeV/c – the same threshold as for SSA in p(GeV/c – the same threshold as for SSA in p()p)pX (beam fragm. region). X (beam fragm. region).

The sign of The sign of Ayy is negative both for Ayy is negative both for (+) and (+) and (-).(-). It can be explained by zero isospin of It can be explained by zero isospin of fragmenting pn(6q)-system and preferable randomization of constituent momentum in fragmenting pn(6q)-system and preferable randomization of constituent momentum in 6q (L=2) along spin axis.6q (L=2) along spin axis.

Ay(dAy(dx) is small and has similar sign for x) is small and has similar sign for (+) and (+) and (-) at Pt<0.6 GeV/c(-) at Pt<0.6 GeV/c due to quark due to quark content of pn-system (I=0). content of pn-system (I=0). At Pt>0.6 Ay(At Pt>0.6 Ay(+) shows tendency to rise+) shows tendency to rise – it should be – it should be checked in future measurements at Pt=0.7 to 0.9 GeV/c.checked in future measurements at Pt=0.7 to 0.9 GeV/c.

Measurements at this Pt -range is needed to put Measurements at this Pt -range is needed to put upper limit of Ayy(Pt) linear riseupper limit of Ayy(Pt) linear rise too. too.

These measurements were proposed to be done in the next runs with dThese measurements were proposed to be done in the next runs with dat Nuclotron. at Nuclotron. New field of investigation is New field of investigation is study of the reaction d(study of the reaction d())KX in cumulativeKX in cumulative regimeregime to to extract info of strangeness contribution in spin of strong correlated NN-pair (6q-extract info of strangeness contribution in spin of strong correlated NN-pair (6q-system).system).

To realize future program the To realize future program the next parameter of polarized deuteron beamnext parameter of polarized deuteron beam extracted extracted from Nuclotron are from Nuclotron are requiredrequired: Ed up to : Ed up to 11 GeV11 GeV, Id >, Id >10^9d/spill10^9d/spill ( (PionPion program), Id> program), Id> 10^10d/spill (Kaon10^10d/spill (Kaon program). These numbers are within the limits of Nuclotron design program). These numbers are within the limits of Nuclotron design parameters. parameters.