Liang, Z
Liu, C
Hyperon polarization in $\nu_{\mu}$ charged current interaction at the NOMAD energies
Phys. Rev. D
057302
66
We show that, in $\nu_\mu N\to \mu^-\Lambda X$ at the NOMAD energies, it is impossible to separate the products of the fragmentation of the struck quark from those of the nucleon remnant. The latter has a large contribution even in the current fragmentation region and has to be taken into account in calculating $\Lambda$ polarization using different pictures. Based on this, we make a rough estimation for the longitudinal $\Lambda$ polarization in $\nu_{\mu} N \to \mu^- \Lambda X$ at the NOMAD energies. A comparison with the data is given and predictions for $\nu_\mu N\to\mu^-\Sigma^+X$ are presented.
eng
2002
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0204323;
http://cds.cern.ch/record/549388/files/0204323.pdf;
http://cds.cern.ch/record/549388/files/0204323.ps.gz;
Imported from Invenio.
Liang, Z
Xu, Q
Hyperon polarization in e^-p --> e^-HK with polarized electron beams
Phys. Rev. D
113012
65
We apply the picture proposed in a recent Letter for transverse hyperon polarization in unpolarized hadron-hadron collisions to the exclusive process e^-p --> e^-HK such as e^-p-->e^-\Lambda K^+, e^-p --> e^-\Sigma^+ K^0, or e^-p--> e^-\Sigma^0 K^+, or the similar process e^-p\to e^-n\pi^+ with longitudinally polarized electron beams. We present the predictions for the longitudinal polarizations of the hyperons or neutron in these reactions, which can be used as further tests of the picture.
eng
2002
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0204322;
http://cds.cern.ch/record/549387/files/0204322.pdf;
http://cds.cern.ch/record/549387/files/0204322.ps.gz;
Imported from Invenio.
Popov, B A
Measurement of the $\Lambda$ hyperon polarization in $\nu_{\mu}$ charged current interactions in the NOMAD experiment
Nucl. Phys. A
73-80
692
The Lambda hyperon polarization in nu /sub mu / charged current interactions has been measured in the NOMAD experiment. The event sample (8087 reconstructed Lambda 's) is more than an order of magnitude larger than that of previous bubble chamber experiments, while the quality of the event reconstruction is comparable. We observe a negative polarization along the W-boson direction which is enhanced in the target fragmentation region: P/sub x/(x/sub F/<0) =-0.21+or-0.04(stat)+or-0.02(sys). In the current fragmentation region we find P/sub x/(x/sub F/>0)=-0.09+or-0.06(stat)+or-0.03(sys). These results provide a test of different models describing the nucleon spin composition and the spin transfer mechanisms. We also observe a significant transverse polarization (in the direction orthogonal to the Lambda production plane) for the first time in a neutrino experiment: P/sub y/=-0.22+or-0.03(stat)+or-0.01(sys). The dependence of the absolute value of P/sub y/ on the Lambda transverse momentum with respect to the hadronic jet direction is in qualitative agreement with the results from unpolarized hadron-hadron experiments. The dependence of the Lambda polarization on the type of target nucleon in nu /sub mu / scattering has been also studied. (11 refs).
eng
2001
Imported from Invenio.
Liu Chun Xiu
Liang Zuo Tang
Spin transfer in high-energy hadronization processes and polarization of hyperon in the lepton-induced reactions
High Energy Phys. Nucl. Phys. (Beijing)
476-86
25
We show that measuring the polarization of the hyperon in the lepton induced reactions is an ideal way to study the spin transfer in high- energy hadronization processes. After a brief summary of the polarization of the initial quark or antiquark in these reactions, we give the calculation method of the polarization of the hyperon. As an example, we calculate polarizations of different hyperons in e/sup + /e/sup -/ annihilation at LEP energies and compare these results with the available data. The results show that measurements of such polarizations should provide important information about the question of which picture of spin structure of baryon is more suitable in describing the spin effects in the high-energy fragmentation processes. (17 refs).
chi
2001
Imported from Invenio.
Liu, C
Xu, Q
Liang, Z
Hyperon polarization in semi-inclusive deeply inelastic lepton-nucleon scattering at high energy
Phys. Rev. D
073004
64
We calculate the polarizations for different octet hyperons produced in the current fragmentation regions of the deeply inelastic lepton-nucleon scatterings $\mu^-N \to \mu^- HX$ and $\nu_{\mu} N \to \mu^- HX$ at high energy using different models for spin transfer in fragmentation processes. The results show that measurements of those hyperon polarizations should provide useful information to distinguish between different models in particular the SU(6) and the DIS pictures used frequently in the literature. We found, in particular, that measuring the polarization of $\Sigma^+$ produced in these processes can give a better test to the validity of the different spin transfer models.
eng
2001
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0106184;
http://cds.cern.ch/record/504920/files/0106184.pdf;
http://cds.cern.ch/record/504920/files/0106184.ps.gz;
Imported from Invenio.
Maggiora, M
Balestra, F
Bedfer, Y
Bertini, R
Bland, L C
Brochard, F
Bussa, M P
Chalyshev, V
Choi, S
Debowski, M
Dzemidzic, M
Faivre, Jean-Claude
Falomkin, I V
Fava, L
Ferrero, L
Foryciarz, J
Frolov, V
Fröhlich, I
Garfagnini, R
Gill, D
Grasso, A
Heinz, S
Ivanov, V V
Jacobs, W W
Kühn, W
Maggiora, A
Manara, A
Panzieri, D
Pfaff, H W
Piragino, G
Pontecorvo, G B
Popov, A
Ritman, J
Salabura, P
Tosello, F
Vigdor, S E
Zosi, G
Spin observables in hyperon production
Nucl. Phys. A
477c-480c
663-664
The first exclusive measurements of the spin transfer parameter D sub N sub N in the reaction p-vectorp->pK sup +LAMBDA-vector has been performed at Saturne with the polarized beam and with the DISTO spectrometer. The results suggest an OBE mechanism dominated by kaon exchange.
eng
2000
Imported from Invenio.
Belostotskii, S L
Longitudinal spin transfer to the Lambda hyperon in leptoproduction
http://www-hermes.desy.de/notes/pub/doc-public-index.html#2001;
Imported from Invenio.
Chiang Huan Ching
Lambda hyperon production mechanisms and longitudinal spin transfer at HERMES
The internal spin structure of the Lambda is of special importance for the understanding of the spin structure of hadrons in general. The comparison between the nucleon and Lambda allows for a test of the relevant flavour-symmetry breaking effects. Using nonperturbatively O(a) improved Wilson fermions in the quenched approximation we have calculated the first moments of the unpolarised, longitudinally polarised and transversity quark distribution functions in the Lambda. The results indicate that flavour symmetry breaking has little effect on the internal spin structure, in accordance with model based expectations.
eng
2002
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-lat&id=0208017;
http://cds.cern.ch/record/576187/files/0208017.pdf;
http://cds.cern.ch/record/576187/files/0208017.ps.gz;
Imported from Invenio.
Göckeler, M
Horsley, R
Pleiter, D
Rakow, P E L
Schäfer, S
Schäfer, A
Schierholz, G
The spin structure of the Lambda hyperon in quenched lattice QCD
Nucl. Phys. B, Proc. Suppl.
305-307
106
It has been suggested to use the production of Lambda hyperons for investigating the nucleon spin structure. The viability of this idea depends crucially on the spin structure of the Lambda. Using nonperturbatively O(a) improved Wilson fermions in the quenched approximation we have studied matrix elements of two-quark operators in the Lambda. We present results for the axial vector current, which give us the contributions of the u, d, and s quarks to the Lambda spin.
eng
2002
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-lat&id=0110057;
http://cds.cern.ch/record/522893/files/0110057.pdf;
http://cds.cern.ch/record/522893/files/0110057.ps.gz;
Imported from Invenio.
Belostotskii, S L
Grebenyuk, O
Lambda polarization measured at HERMES and Lambda spin structure
http://www-hermes.desy.de/notes/pub/doc-public-index.html#1999;
Imported from Invenio.
Yang Jian Jun
Up and Down Quark Contributions to Spin Content of Lambda from Fragmentation
Phys. Lett. B
57-64
512
We check the $u$ and $d$ quark contributions to the spin content of the $\Lambda$ by means of the $q\to\Lambda$ fragmentation and find that the $u$ and $d$ quarks of the $\Lambda$ are likely positively polarized. The parton distributions in the $\Lambda$ are given by a successful statistical model which can reproduce and correlate a vast body of polarized and unpolarized structure function and parton distribution data of the nucleon. With the Gribov-Lipatov relation between the quark distributions and fragmentation functions, the longitudinal spin transfer for the $\Lambda$ production in the polarized charged lepton deep inelastic scattering (DIS) process and the $\Lambda$-polarization in the neutrino (antineutrino) DIS process are predicted. The available experimental data suggests that the $u$ and $d$ quark contributions to the spin of the $\Lambda$ are positive. In addition, our results provide a collateral evidence for the SU(3) symmetry breaking in hyperon semileptonic decays of the octet baryons, which is very important for a deeper understanding of the proton 'spin crisis'.
eng
2001
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0107222;
http://cds.cern.ch/record/510152/files/0107222.pdf;
http://cds.cern.ch/record/510152/files/0107222.ps.gz;
Imported from Invenio.
http://www-hermes.desy.de/notes/pub/doc-public-index.html#2001;
Imported from Invenio.
Schnell, G
Longitudinal polarization of the Lambda in deep inelastic scattering of polarized positrons from nucleons
http://www-hermes.desy.de/notes/pub/doc-public-index.html#1999;
Imported from Invenio.
Raue, Brian A
Ratio of $\sigma_L / \sigma_T$ for $p(e,e'K^+)\Lambda$ Extracted from Polarization Transfer
Phys.Rev.C
065209
71
The ratio of longitudinal to transverse structure functions, $\sigma_L/\sigma_T$, has been extracted from recent beam-recoil transferred polarization data for the $p(\vec e,e'K^+)\vec\Lambda$ reaction. Results have been obtained for $W$=1.69, 1.84, and 2.03 GeV at an average $Q^2$ of 0.69 GeV$^2$. Our results indicate a ratio approaching zero. This is in contradiction to previously published results using a Rosenbluth separation. A similar difference between Rosenbluth and recoil polarization results has been observed in the measurement of the ratio of electric to magnetic form factors of the proton, $\mu_pG_E/G_M$.
eng
2004
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=nucl-ex&id=0402024;
http://cds.cern.ch/record/720305/files/0402024.pdf;
Imported from Invenio.
Brüll, A
Transverse polarization of Lambda and Antilambda hyperons in quasi-real photon nucleon scattering
Two related issues are discussed, which might be easily explored by present and future COMPASS experiments. The first one deals with the new world of transversity, the fundamental polarized parton distribution so far totally unknown. The second issue concerns Lambda production in polarized semi-inclusive processes, with a measurement of the Lambda polarization, which might give novel information on distribution and fragmentation properties of polarized partons. In case of transverse polarization the detection of Lambda's gives access to a new way of measuring transversities. Also the interesting case of Lambda polarization in unpolarized processes is discussed.
eng
CERN
2004
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0302008;
http://documents.cern.ch/cgi-bin/setlink?base=yellowarticle&categ=2004-011&id=p130;
http://cds.cern.ch/record/603715/files/0302008.pdf;
http://cds.cern.ch/record/603715/files/0302008.ps.gz;
http://cds.cern.ch/record/603715/files/p130.pdf;
Imported from Invenio.
Carman, D S
First Measurement of Transferred Polarization in the Exclusive e p --> e' K+ Lambda Reaction
Phys. Rev. Lett.
131804
90
The first measurements of the transferred polarization for the exclusive ep --> e'K+ Lambda reaction have been performed in Hall B at the Thomas Jefferson National Accelerator Facility using the CLAS spectrometer. A 2.567 GeV electron beam was used to measure the hyperon polarization over a range of Q2 from 0.3 to 1.5 (GeV/c)2, W from 1.6 to 2.15 GeV, and over the full center-of-mass angular range of the K+ meson. Comparison with predictions of hadrodynamic models indicates strong sensitivity to the underlying resonance contributions. A non-relativistic quark model interpretation of our data suggests that the s-sbar quark pair is produced with spins predominantly anti-aligned. Implications for the validity of the widely used 3P0 quark-pair creation operator are discussed.
eng
2003
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ex&id=0212014;
Imported from Invenio.
Kotzinian, A M
$\Lambda$ polarization in the target fragmentation region of SIDIS
AIP Conf. Proc.
272-276
588
The Lambda and Lambda-bar polarizations in muon neutrino charged current interactions have been measured in the NOMAD experiment. The event sample (8087 reconstructed Lambda's and 649 Lambda-bar's) is more than an order of magnitude larger than that of previous bubble chamber experiments, while the quality of event reconstruction is comparable. For the Lambda hyperons we observe negative polarization along the W-boson direction which is enhanced in the target fragmentation region: Px(xF < 0) = -0.21 +- 0.04 (stat) +- 0.02 (sys). In the current fragmentation region we find Px(xF > 0) = -0.09 +- 0.06 (stat) +- 0.03(sys). A significant transverse polarization (in the direction orthogonal to the Lambda production plane) has been observed for the first time in a neutrino experiment: Py = -0.22 +- 0.03 (stat) +- 0.01 (sys). The dependence of the absolute value of Py on the Lambda transverse momentum with respect to the hadronic jet direction is in qualitative agreement with the results from unpolarized hadron-hadron experiments. The polarization vector of Lambda-bar hyperons measured for the first time in neutrino interactions is found to be consistent with zero.
eng
2002
http://th-www.if.uj.edu.pl/acta/vol33/abs/v33p3791.htm;
http://cds.cern.ch/record/557558/files/arXiv:hep-ph_0206032.pdf;
http://cds.cern.ch/record/557558/files/v33p3791.pdf;
http://cds.cern.ch/record/557558/files/0206032.pdf;
http://cds.cern.ch/record/557558/files/0206032.ps.gz;
Imported from Invenio.
Naumov, D V
Lambda Polarization in Deep-Inelastic Production
Acta Phys. Pol. B
3803-3808
33
We propose a model for the longitudinal polarization of Lambda baryons produced in deep-inelastic lepton scattering at any xF, based on static SU(6) quark-diquark wave functions and polarized intrinsic strangeness in the nucleon associated with individual valence quarks. Free parameters of the model are fixed by fitting the NOMAD data on the longitudinal polarization of Lambda hyperons in neutrino interactions. Our model correctly reproduces the observed dependences of Lambda polarization on the kinematic variables. Within the context of our model, the NOMAD data imply that the intrinsic strangeness associated with a valence quark has anticorrelated polarization. We also compare our model predictions with results from the HERMES and E665 experiments using charged leptons. Predictions of our model for the COMPASS experiment are also presented.
eng
2002
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0206031;
http://cds.cern.ch/record/557557/files/0206031.pdf;
http://cds.cern.ch/record/557557/files/0206031.ps.gz;
Imported from Invenio.
Ellis, John R.
Kotzinian, Aram
Naumov, Dmitry V.
Intrinsic Polarized Strangeness and Lambda Polarization in Deep-Inelastic Production
Eur. Phys. J. C
603-613
25
We propose a model for the longitudinal polarization of Lambda baryons produced in deep-inelastic lepton scattering at any xF, based on static SU(6) quark-diquark wave functions and polarized intrinsic strangeness in the nucleon associated with individual valence quarks. Free parameters of the model are fixed by fitting NOMAD data on the longitudinal polarization of Lambda hyperons in neutrino collisions. Our model correctly reproduces the observed dependences of Lambda polarization on the kinematic variables. Within the context of our model, the NOMAD data imply that the intrinsic strangeness associated with a valence quark has anticorrelated polarization. We also compare our model predictions with results from the HERMES and E665 experiments using charged leptons. Predictions of our model for the COMPASS experiment are also presented.
eng
2002
http://weblib.cern.ch/abstract?CERN-TH-2002-080;
http://cds.cern.ch/record/547521/files/arXiv:hep-ph_0204206.pdf;
http://cds.cern.ch/record/547521/files/0204206.ps.gz;
http://cds.cern.ch/record/547521/files/0204206.pdf;
Imported from Invenio.
Anselmino, M
Boer, D
D'Alesio, U
Murgia, F
Transverse Lambda polarization in inclusive processes
Int. J. Mod. Phys. A
1237-1246
18
A formalism proposed to study transverse Lambda polarization in unpolarized hadronic processes, based on a generalized pQCD factorization theorem, is extended to semi-inclusive DIS. Analytical expressions and examples of numerical estimates are given.
eng
2003
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0201076;
http://cds.cern.ch/record/535101/files/0201076.pdf;
http://cds.cern.ch/record/535101/files/0201076.ps.gz;
Imported from Invenio.
Arestov, Y
Polarization transfer in SIDIS for Lambda production
Polarization transfer from the longitudinally polarized positron to the final-state quark is considered for the underlying QCD subprocesses giving rise to the reaction e+(pol) + p --> e+ + Lambda(pol) + X at the HERMES energy.
eng
2001
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=physics&id=0111106;
http://cds.cern.ch/record/526616/files/0111106.pdf;
http://cds.cern.ch/record/526616/files/0111106.ps.gz;
Imported from Invenio.
Anselmino, M
Boer, D
D'Alesio, U
Murgia, F
Transverse Lambda polarization in semi-inclusive DIS
Phys. Rev. D
114014
65
Extending a previous description of Lambda and Lambda-bar polarization in unpolarized p-p interactions, within a pQCD factorization scheme with new polarizing fragmentation functions, we give predictions for the transverse polarization of Lambda's and Lambda-bar's in semi-inclusive DIS, both with neutral and charged currents. Comparison with existing data is not yet significant, but more experimental results are expected in the near future.
eng
2002
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0109186;
http://cds.cern.ch/record/520384/files/0109186.pdf;
http://cds.cern.ch/record/520384/files/0109186.ps.gz;
Imported from Invenio.
Anselmino, M
Boglione, M
D'Alesio, U
Murgia, F
Longitudinal Lambda polarization in polarized semi-inclusive DIS
We calculate, within pQCD parton model at leading orders, the expression of the longitudinal polarization of Lambda baryons produced in polarized semi-inclusive DIS, including weak interaction effects. We present some numerical estimates in few cases for which data are or will soon be available and discuss how to gather new information on polarized fragmentation functions.
eng
2001
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0106256;
http://cds.cern.ch/record/517922/files/0106256.pdf;
http://cds.cern.ch/record/517922/files/0106256.ps.gz;
Imported from Invenio.
Anselmino, M
Boer, D
D'Alesio, U
Murgia, F
Transverse Lambda polarization in unpolarized semi-inclusive DIS
The long-standing problem of transverse Lambda polarization in high-energy collisions of unpolarized hadrons can be tackled by considering new, spin and k_T-dependent quark fragmentation functions for an unpolarized quark into a polarized, spin-1/2 hadron. Simple phenomenological parameterizations of these new "polarizing fragmentation functions", which describe quite well the experimental data on Lambda and Lambda-bar hyperons produced in p-A processes, are utilized and extended here to give predictions for transverse Lambda polarization in semi-inclusive DIS
eng
2001
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0106254;
http://cds.cern.ch/record/517920/files/0106254.pdf;
http://cds.cern.ch/record/517920/files/0106254.ps.gz;
Imported from Invenio.
Sofer, A
Lambda-lambda bar polarization correlations
We present a measurement of the polarization of $\alam$ hyperons produced in $\nu_\mu$ charged current interactions. The full data sample from the NOMAD experiment has been analyzed using the same $\vo$ identification procedure and analysis method reported in a previous paper~\cite{NOMAD-polar} for the case of $\lam$ hyperons. The $\alam$ polarization has been measured for the first time in a neutrino experiment. The polarization vector is found to be compatible with zero.
eng
2001
http://weblib.cern.ch/abstract?CERN-EP-2001-028;
http://cds.cern.ch/record/494744/files/arXiv:hep-ex_0103047.pdf;
http://cds.cern.ch/record/494744/files/EPS_alam-cosy_corr.png;
http://cds.cern.ch/record/494744/files/EPS_v0_mass_1_3.png;
http://cds.cern.ch/record/494744/files/EPS_alam-cosx_corr.png;
http://cds.cern.ch/record/494744/files/EPS_alam-cosz_corr.png;
http://cds.cern.ch/record/494744/files/EPS_alam-cosz.png;
http://cds.cern.ch/record/494744/files/EPS_alam-cosy.png;
http://cds.cern.ch/record/494744/files/EPS_alam-cosx.png;
http://cds.cern.ch/record/494744/files/EPS_numu-distr-antilambda_1.png;
http://cds.cern.ch/record/494744/files/EPS_v0_raw_mass_one_plot_1_3.png;
http://cds.cern.ch/record/494744/files/EPS_r12875e12458_yz_bw.png;
http://cds.cern.ch/record/494744/files/ep-2001-028.ps.gz;
http://cds.cern.ch/record/494744/files/ep-2001-028.pdf;
Imported from Invenio.
Naumov, Dmitry V.
Measurement of Lambda polarization in muon neutrino charged current interactions in NOMAD
AIP Conf. Proc.
489-493
570
The Lambda polarization in muon neutrino charged current interactions has been measured in the NOMAD experiment. We observe negative polarization along the W - boson direction which is enhanced in the target fragmentation region: Px (xF < 0) = -0.21 +/- 0.04(stat) +/- 0.02(sys). In the current fragmentation region we find: Px (xF > 0) = -0.09 +/- 0.06(stat) +/- 0.03(sys). These results provide a test of different models describing the nucleon spin composition and the spin transfer mechanisms. A significant transverse polarization (in the direction orthogonal to the Lambda production plane) has been observed for the first time in a neutrino experiment: Py = -0.22 +/- 0.03(stat) +/- 0.01(sys). The dependence of the absolute value of Py on the Lambda transverse momentum with respect to the hadronic jet direction is in qualitative agreement with the results from unpolarized hadron-hadron experiments.
eng
2001-08-14
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0101325;
http://cds.cern.ch/record/485352/files/0101325.pdf;
http://cds.cern.ch/record/485352/files/0101325.ps.gz;
http://cds.cern.ch/record/485352/files/arXiv:hep-ph_0101325.pdf;
Imported from Invenio.
Bourrely, C
Soffer, J
Deep Inelastic Scattering of Leptons and Hadrons in the QCD Parton Model and Experimental Tests
Academic Press
1565-1581
We present the basic aspects of deep inelastic phenomena in the framework of the QCD parton model. After recalling briefly the standard kinematics, we discuss the physical interpretation of unpolarized and polarized structure functions in terms of parton distributions together with several important sum rules. We also make a rapid survey of the experimental situation together with phenomenological tests, in particular concerning various QCD predictions. In the summary, we try to identify some significant open questions, to clarify where we stand and to see what we expect to learn in the future.
eng
2002
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0101195;
http://cds.cern.ch/record/483903/files/0101195.pdf;
http://cds.cern.ch/record/483903/files/0101195.ps.gz;
Imported from Invenio.
Ma Bo Qiang
Schmidt, Ivan
Yang Jian Jun
Ratio of $\bar{\Lambda}/\Lambda$ in Semi-inclusive Electroproduction
Phys. Lett. B
35-40
574
It is shown that the $\bar{\Lambda}/\Lambda$ cross section ratio in semi-inclusive electroproduction of $\Lambda$ and $\bar{\Lambda}$ hyperons in deep inelastic scattering of charged lepton on a nucleon target, can provide useful information on the quark to $\Lambda$ fragmentation functions. This ratio is calculated explicitly in a quark-diquark model, a pQCD based analysis, and an SU(3) symmetry model, with three different options for the contribution from the unfavored fragmentation functions. The $x$-dependence of this ratio is sensitive to the ratio of unfavored fragmentation functions over favored fragmentation functions, $D_{\bar{u}}^{\Lambda}(z)/D_{u}^{\Lambda}(z)$, whereas the $z$-dependence is sensitive to the flavor structure of the fragmentation functions, i.e., the ratio $D_u^{\Lambda}(z)/D_s^{\Lambda}(z)$. Future measurements by the HERMES Collaboration at DESY can discriminate between various cases.
eng
2003
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0403010;
http://cds.cern.ch/record/720451/files/0403010.pdf;
Imported from Invenio.
Ma, B Q
Schmidt, I
Soffer, J
Yang Jian Jun
Helicity and Transversity Distribution of Nucleon and $\Lambda$-Hyperon from $\Lambda$ Fragmentation
Phys. Rev. D
014017
64
It is shown that $\Lambda$-hyperon fragmentation in charged lepton deep inelastic scattering (DIS) on a polarized nucleon target can provide sensitive information concerning the quark helicity and transversity distributions for both nucleon and $\Lambda$-hyperon at large $x$. Numerical predictions are given for the spin transfers of the produced $\Lambda$, when the target nucleon is polarized either longitudinally or transversely, and with the nucleon and $\Lambda$ quark distributions evaluated both in an SU(6) quark-spectator-diquark model and in a perturbative QCD (pQCD) based model. It is also shown that the predicted spin transfers have different behaviors for proton and neutron targets, and this can provide sensitive tests of different predictions for the quark helicity and transversity distributions of the $d$ valence quark of the proton at large $x$.
eng
2001
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0103136;
http://cds.cern.ch/record/491213/files/0103136.pdf;
http://cds.cern.ch/record/491213/files/0103136.ps.gz;
Imported from Invenio.
Yang Jian Jun
$q \to \Lambda$ Fragmentation Function and Nucleon Transversity Distribution in a Diquark Model
Nucl. Phys. A
562-578
699
Based on a simple quark-diquark model, we propose a set of unpolarized, longitudinally polarized and transversely polarized fragmentation functions for the $\Lambda$ by fitting the unpolarized $\Lambda$ production data in $e^+ e ^- $ annihilation. It is found that the helicity structure of the obtained $\Lambda$ fragmentation functions is supported by the all available experimental data on the longitudinal $\Lambda$ polarization. Within the same framework of the diquark model, the nucleon transversity distributions are presented and consistent descriptions of the available HERMES data on the azimuthal spin asymmetries in pion electroproduction are obtained. Furthermore, the spin transfers to the transversely polarized $\Lambda$ in the charged lepton DIS on a transversely polarized nucleon target are predicted for future experiments.
eng
2002
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=hep-ph&id=0111382;
http://cds.cern.ch/record/528574/files/0111382.pdf;
http://cds.cern.ch/record/528574/files/0111382.ps.gz;
Imported from Invenio.