Measuring The Bottom Quark Tagged Jets In Pp Collisions At (?)=5.02 TeV With ALICE

The current standard model of particle physics believes that quarks and gluons are elementary particles,and their dynamics are described by Quantum Chromodynamics(QCD).According to the QCD Theory,due to the color confinement at long distances or at low energy,quarks are always confined in hadrons and cannot exist in isolation,so it is impossible to observe free quarks and gluons in general circumstances.Under extreme conditions of high temperature and high density,the interaction between quarks and gluons is weakened,and the deconfinement occurs.Modern cosmology believes that QGP is the state of the universe a few microseconds after the Big Bang,and may still exist in the core of the neutron stars.In the LHC heavy ion experiments,two beams of lead ions moving close to the speed of light are collided,reaching a very high energy density in a limited volume,thereby producing QGP.In high-energy heavy-ion collision experiments,jets and heavy quarks(bottom quarks,charm quarks)are two important probes for the study of QGP.The jet is a beam of collimated final-state particles formed by the high-energy partons produced by the hard scattering.When the jet traverses the QGP medium,its high-energy partons interact with the hot and dense medium to cause energy loss.The experimental observation results show the suppression of the transverse momentum spectra.This effect is called jet quenching.Heavy quarks are usually considered to be produced in the early hard scattering process of collision,so heavy quarks can go through the entire process of medium evolution.And according to the perturbation QCD theory,the hard-scattering process can be calculated by the theoretical model and their dependence can be studied by measuring the production of heavy quark jets in proton-proton collisions,proton-lead collisions,and lead-lead collisions.The heavy-flavor jet is one of the current research hotspots in heavy ion collisions.Based on the 5.02TeV proton-proton collision data obtained by the ALICE detector in 2017,the inclusive bottom-jet tagging measurement was performed through Tracking Counting and Secondary Vertex algorithms.The bottom quark jet yield was corrected through procedures of background subtraction,tagging efficiency and purity estimation,as well as detector effect subtraction.And the b-jet production cross section was calculated based on the corrected yield.At the same time,the measurement results are compared with the calculations of the Next to Leading Order(NLO)pQCD model to give a preliminary verification of the theoretical model.