The strong interaction among hadrons has been measured in the past by scattering experiments. Although this technique has been extremely successful in providing information about the nucleon-nucleon ...and pion-nucleon interactions, when unstable hadrons are considered the experiments become more challenging. In the last few years, the analysis of correlations in the momentum space for pairs of stable and unstable hadrons measured in
pp
and
p
+Pb collisions by the ALICE Collaboration at the LHC has provided a new method to investigate the strong interaction among hadrons. In this article, we review the numerous results recently achieved for hyperon-nucleon, hyperon-hyperon, and kaon-nucleon pairs, which show that this new method opens the possibility of measuring the residual strong interaction of any hadron pair.
We present a new analysis framework called “Correlation Analysis Tool using the Schrödinger equation” (CATS) which computes the two-particle femtoscopy correlation function
C
(
k
), with
k
being the ...relative momentum for the particle pair. Any local interaction potential and emission source function can be used as an input and the wave function is evaluated exactly. In this paper we present a study on the sensitivity of
C
(
k
) to the interaction potential for different particle pairs: p–p, p–
Λ
,
K
-
–p,
K
+
–p, p–
Ξ
-
and
Λ
–
Λ
. For the p–p Argonne
v
18
and Reid Soft-Core potentials have been tested. For the other pair systems we present results based on strong potentials obtained from effective Lagrangians such as
χ
EFT for p–
Λ
, Jülich models for
K
(
K
¯
)
–N and Nijmegen models for
Λ
–
Λ
. For the p–
Ξ
-
pairs we employ the latest lattice results from the HAL QCD collaboration. Our detailed study of different interacting particle pairs as a function of the source size and different potentials shows that femtoscopic measurements can be exploited in order to constrain the final state interactions among hadrons. In particular, small collision systems of the order of 1 fm, as produced in pp collisions at the LHC, seem to provide a suitable environment for quantitative studies of this kind.
We review the present status of the experimental and theoretical developments in the field of strangeness in nuclei and neutron stars. We start by discussing the K̄N interaction, that is governed by ...the presence of the Λ(1405). We continue by showing the two-pole nature of the Λ(1405), and the production mechanisms in photon-, pion-, kaon-induced reactions as well as proton–proton collisions, while discussing the formation of K̄NN bound states. We then move to the theoretical and experimental analysis of the properties of kaons and antikaons in dense nuclear matter, paying a special attention to kaonic atoms and the analysis of strangeness creation and propagation in nuclear collisions. Next, we examine the ϕ meson and the advances in photoproduction, proton-induced and pion-induced reactions, so as to understand its properties in dense matter. Finally, we address the dynamics of hyperons with nucleons and nuclear matter, and the connection to the phases of dense matter with strangeness in the interior of neutron stars.
We report on discharge probability studies with a single Gas Electron Multiplier (GEM) under irradiation with alpha particles in Ar- and Ne-based gas mixtures. The discharge probability as a function ...of the GEM absolute gain is measured for various distances between an alpha source and the GEM. We observe that the discharge probability is the highest when the charge deposit occurs in the closest vicinity of the GEM holes, and that the breakdown limit is lower for argon mixtures than for neon mixtures.
Our experimental findings are in line with the well-grounded hypothesis of the charge density being the limiting factor of GEM stability against discharges. A detailed comparison of the measurements with GEANT4 simulations allowed us to extract the critical charge density leading to the formation of a spark in a GEM hole. This number is found to be within the range of (5−9)×106 electrons after amplification, and it depends on the gas mixture.
We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of ...physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.
Systematic investigation of critical charge limits in Thick GEMs Gasik, P.; Lautner, L.; Fabbietti, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2023, Letnik:
1047
Journal Article
Recenzirano
Odprti dostop
We present discharge probability studies performed with a single Thick Gas Electron Multiplier (THGEM) irradiated with alpha particles in Ar-CO2 and Ne-CO2 mixtures. We observe a clear dependency of ...the discharge stability on the noble gas and quencher content pointing to lighter gases being more stable against the development of streamer discharges. A detailed comparison of the measurements with Geant4 simulations allowed us to extract the critical charge value leading to the formation of a spark in a THGEM hole, which is found to be within the range of (3 to 7)×106 electrons, depending on the gas mixture.
Our experimental findings are compared to previous GEM results. We show that the discharge probability of THGEMs exceeds the one measured with GEMs by orders of magnitude. This can be explained with simple geometrical considerations, where primary ionization is collected by a lower number of holes available in a THGEM structure, reaching higher primary charge densities and thus increasing the probability of a spark occurrence. However, we show that the critical charge limits are similar for both amplification structures.
In this work GEM and single-hole Thick GEM structures, composed of different coating materials, are studied. The used foils incorporate conductive layers made of copper, aluminium, molybdenum, ...stainless steel, tungsten and tantalum. The main focus of the study is the determination of the material dependence of the formation of electrical discharges in GEM-based detectors. For this task, discharge probability measurements are conducted with several Thick GEM samples using a basic electronics readout chain. In addition to that, optical spectroscopy methods are employed to study the light emitted during discharges from the different foils. It is observed that the light spectra of GEMs include emission lines from the conductive layer material. This indicates the presence of the foil material in the discharge plasma after the initial spark. However, no lines associated with the coating material are observed while studying spark discharges induced in Thick GEMs. It is concluded that the conductive layer material does not play a substantial role in terms of stability against primary discharges. However, a strong material dependence is observed in the case of secondary discharge formation, pointing to molybdenum coating as the one providing increased stability.
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