Nuclear Theory·nucl-th

Monday·June 26, 2017

10 papers—4 primary·6 cross-listed

05
A determination of the fragmentation functions of pions, kaons, and protons with faithful uncertainties
Valerio Bertone🇳🇱 · Stefano Carrazza🇨🇭 · Nathan P. Hartland🇳🇱 · Emanuele R. Nocera🇬🇧 · Juan Rojo🇳🇱
We present NNFF1.0, a new determination of the fragmentation functions (FFs) of charged pions, charged kaons, and protons/antiprotons from an analysis of single-inclusive hadron production data in electron-positron annihilation. This determination, performed at leading, next-to-leading, and next-to-next-to-leading order in perturbative QCD, is based on the NNPDF methodology, a fitting framework designed to provide a statistically sound representation of FF uncertainties and to minimise any procedural bias. We discuss novel aspects of the methodology used in this analysis, namely an optimised parametrisation of FFs and a more efficient $χ^{2}$ minimisation strategy, and validate the FF fitting procedure by means of closure tests. We then present the NNFF1.0 sets, and discuss their fit quality, their perturbative convergence, and their stability upon variations of the kinematic cuts and the fitted dataset. We find that the systematic inclusion of higher-order QCD corrections significantly improves the description of the data, especially in the small- $z$ region. We compare the NNFF1.0 sets to other recent sets of FFs, finding in general a reasonable agreement, but also important differences. Together with existing sets of unpolarised and polarised parton distribution functions (PDFs), FFs and PDFs are now available from a common fitting framework for the first time.
↳ hep-phhep-exnucl-exnucl-thEPJC(2017)·214 citations
06
Effect of collisions on neutrino flavor inhomogeneity in a dense neutrino gas
Vincenzo Cirigliano🇺🇸 · Mark W. Paris🇺🇸 · Shashank Shalgar🇺🇸
We investigate the stability, with respect to spatial inhomogeneity, of a two-dimensional dense neutrino gas. The system exhibits growth of seed inhomogeneity due to nonlinear coherent neutrino self-interactions. In the absence of incoherent collisional effects, we observe a dependence of this instability growth rate on the neutrino mass spectrum: the normal neutrino mass hierarchy exhibits spatial instability over a larger range of neutrino number density compared to that of the inverted case. We further consider the effect of elastic incoherent collisions of the neutrinos with a static background of heavy, nucleon-like scatterers. At small scales, the growth of flavor instability can be suppressed by collisions. At large length scales we find, perhaps surprisingly, that for inverted neutrino mass hierarchy incoherent collisions fail to suppress flavor instabilities, independent of the coupling strength.
↳ hep-phastro-ph.COnucl-thPLB(2017)·21 citations
07
The Tetraquark Candidate Zc(3900) from Dynamical Lattice QCD Simulations
Yoichi Ikeda (1 and 2, for HAL QCD Collaboration) · ((1) RCNP, Osaka Univ. and (2) Nishina Center, RIKEN)
The structure of the tetraquark candidate $Z_{c} (3900)$ , which was experimentally reported in $e^{+} e^{-}$ collisions, is studied by the s-wave meson-meson coupled-channel scattering on the lattice. The s-wave interactions among the $π J / ψ$ , $ρ η_{c}$ and $D D ˉ^{*}$ channels are derived from (2+1)-flavor dynamical QCD simulations at $m_{π} = 410$ -- $700$ MeV. It is found that the interactions are dominated by the off-diagonal $π J / ψ$ - $D D ˉ^{*}$ and $ρ η_{c}$ - $D D ˉ^{*}$ couplings. With the interactions obtained, the s-wave two-body amplitudes and the pole position in the $π J / ψ$ - $ρ η_{c}$ - $D D ˉ^{*}$ coupled-channel scattering are calculated. The results show that the $Z_{c} (3900)$ is not a conventional resonance but a threshold cusp. A semiphenomenological analysis with the coupled-channel interaction to the experimentally observed decay mode is also presented to confirm the conclusion.
↳ hep-lathep-phnucl-thJ.Phys.G(2018)·46 citations
08
Regge phenomenology in $π^{0}$ and $η$ photoproduction
V. L. Kashevarov🇩🇪 · M. Ostrick🇩🇪 · L. Tiator🇩🇪
The $γ N \to π^{0} N$ and $γ N \to η N$ reactions at photon beam energies above 4 GeV are investigated within Regge models. The models include $t$ -channel exchanges of vector ( $ρ$ and $ω$ ) and axial vector ( $b_{1}$ and $h_{1}$ ) mesons. Moreover, Regge cuts of $ρ P$ , $ρ f_{2}$ , $ω P$ , and $ω f_{2}$ are investigated. A good description of differential cross sections and polarization observables at photon beam energies from 4 to 15 GeV can be achieved.
↳ hep-phnucl-exnucl-thPRC(2017)·27 citations
09
Three-particle quantization condition in a finite volume: 1. The role of the three-particle force
H.-W. Hammer🇩🇪 · J.-Y. Pang🇩🇪 · A. Rusetsky🇩🇪
Using non-relativistic effective Lagrangians in the particle-dimer picture, we rederive the expression for the energy shift of a loosely bound three-particle bound state of identical bosons in the unitary limit. The effective field theory formalism allows us to investigate the role of the three-particle force, which has not been taken into account in the earlier treatment of the problem. Moreover, we are able to relax the requirement of the unitary limit of infinite scattering length and demonstrate a smooth transition from the weakly bound three-particle state to a two-particle bound state of a particle and a deeply bound dimer.
↳ hep-lathep-phnucl-thJHEP(2017)·186 citations
10
Finite size effect of hadronic matter on its transport coefficients
Subhasis Samanta🇮🇳 · Sabyasachi Ghosh🇮🇳 · Bedangadas Mohanty🇮🇳
We have theoretically investigated the finite system size effect of hadronic matter on its transport coefficients like shear viscosity, bulk viscosity, and electrical conductivity. We have used a Hadron Resonance Gas (HRG) model to calculate the thermodynamical quantities like entropy density, speed of sound and also the above transport coefficients. All these quantities are found to be sensitive to finite system size effects of hadronic matter. The effect of finite system size is found to be more when the system is at low temperatures and gets reduced at high temperatures. Owing to the intimate linking between system size and centrality, we have presented the centrality dependence of transport coefficients. We have also explored to link of our results with the macroscopic picture of hydrodynamical evolution.
↳ hep-phnucl-thJ.Phys.G(2018)·28 citations

Affiliations

first authorsco-authorsvia INSPIRE

A determination of the fragmentation functions of pions, kaons, and protons with faithful uncertainties

Effect of collisions on neutrino flavor inhomogeneity in a dense neutrino gas

The Tetraquark Candidate Zc(3900) from Dynamical Lattice QCD Simulations

Regge phenomenology in π0 and η photoproduction

Three-particle quantization condition in a finite volume: 1. The role of the three-particle force

Finite size effect of hadronic matter on its transport coefficients

Affiliations

Regge phenomenology in $π^{0}$ and $η$ photoproduction