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Nuclear Theory·nucl-th

Monday·November 13, 2017

7 papers—5 primary·2 cross-listed

All7Primary5Cross-lists2
  1. 06

    [Submitted on 10 Nov 2017] (cross-list from physics.atom-ph)

    Probing "long-range" neutrino-mediated forces with atomic and nuclear spectroscopy

    Yevgeny V. Stadnik

    The exchange of a pair of low-mass neutrinos between electrons, protons and neutrons produces a "long-range" potential, which can be sought for in phenomena originating on the atomic and sub-atomic length scales. We calculate the effects of neutrino-pair exchange on transition and binding energies in atoms and nuclei. In the case of atomic s-wave states, there is a large enhancement of the induced energy shifts due to the lack of a centrifugal barrier and the highly singular nature of the neutrino-mediated potential. We derive limits on neutrino-mediated forces from measurements of the deuteron binding energy and transition energies in positronium, muonium, hydrogen and deuterium, as well as isotope-shift measurements in calcium ions. Our limits improve on existing constraints on neutrino-mediated forces from experiments that search for new macroscopic forces by 18 orders of magnitude. Future spectroscopy experiments have the potential to probe long-range forces mediated by the exchange of pairs of standard-model neutrinos and other weakly-charged particles.

    Comments:
    6 pages, 1 figure, version accepted to PRL
    Subjects:
    Atomic Physics (physics.atom-ph); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1711.03700 [pdf]
    PRL(2018)·57 citations
  2. 07

    [Submitted on 10 Nov 2017] (cross-list from hep-ph)

    Quantum Chromodynamics at small Bjorken-x

    Pieter Taels🇧🇪

    With the advent of very powerful particle accelerators, such as RHIC and the LHC, it becomes possible to study QCD in high energy collisions, in which the gluon content of the proton or nucleus is probed and its density becomes often large enough for nonlinear effects to play a role. This small-x regime of QCD is well described by an effective theory known as the Color Glass Condensate (CGC). In this thesis, we introduce the CGC and apply it to two different problems. First, we use the CGC to study forward heavy-quark production in pA collisions. When the quarks are nearly back-to-back, the CGC result coincides with the one in the TMD factorization approach. This allows us to extract the small-x limit of the Weizsäcker-Williams gluon distribution, as well as the dipole distribution and one extra gluon TMD. Each of these gluon TMDs is accompanied by a partner, which couples via the quark mass and which describes the linearly polarized gluon content of the unpolarized nucleus. We calculate the six resulting gluon TMDs analytically in the MV model, and evolve them in rapidity using a numerical implementation of JIMWLK. The second problem is situated within heavy-ion physics. Jets, produced in the scattering of two nuclei, travel through the Quark-Gluon Plasma (QGP) before reaching the detector, and are attenuated as a result of their interaction with this medium. This phenomenon, known as jet quenching, is one of the main probes to investigate the QGP. We focus on the transverse momentum broadening of a hard particle traveling through a nuclear medium, and employ small-x techniques to attempt to resum the leading logarithmic corrections due to soft gluon radiation. Although, ultimately, we can only solve the resulting in-medium evolution equation to DLA accuracy, we do present a concise framework for the problem, and draw a detailed comparison with the CGC and with the literature.

    Comments:
    PhD thesis, defended at the University of Antwerp, Belgium, on July 3, 2017
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1711.03928 [pdf]
    8 citations

Affiliations

first authorsco-authorsvia INSPIRE