<p>We investigate the effects of nonthermally produced dark matter on large-scale structure formation, focusing on the gravitino dark matter. Our analysis shows that large-scale structure measurements from the Sloan Digital Sky Survey (SDSS) luminous red galaxy (LRG) data offer a promising approach to probing nonthermally produced gravitinos. Specifically, if gravitinos resulting from neutralino decay constitute a fraction <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>F</mi><mi>dec</mi></msub><mo>=</mo><mn>0.35</mn><mo stretchy="false">(</mo><mn>0.1</mn><mo stretchy="false">)</mo></math> of the dark matter component, the data exclude binolike neutralino with a mass <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><msubsup><mi>χ</mi><mn>1</mn><mn>0</mn></msubsup></msub><mo>≲</mo><mn>25</mn><mo stretchy="false">(</mo><mn>11</mn><mo stretchy="false">)</mo><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> at 95% C.L. Furthermore, this constraint appears to be largely independent of the gravitino mass.</p>

China

Liyuan Guo

Weiyi Deng

South Korea

Chengcheng Han

Zhanhong Lei

Probing nonthermal gravitinos through large-scale structure observations

The self-interacting dark matter (SIDM) paradigm offers a potential solution to the small-scale structure problems faced by collisionless cold dark matter. This framework incorporates self-interactions among dark matter particles, typically mediated by a particle with a MeV-scale mass. Recent evidences of nano-Hertz gravitational waves from pulsar timing arrays (PTAs) such as NANOGrav, CPTA, EPTA, and PPTA suggest the occurrence of a first-order phase transition (FOPT) at a MeV-scale temperature. Considering the close proximity between these two scales, we propose that the mediator mass in the SIDM model originates from the spontaneous breaking of a <math><mi>U</mi><mo>(</mo><mn>1</mn><msup><mo>)</mo><mo>′</mo></msup></math> symmetry, which is driven by the FOPT indicated by PTA data. Consequently, the alignment of these two scales is believed to be deeply connected by the same underlying physics. By extensively exploring the parameter space, remarkably, we find that the parameter space favored by SIDM just provides an explanation for the PTA data.

Ke-Pan Xie

Jin Min Yang

Mengchao Zhang

Self-interacting dark matter implied by nano-Hertz gravitational waves

We explore a scenario of high-scale supersymmetry where all supersymmetric particles except gauginos stay at a high-energy scale <math><msub><mi>M</mi><mi>SUSY</mi></msub></math> that is much larger than the reheating temperature <math><msub><mi>T</mi><mi>RH</mi></msub></math>. The dark matter is dominated by a bino component with mass around the electroweak scale and the observed relic abundance is mainly generated by the freeze-in process during the early Universe. Considering the various constraints, we identify two available scenarios in which the supersymmetric sector at an energy scale below <math><msub><mi>T</mi><mi>RH</mi></msub></math> consists of (a) bino or (b) bino and wino. Typically, for a bino mass around 0.1–1 TeV and a wino mass around 2 TeV, we find that <math><msub><mi>M</mi><mi>SUSY</mi></msub></math> should be around <math><msup><mn>10</mn><mrow><mn>13</mn><mo>−</mo><mn>14</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> with <math><msub><mi>T</mi><mi>RH</mi></msub></math> around <math><msup><mn>10</mn><mrow><mn>4</mn><mo>−</mo><mn>6</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>.

Peiwen Wu

Freeze-in bino dark matter in high-scale supersymmetry

CERN

Carlotta Accettura

United Kingdom

Dean Adams

United States

Rohit Agarwal

Claudia Ahdida

Italy

Chiara Aimè

Nicola Amapane

David Amorim

Paolo Andreetto

Fabio Anulli

Robert Appleby

Artur Apresyan

Aram Apyan

France

Sergey Arsenyev

Pouya Asadi

Egypt

Mohammed Mahmoud

Aleksandr Azatov

John Back

Lorenzo Balconi

Laura Bandiera

Roger Barlow

Nazar Bartosik

Emanuela Barzi

Fabian Batsch

Matteo Bauce

J. Berg

Andrea Bersani

Alessandro Bertarelli

Alessandro Bertolin

Kevin Black

Fulvio Boattini

Alex Bogacz

Maurizio Bonesini

Bernardo Bordini

Salvatore Bottaro

Luca Bottura

Alessandro Braghieri

Marco Breschi

Natalie Bruhwiler

Xavier Buffat

Laura Buonincontri

Philip Burrows

Graeme Burt

Dario Buttazzo

Barbara Caiffi

Marco Calviani

Simone Calzaferri

Daniele Calzolari

Rodolfo Capdevilla

Christian Carli

Fausto Casaburo

Massimo Casarsa

Luca Castelli

Maria Catanesi

Lorenzo Cavallucci

Gianluca Cavoto

Spain

Francesco Celiberto

Luigi Celona

Alessandro Cerri

Gianmario Cesarini

Cari Cesarotti

Portugal

Grigorios Chachamis

Antoine Chance

Switzerland

Siyu Chen

Yang-Ting Chien

Mauro Chiesa

Anna Colaleo

Francesco Collamati

Gianmaria Collazuol

Marco Costa

Nathaniel Craig

Camilla Curatolo

Canada

David Curtin

Giacomo Molin

Germany

Magnus Dam

Heiko Damerau

Sridhara Dasu

Jorge Blas

Stefania Curtis

Ernesto Matteis

Stefania Rosa

Jean-Pierre Delahaye

Dmitri Denisov

Türkiye

Haluk Denizli

Christopher Densham

Radovan Dermisek

Luca Luzio

Elisa Meco

Biagio Micco

Keith Dienes

Eleonora Diociaiuti

Tommaso Dorigo

Alexey Dudarev

Robert Edgecock

Filippo Errico

Marco Fabbrichesi

Stefania Farinon

Anna Ferrari

Jose Somoza

Netherlands

Frank Filthaut

Davide Fiorina

Erratum: Towards a muon collider

A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10 TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work.

Towards a muon collider

Type II seesaw leptogenesis simultaneously explains the origin of neutrino masses, the baryon asymmetry of our universe, and inflation. The Large Hadron Collider (LHC) provides an opportunity to directly test type II seesaw leptogenesis by looking for the predicted triplet Higgs. In this paper, we perform an analysis of the detection prospect for the triplet Higgs at the LHC through multi-electron channels. We find that due to the contribution of the   $pp\to H^{\pm \pm }H^{\mp }$   process, the sensitivity of multi-electron channels searching for doubly-charged Higgs pair production can be improved. We also investigate the   $pp\to H^{\pm \pm }H^{\mp }$   signals to probe   $pp\to H^{\pm \pm }H^{\mp }$   production and find that the future high luminosity LHC could probe a triplet Higgs around 1.2 TeV at the   $pp\to H^{\pm \pm }H^{\mp }$   level.

Weihao Liao

Testing type II seesaw leptogenesis at the LHC  

There is increasing evidence suggesting a discrepancy between the cosmic dipole observed in the number count of distant galaxies and the one derived from the cosmic microwave background (CMB). In this study, we investigate the possibility that the cosmic dipole problem can be addressed by considering the QCD axion, a hypothetical particle that arises from the spontaneous breaking of the Peccei-Quinn symmetry and is postulated to constitute the dark matter in our Universe.

QCD axion dark matter and the cosmic dipole problem

It is known that a light scalar field obtains fluctuations in the de Sitter inflationary background. Such fluctuations could provide an initial condition for baryogenesis through the Affleck-Dine mechanism, where an approximate <math><mi>U</mi><msub><mrow><mo>(</mo><mn>1</mn><mo>)</mo></mrow><mrow><mi>B</mi></mrow></msub></math> symmetry is usually assumed. However, an interpretation of the baryon number generation in this way is strongly related to the correlation length of the angular mode. In this work, we calculate the correlation length of the angular mode for a model exhibiting an approximate <math><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></math> symmetry. We find that for a massive nearly non-interacting field, the correlation length of the angular mode is determined by the mass parameter of the model and it is similar to <math><msup><mrow><mi>H</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><mi>exp</mi><mo>⁡</mo><mo>(</mo><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>/</mo><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></math>. Applying this result to baryogenesis via the Affleck-Dine mechanism with a stochastic origin, we find that only for <math><mi>m</mi><mo>≪</mo><mi>O</mi><mo>(</mo><mn>0.1</mn><mo>)</mo><mi>H</mi></math> (assuming <math><msub><mrow><mi>N</mi></mrow><mrow><mo>⁎</mo></mrow></msub><mo>=</mo><mn>60</mn></math>) can the correlation length of the baryon number density be much larger than our current horizon size, such that we live in the baryon-rich region. If this is not true, at early times our universe would consist of numerous patches of baryon-rich and anti-baryon-rich regions with the average baryon number being nearly zero.

Correlation length of the angular mode for an approximate (1) Symmetry During Inflation

Recently, it has been found that introducing a triplet Higgs to the standard model could provide a feasible leptogenesis to generate the baryon asymmetry of our Universe, providing that the inflation is driven by the mixing state of the triplet Higgs and standard model Higgs. In this work, we survey the viable parameter space satisfying the vacuum stability and perturbativity in this model. We find that the introduction of the triplet Higgs would also ameliorate the problem of the Higgs vacuum instability. We present two representative parameter regions where the origin of neutrino masses, baryon asymmetry of the Universe, and inflation can be explained while keeping consistent with the condition of vacuum stability and perturbativity.

Sihui Huang

Vacuum stability of the type II seesaw leptogenesis from inflation

The Type II Seesaw Mechanism provides a minimal framework to explain the neutrino masses involving the introduction of a single triplet Higgs to the Standard Model. However, this simple extension was believed to be unable to successfully explain the observed baryon asymmetry of the universe through Leptogenesis. In our previous work (Phys. Rev. Lett. 128 (2022) 141801), we demonstrated that the triplet Higgs of the Type II Seesaw Mechanism alone can simultaneously generate the observed baryon asymmetry of the universe and the neutrino masses while playing a role in setting up Inflation. This is achievable with a triplet Higgs mass as low as 1 TeV, and predicts that the neutral component obtains a small vacuum expectation value v ∆ &lt; 10 keV. We find that our model has very rich phenomenology and can be tested by various terrestrial experiments as well as by astronomical observations. Particularly, we show that the successful parameter region may be probed at a future 100 TeV collider, upcoming lepton flavor violation experiments such as Mu3e, and neutrinoless double beta decay experiments. Additionally, the tensor-to-scalar ratio from the inflationary scenario will be probed by the LiteBIRD telescope, and observable isocurvature perturbations may be produced for some parameter choices. In this article, we present all the technical details of our calculations and further discussion of its phenomenological implications.

Neil Barrie

Japan

Hitoshi Murayama

Type II Seesaw leptogenesis