arXiv subjects

S. Parsa

Publications and source records attributed to S. Parsa.

16 recordsLinked to original sources

arXiv2025

Cosmic Ray Measurements Using Charge and Light Readout in a Pixelated Liquid Argon Time Projection Chamber

Liquid argon time projection chambers have emerged as a competitive technology for detecting solar neutrinos. The SoLAr collaboration was formed to explore argon detectors with pixelated light and charge readout, aiming for high detection efficiency and improved energy resolution. Building on the success of an initial prototype, we present results obtained with a second SoLAr prototype (V2), a $30 \times 30 \times 30$ cm$^{3}$ time projection chamber operated in a cryostat containing several hundred kilograms of liquid argon. We report measurements of cosmic-ray muons using both tracking and calorimetry from light and charge sensors, and we highlight the improved performance achieved through combined charge and light reconstruction. These results demonstrate the promise of dual-readout detectors and motivate future prototyping efforts toward kiloton-scale facilities.

physics.ins-det↗

arXiv2025

HARMONI: Haptic-Guided Assistance for Unified Robotic Tele-Manipulation and Tele-Navigation

Shared control, which combines human expertise with autonomous assistance, is critical for effective teleoperation in complex environments. While recent advances in haptic-guided teleoperation have shown promise, they are often limited to simplified tasks involving 6- or 7-DoF manipulators and rely on separate control strategies for navigation and manipulation. This increases both cognitive load and operational overhead. In this paper, we present a unified tele-mobile manipulation framework that leverages haptic-guided shared control. The system integrates a 9-DoF follower mobile manipulator and a 7-DoF leader robotic arm, enabling seamless transitions between tele-navigation and tele-manipulation through real-time haptic feedback. A user study with 20 participants under real-world conditions demonstrates that our framework significantly improves task accuracy and efficiency without increasing cognitive load. These findings highlight the potential of haptic-guided shared control for enhancing operator performance in demanding teleoperation scenarios.

cs.RO↗

arXiv2024

Characterization of the optical model of the T2K 3D segmented plastic scintillator detector

The magnetised near detector (ND280) of the T2K long-baseline neutrino oscillation experiment has been recently upgraded aiming to satisfy the requirement of reducing the systematic uncertainty from measuring the neutrinonucleus interaction cross section, which is the largest systematic uncertainty in the search for leptonic charge-parity symmetry violation. A key component of the upgrade is SuperFGD, a 3D segmented plastic scintillator detector made of approximately 2,000,000 optically-isolated 1 cm3 cubes. It will provide a 3D image of GeV neutrino interactions by combining tracking and stopping power measurements of final state particles with sub-nanosecond time resolution. The performance of SuperFGD is characterized by the precision of its response to charged particles as well as the systematic effects that might affect the physics measurements. Hence, a detailed Geant4 based optical simulation of the SuperFGD building block, i.e. a plastic scintillating cube read out by three wavelength shifting fibers, has been developed and validated with the different datasets collected in various beam tests. In this manuscript the description of the optical model as well as the comparison with data are reported.

hep-ex↗

arXiv2024

First Demonstration of a Combined Light and Charge Pixel Readout on the Anode Plane of a LArTPC

The novel SoLAr concept aims to extend sensitivities of liquid-argon neutrino detectors down to the MeV scale for next-generation detectors. SoLAr plans to accomplish this with a liquid-argon time projection chamber that employs an anode plane with dual charge and light readout, which enables precision matching of light and charge signals for data acquisition and reconstruction purposes. We present the results of a first demonstration of the SoLAr detector concept with a small-scale prototype detector integrating a pixel-based charge readout and silicon photomultipliers on a shared printed circuit board. We discuss the design of the prototype, and its operation and performance, highlighting the capability of such a detector design.

physics.ins-det↗

arXiv2022

SuperFGD prototype time resolution studies

The SuperFGD will be a part of the ND280 near detector of the T2K and Hyper Kamiokande projects, that will help to reduce systematic uncertainties related with neutrino flux and cross-section modeling. The upgraded ND280 will be able to perform a full exclusive reconstruction of the final state from neutrino-nucleus interactions, including measurements of low momentum protons, pions and, for the first time, event-by event measurements of neutron kinematics. The time resolution defines the neutron energy resolution. We present the results of time resolution measurements made with the SuperFGD prototype that consists of 9216 plastic scintillator cubes (cube size is 1 cm$^3$) readout with 1728 wavelength-shifting fibers going along three orthogonal directions. We use data from the muon beam exposure at CERN. The time resolution of 0.97 ns was obtained for one readout channel after implementing the time calibration with a correction for the time-walk effect. The time resolution improves with energy deposited in a scintillator cube. Averaging two readout channels for one scintillator cube improves the time resolution to 0.68 ns which means that signals in different channels are not synchronous. Therefore the contribution from the time recording step of 2.5 ns is averaged as well. Averaging time values from N channels improves the time resolution by $\sim 1/\sqrt{N}$. Therefore a very good time resolution should be achievable for neutrons since neutron recoils hit typically several scintillator cubes and in addition produce larger amplitudes than muons. Measurements performed with a laser and a wide-bandwidth oscilloscope demonstrated that the time resolution obtained with the muon beam is not far from its expected limit. The intrinsic time resolution of one channel is 0.67 ns for signals of 56 photo-electron typical for minimum ionizing particles.

physics.ins-det↗

arXiv2020

The SuperFGD Prototype Charged Particle Beam Tests

A novel scintillator detector, the SuperFGD, has been selected as the main neutrino target for an upgrade of the T2K experiment ND280 near detector. The detector design will allow nearly 4π coverage for neutrino interactions at the near detector and will provide lower energy thresholds, significantly reducing systematic errors for the experiment. The SuperFGD is made of optically-isolated scintillator cubes of size 10x10x10 mm^3, providing the required spatial and energy resolution to reduce systematic uncertainties for future T2K runs. The SuperFGD for T2K will have close to two million cubes in a 1920x560x1840 mm^3 volume. A prototype made of 24x8x48 cubes was tested at a charged particle beamline at the CERN PS facility. The SuperFGD Prototype was instrumented with readout electronics similar to the future implementation for T2K. Results on electronics and detector response are reported in this paper, along with a discussion of the 3D reconstruction capabilities of this type of detector. Several physics analyses with the prototype data are also discussed, including a study of stopping protons.

physics.ins-det↗

arXiv2020

On embeddability of joins and their `factors'

We present a short and clear proof of the following particular case of a 2006 result of Melikhov-Schepin: Let $K$ be a $k$-dimensional simplicial complex and $K*[3]$ the union of three cones over $K$ along their common bases. If $2d\ge3k+3$ and $K*[3]$ embeds into $\mathbb R^{d+2}$, then $K$ embeds into $\mathbb R^d$. We also present a generalization of this theorem. The proofs are based on the Haefliger-Weber `configuration spaces' embeddability criterion, equivariant suspension theorem and simple properties of joins and cones.

math.GT↗

arXiv2018

On the faint-end of the galaxy luminosity function in the Epoch of Reionization: updated constraints from the HST Frontier Fields

Ultra-faint galaxies are hosted by small dark matter halos with shallow gravitational potential wells, hence their star formation activity is more sensitive to feedback effects. The shape of the faint-end of the high-$z$ galaxy luminosity function (LF) contains important information on star formation and its interaction with the reionization process during the Epoch of Reionization (EoR). High-$z$ galaxies with $M_{\rm UV}\gtrsim-17$ have only recently become accessible thanks to the Frontier Fields (FFs) survey combining deep {\it HST} imaging and the gravitational lensing effect. In this paper we investigate the faint-end of the LF at redshift $>$5 using the data of FFs clusters Abell 2744 (A2744), MACSJ0416.1-2403 (M0416), MACSJ0717.5+3745 (M0717) and MACSJ1149.5+2223 (M1149). We analyze both an empirical and a physically-motivated LF model to obtain constraints on a possible turn-over of LF at faint magnitudes. In the empirical model the LF drops fast when the absolute UV magnitude $M_{\rm UV}$ is much larger than a turn-over absolute UV magnitude $M_{\rm UV}^{\rm T}$. We obtain $M_{\rm UV}^{\rm T}\gtrsim-14.6 $ (15.2) at 1 (2) $σ$ confidence level (C.L.) for $z\sim6$. In the physically-motivated analytical model, star formation in halos with circular velocity below $v_c^*$ is fully quenched if these halos are located in ionized regions. Using updated lensing models and new additional FFs data, we re-analyze previous constraints on $v_c^*$ and $f_{\rm esc}$ presented by Castellano et al. 2016a (C16a) using a smaller dataset. We obtain new constraints on $v_c^*\lesssim 59$ km s$^{-1}$ and $f_{\rm esc}\lesssim 56\%$ (both at 2$σ$ C.L.) and conclude that there is no turn-over detected so far from the analyzed FFs data. Forthcoming {\it JWST} observations will be key to tight these constraints further.

astro-ph.GA↗

arXiv2017

No evidence for a significant AGN contribution to cosmic hydrogen reionization

We reinvestigate a claimed sample of 22 X-ray detected active galactic nuclei (AGN) at redshifts z > 4, which has reignited the debate as to whether young galaxies or AGN reionized the Universe. These sources lie within the GOODS-S/CANDELS field, and we examine both the robustness of the claimed X-ray detections (within the Chandra 4Ms imaging) and perform an independent analysis of the photometric redshifts of the optical/infrared counterparts. We confirm the reality of only 15 of the 22 reported X-ray detections, and moreover find that only 12 of the 22 optical/infrared counterpart galaxies actually lie robustly at z > 4. Combining these results we find convincing evidence for only 7 X-ray AGN at z > 4 in the GOODS-S field, of which only one lies at z > 5. We recalculate the evolving far-UV (1500 Angstrom) luminosity density produced by AGN at high redshift, and find that it declines rapidly from z = 4 to z = 6, in agreement with several other recent studies of the evolving AGN luminosity function. The associated rapid decline in inferred hydrogen-ionizing emissivity contributed by AGN falls an order-of-magnitude short of the level required to maintain hydrogen ionization at z ~ 6. We conclude that all available evidence continues to favour a scenario in which young galaxies reionized the Universe, with AGN making, at most, a very minor contribution to cosmic hydrogen reionization.

astro-ph.GA↗

arXiv2017

Baby MIND: A magnetized segmented neutrino detector for the WAGASCI experiment

T2K (Tokai-to-Kamioka) is a long-baseline neutrino experiment in Japan designed to study various parameters of neutrino oscillations. A near detector complex (ND280) is located 280~m downstream of the production target and measures neutrino beam parameters before any oscillations occur. ND280's measurements are used to predict the number and spectra of neutrinos in the Super-Kamiokande detector at the distance of 295~km. The difference in the target material between the far (water) and near (scintillator, hydrocarbon) detectors leads to the main non-cancelling systematic uncertainty for the oscillation analysis. In order to reduce this uncertainty a new WAter-Grid-And-SCintillator detector (WAGASCI) has been developed. A magnetized iron neutrino detector (Baby MIND) will be used to measure momentum and charge identification of the outgoing muons from charged current interactions. The Baby MIND modules are composed of magnetized iron plates and long plastic scintillator bars read out at the both ends with wavelength shifting fibers and silicon photomultipliers. The front-end electronics board has been developed to perform the readout and digitization of the signals from the scintillator bars. Detector elements were tested with cosmic rays and in the PS beam at CERN. The obtained results are presented in this paper.

physics.ins-det↗

arXiv2017

The ASTRODEEP Frontier Fields Catalogues III. Multiwavelength photometry and rest frame properties of MACS-J0717 and MACS-J1149

We present the multiwavelength photometry of two Frontier Fields massive galaxy clusters MACS-J0717 and MACS-J1149 and their parallel fields, ranging from HST to ground based K and Spitzer IRAC bands, and the public release of photometric redshifts and rest frame properties of galaxies found in cluster and parallel pointings. This work was done within ASTRODEEP project and aims to provide a reference for future investigations of the extragalactic populations. To fully exploit the depth of the images and detect faint sources we used an accurate procedure which carefully removes the foreground light of bright cluster sources and the intra-cluster light thus enabling detection and measurement of accurate fluxes in crowded cluster regions. This same procedure has been successfully used to derive the photometric catalogue of MACS-J0416 and Abell-2744. The obtained multi-band photometry was used to derive photometric redshifts, magnification and physical properties of sources. In line with the first two FF catalogues released by ASTRODEEP, the photometric redshifts reach $\sim$4$\%$ accuracy. Moreover we extend the presently available samples to galaxies intrinsically as faint as H160$\sim$32-34 mag thanks the magnification factors induced to strong gravitational lensing. Our analysis allows us to probe galaxy masses larger then 10$^{7}$ M$\odot$ and/or SFR=0.1-1M$\odot$/yr out to redshift z$>6$.

astro-ph.GA↗

arXiv2017

Baby MIND Experiment Construction Status

Baby MIND is a magnetized iron neutrino detector, with novel design features, and is planned to serve as a downstream magnetized muon spectrometer for the WAGASCI experiment on the T2K neutrino beam line in Japan. One of the main goals of this experiment is to reduce systematic uncertainties relevant to CP-violation searches, by measuring the neutrino contamination in the anti-neutrino beam mode of T2K. Baby MIND is currently being constructed at CERN, and is planned to be operational in Japan in October 2017.

physics.ins-det↗

arXiv2017

Baby MIND: A magnetised spectrometer for the WAGASCI experiment

The WAGASCI experiment being built at the J-PARC neutrino beam line will measure the difference in cross sections from neutrinos interacting with a water and scintillator targets, in order to constrain neutrino cross sections, essential for the T2K neutrino oscillation measurements. A prototype Magnetised Iron Neutrino Detector (MIND), called Baby MIND, is being constructed at CERN to act as a magnetic spectrometer behind the main WAGASCI target to be able to measure the charge and momentum of the outgoing muon from neutrino charged current interactions.

physics.ins-det↗

arXiv2017

Evolution of cosmic star formation in the SCUBA-2 Cosmology Legacy Survey

We present a new exploration of the cosmic star-formation history and dust obscuration in massive galaxies at redshifts $0.5< z<6$. We utilize the deepest 450 and 850$μ$m imaging from SCUBA-2 CLS, covering 230arcmin$^2$ in the AEGIS, COSMOS and UDS fields, together with 100-250$μ$m imaging from Herschel. We demonstrate the capability of the T-PHOT deconfusion code to reach below the confusion limit, using multi-wavelength prior catalogues from CANDELS/3D-HST. By combining IR and UV data, we measure the relationship between total star-formation rate (SFR) and stellar mass up to $z\sim5$, indicating that UV-derived dust corrections underestimate the SFR in massive galaxies. We investigate the relationship between obscuration and the UV slope (the IRX-$β$ relation) in our sample, which is similar to that of low-redshift starburst galaxies, although it deviates at high stellar masses. Our data provide new measurements of the total SFR density (SFRD) in $M_\ast>10^{10}M_\odot$ galaxies at $0.5 10$. One third of this is accounted for by 450$μ$m-detected sources, while one fifth is attributed to UV-luminous sources (brighter than $L^\ast_{UV}$), although even these are largely obscured. By extrapolating our results to include all stellar masses, we estimate a total SFRD that is in good agreement with previous results from IR and UV data at $z\lesssim3$, and from UV-only data at $z\sim5$. The cosmic star-formation history undergoes a transition at $z\sim3-4$, as predominantly unobscured growth in the early Universe is overtaken by obscured star formation, driven by the build-up of the most massive galaxies during the peak of cosmic assembly.

astro-ph.GA↗

arXiv2016

Constraints on photoionization feedback from number counts of ultra-faint high-redshift galaxies in the Frontier Fields

We exploit a sample of ultra-faint high-redshift galaxies (demagnified HST $H_{160}$ magnitude $>30$) in the Frontier Fields clusters A2744 and M0416 to constrain a theoretical model for the UV luminosity function (LF) in the presence of photoionization feedback. The objects have been selected on the basis of accurate photometric redshifts computed from multi-band photometry including 7 HST bands and deep $K_s$ and IRAC observations. Magnification is computed on an object-by-object basis from all available lensing models of the two clusters. We take into account source detection completeness as a function of luminosity and size, magnification effects and systematics in the lens modeling of the clusters under investigation. We find that our sample of high-$z$ galaxies constrain the cut-off halo circular velocity below which star-formation is suppressed by photo-ionization feedback to $v_c^{\rm cut} < 50$ km s$^{-1}$. This circular velocity corresponds to a halo mass of $\approx5.6\times10^9~M_\odot$ and $\approx2.3\times10^9~M_\odot$ at $z=5$ and 10 respectively: higher mass halos can thus sustain continuous star formation activity without being quenched by external ionizing flux. More stringent constraints are prevented by the uncertainty in the modeling of the cluster lens, as embodied by systematic differences among the lens models available.

astro-ph.GA↗

arXiv2016

The ASTRODEEP Frontier Fields Catalogues: II - Photometric redshifts and rest-frame properties in Abell-2744 and MACS-J0416

We present the first public release of photometric redshifts, galaxy rest-frame properties and associated magnification values in the cluster and parallel pointings of the first two Frontier Fields, Abell-2744 and MACS-J0416. We exploit a multi-wavelength catalogue ranging from HST to ground-based K and Spitzer IRAC which is specifically designed to enable detection and measurement of accurate fluxes in crowded cluster regions. The multi-band information is used to derive photometric redshifts and physical properties of sources detected either in the H-band image alone or from a stack of four WFC3 bands. To minimize systematics median photometric redshifts are assembled from six different approaches to photo-z estimates. Their reliability is assessed through a comparison with available spectroscopic samples. State of the art lensing models are used to derive magnification values on an object-by-object basis by taking into account sources positions and redshifts. We show that photometric redshifts reach a remarkable ~3-5% accuracy. After accounting for magnification the H band number counts are found in agreement at bright magnitudes with number counts from the CANDELS fields, while extending the presently available samples to galaxies intrinsically as faint as H160~32-33 thanks to strong gravitational lensing. The Frontier Fields allow to probe the galaxy stellar mass distribution at 0.5-1.5 dex lower masses, depending on magnification, with respect to extragalactic wide fields, including sources at Mstar~ 10^7-10^8 Msun at z>5. Similarly, they allow the detection of objects with intrinsic SFRs>1dex lower than in the CANDELS fields reaching 0.1-1 Msun/yr at z~6-10. [abridged]

astro-ph.GA↗