de | en

Dr. rer. nat. Ivan Vorobyev

Photo von Dr. rer. nat. Ivan Vorobyev.
Phone
+49 89 289-12563
Room
E-Mail
ivan.vorobyev@tum.de
Links
Page in TUMonline
Group
Dense and Strange Hadronic Matter

Offered Bachelor’s or Master’s Theses Topics

Absorption of antinuclei in ALICE Time Projection Chamber using machine learning algorithms
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. Multiple balloon- and space-borne experiments are searching for the traces of DM using the idea of possible annihilation or decay of DM particles into ordinary (anti)particles, including light (anti)nuclei. The latter (such as antideuterons and antihelium nuclei) are considered as especially promising probe for such indirect DM searches, as the background stemming from ordinary collisions between cosmic rays and the interstellar medium is expected to be very low with respect to the DM signal. In order to reliably estimate the fluxes of antinuclei near Earth stemming from DM and from background, it is necessary to know the probability for antinuclei to interact inelastically with ordinary matter on their way to the detectors (e.g. with interstellar medium and Earth's atmosphere). This probability is driven by the inelastic cross section of corresponding processes, which for antinuclei are still poorly (or not) known. This fact hinders precise calculations of antinuclei fluxes near Earth and forces existing estimates to rely on extrapolations and modelling. The here advertised master project will deal with the analysis of inelastic interactions of antinuclei inside the gas volume of the Time Projection Chamber of the ALICE detector. Such interactions typically create a bunch of secondary (charged) particles with low momentum with a characteristic topology of secondary vertex inside the TPC volume. The pattern can be recognised by machine learning algorithms trained on simulated events, in which such annihilation processes happen in a controlled environment. After the validation of algorithms with simulated events, one can analyse real experimental data and tag the annihilation events of interest, which in turn can be used to evaluate the effective antinuclei + A inelastic cross section. This project will be structured in the following way: - simulation of the inelastic interactions of antinuclei with the TPC gas using Geant4 toolkit - training and validation of neural networks to reliably recognise antinuclei annihilation events - Analysis of the ALICE experimental data from pp collisions at sqrt(s) = 13 TeV - Evaluation of the effective antinuclei + A inelastic cross sections
suitable as
  • Master’s Thesis Nuclear, Particle, and Astrophysics
Supervisor: Laura Fabbietti
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
Supervisor: Laura Fabbietti
Top of page