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Nuclear Theory·nucl-th

Tuesday·April 13, 2021

12 papers—7 primary·5 cross-listed

All12Primary7Cross-lists5
  1. 08

    Pion form factor from an AdS deformed background

    Miguel Angel Martin Contreras🇨🇱 · Eduardo Folco Capossoli🇧🇷 · Danning Li🇨🇳 · Alfredo Vega🇨🇱 · Henrique Boschi-Filho🇧🇷

    We consider a bottom-up AdS/QCD model with a conformal exponential deformation on a Lorentz invariant AdS background. In this model, we assume the conformal dimension associated with the operator that creates pions at the boundary as . Regarding the infrared scale related to photon field , we analyze two cases: constant and depending on the transferred momentum . In these two cases, we computed the electromagnetic pion form factor as well as the pion radius. We compare our results with experimental data as well as other theoretical (holographic and non-holographic) models. In particular, for the momentum-dependent infrared scale, we find good agreement with the available experimental data as well as non-holographic models.

    ↳ hep-phhep-thnucl-thNPB(2022)·21 citations
  2. 09

    Nonanalyticity, sign problem and Polyakov line in Z3-symmetric heavy quark model at low temperature: Phenomenological model analyses

    Hiroaki Kouno🇯🇵 · Kouji Kashiwa🇯🇵 · Takehiro Hirakida🇯🇵

    The nonanalyticity and the sign problem in the Z3-symmetric heavy quark model at low temperature are studied phenomenologically. For the free heavy quarks, the nonanalyticity is analyzed in the relation to the zeros of the grand canonical partition function. The Z3-symmetric effective Polyakov-line model (EPLM) in strong coupling limit is also considered as an phenomenological model of Z3-symmetric QCD with large quark mass at low temperature. We examine how the Z3-symmetric EPLM approaches to the original one in the zero-temperature limit. The effects of the Z3-symmetry affect the structure of zeros of the microscopic probability density function at the nonanalytic point. The average value of the Polyakov line can detect the structure, while the other thermodynamic quantities are not sensible to the structure in the zero-temperature limit. The effect of the imaginary quark chemical potential is also discussed. The imaginary part of the quark number density is very sensitive to the symmetry structure at the nonanalytical point. For a particular value of the imaginary quark number chemical potential, large quark number may be induced in the vicinity of the nonanalytical point.

    ↳ hep-phhep-latnucl-thPRD(2021)·1 citation
  4. 11

    Detailed analysis of excited state systematics in a lattice QCD calculation of

    Jinchen He🇨🇳 · David A. Brantley🇺🇸 · Chia Cheng Chang🇯🇵 · Ivan Chernyshev🇺🇸 · Evan Berkowitz🇺🇸 · Dean Howarth🇺🇸 · Christopher Körber🇺🇸 · Aaron S. Meyer🇺🇸 · Henry Monge-Camacho🇺🇸 · Enrico Rinaldi🇺🇸 · Chris Bouchard🇬🇧 · M.A. Clark🇺🇸 and 5 other authors

    Excited state contamination remains one of the most challenging sources of systematic uncertainty to control in lattice QCD calculations of nucleon matrix elements and form factors: early time separations are contaminated by excited states and late times suffer from an exponentially bad signal-to-noise problem. High-statistics calculations at large time separations fm are commonly used to combat these issues. In this work, focusing on , we explore the alternative strategy of utilizing a large number of relatively low-statistics calculations at short to medium time separations (0.2--1 fm), combined with a multi-state analysis. On an ensemble with a pion mass of approximately 310 MeV and a lattice spacing of approximately 0.09 fm, we find this provides a more robust and economical method of quantifying and controlling the excited state systematic uncertainty. A quantitative separation of various types of excited states enables the identification of the transition matrix elements as the dominant contamination. The excited state contamination of the Feynman-Hellmann correlation function is found to reduce to the 1% level at approximately 1 fm while for the more standard three-point functions, this does not occur until after 2 fm. Critical to our findings is the use of a global minimization, rather than fixing the spectrum from the two-point functions and using them as input to the three-point analysis. We find that the ground state parameters determined in such a global analysis are stable against variations in the excited state model, the number of excited states, and the truncation of early-time or late-time numerical data.

    ↳ hep-lathep-phnucl-thPRC(2022)·23 citations
  5. 12

    Electromagnetic transition form factors and Dalitz decays of hyperons

    Stefan Leupold (Uppsala U.)🇸🇪 · Nora Salone (Uppsala U. and NCBJ, Warsaw)🇸🇪

    Dalitz decays of a hyperon resonance to a ground-state hyperon and an electron-positron pair can give access to some information about the composite structure of hyperons. We present expressions for the multi-differential decay rates in terms of general transition form factors for spin-parity combinations J^P = 1/2^+/-, 3/2^+/- of the hyperon resonance. Even if the spin of the initial hyperon resonance is not measured, the self-analyzing weak decay of the "final" ground-state hyperon contains information about the relative phase between combinations of transition form factors. This relative phase is non-vanishing because of the unstable nature of the hyperon resonance. If all form factor combinations in the differential decay formulae are replaced by their respective values at the photon point, one obtains a QED type approximation, which might be interpreted as characterizing hypothetical hyperons with point-like structure. We compare the QED type approximation to a more realistic form factor scenario for the lowest-lying singly-strange hyperon resonances. In this way we explore which accuracy in the measurements of the differential Dalitz decay rates is required in order to distinguish the composite-structure case from the pointlike case. Based on the QED type approximation we obtain as a by-product a rough prediction for the ratio between the Dalitz decay width and the corresponding photon decay width.

    ↳ hep-phnucl-thEPJA(2021)·11 citations

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first authorsco-authorsvia INSPIRE