Nuclear Theory·nucl-th
24 papers—16 primary·8 cross-listed
It is shown, that the energy dependence of the chiral based potentials, responsible for the occurrence of two poles in the sector, is the consequence of applying the on-shell factorization introduced in [E. Oset, A. Ramos, Nucl. Phys. A 635(1998)99]. When the dynamical equation is solved without this approximation, the -matrix has only one pole in the energy region of the resonance.
We calculate the spectral function in pseudoscalar (scalar) channel in the high temperature phase of QCD in presence of a background magnetic field. Spatial and temporal screening masses are determined from the long distance behavior of the corresponding correlation functions.
The 2 cluster structure in B is investigated by the microscopic generator coordinate method (GCM) with the Brink cluster wave functions. With a proper choice of the parameters of the effective interaction, the calculated energy spectrum shows reasonable agreement with the observed low-lying spectra of both parities. On the basis of the calculated radii, monopole and transition strengths, several developed cluster states of B are suggested. For the negative-parity states, in addition to the well-known cluster state, the and states are also proposed as the well-developed cluster states. For the positive-parity states, it is found that many states around the 2 threshold show the feature of developed clusters. In particular, the state is found to have a linear-chain-like structure, which is consistent with the previous antisymmetrized molecular dynamics calculation, but contradicts to the orthogonality condition model calculation. It is also found that many of these positive-parity cluster candidates have the non-negligible isoscalar dipole transition strengths, which require the experimental confirmation.
K. Yoshida · M. Gómez-Ramos · K. Ogata · A. M. Moro
[Background] Proton-induced knockout reactions of the form have experienced a renewed interest in recent years due to the possibility of performing these measurements with rare isotopes, using inverse kinematics. Several theoretical models are being used for the interpretation of these new data, such as the distorted-wave impulse approximation (DWIA), the transition amplitude formulation of the Faddeev equations due to Alt, Grassberger and Sandhas (FAGS) and, more recently, a coupled-channels method here referred to as transfer-to-the-continuum (TC). [Purpose] Our goal is to compare the momentum distributions calculated with the DWIA and TC models for the same reactions, using whenever possible the same inputs (e.g. distorting potential). A comparison with already published results for the FAGS formalism is performed as well. [Method] We choose the C(,)C reaction at an incident energy of 420 MeV/u, which has been previously studied with the FAGS formalism. The knocked-out neutron is assumed to be in a single-particle orbital. Longitudinal and transverse momentum distributions are calculated for different assumed separation energies. [Results] For all cases considered, we find a very good agreement between DWIA and TC results. The energy dependence of the distorting optical potentials is found to affect in a modest way the shape and magnitude of the momentum distributions. Moreover, when relativistic kinematics corrections are omitted, our calculations reproduce remarkably well the FAGS result. [Conclusions] The results found in this work provide confidence on the consistency and accuracy of the DWIA and TC models for analyzing momentum distributions for reactions at intermediate energies.
N. J. Upadhyay · A. Bhagwat · B. K. Jain
Nonlocality in the scattering potential leads to an integro-differential equation.In this equation nonlocality enters through an integral over the nonlocal potential kernel. The resulting Schroedinger equation is usually handled by approximating r,r'-dependence of the nonlocal kernel. The present work proposes a novel method to solve the integro-differential equation. The method, using the mean value theorem of integral calculus, converts the nonhomogeneous term to a homogeneous term. The effective local potential in this equation turns out to be energy independent, but has relative angular momentum dependence. This method has high accuracy and is valid for any form of nonlocality. As illustrative examples, the total and differential cross sections for neutron scattering off 12C, 56Fe and 100Mo nuclei are calculated with this method in the low energy region (up to 10 MeV) and are found to be in good accord with the experiments.
N. Reichelt · W. Schweiger · W.H. Klink
A convenient framework for dealing with hadron structure and hadronic physics in the few-GeV energy range is relativistic quantum mechanics. Unlike relativistic quantum field theory, one deals with a fixed, or at least restricted number of degrees of freedom while maintaining relativistic invariance. For systems of interacting particles this is achieved by means of the, so called, "Bakamjian-Thomas construction", which is a systematic procedure for implementing interaction terms in the generators of the Poincare group such that their algebra is preserved. Doing relativistic quantum mechanics in this way one, however, faces a problem connected with the physical requirement of cluster separability as soon as one has more than two interacting particles. Cluster separability, or sometimes also termed "macroscopic causality", is the property that if a system is subdivided into subsystems which are then separated by a sufficiently large spacelike distance, these subsystems should behave independently. In the present contribution we discuss the problem of cluster separability and sketch the procedure to resolve it.
C. E. Fontoura🇧🇷 · F. Krmpotić🇦🇷 · A. P. Galeão🇧🇷 · C De Conti🇧🇷 · G. Krein🇧🇷
We present a study of the nonmesonic weak decay (NMWD) of charmed hypernuclei using a relativistic formalism. We work within the framework of the independent particle shell model and employ a (,) one-meson-exchange model for the decay dynamics. We implement a fully relativistic treatment of nuclear recoil. Numerical results are obtained for the one-neutron-induced transition NMWD rates of the N. The effect of nuclear recoil is sizable and goes in the direction to decrease the nuclear decay rate. We found that the NMWD decay rate of N is of the same order of magnitude as the partial decay rate for the corresponding mesonic decay , suggesting the feasibility of experimental detection of such heavy-flavor nuclear processes.
A. Dobrowolski · K. Mazurek · A. Góźdź
A collective bands of positive and negative parity could be composed of the vibrations and rotations. The rotations of the octupole configurations can be based either on the axial or the non-axial octupole vibrations. A consistent approach to the quadrupole-octupole collective vibrations coupled with the rotational motion enables to distinguish between various scenarios of disappearance of the E2 transitions in negative-parity bands. The here presented theoretical estimates are compared with the recent experimental energies and transition probabilities in and between the ground-state and low-energy negaive-parity bands in Dy. A realistic collective Hamiltonian contains the potential energy term obtained through the macroscopic-microscopic Strutinsky-like method with particle-number-projected BCS approach and deformation-dependent mass tensor defined in vibrational-rotational, nine-dimensional collective space. The symmetrization procedure ensures the uniqueness of the Hamiltonian eigensolutions with respect to the laboratory coordinate system. This quadrupole-octupole collective approach may also allow to find and/or verify some fingerprints of possible high-order symmetries (e.g. tetrahedral, octahedral,...) in nuclear collective bands.
Cutting off the tail of the Woods-Saxon and generalized Woods-Saxon potentials changes the distribution of the poles of the -matrix considerably. Here we modify the tail of the cut-off Woods-Saxon (CWS) and cut-off generalized Woods-Saxon (CGWS) potentials by attaching Hermite polynomial tails to them beyond the cut. The tails reach the zero value more or less smoothly at the finite ranges of the potential. Reflections of the resonant wave functions can take place at different distances. The starting points of the pole trajectories have been reproduced not only for the real values and the moduli of the starting points but also for the imaginary parts.
A. Baran · Cs. Noszaly · T. Vertse
A renewed version of the computer code GAMOW ~\cite{[Ve82]} is given in which the difficulties in calculating broad neutron resonances are amended. New types of phenomenological neutron potentials with strict finite range are built in. Landscape of the S-matrix can be generated on a given domain of the complex wave number plane and S-matrix poles in the domain are localized. Normalized Gamow wave functions and trajectories of given poles can be calculated optionally.
Carlo Barbieri🇬🇧 · Francesco Raimondi🇬🇧 · Christopher McIlroy🇬🇧
We discuss recent \emph{ab initio} calculations based on self-consistent Green's function theory. It is found that a simple extension of the formalism to account for two-nucleon scattering outside the model space allows to calculate non-soft interactions. With this, it is possible to make predictions for Lattice QCD potentials, obtained so far at pion masses of GeV/c. More traditional calculations that use saturating chiral EFT forces yield a good description of nuclear responses and nucleon knockout spectroscopy.
The first ever numerical solution of five-body Faddeev-Yakubovsky equations is presented in this work. Modern realistic Nucleon-Nucleon Hamiltonians have been tested when describing low energy elastic neutron scattering on He nucleus. Obtained results have been compared with those available in the literature and based on solution of the Schrödinger equation.
We briefly review common features and overlapping issues in hadron and flavor physics focussing on continuum QCD approaches to heavy bound states, their mass spectrum and weak decay constants in different strong interaction models.
Igor Altsybeev · Grigory Feofilov
Recent experimental results revealed large elliptic flow of the charmed hadrons at LHC energies, unexpectedly similar to that of the charged pions. The mentioned measurements are often interpreted using transport models, which incorporate dissociation and recombination mechanisms for charm quarks. In this report, a modified version of the Monte Carlo model with string repulsion is used to calculate azimuthal correlations with charmed hadrons. The string repulsion mechanism may provide significant angular correlations and can be considered as an alternative to thermalization picture.
Bharat Kumar🇮🇳 · S. K. Patra🇮🇳 · B. K. Agrawal🇮🇳
We carry out the study for finite nuclei, infinite nuclear matter and neutron star properties with the newly developed relativistic force named as the Institute Of Physics Bhubaneswar-I(IOPB-I). Using this force, we calculate the binding energies, charge radii and neutron skin thickness for some selected nuclei. From the ground state properties of superheavy element i.e. Z=120, it is noticed that considerable shell gaps appear at neutron numbers N=172, 184 and 198, showing the magicity of these numbers. The low density behavior of the equation of state for pure neutron matter is compatible with other microscopic models. Along with the nuclear symmetry energy, its slope and curvature parameters at the saturation density are consistent with those extracted from various experimental data. We calculate the neutron star properties with the equation of state composed of nucleons and leptons in which are in good agreement with the X-ray observations by Steiner and Nättilä. We find that the maximum mass of the neutron star to be 2.15 and stellar radius 11.936 km . Moreover, the radius and tidal deformability of a {\it canonical} neutron star mass 1.4 come out to be 13.242 km and 3.91010 g cm s respectively within this parameter set.
Paolo Alba🇩🇪 · Valentina Mantovani Sarti🇩🇪 · Jorge Noronha🇧🇷 · Jacquelyn Noronha-Hostler🇺🇸 · Paolo Parotto🇺🇸 · Israel Portillo Vazquez🇺🇸 · Claudia Ratti🇺🇸
The QCD equation of state at zero baryon chemical potential is the only element of the standard dynamical framework to describe heavy ion collisions that can be directly determined from first principles. Continuum extrapolated lattice QCD equations of state have been computed using 2+1 quark flavors (up/down and strange) as well as 2+1+1 flavors to investigate the effect of thermalized charm quarks on QCD thermodynamics. Lattice results have also indicated the presence of new strange resonances that not only contribute to the equation of state of QCD matter but also affect hadronic afterburners used to model the later stages of heavy ion collisions. We investigate how these new developments obtained from first principles calculations affect multiparticle correlations in heavy ion collisions. We compare the commonly used equation of state S95n-v1, which was constructed using what are now considered outdated lattice results and hadron states, to the current state-of-the-art lattice QCD equations of state with 2+1 and 2+1+1 flavors coupled to the most up-to-date hadronic resonances and their decays. New hadronic resonances lead to an enhancement in the hadronic spectra at intermediate . Using an outdated equation of state can directly affect the extraction of the shear viscosity to entropy density ratio, , of the quark-gluon plasma and results for different flow observables. The effects of the QCD equation of state on multiparticle correlations of identified particles are determined for both AuAu GeV and PbPb TeV collisions. New insights into the to puzzle in ultracentral collisions are found. Flow observables of heavier particles exhibit more non-linear behavior regardless of the assumptions about the equation of state, which may provide a new way to constrain the temperature dependence of .
Prashant Kocherlakota🇮🇳 · Pankaj S. Joshi🇮🇳 · Sudip Bhattacharyya🇮🇳 · Chandrachur Chakraborty🇮🇳 · Alak Ray🇮🇳 · Sounak Biswas🇮🇳
A rotating black hole causes the spin-axis of a nearby pulsar to precess due to geodetic and gravitomagnetic frame-dragging effects. The aim of our theoretical work here is to explore how this spin-precession can modify the rate at which pulses are received on earth. Towards this end, we obtain the complete evolution of the beam vectors of pulsars moving on equatorial circular orbits in the Kerr spacetime, relative to asymptotic fixed observers. We proceed to establish that such spin-precession effects can significantly modify observed pulse frequencies and, in specific, we find that the observed pulse frequency rises sharply as the orbit shrinks, potentially providing a new way to locate horizons of Kerr black holes, even if observed for a very short time period. We also discuss implications for detections of sub-millisecond pulsars, pulsar nulling, quasi-periodic oscillations, multiply-peaked pulsar Fourier profiles and how Kerr black holes can potentially be distinguished from naked singularities.
Armen Sedrakian🇩🇪 · Ralf-Arno Tripolt🇮🇹 · Jochen Wambach🇮🇹
We study the two-flavor color superconductivity of low-temperature quark matter in the vicinity of chiral phase transition in the quark-meson model where the interactions between quarks are generated by pion and sigma exchanges. Starting from the Nambu-Gor'kov propagator in real-time formulation we obtain finite temperature (real axis) Eliashberg-type equations for the quark self-energies (gap functions) in terms of the in-medium spectral function of mesons. Exact numerical solutions of the coupled nonlinear integral equations for the real and imaginary parts of the gap function are obtained in the zero temperature limit using a model input spectral function. We find that these components of the gap display a complicated structure with the real part being strongly suppressed above , where is its on-shell value. We find MeV close to the chiral phase transition.
V. P. Goncalves🇧🇷 · G. Sampaio dos Santos🇧🇷 · C. R. Sena🇧🇷
In this paper we present a comprehensive analysis of the inclusive heavy quark photoproduction in , and collisions at Run 2 LHC energies using the Color Dipole formalism. The rapidity distributions and total cross sections for the charm and bottom production are estimated considering the more recent phenomenological models for the dipole - proton scattering amplitude, which are based on the Color Glass Condensate formalism and are able to describe the inclusive and exclusive HERA data. Moreover, we present, by the first time, the predictions for the transverse momentum distributions of the and mesons produced in the photon -- induced interactions.
Nora Brambilla🇩🇪 · Miguel A. Escobedo🇫🇮 · Joan Soto🇪🇸 · Antonio Vairo🇩🇪
We perform a comprehensive study of the time evolution of heavy-quarkonium states in an expanding hot QCD medium by implementing effective field theory techniques in the framework of open quantum systems. The formalism incorporates quarkonium production and its subsequent evolution in the fireball including quarkonium dissociation and recombination. We consider a fireball with a local temperature that is much smaller than the inverse size of the quarkonium and much larger than its binding energy. The calculation is performed at an accuracy that is leading-order in the heavy-quark density expansion and next-to-leading order in the multipole expansion. Within this accuracy, for a smooth variation of the temperature and large times, the evolution equation can be written as a Lindblad equation. We solve the Lindblad equation numerically both for a weakly-coupled quark-gluon plasma and a strongly-coupled medium. As an application, we compute the nuclear modification factor for the and states. We also consider the case of static quarks, which can be solved analytically. Our study fulfils three essential conditions: it conserves the total number of heavy quarks, it accounts for the non-Abelian nature of QCD and it avoids classical approximations.
Yuki Kamiya🇯🇵 · Tetsuo Hyodo🇯🇵
We discuss the relation between the analytic structure of the scattering amplitude and the origin of an eigenstate represented by a pole of the amplitude.If the eigenstate is not dynamically generated by the interaction in the channel of interest, the residue of the pole vanishes in the zero coupling limit. Based on the topological nature of the phase of the scattering amplitude, we show that the pole must encounter with the Castillejo-Dalitz-Dyson (CDD) zero in this limit. It is concluded that the dynamical component of the eigenstate is small if a CDD zero exists near the eigenstate pole. We show that the line shape of the resonance is distorted from the Breit-Wigner form as an observable consequence of the nearby CDD zero. Finally, studying the positions of poles and CDD zeros of the KbarN-piSigma amplitude, we discuss the origin of the eigenstates in the Lambda(1405) region.
Krzysztof M. Graczyk🇵🇱 · Beata E. Kowal🇵🇱
Polarization transfer (PT) observables in the single pion production induced by the charged current interaction of the neutrino with the nucleon are examined. The polarization components of the final nucleon and the charged lepton are calculated within two models for the pion production. The predictions are made for neutrino energy of the order of 1~GeV as well as for the T2K energy distribution. It is demonstrated that the PT observables, the degree of polarization and the polarization components of outgoing fermions, are sensitive on assumptions about the nonresonant background model. In particular it is shown that the normal components of the polarization of the outgoing nucleon and the lepton are determined by the interference between the resonant (RES) and nonresonant (NB) amplitudes. Moreover the sign of the normal component of the polarization of the charged lepton is fixed by the relative sign between the RES and the NB amplitudes.
Le Xuan Chung🇻🇳 · Carlos A. Bertulani🇺🇸 · Peter Egelhof🇩🇪 · Stoyanka Ilieva🇩🇪 · Dao T. Khoa🇻🇳 · Oleg A. Kiselev🇩🇪
The momentum distribution of Be fragments produced by the breakup of Be interacting with a proton target at 700.5 MeV/ energy has been measured at GSI Darmstadt. To obtain the structure information on the anomaly of the neutron shell, the momentum distribution of Be fragments from the one-neutron knockout Be(p,pn) reaction, measured in inverse kinematics, has been analysed in the distorted wave impulse approximation (DWIA) based on a quasi-free scattering scenario. The DWIA analysis shows a surprisingly strong contribution of the neutron orbital in Be to the transverse momentum distribution of the Be fragments. The single-neutron spectroscopic factor deduced from the present knock-out data is 1.39(10), which is significantly larger than that deduced recently from data of Be breakup on a carbon target. This result provides a strong experimental evidence for the dominance of the neutron configuration in the ground state of Be.
N. Chouika🇫🇷 · C. Mezrag🇺🇸 · H. Moutarde🇫🇷 · J. Rodríguez-Quintero🇪🇸
We present a novel approach to compute Generalized Parton Distributions within the Lightfront Wave Function overlap framework. We show how to systematically extend Generalized Parton Distributions computed within the DGLAP region to the ERBL one, fulfilling at the same time both the polynomiality and positivity conditions. We exemplify our method using pion Lightfront Wave Functions inspired by recent results of non-perturbative continuum techniques and algebraic nucleon Lightfront Wave Functions. We also test the robustness of our algorithm on reggeized phenomenological parameterizations. This approach paves the way to a better understanding of the nucleon structure from non-perturbative techniques and to a unification of Generalized Parton Distributions and Transverse Momentum Dependent Parton Distribution Functions phenomenology through Lightfront Wave Functions.
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