Studies of hadron spectroscopy and nuclear matter at LHCb

by Dr Yanxi Zhang (LAL)

Tuesday 26 Jun 2018, 10:00 → 11:00 Asia/Shanghai

B326 (IHEP)

While quantum chromodynamics (QCD) is well understood at high energy in the perturbative regime, low-energy phenomena, such as the binding of quarks and gluons within hadrons, are more difficult to predict. High precision measurements are then of paramount importance to test the reliability of theoretical models and computational techniques, such as potential models or lattice-QCD calculations, in predicting the mass spectrum and the properties of hadrons. Owing to its excellent capabilities with particle identification, track and vertex reconstruction, LHCb is in a unique position to make significant contributions to the sector of particle spectroscopy. The discoveries of pentaquark states and the doubly charm baryon at LHCb are presented in this seminar. Quark-Gluon Plasma (QGP) is a matter made up of defined quarks and gluons at high temperature (T>150 MeV). As a statistical assembly, the colour degree of freedom is excited in QGP compared to a system of hadrons. As a result, a phase transition could happen between QGP and hadron gas. QGP is expected to be produced in heavy nucleus collisions and would strongly modify particle productions. Signature of QGP formation in heavy ion collisions is uniquely probed by heavy flavour production. Cold nuclear effects also play a role in particle production, which need to be disentangled from the hot QGP effect. In this seminar, LHCb recent studies of nuclear effects are briefly discussed. About the speaker: Dr. Yanxi Zhang received his PhD degree in particle physics in 2013 from Tsinghua University in Beijing. He is now a postdoc researcher of Linear Accelerator Laboratory (LAL) in Orsay France since 2015, and will work at CERN as a senior research fellow in 2018. Dr. Zhang joined the LHCb collaboration when the LHC started to take data; the major topics he is involved include heavy flavor production and spectroscopy of both conventional and exotic hadrons, and studies of nuclear matter in heavy ion collisions. He made the first measurements of charmonium polarisation at LHCb, and participated in the observations of $J/psi p$ pentaquark states and the doubly charmed baryon $\Xi_{cc}^{++}$. He measured the production of heavy flavour hadrons in proton-lead collisions to study cold nuclear matter effects. He is now served as the convener of the "b-hadron and quarkonia" working group in LHCb coordinating activities to measure of production and decays of $b$ hadrons and quarkonia, and studies of hadron spectroscopy.

Slides SeminarIHEP.pdf