arXiv subjects

Elena Firu

Publications and source records attributed to Elena Firu.

16 recordsLinked to original sources

arXiv2026

Electromagnetic Shower Reconstruction and Identification in FASER's Emulsion Detector for LHC Forward Neutrino Measurements

We present methods for electromagnetic shower reconstruction and identification in the FASERnu emulsion detector using 100 GeV and 200 GeV electron test-beam data from the CERN SPS H4 beamline. The reconstruction employs a clustering-based algorithm without energy-dependent tuning to determine shower axes. A multi-level identification chain comprising track pre-selection, a cut-based selection, and a BDT classifier achieves combined background rejection rates of 99.99% (100 GeV) and 99.94% (200 GeV). The method reaches total reconstruction and identification efficiencies of 58.9% (100 GeV) and 70.8% (200 GeV) evaluated from simulated samples. Energy reconstruction using the total number of reconstructed segments as the calorimetric estimator yields relative biases of +0.6% (100 GeV) and -0.8% (200 GeV), with resolutions of 25.4% and 22.6%, respectively. Systematic uncertainties on the energy reconstruction are dominated by variations in emulsion film detection efficiency, with totals of (+10.9%/-8.2%) at 100 GeV and (+10.3%/-6.9%) at 200 GeV. The methodology provides a validated framework for electron neutrino identification with the FASERnu detector at the LHC.

hep-ex↗

arXiv2026

Optimization of muon suppression using sweeper magnets for the Forward Physics Facility at the HL-LHC

The Forward Physics Facility (FPF) at the High-Luminosity LHC (HL-LHC) will enable high-statistics measurements of TeV-scale neutrinos, but the intense flux of forward muons poses a major challenge for neutrino detectors in the far-forward region. We investigate the suppression of background muons using sweeper magnets with a simulation framework combining SIBYLL event generation, BDSIM beam transport, Geant4 particle tracking, and realistic magnetic field maps. Starting from a muon flux of $3.8\times10^3~\mathrm{cm^{-2}}$ per $\mathrm{fb^{-1}}$ without magnets, a magnet in the LHC tunnel alone achieves the target level of $2\times10^3~\mathrm{cm^{-2}}$ per $\mathrm{fb^{-1}}$. Additional magnets at the TI18 tunnel and FPF entrance further reduce the flux to $1.5\times10^3~\mathrm{cm^{-2}}$ per $\mathrm{fb^{-1}}$ in the optimized configuration. These results demonstrate that a properly optimized multi-stage sweeper magnet system can significantly reduce the forward muon background, while also highlighting the importance of realistic transport simulations and geometrical constraints in achieving further suppression.

hep-ex↗

arXiv2026

Momentum Measurement of Charged Particles in FASER's Emulsion Detector at the LHC

We present a momentum measurement method based on multiple Coulomb scattering (MCS) in the FASER$\nu$ emulsion detector. The measurement of charged-particle momenta is essential for studying neutrino interactions in the TeV energy range at the FASER experiment. This method exploits the sub-micron spatial resolution and long tracking length of the FASER$\nu$ detector, enabling momentum determination from a few GeV up to a few TeV. The performance was evaluated using Geant4-based Monte Carlo simulations and validated with muon test beam data in the momentum range 100-300 GeV. As a first probe of the method for higher momentum muons, background muons recorded by the FASER$\nu$ detector were examined, showing reconstructed momenta consistent with expectations from their angular spread.

hep-ex↗

arXiv2025

Letter of Intent: The Forward Physics Facility

The Forward Physics Facility (FPF) is a proposed extension of the HL-LHC program designed to exploit the unique scientific opportunities offered by the intense flux of high energy neutrinos, and possibly new particles, in the far-forward direction. Located in a well-shielded cavern 627 m downstream of one of the LHC interaction points, the facility will support a broad and ambitious physics program that significantly expands the discovery potential of the HL-LHC. Equipped with four complementary detectors -- FLArE, FASER$\nu$2, FASER2, and FORMOSA -- the FPF will enable breakthrough measurements that will advance our understanding of neutrino physics, quantum chromodynamics, and astroparticle physics, and will search for dark matter and other new particles. With this Letter of Intent, we propose the construction of the FPF cavern and the construction, integration, and installation of its experiments. We summarize the physics case, the facility design, the layout and components of the detectors, as well as the envisioned collaboration structure, cost estimate, and implementation timeline.

hep-ex↗

arXiv2025

Latest neutrino results from the FASER experiment and their implications for forward hadron production

The muon puzzle -- an excess of muons relative to simulation predictions in ultra-high-energy cosmic-ray air showers -- has been reported by many experiments. This suggests that forward particle production in hadronic interactions is not fully understood. Some of the scenarios proposed to resolve this predict reduced production of forward neutral pions and enhanced production of forward kaons (or other particles). The FASER experiment at the LHC is located 480 m downstream of the ATLAS interaction point and is sensitive to neutrinos and muons, which are the decay products of forward charged pions and kaons. In this study, the latest measurements of electron and muon neutrino fluxes are presented using the data corresponding to 9.5 $\mathrm{fb^{-1}}$ and 65.6 $\mathrm{fb^{-1}}$ of proton-proton collisions with $\sqrt{s}=13.6~\mathrm{TeV}$ by the FASER$\nu$ and the FASER electronic detector, respectively. These fluxes are compared with predictions from recent hadronic interaction models, including EPOS-LHCr, SIBYLL 2.3e, and QGSJET 3. The predictions are generally consistent with the measured fluxes from FASER, although some discrepancies appear in certain energy bins. More precise flux measurements with additional data will follow soon, enabling validation of pion, kaon, and charm meson production with finer energy binning, reduced uncertainties, and multi-differential analyses.

hep-ex↗

arXiv2025

Reconstruction and Performance Evaluation of FASER's Emulsion Detector at the LHC

This paper presents the reconstruction and performance evaluation of the FASER$\nu$ emulsion detector, which aims to measure interactions from neutrinos produced in the forward direction of proton-proton collisions at the CERN Large Hadron Collider. The detector, composed of tungsten plates interleaved with emulsion films, records charged particles with sub-micron precision. A key challenge arises from the extremely high track density environment, reaching $\mathcal{O}(10^5)$ tracks per cm$^2$. To address this, dedicated alignment techniques and track reconstruction algorithms have been developed, building on techniques from previous experiments and introducing further optimizations. The performance of the detector is studied by evaluating the single-film efficiency, position and angular resolution, and the impact parameter distribution of reconstructed vertices. The results demonstrate that an alignment precision of 0.3 micrometers and robust track and vertex reconstruction are achieved, enabling accurate neutrino measurements in the TeV energy range.

physics.ins-det↗

arXiv2025

Prospects and Opportunities with an upgraded FASER Neutrino Detector during the HL-LHC era: Input to the EPPSU

The FASER experiment at CERN has opened a new window in collider neutrino physics by detecting TeV-energy neutrinos produced in the forward direction at the LHC. Building on this success, this document outlines the scientific case and design considerations for an upgraded FASER neutrino detector to operate during LHC Run 4 and beyond. The proposed detector will significantly enhance the neutrino physics program by increasing event statistics, improving flavor identification, and enabling precision measurements of neutrino interactions at the highest man-made energies. Key objectives include measuring neutrino cross sections, probing proton structure and forward QCD dynamics, testing lepton flavor universality, and searching for beyond-the-Standard Model physics. Several detector configurations are under study, including high-granularity scintillator-based tracking calorimeters, high-precision silicon tracking layers, and advanced emulsion-based detectors for exclusive event reconstruction. These upgrades will maximize the physics potential of the HL-LHC, contribute to astroparticle physics and QCD studies, and serve as a stepping stone toward future neutrino programs at the Forward Physics Facility.

hep-ex↗

arXiv2024

First Measurement of the Muon Neutrino Interaction Cross Section and Flux as a Function of Energy at the LHC with FASER

This letter presents the measurement of the energy-dependent neutrino-nucleon cross section in tungsten and the differential flux of muon neutrinos and anti-neutrinos. The analysis is performed using proton-proton collision data at a center-of-mass energy of $13.6 \, {\rm TeV}$ and corresponding to an integrated luminosity of $(65.6 \pm 1.4) \, \mathrm{fb^{-1}}$. Using the active electronic components of the FASER detector, $338.1 \pm 21.0$ charged current muon neutrino interaction events are identified, with backgrounds from other processes subtracted. We unfold the neutrino events into a fiducial volume corresponding to the sensitive regions of the FASER detector and interpret the results in two ways: We use the expected neutrino flux to measure the cross section, and we use the predicted cross section to measure the neutrino flux. Both results are presented in six bins of neutrino energy, achieving the first differential measurement in the TeV range. The observed distributions align with Standard Model predictions. Using this differential data, we extract the contributions of neutrinos from pion and kaon decays.

hep-ex↗

arXiv2024

Shining Light on the Dark Sector: Search for Axion-like Particles and Other New Physics in Photonic Final States with FASER

The first FASER search for a light, long-lived particle decaying into a pair of photons is reported. The search uses LHC proton-proton collision data at $\sqrt{s}=13.6~\text{TeV}$ collected in 2022 and 2023, corresponding to an integrated luminosity of $57.7\text{fb}^{-1}$. A model with axion-like particles (ALPs) dominantly coupled to weak gauge bosons is the primary target. Signal events are characterised by high-energy deposits in the electromagnetic calorimeter and no signal in the veto scintillators. One event is observed, compared to a background expectation of $0.44 \pm 0.39$ events, which is entirely dominated by neutrino interactions. World-leading constraints on ALPs are obtained for masses up to $300~\text{MeV}$ and couplings to the Standard Model W gauge boson, $g_{aWW}$, around $10^{-4}$ GeV$^{-1}$, testing a previously unexplored region of parameter space. Other new particle models that lead to the same experimental signature, including ALPs coupled to gluons or photons, U(1)$_B$ gauge bosons, up-philic scalars, and a Type-I two-Higgs doublet model, are also considered for interpretation, and new constraints on previously viable parameter space are presented in this paper.

hep-ex↗

arXiv2023

Development of proton beam irradiation system for the NA65/DsTau experiment

Tau neutrino is the least studied lepton of the Standard Model (SM). The NA65/DsTau experiment targets to investigate $D_s$, the parent particle of the $\nu_\tau$, using the nuclear emulsion-based detector and to decrease the systematic uncertainty of $\nu_\tau$ flux prediction from over 50% to 10% for future beam dump experiments. In the experiment, the emulsion detectors are exposed to the CERN SPS 400 GeV proton beam. To provide optimal conditions for the reconstruction of interactions, the protons are required to be uniformly distributed over the detector's surface with an average density of $10^5~\rm{cm^{-2}}$ and the fluctuation of less than 10%. To address this issue, we developed a new proton irradiation system called the target mover. The new target mover provided irradiation with a proton density of $0.98~\rm{cm^{-2}}$ and the density fluctuation of $2.0\pm 0.3$% in the DsTau 2021 run.

physics.ins-det↗

arXiv2019

DsTau: Study of tau neutrino production with 400 GeV protons from the CERN-SPS

In the DsTau experiment at the CERN SPS, an independent and direct way to measure tau neutrino production following high energy proton interactions was proposed. As the main source of tau neutrinos is a decay of Ds mesons, produced in proton-nucleus interactions, the project aims at measuring a differential cross section of this reaction. The experimental method is based on a use of high resolution emulsion detectors for effective registration of events with short lived particle decays. Here we present the motivation of the study, details of the experimental technique, and the first results of the analysis of the data collected during test runs, which prove feasibility of the full scale study of the process in future.

hep-ex↗

arXiv2018

Event by Event analysis of Maximum Pseudo-rapidity Gap Fluctuation in High energy Nucleus-nucleus Collisions

A study of Event by Event analysis of maximum Pseudo-rapidity Gap Fluctuation in heavy-ion collisions in terms of the scaled variance ω has been carried out for relativistic AA collisions with multiplicity cut (N >10) using nuclear emulsion data at 4.5 AGeV/c. The values of scaled variance are found to be greater than zero indicating the presence of strong fluctuation of maximum rap gap values in the multiparticle production process. The event by event fluctuations are found to decrease with the increase of average multiplicity of the interactions. Experimental analysis has been compared with the results obtained from the analysis of events simulated by generating random numbers (MC-RAND events) and also by Ultra Relativistic Quantum Molecular Dynamics (UrQMD) model. UrQMD model simulated values of event by event fluctuations of maximum rapidity gap are less than the corresponding experimental values.

nucl-ex↗

arXiv2018

Multifractal analysis of charged particle multiplicity distribution in the framework of Renyi entropy

A study of multifractality and multifractal specific heat has been carried out for the produced shower particles in nuclear emulsion detector for 16O-AgBr, 28Si-AgBr and 32S-AgBr interactions at 4.5AGeV/c in the framework of Renyi entropy. Experimental results have been compared with the prediction of Ultra Relativistic Quantum Molecular Dynamics (UrQMD) model. Our analysis reveals the presence of multifractality in the multiparticle production process in high energy nucleus-nucleus interactions. Degree of multifractality is found to be higher for the experimental data and it increases with the increase of projectile mass. The investigation of quark-hadron phase transition in the multiparticle production in 16O-AgBr, 28Si-AgBr and 32S-AgBr interactions at 4.5 AGeV/c in the framework of Ginzburg-Landau theory from the concept of multifractality has also been presented. Evidence of constant multifractal specific heat has been obtained for both experimental and UrQMD simulated data.

nucl-ex↗

arXiv2018

Projectile Fragmentation of relativistic nuclei in peripheral Collisions

A study of multiplicity distribution of singly charged, doubly charged, multi charged projectile fragments and shower particles have been carried out for the peripheral collisions in 16O-emulsion,22Ne-emulsion and 28Si-emulsion interactions at an incident momentum of (4.1-4.5) AGeV/c. Events having no target fragments have been designated as peripheral collision events. Percentage of peripheral events has been found to increase with the increase of projectile mass. Dispersion of the multiplicity distribution and its dependence on projectile mass for projectile fragments and shower particles has also been investigated. Dependence of average multiplicity of projectile fragments and shower particles on the mass of the projectile beam has been studied. Study of different fragmentation mode during the emission of multi charged projectile fragments has also been carried out.

nucl-ex↗

arXiv2017

A Comparative Study of kaon to pion ratio in Proton-Proton Collisions at different energies ---Experimental Results vs. Model Simulation

A detailed study of energy dependence of positive kaon to pion, negative kaon to pion and total kaon to pion multiplicity ratio have been carried out in pp collisions at 6.3, 17.3, 62.4, 200 and 900 GeV and also at root s =2.76 TeV and 7 TeV in the framework of UrQMD and DPMJET III model. Energy dependence of positive kaon to pion and negative kaon to pion show different behavior in case of UrQMD and DPMJET III model. The presence of the horn like structure in the variation of positive kaon to pion and negative kaon to pion ratio with energy for the experimental data is supported by the DPMJET III model. Experimentally it has been observed that as energy increases, the total kaon to pion multiplicity ratio increases systematically for pp collisions at lower energies and becomes independent of energy in LHC energy regime. Our analysis on total kaon to pion multiplicity ratio with UrQMD data is well supported by the experimental results obtained by different collaborations in different times. In case of DPMJET III data, the saturation of kaon to pion ratio at LHC region has not been observed.

nucl-ex↗

arXiv2013

Physics at the CLIC e+e- Linear Collider -- Input to the Snowmass process 2013

This paper summarizes the physics potential of the CLIC high-energy e+e- linear collider. It provides input to the Snowmass 2013 process for the energy-frontier working groups on The Higgs Boson (HE1), Precision Study of Electroweak Interactions (HE2), Fully Understanding the Top Quark (HE3), as well as The Path Beyond the Standard Model -- New Particles, Forces, and Dimensions (HE4). It is accompanied by a paper describing the CLIC accelerator study, submitted to the Frontier Capabilities group of the Snowmass process.

hep-ex↗