Strangeness Charge Research Articles

Nucleon strange electromagnetic form factors

The role of the strange quarks on the low-energy interactions of the proton can be probed through the strange electromagnetic form factors. Knowledge of these form factors provides essential input for parity-violating processes and contributes to the understanding of the sea quark dynamics. We determine the strange electromagnetic form factors of the nucleon within the lattice formulation of Quantum Chromodynamics using simulations that include light, strange and charm quarks in the sea all tuned to their physical mass values. We employ state-of-the-art techniques to accurately extract the form factors for values of the momentum transfer square up to 0.8~GeV$^2$. We find that both the electric and magnetic form factors are statistically non-zero. We obtain for the strange magnetic moment $\mu^s=-0.017(4)$, the strange magnetic radius $\langle r^2_M \rangle^s=-0.015(9)$~fm$^2$, and the strange charge radius $\langle r^2_E \rangle^s=-0.0048(6)$~fm$^2$.

Effect of inverse magnetic catalysis on conserved-charge fluctuations in a hadron resonance gas model

The effect of inverse magnetic catalysis (IMC) has been observed on the conserved charge fluctuations and the correlations along the chemical freeze-out curve in a hadron resonance gas model. The fluctuations and the correlations have been compared with and without charge conservations. The charge conservation plays an important role in the calculation of the fluctuations at nonzero magnetic field and for the fluctuations in the strange charge at zero magnetic field. The charge conservation diminishes the correlations $\chi_{BS}$ and $\chi_{QB}$, but enhances the correlation $\chi_{QS}$. The baryonic fluctuations (2nd order) at $B = 0.25$ ${GeV}^2$ increases more than two times compared to $B = 0$ at higher $\mu_{B}$. The fluctuations have been compared at nonzero magnetic field along the freeze-out curve i.e along fitted parameters of the chemical freeze-out temperature and chemical potentials, with the fluctuations at nonzero magnetic field along the freeze-out curve with the IMC effect, and the results are very different with the IMC effect. This is clearly seen in the products of different moments ${{\sigma}^2}/{M}$ and $S\sigma$ of net-kaon distribution.

Strange Quark Magnetic Moment of the Nucleon at the Physical Point.

We report a lattice QCD calculation of the strange quark contribution to the nucleon's magnetic moment and charge radius. This analysis presents the first direct determination of strange electromagnetic form factors including at the physical pion mass. We perform a model-independent extraction of the strange magnetic moment and the strange charge radius from the electromagnetic form factors in the momentum transfer range of 0.051 GeV^{2}≲Q^{2}≲1.31 GeV^{2}. The finite lattice spacing and finite volume corrections are included in a global fit with 24 valence quark masses on four lattices with different lattice spacings, different volumes, and four sea quark masses including one at the physical pion mass. We obtain the strange magnetic moment G_{M}^{s}(0)=-0.064(14)(09)μ_{N}. The four-sigma precision in statistics is achieved partly due to low-mode averaging of the quark loop and low-mode substitution to improve the statistics of the nucleon propagator. We also obtain the strange charge radius ⟨r_{s}^{2}⟩_{E}=-0.0043(16)(14) fm^{2}.

Statistical Model of the Early Stage of Nucleus--Nucleus Collisions with Exact Strangeness Conservation

The Statistical Model of the Early Stage, SMES, describes a transition between confined and deconfined phases of strongly interacting matter created in nucleus-nucleus collisions. The model was formulated in the late 1990s for central Pb+Pb collisions at the CERN SPS energies. It predicted several signals of the transition (onset of deconfinement) which were later observed by the NA49 experiment. The grand canonical ensemble was used to calculate entropy and strangeness production. This approximation is valid for reactions with mean multiplicities of particles carrying conserved charges being significantly larger than one. Recent results of NA61/SHINE on hadron production in inelastic p+p interactions suggest that the deconfinement may also take place in these reactions. However, in this case mean multiplicity of particles with non-zero strange charge is smaller than one. Thus for the modeling of p+p interactions the exact strangeness conservation has to be implemented in the SMES. This extension of the SMES is presented in the paper.

Strangeness-driven phase transition in (proto-)neutron star matter

The phase diagram of a system constituted of neutrons, protons, $\ensuremath{\Lambda}$ hyperons, and electrons is evaluated in the mean-field approximation in the complete three-dimensional space given by the baryon, lepton, and strange charge. It is shown that the phase diagram at subsaturation densities is strongly affected by the electromagnetic interaction, while it is almost independent of the electric charge at suprasaturation density. As a consequence, stellar matter under the condition of strangeness equilibrium is expected to experience a first as well as a second-order strangeness-driven phase transition at high density, while the liquid-gas phase transition is expected to be quenched. An RPA calculation indicates that the presence of this critical point might have sizable implications for the neutrino propagation in core-collapse supernovae.

Four-nucleon shell-model calculations in a Faddeev-like approach

We use equations for Faddeev amplitudes to solve the shell-model problem for four nucleons in the model space that includes up to 14 hbar Omega harmonic-oscillator excitations above the unperturbed ground state. Two- and three-body effective interactions derived from the Reid93 and Argonne V8' nucleon-nucleon potentials are used in the calculations. Binding energies, excitations energies, point-nucleon radii and electromagnetic and strangeness charge form factors for 4He are studied. The structure of the Faddeev-like equations is discussed and a formula for matrix elements of the permutation operators in a harmonic-oscillator basis is given. The dependence on harmonic-oscillator excitations allowed in the model space and on the harmonic-oscillator frequency is investigated. It is demonstrated that the use of the three-body effective interactions improves the convergence of the results.

Many-body currents and the strange-quark content of 4He.

Meson-exchange current (MEC) contributions to the parity-violating (PV) asymmetry for elastic scattering of polarized electrons from $^4$He are calculated over a range of momentum transfer using Monte Carlo methods and a variational $^4$He ground state wavefunction. The results indicate that MEC's generate a negligible contribution to the asymmetry at low-$|\qv|$, where a determination of the nucleon's mean square strangeness radius could be carried out at CEBAF. At larger values of momentum transfer -- beyond the first diffraction minimum -- two-body corrections from the $\rho$-$\pi$ \lq\lq strangeness charge" operator enter the asymmetry at a potentially observable level, even in the limit of vanishing strange-quark matrix elements of the nucleon. For purposes of constraining the nucleon's strangeness electric form factor, theoretical uncertainties associated with these MEC contributions do not appear to impose serious limitations.

The Shadow of de Man

The name carries a strange charge on the current scene of theory. While de Man stands as a representative figure of the turn to theory from the late 1960s on and his work decisively marked the ensuing critical conversation, his name now spurs a range of complicated reactions, from guarded veneration to knee-jerk condemnation. In the aftermath of the discovery of his wartime writings, his name invokes a scandal, a scandal that incurs a series of echoing effects: his demonization, by extension the condemnation of deconstruction and the castigation of theory, the defensive responses of his supporters, and the elision of his name from the official story of deconstruction, as well as the continuation of his work under other names.1 My point here is not to adjudicate the case of de Man, certainly not to condemn or defend him in light of his wartime writings, but to sketch out these effects and what they tell of the current critical scene, of the economy of criticism and theory and the institutional circuit of that economy. For it seems to me, more than any other figure, has become a synechdochal figure for theory and its stakes these past fifteen years, and the charges that his name takes are a cipher of the critical scene. More precisely, the complicated and equivocal effects ensuing from play out the present ambivalent state of theory. In 1980, the case was much different. In some ways, de Man loomed magisterially over the critical scene. To give one instance of his extraordinary sway, as Don Bialostosky points out in the context of Wordsworth criticism, de Man not only marked the scene but set the terms or problematics of Wordsworth criticism on the basis of a few articles-merely sixtyfive or so pages, by Bialostosky's count--displacing other prominent Romanticists, most notably Geoffrey Hartman and M. H. Abrams.2 And de Man was very visible not only in the influence of his texts, but in his tutelary form, via prominent students (such as Barbara Johnson, Cynthia Chase, Andrzej Warminski, Carol Jacobs, Deborah Esch, Peggy Kamuf, and to a lesser or more mediated degree, Neil Hertz, Jonathan Culler, Werner Hamacher, Samuel Weber, and perhaps even Hillis Miller). Further, one can measure his reach inversely by the extent of antagonism he drew. While it would require amassive examination of the institution of literature through that moment to explain the profusion of theory and de Man's role in it, suffice it to say that came to stand in as a figural locus for theory itself, more locally for deconstruction but more generally for the various

Nuclear tests for the strange charge from factor of the nucleon

It is shown that the measurements of elastic and inelastic scattering of neutrinos and parity-violating asymmetry of longitudinally polarized electrons on spin-isospin zero nuclei would yield model independent information about the strangeness charge form factor. Nunerical estimates of the contribution of this form factor are presented for 4He, 12C and 16O nuclei in impulse approximation using strangeness vector from factors of the nucleon recently suggested in the literature. A general relation between the P-odd asymmetry in electron scattering and the cross sections of neutrino and unpolarized electron scattering on spin zero nuclei is obtained.

Temporality and the Necessity for Dialectic: The Missing Dimension of Contemporary Theory

is the painful fact that modern culture no longer experiences temporality in accord with Enlightenment models of progress. For us the social force of time is not a source of hope but a specter promising the degeneration of all that we can still value. The challenge then is to show why we need a temporal dimension to our interpretive thinking. What does this dimension add to our powers as agents, and how might its reflective presence actually affect the social order now terrified of its consequences? I cannot live up to the melodramatic voice of this introduction or answer these questions directly. But I think I can tease out the beginnings of an answer by focusing on the consequences following from the ways in which the dominant perspectives in contemporary critical theory suppress time. At first you will hear this as a strange charge. Usually modernism is seen as a movement desperate to escape the historical forces transforming the remnants of aristocratic culture into a dominant bourgeois order. We contemporaries then become the rescuers of history, with our commitments to antifoundationalism and our resistance to the totalizing claims proposed by dialecticians like Hegel. Our theorizing is committed not to myth and to form but to the contingencies of locally constituted structures of belief and hence to ethical and political ideals devoted to valuing heterogeneity over any ordering schema. Yet this very insistence on heterogeneity has produced governing metaphors for our theorizing that privilege space over time, and that thus provide severely limited frameworks for dealing with the entire domain of contingencies, dependencies, and changes which are central to historicist consciousness. Critics like Carolyn Porter, Dominick La Capra, and Vincent Pecora have already noted the price New Historicism has