On the Corner Elements of the CKM and PMNS Matrices

Michael J. Baker, J. Bordes, H. M. Chan, S. T. Tsou

Recent experiments show that the top-right corner element ($U_{e3}$) of the PMNS, like that ($V_{ub}$) of the CKM, matrix is small but nonzero, and suggest further via unitarity that it is smaller than the bottom-left corner element ($U_{τ1}$), again as in the CKM case ($V_{ub} < V_{td}$). An attempt in explaining these facts would seem an excellent test for any model of the mixing phenomenon. Here, it is shown that if to the assumption of a universal rank-one mass matrix, long favoured by phenomenologists, one adds that this matrix rotates with scale, then it follows that (A) by inputting the mass ratios $m_c/m_t, m_s/m_b, m_μ/m_τ$, and $m_2/m_3$, (i) the corner elements are small but nonzero, (ii) $V_{ub} < V_{td}$, $U_{e 3} < U_{τ1}$, (iii) estimates result for the ratios $V_{ub}/V_{td}$ and $U_{e 3}/U_{τ1}$, and (B) by inputting further the experimental values of $V_{us}, V_{tb}$ and $U_{e2},U_{μ3}$, (iv) estimates result for the values of the corner elements themselves. All the inequalities and estimates obtained are consistent with present data to within expectation for the approximations made.

Mass Hierarchy, Mixing, CP-Violation and Higgs Decay---or Why Rotation is Good for Us

Michael J Baker, J. Bordes, H. M. Chan, S. T. Tsou

The idea of a rank-one rotating mass matrix (R2M2) is reviewed detailing how it leads to ready explanations both for the fermion mass hierarchy and for the distinctive mixing patterns between up and down fermion states, which can be and have been tested against experiment and shown to be fully consistent with existing data. Further, R2M2 is seen to offer, as by-products: (i) a new solution of the strong CP problem in QCD by linking the theta-angle there to the Kobayashi-Maskawa CP-violating phase in the CKM matrix, and (ii) some novel predictions of possible anomalies in Higgs decay observable in principle at the LHC. A special effort is made to answer some questions raised.

Black Hole Evaporation Beyond the Standard Model of Particle Physics

Michael J. Baker, Andrea Thamm

The observation of an evaporating black hole would provide definitive information on the elementary particles present in nature. In particular, it could discover or exclude particles beyond those present in the standard model of particle physics. We consider a wide range of motivated scenarios beyond the standard model and identify those which would be best probed in the event of an observation. For those models we define representative benchmark parameters and characterise the photon spectra as a function of time. For the supersymmetric benchmark model, where most of the new particles produce secondary photons, we provide secondary spectra and discuss the subtle interplay between faster black hole evaporation and an increased flux of secondary photons. Finally, we discuss the impact of these models on future experimental analysis strategies.

Has the Origin of the Third-Family Fermion Masses been Determined?

Michael J. Baker, Peter Cox, Raymond R. Volkas

Precision measurements of the Higgs couplings are, for the first time, directly probing the mechanism of fermion mass generation. The purpose of this work is to determine to what extent these measurements can distinguish between the tree-level mechanism of the Standard Model and the theoretically motivated alternative of radiative mass generation. Focusing on the third-family, we classify the minimal one-loop models and find that they fall into two general classes. By exploring several benchmark models in detail, we demonstrate that a radiative origin for the tau-lepton and bottom-quark masses is consistent with current observations. While future colliders will not be able to rule out a radiative origin, they can probe interesting regions of parameter space.

Light Resonances and the Low-$q^2$ Bin of $R_{K^*}$

Wolfgang Altmannshofer, Michael J. Baker, Stefania Gori, Roni Harnik, Maxim Pospelov, Emmanuel Stamou, Andrea Thamm

LHCb has reported hints of lepton-flavor universality violation in the rare decays $B \to K^{(*)} \ell^+\ell^-$, both in high- and low-$q^2$ bins. Although the high-$q^2$ hint may be explained by new short-ranged interactions, the low-$q^2$ one cannot. We thus explore the possibility that the latter is explained by a new light resonance. We find that LHCb's central value of $R_{K^*}$ in the low-$q^2$ bin is achievable in a restricted parameter space of new-physics scenarios in which the new, light resonance decays preferentially to electrons and has a mass within approximately $10$ MeV of the di-muon threshold. Interestingly, such an explanation can have a kinematic origin and does not require a source of lepton-flavor universality violation. A model-independent prediction is a narrow peak in the differential $B \to K^* e^+e^-$ rate close to the di-muon threshold. If such a peak is observed, other observables, such as the differential $B \to K e^+e^-$ rate and $R_K$, may be employed to distinguish between models. However, if a low-mass resonance is not observed and the low-$q^2$ anomaly increases in significance, then the case for an experimental origin of the lepton-flavor universality violating anomalies would be strengthened. To further explore this, we also point out that, in analogy to $J/ψ$ decays, $e^+e^-$ and $μ^+μ^-$ decays of $φ$ mesons can be used as a cross check of lepton-flavor universality by LHCb with $5$ fb$^{-1}$ of integrated luminosity.

Probing Dark Sectors with Exploding Black Holes: Gamma Rays

Michael J. Baker, Joaquim Iguaz Juan, Aidan Symons, Andrea Thamm

The Hawking radiation from the explosion of a black hole would provide definitive information on the particle spectrum of nature. Here we quantify the potential of current and future gamma ray telescopes to probe new dark sectors. We improve on the analysis used in previous work by making careful use of the experimental response functions, deriving a more realistic estimate of the backgrounds and optimizing the statistical analysis. We compute the sensitivity of the current experiments (HAWC and LHAASO) and estimate the reach of the future experiments (SWGO and CTA North and South), for various sky positions of the explosion. We find that for a black hole exploding at $0.01\,\text{pc}$ the gamma ray signal observed by HAWC could probe dark sectors with 10-20 (or more) new Dirac fermions up to masses around $10^5\,\text{GeV}$, while CTA will be able to probe 2-15 new Dirac fermions with masses up to $10^6\,\text{GeV}$. CTA North and South will have sensitivity to 10 dark fermions up to a distance of 0.1 pc and 50 up to a distance of 0.6 pc.

Could We Observe an Exploding Black Hole in the Near Future?

Michael J. Baker, Joaquim Iguaz Juan, Aidan Symons, Andrea Thamm

Observation of an exploding black hole would provide the first direct evidence of primordial black holes, the first direct evidence of Hawking radiation, and definitive information on the particles present in nature. However, indirect constraints suggest that direct observation of an exploding Schwarzschild black hole is implausible. We introduce a dark-QED toy model consisting of a dark photon and a heavy dark electron. In this scenario a population of light primordial black holes charged under the dark $u(1)$ symmetry can become quasi-extremal, so they survive much longer than if they were uncharged, before discharging and exhibiting a Schwarzschild-like final explosion. We show that the answer is "yes", in this scenario the probability of observing an exploding black hole over the next $10$ years could potentially be over $90\%$.

The Rotating Mass Matrix, the Strong CP Problem and Higgs Decay

Michael J Baker, S. T. Tsou

We investigate a recent solution to the strong CP problem, obtaining a theta-angle of order unity, and show that a smooth trajectory of the massive eigenvector of a rank-one rotating mass matrix is consistent with the experimental data for both fermion masses and mixing angles (except for the masses of the lightest quarks). Using this trajectory we study Higgs decay and find suppression of $Γ(H\to c\bar{c})$ compared to the standard model predictions for a range of Higgs masses. We also give limits for flavour violating decays, including a relatively large branching ratio for the $τ^-μ^+$ mode.

Dynamic Freeze-In: Impact of Thermal Masses and Cosmological Phase Transitions on Dark Matter Production

Michael J. Baker, Moritz Breitbach, Joachim Kopp, Lukas Mittnacht

The cosmological abundance of dark matter can be significantly influenced by the temperature dependence of particle masses and vacuum expectation values. We illustrate this point in three simple freeze-in models. The first one, which we call kinematically induced freeze-in, is based on the observation that the effective mass of a scalar temporarily becomes very small as the scalar potential undergoes a second order phase transition. This opens dark matter production channels that are otherwise forbidden. The second model we consider, dubbed vev-induced freeze-in, is a fermionic Higgs portal scenario. Its scalar sector is augmented compared to the Standard Model by an additional scalar singlet, $S$, which couples to dark matter and temporarily acquires a vacuum expectation value (a two-step phase transition or `vev flip-flop'). While $\langle S \rangle \neq 0$, the modified coupling structure in the scalar sector implies that dark matter production is significantly enhanced compared to the $\langle S \rangle = 0$ phases realised at very early times and again today. The third model, which we call mixing-induced freeze-in, is similar in spirit, but here it is the mixing of dark sector fermions, induced by non-zero $\langle S \rangle$, that temporarily boosts the dark matter production rate. For all three scenarios, we carefully dissect the evolution of the dark sector in the early Universe. We compute the DM relic abundance as a function of the model parameters, emphasising the importance of thermal corrections and the proper treatment of phase transitions in the calculation.

The Vev Flip-Flop: Dark Matter Decay between Weak Scale Phase Transitions

Michael J. Baker, Joachim Kopp

We propose a new alternative to the Weakly Interacting Massive Particle (WIMP) paradigm for dark matter. Rather than being determined by thermal freeze-out, the dark matter abundance in this scenario is set by dark matter decay, which is allowed for a limited amount of time just before the electroweak phase transition. More specifically, we consider fermionic singlet dark matter particles coupled weakly to a scalar mediator $S_3$ and to auxiliary dark sector fields, charged under the Standard Model gauge groups. Dark matter freezes out while still relativistic, so its abundance is initially very large. As the Universe cools down, the scalar mediator develops a vacuum expectation value (vev), which breaks the symmetry that stabilises dark matter. This allows dark matter to mix with charged fermions and decay. During this epoch, the dark matter abundance is reduced to give the value observed today. Later, the SM Higgs field also develops a vev, which feeds back into the $S_3$ potential and restores the dark sector symmetry. In a concrete model we show that this "vev flip-flop" scenario is phenomenologically successful in the most interesting regions of its parameter space. We also comment on detection prospects at the LHC and elsewhere.

Finite Energy Sum Rules with Legendre Polynomial Kernels

J. Bordes, J. A. Peñarrocha, Michael J. Baker

In this note we report about a method to deal with finite energy sum rules. With a reasonable knowledge of the main resonances of the spectrum, the method guarantees that we can find a nice duality matching between the low energy hadronic data and asymptotic QCD at high energies.

Hot Leptogenesis

Michael J. Baker, Ansh Bhatnagar, Djuna Croon, Jessica Turner

We investigate a class of leptogenesis scenarios in which the sector containing the lightest right-handed neutrino establishes kinetic equilibrium at a temperature $T_{N_1} > T_\text{SM}$, where $T_\text{SM}$ is the temperature of the Standard Model sector. We study the reheating processes which realise this "hot leptogenesis" and the conditions under which kinetic and chemical equilibrium can be maintained. We derive and solve two sets of evolution equations, depending on the presence of chemical equilibrium within the hot sector, and numerically solve these for benchmark scenarios. We compare the viable parameter space of this model with standard leptogenesis scenarios with a thermal initial condition and find that hot leptogenesis resolves the neutrino and Higgs mass fine-tuning problems present in the standard scenario.

A Simplified Model of Heavy Vector Singlets for the LHC and Future Colliders

Michael J. Baker, Timothy Martonhelyi, Andrea Thamm, Riccardo Torre

We study a simplified model of two colourless heavy vector resonances in the singlet representation of $SU(2)_{L}$, with zero and unit hypercharge. We discuss mixing with the Standard Model gauge bosons due to electroweak symmetry breaking, semi-analytic formulae for production at proton colliders, requirements to obey the narrow width approximation and selected low energy constraints. We show current LHC constraints and sensitivity projections for the HL-LHC, HE-LHC, SPPC and FCC-hh on the charged and neutral heavy vectors. The utility of the simplified model Lagrangian is demonstrated by matching these results onto three explicit models: a weakly coupled abelian extension of the Standard Model gauge group, a weakly coupled non-abelian extension and a strongly coupled minimal composite Higgs model. All our results are presented in terms of physical resonance masses, using expressions which are accurate even at vector masses near the electroweak scale due to a parameter inversion we derive. We discuss the importance of this inversion and point out that its effect, and the effects of electroweak symmetry breaking, can remain important up to resonance masses of several TeV. Finally, we clarify the relation between this simplified model and the Heavy Vector Triplet (HVT) model, a simplified model for heavy $SU(2)_{L}$ triplets with zero hypercharge, and provide exact and approximate matching relations.

Detailed Calculation of Primordial Black Hole Formation During First-Order Cosmological Phase Transitions

Michael J. Baker, Moritz Breitbach, Joachim Kopp, Lukas Mittnacht

Primordial black holes could potentially form during a first-order cosmological phase transition due to a build-up of particles which are predominantly reflected from the advancing bubble walls. After discussing the general mechanism, we examine the criteria that need to be satisfied for a black hole to form. We then set out the Boltzmann equation that describes the evolution of the relevant phase space distribution function, carefully describing our treatment of the Liouville operator and the collision term. Assuming a spherical false vacuum pocket of sufficient size and a constant wall velocity, we find that black holes can form in a range of different scenarios.

Reinterpretation of LHC Results for New Physics: Status and Recommendations after Run 2

Waleed Abdallah, Shehu AbdusSalam, Azar Ahmadov, Amine Ahriche, Gaël Alguero, Benjamin C. Allanach, Jack Y. Araz, Alexandre Arbey, Chiara Arina, Peter Athron, Emanuele Bagnaschi, Yang Bai, Michael J. Baker, Csaba Balazs, Daniele Barducci, Philip Bechtle, Aoife Bharucha, Andy Buckley, Jonathan Butterworth, Haiying Cai, Claudio Campagnari, Cari Cesarotti, Marcin Chrzaszcz, Andrea Coccaro, Eric Conte, Jonathan M. Cornell, Louie Dartmoor Corpe, Matthias Danninger, Luc Darmé, Aldo Deandrea, Nishita Desai, Barry Dillon, Caterina Doglioni, Juhi Dutta, John R. Ellis, Sebastian Ellis, Farida Fassi, Matthew Feickert, Nicolas Fernandez, Sylvain Fichet, Jernej F. Kamenik, Thomas Flacke, Benjamin Fuks, Achim Geiser, Marie-Hélène Genest, Akshay Ghalsasi, Tomas Gonzalo, Mark Goodsell, Stefania Gori, Philippe Gras, Admir Greljo, Diego Guadagnoli, Sven Heinemeyer, Lukas A. Heinrich, Jan Heisig, Deog Ki Hong, Tetiana Hryn'ova, Katri Huitu, Philip Ilten, Ahmed Ismail, Adil Jueid, Felix Kahlhoefer, Jan Kalinowski, Deepak Kar, Yevgeny Kats, Charanjit K. Khosa, Valeri Khoze, Tobias Klingl, Pyungwon Ko, Kyoungchul Kong, Wojciech Kotlarski, Michael Krämer, Sabine Kraml, Suchita Kulkarni, Anders Kvellestad, Clemens Lange, Kati Lassila-Perini, Seung J. Lee, Andre Lessa, Zhen Liu, Lara Lloret Iglesias, Jeanette M. Lorenz, Danika MacDonell, Farvah Mahmoudi, Judita Mamuzic, Andrea C. Marini, Pete Markowitz, Pablo Martinez Ruiz del Arbol, David Miller, Vasiliki Mitsou, Stefano Moretti, Marco Nardecchia, Siavash Neshatpour, Dao Thi Nhung, Per Osland, Patrick H. Owen, Orlando Panella, Alexander Pankov, Myeonghun Park, Werner Porod, Darren Price, Harrison Prosper, Are Raklev, Jürgen Reuter, Humberto Reyes-González, Thomas Rizzo, Tania Robens, Juan Rojo, Janusz A. Rosiek, Oleg Ruchayskiy, Veronica Sanz, Kai Schmidt-Hoberg, Pat Scott, Sezen Sekmen, Dipan Sengupta, Elizabeth Sexton-Kennedy, Hua-Sheng Shao, Seodong Shin, Luca Silvestrini, Ritesh Singh, Sukanya Sinha, Jory Sonneveld, Yotam Soreq, Giordon H. Stark, Tim Stefaniak, Jesse Thaler, Riccardo Torre, Emilio Torrente-Lujan, Gokhan Unel, Natascia Vignaroli, Wolfgang Waltenberger, Nicholas Wardle, Graeme Watt, Georg Weiglein, Martin J. White, Sophie L. Williamson, Jonas Wittbrodt, Lei Wu, Stefan Wunsch, Tevong You, Yang Zhang, José Zurita

Leptonic WIMP Coannihilation and the Current Dark Matter Search Strategy

Michael J. Baker, Andrea Thamm

We discuss the extent to which models of Weakly Interacting Massive Particle (WIMP) Dark Matter (DM) at and above the electroweak scale can be probed conclusively in future high energy and astroparticle physics experiments. We consider simplified models with bino-like dark matter and slepton-like coannihilation partners, and find that perturbative models yield the observed relic abundance up to at least 10 TeV. We emphasise that coannihilation can either increase or decrease the dark matter relic abundance. We compute the sensitivity of direct detection experiments to DM-nucleus scattering, consider indirect detection bounds and estimate the sensitivity of future proton colliders to slepton pair production. We find that current and future experiments will be able to probe the Dirac DM models up to at least 10 TeV. However, current and future searches will not be sensitive to models of Majorana dark matter for masses above 2 or 4 TeV, for one or ten coannihilation partners respectively, leaving around 70 % of the parameter space unconstrained. This demonstrates the need for new experimental ideas to access models of coannihilating Majorana dark matter.

Radiative Muon Mass Models and $(g-2)_μ$

Michael J. Baker, Peter Cox, Raymond R. Volkas

Recent measurements of the Higgs-muon coupling are directly probing muon mass generation for the first time. We classify minimal models with a one-loop radiative mass mechanism and show that benchmark models are consistent with current experimental results. We find that these models are best probed by measurements of $(g-2)_μ$, even when taking into account the precision of Higgs measurements expected at future colliders. The current $(g-2)_μ$ anomaly, if confirmed, could therefore be a first hint that the muon mass has a radiative origin.

Report of the Topical Group on Physics Beyond the Standard Model at Energy Frontier for Snowmass 2021

Tulika Bose, Antonio Boveia, Caterina Doglioni, Simone Pagan Griso, James Hirschauer, Elliot Lipeles, Zhen Liu, Nausheen R. Shah, Lian-Tao Wang, Kaustubh Agashe, Juliette Alimena, Sebastian Baum, Mohamed Berkat, Kevin Black, Gwen Gardner, Tony Gherghetta, Josh Greaves, Maxx Haehn, Phil C. Harris, Robert Harris, Julie Hogan, Suneth Jayawardana, Abraham Kahn, Jan Kalinowski, Simon Knapen, Ian M. Lewis, Meenakshi Narain, Katherine Pachal, Matthew Reece, Laura Reina, Tania Robens, Alessandro Tricoli, Carlos E. M. Wagner, Riley Xu, Felix Yu, Filip Zarnecki, Amin Aboubrahim, Andreas Albert, Michael Albrow, Wolfgang Altmannshofer, Gerard Andonian, Artur Apresyan, Kétévi Adikle Assamagan, Patrizia Azzi, Howard Baer, Michael J. Baker, Avik Banerjee, Vernon Barger, Brian Batell, Martin Bauer, Hugues Beauchesne, Samuel Bein, Alexander Belyaev, Ankit Beniwal, Mikael Berggren, Prudhvi N. Bhattiprolu, Nikita Blinov, Alain Blondel, Oleg Brandt, Giacomo Cacciapaglia, Rodolfo Capdevilla, Marcela Carena, Cesare Cazzaniga, Francesco Giovanni Celiberto, Cari Cesarotti, Sergei V. Chekanov, Hsin-Chia Cheng, Thomas Y. Chen, Yuze Chen, R. Sekhar Chivukula, Matthew Citron, James Cline, Tim Cohen, Jack H. Collins, Eric Corrigan, Nathaniel Craig, Daniel Craik, Andreas Crivellin, David Curtin, Smita Darmora, Arindam Das, Sridhara Dasu, Annapaola de Cosa, Aldo Deandrea, Antonio Delgado, Zeynep Demiragli, David d'Enterria, Frank F. Deppisch, Radovan Dermisek, Nishita Desai, Abhay Deshpande, Jordy de Vries, Jennet Dickinson, Keith R. Dienes, Karri Folan Di Petrillo, Matthew J. Dolan, Peter Dong, Patrick Draper, Marco Drewes, Etienne Dreyer, Peizhi Du, Florian Eble, Majid Ekhterachian, Motoi Endo, Rouven Essig, Jesse N. Farr, Farida Fassi, Jonathan L. Feng, Gabriele Ferretti, Daniele Filipetto, Thomas Flacke, Karri Folan Di Petrillo, Roberto Franceschini, Diogo Buarque Franzosi, Keisuke Fujii, Benjamin Fuks, Sri Aditya Gadam, Boyu Gao, Aran Garcia-Bellido, Isabel Garcia Garcia, Maria Vittoria Garzelli, Stephen Gedney, Marie-Hélène Genest, Tathagata Ghosh, Mark Golkowski, Giovanni Grilli di Cortona, Emine Gurpinar Guler, Yalcin Guler, C. Guo, Nate Graf, Ulrich Haisch, Jan Hajer, Koichi Hamaguchi, Tao Han, Philip Harris, Sven Heinemeyer, Christopher S. Hill, Joshua Hiltbrand, Tova Ray Holmes, Samuel Homiller, Sungwoo Hong, Walter Hopkins, Shih-Chieh Hsu, Phil Ilten, Wasikul Islam, Sho Iwamoto, Daniel Jeans, Laura Jeanty, Haoyi Jia, Sergo Jindariani, Daniel Johnson, Felix Kahlhoefer, Yonatan Kahn, Paul Karchin, Thomas Katsouleas, Shin-ichi Kawada, Junichiro Kawamura, Chris Kelso, Elham E Khoda, Valery Khoze, Doojin Kim, Teppei Kitahara, Juraj Klaric, Michael Klasen, Kyoungchul Kong, Wojciech Kotlarski, Ashutosh V. Kotwal, Jonathan Kozaczuk, Richard Kriske, Suchita Kulkarni, Jason Kumar, Manuel Kunkel, Greg Landsberg, Kenneth Lane, Clemens Lange, Lawrence Lee, Jiajun Liao, Benjamin Lillard, Lingfeng Li, Shuailong Li, Shu Li, Jenny List, Tong Li, Hongkai Liu, Jia Liu, Jonathan D Long, Enrico Lunghi, Kun-Feng Lyu, Danny Marfatia, Dakotah Martinez, Stephen P. Martin, Navin McGinnis, Karrick McGinty, Krzysztof Mękała, Federico Meloni, Oleksii Mikulenko, Ming Huang, Rashmish K. Mishra, Manimala Mitra, Vasiliki A. Mitsou, Chang-Seong Moon, Alexander Moreno, Takeo Moroi, Gerard Mourou, Malte Mrowietz, Patric Muggli, Jurina Nakajima, Pran Nath, J. Nelson, Matthias Neubert, Laura Nosler, Maria Teresa Núñez Pardo de Vera, Nobuchika Okada, Satomi Okada, Vitalii A. Okorokov, Yasar Onel, Tong Ou, Maksym Ovchynnikov, Rojalin Padhan, Priscilla Pani, Luca Panizzi, Andreas Papaefstathiou, Kevin Pedro, Cristián Peña, Federica Piazza, James Pinfold, Deborah Pinna, Werner Porod, Chris Potter, Markus Tobias Prim, Stefano Profumo, James Proudfoot, Mudit Rai, Filip Rajec, Reese Ramos, Michael J. Ramsey-Musolf, Javier Resta-Lopez, Jürgen Reuter, Andreas Ringwald, Chiara Rizzi, Thomas G. Rizzo, Giancarlo Rossi, Richard Ruiz, L. Rygaard, Aakash A. Sahai, Shadman Salam, Pearl Sandick, Deepak Sathyan, Christiane Scherb, Pedro Schwaller, Leonard Schwarze, Pat Scott, Sezen Sekmen, Dibyashree Sengupta, S. Sen, Anna Sfyrla, Eric Shackelford, T. Sharma, Varun Sharma, Jessie Shelton, William Shepherd, Seodong Shin, Elizabeth H. Simmons, Zoie Sloneker, Carlos Vázquez Sierra, Torbjörn Sjöstrand, Scott Snyder, Huayang Song, Giordon Stark, Patrick Stengel, Joachim Stohr, Daniel Stolarski, Matt Strassler, Nadja Strobbe, Julia Gonski, Rebeca Gonzalez Suarez, Taikan Suehara, Shufang Su, Wei Su, Raza M. Syed, Tim M. P. Tait, Toshiki Tajima, Andy Tang, Xerxes Tata, Teodor Tchalokov, Andrea Thamm, Brooks Thomas, Natalia Toro, Nhan V. Tran, Loan Truong, Yu-Dai Tsai, Eva Tuecke, Nikhilesh Venkatasubramanian, Chris B. Verhaaren, Carl Vuosalo, Xiao-Ping Wang, Xing Wang, Yikun Wang, Zhen Wang, Christian Weber, Glen White, Martin White, Anthony G. Williams, Brady Williams, Mike Williams, Stephane Willocq, Alex Woodcock, Yongcheng Wu, Ke-Pan Xie, Keping Xie, Si Xie, C. -H. Yeh, Ryo Yonamine, David Yu, S. -S. Yu, Mohamed Zaazoua, Aleksander Filip Żarnecki, Kamil Zembaczynski, Danyi Zhang, Jinlong Zhang, Frank Zimmermann, Jose Zurita

Collider Signatures of Coannihilating Dark Matter in Light of the B-Physics Anomalies

Michael J. Baker, Darius A. Faroughy, Sokratis Trifinopoulos

Motivated by UV explanations of the $B$-physics anomalies, we study a dark sector containing a Majorana dark matter candidate and a coloured coannihilation partner, connected to the Standard Model predominantly via a $U_1$ vector leptoquark. A TeV scale $U_1$ leptoquark, which couples mostly to third generation fermions, is the only successful single-mediator description of the $B$-physics anomalies. After calculating the dark matter relic surface, we focus on the most promising experimental avenue: LHC searches for the coloured coannihilation partner. We find that the coloured partner hadronizes and forms meson-like bound states leading to resonant signatures at colliders reminiscent of the quarkonia decay modes in the Standard Model. By recasting existing dilepton and monojet searches we exclude coannihilation partner masses less than 280 GeV and 400 GeV, respectively. Since other existing collider searches do not significantly probe the parameter space, we propose a new dedicated search strategy for pair production of the coloured partner decaying into $bbττ$ final states and dark matter particles. This search is expected to probe the model up to dark matter masses around 600 GeV with current luminosity.

Filtered Baryogenesis

Michael J. Baker, Moritz Breitbach, Joachim Kopp, Lukas Mittnacht, Yotam Soreq

We propose a new mechanism to simultaneously explain the observed dark matter abundance and the baryon asymmetry of the Universe. The mechanism is based on the Filtered Dark Matter scenario, where dark matter particles acquire a large mass during a first-order phase transition. This implies that only a small fraction of them are energetic enough to enter the advancing true vacuum bubbles and survive until today, while the rest are reflected and annihilate away quickly. We supplement this scenario with a CP-violating interaction, which creates a chiral asymmetry in the population of dark matter particles. In the false vacuum phase, a portal interaction quickly converts the dark sector chiral asymmetry into a Standard Model lepton asymmetry. The lepton asymmetry is then partially converted to a baryon asymmetry by standard electroweak sphaleron processes. We discuss the dependence of the generated asymmetry on the parameters of the model for two different portal interactions and demonstrate successful baryogenesis for both. For one of the portals, it is also possible to simultaneously explain the observed dark matter abundance, over many orders of magnitude in the dark matter mass.