Nuclear Theory·nucl-th

Monday·June 29, 2020

8 papers—2 primary·6 cross-listed

03
[Submitted on 25 Jun 2020] (cross-list from hep-ph)
nNNPDF2.0: Quark Flavor Separation in Nuclei from LHC Data
Rabah Abdul Khalek🇳🇱 · Jacob J. Ethier🇳🇱 · Juan Rojo🇳🇱 · Gijs van Weelden🇳🇱
We present a model-independent determination of the nuclear parton distribution functions (nPDFs) using machine learning methods and Monte Carlo techniques based on the NNPDF framework. The neutral-current deep-inelastic nuclear structure functions used in our previous analysis, nNNPDF1.0, are complemented by inclusive and charm-tagged cross-sections from charged-current scattering. Furthermore, we include all available measurements of W and Z leptonic rapidity distributions in proton-lead collisions from ATLAS and CMS at $s = 5.02$ TeV and 8.16 TeV. The resulting nPDF determination, nNNPDF2.0, achieves a good description of all datasets. In addition to quantifying the nuclear modifications affecting individual quarks and antiquarks, we examine the implications for strangeness, assess the role that the momentum and valence sum rules play in nPDF extractions, and present predictions for representative phenomenological applications. Our results, made available via the LHAPDF library, highlight the potential of high-energy collider measurements to probe nuclear dynamics in a robust manner.
Comments:
65 pages, 26 figures. The nNNPDF2.0 sets are available from http://nnpdf.mi.infn.it/for-users/nuclear-pdfs/
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2006.14629 [pdf]
JHEP(2020)·122 citations
04
[Submitted on 26 Jun 2020] (cross-list from hep-ph)
Hadron production in elementary nucleon-nucleon reactions from low to ultra-relativistic energies
V. Kireyeu🇷🇺 · I. Grishmanovskii🇩🇪 · V. Kolesnikov🇷🇺 · V. Voronyuk🇷🇺 · E. Bratkovskaya🇩🇪
We study the hadron production in $p + p$ , $p + n$ and $n + n$ reactions within the microscopic Parton-Hadron-Dynamics (PHSD) transport approach in comparison to PYTHIA 8.2. We discuss the details of the "PHSD tune" of the Lund string model (realized by event generators FRITIOF and PYTHIA) in the vacuum (as in $N + N$ collisions) as well as its in-medium modifications relevant for heavy-ion collisions where a hot and dense matter is produced. We compare the results of PHSD and PYTHIA 8.2 (default version) for the excitation function of hadron multiplicities as well as differential rapidity $y$ , transverse momentum $p_{T}$ and $x_{F}$ distributions in $p + p$ , $p + n$ and $n + n$ reactions with the existing experimental data in the energy range $s_{N N} = 2.7 - 7000$ GeV. We discuss the production mechanisms of hadrons and the role of final state interactions (FSI) due to the hadronic rescattering. We also show the influence of the possible quark-gluon plasma (QGP) formation on hadronic observables in $p + p$ collisions at LHC energies. We stress the importance of developing a reliable event generator for elementary reactions from low to ultra-relativistic energies in view of actual and upcoming heavy-ion experiments.
Comments:
18 pages, 17 figures; extended version to be published in the European Physical Journal A
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2006.14739 [pdf]
EPJA(2020)·28 citations
05
[Submitted on 26 Jun 2020] (cross-list from astro-ph.HE)
Parameter estimation for strong phase transitions in supranuclear matter using gravitational-wave astronomy
Peter T. H. Pang🇳🇱 · Tim Dietrich🇩🇪 · Ingo Tews🇺🇸 · Chris Van Den Broeck🇳🇱
At supranuclear densities, explored in the core of neutron stars, a strong phase transition from hadronic matter to more exotic forms of matter might be present. To test this hypothesis, binary neutron-star mergers offer a unique possibility to probe matter at densities that we can not create in any existing terrestrial experiment. In this work, we show that, if present, strong phase transitions can have a measurable imprint on the binary neutron-star coalescence and the emitted gravitational-wave signal. We construct a new parameterization of the supranuclear equation of state that allows us to test for the existence of a strong phase transition and extract its characteristic properties purely from the gravitational-wave signal of the inspiraling neutron stars. We test our approach using a Bayesian inference study simulating 600 signals with three different equations of state and find that for current gravitational-wave detector networks already twelve events might be sufficient to verify the presence of a strong phase transition. Finally, we use our methodology to analyze GW170817 and GW190425, but do not find any indication that a strong phase transition is present at densities probed during the inspiral.
Comments:
17 pages, 11 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2006.14936 [pdf]
PRResearch(2020)·44 citations
06
[Submitted on 26 Jun 2020] (cross-list from hep-ph)
The nature of $X (3872)$ from high-multiplicity $pp$ collisions
Angelo Esposito🇨🇭 · Elena G. Ferreiro🇪🇸 · Alessandro Pilloni🇮🇹 · Antonio D. Polosa🇮🇹 · Carlos A. Salgado🇪🇸
The structure of exotic resonances that do not trivially fit the usual quark model expectations has been a matter of intense scientific debate during the last two decades. A possible way of estimating the size of these states is to study their behavior when immersed in QCD matter. Recently, LHCb has measured the relative abundance of the exotic $X (3872)$ over the ordinary $ψ (2 S)$ . We use the comover interaction model to study the yield of a compact $X (3872)$ . To confirm the reliability of the model in high-multiplicity $pp$ collisions, we describe the suppression of excited over ground $Υ$ states. With this at hand, we show that the size of the compact $X (3872)$ would be slightly larger than that of the $ψ (2 S)$ . If the $X (3872)$ is instead assumed to be a meson molecule of large size, we argue that its evolution in QCD matter should be described via a coalescence model, as suggested by data on deuteron production. We show that the predictions of this model for the $X (3872)$ are in contrast with data.
Comments:
11 pages, 6 figures. Presentation updated, references added, conclusions unchanged. Version accepted in EPJC
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2006.15044 [pdf]
EPJC(2021)·107 citations
07
[Submitted on 26 Jun 2020] (cross-list from nucl-ex)
Fast-timing study of $^{81}$ Ga from the $β$ decay of $^{81}$ Zn
V. Paziy🇪🇸 · L.M. Fraile🇪🇸 · H. Mach🇪🇸 · B. Olaizola🇪🇸 · G.S. Simpson🇫🇷 · A. Aprahamian🇺🇸 · C. Bernards🇩🇪 · J.A. Briz🇪🇸 · B. Bucher🇺🇸 · C.J. Chiara🇺🇸 · Z. Dlouhý🇵🇱 · I. Gheorghe🇷🇴 and 14 other authors
The $β^{-}$ decay of $^{81}$ Zn to the neutron magic $N = 50$ nucleus $^{81}$ Ga, with only three valence protons with respect to $^{78}$ Ni, was investigated. The study was performed at the ISOLDE facility at CERN by means of $γ$ spectroscopy. The $^{81}$ Zn half-life was determined to be $T_{1/2} = 290 (4)$ ms while the $β$ -delayed neutron emission probability was measured as $P_{n} = 23 (4) %$ . The analysis of the $β$ -gated $γ$ -ray singles and $γ$ - $γ$ coincidences from the decay of $^{81}$ Zn provides 47 new levels and 70 new transitions in $^{81}$ Ga. The $β^{-}$ $n$ decay of $^{81}$ Zn was observed and a new decay scheme into the odd-odd $^{80}$ Ga nucleus was established. The half-lives of the first and second excited states of $^{81}$ Ga were measured via the fast-timing method using LaBr $_{3}$ (Ce) detectors. The level scheme and transition rates are compared to large-scale shell-model calculations. The low-lying structure of $^{81}$ Ga is interpreted in terms of the coupling of the three valence protons outside the doubly-magic $^{78}$ Ni core.
Comments:
Submitted to Phys. Rev. C
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2006.15095 [pdf]
PRC(2020)·9 citations
08
[Submitted on 26 Jun 2020] (cross-list from hep-ph)
The JIMWLK evolution and the s-channel unitarity
Alex Kovner🇺🇸 · Eugene Levin🇨🇱 · Ming Li🇺🇸 · Michael Lublinsky🇮🇱
Further developing ideas set forth in \cite{KLL}, we discuss QCD Reggeon Field Theory (RFT) and formulate restrictions imposed on its Hamiltonian by the unitarity of underlying QCD. We identify explicitly the QCD RFT Hilbert space, provide algebra of the basic degrees of freedom (Wilson lines and their duals) and the algorithm for calculating the scattering amplitudes. We formulate conditions imposed on the "Fock states" of RFT by unitary nature of QCD, and explain how these constraints appear as unitarity constraints on possible RFT hamiltonians that generate energy evolution of scattering amplitudes. We study the realization of these constraints in the dense-dilute limit of RFT where the appropriate Hamiltonian is the JIMWLK Hamiltonian $H_{J I M W L K}$ . We find that the action $H_{J I M W L K}$ on the dilute projectile states is unitary, but acting on dense "target" states it violates unitarity and generates states with negative probabilities through energy evolution.
Comments:
30 pages, 3 figures, added discussions on IR-divergence as suggested by the referee
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2006.15126 [pdf]
JHEP(2020)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE

nNNPDF2.0: Quark Flavor Separation in Nuclei from LHC Data

Hadron production in elementary nucleon-nucleon reactions from low to ultra-relativistic energies

Parameter estimation for strong phase transitions in supranuclear matter using gravitational-wave astronomy

The nature of X(3872) from high-multiplicity pp collisions

Fast-timing study of 81Ga from the β decay of 81Zn

The JIMWLK evolution and the s-channel unitarity

Affiliations

The nature of $X (3872)$ from high-multiplicity $pp$ collisions

Fast-timing study of $^{81}$ Ga from the $β$ decay of $^{81}$ Zn