Results from the FASER experiment at the LHC�

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Akitaka Ariga

University of Bern / Chiba University

On behalf of the FASER Collaboration

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FASER physics concept

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Strongly interacting massive particles

Let’s put small detector on the beam axis!

The FASER experiment

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

LHC tunnel

Neutrinos and LLPs

LHC magnets

p-p collision at ATLAS

Neutral hadrons

Charged particles

FORWARD SEARCH EXPERIMENT AT THE LHC

FASER detector

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

• Small, inexpensive detector
• 10 cm radius
• 7 m long

(ariXiv:2207.11427)

Air-core magnets

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Calorimeter

Pre-shower

Tracking spectrometer

Decay volume

Veto

IFT

Results from the FASER experiment

BSM

• Dark photon with 2022 data, Moriond 2023 + Updates
• 10.1016/j.physletb.2023.138378

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• Axion-Like-Particles (ALPs) with 2022, 2023 data
• Preliminary result

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

2018

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2019

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2020

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2021

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2022

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2023

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2024

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Run 2

Run 3

Updated

Dark photon search

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Simple and robust A’ 🡪 e⁺e^- selection, optimised for discovery

No veto signal, two tracks and E(calo) > 500 GeV

Dark photon produced in decays of forward mesons 🡪 decay into fermion pairs in the detector

Production

Decay

Dark photon results

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

• 27 fb^-1 in 2022 run
• Total background prediction (dominated by neutrinos)

N_BG= (2.3 ± 2.3) x 10^-3

• No events in unblinded signal region

Dark Photon B-L Gauge boson

Same dataset as shown last year, but now published: 10.1016/j.physletb.2023.138378

Axion-like Particles (ALPs) search

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

• No signal in 5 veto counters and timing scintillators
• Evidence of EM shower in pre-shower counters
• > 1.5 TeV in calorimeter
• In time with LHC collision

Selection

4-m-long decay volume

production

decay

ALPs results

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Public documentation to be released soon

Event display of 1 selected event: “ALPtrino” event

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Pre-shower

Calorimeter

1.6 TeV

No signal in veto and timing scintillators

Waveforms of PMTs (ns-mV)

Neutrino studies in FASER

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

2402.13318

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Spectrometer to measure particle momenta

Shown in Moriond 2023, now published in Phys. Rev. Lett. 131, 031801 (2023)

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Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Emulsion detectors: �3D tracking device with 50 nm precision

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Cross-sectional view

Emulsion layer

200 nm

Emulsion film

Residual from fitted track

σ = 50 nm

AgBr crystal = detector

10¹⁴ channels/film or 10¹⁴ channels/cm³

Antiproton annihilation in emulsion

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Glass base

1 mm

Emulsion layer

(50 micron)

antiproton

200 microns

Emulsion layer

(50 micron)

Antiproton annihilation taken in AEgIS 2012

3D view of emulsion detector

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

150 μm x 120 μm x 50 μm

• 3D high resolution hits
• Work as tracker
• dE/dx proportional to darkness (Number of grains)

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Readout

Alignment

Track reconstruction

Vertex reconstruction

Physics analysis

Development

Exposure

Assembly

Film production

Disassembling

Japan

Japan

CERN

Offline analysis

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Muons at FASER site

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Angular distribution (Data)

0.5 fb^-1

10 fb^-1

From IP

From backward

FASER preliminary

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

BG muon angular distribution (Data)

20 mrad

FASER Preliminary

Electron neutrino observation in FASERν

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

• Vertex with 11 tracks
• 615 µm inside tungsten

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• e-like track from vertex
• Single track for 2X₀
• Shower max @ 7.8Χ₀
• θ_e = 11 mrad to beam

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• Back-to-back topology
• 175° between e & rest

Beam View

Side View

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Beam view

Side view

• Vertex with 11 tracks
• 615 µm inside tungsten

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• e-like track from vertex
• Single track for 2X₀
• Shower max @ 7.8Χ₀
• θ_e = 11 mrad to beam

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• Back-to-back topology
• 175° between e & rest

Try an interactive display! http://physics.s.chiba-u.ac.jp/lepp/pika-nu.html

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

arXiv: 2403.12520

Summary of the event detection

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

arXiv: 2403.12520

Electron energy

Muon

momentum

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Beam view

Beam view

Rotated view

1.5 TeV

360 GeV

First cross section measurements at TeV energies

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

arXiv: 2403.12520

Relative measurement wrt theoretical curve

Large uncertainty from neutrino flux

L=9.5 fb^-1, m=128.6 kg

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Neutrino flux

neutrino cross section

Neutrino flux

uncertainty

FASER’s result = interaction rates

FASER’s interaction rate measurements

Precise knowledge of flux

Neutrino cross section measurements

SM neutrino cross section is decent

Neutrino flux measurement

• Hadron production models
• External validation data

Cross section

uncertainty

• Assuming LFU is valid

• Test Lepton Flavor Universality
• Search for new interactions

LHC’s forward neutrino beam… Is it special?

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

IceCube: 100 PeV fixed target

Large-x

Small-x

forward beam

Sensitive to QCD studies; small-𝑥 factorization, probe intrinsic charm, and prompt neutrinos.

Neutrinos = proxy of forward hadron production

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

FASER’s flux model recommendation:

• https://arxiv.org/abs/2402.13318

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

EPOS-LHC for light hadrons

POWHEG+PYTHIA for charm

What external data can be used?

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Hadron production at the LHC

FASER data can be inputs for cosmic ray physics

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

IceCube’s prompt atmospheric neutrinos limits

K.H. Kampert, M. Unger, Astropart. Phys. 35, 660 (2012),

H.P. Dembinski et al., EPJ Web Conf. 210, 02004 (2019)

LFU test in heavy-flavor-associated channels

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

LHC Schedule

• LHC Run-3 will start in 2022, aiming to double the integrated luminosity
• HL-LHC, starting in 2027, will deliver 10 times more integrated luminosity

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Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Forward experiment in HL-LHC

Physics run will start in 2022 (~150 fb^-1)

BG measurement, pilot run in 2018

Forward Physics Facility at the HL-LHC

HL-LHC provides x20 proton collisions

Extending sensitivities for new particle searches and neutrino physics by two orders of magnitude

Wide discussion in periodical workshops indico.cern.ch/event/1022352

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Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

UJ12

SPS

ATLAS

UJ18

CERN GIS

LHC

FASER2

LAr

MilliQan

65m

Option 1:

Extend existing tunnel

Option 2:

New shaft and hall

Forward Physics Facility (FPF) at the HL-LHC

BSM particles can be detected in various ways

• Giving access to wide range of models

Neutrinos can be used to search for BSM effects

• Production
• Propagation
• Interaction

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There was an interesting IceCube talk by Lu Lu’s talk in FPF7

Please also listen to Jonathan Feng about FPF in IceCube CM in Sep

Akitaka Ariga, DMNet, Sep 2023

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2023/3/15

Meetings and Documentation

FPF workshop series:

FPF1, FPF2, FPF3, �FPF4, FPF5, FPF6

FPF 7^th workshop (2024/2)

https://indico.cern.ch/event/1358966/

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FPF Paper:

2109.10905

~75 pages, ~80 authors

Snowmass Whitepaper:

2203.05090

~450 pages, ~250 authors

_{FASER Collaboration, 1811.12522 (2018)}

Detectors at the FPF

Akitaka Ariga, DMNet, Sep 2023

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2023/3/15

AdvSND

electronic detector �near detector at η~5 �far detector at FPF

FLArE�liquid noble gas detector

FASERv2�20 tons emulsion neutrino detector�followed by FASER spectrometer

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FASER2

LLP searches�

FORMOSA�Milli charged particle

Summary

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

L=9.5 fb^-1, m=128.6 kg

FASER INSTITUTIONS

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2024/4/18

96 collaborators, 26 institutions, 10 countries

International laboratory covered by a cooperation agreement with CERN

Backup

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2024/4/18

FASER detector

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

LHC forward beam

Emulsion-based neutrino target

Akitaka Ariga, DMNet, Sep 2023

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2023/3/15

Emulsion films produced in Japan

Silver bromide crystals

Anti proton annihilation in emulsion

Nagoya’s emulsion technology

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Wide range of projects, many more

Emulsion gel production

Film production

Emulsion read-out (scanning)

Muography

CERN Emulsion Facility

Akitaka Ariga, DMNet, Sep 2023

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2023/3/15

Asbestos floor removed, new shiny floor, modern climate control, card lock system…

Temperature controlled developer bath

Development room

13 x 100L tanks

Easy disposal system

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Development timer

Film drying

Disposal

Microscope

Event selection

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Expected neutrino spectra for FASER and SND@LHC

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Expected CC interactions with 150 fb^-1

10.1103/PhysRevD.104.113008

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Neutrinos = proxy of forward hadron production

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Heavy-flavor-associated channels

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Sterile neutrino oscillation

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2024/4/18

Background for ALPs

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2024/4/18

Neutrino control region

(Large EM in calo, but little in pre-shower)

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

ALPS backgrounds

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2024/4/18

ALPs acceptance, efficiency

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

New NA62 result

arXiv:2312.12055

Future sensitivity

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

CERN-LHCC-2023-009

https://cds.cern.ch/record/2882503?ln=en

Discussion on angular distribution of wide range

Akitaka Ariga, FASER, IceHap seminar

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2024/4/18

0.11 rad

LOS

The line connecting the positions of Q15, Q16, and FASER

Q16

FASERν

Q15

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2024/4/18

Lu Lu FPF7

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2024/4/18

Lu Lu FPF7

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