Nuclear Theory·nucl-th

Tuesday·April 2, 2019

23 papers—13 primary·10 cross-listed

14
Nuclear Parton Distributions from Lepton-Nucleus Scattering and the Impact of an Electron-Ion Collider
Rabah Abdul Khalek🇳🇱 · Jacob J. Ethier🇳🇱 · Juan Rojo🇳🇱
We present a first determination of the nuclear parton distribution functions (nPDF) based on the NNPDF methodology: nNNPDF1.0. This analysis is based on neutral-current deep-inelastic structure function data and is performed up to NNLO in QCD calculations with heavy quark mass effects. For the first time in the NNPDF fits, the $χ^{2}$ minimization is achieved using stochastic gradient descent with reverse-mode automatic differentiation (backpropagation). We validate the robustness of the fitting methodology through closure tests, assess the perturbative stability of the resulting nPDFs, and compare them with other recent analyses. The nNNPDF1.0 distributions satisfy the boundary condition whereby the NNPDF3.1 proton PDF central values and uncertainties are reproduced at $A = 1$ , which introduces important constraints particularly for low- $A$ nuclei. We also investigate the information that would be provided by an Electron-Ion Collider (EIC), finding that EIC measurements would significantly constrain the nPDFs down to $x ≃ 5 \times 1 0^{- 4}$ . Our results represent the first-ever nPDF determination obtained using a Monte Carlo methodology consistent with that of state-of-the-art proton PDF fits, and provide the foundation for a subsequent global nPDF analyses including also proton-nucleus data.
↳ hep-phhep-exnucl-exnucl-thEPJC(2019)·147 citations
15
Charting the coming synergy between lattice QCD and high-energy phenomenology
T. J. Hobbs🇺🇸 · Bo-Ting Wang🇺🇸 · Pavel M. Nadolsky🇺🇸 · Fredrick I. Olness🇺🇸
Building upon the PDFSense framework developed in Ref. [1], we perform a comprehensive analysis of the sensitivity of present and future high-energy data to a number of quantities commonly evaluated in lattice gauge theory, with a particular focus on the integrated Mellin moments of nucleon parton distribution functions (PDFs), such as $⟨ x ⟩_{u^{+} - d^{+}}$ and $⟨ x ⟩_{g}$ , as well as $x$ -dependent quark quasi-distributions -- in particular, that of the isovector combination. Our results demonstrate the potential for lattice calculations and phenomenological quark distributions informed by high-energy experimental data to cooperatively improve the picture of the nucleon's collinear structure. This will increasingly be the case as computational resources for lattice calculations further expand, and QCD global analyses continue to grow in sophistication. Our sensitivity analysis suggests that a future lepton-hadron collider would be especially instrumental in providing phenomenological constraints to lattice observables.
↳ hep-phhep-exhep-latnucl-thPRD(2019)·45 citations
16
Meson-meson scattering lengths at maximum isospin from lattice QCD
Christopher Helmes🇩🇪 · Christian Jost🇩🇪 · Bastian Knippschild🇩🇪 · Bartosz Kostrzewa🇩🇪 · Liuming Liu🇨🇳 · Ferenc Pittler🇩🇪 · Carsten Urbach🇩🇪 · Markus Werner🇩🇪
We summarize our lattice QCD determinations of the pion-pion, pion-kaon and kaon-kaon s-wave scattering lengths at maximal isospin with a particular focus on the extrapolation to the physical point and the usage of next-to-leading order chiral perturbation theory to do so. We employ data at three values of the lattice spacing and pion masses ranging from around 230 MeV to around 450 MeV, applying Luescher's finite volume method to compute the scattering lengths. We find that leading order chiral perturbation theory is surprisingly close to our data even in the kaon-kaon case for our entire range of pion masses.
↳ hep-lathep-phnucl-thPoS(2019)·5 citations
17
Anisotropic pressure induced by finite-size effects in SU(3) Yang-Mills theory
Masakiyo Kitazawa🇯🇵 · Sylvain Mogliacci🇿🇦 · Isobel Kolbé🇿🇦 · W. A. Horowitz🇿🇦
We study the pressure anisotropy in anisotropic finite-size systems in SU(3) Yang-Mills theory at nonzero temperature. Lattice simulations are performed on lattices with anisotropic spatial volumes with periodic boundary conditions. The energy-momentum tensor defined through the gradient flow is used for the analysis of the stress tensor on the lattice. We find that a clear finite-size effect in the pressure anisotropy is observed only at a significantly shorter spatial extent compared with the free scalar theory, even when accounting for a rather large mass in the latter.
↳ hep-lathep-phnucl-thPRD(2019)·40 citations
18
The non-equilibrium attractor: Beyond hydrodynamics
Michael Strickland🇺🇸
The quark-gluon plasma created in heavy-ion collisions is not in local thermal equilibrium at early times. Despite this, dissipative hydrodynamics describes the evolution of the energy-momentum tensor quite well after only roughly 0.5 - 1 fm/c. This can be understood using the concept of a non-equilibrium dynamical attractor. The attractor is a uniquely identifiable solution to the dynamical equations to which all solutions are drawn as the system evolves. Once solutions collapse onto the non-equilibrium attractor they are ``pseudo-thermalized'' in the sense that they have lost information about the precise initial conditions used, but are not yet in exact local thermal equilibrium. Here I review recent work which demonstrates that there exists a non-equilibrium attractor in full kinetic theory models which goes beyond the usual low-order momentum moments considered in hydrodynamical treatments.
↳ hep-phnucl-thActa Phys.Polon.B(2019)·6 citations
19
Charmed dibaryon resonances in the potential quark model
Makoto Oka🇯🇵 · Saori Maeda🇯🇵 · Yan-Rui Liu🇨🇳
Charmed dibaryon states with the spin-parity $J^{π} = 0^{+}$ , $1^{+}$ , and $2^{+}$ are predicted for the two-body $Y_{c} N$ ( $= Λ_{c}$ , $Σ_{c}$ , or $Σ_{c}^{*}$ ) systems. We employ the complex scaling method for the coupled channel Hamiltonian with the $Y_{c} N$ -CTNN potentials, which were proposed in our previous study. We find four sharp resonance states near the $Σ_{c} N$ and $Σ_{c}^{*} N$ thresholds. From the analysis of the binding energies of partial channel systems, we conclude that these resonance states are Feshbach resonances. We compare the results with the $Y_{c} N$ resonance states in the heavy quark limit, where the $Σ_{c} N$ and $Σ_{c}^{*} N$ thresholds are degenerate, and find that they form two pairs of the heavy-quark doublets in agreement with the heavy quark spin symmetry.
↳ hep-phnucl-thInt.J.Mod.Phys.Conf.Ser.(2019)·8 citations
20
Heavy quark spin multiplet structure of $P_{c} (4312)$ , $P_{c} (4440)$ , and $P_{c} (4457)$
Yuki Shimizu🇯🇵 · Yasuhiro Yamaguchi🇯🇵 · Masayasu Harada🇯🇵
Very recently, the LHCb collaboration has reported the new result about the hidden-charm pentaquarks: $P_{c} (4312)$ near the $D ˉ Σ_{c}$ threshold, and $P_{c} (4440)$ and $P_{c} (4457)$ near $D ˉ^{*} Σ_{c}$ threshold. We study the heavy quark spin (HQS) multiplet structures of these newly $P_{c}$ pentaquarks under the heavy quark spin symmetry based on the hadronic molecular picture. We point out that $P_{c} (4312)$ is the $J^{P} = 1/ 2^{-}$ member of an HQS triplet, and $P_{c} (4440)$ and $P_{c} (4457)$ are the $J^{P} = 3/ 2^{-}$ member of the HQS triplet and an HQS singlet with $J^{P} = 3/ 2^{-}$ . Namely, the $P_{c} (4312)$ and one of $P_{c} (4440)$ and $P_{c} (4457)$ belong to an HQS triplet. The HQS multiplet structure predicts the existence of $J^{P} = 5/ 2^{-}$ state near $D ˉ^{*} Σ_{c}^{*}$ threshold.
↳ hep-phnucl-th67 citations
21
Nature of the D_0 meson in the D pi scattering with chiral symmetry
Takumi Sugiura🇯🇵 · Tetsuo Hyodo🇯🇵
We study the nature of the scalar D_0 meson from the viewpoint of chiral symmetry. With the linear representation of chiral symmetry, we construct the D pi scattering amplitude satisfying the chiral low-energy theorem, in which the D_0 meson appears as an s-wave resonance. We show that the properties of the D_0 meson can be successfully reproduced as the chiral partner of the D meson coupled with the D pi scattering states. At the same time, we find that the spectral function and the pole position of D_0 are not very sensitive to the reduction of the chiral condensate, indicating the importance of the dressing of the bare state by the D pi molecular component.
↳ hep-phnucl-thPRC(2019)·3 citations
22
Unequal rapidity correlators in the dilute limit of JIMWLK
Tuomas Lappi🇫🇮 · Andrecia Ramnath🇫🇮
We study unequal rapidity correlators in the stochastic Langevin picture of Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner (JIMWLK) evolution in the Color Glass Condensate effective field theory. We discuss a diagrammatic interpretation of the long-range correlators. By separately evolving the Wilson lines in the direct and complex conjugate amplitudes, we use the formalism to study two-particle production at large rapidity separations. We show that the evolution between the rapidities of the two produced particles can be expressed as a linear equation, even in the full nonlinear limit. We also show how the Langevin formalism for two-particle correlations reduces to a BFKL picture in the dilute limit and in momentum space, providing an interpretation of BFKL evolution as a stochastic process for color charges.
↳ hep-phnucl-thPRD(2019)·5 citations
23
Complete Matching for Quasi-distribution Functions in Large Momentum Effective Theory
Wei Wang🇨🇳 · Jian-Hui Zhang🇩🇪 · Shuai Zhao🇨🇳 · Ruilin Zhu🇨🇳
We complete the procedure of extracting parton distribution functions (PDFs) using large momentum effective theory (LaMET) at leading power accuracy in the hadron momentum. We derive a general factorization formula for the quasi PDFs in the presence of mixing, and give the corresponding hard matching kernel at $O (α_{s})$ , both for the unpolarized and for the polarized quark and gluon quasi-PDFs. Our calculation is performed in a regularization-independent momentum subtraction scheme. The results allow us to match the nonperturbatively renormalized quasi-PDFs to normal PDFs in the presence of mixing, and therefore can be used to extract flavor-singlet quark PDFs as well as gluon PDFs from lattice simulations.
↳ hep-phhep-latnucl-thPRD(2019)·86 citations

Affiliations

first authorsco-authorsvia INSPIRE