Spin alignment of mesons produced in neutron-carbon interactions

Aleev, A.N.; Amaglobeli, N.S.; Balandin, V. P.; Bugorski, A.P.; Cheshkov, C.; Gaponenko, A.; Geshkov, I.M.; Grigalashvili, T.S.; Hristov, P.; Ivanchenko, I.M.; Ivanchenko, Z.M.; Kapishin, Mikhail; Karpenko, N.N.; Kekelidze, V.; Khristova, T.V.; Kojenkova, Z.I.; Kopadze, M.V.; Kosarev, I.; Kretov, Yu.A.; Kurilin, A. S.; Kuzmin, N.; Kvatadze, R.; Lavrentyev, A.A.; Loktionov, A. A.; Lomidze, N.; Lyubimov, A.L.; Madigojin, D.T.; Mestvirishvili, A.; Molokanova, N.; Morozov, A.; Panacik, A.A.; Ponta, T.; Potrebenikov, Yu.; Preda, T.; Skripnichuk, A.G.; Slepets, L.A.; Spaskov, V.; Tatishvili, G.; Tkatchev, A.; Zinchenko, A.

doi:10.1016/s0370-2693(00)00704-8

Cited by 13 publications

(5 citation statements)

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“…It has been shown that the existence of the spin alignment of vector mesons in unpolarized hadron-hadron collision is another manifestation of the existence of the s q · n type of spin correlation. The obtained result are in agreement with the available data [26,27,28].…”

Section: The Physical Picturesupporting

confidence: 92%

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Hyperon polarization in different inclusive production processes in unpolarized high energy hadron-hadron collisions

Dong

Liang

2004

Phys. Rev. D

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We apply the picture proposed in a previous Letter, which relates the hyperon polarization in unpolarized hadron-hadron collisions to the left-right asymmetry in singly polarized reactions, to the production of different hyperons in reactions using different projectiles and/or targets. We discuss the different ingredients of the proposed picture in detail and present the results for hyperon polarization in the reactions such as pp, K − p, π ± p, and Σ − p collisions. We compare the results with the available data and make predictions for future experiments.

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Section: The Physical Picturesupporting

confidence: 92%

“…(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31) to get the numerical results for P Λ (x F |s) as a function of x F .…”

Section: Resultsmentioning

confidence: 99%

Hyperon polarization in different inclusive production processes in unpolarized high energy hadron-hadron collisions

Dong

Liang

2004

Phys. Rev. D

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“…In the past, spin alignment measurements in e þ e − [31][32][33], hadron-proton [34] and nucleon-nucleus collisions [35] were carried out to understand the role of spin in the dynamics of particle production, finding ρ 00 > 1=3 and off-diagonal elements close to zero with respect to the PP. For pp collisions at ffiffi ffi s p ¼ 13 TeV, we find ρ 00 ∼ 1=3…”

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confidence: 99%

Evidence of Spin-Orbital Angular Momentum Interactions in Relativistic Heavy-Ion Collisions

Acharya¹,

Adamová²,

Adler³

et al. 2020

Phys. Rev. Lett.

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137

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The first evidence of spin alignment of vector mesons (K Ã0 and ϕ) in heavy-ion collisions at the Large Hadron Collider (LHC) is reported. The spin density matrix element ρ 00 is measured at midrapidity (jyj < 0.5) in Pb-Pb collisions at a center-of-mass energy (ffiffiffiffiffiffiffi ffi s NN p) of 2.76 TeV with the ALICE detector. ρ 00 values are found to be less than 1=3 (1=3 implies no spin alignment) at low transverse momentum (p T < 2 GeV=c) for K Ã0 and ϕ at a level of 3σ and 2σ, respectively. No significant spin alignment is observed for the K 0 S meson (spin ¼ 0) in Pb-Pb collisions and for the vector mesons in pp collisions. The measured spin alignment is unexpectedly large but qualitatively consistent with the expectation from models which attribute it to a polarization of quarks in the presence of angular momentum in heavy-ion collisions and a subsequent hadronization by the process of recombination.

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“…Other elements, ρ 10 and ρ 1−1 , can be studied by further measuring W (θ, φ). In fact, such measurements have already been carried out in lepton induced reactions and hadron-hadron collisions [4,5,6,7,8,9,10,11,12,13,16,17,18]. Unlike the polarization of hyperons, the spin-alignment of vector mesons, ρ V 00 , does not know the direction of the reaction plane since it only depends on cos 2 θ [see Eq.…”

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confidence: 99%

Spin alignment of vector mesons in non-central A+A collisions

2005

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We discuss the consequence of global polarization of the produced quarks in non-central heavy-ion collisions on the spin alignment of vector mesons. We show that the alignment is quite different for different hadronization scenarios. These results can be tested directly by measuring the vector mesons' alignment through angular distributions of the decay products with respect to the reaction plane. Such angular distributions will give rise to azimuthal anisotropy v2 of the decay products in the collision frame. Constraints provided by the data on the azimuthal anisotropy of hadron spectra at RHIC points to a quark recombination scenario of hadronization.PACS numbers: 13.88.+e, 12.38.Mh, 25.75.Nq Due to the presence of a large orbital angular momentum of the parton system produced at the early stage of non-central heavy-ion collisions, quarks and anti-quarks are shown recently [1] to be polarized in the direction opposite to the reaction plan which is determined by the vector of impactparameter and the beam momentum. Such global quark polarization should have many observable consequences such as left-right (with respect to the quarks' spin polarization) asymmetry in hadron spectra at large rapidity, global polarization of thermal photons, dileptons and final hadrons with spin. The left-right asymmetry of hadrons from the hadronization of such globally polarized quarks effectively gives rise to a "directed flow". However, it is difficult to disentangle it from the true directed flow due to interaction between produced matter and the spectator nucleons. Global hyperon polarization from the hadronization of polarized quarks are predicted [1] independently of the hadronization scenarios. Measurements of such global hyperon polarization are made possible by the self-analyzing power of the hyperon's parity-violating decay [2], which produces an angular distribution, dN/d cos θ = 1 + αP H cos θ, for its decay products with respect to the polarization direction. Here, α is a constant (e.g., α = 0.642 for Λ → pπ − ) and P H is the hyperon's polarization. In practice, one needs to know not only the orientation but also the sign (or direction) of the reaction plane which can only be determined by the directed flow in each event class. If one sums over events with opposite reaction planes, the effect of the hyperon's polarization on the angular distribution of its decay products will cancel. While such measurements are underway, other consequences can and should be studied.In this note, we discuss the spin alignment of vector mesons due to the global quark polarization in non-central A + A collisions. Similarly as in Ref.[1], we consider two colliding nuclei with the projectile of beam momentum p moving in the direction of the z axis. The impact parameter b is taken as alongx, which is the transverse distance of the projectile from the target nucleus. The norm of the reaction plane is given by n b ≡ p × b/| p × b| and is alongŷ. For a non-central collision, the dense matter produced in the overlapped region of the collisi...

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Spin alignment of mesons produced in neutron-carbon interactions

Cited by 13 publications

References 13 publications

Hyperon polarization in different inclusive production processes in unpolarized high energy hadron-hadron collisions

Hyperon polarization in different inclusive production processes in unpolarized high energy hadron-hadron collisions

Evidence of Spin-Orbital Angular Momentum Interactions in Relativistic Heavy-Ion Collisions

Spin alignment of vector mesons in non-central A+A collisions

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