The recent observation of a hadronic resonance d⁎ in the proton–neutron system with isospin I=0 and spin-parity JP=3+ raises the possibility of producing other novel six-quark dibaryon configurations ...allowed by QCD. A dramatic example of an exotic six-quark color-singlet system is the charge Q=+4, isospin I=3, Iz=+3|uuuuuu〉 state which couples strongly to Δ+++Δ++. The width and decay properties of such six-quark resonances could be regarded as manifestations of “hidden-color” six-quark configurations, a first-principle prediction of QCD – SU(3)-color gauge theory for the deuteron distribution amplitude. Other implications and possible future experiments are discussed.
Despite many decades of study the physical origin of 'dark matter' (DM) in the Universe remains elusive. In this letter we calculate the properties of a completely new DM candidate-Bose-Einstein ...condensates formed from a recently discovered bosonic particle in the light-quark sector, the d * ( 2380 ) hexaquark. In this first study, we show stable d ∗ ( 2380 ) Bose-Einstein condensates could form in the primordial early universe, with a production rate sufficiently large that they are a plausible new candidate for DM. Some possible astronomical signatures of such DM are also presented.
Elucidating the role of strange baryons (hyperons) in neutron stars requires detailed knowledge of hyperon–nucleon interactions in the light (u,d,s) quark sector. The structure of the hyperons and ...their excitation spectra also directly impact, and are an input to, models of big-bang nucleosynthesis. The upcoming K-long Facility will provide a much-needed intense and clean neutral strange meson beam, from which hyperons can be produced at rates where hyperon structure, hyperon–nucleon interactions and higher-order interactions can be studied with a new level of accuracy and for hitherto unreachable measurements. The new facility has the potential to address long-standing questions surrounding the strange sector of the strong force and its relevance to the structure of atomic nuclei, neutron stars and the cosmos at large. This article is part of the theme issue ‘The liminal position of Nuclear Physics: from hadrons to neutron stars’.
Positron Emission Tomography (PET) is a widely-used imaging modality for medical research and clinical diagnosis. Imaging of the radiotracer is obtained from the detected hit positions of the two ...positron annihilation photons in a detector array. The image is degraded by backgrounds from random coincidences and in-patient scatter events which require correction. In addition to the geometric information, the two annihilation photons are predicted to be produced in a quantum-entangled state, resulting in enhanced correlations between their subsequent interaction processes. To explore this, the predicted entanglement in linear polarisation for the two photons was incorporated into a simulation and tested by comparison with experimental data from a cadmium zinc telluride (CZT) PET demonstrator apparatus. Adapted apparati also enabled correlation measurements where one of the photons had undergone a prior scatter process. We show that the entangled simulation describes the measured correlations and, through simulation of a larger preclinical PET scanner, illustrate a simple method to quantify and remove the unwanted backgrounds in PET using the quantum entanglement information alone.
Elucidating the appropriate microscopic degrees of freedom within neutron stars remains an open question which impacts nuclear physics, particle physics and astrophysics. The recent discovery of the ...first non-trivial dibaryon, the d⁎(2380), provides a new candidate for an exotic degree of freedom in the nuclear equation of state at high matter densities. In this paper a first calculation of the role of the d⁎(2380) in neutron stars is performed based on a relativistic mean field description of the nucleonic degrees of freedom supplemented by a free boson gas of d⁎(2380). The calculations indicate that the d⁎(2380) would appear at densities around three times normal nuclear matter saturation density and comprise around 20% of the matter in the centre of heavy stars with higher fractions possible in the higher densities of merger processes. The d⁎(2380) would also reduce the maximum star mass by around 15% and have significant influence on the fractional proton/neutron composition. New possibilities for neutron star cooling mechanisms arising from the d⁎(2380) are also predicted.
Dibaryons and where to find them Bashkanov, M; Watts, D P; Clash, G ...
Journal of physics. G, Nuclear and particle physics,
04/2024, Letnik:
51, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Abstract In recent years, there has been tremendous progress in the investigation of bound systems of quarks with multiplicities beyond the more usual two- and three-quark systems. Experimental and ...theoretical progress has been made in the four-, five- and even six-quark sectors. In this paper, we review the possible lightest six-quark states using a simple ansatz based on SU(3) symmetry and evaluate the most promising decay branches. The work will be useful to help focus future experimental searches in this six-quark sector.
We present the extension of a previous study where, assuming a simple free bosonic gas supplemented with a relativistic mean-field model to describe the pure nucleonic part of the equation of state, ...we studied the consequences that the first non-trivial hexaquark
d
*
(2380) could have on the properties of neutron stars. Compared to that exploratory work, we employ a standard non-linear Walecka model including additional terms that describe the interaction of the
d
*
(2380) di-baryon with the other particles of the system through the exchange of
σ
- and
ω
-meson fields. Our results show that the presence of the
d
*
(2380) leads to maximum masses compatible with recent observations of ∼2
M
⊙
millisecond pulsars if the interaction of the
d
*
(2380) is slightly repulsive or the
d
*
(2380) does not interact at all. An attractive interaction makes the equation of state too soft to be able to support a 2
M
⊙
neutron star whereas an extremely repulsive one induces the collapse of the neutron star into a black hole as soon as the
d
*
(2380) appears.
A precise measurement of the differential cross sections dσ/dΩ and the linearly polarized photon beam asymmetry Σ_{3} for Compton scattering on the proton below pion threshold has been performed with ...a tagged photon beam and almost 4π detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS setup. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-t dispersion relation model, constraining the fits with the Baldin sum rule, we have obtained the proton electric and magnetic polarizabilities with unprecedented precision: α_{E1}=10.99±0.16±0.47±0.17±0.34, β_{M1}=3.14±0.21±0.24±0.20±0.35; in units of 10^{-4} fm^{3} where the errors are statistical, systematic, spin polarizability dependent, and model dependent.
We report a measurement of the spin polarization of the recoiling neutron in deuterium photodisintegration, utilizing a new large acceptance polarimeter within the Crystal Ball at MAMI. The measured ...photon energy range of 300-700 MeV provides the first measurement of recoil neutron polarization at photon energies where the quark substructure of the deuteron plays a role, thereby providing important new constraints on photodisintegration mechanisms. A very high neutron polarization in a narrow structure centered around E_{γ}∼570 MeV is observed, which is inconsistent with current theoretical predictions employing nucleon resonance degrees of freedom. A Legendre polynomial decomposition suggests this behavior could be related to the excitation of the d^{*}(2380) hexaquark.
Using a high-quality beam of storage rings in combination with a pellet target and a hermetic WASA detector covering practically the full solid angle, two-pion production in nucleon-nucleon ...collisions has been systematically studied by exclusive and kinematically complete measurements-first at CELSIUS and subsequently at COSY. These measurements resulted in a detailed understanding of the two-pion production mechanism by t-channel meson exchange. The investigation of the ABC effect, which denotes an unusual low-mass enhancement in the -invariant mass spectrum, in double-pionic fusion reactions led the trace to the observation of a narrow dibaryon resonance with about 80 MeV below the nominal mass of the conventional system. New neutron-proton scattering data, taken with a polarized beam at COSY, produced a pole in the coupled partial waves at ( ) MeV, establishing thus the first observation of a genuine s-channel dibaryon resonance.
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