Nuclear Theory·nucl-th
17 papers—3 primary·14 cross-listed
N.N. Achasov🇷🇺 · A.V. Kiselev🇷🇺
The decays and (and the charge conjugated ones) is the direct probe of the two-quark components in the and wave functions. Recent BESIII experiment is the first step in experimental study of these decays. We present a possible variant of invariant mass distribution when has no component at all.
M. S. Hussein · J. G. G. S. Ramos
We discuss the phenomenon of universal fluctuations in mesoscopic systems and nuclei. For this purpose we use Random Matrix Theory (RMT). The statistical -matrix is used to obtain the physical observables in the case of Quantum Dots, both the Schrödinger and the Dirac types. To obtain analytical results, we use the Stub model. In all cases we concentrate our attention on the average density of maxima in the fluctuating observables, such as the electronic conductance. The case of neutron capture by a variety of nuclei at thermal energies is also considered. Here the average density of maxima in the cross section vs. the mass number is analysed and traced to astrophysical conditions.
Youhei Masada🇯🇵 · Kei Kotake🇯🇵 · Tomoya Takiwaki🇯🇵 · Naoki Yamamoto🇯🇵
Macroscopic evolution of relativistic charged matter with chirality imbalance is described by the chiral magnetohydrodynamics (chiral MHD). One such astrophysical system is high-density lepton matter in core-collapse supernovae where the chirality imbalance of leptons is generated by the parity-violating weak processes. After developing the chiral MHD equations for this system, we perform numerical simulations for the real-time evolutions of magnetic and flow fields, and study the properties of the chiral MHD turbulence. In particular, we observe the inverse cascade of the magnetic energy and the fluid kinetic energy. Our results suggest that the chiral effects that have been neglected so far can reverse the turbulent cascade direction from direct to inverse cascade, which would impact the magnetohydrodynamics evolution in the supernova core toward explosion.
B. Pasquini (Pavia U. & INFN, Pavia)🇮🇹 · M. Vanderhaeghen (Mainz U., Inst. Kernphysik & U. Mainz, PRISMA)🇩🇪
We review various applications of dispersion relations (DRs) to the electromagnetic structure of hadrons. We discuss the way DRs allow one to extract information on hadron structure constants by connecting information from complementary scattering processes. We consider the real and virtual Compton scattering processes off the proton, and summarize recent advances in the DR analysis of experimental data to extract the proton polarizabilities, in comparison with alternative studies based on chiral effective field theories. We discuss a multipole analysis of real Compton scattering data, along with a DR fit of the energy-dependent dynamical polarizabilities. Furthermore, we review new sum rules for the double-virtual Compton scattering process off the proton, which allow for model independent relations between polarizabilities in real and virtual Compton scattering, and moments of nucleon structure functions. The information on the double-virtual Compton scattering is used to predict and constrain the polarizability corrections to muonic hydrogen spectroscopy.
Nodoka Yamanaka🇫🇷 · Shoji Hashimoto🇯🇵 · Takashi Kaneko🇯🇵 · Hiroshi Ohki (JLQCD Collaboration)🇯🇵
We calculate the scalar and tensor charges of the nucleon in 2+1-flavor lattice QCD, for which the systematics of the renormalization of the disconnected diagram is well controlled. Numerical simulations are performed at a single lattice spacing a = 0.11 fm. We simulate four pion masses, which cover a range of 290 - 540 MeV, and a single strange quark mass close to its physical value. The statistical accuracy is improved by employing the so-called low-mode averaging technique and the truncated solver method. We study up, down, and strange quark contributions to the nucleon charges by calculating disconnected diagrams using the all-to-all quark propagator. Chiral symmetry is exactly preserved by using the overlap quark action to avoid operator mixing among different flavors, which complicates the renormalization of scalar and tensor matrix elements and leads to possibly large contamination to the small strange quark contributions. We also study the nucleon axial charge with contribution from the disconnected diagram. Our results are in reasonable agreement with experiments and previous lattice studies.
V.A.B. Zagatto · F. Cappuzzello · J. Lubian · M. Cavallaro · R. Linares · D. Carbone · C. Agodi · A. Foti · S. Tudisco · J.S. Wang · J.R.B. Oliveira · M. S. Hussein
The elastic scattering angular distribution of the ONi system at MeV was measured in the range of the Rutherford cross section down to orders of magnitude below. The cross sections of the lowest and inelastic states of the target were also measured over a several orders of magnitude range. Coupled channel (CC) calculations were performed and are shown to be compatible with the whole set of data only when including the excitation of the projectile and when the deformations of the imaginary part of the nuclear optical potential are taken into account. Similar results were obtained when the procedure is applied to the existing data on OAl elastic and inelastic scattering at and MeV. An analysis in terms of Dynamical Polarization Potentials (DPP) indicate the major role of coupled channel effects in the overlapping surface region of the colliding nuclei.
The hidden charm resonance is usually thought to be a meson-antimeson molecule with quantum numbers . If this is the case, there is the possibility that there might be three body bound states with two charmed mesons and a charmed antimeson. Here we argue that the theoretical existence of this type of three body molecules is expected from heavy quark spin symmetry. If applied to the two body sector, this symmetry implies that the interaction of the meson-antimeson pair in the channel is the same as in the case. From this we can infer that the molecule will be able to display the Efimov effect if the scattering length of the channel is close enough to the unitary limit. Heavy quark spin symmetry also indicates that the molecule is analogous to the one. That is, it can also have a geometric spectrum. If we consider these triply heavy trimers in the isospin symmetric limit, the Efimov effect disappears and we can in principle predict the fundamental state of the and systems. The same applies to the system: if the is an isovector molecule then the isodoublet and the , isoquartet trimers might bind, but do not display Efimov physics. Finally from heavy flavour symmetry it can be argued that scattering in the two-body system might be resonant. This would in turn imply the possibility of Efimov physics in the three body system.
The density dependence of the nuclear symmetry energy governs important aspects of very neutron rich systems such as heavy nuclei and their collisions, neutron stars and their mergers. Many analyses of experimental data have generated constraints on the symmetry energy and its first derivative at saturation density, rho_0 ~ 2.7xE14 g/cm3. We show that each analysis does not accurately constrain the symmetry energy at rho_0, but rather at a lower density, rho_s, that is most sensitively probed by that analysis. Using published constraints on the symmetry energy and its first derivative at rho_0, we constrain the symmetry energy within a density range of 0.25rho_0 to 0.75rho_0 that is relevant to the inner crusts of neutron stars and to the neutrino-sphere of core-collapse supernovae. With appropriate data, the symmetry energy can be similarly constrained over a wider density range.
I. G. Aznauryan🇦🇲 · V. D. Burkert🇺🇸
We report the predictions for the 3q core contributions to the electroexcitation of the resonances Delta(1232)3/2+, N(1440)1/2+, N(1520)3/2-, N(1535)1/2-, and N(1675)5/2- on the proton obtained in the light-front relativistic quark model (LF RQM). For these states, experimental data on the electroexcitation transition amplitudes allow us to make comparison between the experiment and LF RQM predictions in wide range of Q2 and also to quantify the expected meson-baryon contributions as a function of Q2.
Jiaxing Zhao🇨🇳 · Shuzhe Shi🇺🇸 · Nu Xu🇨🇳 · Pengfei Zhuang🇨🇳
Heavy quarks are initially produced in nuclear collisions and the number is conserved during the evolution of the system. We establish a sequential coalescence model with charm conservation and apply it to charmed hadron production at RHIC and LHC energies. The charm conservation enhances the earlier formed hadrons and reduces the later formed ones, which leads to a enhancement and a suppression. The mass dependence of the sequential hadron formation provides us a new tool for studying the quark-gluon plasma hadronization in high energy nuclear collisions.
Egle Tomasi-Gustafsson🇫🇷 · Simone Pacetti🇮🇹
After recalling the arguments for possible excess of two-photon contribution over -counting, model independent statements about the consequences on the observables will be given. The relevant experimental data are discussed: (polarized and unpolarized) electron and positron elastic scattering on the proton, as well as annihilation data. A reanalysis of unpolarized electron-proton elastic scattering data is presented in terms of the electric to magnetic form factor squared ratio. This observable is in principle more robust against experimental correlations and global normalizations. The present analysis shows indeed that it is a useful quantity that contains reliable and coherent information. The comparison with the ratio extracted from the measurement of the longitudinal to transverse polarization of the recoil proton in polarized electron-proton scattering shows that the results are compatible. These results bring a decisive piece of information in the controversy on the deviation of the proton form factors from the dipole dependence.
The Skyrme model is extended with a sextic derivative term - called the BPS-Skyrme term - and a repulsive potential term - called the loosely bound potential. A large part of the model's parameter space is studied for the 4-Skyrmion which corresponds to the Helium-4 nucleus and emphasis is put on preserving as much of the platonic symmetries as possible whilst reducing the binding energies. We reach classical binding energies for Helium-4 as low as 0.2%, while retaining the cubic symmetry of the 4-Skyrmion, and after taking into account the quantum mass correction to the nucleon due to spin/isospin quantization, we get total binding energies as low as 3.6% - still with the cubic symmetry intact.
Gunnar S. Bali🇩🇪 · Bastian B. Brandt🇩🇪 · Gergely Endrodi🇩🇪 · Benjamin Glaessle🇩🇪
The leptonic decay of charged pions is investigated in the presence of background magnetic fields. In this situation Lorentz symmetry is broken and new fundamental decay constants need to be introduced, associated with the decay via the vector part of the electroweak current. We calculate the magnetic field-dependence of both the usual and a new decay constant non-perturbatively on the lattice. We employ both Wilson and staggered quarks and extrapolate the results to the continuum limit. With this non-perturbative input we calculate the tree-level electroweak amplitude for the full decay rate in strong magnetic fields. We find that the muonic decay of the charged pion is enhanced drastically by the magnetic field. We comment on possible astrophysical implications.
Mao-Jun Yan🇨🇳 · Xiao-Hai Liu🇩🇪 · Sergi Gonzàlez-Solís🇨🇳 · Feng-Kun Guo🇨🇳 · Christoph Hanhart🇩🇪 · Ulf-G. Meißner🇩🇪 · Bing-Song Zou🇨🇳
The discovery of by the LHCb Collaboration triggers predictions of more doubly charmed baryons. By taking into account both the -wave excitations between the two charm quarks and the scattering of light pseudoscalar mesons off the ground state doubly charmed baryons, a set of negative-parity spin-1/2 doubly charmed baryons are predicted already from a unitarized version of leading order chiral perturbation theory. Moreover, employing heavy antiquark-diquark symmetry the relevant low-energy constants in the next-to-leading order are connected with those describing light pseudoscalar mesons scattering off charmed mesons, which have been well determined from lattice calculations and experimental data. Our calculations result in a spectrum richer than that of heavy mesons. We find two very narrow , which very likely decay into breaking isospin symmetry. In the isospin-1/2 sector, three states are predicted to exist below 4.2~GeV with the lowest one being narrow and the other two rather broad. We suggest to search for the states in the mode. Searching for them and their analogues are helpful to establish the hadron spectrum.
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