Zhang, X. Y., Shi, P. P., & Guo, F. K. (2025). Production of 1-+ exotic charmonium-like states in electron-positron collisions. Phys. Lett. B, 867, 139603–8pp.
Abstract: The absence of observed charmonium-like states with the exotic quantum numbers J=1+ has prompted us to investigate the production rates of the 1 DD, (2420) and D D, (2420) hadronic molecules, which we refer to as n and, respectively, in electron-positron collisions. Assuming a hadronic molecular nature for the vector charmonium-like states (4360) and yr(4415), we evaluate the radiative decay widths of (4360)-> 77 and (4415) yn. Using these decay widths, we estimate the cross sections for producing, and, in electron-positron annihilations, as well as the event numbers at the planned Super r-Charm Facility. Our results suggest that the ideal energy region for observing these states is around 4.44 and 4.50 GeV, just above the D D (2420) and D D (2460) thresholds, respectively.
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Zhang, S. C., Duan, M. Y., Lyu, W. T., Wang, G. Y., Zhu, J. Y., & Wang, E. (2024). Explore the properties of Λ(1670) in the Cabibbo-favored process Λc+ → p K- π+. Eur. Phys. J. C, 84(12), 1253–8pp.
Abstract: Recently, the Belle and LHCb Collaborations have measured the Lambda c+-> pK-pi+ invariant mass distribution, which shows a clear cusp structure around the eta Lambda threshold. In this work, we have analyzed this process by considering the triangle mechanism and the S-wave pseudoscalar meson-octet baryon interactions within the chiral unitary approach, which dynamically generates the Lambda(1670). Our results are in good agreement with the Belle measurements, which implies that the cusp structure around eta Lambda threshold could be associated with the Lambda(1670) with the molecular nature.
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Zhang, G. et al, Algora, A., Nacher, E., Orrigo, S. E. A., Perez-Vidal, R. M., & Rubio, B. (2025). Approaching 100Sn: Structural evolution in 98,100Cd via lifetime measurements. Phys. Lett. B, 863, 139378–7pp.
Abstract: The lifetimes of low-lying excited states below the 8(+) seniority isomer were directly measured using fast timing detectors in the neutron-deficient isotopes Cd-98,Cd-100. This experiment was conducted with the DEcay SPECtroscopy (DESPEC) setup at GSI, where the ions of interest were produced via a fragmentation reaction and identified using the FRagment Separator (FRS) before being implanted in the AIDA active stopper system, and the gamma rays emitted during the de-excitation of isomeric states were detected by the LaBr3 FATIMA Array. The newly deduced values for the reduced transition probabilities were compared with shell-model calculations using different interactions and effective charges. The results indicate that, while Cd-98 aligns well with a seniority scheme description, in Cd-100 the transition strengths among low-lying states are not fully reproduced, and the nature of these states remains an open problem within the present theoretical description. Ultimately, a key element in the description of this region, crucial for nuclear physics and astrophysics, appears to be the proton-neutron term of the nuclear effective interaction.
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Zhai, Q. Y., Molina, R., Oset, E., & Geng, L. S. (2025). Study of the exotic three-body ND*Kbar* system. Phys. Rev. D, 111(3), 034039–6pp.
Abstract: We have studied the ND*K<overline>* system in the framework of the fixed center approximation to the Faddeev equations, taking the exotic D*K<overline>* system as the cluster and allowing the N to interact with the components of the cluster. Previous studies have determined the existence of three states of spin 0, 1, 2 for the D*K<overline>* system, the one of spin 0 associated to the X0(2900) state observed by the LHCb Collaboration. From this perspective, we find five states with total spin 1/2, 3/2, 5/2, with bindings from 10 to 30 MeV and widths below 60 MeV, which could be well identified. We also discuss the decay channels of these states that should help in future experimental searches for these states.
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Yu, J. J., Mollaebrahimi, A., Ayet, S., Dickel, T., Plass, W. R., Wilsenach, H., et al. (2024). A compact ion source combining electron-impact and thermal ionization for multiple-reflection time-of-flight mass spectrometry. Rev. Sci. Instrum., 95(8), 083309–7pp.
Abstract: A compact ion source combining electron impact and thermal ionization has been developed and commissioned in two Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) setups at the Fragment Separator Ion Catcher at the GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany, and at TRIUMF's Ion Trap for Atomic and Nuclear science at TRIUMF Canada's particle accelerator center, Vancouver, Canada. The ion source is notable for its compact dimensions of 50 mm in height and 68 mm in diameter. The ion source is currently in daily operation at both facilities. Design, simulations, and results of combining ions from thermal and electron-impact ionization of different gases (perfluoropropane and sulfur hexafluoride) are presented in this work. The systematic effects of heating power on the thermal source were studied in detail. The source has demonstrated stable and long-term production of reference ions over a wide mass range for the MR-TOF-MS. This versatile ion source has also been used to optimize and investigate the transport of ions with different chemical reactivity and ionization potentials.
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Yeung, T. T. et al, Morales, A. I., Tain, J. L., Alcala, G., Algora, A., Agramunt, J., et al. (2024). First Exploration of Monopole-Driven Shell Evolution above the N=126 Shell Closure: New Millisecond Isomers in Tl-213 and Tl-215. Phys. Rev. Lett., 133(7), 072501–7pp.
Abstract: Isomer spectroscopy of heavy neutron-rich nuclei beyond the N = 126 closed shell has been performed for the first time at the Radioactive Isotope Beam Factory of the RIKEN Nishina Center. New millisecond isomers have been identified at low excitation energies, 985.3(19) keV in Tl-213 and 874(5) keV in Tl-215. The measured half-lives of 1.34(5) ms in Tl-213 and 3.0(3) ms in Tl-215 suggest spins and parities 11/2(-) with the single proton-hole configuration pi h(11/2) as leading component. They are populated via E1 transitions by the decay of higher-lying isomeric states with proposed spin and parity 17/2(+), interpreted as arising from a single pi s(1/2) proton hole coupled to the 8(+) seniority isomer in the PbA + 1 cores. The lowering of the 11/2(-) states is ascribed to an increase of the pi h(11/2) proton effective single-particle energy as the second nu g(9/2) orbital is filled by neutrons, owing to a significant reduction of the proton-neutron monopole interaction between the pi h(11/2) and nu g(9/2) orbitals. The new ms isomers provide the first experimental observation of shell evolution in the almost unexplored N > 126 nuclear region below doubly magic Pb-208.
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Yang, W. Q., Pan, S., Di Valentino, E., Mena, O., Mota, D. F., & Chakraborty, S. (2025). Probing the cold nature of dark matter. Phys. Rev. D, 111(10), 103509–16pp.
Abstract: A pressureless dark matter component fits well with several cosmological observations. However, there are indications that cold dark matter may encounter challenges in explaining observations at small scales, particularly at galactic scales. Observational data suggest that dark matter models incorporating a pressure component could provide solutions to these small-scale problems. In this work, we investigate the possibility that present-day dark matter may result from a decaying noncold dark matter sector transitioning into the dark energy sector. As the sensitivity of astronomical surveys rapidly increases, we explore an interacting scenario between dark energy and noncold dark matter, where dark energy has a constant equation of state (wde), and dark matter, being noncold, also has a constant (non-zero) equation of state (wdm). Considering the phantom and quintessence nature of dark energy, characterized by its equation of state, we separately analyze interacting phantom and interacting quintessence scenarios. We constrain these scenarios using cosmic microwave background (CMB) measurements and their combination with external probes, such as DESI-BAO and PantheonPlus. From our analyses, we find that a very mild preference for noncold dark matter cannot be excluded based on the employed datasets. Additionally, for some datasets, there is a pronounced preference for the presence of an interaction at more than 95% confidence level (CL). Moreover, when the dark energy equation of state lies in the phantom regime, the S8 tension can be alleviated. This study suggests that cosmological models incorporating a noncold dark matter component should be considered as viable scenarios with novel phenomenological implications, as reflected in the present work.
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Yaneva, A. et al, & Algora, A. (2024). The shape of the Tz =+1 nucleus 94Pd and the role of proton-neutron interactions on the structure of its excited states. Phys. Lett. B, 855, 138805–7pp.
Abstract: Reduced transition probabilities have been extracted between excited, yrast states in the N = Z + 2 nucleus Pd-94. The transitions of interest were observed following decays of the I-pi = 14(+), E-x = 2129-keV isomeric state, which was populated following the projectile fragmentation of a Xe-124 primary beam at the GSI Helmholtzzentrum fur Schwerionenforschung accelerator facility as part of FAIR Phase-0. Experimental information regarding the reduced E2 transition strengths for the decays of the yrast 8(+) and 6(+) states was determined following isomer-delayed E-gamma 1 – E-gamma 2 – Delta T-2,T-1 coincidence method, using the LaBr3(Ce)-based FATIMA fast-timing coincidence gamma-ray array, which allowed direct determination of lifetimes of states in Pd-94 using the Generalized Centroid Difference (GCD) method. The experimental value for the half-life of the yrast 8(+) state of 755(106) ps results in a reduced transition probability of B(E2:8(+)-> 6(+)) = 205(-25)(+34) e(2) fm(4), which enables a precise verification of shell-model calculations for this unique system, lying directly between the N = Z line and the N = 50 neutron shell closure. The determined B(E2) value provides an insight into the purity of (g(9/2))(n) configurations in competition with admixtures from excitations between the (lower) N = 3pf and (higher) N = 4gds orbitals for the first time. The results indicate weak collectivity expected for near-zero quadrupole deformation and an increasing importance of the T = 0 proton-neutron interaction at N = 48.
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Xu, Z. Y. et al, & Morales, A. I. (2024). Compound-Nucleus and Doorway-State Decays of β-Delayed Neutron Emitters 51,52,53 K. Phys. Rev. Lett., 133(4), 042501–7pp.
Abstract: We investigated decays of 51,52,53Kat the ISOLDE Decay Station at CERN in order to understand the mechanism of the β-delayed neutron-emission (βn) process. The experiment quantified neutron and gamma-ray emission paths for each precursor. We used this information to test the hypothesis, first formulated by Bohr in 1939, that neutrons in the βn process originate from the structureless “compound nucleus.” The data are consistent with this postulate for most of the observed decay paths. The agreement, however, is surprising because the compound-nucleus stage should not be achieved in the studied β decay due to insufficient excitation energy and level densities in the neutron emitter. In the 53 K βn decay, we found a preferential population of the first excited state in 52 Ca that contradicted Bohr's hypothesis. The latter was interpreted as evidence for direct neutron emission sensitive to the structure of the neutron-unbound state. We propose that the observed nonstatistical neutron emission proceeds through the coupling with nearby doorway states that have large neutron-emission probabilities. The appearance of “compound- nucleus” decay is caused by the aggregated small contributions of multiple doorway states at higher excitation energy.
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Xiao, C. W., Dias, J. M., Dai, L. R., Liang, W. H., & Oset, E. (2024). Triangle singularity in the J/ψ → ϕ π+ a−0(π−η) ,ϕ π− a+0(π+η) decays. Phys. Rev. D, 109(7), 074033–11pp.
Abstract: We study the J= psi -> phi pi + a 0 ( 980 ) – ( a – 0 -> pi – eta ) decay, evaluating the double mass distribution in terms of the pi – eta and pi + a – 0 invariant masses. We show that the pi – eta mass distribution exhibits the typical cusp structure of the a 0 ( 980 ) seen in recent high statistics experiments, and the pi + a – 0 spectrum shows clearly a peak around M inv ( pi + a – 0 ) = 1420 MeV, corresponding to a triangle singularity. When integrating over the two invariant masses we find a branching ratio for this decay of the order of 10 – 5 , which is easily accessible in present laboratories. We also call attention to the fact that the signal obtained is compatible with a bump experimentally observed in the eta pi + pi – mass distribution in the J= psi -> phi eta pi + pi – decay and encourage further analysis to extract from there the phi pi + a – 0 and phi pi – a + 0 decay modes.
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