YOUNGST@RS - Feebly Interacting Sectors Impact on Cosmology & Astrophysics

1 Mar 2022, 15:50 → 4 Mar 2022, 19:30 Europe/Berlin

Mainz Institute for Theoretical Physics, Johannes Gutenberg University

Overview:

Different types of astrophysical environments—such as horizontal branch stars, the sun, supernovae (SNe), neutron stars, black holes—offer different guises to explore fundamental physics, and in particular feebly interacting sectors.

A collaborative effort between particle physicists, astrophysicists and astronomers is highly desirable. This interaction can help refine existing ideas, identify the most promising candidate theories and come up with new possible signatures from astrophysical objects.

The goal of this workshop is to bring together the relevant communities, paving the way for a new decade in fundamental physics.

Dates and time:

• March 1-4
• Daily at 4:00 PM CET (7:00 AM US PST, 9:00 AM US EST)

Venue:

• Online ZOOM (virtual)
• Connection information will be sent to participants

Confirmed speakers:

• Asimina Arvanitaki (Perimeter Inst. Theor. Phys.)

• Francesca Calore (Annecy, LAPTH)

• Djuna Croon (Durham U.)

• Igor G. Irastorza (U. Zaragoza)

• Joachim Kopp (CERN and U. Mainz)

• Rebecca Leane (SLAC)

• Sasha Philippov (CCA, Flatiron Institute)

• Georg Raffelt (MPI for Physics)

• Benjamin R. Safdi (LBNL and UC Berkeley)

• Oscar Straniero (INAF-Osservatorio Astronomico d'Abruzzo)

• Irene Tamborra (NBI, U. Copenhagen)

• Ken Van Tilburg (NYU and CCA, Flatiron Institute)

Executive_Summary_FISICA2022.pdf

Tuesday 1 March

Welcome Greeting by MITP Directors

Stars and Supernovae

1 Stars as Particle-Physics Laboratories: Old Ideas and New Developments

The hot and dense interiors of stars are powerful factories for
low-mass particles such as neutrinos or the hypothetical axions and axion-like particles, dark photons, fuzzy-dark-matter-particles, and others. The back-reaction on stars or searching for the particle fluxes or decay products provides some of the most restrictive limits, but also future detection opportunities. While many of these arguments go back to the beginnings of neutrino physics and axion ideas, there have been intriguing new developments and opportunities that will be reviewed.

Speaker: Georg Raffelt

Fisica_Raffelt.pdf

Fisica_Raffelt.pptx

Raffelt Youtube

2 Supernova Lessons from the Weakly Interacting Universe

Neutrinos are key particles in the core collapse of massive stars, crucially affecting the supernova inner workings. In addition, non-standard feebly interacting particles may be abundantly produced in the hot and dense supernova core, making the latter a unique laboratory to explore physic beyond the Standard Model. Fascinating recent developments on the physics of neutrinos and other weakly interacting particles in core-collapse supernovae will be reviewed.

Speaker: Irene Tamborra

3 Axion-Electron coupling from the RGB tip after the GAIA early-data-release 3

Globular Clusters (GC) are building blocks of any kind of galaxy. The Milky Way hosts hundreds of GCs, preferentially located in the galactic halo and bulge. A typical GC contains about 10^6 almost coeval stars, as old as \sim 13 Gyr. In the more advanced phase of the evolution, i.e., stars found in the RGB, HB, AGB and WD cooling sequence, stellar interiors are hot enough for the activation of thermal processes capable to produce hypothetical feebly interacting particles, such as Axions or Axion-Like-Particles (ALPs). Then, if the mass of these particles is smaller than \sim 100 KeV, they freely escape from the stellar core, thus acting as a net energy sink, whose effects are expected to modify the observed macroscopic stellar properties, such as the luminosity or the number of stars found in a given evolutionary phase. Therefore, precise measurements of these stellar properties my constrain the unknown properties of these particles, such as the strengths of the interactions with standard model particles (photons, electrons….) or their mass. In this talk, I will discuss the constraint of the axion-electron coupling as obtained from the observed luminosity of the RGB tip. I will show how the recent availability of more accurate astrometric data from GAIA (EDR3) and HST, coupled to the development of more reliable stellar models, provide the most stringent and robust upper bound to g_ae.

Speaker: Oscar Straniero

18:00 Coffee Break

Stars and Supernovae

4 Constraining pseudo-Dirac neutrinos from a future galactic supernova

Ever since the discovery of neutrinos, we have wondered if neutrinos are their own antiparticles. One remarkable possibility is that neutrinos have a pseudo-Dirac nature, predicting a tiny mass difference between active and sterile states, with oscillations driven by this tiny mass difference. Such oscillations can only be visible over very long distances. In this talk, I will discuss how analyzing the neutrino data from SN1987A in the light of active-sterile oscillations can present a mild preference for such oscillations. Notably, the same data is able to exclude some of the tiniest mass differences for neutrinos constrained so far. I will further discuss the prospects of next-generation experiments aimed at detecting supernova neutrinos to the nature of the neutrino mass.

Speaker: Manibrata Sen

FISICA22_Sen.pdf

5 Indication of a Pulsar Wind Nebula in SN 1987A

Since the day of its explosion, SN 1987A was closely monitored with the aim to study its evolution and to detect its central compact relic. The detection of neutrinos from the supernova strongly supports the formation of a neutron star (NS). However, the constant and fruitless search for this object has led to different hypotheses on its nature. To date, the detection in the Atacama Large Millimeter/submillimeter Array data of a feature that is somehow compatible with the emission arising from a proto-pulsar wind nebula (PWN) is the only hint of the existence of such elusive compact object. In this talk, I will discuss how we tackled this 33 yr old issue by analyzing archived observations of SN87A performed by Chandra and NuSTAR in different years. We firmly detect nonthermal emission in the 10-20 kev energy band, due to synchrotron radiation. The possible physical mechanism powering such emission is twofold: diffusive shock acceleration (DSA) or emission arising from an absorbed PWN. By relating a state-of-the-art magnetohydrodynamic simulation of SN87A to the actual data, we reconstruct the absorption pattern of the PWN embedded in the remnant and surrounded by cold ejecta. We found that the most likely scenario that well explains the data is that of PWN emission. Finally, I will also present some follow-up results corroborating the PWN scenario.

Speaker: Emanuele Greco

6 Towards probing the diffuse supernova neutrino background in all flavors

To fully understand the whole core-collapse supernova population, it is essential to observe neutrinos from multiple supernovae events - the diffuse supernova neutrino background (DSNB). The Super-Kamiokande (SK) detector achieved the most stringent upper limit on the electron antineutrino component of the DSNB. This limit is only a factor of 2-3 above most of the theoretical predictions. In addition, SK is now enriched with gadolinium which will help to reduce backgrounds for the DSNB search and most probably lead to the detection within the near future. The electron neutrino component of the DSNB has a ten times weaker upper limit than the electron antineutrino component. The limit may change into observation with the upcoming Deep Underground Neutrino Experiment (DUNE). But capturing the complete picture of the core-collapse supernova landscape and investigating new astrophysics or physics requires probing DSNB in all flavors. The upper limits on the non-electron component of the DSNB (muon and tau neutrinos and antineutrinos) are ~ a thousand times weaker than the theoretical predictions. In this talk, I will present how the large-scale direct dark matter detectors can help significantly tighten the upper limits on the non-electron component of DSNB. In addition, I will talk about plausible beyond the Standard Model scenarios, which could alter the non-electron neutrino emission from the core-collapse supernovae.

Speaker: Anna Suliga

Suliga_Mainz.pdf

Wednesday 2 March

X-ray and radio observations

7 Probing axion-like and other feebly interacting particles from core collapse SNe with high-energy astrophysics

Axion-like particles (ALPs) and other feebly interacting particles (FIPs) can be efficiently produced in core collapse SNe and escape the SNe envelope.
During propagation in the interstellar medium and interaction with the environment, depending on their couplings, they may leave trace of their presence in cosmic backgrounds of high-energy radiation, from X to gamma rays, as well as specific signatures such as a 511 keV line signal.
I will illustrate how high-energy astrophysics observations can be exploited to look for specific imprints of ALPs and other FIPs over a broad range of wavelengths.

Speaker: Francesca Calore

Youngstars_FCalore.pdf

8 Pulsar magnetospheres and their radiation

In this talk I will review the state-of-the-art understanding of pulsar magnetospheres and their radiation using first-principles kinetic simulations. I will focus on physics of pair production discharges near the star, magnetic reconnection close to the light cylinder, and their role in producing observed coherent radio and gamma-ray radiation.

Speaker: Alexander Philippov

9 The QCD Axion Mass

Speaker: Malte Buschmann

18:00 Coffee Break

X-ray and radio observations

10 Radio lines from axion dark matter: on the forward modeling

Axion dark matter may undergo efficient conversion to photons deep in the magnetospheres of neutron stars, generating narrow spectral features observable with radio telescopes. In this talk I will discuss the current state-of-the-art in the forward modeling of these systems, which rely on the use of geometric ray tracing algorithms to compute the anisotropy, spectral properties, and magnitude of the radio signal. By combining these algorithms with our knowledge of the evolution and distribution of neutron stars in our galaxy, we have developed a novel and powerful technique to indirectly detect axion dark matter. Results from the latest search using observations of the Galactic Center taken by the Green Bank Telescope will be presented in the following talk (given by Josh Foster).

Speaker: Samuel Witte

axions_magneto.pdf

11 Axion Dark Matter Searches with Breakthrough Listen SETI Dat

The efficient conversion of axion to radio-band photons in neutron star magnetospheres provides a tantalizing opportunity to search for micro-eV axion dark matter through indirect means with existing and upcoming telescopes. We search for evidence of this conversion process using archival Green Bank Telescope data collected in a survey of the Galactic Center in the C-Band by the Breakthrough Listen project. While Breakthrough Listen aims to find signatures of extraterrestrial life in the radio band, their high-frequency resolution spectral data of the Galactic Center region is ideal for searching for the quasi-monochromatic radio spectral lines of axion conversion. Using state-of-the-art ray-tracing simulations and data-driven models of the neutron star population in the inner pc of the galaxy, we make use of 280 minutes of observations of the inner GC to search for axion DM, finding no evidence for a signal and setting leading constraints on the axion-photon coupling for masses between 15 and 35 micro-eV.

Speaker: Joshua Foster

Thursday 3 March

Direct detection and superradiance

12 Experimental searches for axions

Proposed more than 40 years ago, axions are still the most compelling solution to the strong CP problem of the Standard Model. More recently their physics case has been considerably sharpened, as well as that of similar axion-like particles (ALPs) that generically emerge in diverse high-energy extensions of the Standard Model, notably string theory. Both axion and ALPs constitute very appealing candidates to the dark matter of the Universe, and they are also invoked as a solution of a number of anomalous astrophysical observations. In addition, particular realizations of these type of models appear linked with inflation, dark radiation and even dark energy. These developments, together with the fact that experimental techniques have recently achieved sensitivity to relevant regions of ALP parameter space, are increasing the interest in the search for these particles. I will review the status of the experimental landscape, as well as near term prospect from ongoing experiments, future projects and new detection ideas in the search for laboratory, dark matter and solar axions and ALPs.

Speaker: Igor Irastorza

13 Stellar Basins

I will describe the phenomenology of stellar basins: volumetric stellar emission into gravitationally bound orbits of weakly coupled particles such as axions, moduli, hidden photons, and fermions. While only a tiny fraction of the instantaneous luminosity of a star (the vast majority of the emission is into relativistic modes), the continual injection of these particles into a small part of phase space causes them to accumulate over astrophysically long time scales, forming a "stellar basin", in analogy with the geologic kind. The energy density of the Solar basin can surpass that of the relativistic Solar flux at Earth's location after only a million years, for a sufficiently long-lived particle produced through an emission process whose matrix elements are unsuppressed at low momentum. I will discuss ongoing N-body simulations of the Solar basin, and preliminary results on recasted direct detection searches for basin particles around the Sun.

Speaker: Ken Van Tilburg

14 The piezoaxionic effect

Axion dark matter (DM) constitutes an oscillating background that violates parity and time-reversal symmtries. Inside piezoelectric crystals, where parity is broken spontaneously, this axion background can result in a stress. We call this new phenomenon "the piezoaxionic effect". When the frequency of axion DM matches the natural frequency of a bulk acoustic normal mode of the piezoelectric crystal, the piezoaxionic effect is resonantly enhanced and can be read out electrically via the piezoelectric effect. We explore all axion couplings that can give rise to the piezoaxionic effect -- the most promising one is the defining coupling of the QCD axion, through the anomaly of the strong sector. We also point our another, subdominant phenomenon present in all dielectrics, namely the "electroaxionic effect". An axion background can produce an electric displacement field in a crystal which in turn will give rise to a voltage across the crystal. The electroaxionic effect is again largest for the axion coupling to gluons. We find that this model independent coupling of the QCD axion may be probed through the combination of the piezoaxionic and electroaxionic effects in piezoelectric crystals with aligned nuclear spins, with near-future experimental setups applicable for axion masses between 10−11eV and 10−7eV, a challenging range for most other detection concepts.

Speaker: Asimina Arvanitaki

18:00 Coffee Break

Direct detection and superradiance

15 ALPHA: Towards a Plasma Haloscope

Plasma haloscopes are a novel method for the detection of the resonant conversion of axions to photons. Matching a tunable plasma frequency to the axion mass, allows for resonant conversion even if translation invariance is unbroken. Using a wire metamaterial one can create an artificial plasma, which is tuneable changing the interwire spacing, allowing for large conversion volumes. This talk will give an overview of the plasma haloscope concept and the ongoing efforts of the ALPHA consortium.

Speaker: Alexander Millar

16 Lumped element detection for low-mass axions: ABRACADABRA and DMRadio

Axions with low masses (less than ~1 \mu eV) have wavelengths that are too large to fit inside a reasonably-sized experiment. In this regime, axion-photon interactions in a strong magnetic field produce an effective current that is in phase across an entire detector. This effective current can be inductively coupled to a circuit and read out using high-sensitivity amplifiers. ABRACADABRA-10 cm gave the first demonstration of this technique, setting world-leading limits on axion dark matter with masses 0.3-8.3 neV. This program is continuing with DMRadio, a set of lumped element experiments currently being designed with the goal of searching for ALP and QCD axion dark matter over a wide range of masses below 1 \mu eV.

Speaker: Chiara Salemi

17 Hunting for axions in the solar basin

A large flux of axion-like particles can be produced in the solar core. While the majority of these particles will have high velocities and escape the Sun’s gravitational pull, a small fraction of low-velocity particles will become trapped on bound orbits. Over time, an appreciable density of slow-moving axions can accumulate in this “solar basin.” Their subsequent decay to two photons provides a distinct observational signature. I will present an ongoing analysis using the NuSTAR X-ray telescope to search for the decay products of keV-scale axions trapped in the solar basin.

Speaker: Will De Rocco

Friday 4 March

Dark matter interactions in Astrophysics

18 Black hole archeology with gravitational waves

The growing gravitational wave dataset makes black hole population studies possible. In this talk I will demonstrate how such studies can be used to study particle and nuclear physics. The key insight is that a wide range of initial stellar masses leave no compact remnant, due to the physics of pair-instability; the unpopulated space in the stellar graveyard is known as the black hole mass gap (BHMG). New physics can dramatically alter the late stages of stellar evolution and shift the BHMG, when it acts as an additional source of energy (loss) or modifies the equation of state. The latter will be the focus of this talk, in which I will show some new results with axions in the so-called cosmic triangle. I will also demonstrate how these predictions can be tested with the gravitational wave observations by the LIGO/Virgo/Kagra collaboration, and what we can already infer from GWTC-2 and 3.

Speaker: Djuna Croon

19 Dark Matter, Destroyer of Worlds: Dark Matter-Induced Black Hole Formation in Stars and Planets

Dark Matter can be captured by celestial objects and accumulate at their centers. If the density is high enough, these dark matter cores can collapse into small black holes. If the nascent black hole is large enough, it will eventually consume its host. If it is smaller, it will evaporate via Hawing radiation, which his potentially observable as an anomalous heat flux or an anomalous neutrino flux. We show how such arguments can be used to constrain dark matter, in particular super-heavy dark matter particles.

Speaker: Joachim Kopp

20 Gamma-Ray Searches for Dark Matter in Celestial Bodies

Stars and planets can be ideal playgrounds to discover dark matter. In this talk, I will discuss a range of new searches for dark matter using gamma rays emitted from celestial objects, including solar system objects, such as the Sun and Jupiter, as well as Galactic populations of brown dwarfs and neutron stars.

Speaker: Rebecca Leane

18:00 Coffee Break

Dark matter interactions in Astrophysics

21 New manifestations of primordial black holes

Speaker: Volodymyr Takhistov

22 Simulation of energy transport by dark matter scattering in stars

Asymmetric dark matter (ADM) that is captured in stars can an act as an efficient conductor of heat, generating observable modifications to neutrino fluxes and astroseismological observables. The two formalisms commonly used to parametrise this phenomenon were developed over 30 years ago, and calibrated on single set of simulations. In this talk, I will present the results of new state-of-the-art Monte Carlo simulations of ADM mediated energy transport, including the first ever numerical exploration of interaction cross sections with velocity and momentum dependence. Based on simulation results, updated recommendations on the parametrisation of DM heat transport for inclusion in stellar evolution models will be given.

Speaker: Hannah Banks