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Nuclear Theory·nucl-th

Tuesday·June 25, 2019

9 papers—4 primary·5 cross-listed

All9Primary4Cross-lists5
  1. 05

    [Submitted on 21 Jun 2019] (cross-list from hep-ph)

    Aspects of heavy flavor jet physics in heavy ion collisions

    Ivan Vitev🇺🇸

    n these proceedings I discuss several recent developments in the physics of heavy flavor jets in heavy ion collisions. i) The dijet mass modification in nucleus-nucleus reactions has been proposed as a new observable with enhanced sensitivity to parton energy loss in nuclear matter. It also enables more precise studies of heavy quark mass effects on parton shower formation. ii) Computational techniques from soft-collinear effective theory have allowed us to bridge the gap between high energy and heavy ion QCD phenomenology. I show the first application of the semi-inclusive jet function formalism to heavy flavor jet production in proton-nucleus and nucleus-nucleus collisions at the LHC. iii) Last but not least, central to the theoretical calculations of heavy flavor jets is the accurate theoretical description of in-medium parton showers. A formalism to compute branching processes in nuclear matter to any desired order in opacity has been developed and illustrative numerical results are presented.

    Comments:
    6 pages, 6 figures. Proceedings of 13th International Workshop in High pT Physics in the RHIC and LHC Era
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1906.09276 [pdf]
    PoS(2020)·1 citation
  2. 06

    [Submitted on 21 Jun 2019] (cross-list from hep-ph)

    Perspectives of photon physics at future colliders

    M. Klasen🇩🇪

    We review current results on physics with photons at the LHC and discuss realistic perspectives of photon physics at future colliders. In particular, we focus on Standard Model (SM) measurements with photons at the upcoming high-luminosity and a possible high-energy LHC as well as jet measurements at an Electron-Ion Collider (EIC) to be constructed either at BNL or at JLAB and their potential to constrain nuclear parton densities. We also discuss future searches for physics beyond the SM with photons in the high-luminosity phase of the LHC.

    Comments:
    11 pages, 8 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1906.09280 [pdf]
    Frascati Phys.Ser.(2019)·3 citations
  3. 07

    [Submitted on 24 Jun 2019] (cross-list from hep-ph)

    Prompt -pair production at the LHC: impact of loop-induced contributions and of the colour-octet mechanism

    Jean-Philippe Lansberg🇫🇷 · Hua-Sheng Shao🇫🇷 · Nodoka Yamanaka🇫🇷 · Yu-Jie Zhang🇨🇳

    Prompt double- production at high-energy hadron colliders can be considered as a golden channel to probe double parton scatterings (DPS) --in particular to study gluon-gluon correlations inside the proton-- and, at the same time, to measure the distribution of linearly-polarised gluons inside the proton. Such studies however require a good control of both single and DPS in the respective regions where they are carried out. In this context, we have critically examined two mechanisms of single parton scatterings (SPS) that may be kinematically enhanced where DPS are thought to be dominant, even though they are either at higher orders in the strong-coupling or velocity expansion. First, we have considered a gauge-invariant and infrared-safe subset of the loop-induced contribution via Colour-Singlet (CS) transitions. We have found it to become the leading CS SPS contributions at large rapidity separation, yet too small to account for the data without invoking the presence of DPS yields. Second, we have surveyed the possible Colour-Octet (CO) contributions using both old and up-to-date non-perturbative long distance matrix elements (LDMEs). We have found that the pure CO yields crucially depend on the LDMEs. Among all the LDMEs we used, only two result into a visible modification of the NRQCD (CS+CO) yield, but only in two kinematical distributions measured by ATLAS, those of the rapidity separation and of the pair invariant mass. These modifications however do not impact the control region used for their DPS study.

    Comments:
    32 pages, 21 figures, 3 tables
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1906.10049 [pdf]
    EPJC(2019)·29 citations
  4. 08

    [Submitted on 24 Jun 2019] (cross-list from math-ph)

    Relativistic invariance in Euclidean formulations of quantum mechanics

    Gohin Shaikh Samad🇺🇸 · Wayne Polyzou🇺🇸

    Relativistic invariance in Euclidean formulations of quantum mechanics is discussed. Relativistic treatments of quantum theory are needed to study hadronic systems at sub-hadronic distance scales. Euclidean formulations of relativistic quantum mechanics have some computational advantages. In the Euclidean representation the physical Hilbert space inner product is expressed in terms of Euclidean space-time variables with no need for any analytic continuation. The identification of the complex Euclidean group with the complex Poincaré group relates the infinitesimal generators of both groups. In this work explicit representations of the Poincaré generators in Euclidean space-time variables for all positive-mass positive-energy irreducible representations of the Poincaré group are derived. The commutation relations are checked, both hermiticity and self-adjointness are established, and reflection positivity of the kernels is verified.

    Comments:
    23 pages
    Subjects:
    Mathematical Physics (math-ph); High Energy Physics — Theory (hep-th); math.MP (math.MP); Nuclear Theory (nucl-th)
    arXiv:
    1906.10083 [pdf]
    0 citations
  5. 09

    [Submitted on 24 Jun 2019] (cross-list from cond-mat.quant-gas)

    The contact in the unitary Fermi gas across the superfluid phase transition

    S. Jensen🇺🇸 · C. N. Gilbreth🇺🇸 · Y. Alhassid🇺🇸

    A quantity known as the contact plays a fundamental role in quantum many-body systems with short-range interactions. The determination of the temperature dependence of the contact for the unitary Fermi gas of infinite scattering length has been a major challenge, with different calculations yielding qualitatively different results. Here we use finite-temperature auxiliary-field quantum Monte Carlo (AFMC) methods on the lattice within the canonical ensemble to calculate the temperature dependence of the contact for the homogeneous spin-balanced unitary Fermi gas. We extrapolate to the continuum limit for 40, 66, and 114 particles. We observe a dramatic decrease in the contact as the superfluid critical temperature is approached from below, followed by a gradual weak decrease as the temperature increases in the normal phase. Our results are in excellent agreement with the most recent precision ultracold atomic gas experiments. We also present results for the energy of the unitary gas as a function of temperature in the continuum limit.

    Comments:
    6 pages, 2 figures, and 4 pages, 5 figures of supplemental material
    Subjects:
    Quantum Gases (cond-mat.quant-gas); Superconductivity (cond-mat.supr-con); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1906.10117 [pdf]
    PRL(2020)·26 citations

Affiliations

first authorsco-authorsvia INSPIRE