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Nuclear Theory·nucl-th

Thursday·August 13, 2020

9 papers—2 primary·7 cross-listed

All9Primary2Cross-lists7
  1. 03

    Medium-induced fragmentation and equilibration of highly energetic partons

    Soeren Schlichting🇩🇪 · Ismail Soudi🇩🇪

    We investigate the energy loss and equilibration of highly energetic particles/jets inside a QCD medium. Based on an effective kinetic description of QCD, including elastic processes, radiative processes, as well as the back-reaction of jet constituents onto the thermal medium, we describe the in-medium evolution of jets from the energy scale of the jet all the way to the medium scale . While elastic processes and back-reaction are important to describe the equilibration of soft fragments of the jet, we find that the energy loss is dominated by an inverse turbulent cascade due to successive radiative branchings, which has interesting implications for the energy spectra and chemistry of jet fragments.

    ↳ hep-phnucl-thJHEP(2021)·53 citations
  2. 04

    Improving Hamiltonian encodings with the Gray code

    Olivia Di Matteo🇨🇦 · Anna McCoy🇨🇦 · Peter Gysbers🇨🇦 · Takayuki Miyagi🇨🇦 · R. M. Woloshyn🇨🇦 · Petr Navrátil🇨🇦

    Due to the limitations of present-day quantum hardware, it is especially critical to design algorithms that make the best possible use of available resources. When simulating quantum many-body systems on a quantum computer, straightforward encodings that transform many-body Hamiltonians into qubit Hamiltonians use of the available basis states of an -qubit system, whereas are in theory available. We explore an efficient encoding that uses the entire set of basis states, where terms in the Hamiltonian are mapped to qubit operators with a Hamiltonian that acts on the basis states in Gray code order. This encoding is applied to the commonly-studied problem of finding the ground state energy of a deuteron with a simulated variational quantum eigensolver (VQE). It is compared to a standard "one-hot" encoding, and various trade-offs that arise are analyzed. The energy distribution of VQE solutions has smaller variance than the one obtained by the one-hot encoding even in the presence of simulated hardware noise, despite an increase in the number of measurements. The reduced number of qubits and a shorter-depth variational ansatz enables the encoding of larger problems on current-generation machines. This encoding also demonstrates improvements for simulating time evolution of the same system, producing circuits for the evolution operators with reduced depth and roughly half the number of gates compared to a one-hot encoding.

    ↳ quant-phnucl-thPRA(2021)·90 citations
  3. 05

    Ultra-peripheral nuclear collisions as a source of heavy quarkonia

    B. Z. Kopeliovich🇨🇱 · M. Krelina🇨🇿 · J. Nemchik🇨🇿 · I. K. Potashnikova🇨🇱

    Heavy quarkonium production in ultra-peripheral nuclear collisions (UPC) is described within the QCD dipole formalism. Realistic quarkonium wave functions in the rest frame are calculated by solving the Schrödinger equation with a subsequent Lorentz boost to high energy. We rely on several realistic potentials, which allow to describe well the quarkonium masses and decay widths, as well as data on diffractive electroproduction of quarkonia on protons. Nuclear effects are calculated with the phenomenological dipole cross sections fitted to DIS data. The higher twist quark shadowing related to the lowest Fock component of the photon, as well as the leading twist gluon shadowing, related to higher components containing gluons, are included. The results for coherent and incoherent photoproduction of charmonia and bottomonia in UPC of heavy nuclei are in good accord with available data from the LHC. They can also be verified in future experiments at electron-ion colliders.

    ↳ hep-phnucl-thPRD(2023)·33 citations
  4. 06

    Parity violation in proton-deuteron scattering

    A.I. Milstein🇷🇺 · N.N. Nikolaev🇷🇺 · S.G. Salnikov🇷🇺

    The effects of parity violation in the interaction of relativistic polarized protons and deuterons are discussed. Within Glauber's approach, estimates are obtained for P-odd asymmetries in the total and elastic scattering cross sections, in the deuteron dissociation cross section, and in the inelastic cross section with meson production in a final state. It is shown that, from the point of view of the magnitude of the P-odd effects, the interaction of polarized deuterons with unpolarized protons has an advantage over the interaction of polarized protons with unpolarized deuterons. A significant P-odd asymmetry was found in the dissociation channel of the polarized deuteron.

    ↳ hep-phnucl-thJETP Lett.(2020)·4 citations
  5. 07

    Dipole model at Next-to-Leading Order meets HERA data

    G. Beuf🇫🇮 · H. Hänninen🇫🇮 · T. Lappi🇫🇮 · H. Mäntysaari🇫🇮

    Deep inelastic scattering (DIS) total cross section data at small-x as measured by the HERA experiments is well described by Balitsky-Kovchegov (BK) evolution in the leading order dipole picture. Recently the full Next-to-Leading Order (NLO) dipole picture total cross sections have become available for DIS, and a working factorization scheme has been devised which subtracts the soft gluon divergence present at NLO. We report our recently published work in which we make the first comparisons of the NLO DIS total cross sections to HERA data. The non-perturbative initial condition to BK evolution is fixed by fitting the HERA reduced cross section data. As the NLO results for the DIS total cross section are currently available only in the massless quark limit, we also fit a light-quark-only cross section constructed with a parametrization of published total and heavy quark data. We find an excellent description of the HERA data. Since the full NLO BK equation is computationally expensive, we use a number of beyond LO prescriptions for the evolution that include most important higher order corrections enhanced by large transverse logarithms, including the recent version of the equation formulated in terms of the target momentum fraction.

    ↳ hep-phnucl-thPoS(2021)·3 citations
  6. 08

    Transverse moments of TMD parton densities and ultraviolet divergences

    Ted Rogers🇺🇸

    I review some open questions relating to the large transverse momentum divergences in transverse moments of transverse momentum dependent (TMD) parton correlation func- tions. I also explain, in an abbreviated and summarized form, recent work that shows that the resulting violations of a commonly used integral relation are not perturbatively suppressed. I argue that this implies a need for more precise definitions for the correlation functions used to describe transverse moments.

    ↳ hep-phhep-exnucl-thMod.Phys.Lett.A(2020)·9 citations
  7. 09

    The Sivers Asymmetry in Hadronic Dijet Production

    Zhong-Bo Kang🇺🇸 · Kyle Lee🇺🇸 · Ding Yu Shao🇺🇸 · John Terry🇺🇸

    We study the single spin asymmetry in the back-to-back dijet production in transversely polarized proton-proton collisions. Such an asymmetry is generated by the Sivers functions in the incoming polarized proton. We propose a QCD formalism in terms of the transverse momentum dependent parton distribution functions, which allow us to resum the large logarithms that arise in the perturbative calculations. We make predictions for the Sivers asymmetry of hadronic dijet production at the kinematic region that is relevant to the experiment at the Relativistic Heavy Ion Collider (RHIC). We further compute the spin asymmetries in the selected positive and negative jet charge bins, to separate the contributions from - and -quark Sivers functions. We find that both the sign and size of our numerical results are roughly consistent with the preliminary results from the STAR collaboration at the RHIC.

    ↳ hep-phhep-exnucl-exnucl-thJHEP(2021)·27 citations

Affiliations

first authorsco-authorsvia INSPIRE