<p>Among the particles being searched for at the LHC beyond the Standard Model are bileptons, which are doubly charged gauge bosons. Bileptons are predicted by several Standard Model extensions, including the so-called 331 models with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>β</mi><mo>=</mo><msqrt><mn>3</mn></msqrt></math>. The minimal formulation of these models is generally plagued by a low-energy Landau pole, which can undermine current predictions for TeV-scale bileptons. We analyze this issue and investigate the possibility to shift the Landau pole at higher energy scales by extending the troublesome minimal 331 models.</p>

Italy

Stefano Morisi

Giulia Ricciardi

Giovanna Paola Perdonà

Rescuing 331 bileptons from the Landau pole

<p>We propose an alternative to the axion mechanism for addressing the charge parity (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math>) problem in QCD. Our approach involves imposing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> as an inherent symmetry of the Lagrangian, which is then spontaneously broken. To generate the correct texture for the Yukawa matrices, we introduce a discrete <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="double-struck">Z</mi><mn>2</mn></msub></math> symmetry that is softly broken by the scalar potential. By identifying a benchmark point for the Yukawa couplings that aligns with the measured quark masses, the Cabibbo-Kobayashi-Maskawa matrix, and low-energy flavor-changing constraints, our findings suggest that this model offers a viable solution to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> problem.</p>

Germany

Rodolfo Ferro-Hernández

Mexico

Eduardo Peinado

Axionless strong <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math> problem solution: The spontaneous <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math>-violation case

We investigate the effects on sub-TeV resonant leptogenesis of primordial black holes with masses from <math><msup><mn>10</mn><mn>6</mn></msup><mtext> </mtext><mtext> </mtext><mi>g</mi></math> to <math><mo>∼</mo><msup><mn>10</mn><mn>9</mn></msup><mtext> </mtext><mtext> </mtext><mi>g</mi></math>. The latter might dominate the energy content of the Universe altering its evolution and, eventually, diluting the final baryon asymmetry. We find that, depending on the mass and abundance of primordial black holes, the parameter space of sub-TeV resonant leptogenesis shrinks towards higher right-handed neutrino masses and smaller active-sterile mixing. Remarkably, this translates into important implications for the experimental searches of heavy neutral leptons. Conversely, we demonstrate that a possible future detection of sub-TeV heavy neutral leptons would disfavor regions of the parameter space of primordial black holes currently allowed.

Roberta Calabrese

Marco Chianese

Jacob Gunn

Gennaro Miele

Ninetta Saviano

Impact of primordial black holes on heavy neutral leptons searches in the framework of resonant leptogenesis

Despite being remarkably predictive, the Standard Model leaves unanswered several important issues, which motivate an ongoing search for its extensions. One fashionable possibility are the so-called 331 models, where the electroweak gauge group is extended to <math><msub><mi>SU</mi><mi>L</mi></msub><mo>(</mo><mn>3</mn><mo>)</mo><mo>×</mo><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></math>. We focus on a minimal extension which includes vectorlike quarks (VLQs) and new gauge bosons, performing a consistent analysis of the production at the LHC of a pair of doubly charged bileptons. We include for the first time all the relevant processes where VLQs contribute and, in particular, the associate production VLQ bilepton. Finally, we extract the bound on the bilepton mass, <math><msub><mi>m</mi><mi>Y</mi></msub><mo>&gt;</mo><mn>1300</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, from a reinterpretation of a recent ATLAS search for doubly charged Higgs bosons in multilepton final states.

Alberto Orso Maria Iorio

Natascia Vignaroli

331 models and bilepton searches at the LHC

We investigate the role that the evaporation of light primordial black holes may have played in the production of the baryon asymmetry of the Universe through high-scale leptogenesis. In particular, for masses of primordial black holes in the range <math><mrow><mo>[</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>6</mn></mrow></msup><mi>–</mi><msup><mrow><mn>10</mn></mrow><mrow><mn>9</mn></mrow></msup><mo>]</mo><mtext> </mtext><mtext> </mtext><mi>g</mi></mrow></math>, we find a dilution of thermally generated lepton asymmetry via entropy injection in the primordial plasma after the sphaleron freeze-out. As a consequence, we can put strong constraints on the primordial black hole parameters, showing the mutual exclusion limits between primordial black holes and high-scale leptogenesis. Remarkably, we point out an interplay between the upper bound on the initial abundance of primordial black holes and the active neutrino mass scale.

Limits on light primordial black holes from high-scale leptogenesis

Primordial black holes (PBHs) hypothetically generated in the first instants of life of the Universe are potential dark matter (DM) candidates. Focusing on PBHs masses in the range <math><mo>[</mo><mn>5</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>14</mn></mrow></msup><mo>−</mo><mn>5</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>15</mn></mrow></msup><mo>]</mo></math> g, we point out that the neutrinos emitted by PBHs evaporation can interact through the coherent elastic neutrino nucleus scattering (CEνNS) producing an observable signal in multi-ton DM direct detection experiments. We show that with the high exposures envisaged for the next-generation facilities, it will be possible to set bounds on the fraction of DM composed by PBHs improving the existing neutrino limits obtained with Super-Kamiokande. We also quantify to what extent a signal originating from a small fraction of DM in the form of PBHs would modify the so-called “neutrino floor”, the well-known barrier towards detection of weakly interacting massive particles (WIMPs) as the dominant DM component.

Damiano F.G. Fiorillo

Antonio Palazzo

Primordial black hole dark matter evaporating on the neutrino floor

Neutrino-nucleus coherent scattering measurements by the COHERENT collaboration provide us with a unique capability to test various beyond the standard model scenarios. In this work, we constrain scalar leptoquarks (LQs) using the COHERENT data. LQs arise in many extensions of the Standard Model (SM). Generally, the mass of the LQs is assumed to be very high to avoid the bounds from proton decay. However, there are low-scale LQ models which prohibit proton decay by construction. We consider two electroweak doublet scalar LQ models with hypercharge <math><mrow><mi>Y</mi><mo>=</mo><mn>1</mn><mo>/</mo><mn>6</mn></mrow></math>, and <math><mrow><mi>Y</mi><mo>=</mo><mn>7</mn><mo>/</mo><mn>6</mn></mrow></math> and provide the bounds in the plane of the Yukawa coupling and the mass of LQ. We also compare the bounds on LQs coming from various other experiments and find that the COHERENT one covers a wide range of LQ masses from MeV to TeV and in certain regions the constraints are competitive with the others.

Samiran Roy

Pietro Santorelli

Constraining scalar leptoquarks using COHERENT data

The Standard Model of particle physics and its description of nature have been recently challenged by a series of precision measurements performed via different accelerator machines. Statistically significant anomalies emerged when measuring the muon magnetic momentum, and very recently when deducing the mass of the <math><mi>W</mi></math> boson. Here we consider a radiative extension of the Standard Model devised to be sufficiently versatile to reconcile the various experimental results while further predicting the existence of new bosons and fermions with a mass spectrum in the TeV energy scale. The resulting spectrum is, therefore, within the energy reach of the proton-proton collisions at the LHC experiments at CERN. The model investigated here allows us to interpolate between composite and elementary extensions of the Standard Model with an emphasis on a new modified Yukawa sector that is needed to accommodate the anomalies. Focusing on the radiative regime of the model, we introduce interesting search channels of immediate impact for the ATLAS and CMS experimental programs such as the associate production of Standard Model particles with either invisible or long-lived particles. We further show how to adapt earlier supersymmetry-motivated searchers of new physics to constrain the spectrum and couplings of the new scalars and fermions. Overall, the new physics template simultaneously accounts for the bulk of the observed experimental anomalies while suggesting a wide spectrum of experimental signatures relevant for the current LHC experiments.

France

Giacomo Cacciapaglia

Antimo Cagnotta

Francesco Carnevali

Agostino De Iorio

Denmark

Francesco Sannino

Radiative flavor template at the LHC: <math><mi>g</mi><mo>−</mo><mn>2</mn></math> and the <math><mi>W</mi></math> mass

Recently Dolgov and Pozdnyakov proposed a new baryogenesis mechanism in which baryon asymmetry is produced without violating baryon number at the Lagrangian level. In this scenario, baryon asymmetry is generated by absorption of a new particle <math><mi>X</mi></math> carrying baryon number onto primordial black holes (PBHs). Assuming <math><mi>C</mi><mi>P</mi></math>-violation, the particle <math><mi>X</mi></math> is absorbed at a different rate than the antiparticle <math><mrow><mover><mrow><mi>X</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math>, producing an asymmetry in the baryonic number. We independently test this scenario, finding that it suffers from two fundamental issues. At the phenomenological level, strong absorption by PBHs initially increases the baryon asymmetry. However, at later times such asymmetry is completely absorbed by PBHs. In order to overcome this issue, we account for PBH evaporation, which provides a natural way of halting the absorption while keeping a finite baryon asymmetry. We provide a systematic study of the parameter space, identifying the regions leading to the production of the baryon asymmetry without violating the known constraints on PBHs concentration. At the theoretical level, a model realizing the <math><mi>C</mi><mi>P</mi></math>-violation postulated in this scenario is difficult to realize. We show, by implementing a minimal model, that the framework proposed in the original work in order to produce <math><mi>C</mi><mi>P</mi></math>-violation, even if qualitatively correct, is quantitatively in disagreement with the observed baryon asymmetry, namely this mechanism produces only a fraction of the total baryon asymmetry.

Antonio Ambrosone

Damiano F. G. Fiorillo

Towards baryogenesis via absorption from primordial black holes

Many extensions of the Standard Model predict the existence of new charged or neutral gauge bosons, with a wide variety of phenomenological implications depending on the model adopted. The search for such particles is extensively carried through at the Large Hadron Collider (LHC), and it is therefore of crucial importance to have for each proposed scenario quantitative predictions that can be matched to experiments. In this work we focus on the implications of one of these models, the top-flavor model (TF), proposing a charged <math><msup><mi>W</mi><mo>′</mo></msup></math> boson that has preferential couplings to the third-generation fermions. We compare such predictions to the ones from the so-called sequential Standard Model (SSM), that is used as benchmark, being one of the simplest and most commonly considered models for searches at the LHC. We identify the parameter space still open for searches at the LHC, and we show that the cross sections for the processes <math><mi>p</mi><mi>p</mi><mo>→</mo><msup><mi>W</mi><mo>′</mo></msup><mo>→</mo><mi>τ</mi><mi>ν</mi></math> and <math><mi>p</mi><mi>p</mi><mo>→</mo><msup><mi>W</mi><mo>′</mo></msup><mo>→</mo><mi>t</mi><mi>b</mi></math> in the TF assume different values with respect to the SSM as a function of the particle mass and width and that the TF has realizations that would not be allowed in the SSM and not yet excluded by data. This study makes the case for further searches at the LHC and shows how a complete and systematic model-independent analysis of <math><msup><mi>W</mi><mo>′</mo></msup></math> boson phenomenology at colliders is essential to provide guidance for future searches.