Light dark matter particles may be produced in electron and positron beam dumps of the International Linear Collider (ILC). We propose an experimental setup to search for such events, the Beam-Dump eXperiment at the ILC (ILC-BDX). The setup consists of a muon shield placed behind the beam dump, followed by a multi-layer tracker and an electromagnetic calorimeter. The calorimeter can detect electron recoils due to elastic scattering of dark matter particles produced in the dump, while the tracker is sensitive to decays of excited dark-sector states into the dark matter particle. We study the production, decay and scattering of sub-GeV dark matter particles in this setup in several models with a dark photon mediator. Taking into account beam-related backgrounds due to neutrinos produced in the beam dump as well as the cosmic-ray background, we evaluate the sensitivity reach of the ILC-BDX experiment. We find that the ILC-BDX will be able to probe interesting regions of the model parameter space and, in many cases, reach well below the relic target.

Japan

Kento Asai

Hungary

Taiwan

Sho Iwamoto

United States

Maxim Perelstein

Yasuhito Sakaki

China

Daiki Ueda

Sub-GeV dark matter search at ILC beam dumps

In this paper we explore the possibility of explaining the muon g − 2 anomaly in various types of supersymmetric extensions of the Standard Model. In particular, we investigate and compare the phenomenological constraints in the MSSM with stable neutralino and the other types of scenarios where the neutralino is unstable. For the latter case we study the Gauge Mediated SUSY Breaking (GMSB) scenario with very light gravitino and the UDD-type R-Parity Violating (RPV) scenario. In the MSSM with stable neutralino, the parameter region favoured by the (g − 2) μ  is strongly constrained by the neutralino relic abundance and the dark matter direct detection experiments, as well as by the LHC searches in the lepton plus missing transverse energy channel. On the other hand, the scenarios without stable neutralino are free from the dark matter constraints, while the LHC constraints depends strongly on the decay of the neutralino. We find that in GMSB the entire parameter region favoured by the muon g − 2 is already excluded if the Next Lightest SUSY Particle (NLSP) is the neutralino. In the GMSB scenario with a stau NSLP and in the RPV scenario, LHC constraints are weaker than the stable neutralino case and a larger region of parameter space is available to fit the (g − 2) μ  anomaly.

Poland

Manimala Chakraborti

South Africa

Jong Kim

Rafał Masełek

Kazuki Sakurai

Supersymmetric explanation of the muon g – 2 anomaly with and without stable neutralino

In this letter, we show that the wino-Higgsino dark matter (DM) is detectable in near future DM direct detection experiments for almost all consistent parameter space in the spontaneously broken supergravity (SUGRA) if the muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math> anomaly is explained by the wino-Higgsino loop diagrams. We also point out that the present and future LHC experiments can exclude or confirm this SUGRA explanation of the observed muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math> anomaly.

Tsutomu T. Yanagida

Norimi Yokozaki

Wino-Higgsino dark matter in MSSM from the − 2 Anomaly

We study capability of the ILC beam dump experiment to search for new physics, comparing the performance of the electron and positron beam dumps. The dark photon, axion-like particles, and light scalar bosons are considered as new physics scenarios, where all the important production mechanisms are included: electron-positron pair-annihilation, Primakoff process, and bremsstrahlung productions.

New physics searches at the ILC positron and electron beam dumps

We consider gauged U(1) extensions of the standard model of particle physics with three right-handed sterile neutrinos and a singlet scalar. The neutrinos obtain mass via the type I seesaw mechanism. We compute the one-loop corrections to the elements of the tree-level mass matrix of the light neutrinos and show explicitly the cancellation of the gauge-dependent terms. We present a general formula for the gauge-independent, finite one-loop corrections for arbitrary number new U(1) groups, new complex scalars, and sterile neutrinos. We estimate the size of the corrections relative to the tree-level mass matrix in a particular extension, the superweak model.

Timo J. Kärkkäinen

Zoltán Péli

Zoltán Trócsányi

One-loop corrections to light neutrino masses in gauged U(1) extensions of the standard model

The Fermilab Muon g − 2 collaboration recently announced the first result of measurement of the muon anomalous magnetic moment (g − 2), which confirmed the previous result at the Brookhaven National Laboratory and thus the discrepancy with its Standard Model prediction. We revisit low-scale supersymmetric models that are naturally capable to solve the muon g − 2 anomaly, focusing on two distinct scenarios: chargino-contribution dominated and pure-bino-contribution dominated scenarios. It is shown that the slepton pair-production searches have excluded broad parameter spaces for both two scenarios, but they are not closed yet. For the chargino-dominated scenario, the models with   <math> <msub> <mi>m</mi> <msub> <mover> <mi>μ</mi> <mo>˜</mo> </mover> <mi>L</mi> </msub> </msub> <mo>≳</mo> <msub> <mi>m</mi> <msubsup> <mover> <mi>χ</mi> <mo>˜</mo> </mover> <mn>1</mn> <mo>±</mo> </msubsup> </msub> </math>  $$ {m}_{{\tilde{\mu}}_{\mathrm{L}}}\gtrsim {m}_{{\tilde{\chi}}_1^{\pm }} $$  are still widely allowed. For the bino-dominated scenario, we find that, although slightly non-trivial, the region with low tan β with heavy higgsinos is preferred. In the case of universal slepton masses, the low mass regions with   <math> <msub> <mi>m</mi> <mover> <mi>μ</mi> <mo>˜</mo> </mover> </msub> </math>  $$ {m}_{\tilde{\mu}} $$  ≲ 230 GeV can explain the g − 2 anomaly while satisfying the LHC constraints. Furthermore, we checked that the stau-bino coannihilation works properly to realize the bino thermal relic dark matter. We also investigate heavy staus case for the bino-dominated scenario, where the parameter region that can explain the muon g − 2 anomaly is stretched to   <math> <msub> <mi>m</mi> <mover> <mi>μ</mi> <mo>˜</mo> </mover> </msub> </math>  $$ {m}_{\tilde{\mu}} $$  ≲ 1.3 TeV.

Motoi Endo

Koichi Hamaguchi

Teppei Kitahara

Supersymmetric interpretation of the muon g – 2 anomaly

The sensitivity of future electron-proton colliders, the LHeC and FCC-eh, to weakly produced supersymmetric particles is evaluated in this paper. Supersymmetric scenarios where charginos (<math><msubsup><mover><mi>χ</mi><mo>˜</mo></mover><mn>1</mn><mo>±</mo></msubsup></math>) and neutralinos (<math><mrow><msubsup><mrow><mover><mrow><mi>χ</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mn>1</mn></mrow><mrow><mn>0</mn></mrow></msubsup></mrow></math> and <math><mrow><msubsup><mrow><mover><mrow><mi>χ</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mn>2</mn></mrow><mrow><mn>0</mn></mrow></msubsup></mrow></math>) are nearly degenerate in mass are considered. Two sets of models, which differ in the mass of sleptons (<math><mover><mo>ℓ</mo><mo>˜</mo></mover></math>), are studied. Under the hypothesis that slepton masses are at the multi-TeV scale (“decoupled” scenario), the production processes for charginos and neutralinos at <math><mi>e</mi><mi>p</mi></math> colliders, <math><mi>p</mi><msup><mi>e</mi><mo>−</mo></msup><mo>→</mo><mi>j</mi><msup><mi>e</mi><mo>−</mo></msup><mover><mi>χ</mi><mo>˜</mo></mover><mover><mi>χ</mi><mo>˜</mo></mover></math> with <math><mover><mi>χ</mi><mo>˜</mo></mover><mo>=</mo><msubsup><mover><mi>χ</mi><mo>˜</mo></mover><mn>1</mn><mn>0</mn></msubsup></math>, <math><msubsup><mover><mi>χ</mi><mo>˜</mo></mover><mn>1</mn><mo>±</mo></msubsup></math> or <math><msubsup><mover><mi>χ</mi><mo>˜</mo></mover><mn>2</mn><mn>0</mn></msubsup></math>, are considered. For the models where slepton masses are above but close to <math><msubsup><mover><mi>χ</mi><mo>˜</mo></mover><mn>1</mn><mo>±</mo></msubsup></math>, <math><msubsup><mover><mi>χ</mi><mo>˜</mo></mover><mn>2</mn><mn>0</mn></msubsup></math> masses (“compressed” scenario), contributions from the processes <math><mi>p</mi><msup><mi>e</mi><mo>−</mo></msup><mo>→</mo><mi>j</mi><mover><mi>χ</mi><mo>˜</mo></mover><msubsup><mover><mi>e</mi><mo>˜</mo></mover><mi>L</mi><mo>−</mo></msubsup></math> and <math><mi>j</mi><mover><mi>χ</mi><mo>˜</mo></mover><mover><mi>ν</mi><mo>˜</mo></mover></math> followed by the decays <math><msubsup><mover><mi>e</mi><mo>˜</mo></mover><mi>L</mi><mo>−</mo></msubsup><mo>→</mo><msubsup><mover><mi>χ</mi><mo>˜</mo></mover><mrow><mn>1</mn><mo>,</mo><mn>2</mn></mrow><mn>0</mn></msubsup><mo>+</mo><msup><mi>e</mi><mo>−</mo></msup></math> and <math><mrow><mover><mrow><mi>ν</mi></mrow><mrow><mo>˜</mo></mrow></mover><mo>→</mo><msubsup><mrow><mover><mrow><mi>χ</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mn>1</mn></mrow><mrow><mo>+</mo></mrow></msubsup><mo>+</mo><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> are also taken into account. These scenarios are analyzed with realistic detector performance, using multivariate techniques. Effects of systematic uncertainties and electron beam polarization dependence are also discussed. The reach is found to be complementary to the one obtained at <math><mi>p</mi><mi>p</mi></math> colliders, in particular for the compressed-slepton scenario.

Canada

Georges Azuelos

United Kingdom

Monica D’Onofrio

Italy

Kechen Wang

Search for the SUSY electroweak sector at <math><mi>e</mi><mi>p</mi></math> colliders

Supersymmetric models with sub-TeV charginos and sleptons have been a candidate for the origin of the long-standing discrepancy in the muon anomalous magnetic moment ( 2). By gathering all the available LHC Run 2 results, we investigate the latest LHC constraints on models that explain the anomaly by their chargino contribution to the muon 2. It is shown that the parameter regions where sleptons are lighter than charginos are strongly disfavored. In contrast, we find that the models with $$ {m}_{{\tilde{\mu}}_{\mathrm{L}}}\underset{\sim }{>}{m}_{{\tilde{\chi}}_1^{\pm }} $$ are still widely allowed, where the lighter chargino dominantly decays into a -boson and a neutralino.

Israel

Muon

The type I seesaw represents one of the most popular extensions of the Standard Model. Previous studies of this model have mostly focused on its ability to explain neutrino oscillations as well as on the generation of the baryon asymmetry via leptogenesis. Recently, it has been pointed out that the type I seesaw can also account for the origin of the electroweak scale due to heavy-neutrino threshold corrections to the Higgs potential. In this paper, we show for the first time that all of these features of the type I seesaw are compatible with each other. Integrating out a set of heavy Majorana neutrinos results in small masses for the Standard Model neutrinos; baryogenesis is accomplished by resonant leptogenesis; and the Higgs mass is entirely induced by heavy-neutrino one-loop diagrams, provided that the tree-level Higgs potential satisfies scale-invariant boundary conditions in the ultraviolet. The viable parameter space is characterized by a heavy-neutrino mass scale roughly in the range <math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>6.5</mn><mo>⋯</mo><mn>7.0</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> and a mass splitting among the nearly degenerate heavy-neutrino states up to a few TeV. Our findings have interesting implications for high-energy flavor models and low-energy neutrino observables. We conclude that the type I seesaw sector might be the root cause behind the masses and cosmological abundances of all known particles. This statement might even extend to dark matter in the presence of a keV-scale sterile neutrino.

Germany

Vedran Brdar

Alexander J. Helmboldt

Kai Schmitz

Type I seesaw mechanism as the common origin of neutrino mass, baryon asymmetry, and the electroweak scale

We study supersymmetric (SUSY) models in which the muon g −2 discrepancy and the dark matter relic abundance are simultaneously explained. The muon g − 2 discrepancy, or a 3 σ deviation between the experimental and theoretical results of the muon anomalous magnetic moment, can be resolved by SUSY models, which implies at least three SUSY multiplets have masses of O 100 $$ \mathcal{O}(100) $$ GeV. In particular, models with the bino, higgsino and slepton having O 100 $$ \mathcal{O}(100) $$ GeV masses are not only capable to explain the muon g −2discrepancybutnaturallycontainstheneutralinodarkmatterwiththeobservedrelic abundance. We study constraints and future prospects of such models; in particular, we find that the LHC search for events with two hadronic taus and missing transverse mo-mentum can probe this scenario through chargino/neutralino production. It is shown that almost all the parameter space of the scenario can be probed at the high-luminosity LHC, and a large part can also be tested at the XENON1T experiment as well as at the ILC.

Keisuke Yanagi

Probing minimal SUSY scenarios in the light of muon g −2 and dark matter