Nuclear Theory·nucl-th

Wednesday·December 19, 2018

12 papers—4 primary·8 cross-listed

01
Chiral QCD phase in equilibrium with Hadron Gas and the location of the critical point
N. G. Antoniou🇬🇷 · F. K. Diakonos🇬🇷 · A. S. Kapoyannis🇬🇷
We develop a description of the equation of state of QCD matter with restored chiral symmetry, which is in thermal and chemical equilibrium with the hadronic phase. The hadron gas is described with thermodynamically consistent volume corrections. The chiral phase is composed of a set of few quark condensates, each of which corresponds to a family of hadrons with specific quark content. On the boundary between the two phases we apply the requirement of conservation of particle numbers per family. We use lattice calculations for temperatures below the transition curve to determine hadronic volumes. We find that the pion system plays decisive role in the shift of the transition from higher order (crossover) to first order. For four volume models we calculate the location of the critical point as function of critical temperature $T_{c}$ at vanishing baryon density. Particularly, if we additionally impose the equality between the densities of quarks contained in mesons and baryons, we find a critical point residing in the interval of baryon chemical potential $μ_{B} ≃$ 233-267 MeV and of temperature $T ≃$ 153-158 MeV.
nucl-thhep-ph0 citations
02
Nucleon microscopy in proton-nucleus scattering via analysis of bremsstrahlung emission
Sergei P. Maydanyuk (1 and 2)🇨🇳 · Peng-Ming Zhang (1)🇨🇳 · Li-Ping Zou (1) ((1) Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China, (2) Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kiev, Ukraine)🇨🇳
We investigate an idea, how to use analysis of the bremsstrahlung photons to study the internal structure of proton under nuclear reaction with nucleus. A new model is constructed to describe bremsstrahlung emission of photons which accompanies the scattering of protons off nuclei. Our bremsstrahlung formalism uses many-nucleon basis that allows to analyze coherent and incoherent bremsstrahlung emissions. As scattered proton can be under the influence of strong forces and produces the largest bremsstrahlung contribution to full spectrum, we focus on accurate determination of its quantum evolution concerning nucleus basing on quantum mechanics and scattering theory. For such a motivation, we at first time generalize Pauli equation with interacting potential describing evolution of fermion inside strong field, with including the electromagnetic form-factors of nucleon basing on DIS theory. Anomalous magnetic momenta of nucleons reinforce our motivation to develop such a formalism, starting from low energy. The full bremsstrahlung spectrum in our model (after renormalization) is dependent on form-factors of the scattered proton. For calculations, we choose the scattering of $p +^{197} Au$ at proton beam energy of 190~MeV, where experimental bremsstrahlung data were obtained with high accuracy. We show that the full bremsstrahlung spectrum is sensitive to the form-factors of the scattered proton. In the limit without such form-factors, we reconstruct our previous result (where internal structure of the scattered proton was not studied).
nucl-thPRC(2019)·10 citations
03
Charmonium decay widths in magnetized matter
Amruta Mishra🇮🇳 · Amal Jahan CS🇮🇳 · Shivam Kesarwani🇮🇳 · Haresh Raval🇮🇳 · Shashank Kumar🇮🇳 · Jitendra Meena🇮🇳
We study the partial decay widths of the charmonium states ( $J / ψ$ , $ψ (3686)$ , $ψ (3770)$ , $χ_{c 0}$ , $χ_{c 2}$ ) to $D D ˉ$ ( $D^{+} D^{-}$ or $D^{0} D^{0} ˉ$ ) in isospin asymmetric nuclear matter, in the presence of strong magnetic fields. The in-medium partial decay widths of charmonium states to $D D ˉ$ are calculated within a light quark--antiquark pair creation model, namely the $^{3} P_{0}$ model, using the in--medium masses of the charmonia as well as $D$ and $D ˉ$ mesons in the magnetized nuclear matter obtained within a chiral effective model. The presence of a magnetic field leads to Landau quantization of the energy levels of the proton in the nuclear medium. The effects of magnetic field and isospin asymmetry on the charmonium decay widths to $D D ˉ$ are found to be quite prominent. The effects of the anomalous magnetic moments have also been taken into consideration for obtaining the in-medium masses of these heavy flavour mesons, used to calculate the partial decay widths of the charmonium states. The medium modifications of the charmonium decay widths can have observable consequences on the production of the charmed mesons in high energy asymmetric heavy ion collision experiments.
nucl-thhep-phEPJA(2019)·29 citations
04
Jet structure in integrated EPOS3-HQ approach
Iurii Karpenko🇫🇷 · Martin Rohrmoser🇵🇱 · Pol Gossiaux🇫🇷 · Joerg Aichelin🇫🇷 · Klaus Werner🇫🇷
We report on the first results for jet observables from a time-like parton cascade integrated with hydrodynamic evolution within the EPOS3-HQ framework. The hard (jet) partons are produced along with soft partons in the initial state EPOS approach. The soft partons, represented by strings, melt into a thermalized medium which is described by a 3 dimensional event-by-event viscous hydrodynamic approach. The jet partons then propagate in the hydrodynamically expanding medium. The total jet energy gets progressively `degraded' when the partons reaching a thermal energy scale are melted into the hydrodynamic medium via the source terms. The full evolution proceeds in a parallel mode, without separating the thermalized and jet parts. We demonstrate how the transverse expansion of the medium affects the jet structure, and how the medium itself is affected by the jet recoil.
nucl-thhep-phnucl-exPoS(2018)·1 citation
05
Unravelling High-Energy Hadron Structures with Lattice QCD
Yong Zhao🇺🇸
Parton distribution functions are key quantities for us to understand the hadronic structures in high-energy scattering, but they are difficult to calculate from lattice QCD. Recent years have seen fast development of the large-momentum effective theory which allows extraction of the $x$ -dependence of parton distribution functions from a quasi-parton distribution function that can be directly calculated on lattice. The extraction is based on a factorization formula for the quasi-parton distribution function that has been derived rigorously in perturbation theory. A systematic procedure that includes renormalization, perturbative matching, and power corrections has been established to calculate parton distribution functions. Latest progress from lattice QCD has shown promising signs that it will become an effective tool for calculating parton physics.
↳ hep-phhep-latnucl-thInt.J.Mod.Phys.A(2019)·33 citations
06
Jet quenching parameter in an expanding QCD plasma
Edmond Iancu🇫🇷 · Pieter Taels🇫🇷 · Bin Wu🇨🇭
We present a new definition of the jet quenching parameter $q^$ in a weakly-coupled quark-gluon plasma undergoing boost-invariant longitudinal expansion. We propose a boost-invariant definition of $q^$ , which is proportional to the broadening of the angular variables $η$ (the pseudo-rapidity) and $ϕ$ (the azimuthal angle). We furthermore consider radiative corrections to $q^$ and find potentially large corrections enhanced by a double logarithm like the case of a static medium. But unlike for the static medium, these corrections are now local in (proper) time.
↳ hep-phhep-exnucl-exnucl-thPoS(2018)·0 citations
07
Hyperons in thermal QCD: A lattice view
Gert Aarts🇬🇧 · Chris Allton🇬🇧 · Davide De Boni🇬🇧 · Benjamin Jäger🇩🇰
The hadron resonance gas (HRG) is a widely used description of matter under extreme conditions, e.g. in the context of heavy-ion phenomenology. Commonly used implementations of the HRG employ vacuum hadron masses throughout the hadronic phase and hence do not include possible in-medium effects. Here we investigate this issue, using nonperturbative lattice simulations employing the FASTSUM anisotropic Nf=2+1 ensembles. We study the fate of octet and decuplet baryons as the temperature increases, focussing in particular on the positive- and negative-parity groundstates. While the positive-parity groundstate masses are indeed seen to be temperature independent, within the error, a strong temperature dependence is observed in the negative-parity channels. We give a simple parametrisation of this and formulate an in-medium HRG, which is particularly effective for hyperons. Parity doubling is seen to emerge in the deconfined phase at the level of correlators, with a noticeable effect of the heavier s quark. Channel dependence of this transition is analysed.
↳ hep-lathep-phnucl-thPRD(2019)·84 citations
08
The Angular Power Spectrum of Heavy Ion Collisions
Meera Machado🇩🇰 · Poul Henrik Damgaard🇩🇰 · Jens Jørgen Gaardhøje🇩🇰 · Christian Bourjau🇩🇰
Particles produced in heavy ion collisions carry information about anisotropies present already in the early state of the system and play a crucial role in understanding the Quark Gluon Plasma and its evolution. We explore the angular power spectrum of particle multiplicities in such heavy ion collisions to extract fluctuations in particle multiplicities on the surface a sphere. Results are presented for Pb-Pb data at $s_{N N} = 2.76 TeV$ , extracted from the ALICE open data portal. We find that odd modes of the power spectrum display a power-law behavior with corresponding index $β$ , which is found to be close to unity. We also demonstrate that the angular power spectrum allows us to extract accurately the flow coefficients of non-central collisions.
↳ hep-phnucl-thPRC(2019)·5 citations
09
Anyon optics with time-of-flight two-particle interference of double-well-trapped interacting ultracold atoms
Constantine Yannouleas · Uzi Landman
The subject of bianyon interference with ultracold atoms is introduced through theoretical investigations pertaining to the second-order momentum correlation maps of two anyons (built upon spinless and spin-1/2 bosonic, as well as spin-1/2 fermionic ultracold atoms) trapped in a double-well optical trap. The two-particle system is modeled according to the recently proposed protocols for emulating an anyonic Hubbard Hamiltonian in ultracold-atom one-dimensional lattices. Because the second-order momentum correlations are mirrored in the time-of-flight second-order interference patterns in space, our findings provide impetus for time-of-flight experimental protocols for detecting anyonic statistics via interferometry measurements of massive particles that broaden the scope of the biphoton interferometry of quantum optics.
↳ cond-mat.quant-gasnucl-thquant-phPRA(2019)·7 citations
10
$β^{-}$ decay study of the $^{66}$ Mn - $^{66}$ Fe - $^{66}$ Co - $^{66}$ Ni chain
M. Stryjczyk🇧🇪 · Y. Tsunoda🇯🇵 · I. G. Darby🇧🇪 · H. De Witte🇧🇪 · J. Diriken🇧🇪 · D. V. Fedorov🇷🇺 · V. N. Fedosseev🇨🇭 · L. M. Fraile🇪🇸 · M. Huyse🇧🇪 · U. Köster🇫🇷 · B. A. Marsh🇨🇭 · T. Otsuka🇯🇵 and 10 other authors
Background: Shell evolution can impact the structure of the nuclei and lead to effects such as shape coexistence. The nuclei around $^{68}$ Ni represent an excellent study case, however, spectroscopic information of the neutron-rich, $Z < 28$ nuclei is limited. Purpose: The goal is to measure $γ$ -ray transitions in $^{66}$ Fe, $^{66}$ Co and $^{66}$ Ni populated in the $β^{-}$ decay of $^{66}$ Mn, to determine absolute $β$ -feedings and relative $γ$ -decay probabilities and to compare the results with Monte Carlo Shell Model calculations in order to study the influence of the relevant single neutron and proton orbitals occupancies around $Z = 28$ and $N = 40$ . Method: The low-energy structures of $^{65, 66}$ Fe, $^{66}$ Co and $^{66}$ Ni were studied in the $β^{-}$ decay of $^{66}$ Mn produced at ISOLDE, CERN. The beam was purified by means of laser resonance ionization and mass separation. The $β$ and $γ$ events detected by three plastic scintillators and two MiniBall cluster germanium detectors, respectively, were correlated in time to build the low-energy excitation schemes and to determine the $β$ -decay half-lives of the nuclei. Results: The relative small $β$ -decay ground state feeding of $^{66}$ Fe obtained in this work is at variant to the earlier studies. Spin and parity $1^{+}$ was assigned to the $^{66}$ Co ground state based on the strong ground state feeding in the decay of $^{66}$ Fe as well as in the decay of $^{66}$ Co. Experimental log(ft) values, $γ$ -ray deexcitation patterns and energies of excited states were compared to Monte Carlo Shell Model calculations. Based on this comparison, spin and parity assignments for the selected number of low-lying states in the $^{66}$ Mn to $^{66}$ Ni chain were proposed. Conclusions: The $β$ -decay chain starting $^{66}$ Mn towards $^{66}$ Ni, crossing $N = 40$ , evolves from deformed nuclei to sphericity...
↳ nucl-exnucl-thPRC(2018)·19 citations
11
Jet substructure in high-energy hadron collisions
Felix Ringer🇺🇸
In the past years significant progress has been made toward achieving a quantitative understanding of jets and their substructure in high-energy proton-proton collisions from first principles in QCD. Precise measurements have become available from the experimental collaborations at the LHC and RHIC allowing a direct comparison of theoretical calculations and data. These developments make it possible to use jet substructure observables as precision probes in heavy-ion collisions. The radiation pattern inside jets contains valuable information about the hot and dense QCD medium which can be investigated using jet substructure techniques. By studying the soft sensitivity of the different observables it is possible to obtain important insights into the interaction of hard probes with the quark gluon plasma.
↳ hep-phhep-exnucl-exnucl-thPoS(2018)·0 citations
12
A transverse momentum dependent framework for back-to-back photon+jet production
Maarten G.A. Buffing🇺🇸 · Zhong-Bo Kang🇺🇸 · Kyle Lee🇺🇸 · Xiaohui Liu🇨🇳
We propose the $pp \to jet + γ$ as a new process for studying the Transverse Momentum Dependent Parton Distribution Functions (TMDs). To do so, we developed a novel framework for the jet- $γ$ imbalance in $pp \to jet + γ$ using Soft Collinear Effective Theory. The new framework opens up many new insights to the TMDs which the current TMD studies confined to the Drell-Yan and semi-inclusive deep inelastic scattering processes cannot achieve. The established formalism provides, for the first time, a first principle prediction of the jet- $γ$ imbalance in $pp$ collisions and therefore a first direct probe of the factorization breaking effects when compared with the future experimental data. If the factorization breaking effects are found small, the process will offer the unique sensitivities to both the polarized and un-polarized quark/gluon TMDs. We demonstrate the predictive power of the framework by calculating each component in the formalism to the next-to-leading order accuracy and by realizing the next-to-leading-logarithmic evolution. We provide the first numerical estimates for this process, for both the unpolarized cross section and the Sivers asymmetry.
↳ hep-phnucl-th52 citations

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