Abashian-Booth-Crowe Effect in Basic Double-Pionic Fusion: A New Resonance?

Abstract

We report on an exclusive and kinematically complete high-statistics measurement of the basic doublepionic fusion reaction pn ! d 0 0 over the full energy region of the ABC effect, a pronounced low-mass enhancement in the -invariant mass spectrum. The measurements, which cover also the transition region to the conventional t-channel ÁÁ process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance PRL

A new possibility for light-quark dark matter

“…In this letter we present a new possibility for light-quark based DM, motivated by the recent discovery of the d * (2380) hexaquark. The properties of the d * (2380) have been established in recent years following its first experimental observation [5,6,7,8,9,10,11,12,13]. It has a mass of M d * = 2380 MeV, vacuum width Γ = 70 MeV and quantum numbers I(J P ) = 0(3 + ) and made of six light quarks; 3 u-quarks and 3 d-quarks.…”

Neutron star matter equation of state including d*-hexaquark degrees of freedom

“…Recently, we studied the role of a new degree of freedom d * (2380) (Bashkanov et al (2019)) on the nuclear EoS ). The d * (2380) is a massive positively charged non-strange particle with integer spin (J=3) and it represents the first known non-trivial hexaquark evidenced in experiment (Adlarson et al (2011(Adlarson et al ( , 2013(Adlarson et al ( , 2014). The importance of such a new degree-offreedom resides in the fact that it has the same u, d quark composition as neutrons and protons and, therefore, does not involve any strangeness degrees of freedom.…”

Form factors of the d*(2380) resonance

“…It was found that the results cannot be explained by the contribution either from the intermediate Roper excitation or from the t-channel ΔΔ contribution, except introducing an intermediate new resonance. Then, the discovery of a new resonance with a mass of about 2370-2380 MeV, a width of about 70-80 MeV, and the quantum numbers of IðJ P Þ ¼ 0ð3 þ Þ was announced [1][2][3][4]. Since the baryon number of the resonance is 2, it is believed that such a state is just the d à state which has been hunted for several decades, and, in general, can be explained by either "an exotic compact particle" or "a hadronic molecule state.…”

“…[1][2][3][4], many theoretical models for the structure of d à have been developed or proposed. Up to now, there are mainly two structural schemes which attract considerable attention of physicists.…”

“…Since then, a series of experimental studies for d à was carried out in the study of ABC effect by CELSIUS/WASA and WASA@COSY Collaborations. [1][2][3][4]. Various double-pion and single-pion decays of d à , including invariant mass spectra, Dalitz plots, Argon plots, in the pn and pA reactions, the analyzing power of the neutron-proton scattering and etc., have been carefully measured and analyzed.…”