Development of large area, ultra-thin MAPS for the ALICE experiment at the CERN LHC

openThe ALICE experiment, installed at the CERN Large Hadron Collider, studies the collisions of nuclei at the ultra-relativistic energies provided by the LHC. The aim is to study the physics of strongly interacting matter at the highest energy densities reached so far in the laboratory, where the quark-gluon plasma forms. In 2021 ALICE completed a significant upgrade of its detectors, and it is now looking forward to start the design phase of a completely new detector for the next decade. The ALICE experiment is planning to upgrade the innermost part of its Tracking System with a novel vertex detector consisting of curved wafer-scale, ultra-thin silicon sensors arranged in perfectly cylindrical layers, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layer positioned at only 18 mm radial distance from the interaction point. This new vertex detector, planned to be installed during the LHC LS3, will reduce the material budget, and improve the tracking precision and efficiency at low transverse momentum, leading to a significant advancement in the measurement of low momentum charmed hadrons and low-mass dielectrons in heavy-ion collisions. The thesis includes test, measurement and characterisation of the early sensor prototypesThe ALICE experiment, installed at the CERN Large Hadron Collider, studies the collisions of nuclei at the ultra-relativistic energies provided by the LHC. The aim is to study the physics of strongly interacting matter at the highest energy densities reached so far in the laboratory, where the quark-gluon plasma forms. In 2021 ALICE completed a significant upgrade of its detectors, and it is now looking forward to start the design phase of a completely new detector for the next decade. The ALICE experiment is planning to upgrade the innermost part of its Tracking System with a novel vertex detector consisting of curved wafer-scale, ultra-thin silicon sensors arranged in perfectly cylindrical layers, featuring an unprecedented low material budget of 0.05% X0 per layer, with the innermost layer positioned at only 18 mm radial distance from the interaction point. This new vertex detector, planned to be installed during the LHC LS3, will reduce the material budget, and improve the tracking precision and efficiency at low transverse momentum, leading to a significant advancement in the measurement of low momentum charmed hadrons and low-mass dielectrons in heavy-ion collisions. The thesis includes test, measurement and characterisation of the early sensor prototypes

Allium cyrilli Tenore 1827

Allium cyrilli Tenore (1827: 364). Type: — ITALY. Apulia: Foggia, s.d., Tenore s.n. (lectotype NAP!, here designated). Tenore's protologue consists of a diagnosis, referring also to " Allium fragrans ", an unpublished name and illustration by Domenico Cirillo (1739–1799). Unfortunately, Cirillo's collections were destroyed when he was murdered (Stafleu & Cowan 1976). Moreover, we have been unable to find the illustration cited by Tenore, but in his Herbarium in NAP we found a specimen collected in Foggia, Apulia, originally labelled as " Allium fragrans Cyrill. " and then as " Allium Cyrilli Nob. " (Fig. 1). In the protologue, the author quotes " né campi di Puglia, al Tavoliere " as locus classicus for this species. Foggia is a city within the "Tavoliere" area (a plain located in northern Apulia). Accordingly, this specimen can be considered as original material for the name and it is here selected as the lectotype.Published as part of Peruzzi, Lorenzo, Adorni, Michele, Dura, Teodoro, Ghillani, Luigi, Pasquali, Giancarlo, Rignanese, Luigi, Ronconi, Daniele & Teruzzi, Maurizio, 2012, Allium cyrilli (Amaryllidaceae): typification, taxonomy and update of the Italian distribution, pp. 53-58 in Phytotaxa 71 (1) on page 54, DOI: 10.11646/phytotaxa.71.1.11, http://zenodo.org/record/506640

Over 15% efficient wide-band-gap Cu(In,Ga)S2 solar cell: Suppressing bulk and interface recombination through composition engineering

The progress of Cu(In,Ga)S2 remains significantly limited mainly due to photovoltage (Voc) losses in the bulk and at the interfaces. Here, via a combination of photoluminescence, cathodoluminescence, electrical measurements, and ab initio modeling, we address the bulk and interface losses to improve ∼1.6-eV-band-gap (Eg) Cu(In,Ga)S2. The optoelectronic quality of the absorber improves upon reducing the [Cu]/[Ga+In] (CGI) ratio, as manifested by the suppression of deep defects, higher quasi-Fermi level splitting (QFLS), improved charge-carrier lifetime, and higher Voc. We identify antisite CuIn/CuGa as a major performance-limiting deep defect by comparing the formation energies of various intrinsic defects. Interface recombination is suppressed using a Zn(O,S) buffer layer in Cu-poor devices, which leads to the activation energy of recombination equal to the Eg. We demonstrate an efficiency of 15.2% with Voc of 902 mV from a H2S-free, Cd-free, and KCN-free process

Particle production as a function of charged-particle flattenicity in pp collisions at s\sqrt{s} = 13 TeV

International audienceThis paper reports the first measurement of the transverse momentum ($p_{\mathrm{T}}$) spectra of primary charged pions, kaons, (anti)protons, and unidentified particles as a function of the charged-particle flattenicity in pp collisions at $\sqrt{s}=13$ TeV. Flattenicity is a novel event shape observable that is measured in the pseudorapidity intervals covered by the V0 detector, $2.8<\eta<5.1$ and $-3.7<\eta<-1.7$. According to QCD-inspired phenomenological models, it shows sensitivity to multiparton interactions and is less affected by biases towards larger $p_{\mathrm{T}}$ due to local multiplicity fluctuations in the V0 acceptance than multiplicity. The analysis is performed in minimum-bias (MB) as well as in high-multiplicity events up to $p_{\mathrm{T}}=20$ GeV/$c$. The event selection requires at least one charged particle produced in the pseudorapidity interval $|\eta|<1$. The measured $p_{\mathrm{T}}$ distributions, average $p_{\mathrm{T}}$, kaon-to-pion and proton-to-pion particle ratios, presented in this paper, are compared to model calculations using PYTHIA 8 based on color strings and EPOS LHC. The modification of the $p_{\mathrm{T}}$-spectral shapes in low-flattenicity events that have large event activity with respect to those measured in MB events develops a pronounced peak at intermediate $p_{\mathrm{T}}$ ($2<p_{\mathrm{T}}<8$ GeV/$c$), and approaches the vicinity of unity at higher $p_{\mathrm{T}}$. The results are qualitatively described by PYTHIA, and they show different behavior than those measured as a function of charged-particle multiplicity based on the V0M estimator

Exploring nuclear structure with multiparticle azimuthal correlations at the LHC

International audienceUnderstanding nuclear structure provides essential insights into the properties of atomic nuclei. In this paper, details of the nuclear structure of $^{\rm 129}$Xe, such as the quadrupole deformation and the nuclear diffuseness, are studied by extensive measurements of anisotropic-flow-related observables in Xe$-$Xe collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}} = 5.44$ TeV with the ALICE detector at the LHC. The results are compared with those from Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV for a baseline, given that the $^{\rm 208}$Pb nucleus is not deformed. Furthermore, comprehensive comparisons are performed with a state-of-the-art hybrid model using IP-Glasma+MUSIC+UrQMD. It is found that among various IP-Glasma+MUSIC+UrQMD calculations with different values of nuclear parameters, the one using a nuclear diffuseness parameter of $a_0=0.492$ and a nuclear quadrupole deformation parameter of $\beta_2=0.207$ provides a better description of the presented flow measurements. These studies represent an important step towards a thorough exploration of the imaging power of nuclear collisions at ultrarelativistic energy and the search for the imprint of nuclear structure on various flow observables in heavy-ion collisions at the LHC. The findings demonstrate the potential of nuclear structure studies at the TeV energy scale and highlight that the LHC experiments can complement existing low-energy experiments on nuclear structure studies

J/ψ\psi-hadron correlations at midrapidity in pp collisions at s\sqrt{s} = 13 TeV

International audienceWe report on the measurement of inclusive, non-prompt, and prompt J/$\psi$-hadron correlations by the ALICE Collaboration at the CERN Large Hadron Collider in pp collisions at a center-of-mass energy of 13 TeV. The correlations are studied at midrapidity ($|y| < 0.9$) in the transverse momentum ranges $p_{\rm T} < 40~\text{GeV}/c$ for the J/$\psi$ and $0.15 < p_{\rm T} < 10$ GeV/$c$ and $|\eta|<0.9$ for the associated hadrons. The measurement is based on minimum bias and high multiplicity data samples corresponding to integrated luminosities of $L_{\text{int}} = 34~\text{nb}^{-1}$ and $L_{\text{int}} = 6.9~\text{pb}^{-1}$, respectively. In addition, two more data samples are employed, requiring, on top of the minimum bias condition, a threshold on the tower energy of $E = 4$ and $9~\text{GeV}$ in the ALICE electromagnetic calorimeters, which correspond to integrated luminosities of $L_{\text{int}} = 0.9~\text{pb}^{-1}$ and $L_{\text{int}} = 8.4~\text{pb}^{-1}$, respectively. The results are presented as associated hadron yields per J/$\psi$ trigger as a function of the azimuthal angle difference between the associated hadrons and J/$\psi$ mesons. The integrated near-side and away-side correlated yields are also extracted as a function of the J/$\psi$ transverse momentum. The measurements are discussed in comparison to PYTHIA calculations

Measurement of f1_{1}(1285) production in pp collisions at s\mathbf{\sqrt{{\textit s}}} = 13 TeV

International audienceThis study presents the first measurement of the f$_{1}$(1285) resonance using the ALICE detector in inelastic proton--proton collisions at a center-of-mass energy of 13 TeV. The resonance is reconstructed at midrapidity ($|y| <$ 0.5) through the hadronic decay channel f$_{1} (1285) \rightarrow \mathrm{K^{0}_{S} K^{\pm}\pi^{\mp}}$. Key measurements include the determination of its mass, transverse-momentum integrated yield, and average transverse momentum. Additionally, the ratio of the transverse-momentum integrated yield of f$_{1}$(1285) to pion is compared with calculations from the canonical statistical hadronization model. The model calculation, assuming a zero total strangeness content for f$_{1}$(1285), reproduces the data within 1$\sigma$ deviation, shedding light on the quark composition of f$_{1}$(1285)

J/ψ\psi-hadron correlations at midrapidity in pp collisions at s\sqrt{s} = 13 TeV

International audienceWe report on the measurement of inclusive, non-prompt, and prompt J/$\psi$-hadron correlations by the ALICE Collaboration at the CERN Large Hadron Collider in pp collisions at a center-of-mass energy of 13 TeV. The correlations are studied at midrapidity ($|y| < 0.9$) in the transverse momentum ranges $p_{\rm T} < 40~\text{GeV}/c$ for the J/$\psi$ and $0.15 < p_{\rm T} < 10$ GeV/$c$ and $|\eta|<0.9$ for the associated hadrons. The measurement is based on minimum bias and high multiplicity data samples corresponding to integrated luminosities of $L_{\text{int}} = 34~\text{nb}^{-1}$ and $L_{\text{int}} = 6.9~\text{pb}^{-1}$, respectively. In addition, two more data samples are employed, requiring, on top of the minimum bias condition, a threshold on the tower energy of $E = 4$ and $9~\text{GeV}$ in the ALICE electromagnetic calorimeters, which correspond to integrated luminosities of $L_{\text{int}} = 0.9~\text{pb}^{-1}$ and $L_{\text{int}} = 8.4~\text{pb}^{-1}$, respectively. The results are presented as associated hadron yields per J/$\psi$ trigger as a function of the azimuthal angle difference between the associated hadrons and J/$\psi$ mesons. The integrated near-side and away-side correlated yields are also extracted as a function of the J/$\psi$ transverse momentum. The measurements are discussed in comparison to PYTHIA calculations

Measurement of the inclusive isolated-photon production cross section in pp and Pb−-Pb collisions at sNN=5.02\sqrt{s_{\rm NN}}=5.02 TeV

International audienceThe ALICE Collaboration at the CERN LHC has measured the inclusive production cross section of isolated photons at midrapidity as a function of the photon transverse momentum ($p_{\rm T}^{\gamma}$), in Pb-Pb collisions in different centrality intervals, and in pp collisions, at centre-of-momentum energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. The photon transverse momentum range is between 10-14 and 40-140 GeV/$c$, depending on the collision system and on the Pb-Pb centrality class. The result extends to lower $p_{\rm T}^{\gamma}$ than previously published results by the ATLAS and CMS experiments at the same collision energy. The covered pseudorapidity range is $|\eta^{\gamma}| <0.67$. The isolation selection is based on a charged particle isolation momentum threshold $p_{\rm T}^{\rm iso,~ch} = 1.5$ GeV/$c$ within a cone of radii $R=0.2$ and $0.4$. The nuclear modification factor is calculated and found to be consistent with unity in all centrality classes, and also consistent with the HG-PYTHIA model, which describes the event selection and geometry biases that affect the centrality determination in peripheral Pb-Pb collisions. The measurement is compared to next-to-leading order perturbative QCD calculations and to the measurements of isolated photons and Z$^0$ bosons from the CMS experiment, which are all found to be in agreement