Nuclear Theory·nucl-th

Monday·December 14, 2015

16 papers—9 primary·7 cross-listed

10
Effect of $Z_{b}$ states on $Υ (3 S) \to Υ (1 S) π π$ decays
Yun-Hua Chen🇩🇪 · Johanna T. Daub🇩🇪 · Feng-Kun Guo🇨🇳 · Bastian Kubis🇩🇪 · Ulf-G. Meißner🇩🇪 · Bing-Song Zou🇨🇳
Within the framework of dispersion theory, we analyze the dipion transitions between the lightest $Υ$ states, $Υ (n S) \to Υ (m S) π π$ with $m < n \leq 3$ . In particular, we consider the possible effects of two intermediate bottomoniumlike exotic states $Z_{b} (10610)$ and $Z_{b} (10650)$ . The $π π$ rescattering effects are taken into account in a model-independent way using dispersion theory. We confirm that matching the dispersive representation to the leading chiral amplitude alone cannot reproduce the peculiar two-peak $π π$ mass spectrum of the decay $Υ (3 S) \to Υ (1 S) π π$ . The existence of the bottomoniumlike $Z_{b}$ states can naturally explain this anomaly. We also point out the necessity of a proper extraction of the coupling strengths for the $Z_{b}$ states to $Υ (n S) π$ , which is only possible if a Flatté-like parametrization is used in the data analysis for the $Z_{b}$ states.
↳ hep-phhep-exnucl-thPRD(2016)·60 citations
11
Linking neutrino oscillations to the nucleosynthesis of elements
Meng-Ru Wu🇩🇪 · Gabriel Martinez-Pinedo🇩🇪 · Yong-Zhong Qian🇺🇸
Neutrino interactions with matter play an important role in determining the nucleosynthesis outcome in explosive astrophysical environments such as core-collapse supernovae or mergers of compact objects. In this article, we first discuss our recent work on the importance of studying the time evolution of collective neutrino oscillations among active flavors in determining their effects on nucleosynthesis. We then consider the possible active-sterile neutrino mixing and demonstrate the need of a consistent approach to evolve neutrino flavor oscillations, matter composition, and the hydrodynamics when flavor oscillations can happen very deep inside the supernovae.
↳ astro-ph.HEhep-phnucl-thEPJ Web Conf.(2016)·9 citations
12
$Z_{c} (3900)$ : what has been really seen?
Miguel Albaladejo🇪🇸 · Feng-Kun Guo🇨🇳 · Carlos Hidalgo-Duque🇪🇸 · Juan Nieves🇪🇸
The $Z_{c}^{\pm} (3900) / Z_{c}^{\pm} (3885)$ resonant structure has been experimentally observed in the $Y (4260) \to J / ψ π π$ and $Y (4260) \to D ˉ^{*} D π$ decays. This structure is intriguing since it is a prominent candidate of an exotic hadron. Yet, its nature is unclear so far. In this work, we simultaneously describe the $D ˉ^{*} D$ and $J / ψ π$ invariant mass distributions in which the $Z_{c}$ peak is seen using amplitudes with exact unitarity. Two different scenarios are statistically acceptable, where the origin of the $Z_{c}$ state is different. They correspond to using energy dependent or independent $D ˉ^{*} D$ $S$ -wave interaction. In the first one, the $Z_{c}$ peak is due to a resonance with a mass around the $D D ˉ^{*}$ threshold. In the second one, the $Z_{c}$ peak is produced by a virtual state which must have a hadronic molecular nature. In both cases the two observations, $Z_{c}^{\pm} (3900)$ and $Z_{c}^{\pm} (3885)$ , are shown to have the same common origin, and a $D ˉ^{*} D$ bound state solution is not allowed. Precise measurements of the line shapes around the $D D ˉ^{*}$ threshold are called for in order to understand the nature of this state.
↳ hep-phnucl-thPLB(2016)·115 citations
13
Scattering asymptotic conditions in Euclidean relativistic quantum theory
Gordon Aiello🇺🇸 · Wayne Polyzou🇺🇸
We discuss the formulation of the scattering asymptotic condition as a strong limit in Euclidean quantum theories satisfying the Osterwalder-Schrader axioms. When used with the invariance principle this provides a constructive method to compute scattering observables directly in the Euclidean formulation of the theory, without an explicit analytic continuation.
↳ hep-thhep-latnucl-thPRD(2016)·8 citations
14
The Phase Diagram of QC2D from Functional Methods
Naseemuddin Khan🇩🇪 · Jan M. Pawlowski🇩🇪 · Fabian Rennecke🇩🇪 · Michael M. Scherer🇩🇪
We study the phase diagram of two-color Quantum Chromodynamics at finite temperature and chemical potential. This is done within an effective low-energy description in terms of quarks, mesons and diquarks. Quantum, thermal and density fluctuations are taken into account with the functional renormalisation group approach. In particular, we establish the phenomenon of pre-condensation, affecting the location of the phase boundary to Bose-Einstein condensation. We also discuss the Silver Blaze property in the context of the functional renormalisation group.
↳ hep-phhep-thnucl-th64 citations
15
Heavy Quark Diffusion in Strong Magnetic Fields at Weak Coupling and Implications for Elliptic Flow
Kenji Fukushima🇯🇵 · Koichi Hattori🇯🇵 · Ho-Ung Yee🇺🇸 · Yi Yin🇺🇸
We compute the momentum diffusion coefficients of heavy quarks, $κ_{∥}$ and $κ_{⊥}$ , in a strong magnetic field $B$ along the directions parallel and perpendicular to $B$ , respectively, at the leading order in QCD coupling constant $α_{s}$ . We consider a regime relevant for the relativistic heavy ion collisions, $α_{s} e B ≪ T^{2} ≪ e B$ , so that thermal excitations of light quarks are restricted to the lowest Landau level (LLL) states. In the vanishing light-quark mass limit, we find $κ_{⊥}^{LO} \propto α_{s}^{2} T e B$ in the leading order that arises from screened Coulomb scatterings with (1+1)-dimensional LLL quarks, while $κ_{∥}$ gets no contribution from the scatterings with LLL quarks due to kinematic restrictions. We show that the first non-zero leading order contributions to $κ_{∥}^{LO}$ come from the two separate effects: 1) the screened Coulomb scatterings with thermal gluons, and 2) a finite light-quark mass $m_{q}$ . The former leads to $κ_{∥}^{LO, gluon} \propto α_{s}^{2} T^{3}$ and the latter to $κ_{∥}^{LO, massive} \propto α_{s} (α_{s} e B)^{1/2} m_{q}^{2}$ . Based on our results, we propose a new scenario for the large value of heavy-quark elliptic flow observed in RHIC and LHC. Namely, when $κ_{⊥} ≫ κ_{∥}$ , an anisotropy in drag forces gives rise to a sizable amount of the heavy-quark elliptic flow even if heavy quarks do not fully belong to an ellipsoidally expanding background fluid.
↳ hep-phnucl-thPRD(2016)·145 citations
16
Rôle of the pion electromagnetic form factor in the $Δ (1232) \to γ^{*} N$ timelike transition
G. Ramalho🇧🇷 · M.T Pena🇵🇹 · J. Weil🇩🇪 · H. van Hees🇩🇪 · U. Mosel🇩🇪
The $Δ (1232) \to γ^{*} N$ magnetic dipole form factor ( $G_{M}^{*}$ ) is described here within a new covariant model that combines the valence quark core together with the pion cloud contributions. The pion cloud term is parameterized by two terms: one connected to the pion electromagnetic form factor, the other to the photon interaction with intermediate baryon states. The model can be used in studies of pp and heavy ion collisions. In the timelike region this new model improves the results obtained with a constant form factor model fixed at its value at zero momentum transfer. At the same time, and in contrast to the Iachello model, this new model predicts a peak for the transition form factor at the expected position, i.e. at the $ρ$ mass pole. We calculate the decay of the $Δ \to γ N$ transition, the Dalitz decay ( $Δ \to e^{+} e^{-} N$ ), and the $Δ$ mass distribution function. The impact of the model on dilepton spectra in pp collisions is also discussed.
↳ hep-phhep-exhep-latnucl-ex+1PRD(2016)·51 citations

Affiliations

first authorsco-authorsvia INSPIRE

Effect of Zb​ states on Υ(3S)→Υ(1S)ππ decays

Linking neutrino oscillations to the nucleosynthesis of elements

Zc​(3900): what has been really seen?

Scattering asymptotic conditions in Euclidean relativistic quantum theory

The Phase Diagram of QC2D from Functional Methods

Heavy Quark Diffusion in Strong Magnetic Fields at Weak Coupling and Implications for Elliptic Flow

Rôle of the pion electromagnetic form factor in the Δ(1232)→γ∗N timelike transition

Affiliations

Effect of $Z_{b}$ states on $Υ (3 S) \to Υ (1 S) π π$ decays

$Z_{c} (3900)$ : what has been really seen?

Rôle of the pion electromagnetic form factor in the $Δ (1232) \to γ^{*} N$ timelike transition