Nuclear Theory·nucl-th

Thursday·October 17, 2019

9 papers—5 primary·4 cross-listed

01
Three-Nucleon Force Effects in the FSI configuration of the d(n, nn)p Breakup Reaction
Hiroyuki Kamada🇯🇵 · Henryk Witala🇵🇱 · Jacek Golak · Roman Skibinski🇵🇱
We investigated three-nucleon (3N) force effects in the final state interaction (FSI) configuration of the d(n, nn)p breakup reaction at the incoming nucleon energy E n = 200 MeV. Although 3N force effects for the elastic nucleon-deuteron scattering cross section at comparable energies are located predominantly in the region of intermediate and backward angles, the corresponding 3N force effects for the integrated FSI configuration breakup cross section are found also at forward scattering angles.
nucl-thSciPost Phys.Proc.(2020)·0 citations
02
Jet quenching in the hadron gas: an exploratory study
Philipp Dorau🇩🇪 · Jean-Bernard Rose🇩🇪 · Daniel Pablos🇳🇴 · Hannah Elfner🇩🇪
The suppression of high momentum particles in heavy-ion collisions in comparison to elementary reactions is one of the main indications for the formation of a quark-gluon plasma. In recent studies, full jets are being reconstructed and substructure observables are gaining importance in assessing the medium modifications of hard probes. In this work, the effect of the late stage hadronic interactions are explored within the hadronic transport approach SMASH (Simulating Many Accelerated Strongly-interacting Hadrons). High momentum particles are incorporated in a radially expanding hadron gas to analyse the corresponding angular distributions, also refered to as `jet shape' observables. We find that the full hadron gas can be approximated with a pion gas with constant elastic cross-sections of 100 mb. In addition, the temperature and probe energy dependence of diffusion coefficients $q ~$ and $e ~$ quantifying the transverse and parallel momentum transfers are extracted. The species dependence and the importance of different interaction types are investigated. Parametrizations are presented that can be employed in future jet quenching calculations to include the effect of the hadronic phase.
nucl-thhep-phPRC(2020)·28 citations
03
Investigation of the energy levels and the structure of the different states of the 24Mg nucleus
Sahar Aslanzadeh · Mohammad Reza Shojaei · Ali Asghar Mowlavi
In this work, the 24Mg nucleus is considered in the cluster model by solving the Schrodinger and Klein- Gordon equations from the Nikiforov- Uvarov (NU) method. A local potential is used for these two equations that is compatible with the Hafstad-Teller potential. By substituting this potential in the Schrodinger and Klein- Gordon equations, the energy levels and wave functions are obtained from NU method. We obtain a first order equation in terms of E for the Schrodinger equation and a fourth-order equation in terms of ER for the Klein-Gordon equation. Therefore, the obtained equation from the Klein-Gordon equation has both the real solutions and imaginary solutions that we consider only the real solutions for this equation. For more accuracy, the spin-orbit and tensor potentials are added to the central potential as the perturbed terms and the first-order correction value of the energy levels is calculated. These energy levels are used for 24Mg nucleus and the good results are obtained in agreement with the experimental data. Of course, one can see that the calculated results from the Schrodinger and Klein-Gordon equations, i.e. non-relativistic and relativistic respectively, are nearly the same. By using the Coulomb repulsive potential, it is shown that the structure of the ground state and the first excited state of this nucleus is as octahedral and the configuration of the alpha particles for the second excited state is as pentahedral, i.e. as 12C +12C . Finally, we obtain the critical point for the calculation of maximum energy of this nucleus in the cluster model.
nucl-thCan.J.Phys.(2020)·2 citations
04
$Δ$ -mass dependence of the M-matrix in the calculation of $\mbox N Δ \to \mbox N N$ cross sections
Ying Cui🇨🇳 · Yingxun Zhang🇨🇳 · Zhuxia Li🇨🇳
Within the one boson exchange model, $Δ$ -mass dependent M-matrix and its influence on the calculation of $N Δ \to N N$ cross sections are investigated. Our calculations show that the $m_{Δ}$ dependence of $∣ p_{N Δ} ∣$ and $∣ M ∣^{2}$ has effects on the calculations of $σ_{N Δ \to N N}$ , especially around the threshold energy. We finally provide a table of accurate $σ_{N Δ \to N N}$ which can be used in the transport models.
nucl-thhep-phCPC(2020)·8 citations
05
Deeply virtual Compton Scattering off $^{4}$ He
Sara Fucini🇮🇹 · Sergio Scopetta🇮🇹 · Michele Viviani🇮🇹
Deeply virtual Compton scattering is a fascinating process which can provide a tomographic view of nuclei and bound nucleons. The first experimental results for $^{4}$ He targets, recently released at Jefferson Lab, have been analyzed here in a rigorous Impulse Approximation scenario. For both the coherent and incoherent channels of the process, the main experimental observables have been written in terms of state-of-the-art models of the nuclear spectral function and of the parton structure of the bound proton. A good overall agreement with the data is obtained. The calculation shows that a comparison of our conventional results with future precise data can expose novel quark and gluon effects in nuclei.
nucl-thhep-phJ.Phys.Conf.Ser.(2020)·0 citations
06
Neutrino Oscillations and Energy-Momentum Conservation
HoSeong La🇺🇸
It is proposed that the energy-momentum expectation values of flavor states should be identified with the missing energy-momentum of neutrino processes so that the conservation of energy-momentum can be strictly imposed. It is also observed that there is a plausible condition to express neutrino mixing angles in terms of neutrino masses without invoking symmetries.
↳ hep-phnucl-th0 citations
07
Survival of heavy flavored mesons in a hot medium
B.Z. Kopeliovich🇨🇱 · Jan Nemchik🇨🇱 · I.K. Potashnikova🇨🇱 · Ivan Schmidt🇨🇿
Hadronization of heavy quarks reveals various unusual features. Gluon radiation by a heavy quark originated from a hard process, ceases shortly on a distance of the order of few fm. Due to the dead-cone effect a heavy quark radiates only a small fraction of its energy. This is why the measured fragmentation function D(z) peaks at large z. Hadronization finishes at very short distances, well shorter than 1 fm, by production of a colorless small-size Qq-bar dipole. This ensures dominance of a perturbative mechanism and makes possible factorization of short and long distances. The latter corresponds to final state interactions of the produced dipole propagating through a dense medium. The results provide good description of data on beauty and charm suppression in heavy ion collisions, fixing the transport coefficient for b-quarks about twice smaller than for charm, and both significantly lower that the values determined from data on suppression of high-pT light hadrons. We relate this to reduction of the QCD coupling at higher scales, and suppression of radiation by the dead-cone effect.
↳ hep-phnucl-th2 citations
08
Excited bottomonia in quark-gluon plasma from lattice QCD
Rasmus Larsen🇺🇸 · Stefan Meinel🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸
We present the first lattice QCD study of up to $3 S$ and $2 P$ bottomonia at non-zero temperatures. Correlation functions of bottomonia were computed using novel bottomonium operators and a variational technique, within the lattice non-relativistic QCD framework. We analyzed the bottomonium correlation functions based on simple physically-motivated spectral functions. We found evidence of sequential in-medium modifications, in accordance with the sizes of the bottomonium states.
↳ hep-lathep-phnucl-thPLB(2020)·78 citations
09
The electromagnetic form factors of the transition from the spin-3/2 Sigma to the Lambda hyperon
Olov Junker🇸🇪 · Stefan Leupold🇸🇪 · Elisabetta Perotti🇸🇪 · Timea Vitos (Uppsala U.)🇸🇪
The three electromagnetic form factors for the transition from a 3/2+ Sigma* hyperon to the ground-state Lambda hyperon are studied. At low energies, combinations of the transition form factors can be deduced from Dalitz decays of the Sigma* hyperon to Lambda plus an electron-positron pair. It is pointed out how more information can be obtained with the help of the self-analyzing weak decay of the Lambda. In particular it is shown that these transition form factors are complex quantities already in this kinematical region. Such measurements are feasible at hyperon factories as for instance the Facility for Antiproton and Ion Research (FAIR). At higher energies, the transition form factors can be measured in electron-positron collisions. The pertinent relations between the transition form factors and the decay distributions and differential cross sections are presented. Using dispersion theory, the low-energy electromagnetic form factors for the Sigma*-to-Lambda transition are related to the pion vector form factor. The additionally required input, i.e. the two-pion - Sigma* - Lambda amplitudes are determined from relativistic next-to-leading-order (NLO) baryon chiral perturbation theory including the baryons from the octet and the decuplet. A poorly known NLO parameter is fixed to the experimental value of the Sigma* to Lambda-gamma decay width. Pion rescattering is taken into account by dispersion theory solving a Muskhelishvili-Omnes equation. Subtracted and unsubtracted dispersion relations are discussed. However, in view of the fact that the transition form factors are complex quantities, the current data situation does not allow for a full determination of the subtraction constants. To reduce the number of free parameters, unsubtracted dispersion relations are used to make predictions for the transition form factors in the low-energy space- and timelike regions.
↳ hep-phnucl-thPRC(2020)·25 citations

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first authorsco-authorsvia INSPIRE