Přehled

Faculty of mathematics and physics of the Charles university (Prague, Czechia) is accepting applications in PhD study programmes (to start studying in October 2024). Details on the requirements and the procedure can be found in the faculty admissions page [link] (deadline for applications is April 30). Practical info on living in Prague can be found [here].

The COMPASS (CERN-NA-58) experiment group at the faculty [our web] is offering a topic of the future PhD thesis and a supplementary scholarship to one applicant in the study programme of particle and nuclear physics. As explained in the faculty admission page, having an approved PhD topic helps in the entrance examination. The scholarship (in the form of a part-time job contract) would add to the default one given by the faculty to provide in total at least 30.000 CZK (about 1.200 EUR) per month and can be guaranteed for 2 years. The topic is described below.

Notes:

• The study may be conducted in cooperation with University of Trieste in the framework of a ‚jointly-supervised thesis‘ agreement.
• We also offer a PhD topic at AMBER experiment [link].
• It may be possible (and preferable) to start the contract earlier (e.g. August), if the visa situation of the applicant allows.

Required qualification:

• Knowledge of particle (sub-nuclear) physics on Master degree level. Background in hadron physics (parton model etc.) would be appreciated.
• Experience with data analysis and computer programming, in the optimal case with ROOT (in C++ or Python) in particular.
• English for professional communication and scientific writing.

To apply for the thesis topic, please send your brief CV and motivation letter to Jan Matousek [email] and arrange for a letter of recommendation to be sent by a relevant referee as well.

Production of pions, kaons and protons identified by a RICH detector in DIS at COMPASS experiment

The structure of hadrons is encoded in the equations of QCD. However, fifty years after the discovery of quarks the theoretical calculations are just beginning to realistically describe their arrangement in hadrons. The COMPASS collaboration collected data on semi-inclusive deep-inelastic scattering of muons off hydrogen and off transversely polarised protons and deuterons. Hadrons produced in this process carry the information on the intrinsic transverse momentum and on the polarisation of quarks of different flavours – a 3D mapping of the nucleon in the momentum space.

In the context of high-energy particle collisions the hadron structure is described by transverse momentum dependent parton distribution functions (TMD PDFs). They are functions of the longitudinal momentum fraction x carried by a particular parton and of the intrinsic transverse momentum k_T squared of the parton. They encode all possible correlations between the nucleon spin,the parton spin and k_T. While the x-dependence is rather well known, accessing the distribution of k_T is difficult, as it is not observable directly. Measuring transverse momentum P_T of hadrons produced in DIS, one accesses a convolution of the k_T of the struck quark and of the transverse momentum obtained in hadronisation. To disentangle the effects, one can use transverse-momentum-dependent multiplicities of hadrons produced in e+e− annihilation, which were recently published [Belle, Phys.Rev.D99 (2019) 112006]. Another way to access the intrinsic k_T is via the Cahn effect – a modulation in the azimuthal angle phi_h of hadrons produced in DIS. However, the available COMPASS [COMPASS, Nucl.Phys.B886, 2014] and HERMES results point to much smaller values of k_T than those coming from the measurements of P_T [Barone et al., Phys.Rev.D91 (2015) 074019].

To understand the complicated picture, it is desirable to carry out a fully multi-dimensional measurement for identified hadron species (pi, K, p). One can also study the possibility to measure neutral pions and kaons and vector mesons such as rho. The large data sample collected by COMPASS in 2016–2017 on liquid hydrogen target allows such a measurement. The data collected in 2022 on polarised deuterium give in addition access to spin-dependent TMD PDFs, such as the polarisation of quarks in a transversely polarised nucleon (so-called transversity PDF) and the correlation between quark transverse momentum and nucleon transverse polarisation (Sivers TMD PDF).