Nuclear Theory·nucl-th

Tuesday·November 28, 2017

20 papers—11 primary·9 cross-listed

01
Parton distribution amplitudes: revealing diquarks in the proton and Roper resonance
Cedric Mezrag🇮🇹 · Jorge Segovia🇪🇸 · Lei Chang🇨🇳 · Craig D. Roberts🇺🇸
We present the first quantum field theory calculation of the pointwise behaviour of the leading-twist parton distribution amplitudes (PDAs) of the proton and its lightest radial excitation. The proton's PDA is a broad, concave function, whose maximum is shifted relative to the peak in QCD's conformal limit expression for this PDA; an effect which signals the presence of both scalar and pseudovector diquark correlations in the nucleon, with the scalar generating around 60% of the proton's normalisation. The radial-excitation is constituted similarly, and the pointwise form of its PDA, which is negative on a material domain, is the result of marked interference between the contributions from both types of diquark; particularly, the locus of zeros that highlights its character as a radial excitation. These features originate with the emergent phenomenon of dynamical chiral-symmetry breaking in the Standard Model.
nucl-thhep-lathep-phnucl-exPLB(2018)·45 citations
02
Parameter free predictions within the proxy-SU(3) model
A. Martinou · D. Bonatsos · I.E. Assimakis · N. Minkov · S. Sarantopoulou · R.B. Cakirli · R.F. Casten · K. Blaum
Using a new approximate analytic parameter-free proxy-SU(3) scheme, we make predictions of shape observables for deformed nuclei, namely beta and gamma deformation variables, and compare them with empirical data and with predictions by relativistic and non-relativistic mean-field theories. Furthermore, analytic expressions are derived for B(E2) ratios within the proxy-SU(3) model, free of any free parameters, and/or scaling factors. The predicted B(E2) ratios are in good agreement with the experimental data for deformed rare earth nuclides.
nucl-thBulg.J.Phys.(2017)·9 citations
03
Novel Soft-Pion Theorem for Long-Range Nuclear Parity Violation
Xu Feng🇨🇳 · Feng-Kun Guo🇨🇳 · Chien-Yeah Seng🇨🇳
The parity-odd effect in the Standard Model weak neutral current reveals itself in the long-range parity-violating nuclear potential generated by the pion exchanges in the $Δ I = 1$ channel with the parity-odd pion-nucleon coupling constant $h_{π}^{1}$ . Despite decades of experimental and theoretical efforts, the size of this coupling constant is still not well-understood. In this Letter we derive a soft-pion theorem relating $h_{π}^{1}$ and the neutron-proton mass-splitting induced by an artificial parity-even counterpart of the $Δ I = 1$ weak Lagrangian, and demonstrate that the theorem still holds exact at the next-to-leading order in chiral perturbation theory. A considerable amount of simplification is expected in the study of $h_{π}^{1}$ by using either lattice or other QCD models following its reduction from a parity-odd proton-neutron-pion matrix element to a simpler spectroscopic quantity. The theorem paves the way to much more precise calculations of $h_{π}^{1}$ , and thus a quantitative test of the strangeness-conserving neutral current interaction of the Standard Model is foreseen.
nucl-thhep-lathep-phPRL(2018)·12 citations
04
Universal scaling of non-equilibrium critical fluctuations from Langevin dynamics of model A
Shanjin Wu🇨🇳 · Huichao Song🇨🇳
Within the framework of the Kibble-Zurek Mechanism, we investigate the universal behavior of the non-equilibrium critical fluctuations, using the Langevin dynamics of model A. With properly located typical time, length and angle scales, $τ_{\mbox K Z}$ , $l_{\mbox K Z}$ , and $θ_{\mbox K Z}$ , the constructed functions $f ˉ_{n} ((τ - τ_{c}) / τ_{\mbox K Z}, θ_{\mbox K Z})$ (n=1...4) for the cumulants of the sigma field show universal behavior near the critical point, which are independent from some non-universal factors, such as the relaxation time or the evolution trajectory.
nucl-thhep-phPoS(2018)·1 citation
05
Hybridization of tensor-optimized and high-momentum antisymmetrized molecular dynamics for light nuclei with bare interaction
Mengjiao Lyu · Masahiro Isaka · Takayuki Myo · Hiroshi Toki · Kiyomi Ikeda · Hisashi Horiuchi · Tadahiro Suhara · Taiichi Yamada
Many-body correlations play an essential role in the ab initio description of nuclei with nuclear bare interactions. We propose a new framework to describe light nuclei by the hybridization of the tensor-optimized antisymmetrized molecular dynamics (TOAMD) and the high-momentum AMD (HM-AMD), which we call "HM-TOAMD". In this framework, we describe the many-body correlations in terms of not only the correlation functions in TOAMD, but also the high-momentum pairs in the AMD wave function. With the bare nucleon-nucleon interaction AV8', we sufficiently reproduce the energy and radius of the 3H nucleus in HM-TOAMD. The effects of tensor force and short-range repulsion in the bare interaction are nicely described in this new framework. We also discuss the convergence in calculation and flexibility of the model space for this new method.
nucl-thPTEP(2018)·15 citations
06
Signatures of octupole correlations in neutron-rich odd-mass barium isotopes
K. Nomura · T. Nikšić · D. Vretenar
Octupole deformation and the relevant spectroscopic properties of neutron-rich odd-mass barium isotopes are investigated in a theoretical framework based on nuclear density functional theory and the particle-core coupling scheme. The interacting-boson Hamiltonian that describes the octupole-deformed even-even core nucleus, as well as the single-particle energies and occupation probabilities of an unpaired nucleon, are completely determined by microscopic axially-symmetric $(β_{2}, β_{3})$ -deformation constrained self-consistent mean-field calculations for a specific choice of the energy density functional and pairing interaction. A boson-fermion interaction that involves both quadrupole and octupole degrees of freedom is introduced, and their strength parameters are determined to reproduce selected spectroscopic data for the odd-mass nuclei. The model reproduces recent experimental results both for the even-even and odd-mass Ba isotopes. In particular, for $^{145, 147}$ Ba our results indicate, in agreement with recent data, that octupole deformation does not determine the structure of the lowest states in the vicinity of the ground state, and only becomes relevant at higher excitation energies.
nucl-thnucl-exPRC(2018)·36 citations
07
Unearthing radial independence for prediction of alpha-decay half-lives
Swagatika Bhoi · Basudeb Sahu
Nuclear radial distance is a prerequisite for generating any alpha-decay half-life formula by taking a suitable effective potential. We study the emission process of alpha particles from an isolated quasi-bound state generated by an effective potential to a scattering state. The effective potential is expressed in terms of Frahn form of potential which is exactly solvable and an analytical expression for half-life is obtained in terms of Coulomb function, wave function and the potential. We then derive a closed form expression for the decay half-life in terms of the parameters of the potential, Q-value of the system, mass and proton numbers of the nuclei valid for alpha-decay as well as proton-decay. From the nature of variations of half-life as a function of radial distance, we trace the radial independence region where decay time is almost constant. Finally by overviewing our results and picking that particular radial distance we predict the half-lives of a series of nuclei by using the closed form expression.
nucl-thIJMPE(2018)·0 citations
08
A statistical method to estimate low-energy hadronic cross sections
Gábor Balassa🇭🇺 · Péter Kovács🇭🇺 · György Wolf🇭🇺
In this article we propose a model based on the Statistical Bootstrap approach to estimate the cross sections of different hadronic reactions up to a few GeV in c.m.s energy. The method is based on the idea, when two particles collide a so called fireball is formed, which after a short time period decays statistically into a specific final state. To calculate the probabilities we use a phase space description extended with quark combinatorial factors and the possibility of more than one fireball formation. In a few simple cases the probability of a specific final state can be calculated analytically, where we show that the model is able to reproduce the ratios of the considered cross sections. We also show that the model is able to describe proton\,-\,antiproton annihilation at rest. In the latter case we used a numerical method to calculate the more complicated final state probabilities. Additionally, we examined the formation of strange and charmed mesons as well, where we used existing data to fit the relevant model parameters.
nucl-thhep-phEPJA(2018)·10 citations
09
Microscopic description of pair transfer between two superfluid Fermi systems: combining phase-space averaging and combinatorial techniques
David Regnier🇫🇷 · Denis Lacroix🇫🇷 · Guillaume Scamps🇯🇵 · Yukio Hashimoto🇯🇵
In a mean-field description of superfluidity, particle number and gauge angle are treated as quasi-classical conjugated variables. This level of description was recently used to describe nuclear reactions around the Coulomb barrier. Important effects of the relative gauge angle between two identical superfluid nuclei (symmetric collisions) on transfer probabilities and fusion barrier have been uncovered. A theory making contact with experiments should at least average over different initial relative gauge-angles. In the present work, we propose a new approach to obtain the multiple pair transfer probabilities between superfluid systems. This method, called Phase-Space combinatorial (PSC) technique, relies both on phase-space averaging and combinatorial arguments to infer the full pair transfer probability distribution at the cost of multiple mean-field calculations only. After benchmarking this approach in a schematic model, we apply it to the collision $^{20}$ O+ $^{20}$ O at various energies below the Coulomb barrier. The predictions for one pair transfer are similar to results obtained with an approximated projection method whereas significant differences are found for two pairs transfer. Finally, we investigated the applicability of the PSC method to the contact between non-identical superfluid systems. [...] The applicability of the PSC method to asymmetric nuclear collisions is investigated for the $^{14}$ O+ $^{20}$ O collision and it turns out that unrealistically small single- and multiple-pair transfer probabilities are obtained. [...] We conclude that the best ground for probing gauge-angle effects in nuclear reaction and/or for applying the proposed PSC approach on pair transfer is the collisions of identical open-shell spherical nuclei.
nucl-thcond-mat.supr-conPRC(2018)·17 citations
10
Phase transitions for rotational states within an algebraic cluster model
E. Lopez-Moreno · P. O. Hess · H. Yepez-Martinez
The catastrophe theory, an effective method for the description of phase transitions, is applied to the Semimicroscopic Algebraic Cluster Model (SACM) as an example of a non-trivial theory. The ground state and excited, rotational phase transitions are investigated. A short introduction to the SACM and the catastrophe theory is given. We apply the formalism to the test case of 16O+alpha-->20Ne.
nucl-th0 citations
11
van der Waals Interactions and Hadron Resonance Gas: Role of resonance widths modeling on conserved charges fluctuations
Volodymyr Vovchenko🇩🇪 · Paolo Alba🇩🇪 · Mark I. Gorenstein🇺🇦 · Horst Stoecker🇩🇪
The quantum van der Waals (QvdW) extension of the ideal hadron resonance gas (HRG) model which includes the attractive and repulsive interactions between baryons -- the QvdW-HRG model -- is applied to study the behavior of the baryon number related susceptibilities in the crossover temperature region. Inclusion of the QvdW interactions leads to a qualitatively different behavior of susceptibilities, in many cases resembling lattice QCD simulations. It is shown that for some observables, in particular for $χ_{11}^{B Q} / χ_{2}^{B}$ , effects of the QvdW interactions essentially cancel out. It is found that the inclusion of the finite resonance widths leads to an improved description of $χ_{2}^{B}$ , but it also leads to a worse description of $χ_{11}^{B Q} / χ_{2}^{B}$ , as compared to the lattice data. On the other hand, inclusion of the extra, unconfirmed baryons into the hadron list leads to a simultaneous improvement in the description of both observables.
nucl-thhep-phEPJ Web Conf.(2018)·4 citations
12
Hard exclusive pion electroproduction at backward angles with CLAS
K. Park · M. Guidal · R.W. Gothe · B. Pire · K. Semenov-Tian-Shansky · J.-M. Laget
We report on the first measurement of cross sections for exclusive deeply virtual pion electroproduction off the proton, $e p \to e^{'} n π^{+}$ , above the resonance region at backward pion center-of-mass angles. The $φ_{π}^{*}$ -dependent cross sections were measured, from which we extracted three combinations of structure functions of the proton. Our results are compatible with calculations based on nucleon-to-pion transition distribution amplitudes (TDAs) and shed new light on nucleon structure.
↳ nucl-exhep-exhep-phnucl-thPLB(2018)·30 citations
13
Comment on "Relation between scattering amplitude and Bethe-Salpeter wave function in quantum field theory"
Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Tetsuo Hatsuda🇯🇵 · Noriyoshi Ishii🇯🇵
We invalidate the arguments given in [T.Yamazaki and Y.Kuramashi, Phys. Rev. D96, 114511 (2017)] over the HAL QCD method for hadron-hadron interactions on the lattice. We also pose questions on the practical usefulness of the method proposed in this reference.
↳ hep-lathep-phnucl-thPRD(2018)·12 citations
14
Nonextensive statistics based on Landsberg-Vedral entropy
A.S. Parvan
The general formalism for the nonextensive statistics based on the Landsberg-Vedral entropy was derived. The formula for the first law of thermodynamics and the exact relations of the thermodynamic quantities to their ensemble averages were obtained. It was found that under the transformation $q \to 2 - q$ the probabilities of microstates of the nonextensive statistics based on the Landsberg-Vedral entropy formally resemble the corresponding probabilities of the Tsallis statistics with escort probabilities. However, the nonextensive statistics with the Landsberg-Vedral entropy does not require introduction of the escort probabilities and generalized expectation values which are used in this version of the Tsallis statistics.
↳ cond-mat.stat-mechnucl-thEPJ Web Conf.(2019)·1 citation
15
Hyperons in hot dense matter: what do the constraints tell us for equation of state?
M. Fortin🇵🇱 · M. Oertel🇫🇷 · C. Providência🇵🇹
For core-collapse and neutron star merger simulations it is important to have at hand adequate equations of state, describing the underlying dense and hot matter as realistically as possible. Here, we present two newly constructed equation of state (EoS) including the entire baryon octet. Both EoS are compatible with the main constraints from nuclear physics, both experimental and theoretical. One of the EoS is equally describing maximum mass for cold $β$ -equilibrated neutron stars of $2 M_{⊙}$ in agreement with recent observations. The predictions obtained with the new EoS are compared with the results obtained with DD2Y, the only presently existing EoS containing the baryon octet, that satisfies the same constraints within uncertainties. The main difference between our new EoS models and DD2Y is the harder symmetry energy of the latter. We show that the density dependence of the symmetry energy has a direct influence on the amount of strangeness inside hot and dense matter and consequently on thermodynamic quantities, e.g. the temperature for given entropy per baryon. We expect these differences to affect the evolution of a protoneutron star or binary neutron star mergers. We also propose several parametrizations calibrated to $Λ$ hypernuclei based on the DD2 and SFHo models that satisfy the two solar mass constraint.
↳ astro-ph.HEnucl-thPubl.Astron.Soc.Austral.(2018)·62 citations
16
Femtoscopy of stopped protons
Andrzej Bialas🇵🇱 · Adam Bzdak🇵🇱 · Volker Koch🇺🇸
The longitudinal proton-proton femtoscopy (HBT) correlation function, based on the idea that in a heavy ion collision at $s ≲ 20$ GeV stopped protons are likely to be separated in configuration space, is evaluated. It shows a characteristic oscillation which appears sufficiently pronounced to be accessible in experiment. The proposed measurement is essential for estimating the baryon density in the central rapidity region, and can be also viewed as an (almost) direct verification of the Lorentz contraction of the fast-moving nucleus.
↳ hep-phhep-exnucl-exnucl-thPRC(2019)·1 citation
17
Chiral Symmetry and hadron properties at finite temperature -A numerical experiment
Teiji Kunihiro🇯🇵 · Shin Muroya🇯🇵 · Atsushi Nakamura🇷🇺 · Chiho Nonaka🇯🇵 · Motoo Sekiguchi🇯🇵 · Hiroaki Wada🇯🇵 · Masayuki Wakayama🇷🇺
We study the hadron properties at finite temperature from measurement of the screening masses, using two-flavor full QCD of the hybrid Monte Carlo (HMC) algorithm with the renormalization group improved Iwasaki gauge action and the clover improved Wilson quark action on a $1 6^{3} \times 4$ lattice. We explore rather heavy quark mass regions. Disconnected quark diagram is dropped. We observe the tendency that the screening masses in all the channels degenerate, which is in accord with the effective restoration of U $_{A}$ (1) symmetry, and then eventually approach 2 $π T$ , i.e. the free quark value. In the low temperature region below pseudocritical temperature $T_{c}$ , the screening masses in all the channels decrease. We discuss the different features between these calculations and the previous ones.
↳ hep-latnucl-th0 citations
18
Predictions for multiplicities and flow harmonics in 5.44 TeV Xe+Xe collisions at the CERN Large Hadron Collider
K. J. Eskola🇫🇮 · H. Niemi🇩🇪 · R. Paatelainen🇫🇮 · K. Tuominen🇫🇮
We present the next-to-leading-order event-by-event EKRT model predictions for the centrality dependence of the charged hadron multiplicity in the pseudorapidity interval $∣ η ∣ \leq 0.5$ , and for the centrality dependence of the charged hadron flow harmonics $v_{n} {2}$ obtained from 2-particle cumulants, in $s_{N N} = 5.44$ TeV Xe+Xe collisions at the CERN Large Hadron Collider. Our prediction for the 0-5 \% central charged multiplicity is $d N_{ch} / d η = 1218 \pm 46$ . We also predict $v_{n} {2}$ in Xe+Xe collisions to increase more slowly from central towards peripheral collisions than those in a Pb+Pb system. We find that at $10 \dots 50$ \% centralities $v_{2} {2}$ is smaller and $v_{3} {2}$ is larger than in the Pb+Pb system while $v_{4} {2}$ is of the same magnitude in both systems. We also find that the ratio of flow harmonics in Xe+Xe collisions and in Pb+Pb collisions shows a slight sensitivity to the temperature dependence of the shear-viscosity-to-entropy ratio. As we discuss here, the new nuclear mass-number systematics especially in the flow harmonics serves as a welcome further constraint for describing the space-time evolution of a heavy-ion system and for determining the shear viscosity and other transport properties of strongly interacting matter.
↳ hep-phnucl-thPRC(2018)·52 citations
19
(Anti-)Symmetrizing Wave Functions
Chethan Krishnan🇮🇳 · K.V. Pavan Kumar🇮🇳 · P. N. Bala Subramanian🇮🇳
The construction of fully (anti-)symmetric states with many particles, when the single particle state carries multiple quantum numbers, is a problem that seems to have not been systematically addressed in the literature. A quintessential example is the construction of ground state baryon wave functions where the color singlet condition reduces the problem to just two (flavor and spin) quantum numbers. In this paper, we address the general problem by noting that it can be re-interpreted as an eigenvalue equation, and provide a formalism that applies to generic number of particles and generic number of quantum numbers. As an immediate result, we find a complete solution to the two quantum number case, from which the baryon wave function problem with arbitrary number of flavors follows. As a more elaborate illustration that reveals complications not visible in the two quantum number case, we present the complete class of states possible for a system of five fermionic particles with three quantum numbers each. Our formalism makes systematic use of properties of the symmetric group and Young tableaux. Even though our motivations to consider this question have their roots in SYK-like tensor models and holography, the problem and its solution should have broader applications.
↳ hep-thhep-phmath-phmath.MP+1J.Math.Phys.(2019)·4 citations
20
Thermodynamic characterizations of exotic and missing states
Eugenio Megias🇪🇸 · Enrique Ruiz Arriola🇪🇸 · Lorenzo Luis Salcedo🇪🇸
Thermal shifts and fluctuations at finite temperature below the deconfinement crossover of QCD from hadronic matter to the Quark-Gluon Plasma provide a viable way to look for exotic and missing states with given quantum numbers in the hadronic spectrum. We study a realization of the Hadron Resonance Gas model in the light quark ( $u d s$ ) flavor sector of QCD to study: i) the entropy shifts, and ii) the fluctuations of electric charge, baryon number and strangeness; and extract from them the possible existence of missing and exotic states from a comparison with lattice data. The analysis of the entropy shift based on the free energy of the Polyakov loop suggests the existence of exotic hybrids $g q q ˉ$ and $g q q q$ .
↳ hep-phhep-latnucl-thPoS(2018)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE