Nuclear Theory·nucl-th

Monday·August 26, 2019

7 papers—1 primary·6 cross-listed

01
Lessons from fitting the lowest order energy independent chiral based $K ˉ N$ potential to experimental data
János Révai
It is shown, that fitting parameters of a $K ˉ N$ interaction model to different sets of experimental data can lead to physical conclusions which might provide a deeper insight into the physics of this multichannel system. The available experimental data are divided into three parts: the "classical" set consisting of the low-energy $K^{-} p$ cross sections and the threshold branching ratios, the SIDDHARTA $1 s$ level shift in kaonic hydrogen and the CLAS photoproduction data. We have fitted the parameters of the potential to different combinations of these data. We found, that the two poles corresponding to the $I = 0$ nuclear quasi-bound state ( $\Lam$ ) and to the $K^{-} p$ $1 s$ atomic level seem to resist to their simultaneous reproduction at the right place, though a more or less satisfactory compromise can be achieved. Potentials with the $\Lam$ pole pinned down close to the PDG value fail to reproduce the classical two-body data with an acceptable accuracy. We also added comments on two papers criticizing the potential used in the fits.
nucl-thFew Body Syst.(2020)·5 citations
02
Hydro+ in Action: Understanding the Out-of-Equilibrium Dynamics Near a Critical Point in the QCD Phase Diagram
Krishna Rajagopal🇺🇸 · Gregory Ridgway🇺🇸 · Ryan Weller🇺🇸 · Yi Yin🇺🇸
Upcoming experimental programs will look for signatures of a possible critical point in the QCD phase diagram in fluctuation observables. To understand and predict these signatures, one must account for the fact that the dynamics of any critical fluctuations must be out-of-equilibrium: because of critical slowing down, the fluctuations cannot stay in equilibrium as the droplet of QGP produced in a collision expands and cools. Furthermore, their out-of-equilibrium dynamics must also influence the hydrodynamic evolution of the cooling droplet. The recently developed Hydro+ formalism allows for a consistent description of both the hydrodynamics and the out-of-equilibrium fluctuations, including the feedback between them. We shall explicitly demonstrate how this works, setting up a Hydro+ simulation in a simplified setting: a rapidity-independent fireball undergoing radial flow with an equation of state in which we imagine a critical point close to the $μ_{B} = 0$ axis of the phase diagram. Within this setup, we show that we can quantitatively capture non-equilibrium phenomena, including critical fluctuations over a range of scales and memory effects. Furthermore, we illustrate the interplay between the dynamics of the fluctuations and the hydrodynamic flow of the fireball: as the fluid cools and flows, the dynamical fluctuations lag relative to how they would evolve if they stayed in equilibrium; there is then a backreaction on the flow itself due to the out-of-equilibrium fluctuations; and, in addition, the radial flow transports fluctuations outwards by advection. Within our model, we find that the backreaction from the out-of-equilibrium fluctuations does not yield dramatically large effects in the hydrodynamic variables. Further work will be needed in order to check this quantitative conclusion in other settings but, if it persists, this will considerably simplify future modelling.
↳ hep-phnucl-thPRD(2020)·81 citations
03
Neutral Current Neutrino-Nucleus Scattering. Theory
Carlotta Giusti🇮🇹 · Martin V. Ivanov🇧🇬
The treatment of nuclear effects in neutrino-nucleus interactions is one of the main sources of systematic uncertainty for the analysis and interpretation of data of neutrino oscillation experiments. Neutrinos interact with nuclei via charged or neutral currents and both cases must be studied to obtain a complete information. We give an overview of the theoretical work that has been done to describe nuclear effects in neutral-current neutrin onucleus scattering in the kinematic region ranging between beam energies of a few hundreds MeV to a few GeV, which is typical of most ongoing and future accelerator-based neutrino experiments, and where quasielastic scattering is the main interaction mechanism. We review the current status and challenges of the theoretical models, the role and relevance of the contributions of different nuclear effects, and the present status of the comparison between the numerical predictions of the models as well as the available experimental data. We discuss also the sensitivity to the strange form factors of the nucleon and the methods and observables that can allow one to obtain evidence for a possible strange quark contribution from measurements of neutrino and antineutrino-nucleus scattering.
↳ hep-phnucl-exnucl-thJ.Phys.G(2020)·18 citations
04
Nambu-Jona-Lasinio model in a sphere
Zheng Zhang🇨🇳 · Chao Shi🇨🇳 · Hongshi Zong🇨🇳
We study the chiral phase transition of the two flavor Nambu-Jona-Lasinio (NJL) model in a sphere with the MIT boundary condition. We find that the MIT boundary condition results in much stronger finite size effects than the antiperiodic boundary condition. Our work may be helpful to study the finite size effects in heavy-ion collision in a more realistic way.
↳ hep-phnucl-thPRD(2020)·14 citations
05
Heavy hadronic molecules with pion exchange and quark core couplings: a guide for practitioners
Yasuhiro Yamaguchi🇯🇵 · Atsushi Hosaka🇯🇵 · Sachiko Takeuchi🇯🇵 · Makoto Takizawa🇯🇵
We discuss selected and important features of hadronic molecules as one of promising forms of exotic hadrons near thresholds. Using examples of $D D ˉ^{*}$ systems such as $X (3872)$ and $Z_{c}$ , emphasis is put on the roles of the one pion exchange interaction between them and their coupling to intrinsic quark states. Thus hadronic molecules emerge as admixtures of the dominant long-range hadron structure and short-range quark structure. For the pion exchange interaction, properties of the tensor force are analyzed in detail. More coupled channels supply more attractions, and heavier constituents suppress kinetic energies, providing more chances to form hadronic molecules of heavy hadrons. Throughout this article, we show details of basic ideas and methods.
↳ hep-phnucl-thJ.Phys.G(2020)·110 citations
06
Fractals, non-extensive statistics and QCD
Airton Deppman🇧🇷 · Eugenio Megias🇪🇸 · Debora P. Menezes🇧🇷
In this work we analyse how scaling properties of Yang-Mills field theory manifest as self-similarity of truncated n-point functions by scale evolution. The presence of such structures, which actually behaves as fractals, allow for recurrent non-perturbative calculation of any vertex. Some general properties are indeed independent of the perturbative order, what simplifies the non-perturbative calculations. We show that for sufficiently high perturbative orders a statistical approach can be used, the non extensive statistics is obtained, and the Tsallis index, $q$ , is deduced in terms of the field theory parameters. The results are applied to QCD in the one-loop approximation, where $q$ can be calculated, resulting in a good agreement with the value obtained experimentally. We discuss how this approach allows to understand some intriguing experimental findings in high energy collisions, as the behavior of multiplicity against collision energy, long-tail distributions and the fractal dimension observed in intermittency analysis.
↳ hep-thhep-phnucl-thPRD(2020)·49 citations
07
Semirelativistic Bound States: (Pseudo-) Spinless-Salpeter Approaches Reassessed
Wolfgang Lucha🇦🇹
Relativistic quantum field theory offers, in form of the homogeneous Bethe-Salpeter framework, a (Poincaré-covariant) description of bound states in terms of their underlying theory's fundamental degrees of freedom. In view of the intrinsic complexity of this approach, simplifications have been sought and abundantly found. The significance of these latter approximations may be estimated by comparing their predictions with (easily inferable) rigorous constraints on the bound-state spectra, such as existence, number and location of discrete eigenstates. The application of these techniques to selected proposed bound-state equations is exemplified for a large class of generalizations of the Hellmann potential frequently employed in several areas of science such as physics and chemistry.
↳ hep-phnucl-thPoS(2020)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE

Lessons from fitting the lowest order energy independent chiral based KˉN potential to experimental data

Hydro+ in Action: Understanding the Out-of-Equilibrium Dynamics Near a Critical Point in the QCD Phase Diagram

Neutral Current Neutrino-Nucleus Scattering. Theory

Nambu-Jona-Lasinio model in a sphere

Heavy hadronic molecules with pion exchange and quark core couplings: a guide for practitioners

Fractals, non-extensive statistics and QCD

Semirelativistic Bound States: (Pseudo-) Spinless-Salpeter Approaches Reassessed

Affiliations

Lessons from fitting the lowest order energy independent chiral based $K ˉ N$ potential to experimental data