PoS(EPS-HEP2019)409 1 − https://pos.sissa.it/ interacting in the detector. Here, we present τ ν , and 20 µ ν , 20,000 e ν for the FASER Collaboration ∗ tomoko.ariga@.ch an overview of the FASER neutrinorun. program, as well as a preliminary analysis of the 2018 test Speaker. FASER is a new experimentweakly interacting at new the particles, Large complementingbe other located Collider experiments. 480 (LHC) m The aiming downstream particleparticles, of to detector we the search also will ATLAS aim for interaction to point. study light, trinos high-energy In at this of addition location. all to To flavors, date, searches as muon- there forneutrino cross-section is new beams, data, a obtained exist huge with up flux accelerator-based of to neu- LHC-FASER, 350 the GeV, but neutrino we cross are sectionsrange still will between missing 350 be data GeV measured and at 6 in the TeV. Inergy the particular, TeV ever. tau energy currently Furthermore, neutrinos scale. the will unexplored be channels energy measured At associated at withcan the heavy highest be quark en- studied. (charm and As beauty) production alocation, feasibility using study, a we 30 performed kg a lead/tungsten test emulsion-based run neutrino in detector. 2018 at We collected the 12.5 proposed fb detector of data, and expect a few tens2021 of to neutrino interactions 2023 to during have Run been 3 recordedwith in of a the the target detector. 14 From mass TeV LHC, of we 1.2would are yield tons, planning roughly possibly 1,300 to coupled deploy with an the emulsion FASER detector magnetic spectrometer, which ∗ Copyright owned by the author(s) under the terms of the Creative Commons c Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). European Physical Society Conference on High10-17 Energy July, Physics 2019 - EPS-HEP2019 - Ghent, Belgium Tomoko Ariga Kyushu University E-mail: Study of high-energy neutrinos in theexperiment FASER at the LHC PoS(EPS-HEP2019)409 4 ν 10 ] for 6 (GeV) ν , E 5 , ν 3 τ 4 ], is a new ν 10 , ,[ τ ν e spectrum (a.u.) τ 10 Tomoko Ariga τ ν ν FASER ν , τ τ ] and technical ν ν , τ τ ν measurements ν 11 τ DONUT ν 2 ] for SK 3 10 IceCube , OPERA 2 energy ranges of oscillated will significantly extends 1 0

0.1

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 ν

ν ν

× σ 10 ( /E /GeV) /GeV) cm

2 •38 6 10 (GeV) ], we indicate only the energy ranges of mixed) ν E ν µ 9 , 5 ν µ 10 shows existing constraints on neutrino-

1 IceCube ( 4 10 (left)). The letter of intent [ (right) shows the expected energy spectrum of ν 2 1 2 ], and IceCube [ spectrum (a.u.) 3 µ 8 FASER ν 10 detector. For all three neutrino flavors, the expected en- µ µ ν ν ν 2 10 accelerator data 1 0

0.1

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2

ν ν

× σ cm 10 ( /E

will fill the gap between existing measurements using accelerator /GeV)

2 ]. •38 6 ν 4 , 10 5 ], SuperKamiokande [ 7 (GeV) ν E e 3 ν ν , 10 e ), together with the expected energy spectra of neutrinos that interact in the FASER cross section measurements. ν ] is a proposed detector designed to detect collider neutrinos at the highest man- τ spectrum (a.u.) τ e 1 ν FASER ν [ ν ] for this experiment were reviewed by LHCC, and approved by CERN in March ν DONUT 2 12 ] for Existing constraints on neutrino-nucleon CC scattering cross sections ([ e e 10 3 ν ν E53 E53 In addition to searches for new particles, we also aim to study high-energy neutrinos of all FASER, the Forward Search Experiment at the (LHC) [ FASER 1 0 (appropriate for heavy, strongly interacting particles). To complement such searches, a particle

0.1 , and [

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 ν ν

× σ /GeV) /GeV) cm 10 ( /E

2 T µ •38 neutrinos with CC interactions at the FASER location. flavors since the FASER location isenergy also neutrinos ideal for produced providing at the the first detection LHC. and Figure studies of high- ν detector. For all threeconstrained. neutrino For flavors, OPERA the [ expected energy spectra peak at energies that are currently un- experiment at the LHC withdark the photons goal and -like of particles. searchingp for Other light, searches weakly for interacting newdetector will physics particles be at such located 480 the as m LHC downstreamaxis of focus the in ATLAS on interaction point high the along the unused beamproposal service collision [ tunnel TI12 (Figure 2019. ergy spectra peak at energies thatthe are neutrino currently cross unconstrained. section FASER For measurements muon to neutrinos, higher FASER energiesexperiments for and IceCube both [ electron and tau neutrinos. Figure 1: their respective 2. The FASER experiment nucleon charged-current (CC) scattering cross sections,of together neutrinos with interacting the in expected the energy FASER spectra Study of high-energy neutrinos in the FASER experiment at the LHC 1. Physics motivation made energies and to study their properties. Figure PoS(EPS-HEP2019)409 25 × shows 3 . For LHC- and the mean Tomoko Ariga 4 int 10 ν λ -1 . The uncertainties 1 − 3 10 . We will reconstruct the [GeV] 3 m-thick plastic base. The ν E τ µ 2 ν 10 μ e CC interactions by identifying ν ν τ τ ν ν 827 GeV 631 GeV 965 GeV μ e ν ν etio neatn ihFASERν with interacting Neutrinos =150fb L Tungsten, of 25cm⨯25cm⨯1m Mean Energy 10 4 3 2 1 -1 -2 10

10 10 10

10 10

ν ] / [ bin N etioInteractions Neutrino , and µ . Through LHC-Run3, about 20,000 muon ν 1 , ]. e − 100 GeV interacting in FASER 1 ν > ν 2 77 58 3 9 1545 2314 E . . + − 3 2 + − + − and 10.1 hadronic interaction lengths 21 0 1296 X 20439 Number of CC Interactions ], which is the fastest readout system at present. After processing to µ e τ 13 ¯ ¯ ¯ ν ν ν + + + e τ µ ν ν ν will be located on the collision axis directly in front of the m thick, that are poured onto both sides of a 200- ν µ leptons produced in the interactions, as shown in Figure 1 m at the 14-TeV LHC with an integrated luminosity of L = 150 fb τ × Left: Location of tunnels TI12 and TI18. The latter is a symmetric location on the other side of The expected number of neutrinos with , and . 1.35 m, and a total tungsten mass of 1.2 tons. The total length of the detector is 1.35 m, µ 1 25 cm , The neutrino event analysis will be based on readout of the full emulsion detectors by the Hy- The FASER × e × reconstruct the tracks in the fullto area locate of neutrino the interactions. emulsion We films, will we classify will the perform a systematic analysis the neutrino energies by combining topologicalstructing and the neutrino kinematical energy variables. is approximately The 30% resolution [ for recon- Table 1: per Track Selector system [ energies of the neutrinos.cm Here we assumecorrespond a to the benchmark range detector of predictions made obtained of from different tungsten Monte with Carlo generators. dimensions 25 FASER main detector to maximize the expected number of neutrino interactions. Figure Figure 2: ATLAS that was also considered forin FASER. Right: a The 1-ton energy tungsten spectrum detector of centered neutrinos on with the CC collision interactions axis of the beam at3. the FASER location. Detector design for LHC-Run3 (2021–2023) a view of the neutrino-detectorfilms module. interleaved with The 1-mm-thick detector tungsten plates. is The madelayers, emulsion of each film a is 70 composed repeated of structure twowhole of emulsion emulsion detector contains acm total of 1,000 emulsioncorresponding films, to 285 with radiation the lengths total volume of 25 cm Study of high-energy neutrinos in the FASER experiment at the LHC Run3 (2021–2023), seven sets of emulsionduring planned detectors technical will stops be roughly every installed, 20–50 withneutrinos, fb replacements 1,300 installed electron neutrinos, andTable 20 tau neutrinos will interact in the detector, as shown in PoS(EPS-HEP2019)409 Tomoko Ariga to the FASER main detector. will detect collider neutrinos of all with the main detector, as shown in ν ν ν to the FASER spectrometer, which is lo- ν 3 . This can be done by means of an interface detector, ν Plan of the detector upgrade to couple FASER shows prospects for cross-section measurements at the 14-TeV LHC in Run3 (150 5 Conceptual design of the detector structure and the topology of various neutrino events that can Figure 4: . If events in the emulsion detector can be matched to those in the interface detector, 4 Figure In addition, we are considering coupling FASER ) using a 1.2-ton tungsten/emulsion detector. FASER 1 − 4. Prospect for LHC-Run3 (2021–2023) three flavors and provide new measurements ofobserved their from neutrino any cross previous sections man-made source, at paving higheraddition, the energies we way than will to be search able for to new physics study effects. specific neutrino-interaction In processes, such as charm-associated fb a combined analysis will beneutrino possible, and providing anti-neutrino charge cross identificationrejection sections to of separately, enable the muon-initiated improvement measurements neutral-hadron-interaction of of background. the energy resolution, and an additional silicon trackerFigure layer that interfaces FASER Figure 3: be observed in the detector. cated immediately downstream of FASER Study of high-energy neutrinos in the FASER experiment at the LHC PoS(EPS-HEP2019)409 τ × ν 4 10 0.2) ± Tomoko Ariga ν 3 (center), and 10 µ FASER ν [GeV] E 2 (left), in 2021–23. Existing con- 10 τ DONUT e 1 of data. During this time, ν + ν − τ 1 ν f b −

0.8 0.6 0.4 0.2

ν ] / [ / σ GeV cm 10 E

- 2 38 4 10 has the capability to observe neutrinos ν IceCube is dominated by particles coming from the ν ν 3 10 ). These results demonstrate that emulsion de- 6 FASER 4 [GeV] E 2 10 μ ν + μ accelerators ν

0.8 0.6 0.4 0.2

ν [ / σ ] / 10 E GeV

detector will be able to identify both charm and beauty cm - 2 38 ν -nucleon CC cross-section sensitivity for 4 ν 10 ν 3 10 ’s estimated FASER ν [GeV] E 2 DONUT 10 , which agrees with the prediction from FLUKA simulations. The results show that the e FASER 2 E53 ν + e ν

0.6 0.4 0.2 0.8

ν ] / [ / σ GeV cm 10 E

- 2 38 At LHC-FASER, we will measure neutrino cross sections in the currently unconstrained en- In 2018 we performed measurements to check the detector environment. We installed emul- In addition, with the aims of possible neutrino detection and gamma-ray-background measure- fb/cm 4 ergy range between 350 GeV and 6 TeV. In particular, we will measure tau-neutrino cross section tectors can work in the actual environmentfrom and that the FASER LHC. Further detailed analysis is in progress. 6. Summary Figure 5: Study of high-energy neutrinos in the FASER experiment at the LHC neutrino interactions. The FASER on the basis of their decaya topology, sizable although number a of larger-scale beauty experiment events.the will way The be for study needed experiments of to at neutrinos observe physics. the at the energy LHC frontier will to be make a complementary milestone, measurements paving in neutrino flux of high-energy particles passing through FASER 5. Results from the 2018 test run sion detectors in the TI12 andThe TI18 tunnels flux along of the charged collision particles axis of measured the within beam 10 or the mrad line around of the sight. collision axis is (1.9 ments, we installed a 30-kg lead/tungstenwere emulsion-based placed neutrino on detector the in TI18. collision axis The modules of the beam and collected 12.5 fb (right) in Run 3 ofstraints the are 14-TeV shown LHC, in with gray. ansection. integrated The The luminosity solid black of error dashed bars 150 correspondthe curve to neutrino-production is statistical rates the uncertainties, corresponding theoretical the to shaded prediction thetors, regions range and for show of the the uncertainties predictions dashed average in obtained error DIS from bars cross different show their MC combination. genera- 10 ATLAS interaction point. we expected a few tens ofemulsion neutrino detector, interactions we to selected have several occurredthat vertex in had the candidates no detector. from charged By incoming a analyzing particle sub-sample the (see of Figure the analyzed data PoS(EPS-HEP2019)409 of data, 1 − Tomoko Ariga ). We collected 12.5 fb 6 5 Universality in Charged Current Neutrino Interactions, Phys. Rev. D 41 (1990) e ν - µ ν Left: The 30-kg pilot neutrino detector that was installed in the TI18 tunnel in 2018. It collected of data. Right: One of vertices found in the detector with no incoming charged track. The vertex 1 − LHC, arXiv:1908.02310 [hep-ex]. 2653. (2008) 052002. Earth absorption, Nature 551 (2017) 596. As a feasibility study, we performed a test run in 2018 at the proposed detector location, using The collaboration acknowledges assistance from many people, including the CERN Physics [1] FASER Collaboration, Detecting and Studying High-Energy Collider Neutrinos with FASER at the [2] C. Baltayet al., [3] DONuT Collaboration, Final tau-neutrino results from the DONuT experiment, Phys. Rev. D[4] 78 Particle Data Group Collaboration, Review of Particle[5] Physics, Phys.IceCube Rev. Collaboration, D Measurement 98 of no. the 3, multi-TeV (2018) neutrinocross 030001. section with IceCube using a 30-kg lead/tungsten emulsion-based neutrino detector (Figure Figure 6: 12.5 fb axis is compatible with the beam direction. at the highest energy ever. Forsten/emulsion LHC-Run3 (2021–2023), detector, we possibly are planning coupled toyield with deploy about a the 20,000 1.2-ton FASER tung- muon magnetic neutrinos,the spectrometer, 1,300 detector. which electron neutrinos, would and 20 tau neutrinos interacting in Beyond Colliders study group, theCERN LHC survey team, Tunnel the Region CERN Experiment STIsupported group, (TREX) in and working part the by group, CERN grants the Civil from Engineering the1179) group. Heising-Simons and Foundation This the (Grant Simons work Nos. Foundation was 2018-1135 (Grant and No.Grant 2019- 623683). No. This JP work is 19H01909 supported and by a JSPS research KAKENHI grant from the Mitsubishi Foundation. 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Connolly, Extracting the Energy-Dependent Neutrino-Nucleon Cross Section [7] OPERA Collaboration, Final Results of the OPERA Experiment on [8] Super-Kamiokande Collaboration, Measurement of the tau neutrino cross section in atmospheric [9] IceCube Collaboration, Measurement of Atmospheric Tau Neutrino Appearance with IceCube Study of high-energy neutrinos in the FASER experiment at the LHC [10] J. L. Feng, I. Galon, F. Kling, and S. Trojanowski, ForwArd Search[11] ExpeRiment atFASER the Collaboration, LHC, Letter Phys. of Intent for FASER: ForwArd SearchExpeRiment at the LHC, [12] FASER Collaboration, Technical Proposal for FASER: ForwArd SearchExpeRiment at the LHC, [13] M. Yoshimoto, T. Nakano, R. Komatani, and H. Kawahara, Hyper-track selector nuclear emulsion