Inclusive K∗−(890) and (890) production in 14.3 GeV/c K−p interactions

Paler, K.; Tovey, S. N.; Shah, T.; Phelan, J.J.; Miller, R.J.; Spiro, M.; Barloutaud, R.; Bardadin-Otwinowska, M.; Borg, A.; Chaurand, B.; Drévillon, B.; Gago, J.; Salmeron, R.

doi:10.1016/0550-3213(75)90454-x

Cited by 34 publications

(7 citation statements)

References 47 publications

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“…An early experiment [2] reported no spin alignment of K * (892) ± produced in pp interactions at 12 and 24 GeV. Significant spin alignment has been observed for leading vector mesons inclusively produced by charged kaons: for K * (892) + and K * (892) 0 in K + p reaction at 8.2 GeV [3], 32 GeV [4] and 70 GeV [5], for K * (892) − and K * (892) 0 in K − p interactions at 14.3 GeV [6] and 32 GeV [7].…”

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confidence: 94%

Spin alignment of mesons produced in neutron-carbon interactions

Aleev

Amaglobeli²,

Balandin³

et al. 2000

Physics Letters B

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A new precise measurements of spin density matrix element ρ 00 of K * (892) ± mesons produced inclusively in neutron-carbon interactions at ∼ 60 GeV have been carried out in the EXCHARM experiment at the Serpukhov accelerator. The values of ρ 00 obtained in the transversity frame are 0.424 ± 0.011(stat) ± 0.018(sys) for K * (892) + and 0.393 ± 0.025(stat) ± 0.018(sys) for K * (892) − . Significant P T dependence of ρ 00 has been observed in K * (892) + production.

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confidence: 94%

Spin alignment of mesons produced in neutron-carbon interactions

Aleev

Amaglobeli²,

Balandin³

et al. 2000

Physics Letters B

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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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“…On the other hand measurements of off diagonal spin density matrix elements are consistent with zero ruling out coherence models [22][23][24] which predicted non zero off diagonal elements. The spin alignment measurements for K * 0 and K * + vector mesons have also been studied in kp and nC interaction [28][29][30][31][32] with respect to the direction perpendicular to the production plane. In these experiments, the measured ρ 00 values are found to be larger than the 1/3 and can be explained by a parton recombination model 34 which attributes to the spin alignment of vector mesons via Thomas precession of the quark's spins in the recombination process of hadronization.…”

Section: Discussionmentioning

confidence: 99%

“…Spin density matrix element ρ 00 for K * 0 and K * + have also been studied in kp and nC interaction [28][29][30][31][32] with respect to the direction the perpendicular to production plane. The ρ 00 values in these measurements are found to be significantly higher than the 1/3 which can be explained by a parton recombination model 34 and attributes the spin alignment of vector mesons via Thomas precession of the quark's spin in the recombination process of hadronization.…”

Section: Spin Alignment Measurements In Small Collision Systemmentioning

confidence: 99%

Spin alignment measurement of vector mesons produced in high energy collisions

Mohanty,

Kundu,

Singha

et al. 2021

Preprint

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This review covers the recent experimental development on spin alignment measurements of K * 0 and φ vector mesons in heavy-ion and pp collisions at RHIC and LHC energies.Measurements in e + e − collisions at LEP energies are also discussed. Spin alignment of vector mesons are studied by measuring the second diagonal element ρ 00 of spin density matrix. The spin density matrix element ρ 00 is obtained by measuring the angular distribution of vector meson decay daughter with respect to the quantization axis in vector meson rest frame. Measured ρ 00 values for vector mesons are found to be larger than 1/3 at high momentum in e + e − collisions at LEP energies, suggesting the preferential production of vector meson with helicity zero state from the fragmentation process. The ρ 00 values are found to be smaller than 1/3 (ρ 00 = 1/3 implies no spin alignment) for K * 0 and φ vector mesons at low transverse momentum in Pb-Pb collisions at √ s NN = 2.76 TeV. This observations are qualitatively consistent with the expectation from models which attribute the spin alignment effect due to polarization of quarks in the presence of large initial angular momentum in non-central heavy-ion collisions and its subsequent hadronization by the process of recombination. No significant spin alignment effect is observed for K 0 S (spin = 0) in mid-central Pb-Pb collisions and for vector mesons in pp collisions. However, the preliminary results of ρ 00 for φ mesons are larger than 1/3 at intermediate p T in Au-Au collisions at RHIC energies and can be attributed to the presence of φ meson field. Although there is evidence of spin alignment effect of vector mesons in heavy-ion collisions but the measured effect is surprisingly larger in context

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Inclusive K∗−(890) and (890) production in 14.3 GeV/c K−p interactions

Cited by 34 publications

References 47 publications

Spin alignment of mesons produced in neutron-carbon interactions

Spin alignment of mesons produced in neutron-carbon interactions

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

Spin alignment measurement of vector mesons produced in high energy collisions

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