Spin Effects Correlated with 6q-Component in the Deuteron

Spin-2006_ Kyoto_Zolin L. 1

Spin Effects Correlated with 6q-Component in the Deuteron

L.S. Zolin, Yu.K. Pilipenko

Joint Institute for Nuclear research (Dubna)

zolin


Outline

• Introduction• SR NN-correlations in nuclei, Fermi- motion or MQC ?• Evidence for MQC in nuclei in IE and HE spin

expts. • dAYπX in cumulative regime as tool to study the

deuteron core spin structure • SSA in dAYπX and ppYπX • Azz(x) of HERMES (b1-data) vs Ayy(x) of Dubna

• Ayy(Pt) in dAYπX and orbital mom. of 6q in D-state

• Conclusion


Structure of nuclei at short internucleonic distances is connected with

phenomenon of existing of short range nucleon correlations which

manifests themselves as few nucleon clusters. When wave functions of nucleons are overlapped ( rNN <

0.7 fm) they can be treated as multiquark configurations MQC. ( In case of deuteron the deuteron core can be considered as the 6q-system).

MQC existence is confirmed by EMC-effect. They are responsible for

such phenomena as subthreshold meson production at E < 1 GeV

and production of high momentum cumulative secondaries in NA-,AA- collisions at high energies. An alternative explanation in frame work of nucleon meson

models of NN-forces is by means of Fermi motion in nuclei.

Experiments with spin observables can help to resolve which of

two approaches is more founded.


Spin observables were studied most intensively at intermediate energies

with detail comparison of data and calculations at use of 2NF’s and 3NF’s.

Analysis of intermediate energy data made it is clear that

1) necessary to find theoretical approach of correct treatment of

relativistic effects and QDF when one probes the NF’s core,

2) the spin effects are very sensitive to structure of short range NF’s.

[ M.Lacombe et al., PR C65,034004 (2002) , the analysis - up to 350 MeV.].

Data at higher energies confirms the same: SR NNF’s cannot be

understood without detail knowledge of nucleon substructure and

structure of SR NN-correlations in nuclei.


Information on SR NN-correlations in nuclei can be extracted :

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

b) in reactions of nuclei fragmentation with use h-probes (NA,pA), very low rNN are available (up to 0.2 fm) but interpretation is difficult due to distortion carried in by strong interacting probe.

Let to discuss the results obtained at fragmentation of polarized deuterons with energies from 1 to 3.65 GeV/n , which permit to study the deuteron spin structure up to internal momenta k=1 GeV/c .

HE-region : DIS experiments and nucleus fragmentation


Dubna and Saclay measurements of the tensor analyzing power T20 and the polarization transfer ko at deuteron breakup revealed significant deviations from IA calculations at k > 0.25 GeV/c.

These discrepancies raise a question: is DWF constructed with realistic NNP not correct at rNN ≤ 0.4÷0.5 fm?


D.Abbott et al., nucl-ex/0001006

It seems an answer was provided inthe JLAB d(e,de’)- experiment whereT20 was measured up to Q equivalentof k=0.65 GeV/c and rather good agreement with IA-predictions wasobserved (and with pQCD-calcul’sas well) - known DWF’s work well up to k~0.6 GeV/c.

Thus, the deuteron breakup N(d,p)Xpermits to probe DWF at very high k(1 Gev/c is reached) but too manymechanisms affect on behavior ofspin observables (FSI, 3NF, isobarexcitation, rescattering and so on).

Another reaction with h-probe which permits to study the deuteron spin structure at very small rNN is polarized deuteron fragmentation into high momentum pions: pol.d + N→π+X.

em - probes vs h - probes


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

Xc →XF at E >> MN

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

One must use a meson production reaction dN→πX in the cumulative regime when the 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: xc·Pd+PN=Ph+Px ( Pd is 4-mom. per nucleon). xc is min. fragmenting mass (in Mn unit) to produce h . In dN→hX xc ranges up to 2. xc is some analog of xF for a case of NA- interaction

Pbeam = 4.5 GeV/c/nucl.


Motivation to study spin observables in the reaction

dA YπX in the cumulative regime

1) Discriminate between two alternatives for mechanisms of cumulative reactions:

a) based on Fermi motion: NN→NNπ, IA can be applied to calculate T20,

the prediction can be compared with data;

b) based on fragmentation 6q-component in the deuteron with hadronization of struck quark into the meson:

d→6q→(q→π )+X ; 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→πX in beam fragmentation

region at Pt > 0.5 GeV/c (FNAL) and at xF > 0.5 (BNL).

Thus, one can expect a remarkable spin effects at d-fragmentation

into high momentum pions with high Pt if similar mechanisms act

at fragmentation of 3q- and 6q-system.

FNAL (E704), 200 GeV/c BNL, 22 GeV/c


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

sr,(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: 28m & 21mTOF-resolution =0.2 ns

TOF 1,2 - correlation

-5

9


Tensor analyzing power Ayy in dA→π(Θ)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 Θ and with rise of xc Ayy reaches –0.4 at xc=1.5

Θ- and k -dependences in A(d,π)X is contrary to A(d,p)X


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

Ayy rises in magnitude at increase of Pt from 0.4 to 0.8 (~linearly, where is limit of such a rise?)Threshold effect is seen for SSA in pp→πX, it is due to x-dependence of quark contribution into nucleon spin.

In dp→πX Ayy(Pt) is tensor effect due to D-state of 6q in the deuteron core (seen at xc > 1 only). In frame of Sivers approach (PDF) Ayy(Pt)-dependence is determined,evidently, by the orbital momentum of 6q (L=2) .


Ayy at fragmentation of 5 GeV/c tensor polarized deuterons

At low Pt (Θ~0) Ayy shows weak xc-dependence varying from +0.1 to –0.1 when Pd ranges from 5 to 9 GeV/c


Vector analyzing power Ay in A(d,π)X at Pd=9 GeV/c

Ay was measured with vector polarized d-beam at Θπ = 180 mrad

Ay changes monotonously from 0.1 to –0.1 at increase of qπ from1.5 to 4 GeV/c (0.4 < xc < 1.7, 0.25 < Pt < 0.7) crossing zero near 3 GeV/c where xc = 1.

Sign of Ay is similar for π+ and π- .

Both features, sign similarity and lowvector analyzing power (comparing withAn in pp→πX), due to isospin I=0 of thedeuteron (quark content is 3u+3d)

.

(+) , o (-) 180 mrad

(-) 135 mrad.


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

GeV deuteron fragmentation vs DIS - deuteron


For a possible explanation of striking Pt-dependence of Ayy in dA -> πX one can follow C.Boros and Liang Zuo-Tang

approach for explanation of SSA in inclusive high energy hadron-hadron

collision processes [ hep-ph/0001330 ]. They constructed the non-perturbative model which explicitly

takes the orbital motion of the valence quarks into account.


Estimation of cumulative pion Ptat breakup of 6q-cluster with L=2

projection on transverse plain

pq

D-beam

Pzz ≠ 0

D-stateL=2

Sdalong z-axis

pq ~ Pt(π)

Absolute value of orbital moment at L=2

Labs = sqrt(L·(L+1)) ~ 500 fm· MeV/cOrbital momentum porb ~ Labs / rNNXc = 1.5 corresponds to rNN ~ 0.4 fm

and porb ~ 1.2 GeV/c. Thus, xy- projection of struck quark can rang up to pq ~ 1.2

GeV/c.At its hadronization into pion the

transverce pion momentum Pt can range in the

same limits.

At cumulative pion emission angle of 160mrad

Ayy ramped to -0.4 with Pt rise up to 0.8 GeV/c.

Above estimations show that one can expect

further rise of Ayy at higher Xc or saturation effect can be revealed as

well.- That is a matter of the next

experiment.


Conclusion

The vector Ay and tensor Ayy analyzing powers were studied at 5 and 9 GeV/c at d-fragmentation into cumulative pions which permit to probe the deuteron core structure up to rNN ~ 0.2 fm where two correlated nucleon can be studied as 6q-system.

Ay in dA->πX is small due to isospin I=0 (u,d -symmetry of pn-pair).

Ayy shows a linear rise at increase Pt from 0.4 to 0.8 GeV/c – the threshold effect similar to AN(Pt) in pp->πX Ayy(Pt)-effect can be connected with orbital momentum of 6q in D-state. Precision measurements at Pt > 0.7 GeV/c are desirable to find a limit of Ayy(Pt) rise and to clarify Pt-dependence of Ay at xc >1.


Our sincere thanks to Organizing Committee of SPIN 2006 for invitation and support to take part in the Symposium.

It is great pleasure for both of us to express our gratitude to collaborators from Nagoya University conducted by Prof. N.

Horikawafor common efforts to perform successful experiments at

Dubna polarized deuteron faсility.


BACK UP 1


We can shortly review data with polarized deuterons at E<1 GeV and E>1 GeV to conclude where

successful andwhere not explanation of observables behavior at

disregardof quark degrees of freedom (QDF) in nuclei.

At intermediate energies (E < 1 GeV) study in a number of

laboratories (IUCF,KVI,RIKEN,RCNP) was concentrated on

search of evidence of a three nucleon forces (3NF) because

discrepancies of 2NF calculations and data take place in

cross section minimum at large c.m. angles.


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

K.Sekiguchi et al., PR 0,014001(2004)p + d elast. at 135 MeV/nucleon

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

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

IUCF-group conclusion: 3NFs are not successful in explanation of discrepancy between 2N-calculations and data at large angles(B.v.Przewoski et al. nucl-ex/0411011)


From Proc. of the Intern. Symp.“Dubna Deuteron-93”,p.71,

Dubna,1993

The first evidence of impotence of the deuteron nucleon model to explane data of deuteron induced reactions in GeV-region

In 1982-83 Dubna (dp-breakup) and SLAC (ed-scatt.) data showed that the nucleon mom. distribution in the deuteron Nd(k) deviates from IA-predictions based on standard DWF at k 0.25 GeV/c. Similar problem was reviled with p(d,p)d

It was as a surprise because the 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. Spin observables shown increasing deviations at the same k 0.25 GeV/c.


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.


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


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

’ ’

Documents

Spin Effects Correlated with 6q-Component in the Deuteron