Experimental searches for supersymmetry (SUSY) are entering a new era. The failure to observe signals of sparticle production at the large hadron collider (LHC) has eroded the central motivation for SUSY breaking at the weak scale. However, String Theory requires SUSY at the fundamental scale $$M_s$$ and hence SUSY could be broken at some high scale below $$M_s$$ . Actually, if this were the case, the lack of experimental evidence for low-energy SUSY could have been anticipated, because most stringy models with high-scale SUSY breaking predict that sparticles would start popping up above about 10 TeV, well beyond the reach of current LHC experiments. We show that using next generation LHC experiments currently envisioned for the Forward Physics Facility (FPF) we could search for signals of neutrino-modulino oscillations to probe models with string scale in the grand unification region and SUSY breaking driven by sequestered gravity in gauge mediation. This is possible because of the unprecedented flux of neutrinos to be produced as secondary products in LHC collisions during the high-luminosity era and the capability of FPF experiments to detect and identify their flavors.

United States

Luis Anchordoqui

Thailand

France

Ignatios Antoniadis

Karim Benakli

Jules Cunat

Germany

Dieter Lüst

Susy at the FPF

We present a set of example models in which the Standard Model (SM) symmetry group is extended by a new abelian symmetry. This additional symmetry appears anomalous in the effective low-energy theory; however, the anomalies cancel out when massive chiral fermions not present in the effective low-energy theory are taken into account. These chiral fermions under the new abelian gauge group, are chosen to be vector-like under the SM symmetries, and reside in the same representations as quarks and leptons. This allows us to quantitatively determine the magnitude of tree-level interactions between three vector bosons induced in low-energy effective field theory by the integration of chiral heavy fermions. We also examine the perturbativity constraints of the theory and the ultraviolet cut-off. We conclude by highlighting possible extensions of our work.

Belgium

Austria

Pascal Anastasopoulos

Cyprus

François Rondeau

Anomalous U(1) extension of the Standard Model

We make use of swampland conjectures to explore the phenomenology of neutrino-modulino mixing in regions of the parameter space that are within the sensitivity of experiments at the CERN's Forward Physics Facility (FPF). We adopt the working assumption of Dirac mass terms which couple left- and right-handed neutrinos. We further assume that the 3 right-handed neutrinos are 0-modes of bulk 5-dimensional states in the dark dimension, a novel scenario which has a compact space with characteristic length-scale in the micron range that produces a natural suppression of the 4-dimensional Yukawa couplings, yielding naturally light Dirac neutrinos. We formulate a specific realization of models with high-scale supersymmetry breaking that can host a rather heavy gravitino (<math><msub><mrow><mi>m</mi></mrow><mrow><mn>3</mn><mo>/</mo><mn>2</mn></mrow></msub><mo>∼</mo><mn>250</mn><mspace width="0.25em"></mspace><mrow><mi>TeV</mi></mrow></math>) and a modulino with mass scale (<math><msub><mrow><mi>m</mi></mrow><mrow><mn>4</mn></mrow></msub><mo>∼</mo><mn>50</mn><mspace width="0.25em"></mspace><mrow><mi>eV</mi></mrow></math>) within the FPF discovery reach.

Luis A. Anchordoqui

United Kingdom

Searching for neutrino-modulino oscillations at the Forward Physics Facility

We develop in components the superspace action obtained in [1] describing the first massive level of the open charged superstring in a flat four-dimensional spacetime. In the absence of an electromagnetic background, we show how the Rarita-Schwinger and Fierz-Pauli Lagrangians are retrieved for spin-3/2 and 2, respectively. We then write different forms of the action in the presence of the electromagnetic background. The resulting equations of motion describe the propagation of fields of charged spin-3/2 and spin-1/2 on the one hand, and spin-2, 1 and 0 on the other.

Brazil

Cassiano Daniel

Wenqi Ke

Spin-3/2 and spin-2 charged massive states in a constant electromagnetic background

We derive fully explicit equations of motion, and the associated set of constraints, describing the propagation in a flat space-time of a charged spin-3/2 massive state in a constant electromagnetic background. For this purpose, we provide the Lagrangian for the physical fermionic fields in the first massive level of the open superstring. We first write a compact Lagrangian, allowing a simple derivation of the equations of motion and constraints. Then another one is given that yields directly a decoupled system of equations, though the fields of different spins look coupled at the level of the Lagrangian.

Cassiano A. Daniel

Open superstring first mass level effective Lagrangian: Massive spin-3/2 fields in an electromagnetic background

Minimal coupling leads to problems such as loss of causality if one wants to describe charged particles of spin greater than one propagating in a constant electromagnetic background. Regge trajectories in string theory contain such states, so their study may allow us to investigate possible avenues to remedy the pathologies. We present here two explicit forms, related by field redefinitions, of the Lagrangian describing the bosonic states in the first massive level of open superstrings in four dimensions. The first one reduces, when the electromagnetic field is set to zero, to the Fierz-Pauli Lagrangian for the spin-2 mode. The second one is a more compact form which simplifies the derivation of a Fierz-Pauli system of equations of motion and constraints.

Open superstring first mass level effective Lagrangian: Massive spin-2 in an electromagnetic background

We consider a set of elementary compactifications of  $$D+1$$  <math> <mrow> <mi>D</mi> <mo>+</mo> <mn>1</mn> </mrow> </math>   to D spacetime dimensions on a circle: first for pure general relativity, then in the presence of a scalar field, first free then with a non minimal coupling to the Ricci scalar, and finally in the presence of gauge bosons. We compute the tree-level amplitudes in order to compare some gravitational and non-gravitational amplitudes. This allows us to recover the known constraints of the U(1), dilatonic and scalar weak gravity conjectures in some cases, and to show the interplay of the different interactions. We study the KK modes pair-production in different dimensions. We also discuss the contribution to some of these amplitudes of the non-minimal coupling in higher dimensions for scalar fields to the Ricci scalar.

Carlo Branchina

Gaëtan Lafforgue-Marmet

Newton versus Coulomb for Kaluza–Klein modes

We investigate the conditions for alignment in Dirac Gaugino models with minimal matter content. This leads to several scenarios, including an aligned Dirac Gaugino NMSSM that allows a light singlet scalar. We then investigate the compatibility of minimal Dirac Gaugino models with an enhanced W boson mass, using a new precise computation of the quantum corrections included in the code SARAH 4.15.0.

Mark Goodsell

Pietro Slavich

W boson mass in minimal Dirac gaugino scenarios

We show that experiments at the Forward Physics Facility, planned to operate near the ATLAS interaction point during the LHC high-luminosity era, will be able to probe predictions of Little String Theory by searching for anomalous <math><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></math> gauge bosons living in the bulk. The interaction of the abelian broken gauge symmetry with the Standard Model is generated at the one-loop level through kinetic mixing with the photon. Gauge invariant generation of mass for the <math><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></math> gauge boson proceeds via the Higgs mechanism in spontaneous symmetry breaking, or else through anomaly-cancellation appealing to Stückelberg-mass terms. We demonstrate that FASER2 will be able to probe string scales over roughly two orders of magnitude: <math><msup><mrow><mn>10</mn></mrow><mrow><mn>5</mn></mrow></msup><mo>≲</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>s</mi></mrow></msub><mo>/</mo><mrow><mi>TeV</mi></mrow><mo>≲</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>7</mn></mrow></msup></math>.

Sweden

Anomalous (1) Gauge Bosons and String Physics at the Forward Physics Facility

Constructing a consistent four-dimensional Lagrangian for charged massive higher-spin fields propagating in an electromagnetic background is an open problem. In 1989, Argyres and Nappi used bosonic open string field theory to construct a Lagrangian for charged massive spin-2 fields in a constant electromagnetic background. In this paper, we use the four-dimensional hybrid formalism for open superstring field theory to construct a supersymmetric Lagrangian for charged massive spin-2 and spin-3/2 fields in a constant electromagnetic background. The hybrid formalism has the advantage over the RNS formalism of manifest   <math> <mi>N</mi> </math>  $$ \mathcal{N} $$  = 1 d=4 spacetime supersymmetry so that the spin-2 and spin-3/2 fields are combined into a single superfield and there is no need for picture-changing or spin fields.