Baryon-antibaryon Pair Production Research Articles

Total cross section of the process e++e−→Σ0+Σ¯0 in the vicinity of charmonium ψ(3770) including the D -meson loop and three-gluon contributions

For the study of the structure of baryons it is necessary to investigate the production of a baryon pair in e+e− annihilation. The baryon-antibaryon pair production at the electron-positron linear collider makes it possible to investigate in detail the basic structure of the Standard Model. The creation of baryon-antibaryon pairs in electron-positron annihilation provides an increasingly powerful tool at higher c.m. energies. We present phenomenological results for Σ0Σ¯0 production in e+e− interaction at the BESIII and Colliders. In the present work, we investigate a hyperon pair produced in the reaction e+e−→Σ0Σ¯0. We calculate the total cross section of the process e+e−→Σ0Σ¯0 taking into account the contributions of the D-meson loop and three gluon loops as well as the interference of all diagrams to the Born approximation. For these contributions large relative phases are generated with respect to the pure electromagnetic mechanism. For the large momentum transferred region we obtain as a byproduct a fit of the electromagnetic form factor of the Σ hyperon. Published by the American Physical Society 2024

Polarization and entanglement in baryon–antibaryon pair production in electron–positron annihilation

Using a sample of $1.31\times 10^9$ $J/\psi$ events collected with the BESIII detector, we report the first observation of spin polarization of $\Lambda$ and $\bar\Lambda$ hyperons from the coherent production in the $J/\psi\to\Lambda\bar\Lambda$ decay. We measure the phase between the hadronic form factors to be $\Delta\Phi=(42.4\pm0.6\pm0.5)^\circ$. The decay parameters for $\Lambda\to p\pi^-$ ($\alpha_-$), $\bar\Lambda\to\bar p\pi^+$ ($\alpha_+$) and $\bar\Lambda\to\bar n\pi^0$ ($\bar\alpha_0$) are measured to be $\alpha_-=0.750\pm0.009\pm0.004$, $\alpha_+=-0.758\pm0.010\pm0.007$ and $\bar\alpha_0=-0.692\pm0.016\pm0.006$, respectively. The obtained value of $\alpha_-$ is higher by $(17\pm 3)\%$ than the current world average. In addition, the $CP$ asymmetry of $-0.006\pm0.012\pm0.007$ is extracted with substantially improved precision. The ratio $\bar{\alpha}_0/\alpha_{+} = 0.913\pm 0.028 \pm 0.012$ is also measured.

Prospects of Ξ(1530)0Ξ̄(1530)0pair production at BESIII

The study of the baryon–antibaryon pair production from the charmonium states provides a favorable test and an input for the perturbative quantum chromodynamics calculation. Based on a Monte Carlo study via a single tag baryon strategy, a clear observation of [Formula: see text](3686)[Formula: see text](1530)[Formula: see text](1530)0is predicted at BESIII with the current 3.08[Formula: see text]106[Formula: see text](3686) dataset. The averaged precision of the [Formula: see text] parameters in the decay angular distribution formula is estimated as 0.25, and is not effective to separate the theoretical predictions. It will be an opportunity to distinguish them with 3.0[Formula: see text]109[Formula: see text](3686) events taken by BESIII detector in the next few years.

STRANGE HADRONS BRIDGE BETWEEN QUARKS AND STARS

Future experimental opportunities for the hypernuclear physics at GSI/FAIR are presented. The HYPHI experiment will investigate exotic hypernuclei which are produced by nuclear collision with stable heavy ion beams and rare isotope beams (RI-beams) at GSI. Thanks to the use of [Formula: see text] beams and the skilful combination of experimental techniques, copious production of double Λ hypernuclei is expected at the PANDA experiment which will enable high precision γ spectroscopy for the first time. Finally a novel method to explore the interaction of antibaryons in nuclei by baryon-antibaryon pair production in antiproton nucleus interactions is outlined.

Baryon-antibaryon pair production in two-photon collisions at LEP

Abstract Baryon pair production in two-photon collisions is studied with the L3 detector at LEP. The following reactions are identified: γγ → p p , γ → Λ Λ , γ → Σ 0 Σ 0 and γγ → Λ GS 0 + Σ 0 Λ . The analyses are based on data collected at e+e− center-of-mass energies from 91 GeV to 208 GeV, corresponding to an integrated luminosity of 844 pb−1. Their cross section is measured as a function of the the two-photon center-of-mass energy and the production polar angle. The results are compared to the predictions of the quark-diquark and handbag models.

Charmless exclusive baryonicBdecays

We present a systematical study of two-body and three-body charmless baryonic B decays. The branching ratios for two-body modes are in general very small, typically less than ${10}^{\ensuremath{-}6},$ except that $\mathcal{B}{(B}^{\ensuremath{-}}\ensuremath{\rightarrow}p{\overline{\ensuremath{\Delta}}}^{\ensuremath{-}\ensuremath{-}})\ensuremath{\sim}1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}.$ In general, $\overline{B}\ensuremath{\rightarrow}N\overline{\ensuremath{\Delta}}>\overline{B}\ensuremath{\rightarrow}N\overline{N}$ due to the large coupling constant for ${\ensuremath{\Sigma}}_{b}\ensuremath{\rightarrow}B\ensuremath{\Delta}.$ For three-body modes we focus on octet baryon final states. The leading three-dominated modes are ${B}^{0}\ensuremath{\rightarrow}p\mathrm{n\ifmmode \bar{}\else \={}\fi{}}{\ensuremath{\pi}}^{\ensuremath{-}}({\ensuremath{\rho}}^{\ensuremath{-}}),$ $n\overline{p}{\ensuremath{\pi}}^{+}({\ensuremath{\rho}}^{+})$ with a branching ratio of order $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ for ${B}^{0}\ensuremath{\rightarrow}p\mathrm{n\ifmmode \bar{}\else \={}\fi{}}{\ensuremath{\pi}}^{\ensuremath{-}}$ and $8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ for ${B}^{0}\ensuremath{\rightarrow}p\mathrm{n\ifmmode \bar{}\else \={}\fi{}}{\ensuremath{\rho}}^{\ensuremath{-}}.$ The penguin-dominated decays with strangeness in the meson, e.g., ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}p\overline{p}{K}^{\ensuremath{-}(*)}$ and ${B}^{0}\ensuremath{\rightarrow}p\mathrm{n\ifmmode \bar{}\else \={}\fi{}}{K}^{\ensuremath{-}(*)},$ $n\mathrm{n\ifmmode \bar{}\else \={}\fi{}}{K}^{0(*)},$ have appreciable rates and the $N\overline{N}$ mass spectrum peaks at low mass. The penguin-dominated modes containing a strange baryon, e.g., ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{0}\overline{p}{\ensuremath{\pi}}^{+},$ ${\ensuremath{\Sigma}}^{\ensuremath{-}}\mathrm{n\ifmmode \bar{}\else \={}\fi{}}{\ensuremath{\pi}}^{+},$ have branching ratios of the order of $(1--4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}.$ In contrast, the decay rate of ${B}^{0}\ensuremath{\rightarrow}\ensuremath{\Lambda}\overline{p}{\ensuremath{\pi}}^{+}$ is smaller. We explain why some of the charmless three-body final states in which baryon-antibaryon pair production is accompanied by a meson have a larger rate than their two-body counterparts: either the pole diagrams for the former have an antitriplet bottom baryon intermediate state, which has a large coupling to the B meson and the nucleon, or they are dominated by the factorizable external W-emission process.

Study of inclusive baryon-antibaryon pair production of $p$ or $\Lambda$ in two-photon processes

Study of inclusive baryon-antibaryon pair production of $p$ or $\Lambda$ in two-photon processes

Applications of the superflavor symmetry to heavy baryon-antibaryon pair production in electron-positron collision.

The baryons containing two heavy quarks and a light quark are believed to have the diquark-quark structure and the diquark is composed of the two heavy quarks which is a spin-0 or spin-1 object. The superflavor symmetry can associate productions of such heavy baryon-antibaryon pair with the heavy meson productions. The whole scenario is presented in some details in this work, and the observation prospect in future experiments is discussed.

Study of inclusive baryon-antibaryon pair production ofp orΛ in two-photon processes

Inclusive baryon-antibaryon pair production was studied in two-photon events which were collected at thee + e − collider TRISTAN, and correspond to an integrated luminosity of 303 pb−1. Correlations between a baryon and an antibaryon were studied for their flavors (p orΛ) and their momentum vectors. The experimental results were compared with the expectations from a jet-fragmentation Monte Carlo simulation. We have found that although the ratios of the cross sections of different baryon-flavor combinations are consistent with the Monte Carlo expectations, the cross section shows an excess over the Monte Carlo expectation in a low invariant-mass region of final-state particles at large angles, that indicates a significant contribution from higher-order QCD or non-perturbative effects. The experimental data show no narrow azimuthal-angle correlation, which is expected from a jet-fragmentation Monte Carlo. A search for exclusiveΛ pair production has also been made. We have no candidates and have obtained the upper limit for the cross section.

New features of unusual shadowing in hadron-nucleus collisions

The appearance of an unusual shadowing in nuclei in a certain kind of processes is applied to nondiffractive interactions on nuclei and to the baryon-antibaryon pair production off nuclei. Also the competition between\(B\bar B\) pair production and annihilation is studied. The unusual shadowing is shown to be present also in certain hadron-hadron processes. Several experimental consequences appear which can check our results.

The role of valence quarks in proton fragmentation

Following earlier theoretical and experimental work (Kalinowski et al. [6], Bourquin et al. [7]), baryon production by fragmentation of incident protons in high energy hadron collisions is re-investigated in terms of a fragmentation-recombination mechanism similar to a model proposed by Fukuda and Iso [4]. The multiplicitiesnf(B) for the various types of baryonsB produced in proton fragmentation are expressed in terms of the probabilitiesai fori=0, ..., 3 valence quarks of the incident proton to emerge in the baryonB and 3−i to emerge in mesons (following [7] we suppose that antibaryon production is mostly due to baryon-antibaryon pair production by a mechanism of non-fragmentation type, and this is taken into account in deducingnf(B) from baryon and antibaryon multiplicity data). The positivity of theai is found to impose remarkably narrow constraints on thenf(B) for (meta)stableB, and we find the data to satisfy these constraints. We show furthermore that the data are compatible with uncorrelated behaviour of the valence quarks of the incident proton, each of them having a probability ≃ 0.6 to emerge in the fragmentation baryonB, and a probability ≃ 0.4 to emerge in a meson. We also briefly discuss the relation of our analysis to previous work on the recombination model of proton fragmentation and its possible extension to meson fragmentation.

Discontinuous behaviour in large angle proton-proton elastic scattering at high energies

Measurements of elastic proton-proton differential cross sections for angles between 65° and 90° c.m.s. have been made at 8, 9, 10, 11, 14, 15 and 21 GeV/ c. The shape of the angular distribution is found to change suddenly between 8 and 11 GeV/ c. An interpretation of this discontinuous behaviour in terms of the reactive effects of baryon-antibaryon pair production is proposed.