arXiv subjects

LHC Collaboration

Publications and source records attributed to LHC Collaboration.

11 recordsLinked to original sources

arXiv2026

Measurement of the muon neutrino charged-current cross section with SND@LHC

We report a measurement of the muon neutrino charged-current (CC) interaction cross section on tungsten using the electronic detectors of the SND@LHC experiment at the CERN Large Hadron Collider. The analysis uses proton--proton collision data at a centre-of-mass energy of $\sqrt{s} = 13.6$ TeV, corresponding to an integrated luminosity of $68.6 ~\text{fb}^{-1}$ collected during LHC Run 3 in 2022 and 2023. A total of 31 $\nu_\mu$ CC candidates are selected against an expected background of $5.0 \pm 1.1$ events, consistent with a signal expectation of $24^{+10}_{-9}$ events. The signal strength is measured to be $\hat{\mu} = 1.09^{+0.72}_{-0.37}$, and the combined muon neutrino and anti-neutrino CC cross section on tungsten is determined to be $\sigma(\nu_\mu + \bar{\nu}_\mu) = (37^{+24}_{-12})\times 10^{-35}~\text{cm}^2$ at a median energy of $228$ GeV. In addition, a calorimetric measurement of the hadronic energies of the neutrino candidate events is performed, making use of calibration data from dedicated test-beam campaigns.

hep-ex↗

arXiv2026

Study of the Run-3 muon flux at the SND@LHC experiment

Long-range muons produced in proton-proton collisions at the ATLAS interaction point constitute the primary background for neutrino interaction searches at the SND@LHC experiment. This work presents a comprehensive characterization of the muon flux throughout LHC Run-3, benchmarking Monte Carlo simulations against experimental measurements. Measured and simulated muon rates agree within 10-15% across all Run-3 configurations. Following the substantial background increase in 2024 as a result of a beam optics change, the reversion to nominal optics in 2025 did not restore the 2022-2023 levels due to the unprecedented adoption of horizontal crossing in ATLAS. As enlightened by simulation results, the latter enhanced the contribution of high-angle muons originating from diffractive proton losses in the LHC Dispersion Suppressor region. Their identification enabled the design of mitigation strategies that were experimentally validated. The simulation framework was also applied to the future High-Luminosity LHC configuration, resulting in a considerable muon rate rise, driven by both the planned luminosity increase and the enlarged magnet aperture. Nevertheless, the upgrade from emulsion films to silicon vertex detectors will preserve the efficiency of the experiment even in such a high-rate environment.

hep-ex↗

arXiv2026

Measurement of the Muon Flux at SND@LHC: Results from the 2023-2025 Proton and Heavy-Ion Periods

The SND@LHC experiment investigates neutrinos in the $7.2 < \eta < 8.4$ forward pseudorapidity range. The detector consists of a veto system, a scintillating fiber tracker interleaved with emulsion cloud chambers, and a downstream muon system. Muons originating from collisions at ATLAS (IP1) constitute the primary background for CC neutrino interactions and determine the replacement frequency of the emulsion target. A precise characterization of this flux is therefore essential. In this work, we report the muon flux measured in the central $31 \times 31\text{ cm}^2$ fiducial area of the detector using data from 2023 through 2025. The measured fluxes for $\textbf{proton collisions}$ are: $(1.90 \pm 0.04) \times 10^{-2}\text{ nb/cm}^2$ (2023), $(3.76 \pm 0.09) \times 10^{-2}\text{ nb/cm}^2$ (2024), and $(2.48 \pm 0.05) \times 10^{-2}\text{ nb/cm}^2$ (2025). A 2024 reference proton run at $\sqrt{s} = 5.36\text{ TeV}$ yielded $(4.21 \pm 0.14) \times 10^{-2}\text{ nb/cm}^2$, providing a direct baseline for the heavy-ion energy regime. The measured fluxes for $\textbf{heavy-ion collisions}$ are $(3.11 \pm 0.12) \times 10^4\text{ nb/cm}^2$, $(5.53 \pm 0.22) \times 10^4\text{ nb/cm}^2$, and $(3.24 \pm 0.13) \times 10^4\text{ nb/cm}^2$ in 2023, 2024, and 2025, respectively. Uncertainties are dominated by systematic effects, with the statistical component contributing $\lesssim 0.1\%$ to the total uncertainty. These results are in agreement with Monte Carlo predictions.

hep-ex↗

arXiv2026

SND@LHC Upgrade for the High-Luminosity LHC: Physics Reach and Installation Scenarios

The SND@LHC experiment is currently taking data at the Large Hadron Collider (LHC), exploring the unique forward region at pseudorapidities from 7.2 to 8.4. Its physics programme covers neutrinos originating from heavy-flavour decays and feebly interacting particles produced in proton proton collisions. Building upon the successful operation of the present detector, this paper presents the physics reach of the approved SND@LHC upgrade for Run4 of the LHC, and compares it with an alternative installation scenario. Lowering the detector by approximately 40 cm and shifting it horizontally by about 30 cm, while keeping it off-axis, increases the total neutrino interaction rate by a factor of five. The paper describes the design of the upgraded detector and compare the physics performance in both installation scenarios.

hep-ex↗

arXiv2025

The SND@LHC neutron shielding

The design and construction of a neutron shielding for the SND@LHC detector, which utilizes a combination of plexiglass and borated polyethylene, is presented. FLUKA simulations were employed to optimize the shielding configuration and assess its efficiency. Results indicate a significant reduction in neutron flux, ensuring the long-term stability of the emulsion films used in the target of the SND@LHC detector.

physics.ins-det↗

arXiv2025

Studies of Hadronic Showers in SND@LHC

The SND@LHC experiment was built for observing neutrinos arising from LHC pp collisions. The detector consists of two sections: a target instrumented with SciFi modules and a hadronic calorimeter/muon detector. Energetic $\nu$N collisions in the target produce hadronic showers. Reconstruction of the shower total energy requires an estimate of the fractions deposited in both the target and the calorimeter. In order to calibrate the SND@LHC response, a replica of the detector was exposed to hadron beams with 100 to 300 GeV in the CERN SPS H8 test beam line in Summer 2023. This report describes the methods developed to tag the presence of a shower, to locate the shower origin in the target, and to combine the target SciFi and the calorimeter signals so to measure the shower total energy.

physics.ins-det↗

arXiv2025

Installation and performance of the 3rd Veto plane at the SND@LHC detector

During 2022/2023 the optimal inefficiency of the Veto system of the SND@LHC detector was measured to be $(7.8\pm2.8)\times10^{-8}$. To reduce this inefficiency, a third Veto plane was installed during the 2023-2024 Year End Technical Stop. In addition, the Veto system was lowered to cover the target fully, thereby increasing acceptance. This paper describes how the inefficiency of the Veto system was reduced from $7.8\times10^{-8}$ with an acceptance of about $64\%$ of the target area in 2022-2023 to $(4.9\pm1.9)\times10^{-9}$ on the full area in 2024.

physics.ins-det↗

arXiv2024

Observation of collider neutrinos without final state muons with the SND@LHC experiment

We report the observation of neutrino interactions without final state muons at the LHC, with a significance of 6.4$ \sigma$. A data set of proton-proton collisions at $\sqrt{s}= 13.6$ TeV collected by SND@LHC in 2022 and 2023 is used, corresponding to an integrated luminosity of 68.6 fb$^{-1}$. Neutrino interactions without a reconstructed muon are selected, resulting in an event sample consisting mainly of neutral-current and electron neutrino charged-current interactions in the detector. After selection cuts, 9 neutrino interaction candidate events are observed with an estimated background of 0.32 events.

hep-ex↗

arXiv2023

Measurement of the muon flux at the SND@LHC experiment

The Scattering and Neutrino Detector at the LHC (\SND) started taking data at the beginning of Run 3 of the LHC. The experiment is designed to perform measurements with neutrinos produced in proton-proton collisions at the LHC in an energy range between 100GeV and 1 TeV. It covers a previously unexplored pseudo-rapidity range of $7.2<\eta<8.4$. The detector is located 480 m downstream of the ATLAS interaction point in the TI18 tunnel. It comprises a veto system, a target consisting of tungsten plates interleaved with nuclear emulsion and scintillating fiber (SciFi) trackers, followed by a muon detector (UpStream, US and DownStream, DS). In this article we report the measurement of the muon flux in three subdetectors: the emulsion, the SciFi trackers and the DownStream Muon detector. The muon flux per integrated luminosity through an 18$\times$18 cm$^{2}$ area in the emulsion is $1.5 \pm 0.1(\textrm{stat}) \times 10^4\,\textrm{fb/cm}^{2}$. The muon flux per integrated luminosity through a 31$\times$31 cm$^{2}$ area in the centre of the SciFi is $2.06\pm0.01(\textrm{stat})\pm0.12(\textrm{sys}) \times 10^{4} \textrm{fb/cm}^{2}$. The muon flux per integrated luminosity through a 52$\times$52 cm$^{2}$ area in the centre of the downstream muon system is $2.35\pm0.01(\textrm{stat})\pm0.10(\textrm{sys}) \times 10^{4}\,\textrm{fb/cm}^{2}$. The total relative uncertainty of the measurements by the electronic detectors is 6 $\%$ for the SciFi and 4 $\%$ for the DS measurement. The Monte Carlo simulation prediction of these fluxes is 20-25 $\%$ lower than the measured values.

hep-ex↗

arXiv2023

Observation of collider muon neutrinos with the SND@LHC experiment

We report the direct observation of muon neutrino interactions with the SND@LHC detector at the Large Hadron Collider. A data set of proton-proton collisions at $\sqrt{s} = 13.6\,$TeV collected by SND@LHC in 2022 is used, corresponding to an integrated luminosity of 36.8$\,\rm{fb}^{-1}$. The search is based on information from the active electronic components of the SND@LHC detector, which covers the pseudo-rapidity region of $7.2 < \eta < 8.4$, inaccessible to the other experiments at the collider. Muon neutrino candidates are identified through their charged-current interaction topology, with a track propagating through the entire length of the muon detector. After selection cuts, 8 $\nu_\mu$ interaction candidate events remain with an estimated background of 0.076 events, yielding a significance of seven standard deviations for the observed $\nu_\mu$ signal.

hep-ex↗

arXiv2022

SND@LHC: The Scattering and Neutrino Detector at the LHC

SND@LHC is a compact and stand-alone experiment designed to perform measurements with neutrinos produced at the LHC in the pseudo-rapidity region of ${7.2 < \eta < 8.4}$. The experiment is located 480 m downstream of the ATLAS interaction point, in the TI18 tunnel. The detector is composed of a hybrid system based on an 830 kg target made of tungsten plates, interleaved with emulsion and electronic trackers, also acting as an electromagnetic calorimeter, and followed by a hadronic calorimeter and a muon identification system. The detector is able to distinguish interactions of all three neutrino flavours, which allows probing the physics of heavy flavour production at the LHC in the very forward region. This region is of particular interest for future circular colliders and for very high energy astrophysical neutrino experiments. The detector is also able to search for the scattering of Feebly Interacting Particles. In its first phase, the detector will operate throughout LHC Run 3 and collect a total of 250 $\text{fb}^{-1}$.

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