Nuclear Theory·nucl-th

Tuesday·September 29, 2020

18 papers—9 primary·9 cross-listed

10
Constraining neutron superfluidity with $r$ -mode physics
Elena M. Kantor · Mikhail E. Gusakov · Vasiliy A. Dommes
We constrain the parameters of neutron superfluidity in the cores of neutron stars making use of the recently proposed effect of resonance stabilization of $r$ -modes. To this end, we, for the first time, calculate the finite-temperature $r$ -mode spectra for realistic models of rotating superfluid neutron stars, accounting for both muons and neutron-proton entrainment in their interiors. We find that the ordinary (normal) $r$ -mode exhibits avoided crossings with superfluid $r$ -modes at certain stellar temperatures and spin frequencies. Near the avoided crossings, the normal $r$ -mode dissipates strongly, which leads to substantial suppression of the $r$ -mode instability there. The extreme sensitivity of the positions of avoided crossings to the neutron superfluidity model allows us to constrain the latter by confronting the calculated spectra with observations of rapidly rotating neutron stars in low-mass X-ray binaries.
↳ astro-ph.HEgr-qcnucl-thPRL(2020)·19 citations
11
Associated production in pp and heavy ion collisions
Hua-Sheng Shao🇫🇷
Associated particle production processes in pp and heavy ion collisions at the LHC are in particular interesting in the sense that they provide unique tools to study double parton scattering (DPS) mechanism. In this talk, I will first review the recent theoretical, phenomenological and experimental developments of DPS in pp collisions. Then, I will focus on the DPS studies in heavy ion collisions, and stress their roles in understanding the cold nuclear matter effects, such as the (poorly known) impact-parameter dependent nuclear parton densities.
↳ hep-phhep-exnucl-exnucl-thPoS(2021)·1 citation
12
Bayesian inference of quark star equation of state using the NICER PSR J0030+0451 data
Ang Li🇨🇳 · Zhi-Qiang Miao🇨🇳 · Jin-Liang Jiang🇨🇳 · Shao-Peng Tang🇨🇳 · Ren-Xin Xu🇨🇳
We constrain the equation of state of quark stars within the Bayesian statistical approach using the mass and radius measurements of PSR J0030+0451 from NICER. Three types of bag models, with and without non-zero finite quark mass and/or superfluidity, are employed for quark stars made up with self-bound strange quark matter. We find the $90%$ posterior credible boundary around the most probable values of the quark star maximum mass is $M_{TOV} = 2.3 8_{- 0.23}^{+ 0.26} M_{⊙}$ , within the model flexibility of the finite quark mass, the quark pairing gap, and the perturbative contribution from the one-gluon exchange. The radius of a canonical $1.4 M_{⊙}$ quark star is $R_{1.4} \sim 12.3 km$ , smaller than the results based on neutron star models.
↳ astro-ph.HEastro-ph.SRnucl-thMNRAS·33 citations
13
Multi-neutron transfer in $^{8}$ He induced reactions near the Coulomb barrier
I. Martel · N. Keeley · K.W. Kemper · K. Rusek
The measured inclusive $^{6}$ He and $^{4}$ He production cross sections of G. Marquínez-Durán {\em et al.}, Phys.\ Rev.\ C {\bf 98}, 034615 (2018) are reexamined and the conclusions concerning the relative importance of 1n and 2n transfer to the production of $^{6}$ He arising from the interaction of a 22 MeV $^{8}$ He beam with a $^{208}$ Pb target revised. A consideration of the kinematics of the 2n-stripping reaction when compared with the measured $^{6}$ He total energy versus angle spectrum places strict limits on the allowed excitation energy of the $^{210}$ Pb residual, so constraining distorted wave Born approximation calculations that the contribution of the 2n stripping process to the inclusive $^{6}$ He production can only be relatively small. It is therefore concluded that the dominant $^{6}$ He production mechanism must be 1n stripping followed by decay of the $^{7}$ He ejectile. Based on this result we present strong arguments in favor of direct, one step four-neutron (4n) stripping as the main mechanism for $^{4}$ He production.
↳ nucl-exnucl-thPRC(2020)·5 citations
14
Flavor decomposition for the proton helicity parton distribution functions
C. Alexandrou (Univ. of Cyprus & The Cyprus Inst.)🇨🇾 · M. Constantinou (Temple Univ.)🇺🇸 · K. Hadjiyiannakou (Univ. of Cyprus)🇨🇾 · K. Jansen (DESY-Zeuthen)🇩🇪 · F. Manigrasso (Univ. of Cyprus, Humboldt Univ., Univ. of Rome Tor Vergata)🇨🇾
We present, for the first time, an \textit{ab initio} calculation of the individual up, down and strange quark helicity parton distribution functions for the proton. The calculation is performed within the twisted mass clover-improved fermion formulation of lattice QCD using one ensemble of dynamical up, down, strange and charm quarks with a pion mass of 260 MeV. The lattice matrix elements are non-perturbatively renormalized and the final results are presented in the $MS$ scheme at a scale of 2 GeV. We give results on the $Δ u^{+} (x)$ and $Δ d^{+} (x)$ , including disconnected quark loop contributions, as well as on the $Δ s^{+} (x)$ . For the latter we achieve unprecedented precision compared to the phenomenological estimates.
↳ hep-lathep-phnucl-thPRL(2021)·51 citations
15
Chemical freeze-out systematics of thermal model analysis using hadron yield ratios
Sumana Bhattacharyya🇮🇳 · Amaresh Jaiswal🇮🇳 · Sutanu Roy🇮🇳
We provide a framework to estimate the systematic uncertainties in chemical freeze-out parameters extracted from $χ^{2}$ analysis of thermal model, using hadron multiplicity ratios in relativistic heavy-ion collision experiments. Using a well known technique of graph theory, we construct all possible sets of independent ratios from available hadron yields and perform $χ^{2}$ minimization on each set. We show that even for ten hadron yields, one obtains a large number ( $1 0^{8}$ ) of independent sets which results in a distribution of extracted freeze-out parameters. We analyze these distributions and compare our results for chemical freeze-out parameters and associated systematic uncertainties with previous results available in the literature.
↳ hep-phhep-exnucl-thPRC(2021)·6 citations
16
Polarization as a signature of local parity violation in hot QCD matter
F. Becattini (Univeristy of Florence)🇮🇹 · M. Buzzegoli (Iowa State U.)🇮🇹 · A. Palermo (University of Florence)🇮🇹 · G. Prokhorov (JINR, Dubna)🇷🇺
We show that local parity violation due to chirality imbalance in relativistic nuclear collisions can be revealed by measuring the projection of the polarization vector onto the momentum, i.e. the helicity, of final state baryons. The proposed method does not require a coupling to the electromagnetic field, like in the Chiral Magnetic Effect. By using linear response theory, we show that, in the presence of a chiral imbalance, the spin 1/2 baryons and anti-baryons receive an additional contribution to the polarization along their momentum and proportional to the axial chemical potential. The additional, parity-breaking, contribution to helicity can be detected by studying helicity-helicity azimuthal angular correlation.
↳ hep-phnucl-thPLB(2021)·22 citations
17
Preparation of excited states for nuclear dynamics on a quantum computer
Alessandro Roggero · Chenyi Gu · Alessandro Baroni · Thomas Papenbrock
We study two different methods to prepare excited states on a quantum computer, a key initial step to study dynamics within linear response theory. The first method uses unitary evolution for a short time $T = O (1 - F)$ to approximate the action of an excitation operator $O^$ with fidelity $F$ and success probability $P \approx 1 - F$ . The second method probabilistically applies the excitation operator using the Linear Combination of Unitaries (LCU) algorithm. We benchmark these techniques on emulated and real quantum devices, using a toy model for thermal neutron-proton capture. Despite its larger memory footprint, the LCU-based method is efficient even on current generation noisy devices and can be implemented at a lower gate cost than a naive analysis would suggest. These findings show that quantum techniques designed to achieve good asymptotic scaling on fault tolerant quantum devices might also provide practical benefits on devices with limited connectivity and gate fidelity.
↳ quant-phnucl-thPRC(2020)·67 citations
18
A Review on Partial-wave Dynamics with Chiral Effective Field Theory and Dispersion Relation
De-Liang Yao🇨🇳 · Ling-Yun Dai🇨🇳 · Han-Qing Zheng🇨🇳 · Zhi-Yong Zhou🇨🇳
The description of strong interaction physics of low-lying resonances is out of the valid range of perturbative QCD. Chiral effective field theories have been developed to tackle the issue. Partial wave dynamics is the systematic tool to decode the underlying physics and reveal the properties of those resonances. It is extremely powerful and helpful for our understanding of the non-perturbative regime, especially when dispersion techniques are utilized simultaneously. Recently, plenty of exotic/ordinary hadrons have been reported by experiment collaborations, e.g. LHCb, Belle, and BESIII, etc.. In this review, we summarize the recent progress on the applications of partial wave dynamics combined with chiral effective field theories and dispersion relations, on related topics, with emphasis on $π π$ , $π K$ , $π N$ and $K ˉ N$ scatterings.
↳ hep-phnucl-thRept.Prog.Phys.(2021)·91 citations

Affiliations

first authorsco-authorsvia INSPIRE