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Lambda 1995-2000
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1.
Spin content of the $\Lambda$ hyperon / Kim, H C ; Praszalowicz, M ; Göke, K
Using the known experimental data for the hyperon semileptonic decayconstants, we calculate integrated quark densities $\Delta q_\Lambda$ and $\Delta \Sigma_\Lambda$ for the hyperon $\Lambda$ with flavor SU(3) symmetrybreaking taken into account. Symmetry breaking is implemented with the help ofthe chiral quark-soliton model in an approach, in which the dynamicalparameters are fixed by the experimental data for six hyperon semileptonicdecay constants. [...]
hep-ph/0003076; PNU-NTG-2000-01; RUB-TP-2-2000-4.- Bochum : Bochum TU. Inst. Theor. Phys. 2, 2000 - Published in : Acta Phys. Pol. B 31 (2000) 1767
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2.
$\Lambda$ and $\overline{\Lambda}$ polarization as a measurement of distribution and fragmentation functions / Anselmino, M ; Boglione, M ; Murgia, F
A combined analysis of the polarization vector of the Lambda baryons produced in DIS processes may give a relevant insight of the hadronization process which governs the transition from partons to physical hadrons and precise indications on the mechanisms of $spin$ transfer from partons to hadrons. We give here a short review of some interesting results..
hep-ph/0010166.- 2000 - Published in : AIP Conf. Proc. 588 (2001) 255-259 Access to fulltext document: PDF; External link: hep-ph/0010166 PDF
In : 2nd Workshop on Physics with an Electron Polarized Light-Ion Collider, Cambridge, MA, USA, 14 - 16 Sep 2000, pp.255-259
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3.
Measurement of the $\Lambda$ polarization in $\nu_\mu$ charged current interactions in the NOMAD experiment / NOMAD Collaboration
The $\Lambda$ polarization in $\nu_\mu$ 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 event reconstruction is comparable [...]
CERN-EP-2000-111.- Geneva : CERN, 2000 - 12 p. - Published in : Nucl. Phys. B 588 (2000) 3-36 Fulltext: PDF; Source files restricted to CERN users: ZIP; - CERN library copies
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4.
Lambda polarization from unpolarized quark fragmentation / Anselmino, M ; Boer, D ; D'Alesio, U ; Murgia, F
The longstanding problem of explaining the observed polarization of Lambda hyperons inclusively produced in the high energy collisions of unpolarized hadrons is tackled by considering spin and k_T dependent quark fragmentation functions. The data on Lambda's and Lambda-bar's produced in p-N processes are used to determine simple phenomenological expressions for these new "polarizing fragmentation functions", which describe the experiments remarkably well..
hep-ph/0008186; DFTT-2000-32; INFNCA-TH-2000-12.- Torino : Torino Univ., 2001 - 1 p. - Published in : Phys. Rev. D 63 (2001) 054029 Access to fulltext document: PDF; External link: hep-ph/0008186 PDF
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5.
The contribution of $\Sigma^* \to \Lambda\pi$ to measured $\Lambda$ polarization / Ashery, D ; Lipkin, Harry Jeannot
Calculations of the polarization of $\Lambda$ and $\bar{\Lambda}$ particlesafter fragmentation of a polarized quark produced in processes like $Z$-decayand deep inelastic polarized lepton scattering must include $\Lambda$ and$\bar{\Lambda}$ produced as decay products of $\Sigma^0$ and $\Sigma^*$ as wellas those produced directly [...]
hep-ph/0002144. - 2000. - 6 p.
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6.
$\Lambda$ and $\overline{\Lambda}$ polarization in polarized DIS / Anselmino, M ; Boglione, M ; Murgia, F
We consider the polarization of Lambda + Lambda-bar baryons produced in polarized Deep Inelastic Scattering at leading order, with various spin configurations: longitudinally polarized leptons and unpolarized nucleon; unpolarized leptons and longitudinally or transversely polarized nucleons; longitudinally polarized leptons and nucleons. We show how the different results in the different cases are related to different aspects of the elementary dynamics and to the spin properties of the distribution and fragmentation functions and show how a combined analysis might give useful information. [...]
hep-ph/0001307; INFNCA-TH-2000-1.- 2000 - Published in : Phys. Lett. B 481 (2000) 253-262 Access to fulltext document: PDF; External link: hep-ph/0001307 PDF
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7.
$\Lambda$, $\overline{\Lambda}$ polarization and spin transfer in lepton deep-inelastic scattering / Ma, B Q ; Schmidt, I ; Soffer, J ; Yang Jian Jun
The flavor and helicity distributions of the $\Lambda$ and $\bar{\Lambda}$ hyperons for both valence and sea quarks are calculated in a perturbative QCD (pQCD) based model. We relate these quark distributions to the fragmentation functions of the $\Lambda$ and $\bar{\Lambda}$, and calculate the $z$- and $p_T$-dependence of the longitudinal spin transfer to the $\Lambda$ and spin transfer to the $\Lambda$ is compatible with the first HERMES results at DESY and further tests are suggested. [...]
hep-ph/0001259; CPT-3952; USM-TH-87.- Valparadíso : Santa Maria Univ. Dept. Fís., 2000 - 25 p. - Published in : Eur. Phys. J. C 16 (2000) 657-664 Access to fulltext document: PDF; External link: hep-ph/0001259 PDF
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8.
$\Lambda$ and $\overline{\Lambda}$ polarization from deep inelastic muon scattering / Adams, M R
We report results of the first measurements of Lambda and Antilambda polarization produced in deep inelastic polarized muon scattering on the nucleon. The results are consistent with an expected trend towards positive polarization with increasing x_F. [...]
hep-ex/9911004.- 2000 - Published in : Eur. Phys. J. C 17 (2000) 263-267 Access to fulltext document: PDF; External link: hep-ex/9911004 PDF
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9.
Expected Polarization of $\Lambda$ particles produced in deep inelastic polarized lepton scattering / Ashery, D ; Lipkin, Harry Jeannot
We calculate the polarization of Lambda and Anti-Lambda particles produced in deep inelastic polarized lepton scattering. We use two models: the naive quark model and a model in which SU(3)$_F$ symmetry is used to deduce the spin structure of SU(3) octet hyperons from that of the proton [...]
hep-ph/9908355.- 1999 - Published in : Phys. Lett. B 469 (1999) 263-269 Access to fulltext document: PDF; External link: hep-ph/9908355 PDF
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10.
Lambda polarization in lepton-induced reactions / Kotzinian, A M (Dubna, JINR)
Different phenomenological approaches for Lambda and Lambda-bar polarization in polarized semi-inclusive deep inelastic scattering and electron-positron annihilation at Z^0 pole are considered. [...]
hep-ph/9709259. - 1997. - 7 p.
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11.
$\Lambda$ and $\overline\Lambda$ Polarization in Lepton Induced Processes / Kotzinian, A M ; Bravar, A ; Von Harrach, D
The study of the longitudinal polarization of Lambda and Lambda-bar hyperons produced in polarized deep inelastic scattering, neutrino scattering, and in Z0 decays allows to access the spin dynamics of the quark fragmentation process. Different phenomenological spin transfer mechanisms are considered and predictions for the Lambda and Lambda-bar longitudinal polarization in various processes using unpolarized and polarized targets are made. [...]
hep-ph/9701384.- Geneva : CERN, 1998 - Published in : Eur. Phys. J. C 2 (1998) 329-337 Access to fulltext document: PDF; External link: hep-ph/9701384 PDF - CERN library copies
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12.
Measurement of Longitudinal Spin Transfer to $\Lambda$ Hyperons in Deep-Inelastic Lepton Scattering / Airapetian, A
Spin transfer in deep-inelastic Lambda electroproduction has been studied with the HERMES detector using the 27.5 GeV polarized positron beam in the HERA storage ring. [...]
hep-ex/9911017 ; DESY-99-151. - 1999. - 12 p.
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13.
Flavor and Spin Structure of $\Lambda$-Baryon at Large x / Ma, B Q ; Schmidt, I ; Yang Jian Jun
It is shown that perturbative QCD (pQCD) and the SU(6) quark-diquark model give significant different predictions concerning the flavor and spin structure for the quark distributions of the $\Lambda$-baryon near $x=1$. Detailed predictions for the ratios $u(x)/s(x)$ of unpolarized quark distributions, up and down quarks of the $\Lambda$ are given from the quark-diquark model and from a pQCD based model. [...]
hep-ph/9906424; USM-TH-77.- Valparadíso : Santa Maria Univ. Dept. Fís., 2000 - 11 p. - Published in : Phys. Lett. B 477 (2000) 107-113 Access to fulltext document: PDF; External link: hep-ph/9906424 PDF
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14.
The strange quark spin of the proton in semi-inclusive $\Lambda$ leptoproduction / Lu, W ; Ma, B Q
Considering the possible interpretation of the Ellis-Jaffe sum rule violation that the strange quark in the polarized proton is remarkably polarized in the opposite direction of the proton spin, we investigate its implication in the semi-inclusive \Lambda production in deep inelastic process with the electron beam unpolarized and proton target polarized longitudinally. [...]
hep-ph/9507403. - 1995. - 9 p.
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15.
The proton spin puzzle and $\Lambda$ polarization in deep-inelastic scattering / Ellis, Jonathan Richard (CERN) ; Kharzeev, Dima E ; Kotzinian, A M
We point out that measurements of longitudinal \Lambda polarization in the target fragmentation region of deep--inelastic \nu \,N and \mu \,N or e \, N scattering may test dynamical mechanisms invoked to explain the proton spin puzzle. A previously-proposed model for polarized \bar s s pairs in the proton wave function reproduces successfully the negative \Lambda polarization found in the WA59 \bar \nu \, N experiment, and makes predictions that could be tested in future \mu \, N and e \, N experiments..
hep-ph/9506280; CERN-TH-95-135.- Geneva : CERN, 1996 - 17 p. - Published in : Z. Phys. C 69 (1996) 467-474 Access to fulltext document: 9506280 - PDF; 9506280.fig1 - PDF; External link: hep-ph/9506280 PDF - CERN library copies
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16.
The proton spin puzzle and depolarization in $\overline{p}$p --> $\overline{\Lambda}\Lambda$ / Alberg, M A ; Ellis, Jonathan Richard (CERN) ; Kharzeev, Dima E
We point out that the measurement of target spin depolarization D_{nn} in the \bar{p}p\to\bar{\Lambda}\Lambda reaction may test dynamical mechanisms invoked to explain the proton spin puzzle revealed by polarized deep--inelastic scattering experiments. In particular, models with {\it negatively} polarized \bar{s}s pairs in the proton wave function predict D_{nn}<0, whereas models with {\it positively} polarized gluons would predict D_{nn}>0..
hep-ph/9503333; CERN-TH-95-47; DOE-ER-40427-2004-N-95.- Geneva : CERN, 1995 - 7 p. - Published in : Phys. Lett. B 356 (1995) 113-117 Access to fulltext document: 9503333 - PDF; 9503333.fig1 - PDF; Fulltext: PDF; External link: hep-ph/9503333 PDF - CERN library copies
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17.
Deep Inelastic Scattering of Leptons and Hadrons in the QCD Parton Model and Experimental Tests / Bourrely, C ; Soffer, J
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. [...]
hep-ph/0101195; CPT-4092.- 2002 - 29 p. - Published in : Academic Press (2002) , pp. 1565-1581 Fulltext: PDF; External link: hep-ph/0101195 PDF
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18.
The Flavor and Spin Structure of Hyperons from Quark Fragmentation / Ma, B Q ; Schmidt, I ; Soffer, J ; Yang Jian Jun
We systematically study the hadron longitudinal polarizations of the octet baryons at large $z$ from quark fragmentations in $e^+e^-$-annihilation, polarized charged lepton deep inelastic scattering (DIS) process, and neutrino (antineutrino) DIS process, based on predictions of quark distributions for the octet baryons in the SU(6) quark-spectator-diquark model and a perturbative QCD based counting rule analysis. We show that the $e^+e^-$-annihilation and polarized charged lepton DIS process are able to distinguish between the two different predictions of the hyperon polarizations. [...]
hep-ph/0008295; CPT-4032; USM-TH-95.- Valparadíso : Santa Maria Univ. Dept. Fís., 2000 - 32 p. - Published in : Phys. Rev. D 62 (2000) 114009 Access to fulltext document: PDF; External link: hep-ph/0008295 PDF
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19.
The Quark-Antiquark Asymmetry of the Nucleon Sea from $\Lambda$ and $\bar{\Lambda}$ Fragmentation / Ma, B Q ; Schmidt, I ; Soffer, J ; Yang Jian Jun
We present a general analysis of the spin transfer for $\Lambda$ and $\bar{\Lambda}$ production in deep-inelastic scattering of polarized charged leptons on the nucleon, and find that the pattern of different behaviors of $\Lambda$ and $\bar{\Lambda}$ production observed by the E665 Collaboration suggests the possibility of quark-antiquark asymmetries either in the quark to $\Lambda$ fragmentation functions and/or in the quark and antiquark distributions of the target proton. We also point out that the strange-antistrange asymmetry of the nucleon sea may produce an observable contribution to the different behaviors of $\Lambda$ and $\bar{\Lambda}$ production. [...]
hep-ph/0005210; USM-TH-92.- Valparadíso : Santa Maria Univ. Dept. Fís., 2000 - 15 p. - Published in : Phys. Lett. B 489 (2000) 293-299 Access to fulltext document: PDF; External link: hep-ph/0005210 PDF
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20.
Quark Flavor Separation in $\Lambda$-Baryon Fragmentation / Ma, B Q ; Soffer, J
It is shown that neutrino and antineutrino deep inelastic scattering of unpolarized and polarized $\Lambda$ and $\bar{\Lambda}$ productions, can provide a clean separation of unpolarized and polarized fragmentation functions of a quark into a $\Lambda$, for both light-flavor quarks and antiquarks and also for strange quarks. Combining with $\Lambda$ and $\bar{\Lambda}$ productions, in polarized electron deep inelastic scattering, one can systematically measure or check the various flavor and spin dependent fragmentation functions. [...]
hep-ph/9810517; BIHEP-TH-98-8; CPT-3706.- Beijing : Acad. Sin. Inst. High Energy Phys., 1999 - 11 p. - Published in : Phys. Rev. Lett. 82 (1999) 2250 Access to fulltext document: PDF; External link: hep-ph/9810517 PDF
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