8th Forward Physics Facility Meeting

21 Jan 2025, 09:00 → 22 Jan 2025, 18:15 Europe/Zurich

6/2-024 - BE Auditorium Meyrin (CERN)

Photo of FPF8 in Jan 25:

Tuesday 21 January ¶

1 Opening Remarks from Organizers¶

Speaker: Jamie Boyd (CERN)

FPF8-Welcome.pdf

2 PBC and the FPF¶

Speaker: Gunar Schnell

FPF2025-PBC-Gunar.Schnell.pdf

3 New Results from FPF Pathfinder Experiments¶

Speaker: Michaela Queitsch-Maitland (University of Manchester (GB))

MQueitschMaitland_ForwardExperimentResults_FPF8.pdf

4 New Particles: Opportunities and Perspectives¶

Speaker: Maxim Pospelov

CERN2025.pdf

10:40 Coffee Break

5 Collider Neutrinos: Opportunities and Perspectives¶

Speaker: Felix Kling (DESY)

25-01-21-SM@FPF-1.pdf

6 Civil Engineering: Update and Status¶

Speaker: Tamara Alice Bud (CERN)

2025_8th FPF Meeting_Civil Engineering Aspects.pdf

2025_8th FPF Meeting_Civil Engineering Aspects.pptx

7 Integration: Update and Status¶

Speaker: Julien Prosic

FPF_Integration_8thFPFmeeting_21012025 - JPRv1.pdf

FPF_Integration_8thFPFmeeting_21012025 - JPRv1.pptx

12:45 Group Photo

13:00 Lunch

Parallel 1: New Physics Searches¶

Chair: Tomohiro Inada

Convener: Tomohiro Inada (Kyushu University, RCAPP)

8 Cosmic Millicharge Background: Probing Reheating Cosmology, String Theory, and GUTs in FORMOSA & FPF¶

We demonstrate that the searches for dark sector particles can provide probes of reheating scenarios, focusing on the cosmic millicharge background produced in the early universe. We discuss two types of millicharge particles (mCPs): either with, or without, an accompanying dark photon. These two types of mCPs have distinct theoretical motivations and cosmological signatures. We discuss constraints from the overproduction and mCP-baryon interactions of the mCP without an accompanying dark photon, with different reheating temperatures. We also consider the ΔNeff constraints on the mCPs from kinetic mixing, varying the reheating temperature. The regions of interest in which the accelerator and other experiments can probe the reheating scenarios are identified in this paper for both scenarios. These probes can potentially allow us to set an upper bound on the reheating temperature down to ∼10 MeV, much lower than the previously considered upper bound from inflationary cosmology at around ∼10^16 GeV. In addition, we find parameter regions in which the two mCP scenarios may be differentiated by cosmological considerations. Finally, we discuss the implications of dedicated mCP searches and future CMB-S4 observations.

Speaker: Yu-Dai Tsai (University of California, Irvine)

CmB.pdf

9 Dark photon pair production via off-shell dark Higgs at FASER¶

We consider a dark photon model in which the dark U(1) gauge symmetry is spontaneously broken by a vacuum expectation value of a new scalar boson. We focus on the ForwArd Search ExpeRiment (FASER) and calculate its sensitivity to the dark photon produced from the off-shell decay of the new scalar boson. It is found that the off-shell production extends the sensitivity region beyond the kinematical threshold of the on-shell decay of the scalar boson, and that the sensitivity region can be spanned to unexplored region. We also show the parameter space in which perturbative calculation is valid for the unitarity of an S matrix.

Speaker: Yohei Nakashima

8thFPFMeeting.pdf

10 Dark Vector Splitting Functions in Proton Bremsstrahlung¶

Experiments at the Forward Physics Facility are sensitive to new weakly coupled degrees of freedom across a broad mass range. Among the various production modes in proton-proton collisions, bremsstrahlung is particularly important for dark sector degrees of freedom with masses between 0.5 and 2.0 GeV, due to mixing with hadronic resonances. In this talk, I will revisit the calculation of dark vector production via initial state radiation in non-single diffractive scattering, using an improved treatment of the splitting functions and timeline electromagnetic form factors at the proton vertex, including the dipole coupling. Resonant enhancements impact the sensitivity above the $\rho /\omega$ mass range. The approach is benchmarked by applying an analogous calculation to model inclusive $\rho$-meson production. (based on 2409.09123)

Speaker: Saeid Foroughi-Abari

FPF8_Foroughi.pdf

11 Discovering Light Scalars Beyond Minimal Flavor Violation¶

We study a simple class of flavored scalar models, in which the couplings of a new light scalar to standard-model fermions are controlled by the flavor symmetry responsible for fermion masses and mixings. The scalar couplings are then aligned with the Yukawa matrices, with small but nonzero flavor-violating entries. D-meson decays are an important source of scalar production in these models, in contrast to models assuming minimal flavor violation, in which B and K decays dominate. We show that FASER2 can probe large portions of the parameter space of the models, with comparable numbers of scalars from B and D decays in some regions. If discovered, these particles will not only provide evidence of new physics, but they may also shed new light on the standard model flavor puzzle.

Speaker: Noam Burger

Flavor at FASER FPF meeting.pdf

16:20 Coffee Break

12 FASER-2 simulation and detector design performance document¶

This talk will aim to present and discuss the in-progress FASER-2 simulation and detector design performance document, which outlines the physics goals, detector requirements, simulation studies, and conceptual design scenarios for the proposed detector. The simulation framework developed uses Geant4 to describe detector geometry for sensitivity studies, along with the ACTS toolkit for track reconstruction and track alignment. These tools enable detector optimisation studies to compare various magnet and tracker configurations, which can be performed using key metrics including momentum resolution, sensitivity to BSM scenarios, and geometrical acceptance to other FPF experiments. This document aims to serve as a reference for the FPF collaboration and a possible resource for the European Strategy Process and further.

Speakers: Josh McFayden (University of Sussex), Olivier Salin (Université Paris-Saclay)

FASER_2_performance_note_draft.pdf

FASER-2_performance_note_FPF8_.pdf

13 DELIGHT and FOREHUNT: dedicated detectors at FCC-hh for light long-lived particles¶

Our efforts in searching for hints of new physics require close attention to the signatures of light particles arising in theories beyond the Standard Model (BSM) physics, as they could have eluded our searches. In many theories, these light BSM particles can have long lifetimes and are worth exploring. We focus on light long-lived particles (LLPs) coming from the decay of the discovered Higgs boson and $B$-mesons. Given the need to optimise the designs of dedicated LLP detectors for future colliders, we propose dedicated LLP detectors for the 100 TeV collider experiment, DELIGHT (Detector for long-lived particles at high energy of 100 TeV) and FOREHUNT (FORward Experiment for HUNdred TeV), and study their sensitivities for LLPs in the Higgs portal.

Speaker: Rhitaja Sengupta (BCTP and Physikalisches Institut der Universität Bonn, Germany)

fpf8_rhitaja.pdf

14 Unlocking the Inelastic Dark Matter Window with Vector Mediators¶

Despite the robust cosmological and astrophysical evidence confirming the existence of a non-baryonic matter component in the Universe, the underlying nature of Dark Matter (DM) remains a mystery. Among the several possible scenarios, light DM candidates thermally produced in the early Universe are especially interesting, since their abundance could be set via the standard freeze-out mechanism. Additionally, new light states can present a rich phenomenology and are attracting increasing attention due to recent experimental capabilities to probe dark sectors with feeble interactions. In particular, inelastic DM (iDM) candidates are an appealing option, since they can avoid cosmic microwave background (CMB) radiation bounds as well as indirect and direct detection searches. Although such models have been intensively studied in the literature, the usual scenario is to consider a secluded dark photon mediator. In this work, we consider the case of iDM with general vector mediators and explore the consequences of such a choice in the relic density computation, as well as for the cosmological and experimental bounds. We examine models with couplings to baryon and lepton number and show new viable parameter regions for inelastic dark matter models. Especially, anomaly-free gauge groups with non-universal couplings to leptons open new windows of the parameter space for thermal dark matter yet unexplored by experiments. We also provide a numerical Python library to compute the relic densities for user-defined gauge charges.

Speaker: Peter Reimitz

iDMQ_FPF.pdf

15 Exploring the LHC as a TeV Muon Beam Dump: Muonphilic Scalars at FASER¶

At FASER, neutrinos are predominantly produced from meson decays, which also result in an intense energetic flux of muons in the forward direction, which are regularly observed by FASER. So far, these muons are treated only as backgrounds to neutrino and new physics studies, and extensive effort is required to suppress them. Here, we consider the opposite scenario and use muons produced in the forward direction to produce new muonphilic scalars, which can then be searched for at the FASER detector. To minimize background for this search, we make use of an upgraded preshower component, which is expected be installed at FASER before the end of Run 3, and is capable of spatially resolving two energetic photons. We find that FASER and FASER2 can probe currently unconstrained regions of parameter space, including regions that can potentially explain the (g − 2)μ anomaly. This highlights the physics opportunities that the intense TeV muon beam at the LHC can bring.

Speaker: Roshan Mammen Abraham (University of California Irvine (US))

Muons_at_FASER_FPF8_RMA.pdf

Parallel 2: Neutrino Measurements¶

Conveners: Ken Ohashi (Universitaet Bern (CH)), Dr Umut Kose (ETH-Zurich)

Zoom link: https://cern.zoom.us/j/6344671012?pwd=Q3AyWEpuVTRoQURHb2I3TlU4a2QvUT09

16 Sweeper Magnet study¶

At the FPF site, the background muon levels are expected to be similar to those at the current FASERν site. While the FASERν experiment requires replacing the detector 2-3 times per year, we aim to reduce this to once per year for FASERν2. To achieve this, We studied possibilities to use a sweeper magnet to reduce the background muons to one-third.
In this study, I performed GEANT4 simulations using background muons generated by BDSIM to evaluate the magnet’s effects. The results demonstrate that the magnet can be effective depending on its placement. Furthermore, placing the magnet 370 meters from the ATLAS interaction point in the LHC tunnel and relocating the FPF to a position 700 meters away from the ATLAS IP was shown to reduce the background muons by up to 40%.

Speaker: Kohei Chinone (Chiba University (JP))

sweeper_magnet_fpf8.pdf

17 Optical readout option for the FLArE detector¶

I will present results obtained using the ARIADNE fast optical readout system and on how these inform the design of a FLArE optical LArTPC. A conceptual design of the FLArE TPC with a light readout plane and fast TimePix cameras will be discussed as well as a vacuum insulated cylindrical cryostat for this TPC option.

Speaker: k Mavrokoridis (University of Liverpool (GB))

ARIADNE+FPF_colab_mtg.pptx

18 Data-driven constraints on the prompt neutrino fluxes¶

The detection of TeV-energy neutrinos by the LHC far-forward detectors FASER/FASER$\nu$ and SND@LHC enables novel opportunities to validate theoretical predictions of of forward light particle production. In this work we present work in progress towards using the FASER and FPF event rate measurements to extract the LHC forward neutrino fluxes in a theory-agnostic manner by means of machine learning techniques. We parametrise these neutrino fluxes with neural networks and train them to available and projected FASER data, differential in neutrino energy and pseudo-rapidity. This way one can estimate the expected precision for this determination of the LHC neutrino fluxes and use this information to constrain models of forward $D$-meson production. This approach aims to demonstrate that FASER/FPF neutrino measurements provide an efficient data-driven approach to calibrate the prompt neutrino fluxes at neutrino telescopes such as IceCube and KM3NET.

Speakers: Jelle Koorn, Jukka John (Nikhef Theory Group)

Nikhef_Beamer_Template.pdf

19 Unravelling New Physics Signals at the HL-LHC with Low-Energy Constraints¶

Recent studies suggest that global fits of Parton Distribution Functions (PDFs) might inadvertently 'fit away' signs of new physics in the high-energy tails of the distributions measured at the high luminosity programme of the LHC (HL-LHC). This could lead to spurious effects that might conceal key BSM signatures and hinder the success of indirect searches for new physics. In this talk, I describe how future deep-inelastic scattering (DIS) measurements at the Electron-Ion Collider (EIC), and at CERN via FASERν and SND@LHC at LHC Run III, and the future neutrino experiments to be hosted at the proposed Forward Physics Facility (FPF) at the HL-LHC, provide complementary constraints on large-x sea quarks. These constraints are crucial to mitigate the risk of missing key BSM signals, by enabling precise constraints on large-x PDFs through a 'BSM-safe' integration of both high- and low-energy data, which is essential for a robust interpretation of the high-energy measurements.

Speaker: Elie Hammou

FPF8_Elie_Hammou.pdf

16:20 Coffee Break

20 Discovering neutrino tridents at FASERν2¶

Neutrino trident production of di-lepton pairs is well recognized as a sensitive probe of both electroweak physics and physics beyond the Standard Model. Although a rare process, it could be significantly boosted by such new physics, and it also allows the electroweak theory to be tested in a new regime. We demonstrate that the forward neutrino physics program at the Large Hadron Collider offers a promising opportunity to measure for the first time, dimuon neutrino tridents with a statistical significance exceeding $5\sigma$, improving on the previous claims at the $\sim 3\sigma$ level by the CHARM-II and CCFR collaborations while accounting for additional backgrounds later identified by the NuTeV collaboration. We present predictions for various proposed experiments and outline a specific experimental strategy to identify the signal and mitigate backgrounds, based on ``reverse tracking'' dimuon pairs in the FASER$\nu$2 detector. We also discuss prospects for constraining beyond Standard Model contributions to neutrino trident rates at high energies.

Speaker: Dr Toni Makela (University of California, Irvine)

Discovering_neutrino_tridents_at_FASERv2.pdf

21 Tau polarization effects in ντ/ν¯τ - tungsten interactions at the LHC energies¶

Considering that the study of neutrino - nucleus interactions with incident neutrino energy ranges in the GeV - TeV range is feasible at the Large Hadron Collider, we investigate in this work the degree of polarization $\mathcal{P}$ of the (anti) tau lepton produced in (anti) tau neutrino - tungsten interactions. In this study we also investigate the impact of the tau polarization on the pions generated in its decay. In particular, we estimate the associated pion momentum, energy and angular distributions. The contribution of the $F_5$ structure function to these observables is also investigated. Our results indicate that the pion properties are sensitive to the tau polarization state as well as to the magnitude of $F_5$.

Speaker: Reinaldo Francener (Universidade Estadual de Campinas)

Presentation.pdf

22 FORTVNE: scintillator bar-tungsten detector for FASER upgrades¶

We discuss results from simulations and CNNs to distinguish neutrino CC and NC events with a scintillator bar-tungsten detector in the FASER location.

Speakers: Dr Wenjie Wu (University of California, Irvine), Wenjie Wu (University of California, Irvine)

20250121@FORTVNE-FPF8.pdf

23 FASERCal: High-Energy Neutrino Measurements at FASER¶

To address the challenges of higher muon background in addition to the increase in luminosity in LHC Run 4, ETH Zurich proposes a novel detector system which aims to provide highly granular 3D tracking, calorimetry and muon identification with a design that is compact, modular and scalable. The proposed FASERCal detector is designed to detect both charged-current and neutral-current neutrino interactions. FASERCal will consist of 15 modular units, each composed of 20 layers of optically-isolate 1 cm${}^3$ plastic scintillator cubes inspired by the recent upgrade of the T2K near detector and 2 layers of high-resolution pixel detectors. Following the modules, the RearCal will provide an electromagnetic calorimeter containing 25 radiation lengths. Finally, the MuonTag component will consist of absorber and scintillator to provide identification for muons passing through the calorimeter.

Speaker: Charlotte Cavanagh (ETH Zurich (CH))

CCavanagh_FASERCal_FPF8_210125.pdf

19:00 Workshop Dinner

Wednesday 22 January ¶

24 FASERnu2¶

Speaker: Tomoko Ariga (Kyushu University (JP))

20250122_tariga_FASERnu2_FPF8.pdf

20250122_tariga_FASERnu2_FPF8.pptx

25 FASER2¶

Speakers: Alan Barr (University of Oxford (GB)), Alan Barr (University of Oxford (GB))

FASER2-2025-01-22.pdf

FASER2-2025-01-22.pptx

26 FORMOSA¶

Speaker: Juan Salvador Tafoya Vargas (University of California Davis (US))

FORMOSA - 8th FPF meeting.pdf

10:30 Coffee Break

27 FLArE Simulations¶

Speaker: Matteo Vicenzi (Brookhaven National Laboratory (US))

20250122_MV_FPF8_FLArE_simulations.pdf

28 FLArE Design¶

Speaker: Steven Linden

FLArE - FPF8.pdf

Installing the FLArE cryostat and TPCs-Final.pptx.pdf

29 LHC neutrinos in Surface Detectors¶

Speaker: Dr Toni Makela (University of California, Irvine)

250122_LHC_neutrinos_in_surface_detectors.pdf

12:30 Lunch

30 Status of Neutrino Interactions with GENIE¶

Speaker: Alfonso Andres Garcia Soto (IFIC)

fpf.pdf

31 An event generator for Lepton-Hadron Deep Inelastic Scattering at NLO+PS with POWHEG including mass effects¶

Speaker: Giovanni Limatola

FPF_limatola.pdf

32 An event generator for neutrino-induced Deep Inelastic Scattering and applications to neutrino astronomy¶

Speaker: Rhorry Gauld (MPP Munich)

FPF_NuPowheg.pdf

33 A Phenomenological Analysis of LHC Neutrino Scattering at NLO Accuracy Matched to Parton Showers¶

Speaker: Juan Rojo Chacon (Nikhef National institute for subatomic physics (NL))

rojo-FPF8-POWHEGnu.pdf

34 DIscussion¶

Speaker: Felix Kling (DESY)

FPF8.pdf

15:30 Coffee Break

35 ESPPU: Document and Plans¶

Speakers: Alan Barr (University of Oxford (GB)), Alan Barr (University of Oxford (GB)), Albert De Roeck (CERN), Felix Kling (DESY), Jamie Boyd (CERN), Juan Rojo Chacon (Nikhef National institute for subatomic physics (NL))

The EPPSU case.pdf

The EPPSU case.pptx

36 Timeline, Funding, Project Management¶

Speakers: Albert De Roeck (CERN), Jamie Boyd (CERN), Milind Vaman Diwan (Brookhaven National Laboratory (US))

rd-funding.pdf