Nuclear Theory·nucl-th

Friday·April 21, 2017

12 papers—6 primary·6 cross-listed

07
Simulating chiral magnetic effect and anomalous transport phenomena in the pre-equilibrium stages of heavy-ion collisions
Mark Mace🇺🇸 · Niklas Mueller🇩🇪 · Soeren Schlichting🇺🇸 · Sayantan Sharma🇺🇸
We present a first principles approach to study the Chiral Magnetic Effect during the pre-equilibrium stage of a heavy-ion collision. We discuss the dynamics of the Chiral Magnetic Effect and Chiral Magnetic Wave based on real-time lattice simulations with dynamical (Wilson and Overlap) fermions simultaneously coupled to color and electromagnetic fields. While for light quarks we observe a dissipation-less transport of charges as in anomalous hydrodynamics, we demonstrate that for heavier quarks the effects of explicit chiral symmetry breaking lead to a significant reduction of the associated currents.
↳ hep-lathep-phnucl-thNPA(2017)·6 citations
08
Physics with ions at the Future Circular Collider
David d'Enterria🇨🇭 · L. Apolinario🇨🇭 · N. Armesto🇨🇭 · A. Dainese🇨🇭 · J. Jowett🇨🇭 · J.P. Lansberg🇨🇭 · S. Masciocchi🇨🇭 · G. Milhano🇨🇭 · C. Roland🇨🇭 · C.A. Salgado🇨🇭 · M. Schaumann🇨🇭 · M. van Leeuwen🇨🇭 · U.A. Wiedemann🇨🇭
The unique physics opportunities accessible with nuclear collisions at the CERN Future Circular Collider (FCC) are summarized. Lead-lead (PbPb) and proton-lead (pPb) collisions at $s_{N N}$ = 39 and 63 TeV respectively with $L_{in t}$ = 33 nb $^{- 1}$ and 8 pb $^{- 1}$ monthly integrated luminosities, will provide unprecedented experimental conditions to study quark-gluon matter at temperatures $O$ (1 GeV). The following topics are succinctly discussed: (i) charm-quark densities thrice larger than at the LHC, leading to direct heavy-quark impact in the bulk QGP properties, (ii) quarkonia, including $Υ (1 S)$ , melting at temperatures up to five times above the QCD critical temperature, (iii) access to initial-state nuclear parton distributions (nPDF) at fractional momenta as low as $x \approx 1 0^{- 7}$ , (iv) availability of $5 \cdot 1 0^{5}$ top-quark pairs per run to study the high- $x$ gluon nPDF and the energy loss properties of boosted colour-antennas, (v) study of possible Higgs boson suppression in the QGP, and (vi) high-luminosity $γ γ$ (ultraperipheral) collisions at c.m. energies up to 1 TeV.
↳ hep-exhep-phnucl-exnucl-thNPA(2017)·10 citations
09
The QCD Equation of state and critical end-point estimates at $O (μ_{B}^{6})$
Sayantan Sharma · for Bielefeld-BNL-CCNU collaboration
We present results for the QCD Equation of State at non-zero chemical potentials corresponding to the conserved charges in QCD using Taylor expansion upto sixth order in the baryon number, electric charge and strangeness chemical potentials. The latter two are constrained by the strangeness neutrality and a fixed electric charge to baryon number ratio. In our calculations, we use the Highly Improved Staggered Quarks (HISQ) discretization scheme at physical quark masses and at different values of the lattice spacings to control lattice cut-off effects. Furthermore we calculate the pressure along lines of constant energy density, which serve as proxies for the freeze-out conditions and discuss their dependence on $μ_{B}$ , which is necessary for hydrodynamic modelling near freezeout. We also provide an estimate of the radius of convergence of the Taylor series from the 6th order coefficients which provides a new constraint on the location of the critical end-point in the T- $μ_{B}$ plane of the QCD phase diagram.
↳ hep-lathep-phnucl-exnucl-thNPA(2017)·9 citations
10
Electromagnetic decays of the neutral pion
Esther Weil🇩🇪 · Gernot Eichmann🇩🇪 · Christian S. Fischer🇩🇪 · Richard Williams🇩🇪
We complement studies of the neutral pion transition form factor pi^0 --> gamma^(*) gamma^(*) with calculations for the electromagnetic decay widths of the processes pi^0 --> e^+ e^-, pi^0 --> e^+ e^- gamma and pi^0 --> e^+ e^- e^+ e^-. Their common feature is that the singly- or doubly-virtual transition form factor serves as a vital input that is tested in the non-perturbative low-momentum region of QCD. We determine this form factor from a well-established and symmetry-preserving truncation of the Dyson-Schwinger equations. Our results for the three- and four-body decays match results of previous theoretical calculations and experimental measurements. For the rare decay we employ a numerical method to calculate the process directly by deforming integration contours, which in principle can be generalized to arbitrary integrals as long as the analytic structure of the integrands are known. Our result for the rare decay is in agreement with dispersive calculations but still leaves a 2 sigma discrepancy between theory and experiment.
↳ hep-phhep-latnucl-thPRD(2017)·65 citations
11
Scale Invariance in Heavy Hadron Molecules
Lisheng Geng🇨🇳 · Junxu Lu🇨🇳 · Manuel Pavon Valderrama🇨🇳
We discuss a scenario in which the $P_{c} (4450)^{+}$ heavy pentaquark is a $Σ_{c} D ˉ^{*}$ - $Λ_{c} (2595) D ˉ$ molecule. The $Λ_{c 1} D ˉ \to Σ_{c} D ˉ^{*}$ transition is mediated by the exchange of a pion almost on the mass shell that generates a long-range $1/ r^{2}$ potential. This is analogous to the effective force that is responsible for the Efimov spectrum in three-boson systems interacting through short-range forces. The equations describing this molecule exhibit approximate scale invariance, which is anomalous and broken by the solutions. If the $1/ r^{2}$ potential is strong enough this symmetry survives in the form of discrete scale invariance, opening the prospect of an Efimov-like geometrical spectrum in two-hadron systems. For a molecular pentaquark with quantum numbers $\frac{3}{2}^{-}$ the attraction is not enough to exhibit discrete scale invariance, but this prospect might very well be realized in a $\frac{1}{2}^{+}$ pentaquark or in other hadron molecules involving transitions between particle channels with opposite intrinsic parity and a pion near the mass shell. A very good candidate is the $Λ_{c} (2595) Ξ ˉ_{b} - Σ_{c} Ξ ˉ_{b}^{'}$ molecule. Independently of this, the $1/ r^{2}$ force is expected to play a very important role in the formation of this type of hadron molecule, which points to the existence of $\frac{1}{2}^{+}$ $Σ_{c} D^{*}$ - $Λ_{c} (2595) D$ and $1^{+}$ $Λ_{c} (2595) Ξ_{b} - Σ_{c} Ξ_{b}^{'}$ molecules and $0^{+}$ / $1^{-}$ $Λ_{c} (2595) Ξ ˉ_{b} - Σ_{c} Ξ ˉ_{b}^{'}$ baryonia.
↳ hep-phnucl-thPRD(2018)·39 citations
12
Chiral Extrapolations of the $ρ (770)$ Meson in $N_{f} = 2 + 1$ Lattice QCD Simulations
B. Hu🇺🇸 · R. Molina🇺🇸 · M. Döring🇺🇸 · M. Mai🇺🇸 · A. Alexandru🇺🇸
Recent $N_{f} = 2 + 1$ lattice data for meson-meson scattering in $p$ -wave and isospin $I = 1$ are analyzed using a unitarized model inspired by Chiral Perturbation Theory in the inverse-amplitude formulation for two and three flavors. Chiral extrapolations are performed that postdict phase shifts extracted from experiment quite well. In addition, the low-energy constants are compared to the ones from a recent analysis of $N_{f} = 2$ lattice QCD simulations to check for the consistency of the hadronic model used here. Some inconsistencies are detected in the fits to $N_{f} = 2 + 1$ data, in contrast to the previous analysis of $N_{f} = 2$ data.
↳ hep-latnucl-thPRD(2017)·42 citations

Affiliations

first authorsco-authorsvia INSPIRE

Simulating chiral magnetic effect and anomalous transport phenomena in the pre-equilibrium stages of heavy-ion collisions

Physics with ions at the Future Circular Collider

The QCD Equation of state and critical end-point estimates at O(μB6​)

Electromagnetic decays of the neutral pion

Scale Invariance in Heavy Hadron Molecules

Chiral Extrapolations of the ρ(770) Meson in Nf​=2+1 Lattice QCD Simulations

Affiliations

The QCD Equation of state and critical end-point estimates at $O (μ_{B}^{6})$

Chiral Extrapolations of the $ρ (770)$ Meson in $N_{f} = 2 + 1$ Lattice QCD Simulations