arXiv subjects

Alessandro Grelli

Publications and source records attributed to Alessandro Grelli.

7 recordsLinked to original sources

arXiv2025

Influence of Radiation and AC Coupling on Time Performance of Analog Pixels Test Structures in 65 nm CMOS technology

Monolithic Active Pixel Sensors (MAPS) in advanced CMOS imaging technologies are key to next-generation tracking systems for high-energy physics, where radiation hardness and precise vertex reconstruction are essential. As part of the ALICE ITS3 R&D program in synergy with the CERN R&D, we evaluated the performance of the Analog Pixel Test Structures (APTS) fabricated in the TPSCo 65 nm CMOS imaging process. The prototypes employ 10 um pitch pixels with a fast operational amplifier-based buffering stage at the output, enabling direct characterization of intrinsic sensor response. Beam tests with minimum ionizing particles assessed the timing and charge collection of DC- and AC-coupled designs, including devices exposed to 10^14 NIEL and 10^15 NIEL non ioninsing energy loss. DC-coupled sensors demonstrated stable performance, maintaining time resolution lower than 70 ps and >99% detection efficiency up to 10^15 NIEL. AC-coupled sensors demonstrated a wide operational margin, with efficiencies above 99% for clusterization thresholds below 150 electrons. Even though the AC coupling allows higher reverse bias than DC-coupled sensors, the reduced signal amplitude lowers the signal-to-noise ratio, increasing the jitter contribution. At high reverse bias, the AC-coupled sensors achieve time resolutions comparable to the DC-coupled version, demonstrating the viability of both approaches. These results also suggest that combining the low capacitance of DC-coupled designs with the high-bias capability of AC coupling could further enhance time resolution. These results confirm the suitability of 65 nm MAPS for future collider detectors requiring high radiation tolerance, efficiency, and timing precision.

physics.ins-det↗

arXiv2025

Yield, noise and timing studies of ALICE ITS3 stitched sensor test structures: the MOST

In the LHC long shutdown 3, the ALICE experiment upgrades the inner layers of its Inner Tracker System with three layers of wafer-scale stitched sensors bent around the beam pipe. Two stitched sensor evaluation structures, the MOnolithic Stitched Sensor (MOSS) and MOnolithic Stitched Sensor with Timing (MOST) allow the study of yield dependence on circuit density, power supply segmentation, stitching demonstration for power and data transmission, performance dependence on reverse bias, charge collection performance, parameter uniformity across the chip, and performance of wafer-scale data transmission. The MOST measures 25.9 cm x 0.25 cm, has more than 900,000 pixels of 18x18 $\mu$m$^2$ and emphasizes the validation of pixel circuitry with maximum density, together with a high number of power domains separated by switches allowing to disconnect faulty circuits. It employs 1 Gb/s 26 cm long data transmission using asynchronous, data-driven readout. This readout preserves information on pixel address, time of arrival and time over threshold. In the MOSS, by contrast, regions with different in-pixel densities are implemented to study yield dependence and are read synchronously. MOST test results validated the concept of power domain switching and the data transmission over 26 cm stitched lines which are to be employed on the full-size, full-functionality ITS3 prototype sensor, MOSAIX. Jitter of this transmission is still under study. This proceeding summarizes the performance of the stitched sensor test structures with emphasis on the MOST.

physics.ins-det↗

arXiv2017

ALICE Overview

An overview of the recent results obtained by the ALICE Collaboration from the analysis of the pp, p-Pb and Pb-Pb data samples collected during LHC run I and the first half of run II is presented.

hep-ex↗

arXiv2013

Heavy-flavour production in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV with the ALICE detector

Hadrons containing heavy-flavours, i.e. charm and beauty quarks, are unique probes of the properties of the hot and dense QCD medium produced in heavy-ion collisions. Due to their large masses, heavy quarks are produced at the initial stage of the collision, almost exclusively via hard partonic scattering processes. Therefore, they are expected to experience the full collision history propagating through and interacting with the QCD medium. The parton energy loss, which is sensitive to the transport coefficients of the produced medium, can be studied experimentally by measuring the nuclear modication factor ($R_{\rm AA}$) which accounts for the modication of the heavy-flavoured hadron yield in Pb-Pb collisions with respect to pp collisions. In semi-central Pb-Pb collisions, the degree of thermalization of charm quarks in the QCD medium can be accessed via the measurement of the heavy flavour elliptic flow $v_2$ at low $p_{\rm T}$ . At high $p_{\rm T}$, $v_2$ is sensitive to the path-length dependence of heavy quark in-medium energy loss. The ALICE collaboration has measured the production of open heavy flavour hadrons via their hadronic and semi-leptonic decays at mid-rapidity and in the semi-muonic decay channel at forward rapidity in pp, p-Pb and Pb-Pb collisions at 7, 5.02 and 2.76 TeV respectively. In this talk the current results on open heavy-flavour $R_{\rm AA}$ and $v_2$ will be presented.

hep-ex↗

arXiv2012

D meson nuclear modification factors in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV with the ALICE detector

The measurement of D meson production provides key tests for parton energy-loss models, which predict that charm quarks should experience less in-medium energy loss than light quarks and gluons. The ALICE experiment has measured the production of prompt D^(0), D^(+) and D^(*+) mesons in pp and Pb-Pb collisions at the LHC at sqrt(s) = 7 and 2.76 TeV and at sqrt(s_NN) = 2.76 TeV, respectively, via the exclusive reconstruction of their hadronic decay. The pT-differential production yields in the range 2 < pT < 16 GeV/c at central rapidity, |y| < 0.5, were used to calculate the nuclear modification factor. A suppression of a factor 3 to 4 for transverse momenta larger than 5 GeV/c in the 20% most central collisions was observed. Preliminary results in an extended pT-range, using the data sample collected during the 2011 Pb-Pb run, together with the first measurement of D^(+)_(s) nuclear modification factor will be shown.

hep-ex↗

arXiv2012

D meson nuclear modification factors in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV measured with the ALICE detector at the CERN-LHC

The properties of the hot and dense QCD medium formed in ultra-relativistic heavy ion collisions, as well as the mechanism of in-medium partonic energy loss, can be accessed via the study of the D mesons nuclear modification factor. The ALICE experiment has measured D meson production in pp and Pb-Pb collisions at the LHC at $\sqrt{s}$ =7 and 2.76 TeV and at $\sqrt{s_{NN}}$ = 2.76 TeV, respectively, via the exclusive reconstruction of hadronic decay channels. D mesons are selected by exploiting the high-resolution tracking performance and the hadron identification capabilities of the ALICE detectors. In this contribution we report on the analyses of the D$^0\rightarrow $K$^-π^+$, the D$^+ \rightarrow $K$^- π^+ π^+$ and the D$^{*+}\rightarrow $D$^0 π^+$ channels. The preliminary results on D mesons nuclear modification factors are presented.

nucl-ex↗

arXiv2009

Heavy flavour production at LHC

The Large Hadron Collider (LHC) will open a new era in high energy physics. The expected large cross section for heavy flavour production in proton-proton collisions at $\sqrt{s}$ = 14 TeV will allow detailed studies of the production mechanisms and an extensive test of Quantum Chromodynamics. Since charm and beauty has been proposed as a good probe to study hot and dense QCD matter, the understanding of the production mechanisms in elementary proton-proton collisions is of primary importance as a reference for studies in heavy-ion collisions. In the early phase of LHC operation the experiments will focus on the investigation of the heavy flavour production mechanisms.

hep-ex↗