A new Low Gain Avalanche Diode concept: the double-LGAD

This paper describes the new concept of the double-LGAD. The goal is to increase the charge at the input of the electronics, keeping a time resolution equal or better than a standard (single) LGAD; this has been realized by adding the charges of two coupled LGADs while still using a single front-end electronics. The study here reported has been done starting from single LGAD with a thickness of 25 \textmu{m}, 35 \textmu{m} and 50 \textmu{m}.Comment: arXiv admin note: text overlap with arXiv:2208.0571

First results on monolithic CMOS detector with internal gain

: In this paper we report on a set of characterisations carried out on the first monolithic LGAD prototype integrated in a customised 110 nm CMOS process having a depleted active volume thickness of 48 μm. This prototype is formed by a pixel array where each pixel has a total size of 100 μm × 250 μm and includes a high-speed front-end amplifier. After describing the sensor and the electronics architecture, both laboratory and in-beam measurements are reported and described. Optical characterisations performed with an IR pulsed laser setup have shown a sensor internal gain of about 2.5. With the same experimental setup, the electronic jitter was found to be between 50 ps and 150 ps, depending on the signal amplitude. Moreover, the analysis of a test beam performed at the Proton Synchrotron (PS) T10 facility of CERN with 10 GeV/c protons and pions indicated that the overall detector time resolution is in the range of 234 ps to 244 ps. Further TCAD investigations, based on the doping profile extracted from C(V) measurements, confirmed the multiplication gain measured on the test devices. Finally, TCAD simulations were used to tune the future doping concentration of the gain layer implant, targeting sensors with a higher avalanche gain. This adjustment is expected to enhance the timing performance of the sensors of the future productions, in order to cope with the high event rate expected in most of the near future high-energy and high-luminosity physics experiments, where the time resolution will be essential to disentangle overlapping events and it will also be crucial for Particle IDentification (PID

First results on monolithic CMOS detector with internal gain

In this paper we report on a set of characterisations carried out on the first monolithic LGAD prototype integrated in a customised 110 nm CMOS process having a depleted active volume thickness of 48 $\mu$m. This prototype is formed by a pixel array where each pixel has a total size of 100 $\mu$m $\times$ 250 $\mu$m and includes a high-speed front-end amplifier. After describing the sensor and the electronics architecture, both laboratory and in-beam measurements are reported and described. Optical characterisations performed with an IR pulsed laser setup have shown a sensor internal gain of about 2.5. With the same experimental setup, the electronic jitter was found to be between 50 ps and 150 ps, depending on the signal amplitude. Moreover, the analysis of a test beam performed at the Proton Synchrotron (PS) T10 facility of CERN with 10 GeV/c protons and pions indicated that the overall detector time resolution is in the range of 234 ps to 244 ps. Further TCAD investigations, based on the doping profile extracted from $C(V)$ measurements, confirmed the multiplication gain measured on the test devices. Finally, TCAD simulations were used to tune the future doping concentration of the gain layer implant, targeting sensors with a higher avalanche gain. This adjustment is expected to enhance the timing performance of the sensors of the future productions, in order to cope with the high event rate expected in most of the near future high-energy and high-luminosity physics experiments, where the time resolution will be essential to disentangle overlapping events and it will also be crucial for Particle IDentification (PID)

Direct detection of charged particles with SiPMs

The direct response of Silicon PhotoMultipliers being traversed by a MIP charged particle have been studied in a systematic way for the first time. Using beam test data, time resolution and the crosstalk probability have been measured. A characterization of the SiPM by means of a laser beam is also reported. The results obtained for different sensors indicate a measured time resolution around 40–70 ps. Although particles are expected to traverse only one SPAD per event, crosstalk measurements on different sensors indicate an unexpected higher value with respect to the one related to the sensor noise

Beam test results of 25 and 35 μ m thick FBK ultra-fast silicon detectors

This paper presents the measurements on first very thin Ultra-Fast Silicon Detectors (UFSDs) produced by Fondazione Bruno Kessler; the data have been collected in a beam test setup at the CERN PS, using beam with a momentum of 12 GeV/c. UFSDs with a nominal thickness of 25 and 35 mu m and an area of 1 x 1 mm(2) have been considered, together with an additional HPK 50-mu m thick sensor, taken as reference. Their timing performances have been studied as a function of the applied voltage and gain. A time resolution of about 25 ps and of 22 ps at a voltage of 120 and 240 V has been obtained for the 25 and 35 mu m thick UFSDs, respectively

Measurements of the Cherenkov effect in direct detection of charged particles with SiPMs

In this paper, different Silicon PhotoMultiplier (SiPM) sensors have been tested with charged particles to characterize the Cherenkov light produced in the sensor protection layer. A careful position scan of the SiPM response has been performed with different prototypes, confirming the large number of firing cells and proving almost full efficiency, with the SiPM filling factor essentially negligible. This study also allowed us to study the time resolution of such devices as a function of the number of firing cells, reaching values below 20 ps. These measurements provide significant insight into the capabilities of SiPM sensors in direct detection of charged particles and their potential for several applications

Measurements of the Cherenkov effect in direct detection of charged particles with SiPMs

In this paper, different Silicon PhotoMultiplier (SiPM) sensors have been tested with charged particles to characterize the Cherenkov light produced in the sensor protection layer. A careful position scan of the SiPM response has been performed with different prototypes, confirming the large number of firing cells and proving almost full efficiency, with the SiPM filling factor essentially negligible. This study also allowed us to study the time resolution of such devices as a function of the number of firing cells, reaching values below 20 ps. These measurements provide significant insight into the capabilities of SiPM sensors in direct detection of charged particles and their potential for several applications

Exploring the Strong Interaction of Three-Body Systems at the LHC

Deuterons are atomic nuclei composed of a neutron and a proton held together by the strong interaction. Unbound ensembles composed of a deuteron and a third nucleon have been investigated in the past using scattering experiments, and they constitute a fundamental reference in nuclear physics to constrain nuclear interactions and the properties of nuclei. In this work, \u1d43e+−\u1d451 and \u1d45d−\u1d451 femtoscopic correlations measured by the ALICE Collaboration in proton-proton (\u1d45d⁢\u1d45d) collisions at √\u1d460=13  TeV at the Large Hadron Collider (LHC) are presented. It is demonstrated that correlations in momentum space between deuterons and kaons or protons allow us to study three-hadron systems at distances comparable with the proton radius. The analysis of the \u1d43e+−\u1d451 correlation shows that the relative distances at which deuterons and protons or kaons are produced are around 2 fm. The analysis of the \u1d45d−\u1d451 correlation shows that only a full three-body calculation that accounts for the internal structure of the deuteron can explain the data. In particular, the sensitivity of the observable to the short-range part of the interaction is demonstrated. These results indicate that correlations involving light nuclei in \u1d45d⁢\u1d45d collisions at the LHC will also provide access to any three-body system in the strange and charm sectors

Charged-particle production as a function of the relative transverse activity classifier in pp, p-Pb, and Pb-Pb collisions at the LHC

Measurements of charged-particle production in pp, p–Pb, and Pb–Pb collisions in the toward, away, and transverse regions with the ALICE detector are discussed. These regions are defined event-by-event relative to the azimuthal direction of the charged trigger particle, which is the reconstructed particle with the largest transverse momentum pTtrig in the range 8 < 15 GeV/c. The toward and away regions contain the primary and recoil jets, respectively; both regions are accompanied by the underlying event (UE). In contrast, the transverse region perpendicular to the direction of the trigger particle is dominated by the so-called UE dynamics, and includes also contributions from initial- and final-state radiation. The relative transverse activity classifier, RT=NchT/NchT, is used to group events according to their UE activity, where NchT is the charged-particle multiplicity per event in the transverse region and NchT is the mean value over the whole analysed sample. The energy dependence of the RT distributions in pp collisions at s = 2.76, 5.02, 7, and 13 TeV is reported, exploring the Koba-Nielsen-Olesen (KNO) scaling properties of the multiplicity distributions. The first measurements of charged-particle pT spectra as a function of RT in the three azimuthal regions in pp, p–Pb, and Pb–Pb collisions at sNN = 5.02 TeV are also reported. Data are compared with predictions obtained from the event generators PYTHIA 8 and EPOS LHC. This set of measurements is expected to contribute to the understanding of the origin of collective-like effects in small collision systems (pp and p–Pb)

Multiplicity and event-scale dependent flow and jet fragmentation in pp collisions at √s=13 TeV and in p-Pb collisions at √sNN=5.02 TeV

Long- and short-range correlations for pairs of charged particles are studied via two-particle angular correlations in pp collisions at s = 13 TeV and p–Pb collisions at sNN = 5.02 TeV. The correlation functions are measured as a function of relative azimuthal angle ∆φ and pseudorapidity separation ∆η for pairs of primary charged particles within the pseudorapidity interval |η| < 0.9 and the transverse-momentum interval 1 < pT< 4 GeV/c. Flow coefficients are extracted for the long-range correlations (1.6 < |∆η| < 1.8) in various high-multiplicity event classes using the low-multiplicity template fit method. The method is used to subtract the enhanced yield of away-side jet fragments in high-multiplicity events. These results show decreasing flow signals toward lower multiplicity events. Furthermore, the flow coefficients for events with hard probes, such as jets or leading particles, do not exhibit any significant changes compared to those obtained from high-multiplicity events without any specific event selection criteria. The results are compared with hydrodynamic-model calculations, and it is found that a better understanding of the initial conditions is necessary to describe the results, particularly for low-multiplicity events