Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Status of the Fast Interaction Trigger detector for the ALICE upgrade

During the second Long Shutdown (LS2) of the LHC, ALICE has installed three new detectors and implemented continuous data readout with online reconstruction and data compression for several other subsystems. The changes are needed to benefit from the increased luminosity of the LHC during Run 3 and 4. The ALICE interaction rate will increase, with respect to Run 1 and 2, by up to two orders of magnitude, reaching 50 kHz for Pb-Pb and up to 1 MHz for pp collisions. One of the new ALICE detectors is the Fast Interaction Trigger (FIT). Its main functionality includes generating minimum-latency interaction triggers ($<425$ ns), luminosity monitoring with online feedback to the LHC, a precise measurement of the collision time with a resolution better than 40 ps, determination of the centrality and event plane for heavy-ion collisions, and tagging of diffractive and ultra-peripheral events. The FIT detector consists of three subsystems: two fast Cherenkov arrays with 2 cm thick quartz radiators coupled to modified MCP-PMT photosensors (FT0), a large-area scintillator disc (FV0) implementing a novel light collection system, and the forward diffractive detector (FDD). FDD comprises two plastic scintillator arrays with fast wavelength shifting bars, optical fibre bundles, and PMTs. The FDD arrays are located ~$\pm 20$ m away from the nominal interaction point, along the beam line. A brief description of the detector and its functionalities is given together with the installation and commissioning status

Status of the Fast Interaction Trigger detector of ALICE

The Fast Interaction Trigger (FIT) is one of the detectors installed in the ALICE experiment during the second Long Shutdown (LS2) of the LHC to cope with the new collision rates of 50 kHz for Pb-Pb and up to 1 MHz for pp collisions. FIT comprised of the FT0, FV0, and FDD sub-detectors that use Cherenkov and scintillator technologies. The sub-detectors are placed in the forward regions on both sides of the interaction point. FIT delivers fast triggers and determines online vertex, luminosity, multiplicity and centrality. FIT also contributes to beam-background monitoring in ALICE and provides feedback on the beam quality to the LHC.This work presents an overview of the FIT detector and its performance with pp and heavy-ion collision data collected during 2022 and 2023

The performance of ALICE-Diffractive detector in a beam-test.

The ALICE Diffractive (AD) detector is a forward detector that was added to ALICE to extend the acceptance of the experiment in the forward rapidity region in order to improve the sensitivity for diffraction physics. The AD detector will contribute to measure the inelastic proton-proton cross-section and to provide additional measurements of centrality in Pb-Pb, proton-Pb and Xe-Xe collisions. The AD is used as a trigger as well as a beam quality monitor at Point 2 of the LHC. AD consists of two assemblies, ADA and ADC, each station consist of two layers of scintillators. Two detector modules identical to those installed in the experiment were tested in the Proton Synchrotron T10 secondary beam at CERN, at four different momenta: 1, 1.5, 2 and 6 GeV/c. The modules were scanned using the beam along the scintillator pad, which is the biggest part of the detector, and additionally the other components, such as optical connectors, optical fibres, photomultiplier and the wavelength shifting bars. The experimental setup used for this study allow us to identify pions and protons coming from the beam. An additional setup to measure cosmic rays was mounted to have a reference. With those measurements, we prove that the efficiency along the plastic scintillators pads is homogeneous, which is an important requirement for a good performance in the experiment. The plastic scintillators pads were extensively analyzed to obtain the timing and charge properties for the different particles species and momenta, obtaining a suitable time resolution and charge response for a minimum ionization particle. It is worth to mention that the timing correction technique was successfully implemented for a MIP and was obtained the correlation between the energy deposited by a particle in the detector and the measurement of the charge. All those studies made for the plastic scintillator were also done for the rest of components (with exception of the correlation of the energy deposition and the charge). The results show that the efficiencies and charges of those sections are low in comparison with the scintillator pad, except for the photomultiplier that have an important contribution when a particle hits its photocathode. Additionally, the wavelength shifting bar was studied in detail by using a pixel detector. Finally, the time resolution and charge were correlated to compare them with the obtained in proton-proton collisions in the ALICE experiment. Also is presented an overview of the diffractive physics and the experiments, which attempt to study and understand the physics related to diffraction in high energy physics

Multiplicity dependence of light (anti-)nuclei production in p–Pb collisions at sNN=5.02 TeV

The measurement of the deuteron and anti-deuteron production in the rapidity range −1 < y < 0 as a function of transverse momentum and event multiplicity in p–Pb collisions at √sNN = 5.02 TeV is presented. (Anti-)deuterons are identified via their specific energy loss dE/dx and via their time-of- flight. Their production in p–Pb collisions is compared to pp and Pb–Pb collisions and is discussed within the context of thermal and coalescence models. The ratio of integrated yields of deuterons to protons (d/p) shows a significant increase as a function of the charged-particle multiplicity of the event starting from values similar to those observed in pp collisions at low multiplicities and approaching those observed in Pb–Pb collisions at high multiplicities. The mean transverse particle momenta are extracted from the deuteron spectra and the values are similar to those obtained for p and particles. Thus, deuteron spectra do not follow mass ordering. This behaviour is in contrast to the trend observed for non-composite particles in p–Pb collisions. In addition, the production of the rare 3He and 3He nuclei has been studied. The spectrum corresponding to all non-single diffractive p-Pb collisions is obtained in the rapidity window −1 < y < 0 and the pT-integrated yield dN/dy is extracted. It is found that the yields of protons, deuterons, and 3He, normalised by the spin degeneracy factor, follow an exponential decrease with mass number

Investigating the nature of the K∗0(700) state with π±K0S correlations at the LHC

The first measurements of femtoscopic correlations with the particle pair combinations π±K0S in pp collisions at s√=13 TeV at the Large Hadron Collider (LHC) are reported by the ALICE experiment. Using the femtoscopic approach, it is shown that it is possible to study the elusive K∗0(700) particle that has been considered a tetraquark candidate for over forty years. Boson source parameters and final-state interaction parameters are extracted by fitting a model assuming a Gaussian source to the experimentally measured two-particle correlation functions. The final-state interaction is modeled through a resonant scattering amplitude, defined in terms of a mass and a coupling parameter, decaying into a π±K0S pair. The extracted mass and Breit-Wigner width, derived from the coupling parameter, of the final-state interaction are found to be consistent with previous measurements of the K∗0(700). The small value and increasing behavior of the correlation strength with increasing source size support the hypothesis that the K∗0(700) is a four-quark state, i.e. a tetraquark state. This latter trend is also confirmed via a simple geometric model that assumes a tetraquark structure of the K∗0(700) resonance

Investigating the nature of the K0∗(700)^*_0(700) state with π±\pi^\pmKS0^0_{\rm S} correlations at the LHC

International audienceThe first measurements of femtoscopic correlations with the particle pair combinations $\pi^\pm$K$^0_{\rm S}$ in pp collisions at $\sqrt{s}=13$ TeV at the Large Hadron Collider (LHC) are reported by the ALICE experiment. Using the femtoscopic approach, it is shown that it is possible to study the elusive K$^*_0(700)$ particle that has been considered a tetraquark candidate for over forty years. Boson source parameters and final-state interaction parameters are extracted by fitting a model assuming a Gaussian source to the experimentally measured two-particle correlation functions. The final-state interaction is modeled through a resonant scattering amplitude, defined in terms of a mass and a coupling parameter, decaying into a $\pi^\pm$K$^0_{\rm S}$ pair. The extracted mass and Breit-Wigner width, derived from the coupling parameter, of the final-state interaction are found to be consistent with previous measurements of the K$^*_0(700)$. The small value and increasing behavior of the correlation strength with increasing source size support the hypothesis that the K$^*_0(700)$ is a four-quark state, i.e. a tetraquark state. This latter trend is also confirmed via a simple geometric model that assumes a tetraquark structure of the K$^*_0(700)$ resonance

Investigating the nature of the K0∗^*_0(700) state with π±\pi^\pmKS0^0_{\rm S} correlations at the LHC

The first measurements of femtoscopic correlations with the particle pair combinations $\pi^\pm$K$^0_{\rm S}$ in pp collisions at $\sqrt{s}=13$ TeV at the Large Hadron Collider (LHC) are reported by the ALICE experiment. Using the femtoscopic approach, it is shown that it is possible to study the elusive K$^*_0(700)$ particle that has been considered a tetraquark candidate for over forty years. Boson source parameters and final-state interaction parameters are extracted by fitting a model assuming a Gaussian source to the experimentally measured two-particle correlation functions. The final-state interaction is modeled through a resonant scattering amplitude, defined in terms of a mass and a coupling parameter, decaying into a $\pi^\pm$K$^0_{\rm S}$ pair. The extracted mass and Breit--Wigner width, derived from the coupling parameter, of the final-state interaction are found to be consistent with previous measurements of the K$^*_0(700)$. The small value and increasing behavior of the correlation strength with increasing source size support the hypothesis that the K$^*_0(700)$ is a four-quark state, i.e. a tetraquark state. This latter trend is also confirmed via a simple geometric model that assumes a tetraquark structure of the K$^*_0(700)$ resonance.The first measurements of femtoscopic correlations with the particle pair combinations $\pi^\pm$K$^0_{\rm S}$ in pp collisions at $\sqrt{s}=13$ TeV at the Large Hadron Collider (LHC) are reported by the ALICE experiment. Using the femtoscopic approach, it is shown that it is possible to study the elusive K$^*_0(700)$ particle that has been considered a tetraquark candidate for over forty years. Boson source parameters and final-state interaction parameters are extracted by fitting a model assuming a Gaussian source to the experimentally measured two-particle correlation functions. The final-state interaction is modeled through a resonant scattering amplitude, defined in terms of a mass and a coupling parameter, decaying into a $\pi^\pm$K$^0_{\rm S}$ pair. The extracted mass and Breit-Wigner width, derived from the coupling parameter, of the final-state interaction are found to be consistent with previous measurements of the K$^*_0(700)$. The small value and increasing behavior of the correlation strength with increasing source size support the hypothesis that the K$^*_0(700)$ is a four-quark state, i.e. a tetraquark state. This latter trend is also confirmed via a simple geometric model that assumes a tetraquark structure of the K$^*_0(700)$ resonance

Investigating the nature of the K0∗(700)^*_0(700) state with π±\pi^\pmKS0^0_{\rm S} correlations at the LHC

International audienceThe first measurements of femtoscopic correlations with the particle pair combinations $\pi^\pm$K$^0_{\rm S}$ in pp collisions at $\sqrt{s}=13$ TeV at the Large Hadron Collider (LHC) are reported by the ALICE experiment. Using the femtoscopic approach, it is shown that it is possible to study the elusive K$^*_0(700)$ particle that has been considered a tetraquark candidate for over forty years. Boson source parameters and final-state interaction parameters are extracted by fitting a model assuming a Gaussian source to the experimentally measured two-particle correlation functions. The final-state interaction is modeled through a resonant scattering amplitude, defined in terms of a mass and a coupling parameter, decaying into a $\pi^\pm$K$^0_{\rm S}$ pair. The extracted mass and Breit-Wigner width, derived from the coupling parameter, of the final-state interaction are found to be consistent with previous measurements of the K$^*_0(700)$. The small value and increasing behavior of the correlation strength with increasing source size support the hypothesis that the K$^*_0(700)$ is a four-quark state, i.e. a tetraquark state. This latter trend is also confirmed via a simple geometric model that assumes a tetraquark structure of the K$^*_0(700)$ resonance