Beyond the Standard Model physics case of far-forward searches at the LHC

Sebastian Trojanowski(strojanowski@camk.edu.pl)

AstroCeNT, Nicolaus Copernicus Astronomical CenterPolish Academy of Sciences

IRCHEP 2021Nov 10, 2021

In collaboration with: B. Batell, J.L. Feng, A. Ismail, I. Galon, F. Kling, R.M. Abraham, ...

MOTIVATION

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-- “leave no stone unturned”

-- cosmology (dark matter, inflation, bariogenesis…)

-- neutrino masses (GeV-scale heavy neutral leptons)

-- anomalies

LIGHT NEW PHYSICS LIGHT „KNOWN” PHYSICS

e.g. supersymmetryFASERν

High-energy collider neutrinos:-- first neutrino measurements at the LHC (candidate events) FASER collaboration: 2105.06197

-- TeV-energy neutrinos remain less explored-- any new tau neutrinos ντ highly welcome-- other possibilities: charm-associated ν interactions, new physics talk: Zahra Tabrizi

WIMPless miracleL. Roszkowski, E.M. Sessolo, ST, 1707.06277

LHC

M. Kaplinghat, S. Tullin, H.-B. Yu, 1508.03339

DM

DMSM

SM

Light long-lived particle

DM DD & ID

FOCUS of this talk is twofold: 1) search for light mediators, 2) search for light DM

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Hidden sector portals─ new „hidden” particles are SM singlets (but gauged U(1)B-L etc. are also considered)

─ interactions between the SM and „hidden” sector arise due to mixing through some SM portal

B. Patt, F. Wilczek, 0605188B. Batell, M. Pospelov, A. Ritz, 0906.5614

Renormalizable portals

PBC report, 1901.09966

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σinel ~ 75 mb, e.g., Nπ ~ 1017 at 3 ab-1 (for comparison σ ~ fb – pb, e.g., NH ~ 107 at 300 fb-1 in high-pT searches)

ATLAS IP FASER

FASER

(side tunnel)

J.L. Feng, I. Galon, F. Kling, ST, 1708.09389 FASER Collaboration: 1811:10243, 1812.09139 1908.02310, 2001.03073

Far-forward search at the LHC

p-p collision axis

new physics & neutrinos

VERY SCHEMATICALLY

ForwArd Search ExpeRiment (FASER) – small (~0.05 m3) and detector to be placed few hundred meters downstream the ATLAS IP

to harness large, currently „wasted” forward LHC cross section

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HL-LHC

Forward Physics Facility

FASER LoI & TP: 1811:10243, 1812.09139FASERν LoI & TP: 1908.02310, 2001.03073

Credit: John Osborne, Kincso Balazs, Jonathan Gall

Run 3main FASER -- cylindrical detector: L = 1.5 m, R = 10 cm, V = 0.05 m3, 150 fb-1 (Run 3)

Run 3 & HL-LHC plans

FPF whitepaper: 2109.10905

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p p

Light long-lived particle SMSM

Production (ATLAS IP, …) Decay (FASER, FPF)

Various production mechanisms:– meson decays (light & heavy)– bremsstrahlung– hard-scatterings,– Primakoff process,...

TANγ

Search for light mediators

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Soft pions going towards high-pT detectors: - produced LLPs would be too soft for triggers - large SM backgrounds

Hard pions highly collimated along the beam axissince their pT ~ ΛQCD e.g. for Eπ0 ≥ 10 GeV ~ 1.7% of π0s go towards FASER~ 24% of π0s go towards FASER 2

This can be compared to the angular size of both detectors with respect to the total solid angle of the forward hemisphere (2 π) :~ (2 × 10-6)% for FASER~ (2 × 10-4)% for FASER 2p p

ATLAS FASERπ0new particle

EPOS-LHC

θπ

J.L. Feng, I. Galon, F. Kling, ST, 1708.09389

Light new physics from pion decays

SELECTED SENSITIVITY REACH PLOTS

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DARK PHOTON DARK HIGGS BOSONHEAVY NEUTRAL LEPTON (TAU)

FASER Collaboration, 1811.12522

F. Kling, ST, 2105.07077

complementarity DM direct detection searchescomplex scalar DM with A’ med

Direct light DM detection at the LHC • We focus on LDM particles produced in the far-forward region of the LHC & their scattering in a distance detector

• This search is highly complementary to the traditional DM direct detection searches: – probe of relativistic interaction rates of LDM (DM energy ~ a few hundred GeV)

[collider-boosted DM] – the search is not sensitive to the precise abundance of χ DM component

(possible variations in cosmological scenario) [collider-produced DM]

credit B. Batell

DM relic targets

DM-electron

Benchmark scenarios: dark vector portal to Majorana or scalar DM

Relic target line: (thermal) Ωχh2 = 100% DM

- above relic target line: underabundant χ DM- below relic target line: too much χ DM (non-standard cosmology needed)

FLArE = Forward Liquid Argon Experiment(LArTPC, a la MiniBooNE)work on design: BNL, UCI,...

B. Batell, J.L. Feng, ST: 2101.10338

Scattering off nuclei: B. Batell, J.L. Feng, A. Ismail, F. Kling, R.M. Abraham, ST, 2107.00666 Leptophobic DM: B. Batell, J.L. Feng, M. Fieg, A. Ismail, F. Kling, R.M. Abraham, ST, 2111.xxxxx

Probing neutrino dipole portal See also talk: Joachim Kopp

Signature 1: upscattering (nuclei) + decay

Signature 3: upscattering (electrons)

γ

ν N

K. Jodlowski, ST, 2011.04751See also: A. Ismail, S. Jana, R.M. Abraham, 2109.05032

Signature 2: upscattering (nuclei) + prompt decay (high-energy)

Dark Z’ portal to heavy neutral leptons

ZD → N N

N e → N e~insensitive to U

τ

+ HNL-ν mixingE. Bertuzzo, S. Jana, P. A. Machado, R. Zukanovich Funchal, 1807.09877P. Ballett, S. Pascoli, and M. Ross-Lonergan, 1808.02915See also: Y. Jho, J. Kim, P. Ko, and S. C. Park, 2008.12598

Further interesting possibilities in less minimal scenarios:

- two sterile neutrinos & additional scalar “a”

P. Bakhti, Y. Farzan, S. Pascoli, 2010.16312

- secondary production of N in front of the detector, striking 4-muon signature

Less simplified case & DM indirect detection

A’ (secluded vector), h

D (scalar portal),

SB (compl. scal. DM)

SA (heavy [TeV] scal. DM)

V (very light vector)m<<GeV or massless V

K. Jodłowski, L. Roszkowski, ST, 2111.xxxxx

Conclusions• Far-forward BSM and neutrino physics at the LHC – new research program (Run 3: FASER, FASERν, SND@LHC, HL-LHC: Forward Physics Facility)

• LHC can be a factory of light unstable mediator and stable DM particles, most of high-energy such dark species will go down the beam pipe and avoid detection

• Light mediator and DM species: attractive target, WIMPless miracle, … simple portals, less-simplified models

• Multiple signatures possible: mediator decays, DM scatterings, BSM neutrino interactions, ...

• Forward Physics Facility: rich further experimental programs (neutrino physics, connections to QCD, cosmic rays,…)

• Efficient simulation tool: F. Kling, ST, 2105.07077