arXiv subjects

G. Paic

Publications and source records attributed to G. Paic.

18 recordsLinked to original sources

arXiv2026

Development of a novel compact and fast SiPM-based RICH detector for the future ALICE 3 PID system at LHC

A dedicated R\&D is ongoing for the charged particle identification system of the \mbox{ALICE 3} experiment proposed for the LHC Run 5 and beyond. One of the subsystems for the high-energy charged particle identification will be a Ring-Imaging Cherenkov (RICH) detector. The possibility of integrating Cherenkov-based charged particle timing measurements is currently under study. The proposed system is based on a proximity-focusing RICH configuration including an aerogel radiator separated from a SiPM array layer by an expansion gap. A thin high-refractive index window of transparent material, acting as a second Cherenkov radiator, is glued on the SiPM array to enable time-of-flight measurements of charged particles by exploiting the yield of Cherenkov photons in the thin window. We assembled a small-scale prototype instrumented with different Hamamatsu SiPM array sensors with pitches ranging from 1 to 3 mm, readout by custom boards equipped with the front-end Petiroc 2A ASICs to measure charges and times. The primary Cherenkov radiator consisted of a 2 cm thick aerogel tile, while various window materials, including SiO$_2$ and MgF$_2$, were used as secondary Cherenkov radiators. The prototype was successfully tested in a campaign at the CERN PS T10 beam line with pions and protons. This paper summarizes the results achieved in the 2023 test beam campaign.

physics.ins-det↗

arXiv2026

Beam test studies for a SiPM-based RICH detector prototype for the future ALICE~3 experiment

The ALICE Collaboration is proposing a completely new apparatus, ALICE~3, for the LHC Runs~5 and beyond. In this context, a key subsystem for high-energy charged particle identification will be a proximity-focusing ring-imaging Cherenkov detector using aerogel as radiator and silicon photomultipliers (SiPMs) as photon sensors. We assembled a small-scale prototype instrumented with Hamamatsu S13352 and S13361-3075AE-08 SiPM arrays, readout by custom boards equipped with front-end Petiroc 2A ASICs. The Cherenkov radiator consisted of a 2 cm thick hydrophobic aerogel tile with a refractive index of 1.03 separated from the SiPM plane by a 23 cm expansion gap. The prototype was successfully tested in a campaign at the CERN PS T10 beam line with the goal of validating the design bRICH specifications in terms to achieve the target separation power. We measured a single photon angular resolution of 3.8~mrad at the Cherenkov angle saturation value of 242~mrad, as well as the expected scaling of the angular resolution with the increasing number of detected photons. We also studied the contribution of uncorrelated and correlated background sources with respect to the signal and proved the effectiveness of time matching between charged tracks and photon hits to achieve efficient suppression of the SiPM dark count rate background. In this paper, the detector concept, the description of the tested prototype layout and the main beam test results are reported.

physics.ins-det↗

arXiv2013

A Very High Momentum Particle Identification Detector

The construction of a new detector is proposed to extend the capabilities of ALICE in the high transverse momentum (pT) region. This Very High Momentum Particle Identification Detector (VHMPID) performs charged hadron identification on a track-by-track basis in the 5 GeV/c < p < 25 GeV/c momentum range and provides ALICE with new opportunities to study parton-medium interactions at LHC energies. The VHMPID covers up to 30% of the ALICE central barrel and presents sufficient acceptance for triggered- and tagged-jet studies, allowing for the first time identified charged hadron measurements in jets. This Letter of Intent summarizes the physics motivations for such a detector as well as its layout and integration into ALICE.

nucl-ex↗

arXiv2011

First observation of Cherenkov rings with a large area CsI-TGEM-based RICH prototype

We have built a RICH detector prototype consisting of a liquid C6F14 radiator and six triple Thick Gaseous Electron Multipliers (TGEMs), each of them having an active area of 10x10 cm2. One triple TGEM has been placed behind the liquid radiator in order to detect the beam particles, whereas the other five have been positioned around the central one at a distance to collect the Cherenkov photons. The upstream electrode of each of the TGEM stacks has been coated with a 0.4 micron thick CsI layer. In this paper, we will present the results from a series of laboratory tests with this prototype carried out using UV light, 6 keV photons from 55Fe and electrons from 90Sr as well as recent results of tests with a beam of charged pions where for the first time Cherenkov Ring images have been successfully recorded with TGEM photodetectors. The achieved results prove the feasibility of building a large area Cherenkov detector consisting of a matrix of TGEMs.

physics.ins-det↗

arXiv2011

The broad away side of azimuthal correlations: 3 vs 2 final state particles in high energy nuclear collisions

In high energy heavy ion collisions at RHIC there are important aspects of the medium induced dynamics, that are still not well understood. In particular, there is a broadening and even a double hump structure of the away-side peak appearing in azimuthal correlation studies in Au+Au collisions which is absent in p+p collisions at the same energies. These features are already present but suppressed in p+p collisions: 2 to 3 parton processes produce such structures but are suppressed with respect to 2 to 2 processes. We argue that in A+A collisions the different geometry for the trajectories of 3 as opposed to 2 particles in the final state, together with the medium induced energy loss effects on the different cross sections, create a scenario that enhances processes with 3 particles in the final state, which gives on average this double hump structure.

nucl-th↗

arXiv2010

R&D results on a CsI-TTGEM based photodetector

The very high momentum particle identification detector proposed for the ALICE upgrade is a focusing RICH using a C4F10 gaseous radiator. For the detection of Cherenkov photons, one of the options currently under investigation is to use a CsI coated Triple-Thick-GEM (CsI-TTGEM) with metallic or resistive electrodes. We will present results from the laboratory studies as well as preliminary results of beam tests of a RICH detector prototype consisting of a CaF2 radiator coupled to a 10x10 cm2 CsI-TTGEM equipped with a pad readout and GASSIPLEX-based front-end electronics. With such a prototype the detection of Cherenkov photons simultaneously with minimum ionizing particles has been achieved for the first time in a stable operation mode.

physics.ins-det↗

arXiv2010

Sensitivity of the parameters measured in pp collisions on the gluon PDF

The sphericity distribution in minimum bias events obtained with PYTHIA event generator, incorporating different parton distribution functions is presented. The results show that for minimum bias pp collisions the sphericity distribution for different parameters like the mean transverse momentum and multiplicity exhibit strong sensitivity on the parton distribution function used. The results indicate that early data at the LHC could be used in this type of analysis to fix the gluon distribution function in the proton.

hep-ph↗

arXiv2009

Three and two-hadron correlations in \sqrt{s_{NN}}=200 GeV proton-proton and nucleus-nucleus collisions

We compare the azimuthal correlations arising from three and two hadron production in high energy proton-proton and nucleus-nucleus collisions at \sqrt{s_{NN}}=200 GeV, using the leading order matrix elements for two-to-three and two-to-two parton-processes in perturbative QCD. We first compute the two and three hadron production cross sections in mid-rapidity proton-proton collisions. Then we consider Au + Au collisions including parton energy loss using the modified fragmentation function approach. By examining the geometrical paths the hard partons follow through the medium, we show that the two away-side partons produced in two-to-three processes have in average a smaller and a greater path length than the average path length of the away-side parton in two-to-two processes. Therefore there is a large probability that in the former processes one of the particles escapes while the other gets absorbed. This effect leads to an enhancement in the azimuthal correlations of the two-to-three with respect to the two-to-two parton-processes when comparing to the same processes in proton-proton collisions since in average the particle with the shortest path length looses less energy with respect to the away side particle in two-to-two processes. We argue that this phenomenon may be responsible for the shape of the away-side in azimuthal correlations observed in mid-rapidity Au + Au collisions at RHIC.

nucl-th↗

arXiv2009

What we have (not)learned from the ultrarelativistic heavy ion collisions

The field of ultrarelativistic heavy ion collisions is today a flourishing activity both on the experimental and on the theoretical side. Although the theoretical justifications to study these collisions was given already more than three decades ago and the experimental studies have a history of more than 25 years we are still very much in the dark as to the details of the processes and of the characteristics of the matter created in collisions. Increasing the energy of collisions has brought new insights but has also resulted with new challenges. In the present paper I will try from a personal perspective to report on the answers we have collected and on the problems we are faced with. The account is partial, taking into account that it is impossible to render justice to every aspect of the field.

nucl-ex↗

arXiv2008

Photosensitive Strip RETHGEM

An innovative photosensitive gaseous detector, consisting of a GEM like amplification structure with double layered electrodes (instead of commonly used metallic ones) coated with a CsI reflective photocathode, is described. In one of our latest designs, the inner electrode consists of a metallic grid and the outer one is made of resistive strips; the latter are manufactured by a screen printing technology on the top of the metallic strips grid The inner metallic grid is used for 2D position measurements whereas the resistive layer provides an efficient spark protected operation at high gains - close to the breakdown limit. Detectors with active areas of 10cm x10cm and 10cm x20cm were tested under various conditions including the operation in photosensitive gas mixtures containing ethylferrocene or TMAE vapors. The new technique could have many applications requiring robust and reliable large area detectors for UV visualization, as for example, in Cherenkov imaging devices.

physics.ins-det↗

arXiv2007

Thermal Dileptons at LHC

We predict dilepton invariant-mass spectra for central 5.5 ATeV Pb-Pb collisions at LHC. Hadronic emission in the low-mass region is calculated using in-medium spectral functions of light vector mesons within hadronic many-body theory. In the intermediate-mass region thermal radiation from the Quark-Gluon Plasma, evaluated perturbatively with hard-thermal loop corrections, takes over. An important source over the entire mass range are decays of correlated open-charm hadrons, rendering the nuclear modification of charm and bottom spectra a critical ingredient.

hep-ph↗

arXiv2007

The current progress of the ALICE Ring Imaging Cherenkov Detector

Recently, the last two modules (out of seven) of the ALICE High Momentum Particle Identification detector (HMPID) were assembled and tested. The full detector, after a pre-commissioning phase, has been installed in the experimental area, inside the ALICE solenoid, at the end of September 2006. In this paper we review the status of the ALICE/HMPID project and we present a summary of the series production of the CsI photo-cathodes. We describe the key features of the production procedure which ensures high quality photo-cathodes as well as the results of the quality assessment performed by means of a specially developed 2D scanner system able to produce a detailed map of the CsI photo-current over the entire photo-cathode surface. Finally we present our recent R&D efforts toward the development of a novel generation of imaging Cherenkov detectors with the aim to identify, in heavy ions collisions, hadrons up to 30 GeV/c.

physics.ins-det↗

arXiv2006

ACORDE a Cosmic Ray Detector for ALICE

ACORDE is one of the ALICE detectors, presently under construction at CERN. It consists of an array of plastic scintillator counters placed on the three upper faces of the ALICE magnet. It will act as a cosmic ray trigger, and, together with other ALICE sub-detectors, will provide precise information on cosmic rays with primary energies around $10^{15} ÷10^{-17}$ eV. Here we describe the design review of ACORDE along with the present status and integration into ALICE.

physics.ins-det↗

arXiv2006

Proton/pion ratios and radial flow in pp and peripheral heavy ion collisions

The production of baryon and mesons in the RHIC heavy-ion experiments has received a lot of attention lately. Although not widely known, the pp data measured concurrently with heavy ion collisions do not find a convincing explanation in terms of simple models. We present the results of an afterburner to Pythia and Hijing event generators, simulating radial flow which seems to qualitatively explain the experimental results when applied to the pp collision data from RHIC at 200 GeV center-of-mass energy.

hep-ph↗

arXiv2006

Azimuthal Correlations in p-p collisions

We report the analysis of experimental azimuthal correlations measured by STAR in p-p collisions at $\sqrt{s_{NN}}$ = 200 GeV. We conclude that for a fit of data using Pythia event generator we need to include two values of $k_{T}$.

hep-ph↗

arXiv2005

Expression of Interest for a Comprehensive New Detector at RHIC II

There are compelling physics questions to be addressed by a new comprehensive detector at a future, high-luminosity RHIC II collider. These form the basis for this Expression of Interest. What precisely are the properties of the strongly-coupled Quark Gluon Plasma (sQGP)? Can a more weakly interacting QGP state be formed and investigated at RHIC? How do particles acquire mass and what is the effect of chiral symmetry restoration on hadronization in a dense medium? What is the chiral structure of the QCD vacuum and its influence on and contributions of different QCD vacuum states to the masses of particles? Is there another phase of matter at low Bjorken-x, i.e. the Color Glass Condensate (CGC)? If present, what are its features and how does it evolve into the QGP? If not, are parton distribution functions understood at low Bjorken-x and can they describe particle production? What are the structure and dynamics inside the proton, including parton spin and orbital angular momentum? What are the contributions of gluons and the QCD sea to the polarization of the proton? What is the flavor-dependence? Are there tests for new physics beyond the Standard Model from spin measurements at RHIC II (such as parity-violating interactions)? We propose that a new comprehensive detector system is needed for RHIC II to address these questions adequately and in an effective way.

nucl-ex↗

arXiv2004

Leading-particle suppression in high energy nucleus-nucleus collisions

Parton energy loss effects in heavy-ion collisions are studied with the Monte Carlo program PQM (Parton Quenching Model) constructed using the BDMPS quenching weights and a realistic collision geometry. The merit of the approach is that it contains only one free parameter that is tuned to the high-pt nuclear modification factor measured in central Au-Au collisions at sqrt{s_NN} = 200 GeV. Once tuned, the model is coherently applied to all the high-pt observables at 200 GeV: the centrality evolution of the nuclear modification factor, the suppression of the away-side jet-like correlations, and the azimuthal anisotropies for these observables. Predictions for the leading-particle suppression at nucleon-nucleon centre-of-mass energies of 62.4 and 5500 GeV are calculated. The limits of the eikonal approximation in the BDMPS approach, when applied to finite-energy partons, are discussed.

hep-ph↗

arXiv2002

Identification of High $\rm p_{\perp}$ Particles with the STAR-RICH Detector

The STAR-RICH detector extends the particle identification capapbilities of the STAR experiment for charged hadrons at mid-rapidity. This detector represents the first use of a proximity-focusing CsI-based RICH detector in a collider experiment. It provides identification of pions and kaons up to 3 GeV/c and protons up to 5 GeV/c. The characteristics and performance of the device in the inaugural RHIC run are described.

nucl-ex↗