Nuclear Theory·nucl-th

Tuesday·June 22, 2021

19 papers—6 primary·13 cross-listed

01
Hidden variables in angular correlations of the particles emitted in fission
F. F. Karpeshin
A comparative analysis of experiments on studying the (n, f), on one hand, and (n, n), on the other hand, angular correlations in fission is carried out, based on the model proposed by muonic conversion in fragments of prompt fission of 238U with negative muons. Their fundamental difference is shown in the sense of the information that can be inferred from them. Historically, the situation resembles the EPR paradox. An experimental check of the empirical relation between the alignment and polarization parameters, the former is twice as small as the latter one.
nucl-th0 citations
02
A model-agnostic analysis of hybrid stars with reactive interfaces
Germán Lugones🇧🇷 · Mauro Mariani🇦🇷 · Ignacio F. Ranea-Sandoval🇦🇷
We study hybrid stars considering the effects on stellar stability of the hadron-quark conversion speed at the sharp interface. The equation of state is constructed by combining a model-agnostic hadronic description with a constant speed of sound model for quark matter. We show that current LIGO/Virgo, NICER, low-density nuclear and high-density perturbative QCD constraints can be satisfied in two scenarios, with low and high transition pressures. If the conversion speed at the interface is slow, a new class of dynamically stable hybrid objects is possible and very stiff hadronic equations of state cannot be discarded. Densities tens of times larger than the nuclear saturation density are possible at the center of these objects. We discuss possible formation mechanisms for the new class of hybrid stars and smoking guns for their observational identification.
nucl-thastro-ph.HEastro-ph.SRhep-phJCAP(2023)·38 citations
03
On attractor and fixed points in Bjorken flows
Jean-Paul Blaizot🇫🇷 · Li Yan🇨🇳
We consider a plasma of massless particles undergoing Bjorken expansion, mimicking the matter created in ultra-relativistic heavy ion collisions. We study the transition to hydrodynamics using kinetic theory in the relaxation time approximation. By allowing the relaxation time to depend on time, we can monitor the speed of the transition from the collisionless regime to hydrodynamics. By using a special set of moments of the momentum distribution, we reduce the kinetic equation to a coupled mode problem which encompasses all versions of second order viscous hydrodynamics for Bjorken flows. This coupled mode problem is analysed first using techniques of linear algebra. Then we transform this two mode problem into a single non linear differential equation and proceed to a fixed point analysis. We identify an attractor solution as the particular solution of this non linear equation that joins two fixed points: one corresponding to the collisionless, early time regime, the other corresponding to late time hydrodynamics. We exploit the analytic solution of this equation in order to test several approximations and to identify generic features of the transition to hydrodynamics. We argue that extending the accuracy of hydrodynamics to early time, i.e. to the region of large gradients, amounts essentially to improve the accuracy of the location of the collisionless fixed point. This is demonstrated by showing that a simple renormalisation of a second order transport coefficient puts the free streaming fixed point at the right location, and allows us to reproduce accurately the full solution of the kinetic equation within second order viscous hydrodynamics, even in regimes far from local equilibrium.
nucl-thhep-phPRC(2021)·53 citations
04
Multi-messenger heavy-ion collision physics
Charles Gale🇨🇦 · Jean-François Paquet🇺🇸 · Björn Schenke🇺🇸 · Chun Shen🇺🇸
This work studies the production of direct photons in relativistic nuclear collisions, along with the production of hadrons. Radiation from the very first instants to the final moments of the evolution is included. The hybrid model used here describes all stages of relativistic heavy-ion collisions. Chronologically, those are an initial state reflecting the collision of nuclei described within the Color Glass Condensate effective theory; a pre-equilibrium phase based on non-equilibrium linear response; relativistic viscous hydrodynamics, and a hadronic afterburner. The effect of the pre-equilibrium phase on both photonic and hadronic observables is highlighted for the first time. The potential of photon observables -- spectrum, differential elliptic and triangular flow -- to reveal the chemical equilibration time is studied. Finally, we consider "small collision systems", including proton+nucleus collisions and collisions of light nuclei, as probed by hadronic and electromagnetic observables. We demonstrate how photon production can signal the formation of quark-gluon plasma in such small systems.
nucl-thhep-phnucl-exPRC(2022)·122 citations
05
Unraveling the Flux-Averaged Neutrino-Nucleus Cross Section
Omar Benhar🇮🇹
The interpretation of the nuclear cross sections measured using accelerator neutrino beams involve severe difficulties, arising primarily from the average over the incoming neutrino flux. The broad energy distribution of the beam particles hampers the determination of the energy transfer to the nuclear target, the knowledge of which is needed to pin down the dominant reaction mechanism. Overcoming this problem requires the development of a theoretical approach suitable to describe neutrino interactions at energies ranging from hundreds of MeV to few GeV. In this paper, it is argued that the approach based on the factorisation of the nuclear cross section provides a consistent framework for the calculation of neutrino-nucleus interactions in both the quasi elastic and inelastic channels. The near-degeneracy between theoretical models based on different assumptions, and the use of electron scattering data to advance the understanding of neutrino-nucleus cross sections are also discussed.
nucl-thhep-phEur.Phys.J.ST(2021)·0 citations
06
Analysis of the neutron matter equation of state and the symmetry energy up to fourth order of chiral effective field theory
Francesca Sammarruca🇺🇸 · Randy Millerson🇺🇸
We present predictions for the neutron matter equation of state, from leading to fourth order of chiral effective field theory, using recently developed, accurate chiral nucleon-nucleon potentials. We find the impact of subleading three-neutron forces to be mild and attractive. We also show order-by-order predictions for the symmetry energy, and discuss its density dependence in relation to empirical constraints.
nucl-thPRC(2021)·20 citations
07
Feeble DM-SM Interaction via New Scalar and Vector Mediators in Rotating Neutron Stars
Atanu Guha🇮🇳 · Debashree Sen🇮🇳
We investigate the possible presence of dark matter (DM) in massive and rotating neutron stars (NSs). For the purpose we extend our previous work [1] to introduce a light new physics vector mediator besides a scalar one in order to ensure feeble interaction between fermionic DM and $β$ stable hadronic matter in NSs. The masses of DM fermion, the mediators and the couplings are chosen consistent with the self-interaction constraint from Bullet cluster and from present day relic abundance. Assuming that both the scalar and vector mediators contribute equally to the relic abundance, we compute the equation of state (EoS) of the DM admixed NSs to find that the present consideration of the vector new physics mediator do not bring any significant change to the EoS and static NS properties of DM admixed NSs compared to the case where only the scalar mediator was considered [1]. However, the obtained structural properties in static conditions are in good agreement with the various constraints on them from massive pulsars like PSR J0348+0432 and PSR J0740+6620, the gravitational wave (GW170817) data and the recently obtained results of NICER experiments for PSR J0030+0451 and PSR J0740+6620. We also extended our work to compute the rotational properties of DM admixed NSs rotating at different angular velocities. The present results in this regard suggest that the secondary component of GW190814 may be a rapidly rotating massive DM admixed NS. The constraints on rotational frequency from pulsars like PSR B1937+21 and PSR J1748-2446ad are also satisfied by our present results. Also, the constraints on moment of inertia are satisfied considering slow rotation. The universality relation in terms of normalized moment of inertia also holds good with our DM admixed EoS.
↳ hep-phastro-ph.COastro-ph.HEnucl-thJCAP(2021)·39 citations
08
Charge Radius of Neutron-deficient $^{54}$ Ni and Symmetry Energy Constraints Using the Difference in Mirror Pair Charge Radii
Skyy V. Pineda🇺🇸 · Kristian König🇺🇸 · Dominic M. Rossi🇩🇪 · B. Alex Brown🇺🇸 · Anthony Incorvati🇺🇸 · Jeremy Lantis🇺🇸 · Kei Minamisono🇺🇸 · Wilfried Nörtershäuser🇩🇪 · Jorge Piekarewicz🇺🇸 · Robert Powel🇺🇸 · Felix Sommer🇩🇪
The nuclear root-mean-square charge radius of $^{54}$ Ni was determined with collinear laser spectroscopy to be $R (^{54}$ Ni) = 3.737\,(3)~fm. In conjunction with the known radius of the mirror nucleus $^{54}$ Fe, the difference of the charge radii was extracted as $Δ R_{ch}$ = 0.049\,(4)~fm. Based on the correlation between $Δ R_{ch}$ and the slope of the symmetry energy at nuclear saturation density ( $L$ ), we deduced $20 \leq L \leq 70$ \,MeV. The present result is consistent with the $L$ from the binary neutron star merger GW170817, favoring a soft neutron matter EOS, and barely consistent with the PREX-2 result within 1 $σ$ error bands. Our result indicates the neutron-skin thickness of $^{48}$ Ca as 0.15\,-\,0.19\,fm.
↳ nucl-exnucl-thPRL(2021)·80 citations
09
Is two-poles' $Λ (1405)$ one state or two?
Zhong-Yu Wang🇨🇳 · Hiwa A. Ahmed🇨🇳 · C. W. Xiao🇨🇳
To understand the nature of two poles for the $Λ (1405)$ state, we revisit the interactions of $K ˉ N$ and $π Σ$ with their coupled channels, where two-poles structure is found in the second Riemann sheet. We also dynamically generate two poles in the single channel interaction of $K ˉ N$ and $π Σ$ , respectively. Moreover, we make a further study of two poles' properties by evaluating the couplings, the compositeness, the wave functions, and the radii for the interactions of four coupled channels, two coupled channels and the single channel. Our results show that the nature of two poles is unique. The higher-mass pole is a pure $K ˉ N$ molecule, and the lower-mass one is a compositeness of mainly $π Σ$ with tiny component $K ˉ N$ . From our results, one can conclude that the $Λ (1405)$ state would be overlapped with two different states of the same quantum number.
↳ hep-phnucl-thEPJC(2021)·11 citations
10
Study of $N (1440)$ structure via $γ^{*} p \to N (1440)$ transition
A. Kaewsnod🇹🇭 · K. Xu🇹🇭 · Z. Zhao🇹🇭 · X. Y. Liu🇹🇭 · S. Srisuphaphon🇹🇭 · A. Limphirat🇹🇭 · Y. Yan🇹🇭
We study the photoproduction of the $N (1440)$ resonance in $γ^{*} p \to N^{*}$ process in quark models, where the $N (1440)$ takes different wave functions: first radial excitation of the nucleon imported from low-lying baryon mass spectrum calculations, a general radial excitation of the nucleon, and a $q^{3}$ state with positive parity. The comparison between the theoretical results and experimental data on the helicity amplitudes $A_{1/2}$ and $S_{1/2}$ and the analysis of the spatial wave function of the $N (1440)$ resonance reveal that the $N (1440)$ resonance is mainly the $q^{3}$ first radial excitation.
↳ hep-phnucl-thPRD(2022)·6 citations
11
Semileptonic decays $D \to η π e^{+} ν_{e}$ in the $a_{0} (980)$ region
N.N. Achasov🇷🇺 · A.V. Kiselev🇷🇺 · G.N. Shestakov🇷🇺
The mechanism of the four-quark production of the light scalar isovector four-quark state $a_{0} (980)$ in the $D \to η π e^{+} ν_{e}$ decays is discussed. It is shown that the characteristic features of the shape of the $η π$ mass spectra expected in our scheme can serve as the indicator of the production mechanism and internal structure of the $a_{0} (980)$ resonance.
↳ hep-phhep-exnucl-thPRD(2021)·13 citations
12
Accessing Topological Fluctuations of Gauge Fields with Chiral Magnetic Effect
Anping Huang🇨🇳 · Shuzhe Shi🇨🇦 · Shu Lin🇨🇳 · Xingyu Guo🇨🇳 · Jinfeng Liao🇺🇸
Gauge fields provide the fundamental interactions in the Standard Model of particle physics. Gauge field configurations with nontrivial topological windings are known to play crucial roles in many important phenomena, from matter-anti-matter asymmetry of today's universe to spontaneous chiral symmetry breaking in strong interaction. Their presence is however elusive for direct detection in experiments. Here we show that measurements of the chiral magnetic effect (CME) in heavy ion collisions can be used for accessing the topological fluctuations of the non-Abelian gauge fields in the Quantum Chromodynamics (QCD). To achieve this, we implemented a key ingredient, the stochastic dynamics of gauge field topological fluctuations, into a state-of-the-art framework for simulating the CME in these collisions. This new framework provides the necessary tool to quantify initial topological fluctuations from any definitive CME signal to be extracted from experimental data. It also reveals a universal scaling relation between initial topological fluctuations and particle multiplicity produced in the corresponding collision events.
↳ hep-phhep-thnucl-exnucl-thPRD(2023)·3 citations
13
Filtering states with total spin on a quantum computer
Pooja Siwach🇮🇳 · Denis Lacroix🇫🇷
Starting from a general wave function described on a set of spins/qubits, we propose several quantum algorithms to extract the components of this state on eigenstates of the total spin $S^{2}$ and its azimuthal projection $S_{z}$ . The method plays the role of total spin projection and gives access to the amplitudes of the initial state on a total spin basis. The different algorithms have various degrees of sophistication depending on the requested tasks. They can either solely project onto the subspace with good total spin or completely uplift the degeneracy in this subspace. After each measurement, the state collapses to one of the spin eigenstates that could be used for post-processing. For this reason, we call the method Total Quantum Spin filtering (TQSf). Possible applications ranging from many-body physics to random number generators are discussed.
↳ quant-phcond-mat.str-elnucl-thPRA(2021)·32 citations
14
Universal many-body diffusion from momentum dephasing
Maurício Hippert🇺🇸 · Gabriel T. Landi🇧🇷 · Jorge Noronha🇺🇸
The open dynamics of quantum many-body systems involve not only the exchange of energy, but also of other conserved quantities, such as momentum. This leads to additional decoherence, which may have a profound impact in the dynamics. Motivated by this, we consider a many-body system subject to total momentum dephasing and show that under very general conditions this leads to a diffusive component in the dynamics of any local density, even far from equilibrium. Such component will usually have an intricate interplay with the unitary dynamics. To illustrate this, we consider the case of a superfluid and show that momentum dephasing introduces a damping in the sound-wave dispersion relation, similar to that predicted by the Navier-Stokes equation for ordinary fluids. Finally, we also study the effects of dephasing in linear response, and show that it leads to a universal additive contribution to the diffusion constant, which can be obtained from a Kubo formula.
↳ cond-mat.quant-gashep-thnucl-thquant-ph2 citations
15
Strong decays of the low-lying doubly bottom baryons
Hui-Zhen He🇨🇳 · Wei Liang🇨🇳 · Qi-Fang Lü🇨🇳
In this work, we adopt the $^{3} P_{0}$ model to investigate the strong decays of the low-lying doubly bottom baryons in the $j - j$ coupling scheme systematically. In this scheme, we construct the formulism of $^{3} P_{0}$ model under the spectator assumption, and then the heavy diquark symmetry is preserved automatically. Our results show that some of the $λ$ -mode $Ξ_{bb} (1 P)$ and $Ω_{bb} (1 P)$ states are narrow, which have good potentials to be observed by future experiments. For the low-lying $ρ$ -mode and $ρ$ - $λ$ hybrid states, the Okubo-Zweig-Iizuka-allowed strong decays are highly suppressed and they should be extremely narrow. Future experiments can test our phenomenological predictions at the quark level.
↳ hep-phhep-exnucl-thPRD(2022)·12 citations
16
Antistars or antimatter cores in mirror neutron stars?
Zurab Berezhiani🇮🇹
The oscillation of the neutron $n$ into mirror neutron $n^{'}$ , its partner from dark mirror sector, can gradually transform an ordinary neutron star into a mixed star consisting in part of mirror dark matter. The implications of the reverse process taking place in the mirror neutron stars depend on the sign of baryon asymmetry in mirror sector. Namely, if it is negative, as predicted by certain baryogenesis scenarios, then $n ˉ^{'} - n ˉ$ transitions create a core of our antimatter gravitationally trapped in the mirror star interior. The annihilation of accreted gas on such antimatter cores could explain the origin $γ$ -source candidates, with unusual spectrum compatible to baryon-antibaryon annihilation, recently identified in the Fermi LAT catalog, In addition, some part of this antimatter escaping after the mergers of mirror neutron stars can produce the flux of cosmic antihelium and also heavier antinuclei which are hunted in the AMS-02 experiment.
↳ astro-ph.HEastro-ph.COhep-phnucl-thUniverse(2022)·17 citations
17
Studying VLOCV twin compact stars with binary mergers
Z. Sharifi🇮🇷 · M. Bigdeli🇮🇷 · D. Alvarez-Castillo🇵🇱
GW170817 has provided valuable constraints on the equations of state of merging binary neutron stars, which can be considered as the most probable candidate for the source of gravitational waves. On the other hand, these natural laboratories of extreme temperature and density may lead to the estimation of some exotic matter like {deconfined quark matter in their cores}. In this paper, we investigate the neutron star matter equation of state (EoS) with the lowest order constrained variational (LOCV) method considering the excluded volume effect (VLOCV) for nucleons {to} compute the tidal deformability of binary neutron star mergers (BNSMs). Within this approach, the size of nucleons makes the EoS {so} stiff that requires a phase transition in order to avoid causality violation. Therefore, this phase transition {may lead} to the appearance of the third family of compact stars {including} ``twin star'' configurations. {Our EoS models are confronted with observations from GW170817, GW190814, GW190425, and also NICER. We find out that regarding all these constraints, the EoS models having the {transition} pressure $\approx$ 30-100 MeV/fm $^{3}$ and the energy density discontinuity $Δ ε$ $≲$ 300 MeV/fm $^{3}$ are preferable.
↳ astro-ph.HEhep-phnucl-thPRD(2021)·17 citations
18
The importance of kinematic twists and genuine saturation effects in dijet production at the Electron-Ion Collider
Renaud Boussarie🇫🇷 · Heikki Mäntysaari🇫🇮 · Farid Salazar🇺🇸 · Björn Schenke🇺🇸
We compute the differential yield for quark anti-quark dijet production in high-energy electron-proton and electron-nucleus collisions at small $x$ as a function of the relative momentum $P_{⊥}$ and momentum imbalance $k_{⊥}$ of the dijet system for different photon virtualities $Q^{2}$ , and study the elliptic and quadrangular anisotropies in the relative angle between $P_{⊥}$ and $k_{⊥}$ . We review and extend the analysis in [1], which compared the results of the Color Glass Condensate (CGC) with those obtained using the transverse momentum dependent (TMD) framework. In particular, we include in our comparison the improved TMD (ITMD) framework, which resums kinematic power corrections of the ratio $k_{⊥}$ over the hard scale $Q_{⊥}$ . By comparing ITMD and CGC results we are able to isolate genuine higher saturation contributions in the ratio $Q_{s} / Q_{⊥}$ which are resummed only in the CGC. These saturation contributions are in addition to those in the WeizsäckerWilliams gluon TMD that appear in powers of $Q_{s} / k_{⊥}$ . We provide numerical estimates of these contributions for inclusive dijet production at the future Electron-Ion Collider, and identify kinematic windows where they can become relevant in the measurement of dijet and dihadron azimuthal correlations. We argue that such measurements will allow the detailed experimental study of both kinematic power corrections and genuine gluon saturation effects.
↳ hep-phnucl-thJHEP(2021)·74 citations
19
Variational coupled cluster for ground and excited states
Antoine Marie🇫🇷 · Fábris Kossoski🇫🇷 · Pierre-François Loos🇫🇷
In single-reference coupled-cluster (CC) methods, one has to solve a set of non-linear polynomial equations in order to determine the so-called amplitudes which are then used to compute the energy and other properties. Although it is of common practice to converge to the (lowest-energy) ground-state solution, it is also possible, thanks to tailored algorithms, to access higher-energy roots of these equations which may or may not correspond to genuine excited states. Here, we explore the structure of the energy landscape of variational CC (VCC) and we compare it with its (projected) traditional version (TCC) in the case where the excitation operator is restricted to paired double excitations (pCCD). By investigating two model systems (the symmetric stretching of the linear \ce{H4} molecule and the continuous deformation of the square \ce{H4} molecule into a rectangular arrangement) in the presence of weak and strong correlations, the performance of VpCCD and TpCCD are gauged against their configuration interaction (CI) equivalent, known as doubly-occupied CI (DOCI), for reference Slater determinants made of ground- or excited-state Hartree-Fock orbitals or state-specific orbitals optimized directly at the VpCCD level. The influence of spatial symmetry breaking is also investigated.
↳ physics.chem-phcond-mat.mtrl-scicond-mat.str-elnucl-th+1J.Chem.Phys.(2021)·14 citations

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