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Dr. rer. nat. Ivan Vorobyev

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Dense and Strange Hadronic Matter

Offered Bachelor’s or Master’s Theses Topics

Study the absorption of antihelium-4 in ALICE experiment at CERN LHC
Dark Matter (DM) is believed to account for roughly 27% of the mass-energy of our Universe, and its nature remains one of the most intriguing unsolved questions of modern physics. This massive hole in our knowledge drives multiple experimental searches for DM, and one of the indirect ways to search for DM is to look for the annihilation or decay of DM particles into ordinary (anti)particles such as light (anti)nuclei as employed by several balloon- and space-borne experiments. Low-energy light antinuclei (e.g. antihelium-4) are particularly promising signals for these indirect DM searches, since the background stemming from ordinary collisions between cosmic rays and the interstellar medium is expected to be low with respect to the DM signal. In order to reliably estimate the detection probability of interesting events such as DM -> helium-4 + antihelium-4 + ..., the interaction probability of antihelium-4 with ordinary matter (like interstellar medium, Earth's atmosphere) must be measured, since it defines the amount of antihelium-4 particles lost on the way to detector. However, nuclear inelastic cross sections of antihelium-4 + A processes are completely unknown, forcing current estimates of expected antihelium fluxes near Earth to rely on extrapolations and modelling. The topic of the here advertised master project deals with the measurement of these interactions using the ALICE detector. In heavy-ion collisions at LHC energies (anti)helium-4 nuclei are produced in significant amounts, and unique tracking and PID capabilities of the ALICE experiment make it possible to reliably detect the (anti)helium-4 nuclei in different sub-detector systems. This allows us to quantify the inelastic interaction probability of (anti)helium-4 with the ALICE detector material. This project will be structured in the following way: Analysis of the inclusive spectra of helium-4 and antihelium-4 nuclei in PbPb collisions at TeV Evaluation of the effective antihelium-4 + A inelastic cross sections Estimation of the antihelium-4 rates expected for different DM models in current and future satellite experiments
suitable as
  • Bachelor’s Thesis Physics
  • Master’s Thesis Nuclear, Particle, and Astrophysics
Supervisor: Laura Fabbietti
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