We explore the potential of the Large Hadron Collider (LHC) in detecting a signal originating from the production of a heavy SU(2) R  charged gauge boson that then decays into a top-bottom quark pair via the mediation of a right-handed neutrino, pp → W  R  → N  R  ℓ → (ℓ  ′  tb)ℓ. Such a channel, that we study in the context of the minimal Left-Right Symmetric Model, contrasts with conventional smoking-gun signatures targeted experimentally and phenomenologically in which only light quarks are involved. We propose a selection strategy aimed at extracting such a top-bottom signal and we estimate the resulting sensitivity of the LHC to the model. Our results demonstrate the potential impact of such a search and we therefore urge the experimental collaborations to carry out a similar analysis in the light of present and future data.

Canada

Mariana Frank

France

Benjamin Fuks

South Korea

Adil Jueid

United Kingdom

Sweden

Stefano Moretti

Özer Özdal

A novel search strategy for right-handed charged gauge bosons at the Large Hadron Collider

For the purpose of cross-fertilising currently separate experimental approaches, we connect results of LHC analyses attempting to access the properties of additional W′ and Z′ bosons from Drell-Yan processes. Under theoretical assumptions linking the two new gauge bosons, we take into account that such possible states of nature are wide enough (in relation to the leptonic mass resolution) for the corresponding signals be significantly affected by interference effects with the background from the Standard Model. The shape of the differential cross section may then no longer be a standard Breit-Wigner distribution, and asymmetry observables would become useful for characterisation (and, possibly, discovery) purposes. Under such conditions we concentrate our analysis on specific widely-studied models: the Sequential Standard Model, a model with an additional SU(2) L  gauge symmetry, as well as standard and alternative realisations of the Left-Right Symmetric Model. We show how information gathered in Z′ boson searches in terms of cross section and/or asymmetry distributions can be used to improve W′ boson searches in terms of the LHC sensitivity, and vice versa.

Jack Araz

Cross-fertilising extra gauge boson searches at the LHC

We attribute deviations of the muon and electron magnetic moments from the theoretical predictions to the presence of an additional U(1)′ supersymmetric model. We interpret the discrepancies between the muon and electron anomalous magnetic moments to be due to the presence of non-universal U(1)′ charges. In a minimally extended model, we show that requiring both deviations to be satisfied imposes constraints on the spectrum of the model, in particular on dark matter candidates and slepton masses and ordering. Choosing three benchmarks with distinct dark matter features, we study implications of the model at colliders, concentrating on variables that can distinguish our non-universal scenario from other U(1)′ implementations.

Türkiye

Yaşar Hiçyılmaz

India

Subhadeep Mondal

Cem Ün

Electron and muon magnetic moments and implications for dark matter and model characterisation in non-universal U(1)′ supersymmetric models

We perform a comprehensive analysis of the secluded supersymmetric <math><mrow><msup><mrow><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></mrow><mrow><mo>′</mo></mrow></msup></mrow></math> model, consistent with present experimental constraints. We find that, in this model, the additional <math><mrow><msup><mrow><mi>Z</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math> gauge boson can be leptophobic without resorting to gauge kinetic mixing and consequently, also <math><mi>d</mi></math>-quark-phobic, thus lowering the LHC bounds on its mass. The model can accommodate very light singlinos as DM candidates, consistent with present day cosmological and collider constraints. Light charginos and neutralinos are responsible for muon anomalous magnetic predictions within <math><mrow><mn>1</mn><mi>σ</mi></mrow></math> of the measured experimental value. Finally, we look at the possibility that a lighter <math><msup><mi>Z</mi><mo>′</mo></msup></math>, expected to decay mainly into chargino pairs and followed by the decay into lepton pairs, could be observed at 27 TeV.

Leptophobic <math><msup><mi>Z</mi><mo>′</mo></msup></math> bosons in the secluded UMSSM

We test realisations of a generic U(1) extended Minimal Supersymmetric Standard Model (UMSSM), parametrised in terms of the mixing angle pertaining to the new U(1) sector, $$ {\theta}_{E_6} $$ , against all currently available data, from space to ground experiments, from low to high energies. We find that experimental constraints are very restrictive and indicate that large gauge kinetic mixing and $$ {\theta}_{E_6} $$ /3 are required within this theoretical construct to achieve compliance with current data. The consequences are twofold. On the one hand, large gauge kinetic mixing implies that the boson emerging from the breaking of the additional U(1) symmetry is rather wide since it decays mainly into pairs. On the other hand, the preferred $$ {\theta}_{E_6} $$ value calls for a rather specific breaking pattern different from those commonly studied. We finally delineate potential signatures of the emerging UMSSM scenario in both Large Hadron Collider (LHC) and in Dark Matter (DM) experiments.

We perform a consistent analysis of the alternative left-right symmetric model emerging from grand unification. We include a large set of theoretical and experimental constraints, with a particular emphasis on dark matter observables and collider signals. We show that the exotic neutrino inherent to this class of models, the scotino, is a viable candidate for dark matter satisfying relic density and direct detection constraints. This has strong implications on the scotino mass restricting it to lie in a narrow window, as well as on the spectrum of Higgs bosons, rendering it predictable, with a few light scalar, pseudoscalar and charged states. Moreover, we also show that the extra charged gauge boson can be light, and investigate the most promising signals at the future high-luminosity upgrade of the LHC. Our findings show that the most optimistic cosmologically-favoured scenarios should be observable at 5 , whilst others could leave visible hints provided the background is under good control at the systematical level.

Natural dark matter and light bosons with an alternative left-right symmetry

We study the mass bounds of the <math><msub><mi>W</mi><mi>R</mi></msub></math> gauge boson in generic left-right symmetric models. Assuming that the gauge bosons couple universally to quarks and leptons, we allow different gauge couplings <math><msub><mi>g</mi><mi>R</mi></msub><mo>≠</mo><msub><mi>g</mi><mi>L</mi></msub></math> and mass mixing <math><mrow><msubsup><mrow><mi>V</mi></mrow><mrow><mi>CKM</mi></mrow><mrow><mi>L</mi></mrow></msubsup><mo>≠</mo><msubsup><mrow><mi>V</mi></mrow><mrow><mi>CKM</mi></mrow><mrow><mi>R</mi></mrow></msubsup></mrow></math> in the left and right sectors. Imposing constraints from collider experiments and <math><msup><mi>K</mi><mn>0</mn></msup></math>, <math><msub><mi>B</mi><mi>d</mi></msub></math>, <math><msub><mi>B</mi><mi>s</mi></msub></math> physics, we investigate scenarios where <math><msub><mi>W</mi><mi>R</mi></msub></math> is lighter or heavier than the right-handed neutrino <math><msub><mi>ν</mi><mi>R</mi></msub></math>. In these scenarios, <math><msub><mi>W</mi><mi>R</mi></msub></math> mass bounds can be considerably relaxed, while <math><msub><mi>Z</mi><mi>R</mi></msub></math> mass bounds are much more stringent. In the case where <math><msub><mi>M</mi><msub><mi>W</mi><mi>R</mi></msub></msub><mo>≤</mo><msub><mi>M</mi><msub><mi>ν</mi><mi>R</mi></msub></msub></math>, the experimental constraints come from the <math><msub><mi>W</mi><mi>R</mi></msub><mo>→</mo><mi>t</mi><mi>b</mi></math> and <math><msub><mi>W</mi><mi>R</mi></msub><mo>→</mo><mi>j</mi><mi>j</mi></math> channels, while if <math><msub><mi>M</mi><msub><mi>W</mi><mi>R</mi></msub></msub><mo>≥</mo><msub><mi>M</mi><msub><mi>ν</mi><mi>R</mi></msub></msub></math>, the dominant constraints come from <math><msub><mi>W</mi><mi>R</mi></msub><mo>→</mo><mo>ℓ</mo><mo>ℓ</mo><mi>j</mi><mi>j</mi></math>. The observed (expected) limits in the two-dimensional (<math><msub><mi>M</mi><msub><mi>W</mi><mi>R</mi></msub></msub></math>, <math><msub><mi>M</mi><msub><mi>ν</mi><mi>R</mi></msub></msub></math>) mass plane excluded at the 95% confidence level extend to approximately <math><msub><mi>M</mi><msub><mi>W</mi><mi>R</mi></msub></msub><mo>=</mo><mn>3.1</mn></math> (3.3) TeV in the <math><mi>e</mi><mi>e</mi></math> channel and 3.3 (3.4) TeV in the (<math><mi>μ</mi><mi>μ</mi></math>) channel, for a large range of right-handed neutrino masses up to <math><mrow><msub><mrow><mi>M</mi></mrow><mrow><msub><mrow><mi>ν</mi></mrow><mrow><mi>R</mi></mrow></msub></mrow></msub><mo>=</mo><mn>2.1</mn><mo>(</mo><mn>2.1</mn><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math> in the <math><mi>e</mi><mi>e</mi></math> channel and 2.6 (2.5) TeV in the (<math><mi>μ</mi><mi>μ</mi></math>) channel, representing a significant relaxation of the mass bounds.

Poulose Poulose

Relaxing LHC constraints on the <math><msub><mi>W</mi><mi>R</mi></msub></math> mass

We explore the low-scale implications of the Pati-Salam Model including the TeV scale right-handed neutrinos interacting and mixing with the MSSM fields through the inverse seesaw (IS) mechanism in light of the muon anomalous magnetic moment (muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math>) resolution and highlight the solutions which are compatible with the quasi-Yukawa unification condition (QYU). We find that the presence of the right-handed neutrinos causes heavy smuons as <math><mrow><msub><mrow><mi>m</mi></mrow><mrow><mover><mrow><mi>μ</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow></msub><mo>≳</mo><mn>800</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> in order to avoid tachyonic staus at the low scale. On the other hand, the sneutrinos can be as light as about 100 GeV, and along with the light charginos of mass <math><mrow><mo>≲</mo><mn>400</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>, they can yield such large contributions to muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math> that the discrepancy between the experiment and the theory can be resolved. These solutions also require <math><mrow><msub><mrow><mi>m</mi></mrow><mrow><msubsup><mrow><mover><mrow><mi>χ</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mn>1</mn></mrow><mrow><mo>±</mo></mrow></msubsup></mrow></msub><mo>≲</mo><mn>400</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> and <math><msub><mi>m</mi><msubsup><mover><mi>χ</mi><mo>˜</mo></mover><mn>1</mn><mn>0</mn></msubsup></msub><mo>≲</mo><mn>200</mn></math>. We also discuss such light chargino and neutralino along with the light stau (<math><mrow><msub><mrow><mi>m</mi></mrow><mrow><mover><mrow><mi>τ</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow></msub><mo>≳</mo><mn>200</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>) in the light of current LHC results. Besides, the gluino mass lies in a range <math><mrow><mo>∼</mo><mo>[</mo><mn>2.5</mn><mi>–</mi><mn>3.5</mn><mo>]</mo><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math>, which is tested in near future experiments. In addition, the model predicts relatively light Higgsinos (<math><mi>μ</mi><mo>≲</mo><mn>700</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>); hence, the second chargino mass is also light enough (<math><mrow><mo>≲</mo><mn>700</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>) to contribute to muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math>. Light Higgsinos also yield less fine-tuning at the electroweak scale, and the regions compatible with muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math> restrict <math><mrow><msub><mrow><mi>Δ</mi></mrow><mrow><mi>EW</mi></mrow></msub><mo>≲</mo><mn>100</mn></mrow></math> strictly, and this region also satisfies the QYU condition. In addition, the ratios among the Yukawa couplings should be <math><mrow><mn>1.8</mn><mo>≲</mo><msub><mrow><mi>y</mi></mrow><mrow><mi>t</mi></mrow></msub><mo>/</mo><msub><mrow><mi>y</mi></mrow><mrow><mi>b</mi></mrow></msub><mo>≲</mo><mn>2.6</mn></mrow></math>, <math><mrow><msub><mrow><mi>y</mi></mrow><mrow><mi>τ</mi></mrow></msub><mo>/</mo><msub><mrow><mi>y</mi></mrow><mrow><mi>b</mi></mrow></msub><mo>∼</mo><mn>1.3</mn></mrow></math> to yield correct fermion masses. Even though the right-handed neutrino Yukawa coupling can be varied freely, the solutions bound its range to <math><mrow><mn>0.8</mn><mo>≲</mo><msub><mrow><mi>y</mi></mrow><mrow><mi>ν</mi></mrow></msub><mo>/</mo><msub><mrow><mi>y</mi></mrow><mrow><mi>b</mi></mrow></msub><mo>≲</mo><mn>1.7</mn></mrow></math>.

Zafer Altın

Cem Salih Ün

Muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math> in an alternative quasi-Yukawa unification with a less fine-tuned seesaw mechanism

We study the low scale predictions of the supersymmetric standard model extended by <math><mrow><mi>U</mi><mo>(</mo><mn>1</mn><msub><mrow><mo>)</mo></mrow><mrow><mi>B</mi><mo>−</mo><mi>L</mi></mrow></msub><mo>×</mo><mi>U</mi><mo>(</mo><mn>1</mn><msub><mrow><mo>)</mo></mrow><mrow><mi>R</mi></mrow></msub></mrow></math> symmetry, obtained from <math><mrow><mi>S</mi><mi>O</mi><mo>(</mo><mn>10</mn><mo>)</mo></mrow></math> breaking via a left-right supersymmetric model, imposing universal boundary conditions. Two singlet Higgs fields are responsible for the radiative <math><mrow><mi>U</mi><mo>(</mo><mn>1</mn><msub><mrow><mo>)</mo></mrow><mrow><mi>B</mi><mo>−</mo><mi>L</mi></mrow></msub><mo>×</mo><mi>U</mi><mo>(</mo><mn>1</mn><msub><mrow><mo>)</mo></mrow><mrow><mi>R</mi></mrow></msub></mrow></math> symmetry breaking, and a singlet fermion <math><mi>S</mi></math> is introduced to generate neutrino masses through an inverse seesaw mechanism. The lightest neutralino or sneutrino emerge as dark matter candidates, with different low scale implications. We find that the composition of the neutralino lightest supersymmetric particle (LSP) changes considerably depending on the neutralino LSP mass, from roughly half <math><mi>U</mi><mo>(</mo><mn>1</mn><msub><mo>)</mo><mi>R</mi></msub></math> bino, half minimal supersymmetric model (MSSM) bino, to a singlet higgsino, or completely dominated by the MSSM higgsino. The sneutrino LSP is statistically much less likely, and when it occurs it is a 50-50 mixture of right-handed sneutrino and the scalar <math><mover><mi>S</mi><mo>˜</mo></mover></math>. Most of the solutions consistent with the relic density constraint survive the XENON 1T exclusion curve for both LSP cases. We compare the two scenarios and investigate parameter space points and find consistency with the muon anomalous magnetic moment only at the edge of a <math><mn>2</mn><mi>σ</mi></math> deviation from the measured value. However, we find that the sneutrino LSP solutions could be ruled out completely by the strict reinforcement of the recent <math><msup><mi>Z</mi><mo>′</mo></msup></math> mass bounds. We finally discuss collider prospects for testing the model.

Exploring the supersymmetric <math><mrow><msub><mrow><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></mrow><mrow><mi>B</mi><mo>−</mo><mi>L</mi></mrow></msub><mo>×</mo><mrow><msub><mrow><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></mrow><mrow><mi>R</mi></mrow></msub></mrow></mrow></math> model with dark matter, muon <math><mrow><mi>g</mi><mi>−</mi><mn>2</mn></mrow></math>, and <math><mrow><msup><mrow><mi>Z</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math> mass limits