Neutrino studies with FASER

Neutrino Studies with Yuxiao WANG on behalf of the FASER Collaboration 29/09/2025 XXI Workshop on Neutrino Telescopes 1 FASER at TI12 tunnel We are here! 7mlong 480 m ForwArd Search ExpeRiment TI12 tunnel 29/09/2025 XXI Workshop on Neutrino Telescopes 2 The FASER Detector 10.1088/1748-0221/19/05/P05066 •10 cm radius •7 m long 4 LHCb Outer ECAL modules 3 x 3 layers of ATLAS SCT strip modules 0.57 Tdipoles 1.5 mdecay volume 10 mm thick +dual PMT readout (σ=400 ps) 29/09/2025 XXI Workshop on Neutrino Telescopes 3 FASERν Emulsion Detector arXiv:2504.13008 silver bromide crystals •730 layers of 1.1 mm tungsten plates interleaved with emulsion films •25×30cm!,1.1 m, 1.1 t •Exchange emulsions ∼3times ayear 50 nm intrinsic position resolution emulsion films from Japan 29/09/2025 XXI Workshop on Neutrino Telescopes 4 Neutrino at FASER 2018 2019 2020 2021 2022 2023 2024 2025 Run 2 Run 3 Neutrino candidates with Run2 data First observation of collider neutrinos First 𝜈!, 𝜈"cross section measurements Differential 𝜈"cross section and flux measurements as afunction of energy FASERν emulsion detector 105 fb"# data collected by 2024 FASER electronic detector 190 fb"# data collected by 2024 PhysRevD.104.L091101 PhysRevLett.133.021802 PRL editor’s suggestion Update with increased statistics CERN-FASER-CONF-2025-002 PhysRevLett.131.031801 PRL editor’s suggestion Neutrino rapidity measurements PhysRevLett.134.211801 CERN-FASER-CONF-2025-001 •Measure neutrino cross-sections at TeV-scale; •From charged current (CC) interaction; •Flavor tagging: 𝜈!, 𝜈", 𝜈# •Expected event number for 250 fb$%,Run3: 𝜈!∼1700, 𝜈"∼8500, 𝜈#∼30 29/09/2025 XXI Workshop on Neutrino Telescopes 5 Neutrino at FASERν Phys.Rev.D 110, 012009 Performance validation •2024 testbeam data •SPS (H8 beamline) ∼20% resolution at 200 GeV Latest results: CERN-FASER-CONF-2025-002 29/09/2025 XXI Workshop on Neutrino Telescopes 6 Data Set and Simulations •Data Sets: -9.5 fb$%,LHC Run 3 -Target mass: 314.7 kg in latest analysis •MC Samples: -Light hadron production (4 samples: EPOS-LHC, QGSJET II-04, SIBYLL 2.3d, PYTHIA 8) -Charm hadron production (1 sample: POWHEG+PYTHIA 8) CERN-FASER-CONF-2025-002 29/09/2025 XXI Workshop on Neutrino Telescopes 7 Neutrino Event Selection vertex reconstruction: 𝑁$%&'()* ≥ 5, 𝑁+&,-./.# ≥ 4 PhysRevLett.133.021802 5𝜈!,20 𝜈" observed! 29/09/2025 XXI Workshop on Neutrino Telescopes 8 𝝂𝒆 CC events side view beam view 29/09/2025 XXI Workshop on Neutrino Telescopes 15 Latest neutrino results at FASER electronic detector 𝜈"cross section measurement 29/09/2025 XXI Workshop on Neutrino Telescopes 16 Summary and Outlook •FASER historic achievements: •first neutrinos observed at a particle collider •first detection of 𝜈$and 𝜈%at the LHC •first neutrino cross-section measurements in the TeV range •Current data taking: •Run3 expectations: ∼10,000 neutrino interactions •200 times more events with full Run3 dataset •FASER continues through LHC Run4 •Future: Forward Physics Facility •Ambitious upgrade program for HL-LHC (FASER2 &FASERν2) •Target: ∼1,000,000 high-energy neutrino interactions ArXiv 2503.19010 29/09/2025 XXI Workshop on Neutrino Telescopes 17 Acknowledgement •FASER is supported by: •We also thank: vLHC for the excellent performance vATLAS Collaboration for providing luminosity information vATLAS SCT Collaboration for spare tracker modules vATLAS for the use of their ATHENA software framework vLHCb Collaboration for spare ECAL modules vCERN FLUKA team for the background simulation vCERN PBC and technical infrastructure groups for the excellent support 29/09/2025 XXI Workshop on Neutrino Telescopes 18 BACKUP FASER Physics Targets •Explore forward physics (particles in very forward region not seen by ATLAS/CMS) •Search for new light, longlived particles (dark photons, ALPs, etc.) •Detect and study collider neutrinos (first-ever TeV neutrinos at LHC) PRL 134.211801 JHEP 2025, 199 29/09/2025 XXI Workshop on Neutrino Telescopes 19 29/09/2025 XXI Workshop on Neutrino Telescopes 20 Kinematic Tools Performances •300 nm position resolution has been achieved -> 0.04 mrad angular resolution for a 1 cm track. •Momentum measurement from Multiple Coulomb Scattering (MCS): Δ𝑃/𝑃 at 200 GeV ∼0.30 •EM shower energy found using segment multiplicity in core of EM shower: Δ𝐸/𝐸 at 200 GeV ∼0.21 29/09/2025 XXI Workshop on Neutrino Telescopes 21 Data Set and Simulations •Data Sets: -2022 second module → 9.5 fb#$ -Target mass: 128.6 kg -∼1.7% of the data collected to date. •MC Samples: -Light hadron production (4 samples: EPOS-LHC, QGSJET II-04, SIBYLL 2.3d, PYTHIA 8) -Charm hadron production (1 sample: POWHEG+PYTHIA 8) 29/09/2025 XXI Workshop on Neutrino Telescopes 22 Systematic Uncertainties •several factors of systematic uncertainties have been considered. •total systematics: sum in quadrature. •First observation of 𝜈!at the LHC (2023) •First neutrino cross-section measurement in the TeV range (2024) •Large uncertainty from neutrino flux. 29/09/2025 XXI Workshop on Neutrino Telescopes 23 First X-section Measurements PhysRevLett.133.021802 •4𝜈!observed •expected background 0.025$'.'%' )'.'%* •significance: 5.2𝜎 •8𝜈"observed •expected background 0.22$'.'+ )'.', •significance: 5.7𝜎 target mass 128.6 kg •FASERν also measures cross-section of Neutral Current (NC) neutrino interactions [arXiv: 2012.10500]. •Non-Standard Interaction (NSI) can be explored in conjunction with measurement of CC cross-section. 29/09/2025 XXI Workshop on Neutrino Telescopes 24 𝝂 NC Cross Sections