PoS(ICHEP2020)112 . 1 − fb https://pos.sissa.it/ , the a interacting in the detector. Here, we present an g a program, as well as the analysis for the neutrino detection , and 20 ` a a ) to study at the highest man-made energies and got a , 5,800 4 a on behalf of the FASER Collaboration ∗ 0, at the LHC . [email protected] Speaker ∗ approval by the CERN Research Boardexist in up December to 2019. a To few date, 100 neutrino GeV with cross-section data accelerator-based neutrino beams. With FASER overview and the status of the FASER in the 2018 data. FASER, the Forward Search Experiment ataiming the to search Large for light, Collider weakly-interacting (LHC), new480 particles. is m an downstream The of experiment particle the detector ATLAS will interactionproposed be point. a located new In detector addition (FASER to searches for new particles, we cross-sections will be measured in the currentlyand unexplored 6 energy In TeV. range particular, between electron-neutrino a and few tau-neutrino 100highest cross GeV energy sections ever. will be Furthermore, measured the at channelsproduction the could associated be with studied. heavy As quark a feasibility (charm study,detector we and performed location beauty) a test with run in a 2018 30-kg atBy the lead/tungsten proposed analyzing emulsion the detector data, and we collected selectedmultivariate analysis data several for neutrino of the separation interaction 12.5 from candidates the andat background are towards the a performing LHC. first a From detection of 2022 neutrinos towith 2024 a during target mass Run 3 of of 1.2would yield the tons, roughly LHC, 1,300 possibly we coupled will with deploy the an FASER emulsion magnetic detector spectrometer, which Albert Einstein Center for Fundamental Physics,Universität Laboratory Bern, for Sidlerstrasse High 5, Energy CH-3012 Physics, Bern, Switzerland E-mail: Copyright owned by the author(s) under the terms of the Creative Commons 0 © Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). 40th International Conference on High EnergyJuly physics 28 - - ICHEP2020 August 6, 2020 Prague, Czech Republic (virtual meeting) Akitaka Ariga Detecting and studying high-energy neutrinos with FASER PoS(ICHEP2020)112 ) a Akitaka Ariga TeV), which will aims to detect and 3 a . 6 and other accelerator- a  > Muon neutrino spectra from differ- at the LHC a Figure 2: ent neutrino beamlines. Y-axisscaled is an interaction arbitrarily- rate (numberper GeV). of interactions energy spectra of FASER 2 ν ` a (GeV) ν E 3 FASER 480 m downstream of the ATLAS, through about 100 m 10 ∼

NuTeV Uncharted energy range

DONuT . Furthermore the beam includes all three neutrino generations, 2 a GeV) and atmospheric neutrino data ( BDF/SHiP 10 Schematic view of the neutrino beamline for this project. 360 10

 < CNGS/OPERA

Figure 1:

NuMi/Minerva NuMi/Minerva 1 LBNF/ND

cross sections will be measured at the highest energy ever. With this beam and a flavor- T2K/on-axis BNB/MiniBooNE g 1 a 1 2 − −

10

10 By using this beamline, we can exploit neutrinos at the high energy frontier of accelerator The FASER experiment is a newly approved experiment at the CERN-LHC. It has two physics So far, no neutrinos produced at a collider has ever been detected. FASER

µ interacting spectrum, spectrum, interacting E/GeV (a.u.) E/GeV ν × Φ and 4 a sensitive , we will studya production, brand-new propagation kinematical and regime. interactionscosmic of It ray neutrinos has physics. at implications for neutrino physics, but also for QCD and eventually be covered by FASER neutrinos.2 Figure shows the comparison of study “collider neutrinos” for the first time, by exploiting neutrinosschematics from of the the LHC.1 Figure neutrinoshows the beamline setupof proposed for is this produced experiment. at An theinto intense interaction neutrinos forward point and beam in leptons. the Most ATLASdipole of apparatus. magnets, the and A remaining neutral fraction charged hadrons particles are of absorbed are themNeutrinos in then decay travel the deflected to beamline by the infrastructure the and detector LHC rock located of shielding. rock. Although not designedcomponents for a of conventional high-energy neutrino neutrino beamline, beamlines, thishadron namely setup shielding. a provides essential target, a sweeping magnet and a based experiments/projects. To date, there isthe an accelerator unexplored energy data range ( at the TeV scale between pillars, namely the new long-lived particles search [1] and high-energy neutrino studies (FASER 1. Neutrinos at the LHC [2,3]. This presentation focuses on the neutrino program. Detecting and studying high-energy neutrinos with FASER PoS(ICHEP2020)112 in-situ ] 2 − Akitaka Ariga collision point. ? - ? 4 4 10 10 4 ) × ) × 4 2 10 . . 0 0 × 2 ± ± 2 9 . . 1 1 ( ( at the LHC a normalized flux, main peak [fb cm 3 ] 2 − 4 4 10 10 10 GeV) ) × ) × > 7 3 . . 0 0 , the tracks were successfully reconstructed by using the software 2 ± ± 6 0 . . cm / 2 3 with respect to the beam. The main background is expected from neutral ( ( 1 . 0 of data. The detector was made of emulsion films interleaved with either 1-mm- normalized flux, all [fb cm 1 \ < particles − measurements by emulsion detectors at the TI18 location. We show photo of the installed 5 fb FLUKA (muons, E tan 10 × TI18 TI12 In situ Measured fluxes from emulsion detector data [1]. The fluxes in the main peak (within 10 mrad) 3 ' In order to prove the feasibility of neutrino measurements, we performed a series of Furthermore, a 30-kg pilot neutrino detector was placed on axis in the TI-18 tunnel, which An effective target mass of 12.3 kg has been analyzed, out of which 11 neutral vertices were collected 12.5 Table 1: should be compared with the muon flux computed by the FLUKA simulation. 2. Pilot measurements in 2018 measurements in 2018. Emulsion detectors were installedand in TI-12 two candidate tunnels, sites, on the the so-called TI-18 beamposition collision with axis. respect The to two ATLAS. candidate The setup sitesshown and are in measured located3. Figure angular at The distribution the main in symmetric angular the peakThe TI-18 is secondary tunnel consistent is peak with the is direction due of to the fluxes the are backward reported particles in1. from Table the These beamline particlesa component. are very found The to little measured be hadron mostly muons component. andThis electrons, result Muons and shows and with that electrons an doalso emulsion not neutrino detector mimic measurements can a are work neutrino feasible. at interaction the vertex. actual experimental environment and selected by requesting 5 orangle within more charged particles at the interaction vertex, with their emission Figure 3: detectors (left), map of(right). the installation location (center), and angular distribution of the detected particle thick lead plates or 0.5-mm-thick tungstenand plates. one of4 Figure thereports selected the neutrinohigh, setup, interaction reconstructed candidates. tracks, Although the chargeddeveloped particle for the density NA65/DsTau was experiment]. [4 hadrons produced by muons interactingnot in aimed the at by upstream the rock. pilot detector, Since the separation the of lepton neutrino and identification neutral was hadron interactions is more Detecting and studying high-energy neutrinos with FASER PoS(ICHEP2020)112 . 2 cm 0.4 tracks/ 5 10 Akitaka Ariga BDT output 0.3 × 3

Data Preliminary 0.2 m 0.1 500 µ detector is a tungsten-emulsion a 10 emulsion films. The red scale bar 0 × , relevant for electro-magnetic shower 0 - 0.1 − 2 mm at the LHC 1 4 3 2 0 a ×

4.5 3.5 2.5 1.5 0.5 Number of events of Number 4 0.4 1.3 m, with a target mass of 1.2 tons. It has a longitudinal BDT output 0.3 × BDT distribution of the MC and data. will be studied separately. The neutrino energy will be recon- neutrino signal background ` 0.2 ¯ 25 cm a Area normalized × and Figure 5: 0.1 has capabilities to identify lepton flavors and also charm/beauty particles. ` a a by combining the topological and kinematical measurable, which would yield 0 : Reconstructed tracks in the 2 mm a , important for muon identification, and 285 : The 30 kg pilot neutrino detector installed in the LHC tunnel in 2018, which collected 12.5 ’s data taking in Run 3 of LHC operation (14 TeV) has been approved by CERN. 0.1 Center m. About 13,000 tracks were observed, corresponding to a track density of _ − a ` 0 away from the background-only hypothesis. This demonstrates the capability to detect is followed by the magnetic spectrometer, which complements muon charge identification. 0.1

0.02 0.16 0.14 0.12 0.08 0.06 0.04 a a.u. f : A vertex found in the detector with no incoming charged track. Yellow line segments are the measured FASER of data. 1 − Right tracks in the emulsion films and gray lines are their extrapolations. FASER reconstruction. FASER Thanks to this feature, shows 1000 fb structed in FASER Figure 4: Left detector with a size of 25 cm The FASER apparatus in Run 3 is shown inlength6. Figure of 10 FASER Detecting and studying high-energy neutrinos with FASER challenging than that in theand kinematical physics variables. run.5 Figure shows A theexpected number BDT multivariate of output method neutrino distributions signal was for and the applied5.6 neutral MC events, on hadron and respectively. background the A data. in preliminary the topological The given hypothesiswas sample test applied are based on 1.5 on the and the full range profile of likelihood BDTof ratio output 2.1 method distributions, which resulted in aneutrinos statistical significance at the LHC with this detector technology. 3. Prospects in Run 3 (2022-2024) PoS(ICHEP2020)112 . 1 − fb  B

, ,  is sensitive to c

Akitaka Ariga a Main parent neutrino interactions would also constitute collision has a rather ) a 4 ? - 10 ? O( 830 GeV 840 GeV 970 GeV will be placed upstream of the spectrometer. , we expect a , will be compared among three neutrino 1 − at the LHC Mean interacting energy a fb CC ℓ detector over the beamline. The neutrino beam a inclusive a # 5 scattering. There are many more physics subjects, / 4 CC a ℓ a interaction rates. In other words, FASER charm # g 110, 55 a = 8437, 2737 2986, 1261 and are described in [2]. ) FLUKA-based a and  ( 4 ℓ a a 2 ' 12, 6 816, 447 6756, 2074 FASER estimation Expected number of charged-current interactions occurring in 1.2-ton detector with 150 g ` 4 Schematic of the FASER apparatus in Run 3. FASER detector on axis. Also the tunnel has been refurbished and ready for the installation of ¯ ¯ ¯ a a a , , , a 4 g ` a a a During Run 3 with a nominal luminosity of 150 Using observed energy-dependent interaction rates and estimated neutrino fluxes, we will study The FASER Collaboration is preparing the detector setup towards the data taking in 2022. Table 2: Figure 6: Detecting and studying high-energy neutrinos with FASER in an energy resolution of about 30%. occurring in the detector,negligible. as detailed In in particular,2. Table the forward Currently, charm the hadron neutrino production flux at uncertainty the is not three-flavor neutrino cross sections at the unchartedcross energy range section at 350 measurement GeV - is 6 Thecharged-current presented TeV. projected interactions, in7. Figure Furthermore, the charm production rate in large uncertainty, which affects the QCD problems, namely theimportant gluon/charm inputs PDF for in astrophysical proton neutrino orestimation observation intrinsic is by charm. currently neutrino under telescopes. These an arein The intensive also Pythia review, neutrino an involving 8 flux the and forward the hadron beam production transportation modeling tuning with the BDSim framework. flavors. This might sheduniversality violation light in on heavy meson the decays. recently-identifed It flavor is worth anomalies, noting which that FASER suggests lepton As shown in8, Figure theFASER trench at the detector site has been prepared, which allows placing the which could be explored by FASER detector components. In parallel, a protectiona of possible the LHC damage beamline when has transporting been the putis in FASER expected order to to be prevent delivered in February 2022. the first observation of charm production in PoS(ICHEP2020)112 interactions, ) Akitaka Ariga 4 measurements in 10 O( B8CD - 8= Technical Proposal: detector (right). a ]. at the LHC a ]. 6 1908.02310 1906.03487 (2020) 61[ C80 Technical Proposal for FASER: ForwArd Search ExpeRiment at the Detecting and Studying High-Energy Collider Neutrinos with FASER at (2020) 033[ DsTau: Study of tau neutrino production with 400 GeV from the . 01 Projected neutrino cross section measurement during Run 3 (2022-2024) JHEP , at the LHC will be the first experiment making use of “Collider neutrinos”. It will Eur. Phys. J. , Tech. Rep. CERN-LHCC-2019-017., LHCC-P-015 CERN, Geneva (11, 2019). , collaboration, collaboration, a collaboration, Figure 7: 1812.09139 Schematics (left) and photo (center) of the FASER cite in the LHC tunnel, and the protection of , FASER CERN-SPS DsTau FASERnu FASER LHC FASER the LHC study neutrinos at the high energy frontier of man-made neutrinos. The 4. Conclusion 2018 quantified the background andmethod. also Data demonstrated taking the in neutrino Run detection 3 (2022-2024) with would the yield proposed neutrino interaction [3] H. Abreu, C. Antel, A. Ariga, T. Ariga, J. Boyd, F. Cadoux et al., [4] Figure 8: the LHC beamline against an accident during the transportation of FASER which allows sensitive studies of neutrinophysics run properties in and 2022. flavor physics. We are preparing for the References [1] [2] Detecting and studying high-energy neutrinos with FASER