Nuclear Theory·nucl-th

Friday·December 2, 2022

12 papers—6 primary·6 cross-listed

01
Ab initio investigations of A=8 nuclei: $α - α$ scattering, deformation in $^{8}$ He, radiative capture of protons on $^{7}$ Be and $^{7}$ Li and the X17 boson
P. Navratil🇨🇦 · K. Kravvaris🇺🇸 · P. Gysbers🇨🇦 · C. Hebborn🇺🇸 · G. Hupin🇫🇷 · S. Quaglioni🇺🇸
We apply the No-Core Shell Model with Continuum (NCSMC) that is capable of describing both bound and unbound states in light nuclei in a unified way with chiral two- and three-nucleon interactions as the only input. The NCSMC can predict structure and dynamics of light nuclei and, by comparing to available experimental data, test the quality of chiral nuclear forces. We discuss applications of NCSMC to the $α - α$ scattering and the structure of $^{8}$ Be, the p+ $^{7}$ Be and p+ $^{7}$ Li radiative capture and the production of the hypothetical X17 boson claimed in ATOMKI experiments. The $^{7}$ Be(p, $γ$ ) $^{8}$ B reaction plays a role in Solar nucleosynthesis and Solar neutrino physics and has been subject of numerous experimental investigations. We also highlight our investigation of the neutron rich exotic $^{8}$ He that has been recently studied experimentally at TRIUMF with an unexpected deformation reported.
nucl-thnucl-exJ.Phys.Conf.Ser.(2023)·1 citation
02
ASTROPHYSICAL S(0)-FACTORS FOR THE $^{3} He (α, γ)^{7} Be$ , $^{3} H (α, γ)^{7} Li$ and $^{7} Be (p, γ)^{8} B$ DIRECT CAPTURE PROCESSES IN A POTENTIAL MODEL
S. A.Turakulov · E. M.Tursunov
Astrophysical S-factors at zero energy for the direct nuclear capture reactions $^{3} He (α, γ)^{7} Be$ , $^{3} H (α, γ)^{7} Li$ and $^{7} Be (p, γ)^{8} B$ are estimated within the framework of two-body potential cluster model on the basis of extranuclear capture approximation of D. Baye and E. Brainis. The values of S(0)-factors have been calculated using two different potential models for each process, which were adjusted to the binding energies and empirical values of the asymptotical normalization coefficients from the literature. New values of S(0)-factors have been obtained.
nucl-thastro-ph.SR0 citations
03
Kaon condensation in skyrmion matter and compact stars
Christoph Adam🇪🇸 · Alberto García Martín-Caro🇪🇸 · Miguel Huidobro🇪🇸 · Ricardo Vázquez🇪🇸 · Andrzej Wereszczynski🇵🇱
We address the possibility of the appearance of a charged kaon condensate in neutron star cores described within a generalized Skyrme model. Our treatment of strange degrees of freedom is based on the Bound State Approach by Callan and Klebanov, which allows to obtain an in-medium effective potential for the $s$ -wave kaon condensate. We predict the onset of kaon condensation at a certain threshold density - whose value depends on the parameters of the model, and ranges between 1.5 and 2.5 times saturation density -, and obtain both the particle fractions and equation of state for dense matter in the kaon condensed phase. Finally, we discuss the effect of such condensates on the mass-radius curves and other observable properties of neutron stars with kaon condensed cores.
nucl-thhep-phPRD(2023)·15 citations
04
Fusion systematics for weakly bound nuclei using neutron flow and collective degrees of freedom
S. Appannababu · V. V. Parkar · V. Jha · S. Kailas
A systematic analysis of the fusion cross sections around the Coulomb barrier energies with stable weakly bound ( $^{6}$ Li, $^{7}$ Li, $^{9}$ Be) and strongly bound $^{12}$ C projectiles on various targets was performed by using neutron flow model and coupled channels approach. The analysis show that both the models are successful in explaining the near barrier fusion data. Further, it is also observed that the collective degrees of freedom as well as the neutron flow influence the near barrier fusion process involving weakly bound projectiles.
nucl-thnucl-exPRC(2022)·3 citations
05
A new three-ranged Gogny interaction in touch with pion exchange
L. Batail🇧🇪 · D. Davesne🇫🇷 · S. Péru🇫🇷 · P. Becker🇫🇷 · A. Pastore🇬🇧 · J. Navarro🇪🇸
We present a new Gogny-type finite-range effective interaction including a third Gaussian in the central term. Based on simple arguments valid for an arbitrary radial form factor, the three ranges are fixed from physical grounds, relating them to one-boson exchange interactions. Moreover, some parameters of the longest range are fixed through the G-matrix elements of the One Pion Exchange Potential. On top of giving a fairly good description of atomic nuclei properties, the resulting interaction leads to a remarkable improvement of some infinite matter properties that are relevant for astrophysical calculations.
nucl-thEPJA(2023)·13 citations
06
Microscopic Optical Potentials: recent achievements and future perspectives
P. Finelli · M. Vorabbi · C. Giusti
Few years ago we started the investigation of microscopic Optical Potentials (OP) in the framework of chiral effective field theories and published our results in a series of manuscripts. Starting from the very first work, where a microscopic OP was introduced following the multiple scattering procedure of Watson, and then followed by more recent works, where the agreement with experimental data and phenomenological approaches was successfully tested, we finally arrived at a description of elastic scattering processes off non-zero spin nuclei. Among our achievements, it is worth mentioning the partial inclusion of three-nucleon forces, and the extension of our OP to antiproton-nucleus elastic scattering. Despite the overall good agreement with empirical data obtained so far, we do believe that several improvements and upgrades of the present approach are still to be achieved. In this short essay we would like to address some of the most relevant achievements and discuss an interesting development that, in our opinion, is needed to further improve microscopic OPs in order to reach in a near future the same level of accuracy of the phenomenological ones.
nucl-thJ.Phys.Conf.Ser.(2023)·4 citations
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