Dense and Strange Hadronic Matter group


Measurement of anti-3He nuclei absorption in matter and impact on their propagation in the Galaxy

Nature Physics, 2022

In our Galaxy, light antinuclei composed of antiprotons and antineutrons can be produced through high-energy cosmic-ray collisions with the interstellar medium or could also originate from the annihilation of dark-matter particles that have not yet been discovered. On Earth, the only way to produce and study antinuclei with high precision is to create them at high-energy particle accelerators. Although the properties of elementary antiparticles have been studied in detail, the knowledge of the interaction of light antinuclei with matter is limited. We determine the disappearance probability of anti-3He when it encounters matter particles and annihilates or disintegrates within the ALICE detector at the Large Hadron Collider. We extract the inelastic interaction cross section, which is then used as an input to the calculations of the transparency of our Galaxy to the propagation of anti-3He stemming from dark-matter annihilation and cosmic-ray interactions within the interstellar medium. For a specific dark-matter profile, we estimate a transparency of about 50%, whereas it varies with increasing anti-3He momentum from 25% to 90% for cosmic-ray sources. The results indicate that anti-3He nuclei can travel long distances in the Galaxy, and can be used to study cosmic-ray interactions and dark-matter annihilation.

See also:

ALICE estimate how transparent the Milky way is to antimatte (CERN news)

Antihelium nuclei as messengers from the depths of the galaxy (TUM news)

Our Solidarity with the Protests in Iran

We decided within our research group to show support to the people, especially women, in Iran and to our Iranian colleagues here at TUM by producing and wearing in our everyday life a pin with the face of Mahsa on it.

We currently wear it on our backpacks, jackets and clothes so that everyday we can help as human beings and scientists, even with a small gesture, spreading awareness on the life conditions in Iran under the dictatorship of the Islamic Republic.

Unveiling the strong interaction among hadrons at the LHC

Nature volume 588, pages 232–238 (2020)

One of the key challenges for nuclear physics today is to understand from first principles the effective interaction between hadrons with different quark content. First successes have been achieved using techniques that solve the dynamics of quarks and gluons on discrete space-time lattices. Experimentally, the dynamics of the strong interaction have been studied by scattering hadrons off each other. Such scattering experiments are difficult or impossible for unstable hadrons and so high-quality measurements exist only for hadrons containing up and down quarks. Here we demonstrate that measuring correlations in the momentum space between hadron pairs produced in ultrarelativistic proton–proton collisions at the CERN Large Hadron Collider (LHC) provides a precise method with which to obtain the missing information on the interaction dynamics between any pair of unstable hadrons. Specifically, we discuss the case of the interaction of baryons containing strange quarks (hyperons). We demonstrate how, using precision measurements of proton–omega baryon correlations, the effect of the strong interaction for this hadron–hadron pair can be studied with precision similar to, and compared with, predictions from lattice calculations. The large number of hyperons identified in proton–proton collisions at the LHC, together with accurate modelling of the small (approximately one femtometre) inter-particle distance and exact predictions for the correlation functions, enables a detailed determination of the short-range part of the nucleon-hyperon interaction.