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Spin and symmetry properties of all-charm tetraquarks
No full textThe traditional quark model accounts for the existence of baryons, like protons and neutrons, which consist of three quarks, as well as mesons, composed of a quark and antiquark pair. Only recently has substantial evidence started to accumulate for exotic states composed of four or five quarks or antiquarks. In this study, the CMS Collaboration investigates the recently discovered family of three tetraquark candidates composed of four charm quarks and antiquarks. The exact nature of their internal structure remains uncertain. They could either be tightly bound states of true tetraquarks, similar to quarks bound within protons and neutrons, or molecules composed of two familiar mesons, loosely bound like protons and neutrons in a nucleus,
with other potential configurations still being considered. Angular analysis techniques for decay products, developed for the discovery and characterization of the Higgs boson, are now being applied to the new exotic states.
The quantum numbers for parity and charge conjugation symmetries are found to be +1. The spin of these exotic states is most consistent with , a value that is uncommon for such particles,
while the and are excluded at 95\% and 99\% confidence level, respectively. The quantum numbers match the expected values for tetraquarks with specific configurations of spin and angular momenta of its components, which helps in narrowing down the tetraquark's internal structure
Development a test bench for characterization of neutron detectors in pulsed neutron fields at the n{\textunderscore}TOF facility
No full textSearch for low-mass hidden valley dark showers with displaced dimuons in proton-proton collisions at
No full textA search for signatures of a dark analog to quantum chromodynamics is performed. The analysis targets long-lived dark mesons that decay into standard model particles with a high branching fraction to muons. A unique dataset with B meson events is used. It was collected by the CMS experiment at the CERN LHC in 2018 using displaced muon triggers, which have a high trigger efficiency for the signal models. Resonant dimuon signatures are searched for, with both pointing and non-pointing topologies. No significant excess is observed beyond the standard model expectation. Upper limits on the branching ratio of Higgs boson decays to dark partons are determined to be less than , at confidence level, surpassing and extending existing limits for the mean proper lifetime of less than approximately for a mass as low as . First limits are set for extended dark shower models, probing the low-mass region down to
Comparison of the Performance of the Dual-Readout Calorimeter for different absorbers
No full textFuture lepton collider experiments (FCC-ee and CEPC) require excellent hadronic energy resolution to exploit their advantages. The dual-readout calorimeter can satisfy this requirement by using two types of calorimeter signals, which provide complementary information about the shower development. The calorimeter design considers a range of different absorbers. We investigated the performance, including the energy resolution of EM and hadronic particles as well as shower developments, of the dual-readout calorimeter for different absorbers such as Fe, Brass, Cu, Pb, and W. In this paper, we present a performance comparison of these absorbers derived from GEANT4 simulation studies
Recent conventional and exotic charmonia results from LHCb
No full textQuarkonia production in heavy-ion collisions is an important experimental probe that sheds light on the heavy quark interaction with the nuclear medium. The bound quarkonium states undergo dissociation and recombination in PbPb collisions, where they can also experience the initial and final state effects such as shadowing and co-mover breakup. With the large datasets of pp and pPb collisions, and excellent vertexing capabilities allowing separation of the prompt and b-decay components, LHCb performs precise measurements of J/ψ, ψ(2S ) and, for the first time at the LHC, χc production and modification in small collision systems. This contribution will discuss these results, along with the first measurement of the nuclear modification factor of the exotic χc1(3872)
Top-quark physics highlights from ATLAS
No full textThe extensive top-quark samples collected by the ATLAS experiment at the LHC have enabled precise measurements of the top-quark production cross-section, reaching unprecedented accuracy and extending into previously unexplored kinematic regimes. These datasets have also provided new insights into top-quark properties, facilitated the observation of rare production processes predicted by the Standard Model, and led to significant advancements in searches within the top-quark sector. This contribution presents key highlights from the ATLAS top-quark physics program, showcasing the latest measurements and emphasizing the sector's broad scientific potential