Nuclear Theory·nucl-th

Thursday·August 16, 2018

10 papers—2 primary·8 cross-listed

01
$0 ν β β$ nuclear matrix elements, neutrino potentials and $SU (4)$ symmetry
Fedor Šimkovic · Adam Smetana · Petr Vogel
Intimate relation between the Gamow-Teller part of the matrix element $M_{GT}^{0 ν}$ and the $2 ν β β$ closure matrix element $M_{cl}^{2 ν}$ is explained and explored. If the corresponding radial dependence $C_{cl}^{2 ν} (r)$ would be known, $M^{0 ν}$ corresponding to any mechanism responsible for the $0 ν β β$ decay can be obtained as a simple integral. However, the $M_{cl}^{2 ν}$ values sensitively depend on the properties of higher lying $1^{+}$ states in the intermediate odd-odd nuclei. We show that the $β^{-}$ and $β^{+}$ amplitudes of such states typically have opposite relative signs, and their contributions reduce severally the $M_{cl}^{2 ν}$ values. Vanishing values of $M_{cl}^{2 ν}$ are signs of a partial restoration of the spin-isospin $SU (4)$ symmetry. We suggest that demanding that $M_{cl}^{2 ν}$ = 0 is a sensible way, within the method of the Quasi-particle Random Phase Approximation (QRPA), of determining the amount of renormalization of isoscalar particle-particle interaction strength $g_{pp}^{T = 0}$ . Using such prescription, the matrix elements $M^{0 ν}$ are evaluated; their values are not very different ( $\leq$ 20\%) from the usual QRPA values when $g_{pp}^{T = 0}$ is related to the known $2 ν β β$ half-lives.
nucl-thPRC(2018)·90 citations
02
Post breakup dynamics of fragments produced in nuclear multifragmentation
S. R. Souza🇧🇷 · B. V. Carlson🇧🇷 · R. Donangelo🇧🇷
The deexcitation of the primary hot fragments, produced in the breakup of an excited nuclear source, during their propagation under the influence of their mutual Coulomb repulsion is studied in the framework of a recently developed hybrid model. The latter is based on the Statistical Mul- tifragmentation Model (SMM), describing the prompt breakup of the source, whereas the particle emission from the hot fragments, that decay while traveling away from each other, is treated by the Weisskopf-Ewing evaporation model. Since this treatment provides an event by event descrip- tion of the process, in which the classical trajectories of the fragments are followed using molecular dynamics techniques, it allows one to study observables such as two-particle correlations and infer the extent to which the corresponding observables may provide information on the multifragment production mechanisms. Our results suggest that the framework on which these treatments are based may be considerably constrained by such analyses. Furthermore, they imply that information obtained from these model calculations may provide feedback to the theory of nuclear interferome- try. We also found that neutron deficient fragments should hold information more closely related to the breakup region than neutron rich ones, as they are produced in much earlier stages of the post breakup dynamics than the latter.
nucl-thnucl-exNPA(2019)·5 citations
03
Dispersion relation for hadronic light-by-light scattering: pion pole
Martin Hoferichter🇺🇸 · Bai-Long Hoid🇩🇪 · Bastian Kubis🇩🇪 · Stefan Leupold🇸🇪 · Sebastian P. Schneider🇩🇪
The pion-pole contribution to hadronic light-by-light scattering in the anomalous magnetic moment of the muon $(g - 2)_{μ}$ is fully determined by the doubly-virtual pion transition form factor. Although this crucial input quantity is, in principle, directly accessible in experiment, a complete measurement covering all kinematic regions relevant for $(g - 2)_{μ}$ is not realistic in the foreseeable future. Here, we report in detail on a reconstruction from available data, both space- and time-like, using a dispersive representation that accounts for all the low-lying singularities, reproduces the correct high- and low-energy limits, and proves convenient for the evaluation of the $(g - 2)_{μ}$ loop integral. We concentrate on the systematics of the fit to $e^{+} e^{-} \to 3 π$ data, which are key in constraining the isoscalar dependence, as well as the matching to the asymptotic limits. In particular, we provide a detailed account of the pion transition form factor at low energies in the time- and space-like region, including the error estimates underlying our final result for the pion-pole contribution, $a_{μ}^{π^{0} -pole} = 62. 6_{- 2.5}^{+ 3.0} \times 1 0^{- 11}$ , and demonstrate how forthcoming singly-virtual measurements will further reduce its uncertainty.
↳ hep-phhep-exhep-latnucl-thJHEP(2018)·537 citations
04
Anyonic particle-vortex statistics and the nature of dense quark matter
Aleksey Cherman🇺🇸 · Srimoyee Sen🇺🇸 · Laurence G. Yaffe🇺🇸
We show that $Z_{3}$ -valued particle-vortex braiding phases are present in high density quark matter. Certain mesonic and baryonic excitations, in the presence of a superfluid vortex, have orbital angular momentum quantized in units of $ℏ/3$ . Such non-local topological features can distinguish phases whose realizations of global symmetries, as probed by local order parameters, are identical. If $Z_{3}$ braiding phases and angular momentum fractionalization are absent in lower density hadronic matter, as is widely expected, then the quark matter and hadronic matter regimes of dense QCD must be separated by at least one phase transition.
↳ hep-thhep-phnucl-thPRD(2019)·63 citations
05
Multiparticle Production at Mid-Rapidity in the Color-Glass Condensate
Mauricio Martinez🇺🇸 · Matthew D. Sievert🇺🇸 · Douglas E. Wertepny🇪🇸
In this paper, we compute a number of cross sections for the production of multiple particles at mid-rapidity in the semi-dilute / dense regime of the color-glass condensate (CGC) effective field theory. In particular, we present new results for the production of two quark-antiquark pairs (whether the same or different flavors) and for the production of one quark-antiquark pair and a gluon. We also demonstrate the existence of a simple mapping which transforms the cross section to produce a quark-antiquark pair into the corresponding cross section to produce a gluon, which we use to obtain various results and to cross-check them against the literature. We also discuss hadronization effects in the heavy flavor sector, writing explicit expressions for the production of various combinations of $D$ and $D ˉ$ mesons, $J / ψ$ mesons, and light hadrons. The various multiparticle cross sections presented here contain a wealth of information and can be used to study heavy flavor production, charge-dependent correlations, and "collective" flow phenomena arising from initial-state dynamics.
↳ hep-phnucl-thJHEP(2019)·18 citations
06
Coupled-channel effects in hadron-hadron correlation functions
J. Haidenbauer🇩🇪
Two-particle momentum correlation functions as measured in heavy ion collisions or in high-energetic proton-proton collisions are studied. Special emphasis is put on systems like $ΛΛ$ or $K^{-} p$ where effects from the coupling to other channels could be relevant. In both cases other channels open at relatively low momenta or are already open at the reaction threshold. To have a solid basis, realistic coupled-channel interactions for $ΛΛ - Ξ N - ΛΣ - ΣΣ$ and $π Λ - π Σ - K ˉ N$ are utilized in the actual calculations. It is found that the opening of the $Ξ N$ channel leaves a trace in the $ΛΛ$ correlation function that could be detectable in experiments. Should the proposed $H$ -dibaryon be located close to or below the $Ξ N$ it will have a very pronounced effect. The presence of open channels in systems like $Ξ^{-} p$ or $K^{-} p$ does influence the correlation functions significantly at low momenta and will certainly complicate any dedicated analysis.
↳ hep-phnucl-thNPA(2019)·92 citations
07
Test of semi-local duality in a large $N_{C}$ framework
Ling-Yun Dai🇨🇳 · Xian-Wei Kang🇨🇳 · Ulf-G. Meißner🇩🇪
In this paper we test the semi-local duality based on the method of Ref.[1] for calculating final-state interactions at varying number of colors ( $N_{C}$ ). We compute the amplitudes by dispersion relations that respect analyticity and coupled channel unitarity, as well as accurately describing experiment. The $N_{C}$ dependence of the $π π \to π π$ scattering amplitudes is obtained by comparing these amplitudes to the one of chiral perturbation theory. The semi-local duality is investigated by varying $N_{C}$ . Our results show that the semi-local duality is not violated when $N_{C}$ is large. At large $N_{C}$ , the contributions of the $f_{2} (1270)$ , the $f_{0} (980)$ and the $f_{0} (1370)$ cancel that of the $ρ (770)$ in the finite energy sum rules, while the $f_{0} (500)$ has almost no effect. This gives further credit to the method developed in Ref.[1] for investigating the $N_{C}$ dependence of hadron-hadron scattering with final-state interactions. This study is also helpful to understand the structure of the scalar mesons.
↳ hep-phnucl-thPRD(2018)·10 citations
08
Quantifying jet modifications with substructure
Konrad Tywoniuk🇨🇭 · Yacine Mehtar-Tani🇺🇸
The striking suppression and modification patterns that are observed in jet observables measured in heavy-ion collisions with respect to the proton-proton baseline have the potential to constrain the spatio-temporal branching process of energetic partons in a dense QCD medium. The mechanism of jet energy loss is intricately associated with medium resolution of jet substructure fluctuations. This naturally affects the behavior of the suppression of jets at high-pT, inducing an explicit dependence on jet scales. In this contribution, we review recent work on using the insight from multi-parton quenching to calculate leading-logarithmic corrections to the single-inclusive jet spectrum, and discuss its impact on a wide range of observables, including jet substructure.
↳ hep-phnucl-th0 citations
09
Hypothesis about semi-weak interaction and experiments with solar neutrinos. II. Deuteron disintegration by neutral currents
L.M. Slad🇷🇺
The present work provides one more evidence of that the solar neutrino problem has an elegant solution based on the hypothesis about the existence of a new, semi-weak, interaction. The analysis of the deuteron disintegration by neutral currents of solar neutrinos, generated by both the electroweak and semi-weak interactions, is fulfilled. A good agreement between the theoretical and experimental results for this process is obtained, which is in harmony with the conclusions of the first part of the work on the other four observed processes with solar neutrinos.
↳ hep-phastro-ph.SRhep-exnucl-th2 citations
10
Electromagnetic spectral function and dilepton rate in a hot magnetized QCD medium
Snigdha Ghosh🇮🇳 · Vinod Chandra🇮🇳
The dilepton production rate in hot QCD medium is studied within a effective description of the medium in the presence of magnetic field. This could be done by obtaining the one-loop self energy of photon due to the effective (quasi-) quark loop at finite temperature under an arbitrary external magnetic field while employing the real time formalism of Thermal Field Theory. The effective quarks and gluons encode hot QCD medium effective in terms of their respective effective fugacities. The magnetic field enters in the form of landau level quantization, in the matter sector (quarks, antiquarks). The full Schwinger proper time propagator including all the Landau levels is considered for the quasi quarks while calculating the photon self energy. The electromagnetic Debye screening (in terms of the self-energy) has seen to be influenced both by the hot QCD medium effects and magnetic field. Analogous results are also obtained from the semi classical transport theory. The imaginary part of the photon self energy function is obtained from the discontinuities of the self energy across the Unitary cuts which are also present at zero magnetic field and the Landau cuts which are purely due to the magnetic field. The dilepton production rate is then obtained in terms of the product of electromagnetic spectral functions due to quark loop and lepton loop. The modifications of both the quarks/antiquarks as well as leptons in presence of an arbitrary external magnetic field have been considered in the formalism. Significant enhancement of the low invariant mass dileptons due the appearance of the Landau cuts in the electromagnetic spectral function at finite external magnetic field has been observed. A substantial enhancement of dilepton rate is also found when the EOS effects are considered through the effective quarks/antiquraks.
↳ hep-phnucl-thPRD(2018)·54 citations

Affiliations

first authorsco-authorsvia INSPIRE