Nuclear Theory·nucl-th

Wednesday·March 18, 2020

10 papers—5 primary·5 cross-listed

06
[Submitted on 16 Mar 2020] (cross-list from hep-th)
Hydrodynamic attractors in phase space
Michal P. Heller🇩🇪 · Ro Jefferson🇩🇪 · Michał Spaliński🇵🇱 · Viktor Svensson🇩🇪
Hydrodynamic attractors have recently gained prominence in the context of early stages of ultra-relativistic heavy-ion collisions at the RHIC and LHC. We critically examine the existing ideas on this subject from a phase space point of view. In this picture the hydrodynamic attractor can be seen as a special case of the more general phenomenon of dynamical dimensionality reduction of phase space regions. We quantify this using Principal Component Analysis. Furthermore, we adapt the well known slow-roll approximation to this setting. These techniques generalize easily to higher dimensional phase spaces, which we illustrate by a preliminary analysis of a dataset describing the evolution of a 5-dimensional manifold of initial conditions immersed in a 16-dimensional representation of the phase space of the Boltzmann kinetic equation in the relaxation time approximation.
Comments:
9 pages, 5 figures. Matches published version and includes new supplemental material on dimensionality reduction in kinetic theory
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2003.07368 [pdf]
PRL(2020)·47 citations
07
[Submitted on 16 Mar 2020] (cross-list from hep-ph)
Predictive power of transverse-momentum-dependent distributions
Manvir Grewal🇺🇸 · Zhong-Bo Kang🇺🇸 · Jian-Wei Qiu🇺🇸 · Andrea Signori🇮🇹
We investigate the predictive power of transverse-momentum-dependent (TMD) distributions as a function of the light-cone momentum fraction $x$ and the hard scale $Q$ defined by the process. We apply the saddle point approximation to the unpolarized quark and gluon transverse momentum distributions and evaluate the position of the saddle point as a function of the kinematics. We determine quantitatively that the predictive power for an unpolarized transverse momentum distribution is maximal in the large- $Q$ and small- $x$ region. For cross sections the predictive power of the TMD factorization formalism is generally enhanced by considering the convolution of two distributions, and we explicitly consider the case of $Z$ and $H^{0}$ boson production. In the kinematic regions where the predictive power is not maximal, the distributions are sensitive to the non-perturbative hadron structure. Thus, these regions are critical for investigating hadron tomography in a three-dimensional momentum space.
Comments:
25 pages - published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2003.07453 [pdf]
PRD(2020)·29 citations
08
[Submitted on 17 Mar 2020] (cross-list from hep-ph)
Molecular picture for the $Ω (2012)$ revisited
Natsumi Ikeno🇯🇵 · Genaro Toledo🇪🇸 · Eulogio Oset🇪🇸
We conduct a study of the interaction of the $K ˉ Ξ^{*}$ , $η Ω$ ( $s$ -wave) and $K ˉ Ξ$ ( $d$ -wave) channels within a coupled channel unitary approach where the transition potential between the $K ˉ Ξ^{*}$ and $η Ω$ channels is obtained from chiral Lagrangians. The transition potential between $K ˉ Ξ^{*}$ , $η Ω$ and $K ˉ Ξ$ is taken in terms of free parameters, which together with a cut off to regularize the meson-baryon loops are fitted to the $Ω (2012)$ data. We find that all data including the recent Belle experiment on $Γ_{Ω^{*} \to π K ˉ Ξ} / Γ_{Ω^{*} \to K ˉ Ξ}$ , are compatible with the molecular picture stemming from meson baryon interaction of these channels.
Comments:
19 pages, 4 figures, 4 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2003.07580 [pdf]
PRD(2020)·44 citations
09
[Submitted on 17 Mar 2020] (cross-list from hep-ph)
Revisiting the $Ω (2012)$ as a hadronic molecule and its strong decays
Jun-Xu Lu🇨🇳 · Chun-Hua Zeng🇨🇳 · En Wang🇨🇳 · Ju-Jun Xie🇨🇳 · Li-Sheng Geng🇨🇳
Recently, the Belle collaboration measured the ratios of the branching fractions of the newly observed $Ω (2012)$ excited state. They did not observe significant signals for the $Ω (2012) \to K ˉ Ξ^{*} (1530) \to K ˉ π Ξ$ decay, and reported an upper limit for the ratio of the three body decay to the two body decay mode of $Ω (2012) \to K ˉ Ξ$ . In this work, we revisit the newly observed $Ω (2012)$ from the molecular perspective where this resonance appears to be a dynamically generated state with spin-parity $3/ 2^{-}$ from the coupled channels interactions of the $K ˉ Ξ^{*} (1530)$ and $η Ω$ in $s$ -wave and $K ˉ Ξ$ in $d$ -wave. With the model parameters for the $d$ -wave interaction, we show that the ratio of these decay fractions reported recently by the Belle collaboration can be easily accommodated.
Comments:
Published version. Published in Eur.\ Phys.\ J.\ C {\bf 80}, 361 (2020)
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2003.07588 [pdf]
EPJC(2020)·38 citations
10
[Submitted on 17 Mar 2020] (cross-list from physics.atm-clus)
Derivation of K-matrix reaction theory in a discrete basis formalism
Y. Alhassid · G.F. Bertsch · P. Fanto
The usual derivations of the S and K matrices for two-particle reactions proceed through the Lippmann-Schwinger equation with formal definitions of the incoming and outgoing scattering states. Here we present an alternative derivation that is carried out completely in the Hamiltonian representation, using a discrete basis of configurations for the scattering channels as well as the quasi-bound configurations of the combined fragments. We use matrix algebra to derive an explicit expression for the K matrix in terms of the Hamiltonian of the internal states of the compound system and the coupling between the channels and the internal states. The formula for the K matrix includes explicitly a real dispersive shift matrix to the internal Hamiltonian that is easily computed in the formalism. That expression is applied to derive the usual form of the S matrix as a sum over poles in the complex energy plane. Some extensions and limitations of the discrete-basis Hamiltonian formalism are discussed in the concluding remarks and in the Appendix.
Subjects:
physics.atm-clus (physics.atm-clus); Nuclear Theory (nucl-th)
arXiv:
2003.07843 [pdf]
Annals Phys.(2020)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE

Hydrodynamic attractors in phase space

Predictive power of transverse-momentum-dependent distributions

Molecular picture for the Ω(2012) revisited

Revisiting the Ω(2012) as a hadronic molecule and its strong decays

Derivation of K-matrix reaction theory in a discrete basis formalism

Affiliations

Molecular picture for the $Ω (2012)$ revisited

Revisiting the $Ω (2012)$ as a hadronic molecule and its strong decays