Nuclear Theory·nucl-th

Friday·December 2, 2022

12 papers—6 primary·6 cross-listed

07
Lattice study on a tetraquark state $T_{bb}$ in the HAL QCD method
Sinya Aoki🇯🇵 · Takafumi Aoki🇯🇵
We investigate a doubly-bottomed tetraquark state $T_{bb}$ $(bb u ˉ d ˉ)$ with quantum number $I (J^{P}) = 0 (1^{+})$ in $(2 + 1)$ -flavor lattice QCD. Using the Non-Relativistic QCD (NRQCD) quark action for $b$ quarks, we have extracted the coupled channel potential between $B ˉ B ˉ^{*}$ and $B ˉ^{*} B ˉ^{*}$ in the HAL QCD method at $a \approx 0.09$ {fm} on $3 2^{3} \times 64$ lattices. The potential predicts an existence of a bound $T_{bb}$ below the $B ˉ B ˉ^{*}$ threshold. At the physical pion mass $m_{π} \approx 140$ {MeV} extrapolated from $m_{π} \approx 410, 570, 700$ {MeV}, a binding energy with its statistical error is given by $E_{binding}^{(coupled)} = 83 (10)$ MeV from a coupled channel analysis where effects due to virtual $B ˉ^{*} B ˉ^{*}$ states are included through the coupled channel potential, while we obtain $E_{binding}^{(single)} = 155 (17)$ MeV only from a potential for a single $B ˉ B ˉ^{*}$ channel. This difference indicates that the effect from virtual $B ˉ^{*} B ˉ^{*}$ states is sizable to the binding energy of $T_{bb}$ . Adding $\pm 20$ MeV as empirical systematic error caused by the NRQCD approximation for $b$ quarks, our estimate of the $T_{bb}$ binding energy becomes $83 (10) (20)$ MeV.
↳ hep-latnucl-thPoS(2023)·7 citations
08
Secondary Neutron Production from Thick Target Deuteron Breakup
Jonathan T. Morrell · Andrew S. Voyles · Jon C. Batchelder · Joshua A. Brown · Lee A. Bernstein
Thick target deuteron breakup is a variable-energy accelerator-based source of high-energy neutrons, with applications in fundamental and applied nuclear science and engineering. However, the breakup mechanism remains poorly understood, and data on neutron yields from thick target breakup remains relatively scarce. In this work, the double-differential neutron yields from deuteron breakup have been measured on a thick beryllium target at $ϵ_{d} = 33$ and 40 MeV, using both time-of-flight and activation techniques. We have also introduced a simple hybrid model for the double-differential deuteron breakup cross section, applicable in the $ϵ_{d} = 10$ -- $100$ MeV energy range on light ( $Z \leq 6$ ) targets. This model features four empirical parameters that have been fit to reproduce experimental breakup measurements on beryllium targets, using the method of least-squares. It was shown that these parameters extrapolate well to higher energies, and to other low-Z target materials. We also include optimization of the parameters that modify the Kalbach systematics for compound and pre-equilibrium reactions, in order to better reproduce the experimental data for beryllium targets at large angles.
↳ nucl-exnucl-thphysics.med-phPRC(2023)·3 citations
09
Transport coefficients of heavy mesons in a thermal medium
Juan M. Torres-Rincon🇪🇸
We have investigated the many-body equations of $D$ and $B ˉ$ mesons in a thermal medium by applying an effective field theory based on chiral and heavy-quark symmetries. Exploiting these symmetries within kinetic theory, we have derived an off-shell Fokker-Planck equation which incorporates information of the full spectral functions of these states. In this contribution we present our latest results on heavy-flavor transport coefficients below the chiral restoration temperature, in both charm and bottom sectors. The calculation incorporating temperature-dependent spectral functions and interactions, together with off-shell effects, allows for an improved matching to the state-of-the-art calculations above the chiral transition temperature.
↳ hep-phnucl-thPoS·0 citations
10
Accessing chiral-even quark generalised parton distributions in the exclusive photoproduction of a $γ π^{\pm}$ pair with large invariant mass in both fixed-target and collider experiments
Goran Duplančić🇭🇷 · Saad Nabeebaccus🇫🇷 · Kornelija Passek-Kumerički🇭🇷 · Bernard Pire🇫🇷 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷
We compute the exclusive photoproduction of a $γ π^{\pm}$ pair using the collinear factorisation framework, in the kinematic regime where the pair has a large invariant mass. This exclusive channel presents a new avenue for the investigation of GPDs. It is particularly interesting as the high centre of mass energies available at future experiments will allow the study of GPDs at small skewness $ξ$ . We compute the scattering amplitude of the process, at leading twist and leading order in $α_{s}$ , which is used to estimate its cross-section and linear polarisation asymmetries with respect to the incoming photon, for JLab~12-GeV, COMPASS, future EIC and LHC (in ultra-peripheral collisions) kinematics. We find that the order of magnitude of estimates are sufficiently large for a dedicated experimental analysis to be performed, especially at JLab. We also compare the results from an asymptotic distribution amplitude (DA) to those using a recently proposed \textit{holographic} DA.
↳ hep-phhep-exnucl-exnucl-thJHEP(2023)·46 citations
11
Basics of factorization in a scalar Yukawa field theory
F. Aslan🇺🇸 · L. Gamberg🇺🇸 · J. O. Gonzalez-Hernandez🇮🇹 · T. Rainaldi🇺🇸 · T. C. Rogers🇺🇸
The factorization theorems of quantum chromodynamics (QCD) apply equally well to most simple quantum field theories that require renormalization but where direct calculations are much more straightforward. Working with these simpler theories is convenient for stress-testing the limits of the factorization program and for examining general properties of the parton density functions (pdfs) or other correlation functions that might be necessary for a factorized description of a process. With this view in mind, we review the steps of factorization in a real scalar Yukawa field theory for both deep inelastic scattering (DIS) and semi-inclusive deep inelastic scattering (SIDIS) cross sections. In the case of SIDIS, we illustrate how to separate the small transverse momentum region, where transverse momentum dependent (TMD) pdfs are needed, from a purely collinear large transverse momentum region, and we examine the influence of subleading power corrections. We also review the steps for formulating TMD factorization in transverse coordinate space, and we study the effect of transforming to the well-known $b_{*}$ -scheme. Within the Yukawa theory, we investigate the consequences of switching to a generalized parton model (GPM) approach, and compare with a fully factorized approach. Our results highlight the need to address similar or analogous issues in QCD.
↳ hep-phhep-exhep-thnucl-thPRD(2023)·12 citations
12
A Strong-QCD Regime Measurement of the Proton's Spin Structure
David Ruth🇺🇸
The theory of the strong force, Quantum Chromodynamics (QCD) remains one of the most important ways to understand the fundamental properties of ordinary matter. However, at low momentum transfer Q2, in the regime where the strong force becomes extremely strong, our understanding of QCD for ordinary nucleons becomes hazy. Several cutting edge theories such as Chiral Perturbation Theory and Lattice QCD have provided valuable predictions in this regime, but Lattice QCD has not yet extended predictions of many important quantities to this kinematic region, and Chiral Perturbation Theory has faced several important disagreements with experimental data for the neutron over the last several decades. It is therefore of extreme importance to have a benchmark of experimental data in the low energy regime for the proton's behavior, as a test of leading theories for the behavior of QCD in this regime. The E08-027 (g2p) experiment ran at Jefferson Lab in 2012 with the goal of collecting this valuable data. Full details of the g2p experiment and my experimental work at the University of New Hampshire are presented in this thesis, as well as a detailed description of the analysis process and the exciting benchmark results, which serve as a direct test of all current and future theories of QCD in the low-Q2 regime.
↳ nucl-exnucl-thphysics.acc-phphysics.atom-ph0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Lattice study on a tetraquark state Tbb​ in the HAL QCD method

Secondary Neutron Production from Thick Target Deuteron Breakup

Transport coefficients of heavy mesons in a thermal medium

Accessing chiral-even quark generalised parton distributions in the exclusive photoproduction of a γπ± pair with large invariant mass in both fixed-target and collider experiments

Basics of factorization in a scalar Yukawa field theory

A Strong-QCD Regime Measurement of the Proton's Spin Structure

Affiliations

Lattice study on a tetraquark state $T_{bb}$ in the HAL QCD method

Accessing chiral-even quark generalised parton distributions in the exclusive photoproduction of a $γ π^{\pm}$ pair with large invariant mass in both fixed-target and collider experiments