Nuclear Theory·nucl-th

Wednesday·January 1, 2020

12 papers—3 primary·9 cross-listed

01
Strong-coupling effects of pairing fluctuations, and Anderson-Bogoliubov mode in neutron $^{1}$ S $_{0}$ superfluids in neutron stars
Daisuke Inotani🇯🇵 · Shigehiro Yasui🇯🇵 · Muneto Nitta🇯🇵
We investigate effects of thermal and quantum fluctuations of the superfluid order parameter in $^{1} S_{0}$ superfluids in neutron stars. We construct a separable potential to reproduce the $^{1} S_{0}$ phase shift reconstructed by using the partial wave analysis from nucleon scattering data. We include superfluid fluctuations within a strong-coupling approximation developed by Nozières and Schmitt-Rink and determine self-consistently the superfluid order parameter as well as the chemical potential. We show that the quantum depletion, which gives a fraction of noncondensed neutrons at zero temperature due to quantum pairing fluctuations, plays an important role not only near the critical temperature from superfluid states to normal states but also at zero temperature. We derive the dispersion relation of Anderson-Bogoliubov modes associated with phase fluctuations, and show also that there is a nonzero fraction of noncondensed components in the neutron number as a result of the strong-coupling effect. Our results indicate that superfluid fluctuations are important for thermodynamic properties in neutron stars.
nucl-thcond-mat.quant-gasPRC(2020)·7 citations
02
Hadron properties in a nuclear medium and effective nuclear force from quarks: the quark-meson coupling model
K. Tsushima🇧🇷
We give a short review of the quark-meson coupling (QMC) model, the quark-based model of finite nuclei and hadron interactions in a nuclear medium, highlighting on the relationship with the Skyrme effective nuclear forces. The model is based on a mean field description of nonoverlapping nucleon MIT bags bound by the self-consistent exchange of Lorentz-scalar-isoscalar, Lorentz-vector-isoscalar, and Lorentz-vector-isovector meson fields directly coupled to the light quarks up and down. In conventional nuclear physics the Skyrme effective forces are very popular, but, there is no satisfactory interpretation of the parameters appearing in the Skyrme forces. Comparing a many-body Hamiltonian generated by the QMC model in the zero-range limit with that of the Skyrme force, it is possible to obtain a remarkable agreement between the Skyrme force and the QMC effective interaction. Furthermore, it is shown that 3-body and higher order N-body forces are naturally included in the QMC-generated effective interaction.
nucl-thhep-exhep-phnucl-exAAPPS (Association of Asia Pacific Physic…·3 citations
03
Many-body correlations in nuclear superfluidity
Elena Litvinova🇺🇸 · Peter Schuck🇫🇷
The two-fermion two-point correlation function in the pairing channel is discussed in the equation of motion framework. Starting from the bare two-fermion interaction, we derive the equation of motion for the two-fermion pair propagator in a strongly-correlated medium. The resulting equation is of the Dyson type with the kernel having a static and a one frequency dependent components and, thus, can be regarded as Dyson Bethe-Salpeter equation (Dyson-BSE). The many-body hierarchy generated by the dynamical interaction kernel is truncated on the level of two-body correlation functions, thus neglecting the explicit three-body and higher-rank correlations. The truncation is performed via a cluster expansion of the intermediate three-particle-one-hole correlation function irreducible in the particle-particle channel, that leads to the coupling between single fermions and emergent collective modes of excitation. The latter couplings are, thus, derived in terms of the exact mapping of the in-medium two-fermion correlation functions onto the domain of bosonic quasibound states (phonons) without introducing new parameters. The approach is applied to calculations of the pairing gaps in medium-mass nuclear systems, that include calcium, nickel and tin isotopic chains.
nucl-thPRC(2020)·19 citations
04
Universality in Hadronic and Nuclear Collisions at High Energy
Paolo Castorina🇮🇹 · Alfredo Iorio🇨🇿 · Daniele Lanteri🇮🇹 · Martin Spousta🇨🇿 · Helmut Satz🇩🇪
Recent experimental results in proton-proton and in proton-nucleus collisions at Large Hadron Collider energies show a strong similarity to those observed in nucleus-nucleus collisions, where the formation of a quark-gluon plasma is expected. We discuss the comparison between small colliding systems and nucleus-nucleus collisions, for: a)~the strangeness suppression factor $γ_{s}$ and yields of multi-strange hadrons; b)~the average transverse momentum, $p_{t}$ , with particular attention to the low $p_{t}$ region where soft, non-perturbative effects are important; c)~the elliptic flow scaled by the participant eccentricity. The universal behavior in hadronic and nuclear high energy collisions emerges for all these observables in terms of a specific dynamical variable which corresponds to the entropy density of initial system in the collision and which takes into account the transverse size of the initial configuration and its fluctuations.
↳ hep-phnucl-thPRC(2020)·30 citations
05
Spectrum of the strange hidden charm molecular pentaquarks in chiral effective field theory
Bo Wang🇨🇳 · Lu Meng🇨🇳 · Shi-Lin Zhu🇨🇳
We calculate the effective potentials of the $Ξ_{c} D ˉ^{(*)}$ , $Ξ_{c}^{'} D ˉ^{(*)}$ and $Ξ_{c}^{*} D ˉ^{(*)}$ systems with the chiral effective field theory up to the next-to-leading order. We simultaneously consider the short-, intermediate- and long-range interactions. With the newly observed $P_{c}$ spectra as inputs, we construct the quark-level contact Lagrangians to relate the low energy constants to those of $Σ_{c} D ˉ^{(*)}$ with the help of quark model. Our calculation indicates there are seven bound states in the $I = 0$ strange hidden charm $[Ξ_{c}^{'} D ˉ^{(*)}]_{J} (J = \frac{1}{2}, \frac{3}{2})$ and $[Ξ_{c}^{*} D ˉ^{(*)}]_{J} (J = \frac{1}{2}, \frac{3}{2}, \frac{5}{2})$ systems. Our analyses also disfavor the $Λ_{c} D ˉ^{(*)}$ bound states. However, we obtain three new hadronic molecules in the isoscalar $[Ξ_{c} D ˉ^{(*)}]_{J} (J = \frac{1}{2}, \frac{3}{2})$ systems. The masses of $[Ξ_{c} D ˉ]_{1/2}$ , $[Ξ_{c} D ˉ^{*}]_{1/2}$ and $[Ξ_{c} D ˉ^{*}]_{3/2}$ are predicted to be $4319. 4_{- 3.0}^{+ 2.8}$ MeV, $4456. 9_{- 3.3}^{+ 3.2}$ MeV and $4463. 0_{- 3.0}^{+ 2.8}$ MeV, respectively. We also notice the one-eta-exchange influence is rather feeble. Binding solutions in the $I = 1$ channels are nonexistent. We hope the future analyses at LHCb can seek for these new $P_{cs}$ s in the $J ψ Λ$ final states, especially near the thresholds of $Ξ_{c} D ˉ^{(*)}$ .
↳ hep-phhep-exhep-latnucl-ex+1PRD(2020)·126 citations
06
Collisional dynamics of polaronic clouds immersed in a Fermi sea
Hiroyuki Tajima · Junichi Takahashi · Eiji Nakano · Kei Iida
We propose a new protocol to examine many-polaron properties in a cold atom experiment. Initially, polaronic clouds are prepared around the opposite edges of a majority gas cloud. After time evolution, the collision of two clouds exhibits various polaronic effects. To see how {\it collective} properties of many polarons with mediated interactions appear in the case in which the impurity and majority gases are composed of mass-balanced fermions with different spin components, we perform a nonlinear hydrodynamic simulation for collisional dynamics of two Fermi polaronic clouds. We found that the dynamics is governed by the impurity Fermi pressure, polaron energy, and multi-polaron correlations. In particular, shock waves occur in such a way as to reflect the many-body properties of polarons through the first sound of minority clouds. Our idea is applicable to other systems such as Bose polarons as well as mass-imbalanced mixtures.
↳ cond-mat.quant-gasnucl-thPRA(2020)·6 citations
07
A possible evidence of the gluon condensation effect in cosmic positron and gamma-ray spectra
Wei Zhu🇨🇳 · Peng Liu🇨🇳 · Jianhong Ruan🇨🇳 · Fan Wang🇨🇳
The gluon condensation effect in cosmic proton-proton collisions at high energy is used to explain an excess in the positron spectrum observed by AMS. We find that this excess may originate from the GC-effect in Tycho's supernova remnant.
↳ astro-ph.HEhep-phnucl-thApJ(2020)·12 citations
08
News from bottomonium spectral functions in thermal QCD
Sam Offler🇬🇧 · Gert Aarts🇬🇧 · Chris Allton🇬🇧 · Jonas Glesaaen🇬🇧 · Benjamin Jäger🇩🇰 · Seyong Kim🇰🇷 · Maria Paola Lombardo🇮🇹 · Sinead M. Ryan🇮🇪 · Jon-Ivar Skullerud🇮🇪
New results on bottomonium at nonzero temperature are presented, using the FASTSUM Generation 2L ensembles. Preliminary results for spectral function reconstruction using Kernel Ridge Regression, a machine learning technique, are shown as well and compared to results from the Maximum Entropy Method.
↳ hep-latnucl-thPoS(2019)·23 citations
09
Determination of Chemical Freeze-out Parameters from Net-kaon Fluctuations at RHIC
Jamie M. Stafford🇺🇸 · Paolo Alba🇩🇪 · Rene Bellwied🇺🇸 · Valentina Mantovani-Sarti🇩🇪 · Jacquelyn Noronha-Hostler🇺🇸 · Paolo Parotto🇺🇸 · Israel Portillo-Vazquez🇺🇸 · Claudia Ratti🇺🇸
We calculate the mean-over-variance ratio of the net-kaon fluctuations in the Hadron Resonance Gas (HRG) Model for the five highest energies of the RHIC Beam Energy Scan (BES) for different particle data lists. We compare these results with the latest experimental data from the STAR collaboration in order to extract sets of chemical freeze-out parameters for each list. We focused on the PDG2012 and PDG2016+ particle lists, which differ largely in the number of resonant states. Our analysis determines the effect of the amount of resonances included in the HRG on the freeze-out conditions.
↳ hep-phnucl-thSpringer Proc.Phys.(2020)·5 citations
10
Sensitivity of EDM experiments in paramagnetic atoms and molecules to hadronic CP violation
V. V. Flambaum🇦🇺 · M. Pospelov🇺🇸 · A. Ritz🇨🇦 · Y. V. Stadnik🇦🇺
Experiments searching for the electric dipole moment (EDM) of the electron $d_{e}$ utilise atomic/molecular states with one or more uncompensated electron spins, and these paramagnetic systems have recently achieved remarkable sensitivity to $d_{e}$ . If the source of $C P$ violation resides entirely in the hadronic sector, the two-photon exchange processes between electrons and the nucleus induce $C P$ -odd semileptonic interactions, parametrised by the Wilson coefficient $C_{S P}$ , and provide the dominant source of EDMs in paramagnetic systems instead of $d_{e}$ . We evaluate the $C_{S P}$ coefficients induced by the leading hadronic sources of $C P$ violation, namely nucleon EDMs and $C P$ -odd pion-nucleon couplings, by calculating the nucleon-number-enhanced $C P$ -odd nuclear scalar polarisability, employing chiral perturbation theory at the nucleon level and the Fermi-gas model for the nucleus. This allows us to translate the ACME EDM limits from paramagnetic ThO into novel independent constraints on the QCD theta term $∣ θ ˉ ∣ < 3 \times 1 0^{- 8}$ , proton EDM $∣ d_{p} ∣ < 2 \times 1 0^{- 23} e cm$ , isoscalar $C P$ -odd pion-nucleon coupling $∣ g ˉ_{π N N}^{(1)} ∣ < 4 \times 1 0^{- 10}$ , and colour EDMs of quarks $∣ d ~_{u} - d ~_{d} ∣ < 2 \times 1 0^{- 24} cm$ . We note that further experimental progress with EDM experiments in paramagnetic systems may allow them to rival the sensitivity of EDM experiments with neutrons and diamagnetic atoms to these quantities.
↳ hep-phnucl-thphysics.atom-phPRD(2020)·63 citations
11
Boundary action and profile of effective bosonic strings
A. S. Bakry🇨🇳 · M. A. Deliyergiyev🇵🇱 · A. A. Galal🇪🇬 · M. N. Khalil
The mean-square width of the energy profile of bosonic string is calculated considering two boundary terms in the effective action. The perturbative expansion of the Lorentz-invariant boundary terms at the second and the fourth order in the effective action is taken around the free Nambu-Goto string. The calculation are presented for open strings with Dirichlet boundary condition on cylinder.
↳ hep-thhep-lathep-phnucl-th6 citations
12
Describing Migdal effects in diamond crystal with atom-centered localized Wannier functions
Zheng-Liang Liang🇨🇳 · Lin Zhang🇨🇳 · Fawei Zheng🇨🇳 · Ping Zhang🇨🇳
Recent studies have theoretically investigated the atomic excitation and ionization induced by the dark matter (DM)-nucleus scattering, and it is found that the suddenly recoiled atom is much more likely to excite or lose its electrons than expected. Such phenomenon is called the "Migdal effect". In this paper, we extend the established strategy to describe the Migdal effect in isolated atoms to the case in semiconductors under the framework of tight-binding (TB) approximation. Since the localized aspects of electrons are respected in form of the Wannier functions (WFs), the extension of the existing Migdal approach for isolated atoms is much more natural, while the extensive nature of electrons in solids is reflected in the hopping integrals. We take diamond target as a concrete proof of principle for the methodology, and calculate relevant energy spectra and projected sensitivity of such diamond detector. It turns out that our method as a preliminary attempt is practically effective.
↳ cond-mat.mes-hallhep-phnucl-thPRD(2020)·28 citations

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first authorsco-authorsvia INSPIRE