Nuclear Theory·nucl-th

Wednesday·November 13, 2019

12 papers—6 primary·6 cross-listed

01
Comparative study of the direct $α + d$ $\to$ $^{6}$ Li + $γ$ astrophysical capture reaction in few-body models
E.M. Tursunov · S.A. Turakulov · A.S. Kadyrov
A comparative analysis of the astrophysical S factor and the reaction rate for the direct $α (d, γ)^{6} Li$ capture reaction, and the primordial abundance of the $^{6}$ Li element, resulting from two-body, three-body and combined cluster models is presented. It is shown that the two-body model, based on the exact-mass prescription, can not correctly describe the dependence of the isospin-forbidden E1 S factor on energy and does not reproduce the temperature dependence of the reaction rate from the direct LUNA data. It is demonstrated that the isospin-forbidden E1 astrophysical S factor is very sensitive to the orthogonalization procedure of Pauli-forbidden states within the three-body model. On the other hand, the E2 S factor does not depend on the orthogonalization method. This insures that the orthogonolizing pseudopotentials method yields a very good description of the LUNA collaboration's low-energy direct data. At the same time, the SUSY transformation significantly underestimates the data from the LUNA collaboration. On the other hand, the energy dependence of the E1 S factor are the same in both methods. The best description of the LUNA data for the astrophysical S factor and the reaction rates is obtained within the combined E1(three-body OPP)+E2(two-body) model. It yields a value of $(0.72 \pm 0.01) \times 1 0^{- 14}$ for the $^{6}$ Li/H primordial abundance ratio, consistent with the estimation $(0.80 \pm 0.18) \times 1 0^{- 14}$ of the LUNA collaboration. For the $^{6} Li /^{7} Li$ abundance ratio an estimation $(1.40 \pm 0.12) \times 1 0^{- 5}$ is obtained in good agreement with the Standard Model prediction.
nucl-thastro-ph.COastro-ph.SRNPA(2020)·14 citations
02
Production of hypernuclei and properties of hyper-nuclear matter
Alexander Botvina🇷🇺 · Marcus Bleicher🇩🇪 · Nihal Buyukcizmeci🇹🇷
The relativistic nucleus-nucleus collisions can produce hypernuclei and low-temperature hyper-matter as a result of hyperon capture by nuclear residues and free nucleons. We use the transport, coalescence and statistical models to describe the whole process, and point at the important advantages of such reactions: A broad variety of formed hypernuclei in masses and isospin allows for investigating properties of exotic hypernuclei, as well as the hypermatter both at high and low temperatures. The abundant production of multi-strange nuclei that can give an access to multi-hyperon systems and strange nuclear matter. The de-excitation of hot hyper-cluster will allow for the hyperon correlation studies. There is a saturation of the hypernuclei production at high energies, therefore, the optimal way to pursue this experimental study is to use the accelerator facilities of intermediate energies.
nucl-thSpringer Proc.Phys.(2020)·0 citations
03
Evolution of fluctuations in the initial state of heavy-ion collisions from RHIC to LHC
Giuliano Giacalone🇫🇷 · François Gelis🇫🇷 · Pablo Guerrero-Rodríguez🇫🇮 · Matthew Luzum🇧🇷 · Cyrille Marquet🇫🇷 · Jean-Yves Ollitrault🇫🇷
Fluctuations in the initial state of heavy-ion collisions are larger at RHIC energy than at LHC energy. This fact can be inferred from recent measurements of the fluctuations of the particle multiplicities and of elliptic flow performed at the two different energies. We show that an analytical description of the initial energy-density field and its fluctuations motivated by the color glass condensate (CGC) effective theory predicts and quantitatively captures the measured energy evolution of these observables. The crucial feature is that fluctuations in the CGC scale like the inverse of the saturation scale of the nuclei.
nucl-thhep-exhep-phnucl-exSpringer Proc.Phys.(2020)·6 citations
04
Extraction of the neutron charge radius from a precision calculation of the deuteron structure radius
A.A. Filin · V. Baru · E. Epelbaum · H. Krebs · D. Möller · P. Reinert
We present a high-accuracy calculation of the deuteron structure radius in chiral effective field theory. Our analysis employs the state-of-the-art semilocal two-nucleon potentials and takes into account two-body contributions to the charge density operators up to fifth order in the chiral expansion. The strength of the fifth-order short-range two-body contribution to the charge density operator is adjusted to the experimental data on the deuteron charge form factor. A detailed error analysis is performed by propagating the statistical uncertainties of the low-energy constants entering the two-nucleon potentials and by estimating errors from the truncation of the chiral expansion as well as from uncertainties in the nucleon form factors. Using the predicted value for the deuteron structure radius together with the very accurate atomic data for the difference of the deuteron and proton charge radii we, for the first time, extract the charge radius of the neutron from light nuclei. The extracted value reads $r_{n}^{2} = - 0.106 + 0.007 - 0.005 fm^{2}$ and its magnitude is about $1.7 σ$ smaller than the current value given by the Particle Data Group. In addition, given the high accuracy of the calculated deuteron charge form factor and its careful and systematic error analysis, our results open the way for an accurate determination of the nucleon form factors from elastic electron-deuteron scattering data measured at the Mainz Microtron and other experimental facilities.
nucl-thnucl-exPRL(2020)·77 citations
05
Excited light baryons from quark-gluon-level calculations
J. Segovia🇪🇸 · C. Chen🇩🇪 · Z.-F. Cui🇨🇳 · Y. Lu🇨🇳 · C.D. Roberts🇨🇳
The task of mapping and explaining the spectrum of baryons and the structure of these states in terms of quarks and gluons is a longstanding challenge in hadron physics, which is likely to persist for another decade or more. We review the progress made in this topic using a functional method based on Dyson-Schwinger equations. This framework provides a non-perturbative, Poincaré-covariant continuum formulation of Quantum Chromodynamics which is able to extract novel insight on baryon properties since the physics at the hadron level is directly related with the underlying quark-gluon substructure, via convolution of Green functions.
nucl-thhep-lathep-ph1 citation
06
Family of Chiral Two- plus Three-Nucleon Interactions for Accurate Nuclear Structure Studies
Thomas Hüther🇩🇪 · Klaus Vobig🇩🇪 · Kai Hebeler🇩🇪 · Ruprecht Machleidt🇺🇸 · Robert Roth🇩🇪
We present a family of nucleon-nucleon (NN) plus three-nucleon (3N) interactions up to N3LO in the chiral expansion that provides an accurate ab initio description of ground-state energies and charge radii up to the medium-mass regime with quantified theory uncertainties. Starting from the NN interactions proposed by Entem, Machleidt and Nosyk, we construct 3N interactions with consistent chiral order, non-local regulator, and cutoff value and explore the dependence of nuclear observables over a range of mass numbers on the 3N low-energy constants. By fixing these constants using the 3-H and 16-O ground-state energies, we obtain interactions that robustly reproduce experimental energies and radii for large range from p-shell nuclei to the nickel isotopic chain and resolve many of the deficiencies of previous interactions. Based on the order-by-order convergence and the cutoff dependence of nuclear observables, we assess the uncertainties due the interaction, which yield a significant contribution to the total theory uncertainty.
nucl-thPLB(2020)·118 citations
07
Extracting many-body correlators of saturated gluons with precision from inclusive photon+dijet final states in deeply inelastic scattering
Kaushik Roy🇺🇸 · Raju Venugopalan🇺🇸
We highlight the principal results of a computation in the Color Glass Condensate effective field theory (CGC EFT) of the next-to-leading order (NLO) impact factor for inclusive photon+dijet production at Bjorken $x_{Bj} ≪ 1$ in deeply inelastic electron-nucleus (e+A DIS) collisions. When combined with extant results for next-to-leading log $x_{Bj}$ JIMWLK renormalization group (RG) evolution of gauge invariant two-point ("dipole") and four-point ("quadrupole") correlators of light-like Wilson lines, the inclusive photon+dijet e+A DIS cross-section can be determined to $\sim 10$ \% accuracy. Our computation simultaneously provides the ingredients to compute fully inclusive DIS, inclusive photon, inclusive dijet and inclusive photon+jet channels to the same accuracy. This makes feasible quantitative extraction of many-body correlators of saturated gluons and precise determination of the saturation scale $Q_{S, A} (x_{Bj})$ at a future Electron-Ion Collider. An interesting feature of our NLO result is the structure of the violation of the soft gluon theorem in the Regge limit. Another is the appearance in gluon emission of time-like non-global logs which also satisfy JIMWLK RG evolution.
↳ hep-phhep-thnucl-thPRD(2020)·33 citations
08
NLO impact factor for inclusive photon $+$ dijet production in $e + A$ DIS at small $x$
Kaushik Roy🇺🇸 · Raju Venugopalan🇺🇸
We compute the next-to-leading order (NLO) impact factor for inclusive photon $+$ dijet production in electron-nucleus (e+A) deeply inelastic scattering (DIS) at small $x$ . An important ingredient in our computation is the simple structure of ``shock wave" fermion and gluon propagators. This allows one to employ standard momentum space Feynman diagram techniques for higher order computations in the Regge limit of fixed $Q^{2} ≫ Λ_{QCD}^{2}$ and $x \to 0$ . Our computations in the Color Glass Condensate (CGC) effective field theory include the resummation of all-twist power corrections $Q_{s}^{2} / Q^{2}$ , where $Q_{s}$ is the saturation scale in the nucleus. We discuss the structure of ultraviolet, collinear and soft divergences in the CGC, and extract the leading logs in $x$ ; the structure of the corresponding rapidity divergences gives a nontrivial first principles derivation of the JIMWLK renormalization group evolution equation for multiparton lightlike Wilson line correlators. Explicit expressions are given for the $x$ -independent $O (α_{s})$ contributions that constitute the NLO impact factor. These results, combined with extant results on NLO JIMWLK evolution, provide the ingredients to compute the inclusive photon $+$ dijet cross-section at small $x$ to $O (α_{s}^{3} ln (x))$ . First results for the NLO impact factor in inclusive dijet production are recovered in the soft photon limit. A byproduct of our computation is the LO photon+ 3 jet (quark-antiquark-gluon) cross-section.
↳ hep-phhep-thnucl-thPRD(2020)·87 citations
09
Unruh effect universality: emergent conical geometry from density operator
Georgy Y. Prokhorov🇷🇺 · Oleg V. Teryaev🇷🇺 · Valentin I. Zakharov🇷🇺
The Unruh effect has been investigated from the point of view of the quantum statistical Zubarev density operator in space with the Minkowski metric. Quantum corrections of the fourth order in acceleration to the energy-momentum tensor of real and complex scalar fields, and Dirac field are calculated. Both massless and massive fields are considered. The method for regularization of discovered infrared divergences for scalar fields is proposed. The calculated corrections make it possible to substantiate the Unruh effect from the point of view of the statistical approach, and to explicitly show its universality for various quantum field theories of massless and massive fields. The obtained results exactly coincide with the ones obtained earlier by calculation of the vacuum average of energy-momentum tensor in a space with a conical singularity. Thus, the duality of two methods for describing an accelerated medium is substantiated. One may also speak about the emergence of geometry with conical singularity from thermodynamics. In particular, the polynomiality of the energy-momentum tensor and the absence of higher-order corrections in acceleration can be explicitly demonstrated.
↳ hep-thgr-qcnucl-thJHEP(2020)·36 citations
10
Calculation of acceleration effects using the Zubarev density operator
Georgy Y. Prokhorov🇷🇺 · Oleg V. Teryaev🇷🇺 · Valentin I. Zakharov🇷🇺
The relativistic form of the Zubarev density operator can be used to study quantum effects associated with acceleration of the medium. In particular, it was recently shown that the calculation of perturbative corrections in acceleration based on the Zubarev density operator makes it possible to show the existence of Unruh effect. In this paper, we present the details of the calculation of quantum correlators arising in the fourth order of the perturbation theory needed to demonstrate the Unruh effect. Expressions for the quantum corrections for massive fermions are also obtained.
↳ hep-thgr-qcnucl-thParticles(2020)·15 citations
11
Pion Beta Decay and CKM Unitarity
Andrzej Czarnecki🇨🇦 · William J. Marciano🇺🇸 · Alberto Sirlin🇺🇸
Pion beta decay, $π^{+} \to π^{0} e^{+} ν (γ)$ , provides a theoretically clean $\pm 0.3%$ determination of the CKM matrix element $V_{ud}$ . That value falls short of super-allowed nuclear beta decays where an order of magnitude better precision already exists. We advocate a new strategy for utilizing pion beta decay, based on its role in determining $V_{us} / V_{ud}$ via the ratio $R_{V} = Γ (K \to π l ν (γ)) /Γ (π^{+} \to π^{0} e^{+} ν (γ))$ . $R_{V}$ measures $f_{+}^{K} (0) ∣ V_{us} ∣/ f_{+}^{π} (0) ∣ V_{ud} ∣$ and is insensitive to the Fermi constant and some radiative corrections. Its dependence on the ratio of form factors may also prove useful for lattice gauge theory calculations. Employing a lattice based value $f_{+}^{K} (0) / f_{+}^{π} (0) = 0.970 (2)$ , we find $V_{us} / V_{ud} = 0.22918 (88)$ compared to $V_{us} / V_{ud} = 0.23131 (45)$ obtained from $R_{A} = Γ (K \to μν (γ)) /Γ (π \to μν (γ))$ . Those vector and axial-vector based $V_{us} / V_{ud}$ values exhibit a 2.2 $σ$ discrepancy. That tension may be relieved by a shift in the lattice $f_{+}^{K} (0) / f_{+}^{π} (0)$ towards the consistency range 0.961(4), changes in experimental input or new physics. Other implications of $R_{V}$ and $R_{A}$ are also discussed.
↳ hep-phhep-exhep-latnucl-thPRD(2020)·55 citations
12
Energy density at kinetic freeze-out in Pb-Pb collisions at the LHC using the Tsallis distribution
M. D. Azmi🇮🇳 · T. Bhattacharyya🇷🇺 · J. Cleymans🇿🇦 · M. Paradza🇿🇦
The thermodynamic parameters like energy density, pressure, entropy density, temperature and particle density are determined from the transverse momentum distributions of charged particles in Pb-Pb collisions at the LHC. The results show a clear increase with the centrality and the beam energy in all parameters. It is determined that in the final freeze-out stage the energy density reaches a value of about 0.039 GeV/fm $^{3}$ for the most central collisions at $s_{N N}$ = 5.02 TeV. This is less than that at chemical freeze-out where the energy density is about 0.36 GeV/fm $^{3}$ . This decrease approximately follows a $T^{4}$ law. The results for the pressure and entropy density are also presented for each centrality class at $s_{N N}$ = 2.76 and 5.02 TeV.
↳ hep-phnucl-thJ.Phys.G(2020)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE