The next generation of MAPS for future tracking detectors will have to meet stringent requirements placed on them. One such detector is the ALICE ITS3 that aims to be very light at 0.07 % X/X-0 per layer and have a low power consumption in the active area of 40 mW/cm(2) by implementing wafer-scale MAPS bent into cylindrical half layers. To address these challenging requirements, the ALICE ITS3 project, in conjunction with the CERN EP R&D on monolithic pixel sensors, proposed the Tower Partners Semiconductor Co. 65 nm CMOS process as the starting point for the sensor. After the initial results confirmed the detection efficiency and radiation hardness, the choice of the technology was solidified by demonstrating the feasibility of operating MAPS in low-power consumption regimes, < 50 mW/cm(2), while maintaining high-quality performance. This was shown through a detailed characterisation of the Digital Pixel Test Structure (DPTS) prototype exposed to X-rays and ionising beams, and the results are presented in this article. Additionally, the sensor was further investigated through studies of the fake-hit rate, the linearity of the front-end in the range 1.7-28 keV, the performance after ionising irradiation, and the detection efficiency of inclined tracks in the range 0-45(degrees).

The production of ${K}^{*}{(892)}^{\ifmmode\pm\else\textpm\fi{}}$ meson resonance is measured at midrapidity ($|y|<0.5$) in $\mathrm{Pb}\text{\ensuremath{-}}\mathrm{Pb}$ collisions at $\sqrt{{s}_{NN}}=5.02$ TeV using the ALICE detector at the CERN Large Hadron Collider. The resonance is reconstructed via its hadronic decay channel ${K}^{*}{(892)}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{K}_{\mathrm{S}}^{0}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$. The transverse momentum distributions are obtained for various centrality intervals in the ${p}_{\mathrm{T}}$ range of $0.4\text{\ensuremath{-}}16 \mathrm{GeV}/c$. Measurements of integrated yields, mean transverse momenta, and particle yield ratios are reported and found to be consistent with previous ALICE measurements for ${K}^{*}{(892)}^{0}$ within uncertainties. The ${p}_{\mathrm{T}}$-integrated yield ratio $2\phantom{\rule{0.16em}{0ex}}{K}^{*}{(892)}^{\ifmmode\pm\else\textpm\fi{}}/({K}^{+}+{K}^{\ensuremath{-}}$) in central $\mathrm{Pb}\text{\ensuremath{-}}\mathrm{Pb}$ collisions shows a significant suppression at a level of $9.3\ensuremath{\sigma}$ relative to $pp$ collisions. Thermal model calculations result in an overprediction of the particle yield ratio. Although both hadron resonance gas in partial chemical equilibrium (HRG-PCE) and music $+$ smash simulations consider the hadronic phase, only HRG-PCE accurately represents the measurements, whereas music $+$ smash simulations tend to overpredict the particle yield ratio. These observations, along with the kinetic freeze-out temperatures extracted from the yields measured for light-flavored hadrons using the HRG-PCE model, indicate a finite hadronic phase lifetime, which decreases with increasing collision centrality percentile. The ${p}_{\mathrm{T}}$-differential yield ratios $2\phantom{\rule{0.16em}{0ex}}{K}^{*}{(892)}^{\ifmmode\pm\else\textpm\fi{}}/({K}^{+}+{K}^{\ensuremath{-}}$) and $2\phantom{\rule{0.16em}{0ex}}{K}^{*}{(892)}^{\ifmmode\pm\else\textpm\fi{}}/({\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}}$) are presented and compared with measurements in pp collisions at $\sqrt{s}=5.02$ TeV. Both particle ratios are found to be suppressed by up to a factor of five at ${p}_{\mathrm{T}}<2.0 \mathrm{GeV}/c$ in central $\mathrm{Pb}\text{\ensuremath{-}}\mathrm{Pb}$ collisions and are qualitatively consistent with expectations for rescattering effects in the hadronic phase. The nuclear modification factor (${R}_{\mathrm{AA}}$) shows a smooth evolution with centrality and is found to be below unity at ${p}_{\mathrm{T}}>8 \mathrm{GeV}/c$, consistent with measurements for other light-flavored hadrons. The smallest values are observed in most central collisions, indicating larger energy loss of partons traversing the dense medium.

The first measurements of femtoscopic correlations with the particle pair combinations π±KS0 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. Source 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 in the π±KS0 system is modeled through a resonant scattering amplitude, defined in terms of a mass and a coupling parameter, 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 increase 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 of the form (q1,q2‾,q3,q3‾) in which q1, q2 and q3 indicate the flavor of the valence quarks of the π and KS0. This latter trend is also confirmed via a simple geometric model that assumes a tetraquark structure of the K⁎0⁎(700) resonance.

The production of prompt $\mathrm {\Lambda_{c}^{+}}$ baryons has been measured at midrapidity in the transverse momentum interval $0

Position-resolved timing characterisation tests were performed on individual pixels of hexagonal and trench 3D silicon sensors. An IR laser was used to deposit energy equivalent to 1 MIP with a 1 & mu;m spatial resolution onto each sensor, which were attached to custom-designed fast read-out electronics chips. Time of Arrival (ToA) values obtained were (544 & PLUSMN; 29.8) ps for the hexagonal geometry, and (515 & PLUSMN; 8.2) ps for the trench geometry.

The ALICE ITS3 (Inner Tracking System 3) upgrade project and the CERN EP R&D on monolithic pixel sensors are investigating the feasibility of the Tower Partners Semiconductor Co. 65 nm process for use in the next generation of vertex detectors. The ITS3 aims to employ wafer-scale Monolithic Active Pixel Sensors thinned down to 20 to 40 um and bent to form truly cylindrical half barrels. Among the first critical steps towards the realisation of this detector is to validate the sensor technology through extensive characterisation both in the laboratory and with in-beam measurements. The Digital Pixel Test Structure (DPTS) is one of the prototypes produced in the first sensor submission in this technology and has undergone a systematic measurement campaign whose details are presented in this article. The results confirm the goals of detection efficiency and non-ionising and ionising radiation hardness up to the expected levels for ALICE ITS3 and also demonstrate operation at +20 C and a detection efficiency of 99% for a DPTS irradiated with a dose of $10^{15}$ 1 MeV n$_{\mathrm{eq}}/$cm$^2$. Furthermore, spatial, timing and energy resolutions were measured at various settings and irradiation levels.

AbstractA newly developed observable for correlations between symmetry planes, which characterize the direction of the anisotropic emission of produced particles, is measured in Pb–Pb collisions at $$\sqrt{s_\text {NN}}$$ s NN = 2.76 TeV with ALICE. This so-called Gaussian Estimator allows for the first time the study of these quantities without the influence of correlations between different flow amplitudes. The centrality dependence of various correlations between two, three and four symmetry planes is presented. The ordering of magnitude between these symmetry plane correlations is discussed and the results of the Gaussian Estimator are compared with measurements of previously used estimators. The results utilizing the new estimator lead to significantly smaller correlations than reported by studies using the Scalar Product method. Furthermore, the obtained symmetry plane correlations are compared to state-of-the-art hydrodynamic model calculations for the evolution of heavy-ion collisions. While the model predictions provide a qualitative description of the data, quantitative agreement is not always observed, particularly for correlators with significant non-linear response of the medium to initial state anisotropies of the collision system. As these results provide unique and independent information, their usage in future Bayesian analysis can further constrain our knowledge on the properties of the QCD matter produced in ultrarelativistic heavy-ion collisions.

Understanding the role of parton mass and Casimir color factors in the quantum chromodynamics parton shower represents an important step in characterizing the emission properties of heavy quarks. Recent experimental advances in jet substructure techniques have provided the opportunity to isolate and characterize gluon emissions from heavy quarks. In this Letter, the first direct experimental constraint on the charm-quark splitting function is presented, obtained via the measurement of the groomed shared momentum fraction of the first splitting in charm jets, tagged by a reconstructed D0 meson. The measurement is made in proton-proton collisions at s=13 TeV, in the low jet transverse-momentum interval of 15≤pTjet ch<30 GeV/c where the emission properties are sensitive to parton mass effects. In addition, the opening angle of the first perturbative emission of the charm quark, as well as the number of perturbative emissions it undergoes, is reported. Comparisons to measurements of an inclusive-jet sample show a steeper splitting function for charm quarks compared with gluons and light quarks. Charm quarks also undergo fewer perturbative emissions in the parton shower, with a reduced probability of large-angle emissions.Received 25 August 2022Revised 13 January 2023Accepted 19 July 2023DOI:https://doi.org/10.1103/PhysRevLett.131.192301Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.© 2023 CERN, for the ALICE CollaborationPhysics Subject Headings (PhySH)Research AreasQuark & gluon jetsNuclear Physics

A bstract The production of strange hadrons ( $$ {\textrm{K}}_{\textrm{S}}^0 $$ K S 0 , Λ, Ξ ± , and Ω ± ), baryon-to-meson ratios (Λ / $$ {\textrm{K}}_{\textrm{S}}^0 $$ K S 0 , Ξ / $$ {\textrm{K}}_{\textrm{S}}^0 $$ K S 0 , and Ω / $$ {\textrm{K}}_{\textrm{S}}^0 $$ K S 0 ), and baryon-to-baryon ratios (Ξ / Λ, Ω / Λ, and Ω / Ξ) associated with jets and the underlying event were measured as a function of transverse momentum ( p T ) in pp collisions at $$ \sqrt{s} $$ s = 13 TeV and p Pb collisions at $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 5 . 02 TeV with the ALICE detector at the LHC. The inclusive production of the same particle species and the corresponding ratios are also reported. The production of multi-strange hadrons, Ξ ± and Ω ± , and their associated particle ratios in jets and in the underlying event are measured for the first time. In both pp and p–Pb collisions, the baryon-to-meson and baryon-to-baryon yield ratios measured in jets differ from the inclusive particle production for low and intermediate hadron p T (0.6–6 GeV/ c ). Ratios measured in the underlying event are in turn similar to those measured for inclusive particle production. In pp collisions, the particle production in jets is compared with P ythia 8 predictions with three colour-reconnection implementation modes. None of them fully reproduces the data in the measured hadron p T region. The maximum deviation is observed for Ξ ± and Ω ± which reaches a factor of about six. The event multiplicity dependence is further investigated in p−Pb collisions. In contrast to what is observed in the underlying event, there is no significant event-multiplicity dependence for particle production in jets. The presented measurements provide novel constraints on hadronisation and its Monte Carlo description. In particular, they demonstrate that the fragmentation of jets alone is insufficient to describe the strange and multi-strange particle production in hadronic collisions at LHC energies.

AbstractThe elliptic flow $$(v_2)$$ ( v 2 ) of $${\textrm{D}}^{0}$$ D 0 mesons from beauty-hadron decays (non-prompt $${\textrm{D}}^{0})$$ D 0 ) was measured in midcentral (30–50%) Pb–Pb collisions at a centre-of-mass energy per nucleon pair $$\sqrt{s_{\textrm{NN}}} = 5.02$$ s NN = 5.02 TeV with the ALICE detector at the LHC. The $${\textrm{D}}^{0}$$ D 0 mesons were reconstructed at midrapidity $$(|y|<0.8)$$ ( | y | < 0.8 ) from their hadronic decay $$\mathrm {D^0 \rightarrow K^-\uppi ^+}$$ D 0 → K - π + , in the transverse momentum interval $$2< p_{\textrm{T}} < 12$$ 2 < p T < 12 GeV/c. The result indicates a positive $$v_2$$ v 2 for non-prompt $${{\textrm{D}}^{0}}$$ D 0 mesons with a significance of 2.7$$\sigma $$ σ . The non-prompt $${{\textrm{D}}^{0}}$$ D 0 -meson $$v_2$$ v 2 is lower than that of prompt non-strange D mesons with 3.2$$\sigma $$ σ significance in $$2< p_\textrm{T} < 8~\textrm{GeV}/c$$ 2 < p T < 8 GeV / c , and compatible with the $$v_2$$ v 2 of beauty-decay electrons. Theoretical calculations of beauty-quark transport in a hydrodynamically expanding medium describe the measurement within uncertainties.

AbstractTwo-particle correlations with $$\textrm{K}^{0}_\mathrm{{S}}$$ K S 0 , $$\Lambda $$ Λ /$$\overline{\Lambda }$$ Λ ¯ , and charged hadrons as trigger particles in the transverse momentum range $$8{<}p_{{\textrm{T}},{\textrm{trig}}}{<}16$$ 8 < p T , trig < 16 GeV/$$c$$ c , and associated charged particles within $$1{<}p_{{\textrm{T}},{\textrm{assoc}}}{<}8$$ 1 < p T , assoc < 8 GeV/$$c$$ c , are studied at midrapidity in pp and central Pb–Pb collisions at a centre-of-mass energy per nucleon–nucleon collision $$\sqrt{s_{\textrm{NN}}}~=~5.02$$ s NN = 5.02 TeV with the ALICE detector at the LHC. After subtracting the contributions of the flow background, the per-trigger yields are extracted on both the near and away sides, and the ratio in Pb–Pb collisions with respect to pp collisions ($$I_{\textrm{AA}}$$ I AA ) is computed. The per-trigger yield in Pb–Pb collisions on the away side is strongly suppressed to the level of $$I_{\textrm{AA}}$$ I AA $$\approx 0.6$$ ≈ 0.6 for $$p_{{\textrm{T}},{\textrm{assoc}}}>3$$ p T , assoc > 3 GeV/$$c$$ c as expected from strong in-medium energy loss, while an enhancement develops at low $$p_{{\textrm{T}},{\textrm{assoc}}}$$ p T , assoc on both the near and away sides, reaching $$I_{\textrm{AA}}$$ I AA $$\approx 1.8$$ ≈ 1.8 and 2.7 respectively. These findings are in good agreement with previous ALICE measurements from two-particle correlations triggered by neutral pions ($$\pi ^{0}$$ π 0 –h) and charged hadrons (h–h) in Pb–Pb collisions at $$\sqrt{s_{\textrm{NN}}}~=~2.76$$ s NN = 2.76 TeV. Moreover, the correlations with $$\textrm{K}^{0}_\mathrm{{S}}$$ K S 0 mesons and $$\Lambda $$ Λ /$$\overline{\Lambda }$$ Λ ¯ baryons as trigger particles are compared to those of inclusive charged hadrons. The results are compared with the predictions of Monte Carlo models.

The first measurements of skewness and kurtosis of mean transverse momentum ($\langle p_\mathrm{T}\rangle$) fluctuations are reported in Pb$-$Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV, Xe$-$Xe collisions at $\sqrt{s_\mathrm{NN}}$ $=$ 5.44 TeV and pp collisions at $\sqrt{s} = 5.02$ TeV using the ALICE detector. The measurements are carried out as a function of system size $\langle \mathrm{d}N_\mathrm{ch}/\mathrm{d}\eta\rangle_{|\eta|<0.5}^{1/3}$, using charged particles with transverse momentum ($p_\mathrm{T}$) and pseudorapidity ($\eta$), in the range $0.2 < p_\mathrm{T} < 3.0$ GeV/$c$ and $|\eta| < 0.8$, respectively. In Pb$-$Pb and Xe$-$Xe collisions, positive skewness is observed in the fluctuations of $\langle p_\mathrm{T}\rangle$ for all centralities, which is significantly larger than what would be expected in the scenario of independent particle emission. This positive skewness is considered a crucial consequence of the hydrodynamic evolution of the hot and dense nuclear matter created in heavy-ion collisions. Furthermore, similar observations of positive skewness for minimum bias pp collisions are also reported here. Kurtosis of $\langle p_\mathrm{T}\rangle$ fluctuations is found to be in good agreement with the kurtosis of Gaussian distribution, for most central Pb$-$Pb collisions. Hydrodynamic model calculations with MUSIC using Monte Carlo Glauber initial conditions are able to explain the measurements of both skewness and kurtosis qualitatively from semicentral to central collisions in Pb--Pb system. Color reconnection mechanism in PYTHIA8 model seems to play a pivotal role in capturing the qualitative behavior of the same measurements in pp collisions.

The dependence of $\mathrm{f}_{0}$(980) production on the final-state charged-particle multiplicity in p$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV is reported. The production of $\mathrm{f}_{0}$(980) is measured with the ALICE detector via the $\mathrm{f}_0 (980) \rightarrow \pi^{+}\pi^{-}$ decay channel in a midrapidity region of $-0.5

In this work the initial performance studies of the first small monolithic pixel sensors dedicated to charged particle detection, called CE-65, fabricated in the 65nm TowerJazz Panasonic Semiconductor Company are presented. The tested prototypes comprise matrices of 64 x 32 square analogue-output pixels with a pitch of 15 mu m. Different pixel types explore several sensing node geometries and amplification schemes, which allows for various biasing voltage of the detection layer and hence depletion conditions and electric field shaping. Laboratory tests conducted with a Fe-55 source demonstrated that the CE-65 sensors reach equivalent noise charge in the 15 to 25 e(-) range and excellent charge collection efficiencies. Charge sharing is substantial for standard diodes, but can be largely suppressed by modifying their design. Depletion of the thin sensitive layer saturates at a reverse diode bias of about 5 V.

Next generation of experiments at the future high luminosity particle colliders will require innovative detectors to correctly reconstruct the many interactions occurring at each bunch crossing. The LHC experiments have shown that the addition of track timing measurements with an accuracy of the order of tens of picoseconds per track will restore tracking and vertexing capabilities at today levels. In the last three years the TimeSPOT collaboration has been developing 3D trench-based silicon pixel sensors with a time resolution better than 20 ps for minimum ionizing particles. Many of the sensors designed have been tested in laboratory, both with a laser-based setup, able to precisely measure the sensor response throughout its active area, and with radioactive sources, emulating a beam test setup in the more controlled laboratory environment. In this contribution we will show that the 3D trench-based pixel design allows to reach time resolutions better than 20 ps, in contrast to what can be obtained with more traditional 3D columnar designs. A preliminary comparison between 3D trench-based silicon sensors with a different pitch size is presented.

In the last years, high-resolution time tagging has emerged as the tool to tackle the problem of high-track density in the detectors of the next generation of experiments at particle colliders. Time resolutions below 50ps and event average repetition rates of tens of MHz on sensor pixels having a pitch of 50$\mu$m are typical minimum requirements. This poses an important scientific and technological challenge on the development of particle sensors and processing electronics. The TIMESPOT initiative (which stands for TIME and SPace real-time Operating Tracker) aims at the development of a full prototype detection system suitable for the particle trackers of the next-to-come particle physics experiments. This paper describes the results obtained on the first batch of TIMESPOT silicon sensors, based on a novel 3D MEMS (micro electro-mechanical systems) design. Following this approach, the performance of other ongoing silicon sensor developments has been matched and overcome, while using a technology which is known to be robust against radiation degradation. A time resolution of the order of 20ps has been measured at room temperature suggesting also possible improvements after further optimisations of the front-end electronics processing stage.

In the last years, and in particular in view of the next generation of experiments at the future high luminosity particle colliders, the need of new tracking detectors with enhanced timing capabilities has strongly emerged, as these detectors will permit a proper reconstruction of tracks and vertices in events where a very large number of particles is present. Some LHC experiments, in view of their future upgrades, are considering as appropriate for their vertex detectors silicon pixel sensors with time resolutions in the range from 10 to 50 picoseconds. Such detectors are starting to become available as the result of many R&D projects around the world. However the laboratory testing tools to precisely characterize these devices are not always adequate for this purpose, often lacking in accuracy in both the space and time domain. In this paper we will describe a new laboratory setup based on an ultra-short pulse duration, 1030 nm wavelength, laser-based light source able to emulate the energy deposit of charged particles inside a silicon detector and all the ancillary equipment used to precisely measure their space and time performance.

In the next generation of experiments at the future high luminosity particle colliders, the identification of the interaction and decay vertices will be an extremely difficult task because of the very large number of particles that will be produced at each bunch crossing. LHC experiments have shown that new vertex detectors with single-hit time resolutions of the order of 10 ps will allow to recover the current tracking and vertexing capabilities. The TimeSPOT project is developing 3D trench-based silicon pixel detectors with a time resolution below 30 ps. Initial beam test with a first sensors batch has showed that these detectors fulfill and even exceed these expectations. To carefully study their performances and optimize their design, it is important to precisely measure sensors time response over their active area. This paper summarize the preliminary measurements of this sensors developed within the TimeSPOT project performed in our laboratory, using a custom laser-based setup to deposit a known energy in specific regions of the pixel sensitive volume, allowing us to estimate the performances of these sensors under charge-particle illumination.

Colloidal semiconductor nanocrystals are promising materials for applications in solution-processable optoelectronic devices including light-emitting diodes, photodetectors, photocatalysts and photovoltaic cells. Chemical synthesis enables refined control over dimension and shape of nanocrystals, allowing for unique functionalities and novel physical properties.

Room temperature optically pumped lasing is achieved for a new n-type molecular crystal of 2,5-bis(4′-cyanobiphenyl-4-yl)­thiophene (BP1T-CN). Efficient stimulated emission in the Fabry–Pérot crystal cavity is supported with a high group refractive index (4.18–4.98), Q factor (910–1860), material gain coefficient (120 cm-1), and a high stimulated emission rate demonstrated by pump–probe measurements.