Nuclear Theory·nucl-th

Tuesday·January 23, 2024

15 papers—6 primary·9 cross-listed

07
$π$ - and $K$ -Mesons Properties for Large $N_{f}$
Aftab Ahmad🇵🇰
The restoration of dynamical chiral symmetry for a higher number of light-quark flavors $N_{f}$ implies suppression of the dynamically generated quark mass. The study of various larger values of $N_{f}$ may have a greater impact on the internal structure of light hadrons. In this work, we study the properties of the $π$ - (pion) and $K$ -meson (kaon), such as the mass, condensate, and leptonic decay constant, for various $N_{f}$ . We use the symmetry-preserving vector-vector flavor-dependent contact interaction model of quark. The dynamical quark masses are calculated using the Schwinger-Dyson equation (SDE). The masses of pion ( $m_{π}$ ) and kaon ( $m_{K}$ ) for different values of $N_{f}$ and are determined using the homogeneous Bethe-Salpeter equation. For fixed $N_{c} = 3$ and $N_{f}$ is increased, the dynamically generated quark mass $M_{u / d}$ ( mass of up and down quarks), strange quark mass ( $M_{s}$ ), meson in-condensate $κ_{(π, K)}^{1/3}$ , and decay constant $f_{(π, K)}$ . monotonically decrease as a function of $N_{f}$ , except for the pion and kaon mass $m_{(π, K)}$ , which increase above a critical value of $N_{f}$ around $8$ . This is the region where chiral symmetry is restored and the pion and kaon behave as free particles, similar to thier behavior in the the presence of a heat bath. The results obtained for fixed $N_{f} = 2$ and $N_{c} = 3$ are fairly in decent agreement with experimentally calculated statistics and previous model calculations based on the Schwinger-Dyson equation (SDE) and Bethe-Salpeter equation (BSE).
↳ hep-phnucl-thInt.J.Theor.Phys.(2026)·2 citations
08
Heavy ion collisions from $s_{N N}$ of 62.4 GeV down to 4 GeV in the EPOS4 framework
K. Werner🇫🇷 · J. Jahan🇺🇸 · I. Karpenko🇨🇿 · T. Pierog🇩🇪 · M. Stefaniak🇺🇸 · D. Vintache🇫🇷
The EPOS4 project is an attempt to construct a realistic model for describing relativistic collisions of different systems, from proton-proton ( $pp$ ) to nucleus-nucleus ( $AA$ ), at energies from several TeV per nucleon down to several GeV. We argue that a parallel scattering formalism (as in EPOS4) is relevant for primary scatterings in AA collisions above 4 GeV, whereas sequential scattering (cascade) is appropriate below. We present briefly the basic elements of EPOS4, and then investigate heavy ion collisions from 62.4 GeV down to 4 GeV, to understand how physics changes with energy, studying in particular the disappearance of the fluid component at low energies.
↳ hep-phnucl-thPRC(2025)·16 citations
09
The $X (3872)$ to $ψ (2 S)$ yield ratio in heavy-ion collisions
L. M. Abreu🇧🇷 · F. S. Navarra🇧🇷 · H. P. L. Vieira🇧🇷
In this work we evaluate the $X (3872)$ to $ψ (2 S)$ yield ratio ( $N_{X} / N_{ψ (2 S)}$ ) in Pb Pb collisions, taking into account the interactions of the $ψ (2 S)$ and $X (3872)$ states with light mesons in the hadron gas formed at the late stages of these collisions. We employ an effective Lagrangian approach to estimate the thermally-averaged cross sections for the production and absorption of the $ψ (2 S)$ and use them in the rate equation to determine the time evolution of $N_{ψ (2 S)}$ . The multiplicity of these states at the end of mixed phase is obtained from the coalescence model. The multiplicity of $X (3872)$ , treated as a bound state of $(D D ˉ^{*} + c . c .)$ and also as a compact tetraquark, was already calculated in previous works. Knowing these yields, we derive predictions for the ratio ( $N_{X} / N_{ψ (2 S)}$ ) as a function of the centrality, of the center-of-mass energy and of the charged hadron multiplicity measured at midrapidity $[d N_{c h} / d η (η < 0.5)]$ . Finally, we make predictions for this ratio in Pb Pb collisions at $s_{N N} = 5.02$ TeV to be measured by the ALICE Collaboration in the Run 3.
↳ hep-phnucl-thPRD(2024)·9 citations
10
Correlating $B \to K^{(*)} ν ν ˉ$ and flavor anomalies in SMEFT
Feng-Zhi Chen🇨🇳 · Qiaoyi Wen🇨🇳 · Fanrong Xu🇨🇳
The recent measurement of $B (B^{+} \to K^{+} ν ν ˉ)$ by Belle-II reveals a $2.8 σ$ deviation from the Standard Model (SM) prediction. Combining this with a prior Belle measurement of $B (B^{0} \to K^{* 0} ν ν ˉ)$ , the upper bound of the ratio $B (B^{0} \to K^{* 0} ν ν ˉ) / B (B^{+} \to K^{+} ν ν ˉ)$ is notably smaller than the SM prediction. In this work, tensions are solved within the framework of Standard Model Effective Field Theory (SMEFT). Flavor observables, described by Low-Energy Effective Field Theory (LEFT) operators, are interconnected by SMEFT at the electroweak scale. Utilizing a set of only four SMEFT operators, the FCNC process $b \to s ν ν ˉ$ is correlated with $b \to s ℓ^{+} ℓ^{-}$ , $b \to u_{i} ℓ ν ˉ$ , $u_{j} \to s ℓ ν ˉ$ , $u_{j} \to u_{i} ν ν ˉ$ , and $u_{j} \to u_{i} ℓ^{+} ℓ^{-}$ . Subsequently, we obtain the latest ranges of Wilson coefficients for these four operators through a global fit that accommodates flavor anomalies such as $R_{K^{(*)}}$ , $R_{D^{(*)}}$ , and $B (B \to K^{(*)} ν ν ˉ)$ . Our findings reveal that predictions for $B (B^{+} \to τ^{+} ν_{τ})$ and $B (D_{s}^{+} \to τ^{+} ν_{τ})$ align well with measured values from Belle and BESIII, based on the fitted coefficients. The predicted branching fraction for $B^{0} \to K^{* 0} ν ν ˉ$ is $(1.42 \pm 0.74) \times 1 0^{- 5}$ , closely approaching the current experimental upper limit. Anticipation surrounds the rare decay $B_{s} \to τ^{+} τ^{-}$ , expected in the near future with a branching fraction on the order of $1 0^{- 4}$ .
↳ hep-phnucl-thEPJC(2024)·47 citations
11
Chiral perturbation theory with vector mesons and the pion form factors
Tae-Sun Park🇰🇷
The chiral perturbation theory (ChPT) of pions is extended to include vector mesons as well as pertinent degrees of freedom. By counting the typical momentum scale of vector mesons as order of $Q$ and vector meson masses as of the order of $Λ_{χ}$ , a consistent theory could be obtained. The explicit renormalization procedure of the theory is presented for the form factors of the pion up to one-loop accuracy. The resulting theory prediction for the form factors is in good agreement with the experimental data for a wide range of momentum transfers. The vector-meson dominance mechanism is also discussed in the systematic framework of ChPT.
↳ hep-phnucl-th2 citations
12
Parametric Matrix Models
Patrick Cook · Danny Jammooa · Morten Hjorth-Jensen · Daniel D. Lee · Dean Lee
We present a general class of machine learning algorithms called parametric matrix models. In contrast with most existing machine learning models that imitate the biology of neurons, parametric matrix models use matrix equations that emulate physical systems. Similar to how physics problems are usually solved, parametric matrix models learn the governing equations that lead to the desired outputs. Parametric matrix models can be efficiently trained from empirical data, and the equations may use algebraic, differential, or integral relations. While originally designed for scientific computing, we prove that parametric matrix models are universal function approximators that can be applied to general machine learning problems. After introducing the underlying theory, we apply parametric matrix models to a series of different challenges that show their performance for a wide range of problems. For all the challenges tested here, parametric matrix models produce accurate results within an efficient and interpretable computational framework that allows for input feature extrapolation.
↳ cs.LGcond-mat.dis-nnnucl-thphysics.comp-ph+1Nature Commun.(2025)·29 citations
13
Unraveling Generalized Parton Distributions Through Lorentz Symmetry and Partial DGLAP Knowledge
P. Dall'Olio🇪🇸 · F. De Soto🇪🇸 · C. Mezrag🇫🇷 · J.M. Morgado Chávez🇫🇷 · H. Moutarde🇫🇷 · J. Rodríguez-Quintero🇪🇸 · P. Sznajder🇵🇱 · J. Segovia🇪🇸
Relying on the polynomiality property of generalized parton distributions, which roots on Lorentz covariance, we prove that it is enough to know them at vanishing- and low-skewness within the DGLAP region to obtain a unique extension to their entire support up to a D-term. We put this idea in practice using two methods: Reconstruction using artificial neural networks and finite-elements methods. We benchmark our results against standard models for generalized parton distributions. In agreement with the formal expectation, we obtain a very accurate reconstructions for a maximal value of the skewness as low as 20% of the longitudinal momentum fraction. This result might be relevant for reconstruction of generalized parton distribution from experimental and lattice QCD data, where computations are for now, restricted in skewness.
↳ hep-phnucl-thPRD(2024)·12 citations
14
Toward QCD on Quantum Computer: Orbifold Lattice Approach
Georg Bergner🇩🇪 · Masanori Hanada🇬🇧 · Enrico Rinaldi🇯🇵 · Andreas Schafer🇩🇪
We propose an orbifold lattice formulation of QCD suitable for quantum simulations. We show explicitly how to encode gauge degrees of freedom into qubits using noncompact variables, and how to write down a simple truncated Hamiltonian in the coordinate basis. We show that SU(3) gauge group variables and quarks in the fundamental representation can be implemented straightforwardly on qubits, for arbitrary truncation of the gauge manifold.
↳ hep-thhep-lathep-phnucl-th+1JHEP(2024)·35 citations
15
Threshold photoproduction of $η_{c}$ and $η_{b}$ using holographic QCD
Florian Hechenberger🇦🇹 · Kiminad A. Mamo🇺🇸 · Ismail Zahed🇺🇸
We discuss the possibility that threshold photoproduction of $η_{c, b}$ may be sensitive to the pseudovector $1^{+-}$ glueball exchange. We use the holographic construction to identify the pseudovector glueball with the Kalb-Ramond field, minimally coupled to bulk Dirac fermions. We derive the holographic C-odd form factor and its respective charge radius. Using the pertinent Witten diagrams, we derive and analyze the differential photoproduction cross section for $η_{c, b}$ in the threshold regime, including the interference from the dual bulk photon exchange with manifest vector dominance. The possibility of measuring this process at current and future electron facilities is discussed.
↳ hep-phnucl-thPRD(2024)·8 citations

Affiliations

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