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Nuclear Theory·nucl-th

Wednesday·August 26, 2020

9 papers—2 primary·7 cross-listed

All9Primary2Cross-lists7
  1. 03

    [Submitted on 24 Aug 2020] (cross-list from hep-ph)

    QCD Beyond Leading Power

    Gherardo Vita🇺🇸

    In this thesis I study the infrared limits of QCD beyond leading power by developing effective quantum field theory techniques. I introduce the motivations for studying this subject both as a tool to deepen our understanding of the infrared structure of gauge theory amplitudes and cross sections in the soft, collinear and Regge limit as well as to improve predictions for collider observables. Using and extending the framework of Soft and Collinear Effective Theory (SCET), I explore the ingredients of factorization beyond leading power constructing subleading hard scattering operators and radiative jet and soft functions for processes such as Higgs production and Drell-Yan. I introduce new subleading power gauge invariant objects, the -jet and -soft functions, which arise in the renormalization of subleading power operators. I use them to achieve the first resummation of collinear and soft logarithms beyond leading power for a collider observable in QCD. I study the perturbative power corrections to differential distributions for color singlet production at the LHC retaining the full dependence on the kinematics of the color singlet. I highlight and solve the subtleties related to the regularization of rapidity divergences beyond leading power for which I propose a new regulator, the pure rapidity regulator. I present a new method to employ cutting edge multiloop techniques for the computation of the expansions of cross sections in the collinear limit. This allows the extraction of universal ingredients arising in the collinear limit of QCD to an unprecedented level of precision in perturbation theory. Finally, I study the Regge limit at the amplitude and cross section level beyond leading power, developing a Lagrangian formalism for the treatment of fermion mediated forward scattering processes in QCD and applying it to obtain the quark reggeization and BFKL resummation.

    Comments:
    Ph.D. thesis, MIT, 2020, 419 pages, very large number of figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2008.10606 [pdf]
    4 citations
  2. 04

    [Submitted on 24 Aug 2020] (cross-list from hep-ph)

    Energy of a point-like neutron in an external electromagnetic field

    Jesus Saenz🇺🇸 · Michael Engelhardt🇺🇸 · Roman Höllwieser🇺🇸

    A point-like neutron in an external electromagnetic field experiences a shift in energy that mimicks the effect of an actual structural deformation of an extended neutron, i.e., a proper polarizability. In order to be able to differentiate between the former and the latter, a Foldy-Wouthuysen transformation is constructed which yields the energy shift of a point-like neutron quadratic in the external field in a derivative expansion, generalizing a long-known result for the dipole electric polarizability due to Foldy. The ten leading Foldy contributions to the energy are determined for a zero-momentum neutron. In addition, eliminating the momentum operator in favor of the velocity operator, analogous results are derived for a zero-velocity neutron. In this case, operator ordering ambiguities are encountered that permit only a determination of eight of the ten Foldy terms.

    Comments:
    Version accepted for publication
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    2008.10691 [pdf]
    PRD(2021)·0 citations
  3. 05

    [Submitted on 24 Aug 2020] (cross-list from hep-ph)

    Regularizing thermo and magnetic contributions within nonrenormalizable theories

    Sidney S. Avancini🇧🇷 · Ricardo L. S. Farias🇧🇷 · Marcus B. Pinto🇧🇷 · Tulio E. Restrepo🇧🇷 · William R. Tavares🇧🇷

    The importance of implementing a proper regularization procedure in order to treat thermo and magnetic contributions within nonrenormalizable theories is investigated. Our study suggests that potential divergences should be isolated into the vacuum and purely magnetic contributions and then regularized while the convergent thermomagnetic contributions should be integrated over the full momentum range. This prescription is illustrated by applying the proper time formalism to the two flavor Polyakov--Nambu--Jona-Lasinio model, whose magnetic field dependent coupling has been recently determined. Observables such as the pressure, magnetization, speed of sound squared, and specific heat evaluated within our scheme are compared with results furnished by other three possible prescriptions. We show that these quantities display a thermomagnetic behavior which is physically more consistent when our scheme is adopted. In particular, we demonstrate that naively regulating the (entangled) vacuum, magnetic and thermomagnetic contributions leads to physically inconsistent results especially at the high temperature domain.

    Comments:
    18 pages, 8 figures, 2 tables
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2008.10720 [pdf]
    PRD(2021)·32 citations
  4. 06

    [Submitted on 24 Aug 2020] (cross-list from hep-ph)

    Magnetic field dependence of nucleon parameters from QCD sum rules

    C. A. Dominguez🇿🇦 · Luis A. Hernández🇿🇦 · Marcelo Loewe🇨🇱 · Cristian Villavicencio🇨🇱 · R. Zamora🇨🇱

    Finite energy QCD sum rules involving nucleon current correlators are used to determine several QCD and hadronic parameters in the presence of an external, uniform, large magnetic field. The continuum hadronic threshold , nucleon mass , current-nucleon coupling , transverse velocity , the spin polarization condensate , and the magnetic susceptibility of the quark condensate , are obtained for the case of protons and neutrons. Due to the magnetic field, and charge asymmetry of light quarks up and down, all the obtained quantities evolve differently with the magnetic field, for each nucleon or quark flavor. With this approach it is possible to obtain the evolution of the above parameters up to a magnetic field strength GeV.

    Comments:
    Note added in proof. Accepted for publication in Phys. Rev. D
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2008.10742 [pdf]
    PRD(2020)·16 citations
  5. 07

    [Submitted on 25 Aug 2020] (cross-list from hep-ph)

    Nuclear suppression from coherent photoproduction at the Large Hadron Collider

    V. Guzey🇷🇺 · E. Kryshen (St. Petersburg, INP)🇷🇺 · M. Strikman (Penn State U.)🇺🇸 · M. Zhalov (St. Petersburg, INP)🇷🇺

    Using the data on coherent photoproduction in Pb-Pb ultraperipheral collisions (UPCs) obtained in Runs 1 and 2 at the Large Hadron Collider (LHC), we determined with a good accuracy the nuclear suppression factor of in a wide range of the momentum fraction , . In the small- region , our fit favors a flat form of with approximately a 5% accuracy for and a 25% error at . At the same time, uncertainties of the fit do not exclude a slow decrease of in the small- limit. At large , is constrained to better than 10% precision up to and is also consistent with the value of at , which we extract from the Fermilab data on the dependence of the cross section of coherent photoproduction on fixed nuclear targets. The resulting uncertainties on are small, which indicates the potential of the LHC data on coherent charmonium photoproduction in Pb-Pb UPCs to provide additional constraints on small- nPDFs. We explicitly demonstrate this using as an example the EPPS16 and nCTEQ16 nuclear parton distribution functions, whose uncertainties decrease severalfold after the Bayesian reweighting of the discussed UPC data.

    Comments:
    18 pages, 3 figures, 3 tables. Revised and extended version including the Run 2 ALICE data at central rapidities and the effect of Bayesian reweighting of the UPC data on EPPS16 and nCTEQ15 nPDFs
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2008.10891 [pdf]
    PLB(2021)·47 citations
  6. 08

    [Submitted on 25 Aug 2020] (cross-list from astro-ph.HE)

    Finding quark content of neutron stars in light of GW170817

    Rana Nandi🇮🇳 · Subrata Pal🇮🇳

    The detection of gravitational waves from GW170817 has provided a new opportunity to constrain the equation of state (EOS) of neutron stars. In this article, we investigate the possible existence of quarks inside the neutron star core in the context of GW170817. The nucleon phase is treated within the relativistic nuclear mean-field approach where we have employed a fully comprehensive set of available models, and the quark phase is described in the Bag model. We show that the nucleonic EOSs which are inconsistent with the tidal deformability bound become consistent when phase transition to quark matter via Gibbs construction is allowed. We find that several nucleonic EOSs support the presence of pure quark matter core with a small mass not more than confined within a radius of 0.9 km. We also find that the strong correlation between tidal deformability and neutron star radii observed for pure nucleonic stars does persist even with a nucleon-quark phase transition and provides an upper limit on the radius of km for a neutron star.

    Comments:
    13 pages, 4 figures, to appear in EPJST
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    2008.10943 [pdf]
    Eur.Phys.J.ST(2021)·26 citations
  7. 09

    [Submitted on 25 Aug 2020] (cross-list from hep-lat)

    Nuclear matrix elements from lattice QCD for electroweak and beyond-Standard-Model processes

    Zohreh Davoudi🇺🇸 · William Detmold🇺🇸 · Kostas Orginos🇺🇸 · Assumpta Parreño🇺🇸 · Martin J. Savage🇪🇸 · Phiala Shanahan🇺🇸 · Michael L. Wagman🇺🇸

    Over the last decade, numerical solutions of Quantum Chromodynamics (QCD) using the technique of lattice QCD have developed to a point where they are beginning to connect fundamental aspects of nuclear physics to the underlying degrees of freedom of the Standard Model. In this review, the progress of lattice QCD studies of nuclear matrix elements of electroweak currents and beyond-Standard-Model operators is summarized, and connections with effective field theories and nuclear models are outlined. Lattice QCD calculations of nuclear matrix elements can provide guidance for low-energy nuclear reactions in astrophysics, dark matter direct detection experiments, and experimental searches for violations of the symmetries of the Standard Model, including searches for additional CP violation in the hadronic and leptonic sectors, baryon-number violation, and lepton-number or flavor violation. Similarly, important inputs to neutrino experiments seeking to determine the neutrino-mass hierarchy and oscillation parameters, as well as other electroweak and beyond-Standard-Model processes can be determined. The phenomenological implications of existing studies of electroweak and beyond-Standard-Model matrix elements in light nuclear systems are discussed, and future prospects for the field toward precision studies of these matrix elements are outlined.

    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2008.11160 [pdf]
    Phys.Rept.(2021)·96 citations

Affiliations

first authorsco-authorsvia INSPIRE