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Longitudinal polarizations of different kinds of hyperons produced in e+e- annihilation at LEP I and LEP II energies in different event samples are calculated using two different pictures for the spin structure of hyperon: that drawn from…

High Energy Physics - Phenomenology · Physics 2009-10-31 Chun-xiu Liu , Zuo-tang Liang

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,…

High Energy Physics - Phenomenology · Physics 2015-06-25 M. Anselmino , D. Boer , U. D'Alesio , F. Murgia

The longitudinal polarization of hyperons in $e^+e^-$ annihilation at high energies depends on the longitudinal polarization of the quark produced at the $e^+e^-$ annihilation vertex whereas the spin alignment of vector mesons is…

High Energy Physics - Phenomenology · Physics 2017-02-22 Kai-bao Chen , Wei-hua Yang , Ya-jin Zhou , Zuo-tang Liang

The possibility is examined for the inclusive $\Lambda$ in unpolarized electron-positron annihilation to be transversely polarized. Due to final-state interactions, there exists a novel structure function $\hat F(z,Q^2)$ for the inclusive…

High Energy Physics - Phenomenology · Physics 2009-10-28 Wei Lu

Data from the Belle Collaboration for associated production (with a light unpolarized hadron) and single-inclusive production of transversely polarized $\Lambda$-hyperons in $e^+e^-$ annihilation processes allowed to extract within a TMD…

High Energy Physics - Phenomenology · Physics 2023-01-18 Marco Zaccheddu , Umberto D'Alesio , Leonard Gamberg , Francesco Murgia

We discuss the production of polarized hadrons in polarized lepton nucleon interactions and show that the helicity density matrix of the hadron, when measurable, can give information on the spin structure of the nucleon and the spin…

High Energy Physics - Phenomenology · Physics 2007-05-23 M. Anselmino , M. Boglione , J. Hansson , F. Murgia

The importance of polarised gluons fragmenting into $\Lambda$ in the polarised $e^+ e^-$ annihilation is discussed using the Altarelli-Parisi evolution equations satisfied by the quark and gluon fragmentation functions. In this context, the…

High Energy Physics - Phenomenology · Physics 2014-11-17 V. Ravindran

Using the helicity formalism of Jacob and Wick we derive spin density matrices of baryon antibaryon pairs produced in $e^+e^-$ annihilation. We consider the production of pairs with spins $1/2+\overline{1/2}$, $1/2+\overline{3/2}$ (+c.c.)…

High Energy Physics - Phenomenology · Physics 2019-03-27 Elisabetta Perotti , Göran Fäldt , Andrzej Kupść , Stefan Leupold , Jiao Jiao Song

The independent helicity amplitudes in the (Lambda_b -> \Lambda l^+ l^-) decay in the standard model and its minimal extension, i.e., with the new vector type interactions, are calculated. We calculate various asymmetry parameters…

High Energy Physics - Phenomenology · Physics 2009-11-11 T. M. Aliev , M. Savci

Experimental data from Belle Collaboration for the transverse polarization of $\Lambda$'s measured in $e^+ e^-$ annihilation processes are used to extract the polarizing fragmentation function (FF) within a TMD approach. We consider both…

High Energy Physics - Phenomenology · Physics 2021-08-03 Umberto D'Alesio , Francesco Murgia , Marco Zaccheddu

We investigate the quantum correlated $\Lambda \bar{\Lambda} $ production in the reaction $e^{+}e^{-} \to J/\psi \to \Lambda \bar{\Lambda}$. Since the $\Lambda$ or $\bar{\Lambda}$ has a nonzero magnetic moment, its spin will undergo a…

High Energy Physics - Phenomenology · Physics 2019-10-16 Hai-Bo Li , Xin-Xin Ma

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…

High Energy Physics - Phenomenology · Physics 2014-11-17 Bo-Qiang Ma , Ivan Schmidt , Jacques Soffer , Jian-Jun Yang

Evidence for CP violation in baryonic decays has not been seen in experiments. With large data events accumulated at $e^+e^-$ collider or Large Hadron Collider, the charmed baryon decays would provide a promising laboratory to test the CP…

High Energy Physics - Phenomenology · Physics 2022-11-30 PengCheng Hong , Fang Yan , RongGang Ping , Tao Luo

The interference fragmentation function translates the fragmentation of a quark with a transverse projection of the spin into an azimuthal asymmetry of two final-state hadrons. In e+e- annihilation the product of two interference…

Since the first surprising results on the spin structure of the proton by the EMC experiment in the late 1980s, much progress has been made in understanding the origin of the proton spin. However, the sea quark contribution to the proton…

High Energy Physics - Experiment · Physics 2023-09-26 Yi Yu

Studies of hadronic final states of $e^+e^-$ annihilations, observed at the Large Electron Positron Collider LEP at CERN, are reviewed. The topics included cover measurements of $\alpha_s$, hadronic event shapes and hadronisation studies,…

High Energy Physics - Experiment · Physics 2014-11-17 Siegfried Bethke

We present new sets of fragmentation functions for D^{*+-} mesons, both at leading and next-to-leading order. They are determined by fitting LEP1 data on inclusive D^{*+-} production in e^+e^- annihilation. In one of the sets, we take the…

High Energy Physics - Phenomenology · Physics 2008-02-03 J. Binnewies , B. A. Kniehl , G. Kramer

We calculate the spin density matrix of the hadron $h$ created via quark fragmentation in the process $e^-e^+ \to q\bar q \to h + X$. In the case of $h=\Lambda$ the experimental data could possibly elucidate the problem of $s$-quark…

High Energy Physics - Phenomenology · Physics 2007-05-23 A. Anselm , M. Anselmino , F. Murgia , M. G. Ryskin

We present new sets of next-to-leading order fragmentation functions for the production of K0short and Lambda particles from the gluon and from each of the quarks, obtained by fitting to all relevant data sets from e+e- annihilation. The…

High Energy Physics - Phenomenology · Physics 2009-09-29 S. Albino , B. A. Kniehl , G. Kramer

The transverse polarization observed in the inclusive production of Lambda hyperons in the high energy collisions of unpolarized hadrons is tackled by considering a new set of spin and kT dependent quark fragmentation functions. Simple…

High Energy Physics - Phenomenology · Physics 2009-10-31 M. Anselmino , D. Boer , U. D'Alesio , F. Murgia