Spin alignment of vector mesons in high energy 
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Chen, Kai-bao; Liang, Zuo-tang; Song, Y.; Wei, Shu-Yi

doi:10.1103/physrevd.102.034001

Cited by 12 publications

(4 citation statements)

References 80 publications

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“…Another popular choice of local frame is the helicity frame, in which vector meson's momentum direction is taken as the quantization axis. An analytical relation between global ρ 00 and the helicity frame ρ 00 does not exist, but based on our simulation for the same kinematic range, typical values of ρ 00 in the helicity frame (in between 0.2 and 0.6 49 ) will result in the global ρ 00 deviating from 1/3 by only ∼ 0.001 and ∼ 0.01 for φ and K * 0 mesons, respectively, which are either negligible or very small when compared to the (ρ 00 − 1/3) observations presented in this work. In a recent work, it is argued that the gradient of the radial flow along the beam axis can generate transverse vorticity loops at finite rapidity, and cause the transverse local spin alignment 27 .…”

Section: Reconstruction Of Event Planementioning

confidence: 91%

Pattern of Global Spin Alignment of $ϕ$ and $K^{*0}$ mesons in Heavy-Ion Collisions

Collaboration¹,

Abdallah²,

E.³

et al. 2022

Preprint

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The strong force, as one of the four fundamental forces at work in the universe, governs interactions of quarks and gluons, and binds together the atomic nucleus. Notwithstanding decades of progress since Yukawa first developed a description of the force between nucleons in terms of meson exchange 1 , a full understanding of the strong interaction remains a major challenge in modern science. One remaining difficulty arises from the non-perturbative nature of the strong force, which leads to the phenomenon of quark confinement at distance scales on the order of the size of the proton. Here we show that in relativistic heavy-ion collisions, where quarks and gluons are set free over an extended volume, two species of produced vector (spin-1) mesons, namely φ and K * 0 , emerge with a surprising pattern of global spin alignment. In particular, the global spin alignment for φ is unexpectedly large, while that for K * 0 is consistent with zero. The observed spin-alignment pattern and magnitude for the φ cannot be explained by conventional mechanisms, while a model with strong force fields 2,3 accommodates the current data. This is the first time that the strong force field is experimentally supported as a key mechanism that leads to global spin alignment. We extract a quantity proportional to the intensity of the field of the strong force. Within the framework of the Standard Model, where the strong force is typically described in the quark and gluon language of Quantum Chromodynamics, the field being considered here is an effective proxy description. This is a qualitatively new class of measurement, which opens a new avenue for studying the behaviour of strong force fields via their imprint on spin alignment.

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Section: Reconstruction Of Event Planementioning

confidence: 91%

Pattern of Global Spin Alignment of $ϕ$ and $K^{*0}$ mesons in Heavy-Ion Collisions

Collaboration¹,

Abdallah²,

E.³

et al. 2022

Preprint

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“…Among these TMD FFs, we notice in particularly that the S LL dependent TMD FF D 1LL , which is responsible for the spin alignment of the produced vector meson, is decoupled from the quark polarization. This suggests that the vector meson spin alignment can also be observed in the unpolarized high-energy collisions [108][109][110]. Besides, D 1LL also survives the k ⊥ -integral.…”

Section: T(0)mentioning

confidence: 72%

“…It was thus first proposed in [63] that the vector meson spin alignment can also be observed in other high-energy collisions with unpolarized quarks fragmenting. Fitting to the experimental data from LEP, other work [108,109] extracted D 1LL (z) and made predictions for the spin alignment of high p T vector mesons in unpolarized pp collisions at RHIC and the LHC [109]. Furthermore, from the same mechanism, there will be a significant spin alignment for vector mesons produced in the unpolarized SIDIS.…”

Section: Vector Mesonsmentioning

confidence: 98%

Several Topics on Transverse Momentum-Dependent Fragmentation Functions

et al. 2023

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The hadronization of a high-energy parton is described by fragmentation functions which are introduced through QCD factorizations. While the hadronization mechanism per se remains uknown, fragmentation functions can still be investigated qualitatively and quantitatively. The qualitative study mainly concentrates on extracting genuine features based on the operator definition in quantum field theory. The quantitative research focuses on describing a variety of experimental data employing the fragmentation function given by the parameterizations or model calculations. With the foundation of the transverse-momentum-dependent factorization, the QCD evolution of leading twist transverse-momentum-dependent fragmentation functions has also been established. In addition, the universality of fragmentation functions has been proven, albeit model-dependently, so that it is possible to perform a global analysis of experimental data in different high-energy reactions. The collective efforts may eventually reveal important information hidden in the shadow of nonperturbative physics. This review covers the following topics: transverse-momentum-dependent factorization and the corresponding QCD evolution, spin-dependent fragmentation functions at leading and higher twists, several experimental measurements and corresponding phenomenological studies, and some model calculations.

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“…For example, tensor polarization related observables in electron-deuteron scattering experiments are utilized to probe the features of nuclear interaction [2][3][4][5]. In the context of the high energy e + e − and pp collisions, the measurement of vector meson's tensor polarization is employed for investigating the spin-dependent fragmentation functions and hence the hadronization mechanism in QCD [6,7]. Motivated by pioneering works [8][9][10][11], tensor polarization of vector meson produced in heavyion collisions (HIC), including K * , φ and J/Ψ have been explored at both RHIC and LHC via analyzing spin alignment observables δρ 00 [12][13][14][15][16], which is the deviation of the "00" components of the vector meson's spin density matrix from 1/3.…”

mentioning

confidence: 99%