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All that Antimatters in the Universe
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503/1-001 - Council Chamber (CERN)
Fiorenza Donato
(Torino University),
Luigi TIBALDO
(IRAP, Université de Toulouse),
Miguel Escudero Abenza
(CERN),
Peter von Ballmoos
(IRAP)
Description
Rationale
The origin of the matter-antimatter asymmetry in the Universe remains an unsolved enigma that requires physics beyond the standard model.
The dominant paradigm today is that from a very early phase the Universe has been composed almost exclusively of matter. Yet, we have high-quality astrophysical and cosmological observations that hold the potential to quantify the presence of antimatter in the Universe far beyond what has been done to date.
This workshop seeks to bring together theorists, observers and experimentalists working on antimatter and related fields. Together, we will discuss how recent and forthcoming observations of the Universe can provide new insights into the origin of the matter-antimatter asymmetry.
Topics
Local Universe: cosmic-ray antinuclei, gamma rays from antimatter annihilation, unidentified gamma-ray sources
Large-scale Universe: cosmic backgrounds (gamma rays, microwaves, radio, gravitational waves ...), Big-Bang nucleosynthesis, history of large-scale structures, galaxy and star formation
Theory: baryogenesis, alternative models of the matter-antimatter asymmetry, CP and CPT violation
Experiments: precision measurements of antimatter systems, CP violation with collider and neutrino experiments, antinuclei
This is a CERN-TH Institute with additional support by Action Thématique Phénomènes Extrêmes et Multi-messagers (ATPEM) and Cosmologie et Galaxies (ATCG) of CNRS/INSU PN Astro with INP and IN2P3, co-funded by CEA and CNES.
TH secretariat
Participants
218
View full list
Zoom Meeting ID
65451462182
Host
TH Computer Support
Alternative hosts
Elena Gianolio, Miguel Escudero Abenza
Passcode
89380266
Useful links
Join via phone
Zoom URL
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08:30
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1
Welcome - workshop aims 503/1-001 - Council ChamberSpeaker: Luigi TIBALDO (IRAP, Université de Toulouse)
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Early Universe and Cosmology 503/1-001 - Council ChamberConvener: Luigi TIBALDO (IRAP, Université de Toulouse)
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The Quest for the Mechanism behind the Matter-Antimatter AsymmetrySpeaker: Julia Harz
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10:30
Coffee break
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Early Universe and Cosmology 503/1-001 - Council ChamberConvener: Anthony BANDAY (IRAP)
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Big Bang nucleosynthesis mattersSpeaker: Alexandre Arbey (Lyon U. & CERN TH)
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4
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12:45
Lunch break
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Early Universe and Cosmology 503/1-001 - Council ChamberConvener: Miguel Escudero Abenza (CERN)
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7
Electroweak Baryogenesis Without New Sources of CP Violation
We investigate the feasibility of electroweak baryogenesis without new sources of CP violation. In particular, we show how finite-temperature corrections to the fermion dispersion relations arising at the 2-loop level can enhance the left–right asymmetry generated at the bubble walls by many orders of magnitude compared to conventional estimates. With only the Standard Model's particle content, though, the resulting particle–antiparticle asymmetry is still not sufficient to explain the baryon asymmetry of the Universe. We therefore investigate also models with non-minimal (but still CP-symmetric) Higgs sectors as a means to further enhance the asymmetry.
Speaker: Dr Sonali Patnaik (Indian Institute of Technology, Guwahati) -
8
Connecting the baryons to the dark matter of the Universe
The existence of dark matter in our Universe and the existence of an asymmetry between nucleons and antinucleons are two of the most solid evidences for physics beyond the Standard Model. Many mechanisms have been proposed to explain these two phenomena. On the other hand, these mechanisms typically involve different particles and different energy scales, therefore the observed similarity between the dark matter abundance and the nucleon abundance is merely coincidental. In this talk we will propose a scenario that can accommodate the observed nucleon-antinucleon asymmetry without fulfilling the Sakharov conditions. Further, our scenario predicts a stable dark matter candidate without invoking new ad-hoc symmetries, and with an abundance which is in the ballpark of the observed value.
Speaker: Alejandro Ibarra (Technical University of Munich) -
9
Revisiting baryogenesis contraints on primordial magnetic field
The decay of helical primordial magnetic fields during electroweak symmetry breaking may contribute to the generation of the baryon asymmetry of the Universe through the chiral (Adler-Bell-Jackiw) anomaly. We put constraints on the parameter space of the field strength and correlation length of such helical magnetic fields at the time of sphaleron freeze-out by requiring that their decay does not overproduce the observed baryon asymmetry. Furthermore, we account for the evolution of the primordial magnetic fields to explore whether they can account for the present-day intergalactic magnetic fields lower bounds. We also investigate whether the parameters of helical or non-helical magnetic fields consistent with baryon asymmetry bounds yield baryon isocurvature perturbations compatible with current observational limits from BBN.
Speaker: Erdenebulgan Lkhagvadorj -
10
Blocking Mesogenesis
Mechanisms of Mesogenesis generate the baryon asymmetry and dark matter of the Universe through late-time decays of standard model mesons $B_{\rm SM}$ into standard model baryons $\mathfrak{B}$ and dark matter states $\psi$: $B_{\rm SM}\rightarrow\mathfrak{B} \psi$.
Terrestrial experiments measuring $\rm{BR}\left(B_{\rm SM}\rightarrow\mathfrak{B} \psi\right)$ seem to constrain the generation of baryon asymmetry such that extra sources of CP violation, beyond the standard model, are needed.
However, by introducing an early-time phase transition (at $T\sim$ MeV) that increases the mass of $\psi$ by $\mathcal{O}(100-1000\rm{MeV})$ near the kinematic threshold of the process $B_{\rm SM}\rightarrow\mathfrak{B} \psi$, we show that much less CPV is needed, down to the level present in the standard model. We denote this mehcnaism $\mathfrak{B}$locking Mesogenesis.
We discuss this mechanism for both $B$ and $D$ mesons, along with the relevant terrestrial constraints in each case.Speaker: Jared Goldberg (Technion (Israel Institute of Technology)) -
11
Baryogenesis and EDMs in 2HDMS (R)
We explore baryogenesis and EDMs in a model with two Higgs doublets, a complex scalar and a Majorana fermion. In this model, $CP$-violation first arises from the singlet decay into the Higgs doublets, is converted into a $B-L$ charge by interactions with the Majorana fermion and finally into a $B$ asymmetry via weak sphalerons. We evaluate the outcome of baryogenesis and the EDM contributions numerically and find that, due to resonant enhancement, baryogenesis is possible with singlet masses as low as $10^6$ GeV, for which the model can give large contributions to the electron EDM, close to current experimental bounds.
Speaker: Edward Wang (Technical University of Munich (TUM)) -
12
Zero-temperature baryon number violation from the dynamics of Standard Model electroweak textures
It was recently shown that baryon number in the Standard Model
can be efficiently violated at zero temperature, from Higgs bubble collisions in
a strongly first-order electroweak phase transition [2508.21825], thus opening up new
possibilities of realizing electroweak baryogenesis in models with a low reheat
temperature and large bubble wall velocity. In this study, the production of baryon number can be attributed to the dynamics of electroweak textures which are non-trivial Higgs field configurations formed upon spontaneous
electroweak symmetry breaking. Textures can decay leading to transitions in the Chern-Simons
number, which is converted into baryon number via the Standard Model chiral
anomaly. This work has been carried out by relying on large-scale (3+1)D
real-time lattice simulations of the Higgs and SU(2)-gauge bosons, where true
vacuum critical bubbles are nucleated at initial time.
There are many ways in which
this first analysis could be improved and extended: by adding the
hypercharge gauge boson, adding plasma effects, studying the non-runaway
regime, and most importantly, adding CP-violation in the simulations, which I will discuss in this presentation.Speaker: Martina Cataldi (University of Hamburg)
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7
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15:30
Coffee break
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Early Universe and Cosmology 503/1-001 - Council ChamberConvener: Anastasia Fialkov
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13
The Radio Synchrotron Background - An Astrophysical Anomaly
It has become apparent that the background brightness level of diffuse radio emission on the sky and its level of anisotropy are significantly higher than those which can result from known classes of astrophysical radio sources. This is in contrast to the more well-known photon backgrounds at microwave, infrared, optical/UV, X-ray, and gamma-ray wavelengths, where the levels of brightness and anisotropy at least roughly match those expected from known cosmological and astrophysical sources. Thus the "radio synchrotron background" at radio wavelengths represents a mystery in astrophysics and cosmology, and provides clear motivation for considering new physics and new emission mechanisms. This talk will review the state of knowledge of the radio background and its potential interplay with signals from 21-cm cosmology and beyond-standard-model physics, the latter including a model in which dense nuggets of antiquarks exist in the universe.
Speaker: Jack Singal (University of Richmond) - 14
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15
Electroweak baryogenesis with relativistic bubbles walls
We present a novel mechanism which leads to the baryon asymmetry generation during the strong first order phase transition. If the bubble wall propagates with ultra-relativistic velocity, it has been shown [1] that it can produce states much heavier than the scale of the transition and that those states are then out of equilibrium. In this paper, we show that this production mechanism can also induce CP-violation at one-loop level. We calculate those CP violating effects during the heavy particle production and show, that combined with baryon number violating interactions, those can lead to successful baryogenesis. Two models based on this mechanism are constructed and their phenomenology is discussed. Stochastic gravitational wave signals turn out to be generic signatures of this type of models.
Speaker: Miguel Etienne A Vanvlasselaer (ICCUB) -
16
Primordial black holes and antistars (R)
A mechanism of antistar formation in the Galaxy is reviewed. Observational consequences are analysed.
Speaker: Alexander Dolgov
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13
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Poster session and reception
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17
Shedding Light on Antinuclei Production with Femtoscopy in High-Energy Nuclear Collisions
High-energy nuclear collisions provide a unique environment for synthesizing antinuclei at temperatures around $T\sim100$ MeV. Their production mechanisms have, however, remained an open question. By solving relativistic kinetic equations for pion-catalyzed reactions for deuteron regeneration and disintegration in $pp$ collisions at $\sqrt{s}=13$ TeV, we find pronounced resonance peaks in the momentum correlations (femtoscopy) of both $\pi^+-p$ and $\pi^+-d$ pairs. These peaks are found to be generated by the formation of intermediate $\Delta$ resonances in the reaction channels. Our results are in good agreement with the preliminary ALICE measurements, and suggest that pion-catalyzed reactions play a dominant role in light (anti-)nuclei production in high-energy nuclear collisions and cosmic rays.
Speaker: LIYUAN ZHANG (Fudan Universiy) -
18
(Anti-)Helium-3 and (Anti-)Hypertriton Flow in Pb+Pb Collision at \texorpdfstring{$\sqrt{s_{NN}}=5.36$}{} TeV
Anisotropic flow of light nuclei provides a unique probe of the space-time evolution and hadronization dynamics in relativistic heavy-ion collisions. We investigate the elliptic ($v_2$) and triangular ($v_3$) flow of (anti-)protons, (anti-)deuterons, and (anti-)Helium-3 in Pb+Pb collisions at $\sqrt{s_{NN}} = 5.36$ TeV within a coalescence framework based on nucleon phase-space distributions from the MUSIC hybrid model. Our study demonstrates that the conventional nucleon-number ($A$) scaling of $v_2$ breaks down at high transverse momentum ($p_T/A > 1.5$~GeV), while an improved scaling relation remains valid up to $p_T/A \approx 3$~GeV. For $v_3$, both scaling prescriptions lead to nearly identical results. We further provide the first predictions for the flow of (anti-)hypertriton and show that they are insensitive to its internal structure. These findings can be directly tested with forthcoming ALICE measurements and offer new insights into the production mechanisms of light (anti-)(hyper-)nuclei in high-energy heavy-ion collisions.
Speaker: Fu Ma -
19
Developments towards quantum logic spectroscopy for high-precision g-factor measurements of (anti-)protons in a cryogenic Penning trap
Multi-Penning trap experiments have proven to be excellent for CPT symmetry tests in the context of the search for physics beyond the Standard Model. The BASE collaboration contributes to these tests by measuring the charge-to-mass ratios and $g$-factor ratios of protons and antiprotons in a cryogenic multi-Penning trap system [1-3]. BASE Hannover is developing new measurement schemes based on sympathetic cooling and quantum logic spectroscopy to further reduce measurement time and the statistical uncertainty, using $^9$Be$^+$ both as cooling and logic ion [4].
This contribution will give an overview of our experimental setup, highlighting recent changes we implemented, including upgrades on the laser systems as well as a new Penning trap stack. Furthermore, recent key milestones, including ground-state cooling and fast adiabatic transport of a single $^9$Be$^+$ ion will be presented in the context of our measurement scheme [5,6].[1] Schneider et al., Science 358, 1081 (2017).
[2] Smorra et al., Nature 550, 371 (2017).
[3] M.J. Borchert et al., Nature 601, 53 (2022).
[4] Cornejo et al., New J. Phys. 23, 073045 (2021).
[5] Cornejo et al., Phys. Rev. Research 6, 033233 (2024).
[6] von Boehn et al., Commun. Phys. 8, 107 (2025).Speaker: Jan Schaper -
20
Simulating Motional Ground-State Cooling of (Anti-)Protons in a Microfabricated Cylindrical Penning Trap
High-precision experiments on isolated cold (anti-)particles provide some of the most stringent tests of CPT symmetry [1,2]. In particular, if cooled to the motional ground state, the magnetic moment of the (anti-)proton could be measured using quantum logic spectroscopy [3,4], contributing to improving the proton–antiproton comparison beyond the parts-per-billion precision achieved by the BASE collaboration [5,6]. At BASE Hannover, we aim to sympathetically cool the (anti-)proton by coupling it via the Coulomb interaction to a single laser-cooled $^9$Be$^+$ ion [7] confined in a double-well potential of a cryogenic microfabricated cylindrical Penning trap. The 9:1 mass ratio of these particles poses a challenge: the shallow trapping potential allows 4 K (anti-)protons to explore anharmonic regions of the potential. We present simulations showing that frequency-swept trapping potentials mitigate these anharmonicities, keeping the (anti-)proton and $^9$Be$^+$ ion in resonance. We also quantify the harmonic region and analyze the robustness of our energy exchange protocol against voltage fluctuations. This approach could open a path to ground-state cooling of laser-inaccessible (anti-)particles in a Penning trap, thereby extending precision tests of fundamental symmetries.
[1] R. Lehnert et al., Symmetry 8, 114 (2016).
[2] M. J. Borchert et al., Nature 601, 53-57 (2022).
[3] J. M. Cornejo et al., New J. Phys. 23, 073045 (2021).
[4] P. O. Schmidt et al., Science 309, 749-752 (2005).
[5] C. Smorra et al., Nature 550, 371-374 (2017).
[6] G. Schneider et al., Science 358, 1081-1084 (2017).
[7] J. M. Cornejo et al., Phys. Rev. Res. 6, 033233 (2024).Speaker: Mr Nikita Poljakov (Institut für Quantenoptik, Leibniz Universität Hannover, Germany) -
21
Pre-Supernova Neutrinos as a Multimessenger Probe of Fundamental Physics
Pre-supernova neutrinos, emitted in the final stages of massive star evolution, provide a rare early signal of an imminent core-collapse. My research focuses on extracting directional information from these neutrinos via elastic scattering in large-scale detectors like Hyper-Kamiokande, enabling rapid follow-up by astronomical observatories.
I present simulation results on expected event rates, energy spectra, and pointing accuracy, highlighting how pre-supernova neutrino observations complement studies of neutrino properties, CP violation, and matter–antimatter asymmetry. This approach connects astrophysical observations with fundamental physics questions, offering a unique multimessenger perspective that complements accelerator and collider experiments.
Results will be shared through both an oral and a poster contribution, demonstrating the potential of pre-supernova neutrinos to provide insights into the Universe’s fundamental asymmetries while illustrating the role of neutrino astrophysics in interdisciplinary research.
Speaker: Assia El Kaftaoui (The Scientific Program of ASP2021) -
22
Antimatter Detection with Gamma-Ray and AntiMatter survey(GRAMS) experiment
GRAMS (Gamma-Ray and AntiMatter Survey), one of the NASA Physics of the Cosmos experiments, targeting both MeV gamma-ray observations and antimatter-based indirect dark matter searches. With a low-cost, large-scale Liquid Argon Time Projection Chamber (LArTPC) detector, GRAMS can provide significantly improved sensitivities to gamma rays in a historically under-explored energy regime often referred to as the MeV Gap. GRAMS can also extensively probe a new dark matter parameter space via low-energy antinuclei measurements, including the regions suggested by the Fermi Galactic Center Excess and AMS-02 antiproton excess. GRAMS will conduct a background-free indirect dark matter search by detecting low-energy antinuclei, especially antideuterons and antiheliums, while exploring various dark matter models.
We've had a successful engineering balloon flight in Japan in 2023, which is the first ever LArTPC detector operated in the stratosphere, and performed an antiproton beam test at J-PARC in 2025. GRAMS has been funded by NASA for a prototype (pGRAMS) balloon flight, which is planned for early 2026 from Tucson, Arizona.
Speaker: Jiancheng Zeng -
23
Baryogenesis in modified gravity
This presentation aims to recreate the gravitational baryogenesis epoch in the framework of the $f(R,L_m)$ theory of gravity, where $R$ and $L_m$ are the curvature scalar and the matter Langragian, respectively. In particular, we examine the model, $f(R,L_m) = \frac{R}{2} + L_m ^{\alpha} + \zeta$, under the supposition that the universe is saturated with dark energy and perfect fluid, with a non-zero baryon to entropy ratio during a radiation dominance era. We confine the model with the gravitational baryogenesis scenario, emphasizing the appropriate values of model parameters compatible with the baryon-to-entropy ratio observation data.
Our study found that $f(R,L_m)$ gravity can considerably and steadily make a contribution to the phenomenon of gravitational baryogenesis.Speaker: Prof. Pradyumn Kumar Sahoo (Birla Institute of Technology and Science-Pilani, Hyderabad Campus) -
24
Low-energy antineutron scattering off protons and nuclei
Nucleon–antinucleon interactions at low energies are not well understood, unlike nucleon-nucleon interactions, because of the absence of low-energy data [1,2,3]. To address this issue, we are proposing a novel method to produce antiprotons with unprecedented low energies by using a charge-exchange reaction (p pbar --> n nbar) with antiproton beams supplied from the Antiproton Decelerator [2,4]. The momentum of backward-produced antineutrons will be as low as 9 MeV/c, which enables us to investigate s-wave antineutron-proton and antineutron-nucleus scattering lengths, by means of scattering measurements. In particular, the latter has not been determined directly so far, despite being an important quantity in planning neutron-antineutron oscillation search experiments [5].
[1] J. Carbonell, G. Hupin, and S. Wycech, Eur. Phys. J. A 59, 259 (2023).
[2] A. Filippi, H. Fujioka, T. Higuchi, and L. Venturelli, arXiv:2503.06972.
[3] A. Filippi, arXiv:2601.11390
[4] C. Amsler, D. Calvo, A. Feliciello, A. Filippi, H. Fujioka, T. Higuchi, and L. Venturelli, "Low-Energy Antineutron Beamline at the Antiproton Decelerator for Scattering Experiments", CERN-SPSC-2025-010, SPSC-I-261.
[5] H. Fujioka and T. Higuchi, arXiv:2508.17725; accepted for publication in Prog. Theor. Exp. Phys.Speaker: Hiroyuki Fujioka (Institute of Science Tokyo (JP)) -
25
Neutron–Antineutron Oscillations with Stored Ultracold Neutrons
Neutron–antineutron ($n$–$\bar{n}$) oscillations, which violate $\mathcal{B}$ and $\mathcal{B}-\mathcal{L}$ conservation ($\mathcal{B}$: baryon number, $\mathcal{L}$: lepton number), constitute powerful probes of physics beyond the Standard Model, with profound implications for the baryon asymmetry of the universe [1]. The most stringent experimental limits to date constrain the oscillation time to $\tau_{n-\bar{n}}>0.86\times 10^8$ s for free neutrons and $>4.7\times 10^8$ s for neutrons bound in nuclei [2,3]. The conventional experimental method for free neutrons employs a beam traversing a vacuum [2,4]. A promising but as yet unrealized alternative involves the use of stored ultracold neutrons (UCNs), which allow orders-of-magnitude longer observation times and more compact experimental setups. Recent advances in superthermal UCN sources have achieved much higher UCN densities than conventional sources, rendering this approach newly practical. Optimizing such experiments, however, requires precise knowledge of low-energy antineutron–nucleus interactions, particularly for the coating materials used in UCN storage vessels [5].
To address this need, we propose a novel low-energy antineutron beamline in the Antiproton Decelerator at CERN, capable of delivering antineutrons with kinetic energies down to $40~\mathrm{keV}$ and enabling direct determinations of antineutron–nucleus scattering lengths [6]. These studies will inform the design of next-generation UCN storage experiments and will also improve the beam-type experiments. Furthermore, they are expected to provide crucial input for refining models of low-energy antinucleon–nucleon interactions.In this presentation, we explain the motivation, methodology, and anticipated impact of the proposed program, and outline how improved knowledge of antinucleon–nucleus interactions can substantially enhance the sensitivity of future neutron–antineutron oscillation searches.
[1] D.G. Phillips II et al., Physics Reports 612$\,$(2016)$\,$1.
[2] M. Baldo-Ceolin et al., Z. Phys. C 63$\,$(1994)$\,$409.
[3] K. Abe et al., Phys. Rev. D 103$\,$(2021)$\,$012008.
[4] F. Backman et al., JINST 17$\,$(2022) P10046.
[5] H. Fujioka and T. Higuchi, arXiv:2508.17725.
[6] C. Amsler et al., CERN-SPSC-2025-010$\,$(2025).Speaker: Takashi Higuchi (Kyoto University (JP)) -
26
Slow Positronium Beams at AEGIS
Slow positronium (Ps) beams form a cornerstone of AEgIS’s mission to advance precision antimatter physics. They enable detailed spectroscopic studies of excited and Rydberg Ps states, offering stringent tests of bound-state QED and new insight into Ps dynamics in combined electric and magnetic fields. Controlled production and manipulation of such states are crucial for efficient antihydrogen formation via charge exchange with trapped antiprotons, a central goal toward precision measurements of antimatter gravity. Future developments in beam brightness, coherence, and timing control will further extend Ps research into the realms of quantum interferometry and field-sensitive spectroscopy. These capabilities position slow Ps beams as an essential platform linking atomic physics, antimatter production, and precision measurement science within and beyond the AEgIS experiment.
Speaker: Benjamin Rienacker (University of Liverpool (GB)) -
27
Towards Antiproton Transport with the BASE-STEP Apparatus
The BASE collaboration performs the world’s most precise tests of CPT invariance in the baryon sector, using advanced cryogenic Penning-trap systems to measure the fundamental properties of single trapped protons and antiprotons [1,2]. However, magnetic-field fluctuations originating from CERN’s AD and ELENA decelerators currently limit measurement resolution and present a major obstacle to further progress within practical experimental timescales. To address this challenge, we have developed BASE-STEP [3], a novel, autonomous, open, and transportable Penning-trap system designed to relocate antiprotons to magnetically quiet environments. Together with our offline experiments, currently under development at Heinrich Heine University (HHU) Düsseldorf and planned at CERN, our strategy will enable next-generation CPT tests with a targeted precision improvement of at least two orders of magnitude over current experiments at CERN’s Antimatter Factory.
In this presentation, we will report on recent major milestones demonstrating the feasibility of antiproton transport. During our 2024 proton campaign, we successfully loaded protons, transported the system by truck outside the Antimatter Factory, and returned the proton reservoir intact [4]. Most recently, BASE-STEP was deployed to our dedicated offline precision laboratory at HHU Düsseldorf, where we performed frequency stability measurements on single protons. Building on insights from the 2024 campaign, we implemented a series of system upgrades and successfully returned BASE-STEP to CERN for its first antiproton beamtime in 2025. We will present ongoing developments and results of the BASE-STEP antiproton campaign and discuss efforts aimed at enabling antimatter trap operation on public roads, opening transformative possibilities for future experiments in precision antimatter physics, particularly with antiprotons and molecular antihydrogen ions.
[1] C. Smorra et al., Nature 550 (2017): 371–374
[2] M. Borchert et al., Nature 601 (2022): 53–57
[3] C. Smorra et al., Rev. Sci. Instrum. 94 (2023)
[4] M. Leonhardt et al., Nature 641 (2025): 871–875Speaker: Marcel Leonhardt (Heinrich Heine University Dusseldorf (DE)) -
28
Vacuum decay in theories with no instantons
In a quantum field theory, a metastable vacuum state can decay through quantum tunnelling. The calculation of the decay rate relies on instantons — non-trivial saddle points of the Euclidean action. However, sometimes theories with metastable vacua do not have any instanton solutions, thus rendering the usual method of calculating decay rates unusable. An important example of such a theory is the Electroweak theory, where vacuum decay is directly related to baryon number violation, but where there are no instanton solutions to mediate the decay.
In this talk, I will discuss a method for computing the decay rate in theories with no exact instanton solutions using constrained instantons. It is based on a perturbative approach by Affleck from the 1980s, which we have generalised and made fully non-perturbative. I will begin by outlining the method in general, and I will then apply it to a simple toy model - a single, real, massive scalar field in 4 dimensions. I will conclude by discussing how this method can be generalised to include gauge fields, and how it can be applied to study the electroweak vacuum decay.
Speaker: Kinga Gawrych (Imperial College London)
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17
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08:30
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Early Universe and Cosmology 503/1-001 - Council ChamberConvener: Julia Harz
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29
Electroweak baryon number violation in the lab?
The Standard Model predicts baryon number violation through the anomalous U(1) B+L symmetry, but in vacuum this process is exponentially suppressed by the sphaleron energy barrier and therefore it has never been observed. The suppression disappears in the high temperatures of the early Universe, making this an important ingredient for explaining the observed matter-antimatter asymmetry in the Universe. In this talk, I demonstrate that strong magnetic fields would also catalyse the process, to the extent that the sphaleron barrier disappears completely above the upper Ambjorn-Olesen field strength of around 10^20 tesla. Magnetic fields of this strength are currently beyond our reach but could be produced for a very short time with a heavy ion collider encircling the whole Moon. I discuss whether this could allow us to achieve electroweak baryon number violation in the lab.
Speaker: Prof. Arttu Rajantie (Imperial College London) -
30
B-Mesogenesis Against the Ropes: Flavor Decoherence and BBN
The B-Mesogenesis mechanism aims to explain the baryon asymmetry of the Universe and the dark matter abundance through CP-violating oscillations and subsequent decays of B-mesons in the early Universe, at temperatures just before BBN (T ≃ 5–20 MeV). In this work, we show that the photo-dissociation process γ + B⁰ → B⁰⋆, which was not included in the original studies, is the most effective source of decoherence for CP-violating oscillations. By providing a first principles calculation of the mechanism and including this process, we find that its efficiency is reduced by a factor of 2–100, depending on the effective reheating temperature in the model. Furthermore, solving for BBN within this mechanism, we find that consistency with observations requires T_RH > 5.3 MeV. Together, these results imply that the required CP asymmetries and branching ratios of B mesons into baryons and missing energy must be at least a factor of 10 larger than previously expected. Overall, the mechanism appears to be in tension with the absence of new-physics signals in these laboratory observables and may already be experimentally excluded.
Speaker: Martha Ulloa (University of Florida) -
31
Hot Spots from Evaporating Black Holes as Engines for Electroweak Baryogenesis
We propose a new pathway to the baryon asymmetry in which small primordial black holes (PBHs) act as localized, short-lived baryogenesis engines after the electroweak phase transition (EWPT). Hawking emission from evaporating PBHs deposits energy into the surrounding plasma, creating over-pressured hot spots that drive near-acoustic shock fronts. Inside these fronts the Higgs expectation value is driven to the symmetric phase while remaining broken outside, yielding moving interfaces that source chiral charge; active sphalerons in the restored regions then convert this into baryon number. We compute the time-dependent Hawking power across Standard Model species, estimate the microscopic Landau–Pomeranchuk–Migdal thermalization length that sets the initial hot-spot size, and solve the hydrodynamics of the expanding front. Adapting electroweak baryogenesis methods to moving walls, we derive the resulting baryon yield for PBH populations with realistic time-dependent mass functions resulting from critical collapse theory. Crucially, the mechanism supplies the needed out-of-equilibrium dynamics without requiring new physics to render the EWPT first order.
Speaker: Alexandra Klipfel -
32
Reviving the $\nu$MSM in the $\nu$SMEFT
Explaining the origin of the matter–antimatter asymmetry remains one of the central open questions in particle cosmology. The $\nu$MSM offers an appealing framework in which low-scale leptogenesis and sterile-neutrino dark matter arise from a minimal extension of the Standard Model. However, successful leptogenesis requires a highly tuned mass degeneracy among the right-handed neutrinos, and the dark-matter component is even more tightly constrained by X-ray observations. In this talk, I investigate how higher-dimensional operators in the neutrino-extended Standard Model Effective Field Theory ($\nu$SMEFT) can reopen and reshape this parameter space. Focusing on a specific dimension-six, lepton-number–conserving operator, I demonstrate its impact on low-scale leptogenesis from oscillations of two right-handed neutrinos and show how the same operator influences sterile-neutrino dark-matter production. I further connect these effects to correlated predictions for neutrinoless double beta decay, highlighting how $\nu$SMEFT corrections link the baryon asymmetry of the Universe with upcoming laboratory probes.
Speaker: Sascha Weber (Johannes Gutenberg-Universität Mainz) -
33
Antimatter and dark matter glow
I will discuss the observational signatures of a QCD-based dark-matter scenario first proposed in 2003 by Zhitnitsky. If the QCD axion exists, a charge-separation mechanism during the QCD phase transition can confine quarks and antiquarks into macroscopic nuggets (with masses of at least a few grams) even as widespread matter–antimatter annihilation proceeds. These nuggets are stable and persist to the present day. In this framework, roughly half of the dark matter consists of antimatter nuggets, the universe’s net baryon number remains zero at all times (eliminating the need for baryogenesis), and the baryonic and dark-matter density parameters naturally take similar values, consistent with observations. Interactions between antimatter nuggets and ordinary matter generate a range of testable astrophysical signatures—i.e., dark matter may emit faint electromagnetic glow. The new space-based observatories Euclid and JWST have the sensitivity to detect such emission. Across the electromagnetic spectrum (from radio to UV) and over multiple cosmic epochs, a characteristic dark-matter glow is expected that targeted observations could search for. I will review current detection limits and outline realistic prospects for a decisive detection in the next few years.
Speaker: Prof. Ludovic Van Waerbeke
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29
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10:30
Coffee break
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Discussion session: antimatter in cosmology 503/1-001 - Council Chamber
Is there any room within current observations for some antimatter to have survived beyond the baryogenesis epoch? Are there new avenues to test this hypothesis through astrophysical and cosmological observations?
Convener: Valerie Domcke -
12:45
Lunch break
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CP and CPT symmetries 503/1-001 - Council Chamber
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CP vs. CPT Violation: More Than Just a Letter ApartSpeaker: Gabriela Barenboim (IFIC & University of Valencia)
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CP violation at collider experimentsSpeaker: Peilian Li (University of Chinese Academy of Sciences)
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15:30
Coffee break
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Convener: Peilian Li (University of Chinese Academy of Sciences)
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CP violation at neutrino experimentsSpeaker: Anne Elizabeth Norrick (Fermi National Accelerator Lab. (US))
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Leptogenesis and light sterile neutrinos (R)
We will discuss leptogenesis in the context of a minimal extended seesaw scenario which can accommodate an eV scale sterile neutrino. It also includes three heavy right handed neutrinos. The active-sterile mixing angles characterize the deviation from Unitarity of the PMNS matrixwhich in this model can be of O(0.1) induced by the light sterile neutrino. We study vanilla leptogenesis in this scheme, where the decay of the heavy right handed neutrinos in the early universe can give rise to theobserved baryon asymmetry. Here, even though the eV scale sterile neutrino does not participate directlyin leptogenesis, its effect is manifested through the non-unitary effects. We find that the parameter spacethat can give rise to successful leptogenesis is constrained by the bounds on the active-sterile mixing angles obtained from the global analysis.
Next, we implement the extended seesaw in a class of left-right symmetric model, where fermion masses are induced through a universal seesaw mechanism. This scenario has a minimal scalar sector with two Higgs Doublets but the fermion sector is enlarged to include additional gauge singlets. We show that leptogenesis can work in this model even with a single generation because the parity doubling leading to the presence of gauge singlet fermions $N_L$ and $N_R$ can account for the $CP$ violation. For the case of exact or approximate parity symmetry we predict a right handed neutrino with mass $m_{\nu_R}< {10} {\mathrm{ eV}} $ , lightest active neutrino mass $m_{\nu_L}< \mathcal{O}((10^{-9}-10^{-3})\;\text{eV})$ and a mixing angle $\mathcal{O}(10^{-5})>\theta_{LR} > \mathcal{O}(10^{-2})$.Speaker: Prof. Srubabati Goswami (Physical research laboratory)
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Antimatter experiments at low energies 503/1-001 - Council ChamberConvener: Dr Barbara Maria Latacz (CERN)
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Antimatter experiments at low energiesSpeaker: Prof. Klaus (KHKJ) Jungmann (University of Groningen)
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Antiprotons Under the Precision Microscope
The BASE collaboration is performing the most precise measurements of the fundamental properties of the proton and the antiproton. Charge-to-mass ratios were compared with a fractional resolution on the 16 parts in a trillion level, and coherent antiproton spin spectroscopy will establish measurements on the sub-parts per billion level. In addition to these world-record measurements, we have used our data to set limits on antiproton/dark matter coupling and parameter-ranges in which milli-charged dark matter can exist. In my talk I will review the achievements of the BASE collaboration since the start of the program, and will give an outlook on the future strategy of the collaboration. This includes antimatter transport, antiproton spectroscopy in dedicated offline laboratories, quantum-logic spectroscopy with antiprotons, advanced measurement protocols with antimatter Q-bits, and other cutting-edge projects that follow the vision to bring precision antiproton spectroscopy to ultimate resolution-limits.
Speaker: Prof. Stefan Ulmer (HHU Düsseldorf / RIKEN)
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10:00
Coffee break
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Antimatter experiments at low energies 503/1-001 - Council ChamberConvener: Michael Charlton (Swansea University)
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Testing Fundamental Physics with Antimatter Systems (R)Speaker: Dr Yevgeny Stadnik (The University of Sydney)
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Antihydrogen yield in AD experiments
ASACUSA produces millions of antihydrogen atoms in every 15-minute experimental cycle. Most of the atoms hit the wall of the trap and annihilate microseconds after formation, and only a small fraction, 0.1% or less, survive long enough to be used in our spectroscopy apparatus. This statement is true of all trap-based experiments (AEgIS, ALPHA, and ASACUSA), and it motivates us to further increase the antihydrogen yield. All AD antihydrogen groups claim an order of magnitude increased yield in the last two years, with similar increases possible in the near future. This will have a secondary effect of increasing production of other species such as the positive antihydrogen ion (the focus of GBAR), which are so far not observed. In this presentation, I will compare the steps being taken by each group to increase the antihydrogen yield in their experiments. I will summarize the expected outcomes for the simplest species ($\bar{\mathrm{H}}$, $\bar{\mathrm{H}}^+$, and $\bar{\mathrm{H}}_2^-$) for both present and short-term projected experimental capabilities.
Speaker: Eric Hunter (CERN) -
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Coherent spectroscopy with a single antiproton spin for the antiproton magnetic moment measurements in BASE
BASE - The Baryon-Antibaryon Symmetry Experiment - is dedicated to conduct ultra-precise tests of Charge Parity Time reversal invariance by comparing key intrinsic properties of protons and antiprotons, such as their charge-to-mass ratios, lifetimes, and magnetic moments.
In this presentation, we will highlight our flagship experiment at CERN, which is currently focused on achieving 10- to 100-fold improved measurements of proton and antiproton magnetic moments. To date, we have determined these quantities with fractional uncertainties of 1.5 parts per billion [1] for the antiproton and 300 parts per trillion [2] for the proton.
Recent progress has been driven by major technical upgrades, including the implementation of a superconducting shielding and shimming system and a newly developed cooling trap [3] that provides vastly enhanced cyclotron-mode cooling performance. These advances have enabled 100%-fidelity, non-destructive spin-state spectroscopy of single antiprotons [3]. In this significant experimental upgrade, we successfully suppressed numerous decoherence mechanisms, culminating in the first non-destructive coherent spectroscopy of a single antiproton spin. In these experiments we have achieved a spin coherence time of 50 seconds, and full control over the linewidth of the g-factor resonance. Using coherence times of 10 s we achieved a sixteenfold reduction in spectral linewidth compared to previous measurements. This represents the first demonstration of an antimatter quantum bit (qubit) and paves the way for much more precise comparisons between the behavior of matter and antimatter.
We will present the recently published results on coherent antiproton spin spectroscopy and discuss ongoing efforts aimed at further improving the precision of both antiproton and proton magnetic moment measurements.
1. C. Smorra, et al., Nature 550.7676 (2017): 371-374.
2. G. Schneider, et al., Science 358.6366 (2017): 1081-1084
3. B. M. Latacz, et al., Phys. Rev. Lett. 133.5 (2024): 053201
4. B. M. Latacz, er al., Nature 644, 64–68 (2025)Speaker: Dr Barbara Maria Latacz (CERN) -
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Advances towards measuring the gravitational free-fall of an antiatom beam at the AEgIS experiment
The AEgIS (Antimatter Experiment, Gravity, Interferometry, and Spectroscopy) experiment,
based at CERN’s Antiproton Decelerator facility, aims to perform gravitational experiments
using beams of neutral antiatoms (antihydrogen and positronium) in the absence of external
fields. A key objective of AEgIS is to make the first direct measurement of the free-fall
acceleration of antihydrogen and to explore, at unprecedented precision, whether antimatter
obeys the Weak Equivalence Principle (WEP). To this end, the collaboration has developed a
suite of innovative techniques for the formation, manipulation, and precision measurement of
antiatom beams.
The experiment pioneered the concept of a moiré deflectometer adapted for neutral antiatom
beams, offering a robust method to detect gravitational sag over a meter-scale flight path [1].
Central to this effort is the creation of a pulsed source of antihydrogen, produced via charge-
exchange between cold antiprotons and Rydberg-state positronium, first demonstrated in 2020
and recently enhanced by more than an order of magnitude, enabling the first statistically
significant beam-like production of antihydrogen [2]. Furthermore, the collaboration
commissioned a new position-sensitive detector with sub-micrometre spatial resolution for
antihydrogen and antiproton annihilation events, enabling precise tracking of individual beam
particles [3].
These advances revealed the crucial role of anti-atomic temperature in achieving beam
collimation, motivating continuous developments toward colder and brighter sources leading,
for example, to the first experimental demonstration of positronium laser cooling - an essential
stepping stone for high-precision experiments employing Ps [4].
Prospects include: (i) directly measuring the gravitational free-fall of a horizontally boosted
antihydrogen beam, (ii) realising long-lived laser-cooled positronium sources, enabling further
constraints on the WEP with leptonic antimatter, and (iii) extending such studies to
antideuterium–should antideuteron beams become available at the AD–thereby enabling WEP
tests with antineutrons.Speaker: Ruggero Caravita (Universita degli Studi di Trento and INFN (IT)) -
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Precision laser spectroscopy of exotic helium atoms to determine the antiproton-to-electron mass ratio, and the charged pion and kaon masses
The ASACUSA collaboration of CERN carries out precision laser spectroscopy of exotic helium atoms that contain antiprotons at CERN's Antiproton Decelerator, and pions at PSI's 590 MeV Ring Cyclotron facility. In the future we plan to extend these studies to determine the antiproton-to-electron mass ratio and the charged pion mass to much higher precision than before. We are also carrying out preliminary studies for future experiments on laser spectroscopy of kaonic helium atoms at the DAPHNE facility of INFN Frascati to determine the charged kaon mass.
Speaker: Masaki Hori (Imperial College London) -
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Towards a future test of CPT Invariance by spectroscopy of H$_2^+$ and $\overline{\mathrm{H}}^-_2$
Recently, there has been impressive progress on the spectroscopy of molecular hydrogen ions, in both r.f. and Penning traps, at several laboratories (Paris, Zürich, Heidelberg, Amsterdam, Düsseldorf). This includes the first laser spectroscopy of H$_2^+$ [1, 2]. It is thus of interest to consider in more detail the proposals [3, 4] of comparing a vibrational transition frequency of H$_{2}^+$ with the analogous one in the antimatter molecule $\overline{\mathrm{H}}_2^-$. Such a comparison would offer a new opportunity to test CPT invariance, complementary to ongoing approaches. We have performed a detailed analysis of the proposal of Myers [4], to perform optical spectroscopy in a Penning trap with non-destructive read-out. This approach has recently been pioneered at ALPHATRAP [5,6]. We extend the analysis to Penning traps using quantum logic spectroscopy. We derive estimates for the achievable accuracy of the test. We find the level $1\times10^{-17}$ to be realistic, using technology mostly already available.
[1] M. R. Schenkel, S. Alighanbari, and S. Schiller, Laser spectroscopy of a rovibrational transition in the molecular hydrogen ion H$^+_ 2$, Nature Physics 20, 383 (2024).
[2] S. Alighanbari, M. R. Schenkel, V. I. Korobov, and S. Schiller, High-accuracy laser spectroscopy of H$^+_2$ and the proton-electron mass ratio, Nature 664, 69 (2025).
[3] H. Dehmelt, Economic synthesis and precision spectroscopy of anti-molecular hydrogen ions in Paul trap, Physica Scripta T59, 423 (1995).
[4] E. G. Myers, CPT tests with the antihydrogen molecular ion, Phys. Rev. A 98, 010101 (2018).
[5] C. M. König, F. Heiße, J. Morgner, T. Sailer, B. Tu, D. Bakalov, K. Blaum, S. Schiller, and S. Sturm, Nondestructive Control of the Rovibrational Ground State of a Single Molecular Hydrogen Ion in a Penning Trap, Phys. Rev. Lett. 134, 163001 (2025)
[6] C. M. König et al., High-precision Penning-trap spectroscopy of the ground-state spin structure of HD$^+$, submitted (2025)Speaker: Prof. Stephan Schiller (Heinrich-Heine-Universität Düsseldorf)
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12:30
Lunch break
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Discussion session: antimatter experiments at low energies 503/1-001 - Council Chamber
What are experiments at the Antiproton Decelerator facility teaching us about fundamental physics and the matter-antimatter asymmetry in the Universe?
Convener: Prof. Stefan Ulmer (HHU Düsseldorf / RIKEN) -
15:30
Coffee break
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Cosmic rays, antinuclei and positrons 503/1-001 - Council ChamberConvener: Mirko Boezio
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Cosmic-ray antimatterSpeaker: David Alain Maurin (Centre National de la Recherche Scientifique (FR))
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Local antimatter domains
If huge efforts have been devoted to study the astronomical dark matter, the quest for antimatter domains in our vicinity has not attracted much attention. According to the standard lore, the universe is baryon asymmetric since antimatter has vanished long ago during a primeval stage of annihilation. However we cannot dismiss the presence of tiny amounts of antimatter in the Milky Way. Actually, the AMS-02 experiment may have detected a few anti-helium events which, if confirmed, would be a smoking gun signature for such a presence. It is timely to revisit this possibility, all the more since Gary Steigman’s survey on antimatter cosmologies is half a century old.
In this talk, I will present updated bounds on the mutual contamination of matter and antimatter clouds in our local universe, based on observations by Planck and Fermi. We can go a step further, using the AMS-02 putative anti-helium events to draw information on Galactic antimatter. The possibility of anti-stars will also be touched upon. I will finally point out the necessity of a thorough investigation of the physics at the interface between matter and antimatter regions.
Speaker: P. Salati (Unite Reseaux du CNRS (FR))
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Cosmic rays, antinuclei and positrons 503/1-001 - Council ChamberConvener: P. Salati (Unite Reseaux du CNRS (FR))
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Observation and Properties of Antimatter Nuclei at the Relativistic Heavy Ion Collider
Relativistic nuclear collisions can produce the most extreme conditions of temperature and density achievable in laboratories: quark matter. Figuratively speaking, this is a “mini-Big Bang” process. The new material state created by this “mini-Big Bang” resembles the state of matter just microseconds after the cosmic Big Bang—a deconfined quark-gluon plasma. Its temperature can reach tens of trillions of degrees, exhibiting many novel properties. Rapidly evolving over time, this process generates vast quantities of positive and negative particles. This report will focus on observations and property studies of antimatter nuclei using the RHIC-STAR detector at the RHIC, including observations of several antimatter hypernuclei and anti-helium-4, as well as measurements of antiproton interactions, the mass, binding energy, and lifetime of antimatter hypernuclei.
Speaker: Prof. Yugang Ma (Fudan University (CN)) -
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Antinuclei production in high-energy nuclear collisions and atmospheric antideuteron flux
Nearly all antinuclei were annihilated during the big bang nucleosynthesis. However, they can be created and survive in the high-energy "little bangs" of nuclear collisions. This talk will cover recent progress in understanding the microscopic dynamics of this little-bang nucleosynthesis. I will also present our new results on the atmospheric antideuteron flux, a key observable in the indirect search for dark matter.
Refs: K. J. Sun et al., Nature Commun. 15 (2024) 1, 1074; J. Pu et al., JHEP 08 (2025) 002.
Speaker: Dr KaiJia Sun (Institute of Modern Physics, Fudan University, Shanghai, China) -
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Antiprotons and antideuterons from primordial black holes
In this talk, we present our recent work on cosmic antiproton and antideuteron signatures from primordial black holes (PBHs). Light PBHs may have formed in the early Universe and could contribute to the dark matter content of our Galaxy. Their Hawking evaporation can lead to the production of antinuclei, which propagate through the Galaxy and reach Earth as cosmic rays with fluxes peaking at GeV energies.
We revisit the expected antiproton and antideuteron signals from PBH evaporation, assuming a lognormal PBH mass distribution, state-of-the-art cosmic-ray propagation models, and an improved coalescence framework for antideuteron formation, whose most recent developments will be discussed in more detail in this talk.
Our predictions are compared with AMS-02 measurements of the antiproton flux. We find that AMS-02 data place stringent constraints on the Galactic PBH density, with bounds that depend sensitively on the parameters of the lognormal mass distribution and are comparable to, or slightly stronger than, those derived from other messengers.
Finally, we discuss the prospects for future detection of antideuterons. Given the AMS-02 antiproton limits, we predict that any future observation of cosmic antideuterons by AMS-02 or GAPS would constitute a clear signal of new physics — only part of which could, however, be explained by PBH evaporation.
Speaker: Lorenzo Stefanuto (University of Turin)
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10:30
Coffee break
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Cosmic rays, antinuclei and positrons 503/1-001 - Council ChamberConvener: Prof. Fiorenza Donato (Torino University)
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Cosmic-Ray Antimatter Particles: Latest Results from the Alpha Magnetic Spectrometer
The Alpha Magnetic Spectrometer (AMS) is a precision particle physics detector operating aboard the International Space Station. Since 2011, AMS has collected 260 billion charged cosmic rays, from elementary particles to iron nuclei with energies up to multi-TeV. The high-precision measurements with ~1% accuracy, over a solar cycle, have led to many surprising observations. The latest results on cosmic elementary particles and antiparticles (electrons, positrons, antiprotons, and protons) reveal unique properties and indicate new sources of particles and antiparticles.
The positron flux is well described by the sum of a power-law term associated with low energy positrons produced in the collision of cosmic rays, and a new source term of high energy positrons. The finite energy cutoff of the source term is established with a significance of ~5σ. These data show that high energy positrons predominantly originate either from dark matter annihilation or from a new astrophysical source. The data on antiproton exhibits an excess of antiprotons compared with secondary antiprotons produced from the collision of cosmic rays. From ~60 to ~500 GV the antiproton flux and positron flux show identical rigidity dependence, indicating a common origin of high energy antiprotons and positrons in the cosmos.Speaker: Zhili Weng (Massachusetts Inst. of Technology (US)) -
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Current Status and Future Prospects of the General Antiparticle Spectrometer (GAPS) Experiment
GAPS is an indirect search for dark matter specifically optimized for low energy cosmic antideuterons, but with excellent sensitivity for antiprotons and antiHelium. GAPS was supposed to launch in the Austral summer of 2024-2025, but unfavorable weather conditions prevented its flight. A successful launch and flight took place in December ‘25-January ‘26. I describe the evolution of the GAPS concept, the overall experiment design, and present some results from the ground calibration and data from the flight. I will also discuss prospects for a subsequent flight with upgraded capability and sensitivity.
Speaker: Charles Hailey (Columbia University) -
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Positrons and ordinary matter in cosmic raysSpeaker: Alvaro De Rujula (Universidad Autonoma de Madrid (ES))
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12:55
Lunch break
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Cosmic rays, antinuclei and positrons 503/1-001 - Council ChamberConvener: Peter von Ballmoos
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Modeling Cosmic-Ray Antiprotons and Positrons, and Comparison with AMS-02 Measurements (R)
Cosmic-ray antiprotons and positrons are expected to originate as secondaries from interactions of primary cosmic rays with interstellar gas during their propagation through the Galaxy. The AMS-02 experiment has provided high-precision measurements of these species, enabling stringent tests of cosmic-ray propagation models.
In Silver & Orlando (2024) ApJ 963, 111, we have updated and tested several standard cosmic-ray propagation scenarios using recent cosmic-ray data. For each model, we computed the resulting antiproton and positron spectra and compared them with direct measurements.
We found that the predicted secondary spectra differ significantly across models: positron spectra vary by up to an order of magnitude around ~1 GeV, while antiproton spectra vary by a factor of ~2 at several GV. We confirm the presence of an unexplained excess in the antiproton spectrum near ∼10 GeV that is not accounted for by any propagation scenario. However, in contrast to some earlier studies, we find no need for an additional model component to explain the high-energy antiproton-to-proton ratio, which follows an approximately constant rigidity dependence between ∼40 GV and ∼400 GV, consistent with AMS-02 observations. In contrast, a high-energy positron excess persists and requires an additional primary source.
Speaker: Elena Orlando -
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Imaging the positron annihilation line with 20-year INTEGRAL/SPI observations and future prospects with COSI
Observations of the 511 keV gamma-ray line from electron-positron annihilation provide a unique probe for studying cosmic antimatter distribution in our Galaxy. While the astronomical origin of Galactic positrons remains one of the long-standing mysteries in high-energy astrophysics, various theoretical scenarios have been proposed, ranging from stellar nucleosynthesis and supernovae to exotic sources such as dark matter annihilation.
In this talk, I present the latest results from analyzing 20 years of INTEGRAL/SPI data, representing the most sensitive all-sky survey of 511 keV emission to date. Using GPU acceleration and sparse matrix techniques to efficiently process about 140,000 observations with SPI's coded-mask aperture, we have created an updated all-sky map of the 511 keV gamma-ray line emission.
The reconstructed image successfully recovers established morphological features including the bright central component, extended bulge emission, and disk component along the Galactic plane. More importantly, we also report hints of new spatial features in the reconstructed image, including an asymmetric structure in the broad bulge emission and 511 keV emission potentially associated with massive stars from the Scorpius–Centaurus and other OB associations. It could provide new insights into the origin of Galactic positrons and the propagation of low-energy positrons in the interstellar medium, and should be validated with more sensitive observations.
The upcoming COSI mission as a NASA SMEX mission will improve MeV gamma-ray line observations with an order of magnitude better sensitivity, allowing us to solve the Galactic positron puzzle with its unprecedented capability. To prepare for this next-generation observation to be started from 2027, we have developed a data analysis framework for COSI, including a new algorithm for image analysis based on a Bayesian approach. In this talk, I will also present COSI's 511 keV imaging capabilities based on 3-month observation simulations.Speaker: Hiroki Yoneda
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Speaker: Luigi TIBALDO (IRAP, Université de Toulouse)
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Visit antimatter factory 1
Max 36 people. Meeting point: 15:50 at the council chamber. Guides: Eric Hunter, Jonathan Morgner, April Mathad
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Visit antimatter factory 2
Max 36 people. Meeting point: 16:50 at the council chamber. Guides: Barbara Latacz, Jonathan Morgner, ...
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