Nuclear Theory·nucl-th

Tuesday·May 21, 2019

11 papers—5 primary·6 cross-listed

01
On the convergence of nuclear effective field theory with perturbative pions
David B. Kaplan🇺🇸
The classic paper by Fleming, Mehen and Stewart cast doubts on the convergence of spin-triplet nucleon-nucleon partial wave scattering amplitudes when following the proposal of Kaplan, Savage and Wise to construct nuclear effective field theory around the unitary fermion limit with perturbative pion exchange. FMS identified the subclass of iterated one-pion exchange potential graphs as the cause of this poor convergence, which they showed persisted in the chiral limit. Theoretical tools are developed here to compute these Feynman graphs analytically to high order in all angular momentum channels simultaneously, examining the amplitudes computed to seven loops in the $L = J$ channels, and three loops in the coupled $L = J \pm 1$ channels. One finds that there is nothing pathological about the perturbative expansion of a $1/ r^{3}$ potential in general, and that the expansion converges satisfactorily in all partial waves except those with the lowest angular momentum, particularly the $^{3} P_{0}$ and the coupled $^{3} S_{1} -^{3} D_{1}$ channels. The results corroborate work by Birse, which suggests possible avenues to explore for improving the range of validity of the EFT expansion.
nucl-thhep-phPRC(2020)·41 citations
02
Effects of the Coulomb interaction on parameters of resonance states in mirror three-cluster nuclei
A.D. Duisenbay · N. Kalzhigitov · K. Katō · V. O. Kurmangaliyeva · N. Takibayev · V. S. Vasilevsky
We investigate how the Coulomb interaction affects the energy $E$ and width $Γ$ of resonance states in mirror nuclei. We employ a three-cluster microscopic model to determine position of resonance states in two- and three-body continua. Two parameters are introduced to quantify effects of the Coulomb interactions. As the energy and width of the corresponding resonance states of mirror nuclei are displayed on an $E$ - $Γ$ plane, these parameters determine a rotation and a dilatation. With the help of these parameters we found resonance states with strong, small and medium effects of the Coulomb interaction. We also found two different scenarios of the motion of resonance states due to the Coulomb interaction. The first standard (major) scenario represent resonance states with the larger energy and larger width than their counterparts have. The second rear scenario includes resonance states with the larger energy but smaller width.
nucl-thNPA(2020)·7 citations
03
Effects of pairing, continuum, and deformation on particles in the classically forbidden regions for Mg isotopes
Kaiyuan Zhang · Dongyang Wang · Shuangquan Zhang
Particles in the classically forbidden regions are studied based on the deformed relativistic Hartree-Bogoliubov theory in continuum with PC-PK1 for magnesium isotopes. By analyzing the neutron and proton radii, it is found that the largest deviations from the empirical values appear at the predicted neutron halo nuclei $^{42}$ Mg and $^{44}$ Mg. Consistently, notable increases at $^{42}$ Mg and $^{44}$ Mg are found in the total number of neutrons in the classically forbidden regions that includes the number of neutrons in continuum. It is shown that the deformation effect, in general, increases the number of particles in the classically forbidden regions below the continuum threshold. The most deeply bound single-particle states play the dominant roles in the increase caused by deformation.
nucl-thPRC(2019)·62 citations
04
$^{42}$ Ca and $^{50}$ Ca with the (Many- and Few-body) Unified Method
E. Garrido · A.S. Jensen
A new method unifying many and few-body aspects of nuclear structure has recently been introduced \cite{hov18}. This method combines the many-body description of a core and the few-body structure of this core surrounded by two valence nucleons. For this reason this method is expected to work specially well when applied to nuclei close to the driplines, where the few-body halo structure with one or more nucleons outside the core is established. In this work we apply the new method to nuclei close to the valley of stability, with $^{42}$ Ca and $^{50}$ Ca as illustrations. We compare the results from uncorrelated mean-field calculations with the ones obtained with the unified method allowing arbitrary correlations in the valence space. We find that the unified method provides results rather similar, although distinguishable, to the Hartree-Fock calculations. The correlations are much less pronounced than at the driplines, which initially were targets for the unified method. The halo structure is not artificially maintained, but the correlations are here demonstrated to be applicable to well-bound nuclei. Excited states built on valence degrees of freedom are calculated for the same nuclei.
nucl-thFew Body Syst.(2019)·1 citation
05
Microscopic three-cluster study of light exotic nuclei
P. Descouvemont
I develop a microscopic three-cluster model for exotic light nuclei. I use the hyperspherical formalism, associated with the Generator Coordinate Method. This model is well adapted to halo nuclei, since the long-range part of the radial wave functions is accurately reproduced. The core wave functions are described in the shell model, including excited states. This technique provides large bases, expressed in terms of projected Slater determinants. Matrix elements involve seven-dimension integrals, and therefore require long calculation times. I apply the model to 11Li, 14Be, 15B, and 17N described by two neutrons surrounding a 9Li, 12Be, 13B and 15N core, respectively. The 17Ne (as 15O+p+p) and 15Ne (as 13O+p+p) mirror nuclei are briefly discussed. I present the spectra and some spectroscopic properties, such as r.m.s. radii or E2 transition probabilities. I also analyze the importance of core excitations.
nucl-thPRC(2019)·9 citations
06
Subleading Power Factorization with Radiative Functions
Ian Moult🇺🇸 · Iain W. Stewart🇺🇸 · Gherardo Vita🇺🇸
The study of amplitudes and cross sections in the soft and collinear limits allows for an understanding of their all orders behavior, and the identification of universal structures. At leading power soft emissions are eikonal, and described by Wilson lines. Beyond leading power the eikonal approximation breaks down, soft fermions must be added, and soft radiation resolves the nature of the energetic partons from which they were emitted. For both subleading power soft gluon and quark emissions, we use the soft collinear effective theory (SCET) to derive an all orders gauge invariant bare factorization, at both amplitude and cross section level. This yields universal multilocal matrix elements, which we refer to as radiative functions. These appear from subleading power Lagrangians inserted along the lightcone which dress the leading power Wilson lines. The use of SCET enables us to determine the complete set of radiative functions that appear to $O (λ^{2})$ in the power expansion, to all orders in $α_{s}$ . For the particular case of event shape observables in $e^{+} e^{-} \to$ dijets we derive how the radiative functions contribute to the factorized cross section to $O (λ^{2})$ .
↳ hep-phnucl-thJHEP(2019)·91 citations
07
Event shape and Multiplicity dependence of Freeze-out Scenario and System Thermodynamics in Proton+Proton Collisions at $s$ = 13 TeV using PYTHIA8
Sushanta Tripathy🇮🇳 · Ashish Bisht🇮🇳 · Raghunath Sahoo🇮🇳 · Arvind Khuntia🇵🇱 · Malavika Panikkassery Salvan🇮🇳
Recent observations of QGP-like conditions in high-multiplicity pp collisions from ALICE experiment at the LHC warrants an introspection whether to use pp collisions as a baseline measurement to characterize heavy-ion collisions for possible formation of a Quark-Gluon Plasma. A double differential study of the particle spectra and thermodynamics of the produced system as a function of charged-particle multiplicity and transverse spherocity in pp collisions would shed light into the underlying event dynamics. Transverse spherocity, one of the event shape observables, allows to separate the events in terms of jetty and isotropic events. We analyse the identified particle transverse momentum ( $p_{T}$ ) spectra as a function of charged-particle multiplicity and transverse spherocity using Tsallis non-extensive statistics and Boltzmann-Gibbs Blastwave (BGBW) model in pp collisions at $s$ = 13 TeV using PYTHIA8 event generator. The extracted parameters such as temperature ( $T$ ), radial flow ( $β$ ) and non-extensive parameter ( $q$ ) are shown as a function of charged-particle multiplicity for different spherocity classes. We observe that the isotropic events approach to thermal equilibrium while the jetty ones remain far from equilibrium. We argue that, while studying the QGP-like conditions in small systems, one should separate the isotropic events from the spherocity-integrated events, as the production dynamics are different.
↳ hep-phhep-exnucl-exnucl-thAdv.High Energy Phys.(2021)·28 citations
08
Thermal Diffusion and Quantum Chaos in Neutral Magnetized Plasma
Wei Li🇹🇼 · Shu Lin🇨🇳 · Jiajie Mei🇨🇳
We calculate the thermal diffusion constant $D_{T}$ and butterfly velocity $v_{B}$ in neutral magnetized plasma using holographic magnetic brane background. We find the thermal diffusion constant satisfies Blake's bound. The constant in the bound $D_{T} 2 π T / v_{B}^{2}$ is a decreasing function of magnetic field. It approaches one half in the large magnetic field limit. We also find the existence of a special point defined by Lyapunov exponent and butterfly velocity on which pole-skipping phenomenon occurs.
↳ hep-thcond-mat.str-elnucl-thPRD(2019)·32 citations
09
Mass shifts of $^{3} P_{J}$ heavy quarkonia due to the effect of two-gluon annihilation
Hui-Yun Cao🇨🇳 · Hai-Qing Zhou🇨🇳
In this work, we calculate the nonrelativistic asymptotic behavior of the amplitudes of $q q \to 2 g \to q q$ in the leading order of $α_{s}$ (LO- $α_{s}$ ) with $q q$ in the $^{3} P_{J}$ channels. In the practical calculation we take the momenta of quarks and antiquarks on-shell and expand the amplitudes on the three-momentum of the quarks and antiquarks to order 6 and get three nonzero terms. The imaginary parts of the first term and the second term are the old. The real parts of the results have IR divergence. When applying the results to the heavy quarkonia, the corresponding amplitude of $q q \to 1 g \to q q$ with $q q$ in the color octet $^{3} S_{1}$ channel is considered to absorb the IR divergence in a unitary way in the leading order of $v$ (LO- $v$ ). The finial results can be used to estimate the mass shifts of the $^{3} P_{J}$ heavy quarkonia due to the effect of two-gluon annihilation. The numerical estimation shows that the contributions to the mass shifts of $χ_{c 0, c 1, c 2}$ are about $1.23 \sim 1.58$ MeV, $1.57 \sim 1.86$ MeV and $5.92 \sim 5.45$ MeV when taking $α_{s} \approx 0.25 \sim 0.35$ .
↳ hep-phnucl-thPRD(2019)·1 citation
10
Deep Inelastic Scattering on an Extremal RN-AdS Black Hole II: Holographic Fermi Surface
Kiminad A. Mamo🇺🇸 · Ismail Zahed🇺🇸
We consider deep inelastic scattering (DIS) on a dense nucleus described as an extremal RN-AdS black hole with holographic quantum fermions in the bulk. We evaluate the 1-loop fermion contribution to the R-current on the charged black hole, and map it on scattering off a Fermi surface of a dense and large nucleus with fixed atomic number. Near the black hole horizon, the geometry is that of AdS $_{2} \times$ R $^{3}$ where the fermions develop an emergent Fermi surface with anomalous dimensions. DIS scattering off these fermions yields to anomalous partonic distributions mostly at large-x, as well as modified hard scattering rules. The pertinent R-ratio for the black hole is discussed. For comparison, the structure functions and the R-ratio in the probe or dilute limit with no back-reaction on the geometry, are also derived. We formulate a hybrid holographic model for DIS scattering on heavy and light nuclei, which compares favorably to the existing data for Pb, Au, Fe, C and He over a wide range of parton-x.
↳ hep-thhep-phnucl-thPRD(2020)·6 citations
11
System size and Multiplicity dependence of Chemical freeze-out parameters at the Large Hadron Collider Energies
Rutuparna Rath🇮🇳 · Arvind Khuntia🇵🇱 · Raghunath Sahoo🇮🇳
The collision system and multiplicity dependence of chemical freeze-out temperature ( $T_{ch}$ ) and strangeness saturation factor ( $γ_{s}$ ) are obtained by studying the particle ratios at the Large Hadron Collider (LHC) energies. Here, we consider the new results in pp at 13 TeV, p+Pb at $s_{NN}$ = 5.02 TeV, Xe+Xe at $s_{NN}$ = 5.44 TeV and Pb+Pb at $s_{NN}$ = 5.02 TeV along with the earlier results in pp at $s$ = 7 TeV and Pb+Pb at $s_{NN}$ = 2.76 TeV. A statistical thermal model is used to extract the chemical freeze-out parameters in different multiplicity classes. To understand the particle production from small to large collision systems two ensembles namely, canonical and grand canonical have been considered in this study. A clear observation of multiplicity dependence of $T_{ch}$ and $γ_{s}$ is observed. The values obtained in high-multiplicity pp collisions are found to be similar to the peripheral Pb+Pb collisions. A final state midrapidity charged particle multiplicity density of around 20-30 appears to be a threshold below which, the chemical freeze-out temperature is lower than the kinetic freeze-out temperature.
↳ hep-phhep-exnucl-exnucl-th5 citations

Affiliations

first authorsco-authorsvia INSPIRE