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Nuclear Theory·nucl-th

Thursday·February 15, 2018

11 papers—5 primary·6 cross-listed

All11Primary5Cross-lists6
  1. 06

    Heavy Ion Collisions: The Big Picture, and the Big Questions

    Wit Busza🇺🇸 · Krishna Rajagopal🇺🇸 · Wilke van der Schee🇺🇸

    Heavy ion collisions quickly form a droplet of quark-gluon plasma (QGP) with a remarkably small viscosity. We give an accessible introduction to how to study this smallest and hottest droplet of liquid made on earth and why it is so interesting. The physics of heavy ions ranges from highly energetic quarks and gluons described by perturbative QCD to a bath of strongly interacting gluons at lower energy scales. These gluons quickly thermalize and form QGP, while the energetic partons traverse this plasma and end in a shower of particles called jets. Analyzing the final particles in a variety of different ways allows us to study the properties of QGP and the complex dynamics of multi-scale processes in QCD which govern its formation and evolution, providing what is perhaps the simplest form of complex quantum matter that we know of. Much remains to be understood, and throughout the review big open questions will be encountered.

    ↳ hep-phhep-thnucl-exnucl-thAnn.Rev.Nucl.Part.Sci.(2018)·1140 citations
  2. 07

    Neutron Star Mergers Chirp About Vacuum Energy

    Csaba Csáki🇺🇸 · Cem Eröncel🇺🇸 · Jay Hubisz🇺🇸 · Gabriele Rigo🇺🇸 · John Terning🇺🇸

    Observations of gravitational waves from neutron star mergers open up novel directions for exploring fundamental physics: they offer the first access to the structure of objects with a non-negligible contribution from vacuum energy to their total mass. The presence of such vacuum energy in the inner cores of neutron stars occurs in new QCD phases at large densities, with the vacuum energy appearing in the equation of state for a new phase. This in turn leads to a change in the internal structure of neutron stars and influences their tidal deformabilities which are measurable in the chirp signals of merging neutron stars. By considering three commonly used neutron star models we show that for large chirp masses the effect of vacuum energy on the tidal deformabilities can be sizable. Measurements of this sort have the potential to provide a first test of the gravitational properties of vacuum energy independent from the acceleration of the Universe, and to determine the size of QCD contributions to the vacuum energy.

    ↳ astro-ph.HEhep-phnucl-thJHEP(2018)·28 citations
  4. 09

    Hadronic Paschen-Back effect

    Sachio Iwasaki🇯🇵 · Makoto Oka🇯🇵 · Kei Suzuki🇯🇵 · Tetsuya Yoshida🇯🇵

    We find a novel phenomenon induced by the interplay between a strong magnetic field and finite orbital angular momenta in hadronic systems, which is analogous to the Paschen-Back effect observed in the field of atomic physics. This effect allows the wave functions to drastically deform. We discuss anisotropic decay from the deformation as a possibility to measure the strength of the magnetic field in heavy-ion collision at LHC, RHIC and SPS, which has not experimentally been measured. As an example we investigate charmonia with a finite orbital angular momentum in a strong magnetic field. We calculate the mass spectra and mixing rates. To obtain anisotropic wave functions, we apply the cylindrical Gaussian expansion method, where the Gaussian bases to expand the wave functions have different widths along transverse and longitudinal directions in the cylindrical coordinate.

    ↳ hep-phhep-exnucl-exnucl-th+1PLB(2019)·17 citations
  5. 10

    The relativistic chiral Lagrangian for decuplet and octet baryons at next-to-leading order

    Måns Holmberg🇸🇪 · Stefan Leupold (Uppsala U.)🇸🇪

    A complete and minimal relativistic Lagrangian is constructed at next-to-leading order for SU(3) chiral perturbation theory in the presence of baryon octet and baryon decuplet states. The Lagrangian has 13 terms for the pure decuplet sector, 6 terms for the transition sector from baryon octet to decuplet and (as already known from the literature) 16 terms for the pure octet sector. The minimal field content of 25 of these terms is meson-baryon four-point interactions. 3 terms give rise to the mass splitting for baryon octet and decuplet states, respectively. 2 terms give rise to overall mass shifts. 4 terms provide anomalous magnetic moments and a decuplet-to-octet magnetic transition moment. 1 term leads to an axial vector transition moment. It is shown that meson-baryon three-point coupling constants come in at leading order whereas no additional one appears in the minimal Lagrangian at next-to-leading order. Those low-energy constants that give rise to mass splitting and magnetic moments, respectively, are determined. Predictions are provided for radiative decays of decuplet to octet baryons.

    ↳ hep-phnucl-thEPJA(2018)·36 citations
  6. 11

    First Extraction of Transversity from a Global Analysis of Electron-Proton and Proton-Proton Data

    Marco Radici🇮🇹 · Alessandro Bacchetta🇮🇹

    We present the first extraction of the transversity distribution in the framework of collinear factorization based on the global analysis of pion-pair production in deep-inelastic scattering off transversely polarized targets and in proton-proton collisions with one transversely polarized proton. The extraction relies on the knowledge of di-hadron fragmentation functions, which are taken from the analysis of electron-positron annihilation data. For the first time, the chiral-odd transversity is extracted from a global analysis similar to what is usually done for the chiral-even spin-averaged and helicity distributions. The knowledge of transversity is important for, among other things, detecting possible signals of new physics in high-precision low-energy experiments.

    ↳ hep-phhep-exnucl-exnucl-thPRL(2018)·145 citations

Affiliations

first authorsco-authorsvia INSPIRE