Nuclear Theory·nucl-th

Tuesday·February 15, 2022

11 papers—6 primary·5 cross-listed

07
[Submitted on 11 Feb 2022] (cross-list from hep-ph)
A dispersive analysis of $η^{'} \to π^{+} π^{-} γ$ and $η^{'} \to ℓ^{+} ℓ^{-} γ$
Simon Holz🇩🇪 · Christoph Hanhart🇩🇪 · Martin Hoferichter🇨🇭 · Bastian Kubis🇩🇪
We present a dispersive representation of the $η^{'}$ transition form factor that allows one to account, in a consistent way, for the effects of $ρ$ - $ω$ mixing in both the isoscalar and the isovector contributions. Using this formalism, we analyze recent data on $η^{'} \to π^{+} π^{-} γ$ to constrain the isovector part of the form factor, individually and in combination with data for the pion vector form factor. As a first application, we use our results, in combination with the most recent input for the isoscalar part of the form factor, to predict the corresponding spectrum of $η^{'} \to ℓ^{+} ℓ^{-} γ$ , in particular we find the slope parameter $b_{η^{'}} = 1.431 (23) GeV^{- 2}$ . With forthcoming data on the latter process, our results establish the necessary framework to improve the evaluation of the $η^{'}$ -pole contribution to the anomalous magnetic moment of the muon using experimental input from both $η^{'}$ decay channels.
Comments:
18 pages, 2 figures, tension in $ϵ_{ρ ω}$ resolved by including higher orders in $e^{2}$
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2202.05846 [pdf]
EPJC(2022)·61 citations
08
[Submitted on 12 Feb 2022] (cross-list from hep-ph)
Production of $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ mesons in hadronic matter
Li-Yuan Li🇨🇳 · Xiao-Ming Xu🇨🇳 · H. J. Weber🇺🇸
We present the first study of production of $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ mesons in hadronic matter. Quark interchange between two colliding charmed mesons leads to the production of the three mesons. We calculate unpolarized cross sections for the reactions, $D D ˉ \to ρR$ , $D D ˉ^{*} \to π R$ , $D D ˉ^{*} \to ρR$ , $D^{*} D ˉ \to π R$ , $D^{*} D ˉ \to ρR$ , $D^{*} D ˉ^{*} \to π R$ , and $D^{*} D ˉ^{*} \to ρR$ , where $R$ stands for $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ . In the temperature region covering hadronic matter the peak cross sections of producing $ψ (4040)$ are similar to or larger than the ones of producing $ψ (4415)$ , and the latter are generally larger than those of producing $ψ (4160)$ . With the cross sections we establish new master rate equations for $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ . The equations are solved for central Pb-Pb collisions at $s_{N N} = 5.02$ TeV at the Large Hadron Collider. Solutions of the equations show that the $ψ (4040)$ number density at kinetic freeze-out of hadronic matter is larger than the $ψ (4415)$ number density which is larger than the $ψ (4160)$ number density.
Comments:
50 pages, 21 figures, 5 tables; discussions added
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2202.05999 [pdf]
PRD(2022)·2 citations
09
[Submitted on 12 Feb 2022] (cross-list from hep-ph)
Artificial Dynamical Effects in Quantum Field Theory
S. J. Brodsky🇺🇸 · A. Deur🇺🇸 · C. D. Roberts🇨🇳
In Newtonian mechanics, inertial pseudoforces - or fictitious forces - appear in systems studied in non-Galilean reference frames; e.g., a centrifugal force seems to arise if the dynamics is analyzed in a rotating reference frame. The equivalent of Galilean invariance for relativistic kinematics is Poincaré invariance; analogous artificial effects may arise in relativistic quantum field theory (QFT) if a system is studied in a framework violating Poincaré invariance. We highlight how such issues complicate the traditional canonical quantization of QFTs and can lead to a subjective description of natural phenomena. In fact, if the system involves the strong interaction, obtaining objective results can become an intractable problem using canonical quantization because the pseudoforces are essentially nonperturbative. In contrast, the treatment of the same problem using light-front (LF) quantization is free of spurious pseudoeffects because Poincaré invariance is manifest; thus the treatment of strong interaction problems becomes simpler. These statements are illustrated using several examples: the Gerasimov-Drell-Hearn (GDH) relation, a fundamental feature of QFT; the absence of any measurable impact of Lorentz contraction in high-energy collisions; and the fictitious character of vacuum fluctuation contributions to the cosmological constant.
Comments:
21 page, 4 Figure. A version of this document, amended during the peer consultation process, has been accepted for publication in Nature Reviews Physics
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2202.06051 [pdf]
Nature Rev.Phys.(2022)·27 citations
10
[Submitted on 14 Feb 2022] (cross-list from hep-ph)
Doubly heavy tetraquarks in a chiral-diquark picture
Yonghee Kim🇯🇵 · Makoto Oka🇯🇵 · Kei Suzuki🇯🇵
Energy spectrum of doubly heavy tetraquarks, $T_{QQ}$ ( $QQ q ˉ q ˉ$ with $Q = c, b$ and $q = u, d, s$ ), is studied in the potential chiral-diquark model. Using the chiral effective theory of diquarks and the quark-diquark-based potential model, the $T_{bb}$ , $T_{cc}$ , and $T_{c b}$ tetraquarks are described as a three-body system composed of two heavy quarks and an antidiquark. We find several $T_{bb}$ bound states, while no $T_{cc}$ and $T_{c b}$ (deep) bound state is seen. We also study the change of the $T_{QQ}$ tetraquark masses under restoration of chiral symmetry.
Comments:
16 pages, 14 Figures, 10 Tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2202.06520 [pdf]
PRD(2022)·54 citations
11
[Submitted on 14 Feb 2022] (cross-list from hep-ph)
Energy dependence of the proton geometry in exclusive vector meson production
Arjun Kumar🇮🇳 · Tobias Toll🇮🇳
The gluon radius of the proton is expected to increase at small gluon momentum fractions $x$ , an effect which has hitherto not been considered in the dipole model framework. We investigate the energy dependence of exclusive $J / ψ$ , $ϕ$ , and $ρ$ production by introducing three models for $x$ dependence of the gluon thickness function. We allow the transverse width of the proton to increase as $x$ decreases, using novel parametrisations in the spherical proton and the hotspot model. We compare these with a model where the number of hotspots increases as $x$ decreases and confront the models with HERA data. The models exhibit clear differences in the slope of the $t$ -spectra and in the cross section ratios between coherent and incoherent events. Comparisons to $t$ -slopes and $W_{γ p}$ measurements show a preference for models where the proton's size increases as $x$ decreases.
Comments:
11 pages,7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2202.06631 [pdf]
PRD(2022)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE

A dispersive analysis of η′→π+π−γ and η′→ℓ+ℓ−γ

Production of ψ(4040), ψ(4160), and ψ(4415) mesons in hadronic matter

Artificial Dynamical Effects in Quantum Field Theory

Doubly heavy tetraquarks in a chiral-diquark picture

Energy dependence of the proton geometry in exclusive vector meson production

Affiliations

A dispersive analysis of $η^{'} \to π^{+} π^{-} γ$ and $η^{'} \to ℓ^{+} ℓ^{-} γ$

Production of $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ mesons in hadronic matter