Nuclear Theory·nucl-th

Monday·October 23, 2017

10 papers—4 primary·6 cross-listed

05
Constraints on the hadronic spectrum from Lattice QCD
Paolo Parotto🇺🇸
The spectrum of hadronic resonances continually receives updates from the Particle Data Group, which lists every state with a status representing how established the state is. Moreover, the existence of additional states is predicted by relativistic quark models. It has been suggested that further states might need to be included in the hadronic spectrum in order to improve the agreement between the hadron resonance gas model predictions and lattice QCD data. Such an inclusion would also affect the results of many areas of heavy-ion collision physics that make use of hadronic degrees of freedom, such as hydrodynamical simulations afterburners. However, for some selected observables, the inclusion of further states worsens the agreement with the lattice results. We propose new observables, sensitive to the spectrum content divided by quantum numbers, which allow us to gauge the contribution of additional states. The comparison of Lattice QCD results and predictions from the Hadron Resonance Gas model for these observables, helps to clarify the situation and determine how many, and which new states are needed.
↳ hep-phhep-latnucl-thJ.Phys.Conf.Ser.(2018)·0 citations
06
Jet Quenching in The Most Vortical Fluid: A Holographic Approach
Brett McInnes🇸🇬
The STAR collaboration at the RHIC facility has recently announced the exciting discovery of direct evidence for extremely large vorticity in the Quark-Gluon Plasma generated in peripheral collisions, seen in the form of global polarization of $Λ$ and $Λ ˉ$ hyperons. This prompts the question: does this vorticity have any effect on other observed phenomena, such as jet quenching? Using a simple gauge-gravity model, we suggest that such an effect may be detectable, in data from near-future experiments, as a reduction in the jet quenching parameter. This is predicted to be most prominent in collisions corresponding to a narrow range of centralities around $10%$ . The relative reduction (compared to collisions at zero or, alternatively, large centrality) is predicted to behave in an unexpected and characteristic manner: the model suggests that it is independent of the impact energy.
↳ hep-phhep-thnucl-th7 citations
07
Structure of 55Sc and development of the N=34 subshell closure
D. Steppenbeck · S. Takeuchi · N. Aoi · P. Doornenbal · M. Matsushita · H. Wang · H. Baba · S. Go · J. D. Holt · J. Lee · K. Matsui · S. Michimasa and 13 other authors
The low-lying structure of $^{55}$ Sc has been investigated using in-beam $γ$ -ray spectroscopy with the $^{9}$ Be( $^{56}$ Ti, $^{55}$ Sc+ $γ$ ) $X$ one-proton removal and $^{9}$ Be( $^{55}$ Sc, $^{55}$ Sc+ $γ$ ) $X$ inelastic-scattering reactions at the RIKEN Radioactive Isotope Beam Factory. Transitions with energies of 572(4), 695(5), 1539(10), 1730(20), 1854(27), 2091(19), 2452(26), and 3241(39) keV are reported, and a level scheme has been constructed using $γ γ$ coincidence relationships and $γ$ -ray relative intensities. The results are compared to large-scale shell-model calculations in the $s d$ - $p f$ model space, which account for positive-parity states from proton-hole cross-shell excitations, and to it ab initio shell-model calculations from the in-medium similarity renormalization group that includes three-nucleon forces explicitly. The results of proton-removal reaction theory with the eikonal model approach were adopted to aid identification of positive-parity states in the level scheme; experimental counterparts of theoretical $1/ 2_{1}^{+}$ and $3/ 2_{1}^{+}$ states are suggested from measured decay patterns. The energy of the first $3/ 2^{-}$ state, which is sensitive to the neutron shell gap at the Fermi surface, was determined. The result indicates a rapid weakening of the $N = 34$ subshell closure in $p f$ -shell nuclei at $Z > 20$ , even when only a single proton occupies the $π f_{7/2}$ orbital.
↳ nucl-exnucl-thPRC(2017)·29 citations
08
Dual Formulation and Phase Diagram of Lattice QCD in the Strong Coupling Regime
Giuseppe Gagliardi🇩🇪 · Jangho Kim🇩🇪 · Wolfgang Unger🇩🇪
We present the computation of invariants that arise in the strong coupling expansion of lattice QCD. These invariants are needed for Monte Carlo simulations of Lattice QCD with staggered fermions in a dual, color singlet representation. This formulation is in particular useful to tame the finite density sign problem. The gauge integrals in this limiting case $β \to 0$ are well known, but the gauge integrals needed to study the gauge corrections are more involved. We discuss a method to evaluate such integrals. The phase boundary of lattice QCD for staggered fermions in the $μ_{B} - T$ plane has been established in the strong coupling limit. We present numerical simulations away from the strong coupling limit, taking into account the higher order gauge corrections via plaquette occupation numbers. This allows to study the nuclear and chiral transition as a function of $β$ .
↳ hep-latnucl-thEPJ Web Conf.(2018)·20 citations
09
Importance of non-flow in mixed-harmonic multi-particle correlations in small collision systems
Peng Huo🇺🇸 · Katarina Gajdosova🇩🇰 · Jiangyong Jia🇺🇸 · You Zhou🇩🇰
Recently CMS Collaboration measured mixed-harmonic four-particle azimuthal correlations, known as symmetric cumulants SC(n,m), in pp and pPb collisions, and interpreted the non-zero SC(n,m) as evidence for long-range collectivity in these small collision systems. Using the PYTHIA and HIJING models which do not have genuine long-range collectivity, we show that the CMS results, obtained with standard cumulant method, could be dominated by non-flow effects associated with jet and dijets, especially in $pp$ collisions. We show that the non-flow effects are largely suppressed using the recently proposed subevent cumulant methods by requiring azimuthal correlation between two or more pseudorapidity ranges. We argue that the reanalysis of SC(n,m) using the subevent method in experiments is necessary before they can used to provide further evidences for a long-range multi-particle collectivity and constraints on theoretical models in small collision systems.
↳ nucl-exhep-phnucl-thPLB(2018)·53 citations
10
Novel subjet observables for jet quenching in heavy-ion collisions
Liliana Apolinário🇵🇹 · José Guilherme Milhano🇵🇹 · Mateusz Ploskon🇺🇸 · Xiaoming Zhang🇨🇳
Using a novel observable that relies on the momentum difference of the two most energetic subjets within a jet $Δ S_{12}$ we study the internal structure of high-energy jets simulated by several Monte Carlo event generators that implement the partonic energy-loss in a dense partonic medium. Based on inclusive jet and di-jet production we demonstrate that $Δ S_{12}$ is an effective tool to discriminate between different models of jet modifications over a broad kinematic range. The new quantity, while preserving the colinear and infrared safety of modern jet algorithms, it is experimentally attractive because of its inherent resiliance against backgrounds of heavy-ion collisions.
↳ hep-phhep-exnucl-thEPJC(2018)·37 citations

Affiliations

first authorsco-authorsvia INSPIRE

Constraints on the hadronic spectrum from Lattice QCD

Jet Quenching in The Most Vortical Fluid: A Holographic Approach

Structure of 55Sc and development of the N=34 subshell closure

Dual Formulation and Phase Diagram of Lattice QCD in the Strong Coupling Regime

Importance of non-flow in mixed-harmonic multi-particle correlations in small collision systems

Novel subjet observables for jet quenching in heavy-ion collisions

Affiliations