Di-hadron Correlation In Pb+Pb Collisions At (S_NN)～(1/2)=5.5TeV With ALICE

With the development of science technology and the progress of theory, the re-alization to the microstructure of materials has been increased deeply, from Wrong "atomic indivisible" to the discovery of the electron, then to Rutherford raising atom nuclear model, and after the discovery of the neutron......, All these make people come to realize:the atom consists of the nuclei and electrons,the nucleus is composed of the protons and the neutrons, while the proton and the neutron consist of the confined of quarks and gluons. A theory established on the modern physics, de-scribes the basic interactions and elementary particles participating in-the Standard Model(SM), which shows all the macroscopic materials composed of these elementary particles, namely 6 flavor quarks,6 leptons and 4 force carriers(presently). At the same time, Another aspect of the standard model, the kinetic theory describing the interaction of quarks,gluons-quantum chromodynamics (QCD), predicts that the quarks and gluons will be deconfined at a high temperature or high density of baryon environment,then form a new state of matter, quark-gluon plasma(QGP). Numerous studies have shown that the initial Big Bang may had formed the new state because of the extremely high temperature in initial explosion; or the inner of neutron star for the neutron star having a very high baryon density.To search for the quark-gluon plasma and study the properties of the new matter, scientists look forward to producing the new state of matter by high energy heavy-ion collisions experiments, then haved built the CERN/SPS, RHIC and other large exper-iments. And fruitful results about QGP have been got. CERN is currently running the Large Hadron Collider (LHC), which is Composed of four large experiments. One of them, the Large Heavy Ions Collisions Experiments (ALICE), whose design and performance will provide unprecedented advantage to study the heavy ions collisions. In the lead-lead collision,the energy of per-Pb nucleon is accelerated to 2.75TeV, and then is carried out the collision. It is expected to form a more significant local extremely high temperature and density of nuclear matter to produce the new mat-ter of quark-gluon plasma(QGP). Because the formation of the QGP only instantly exists after the collision, so it is impossible to observe this new matter directly, and only judge the formation of QGP from a variety of final information or not,then to study various properties of QGP. So far, the signals of formation QGP in heavy ions collisions are follows:strangeness enhancement, J/Ψsuppression, directed photons and thermal di-lepton, jet quenching, collective flow etc. Much results of hadrons correlations show the production of jet quenching, such as the final state inclusive hadron spectra distribution and the nuclear modification factor showing strong sup-pression in the high transverse momentum, di-hadron azimuth correlation away-side peak suppression and so on.ALICE Off-line analysis is an important part of the ALICE experiments, which is based on the Root and AliRoot framework to carry out the collision data gen-erated in simulation,reconstruction of the ALICE detector and data analysis with the phenomenology generator in high-energy collisions. As a member of the AL-ICE experimental group,Ⅰhave worked on the data generated of LHC energy re-gion,reconstruction and analysis under the ALICE Off-line framework in the past three years. This work is in the framework to use phenomenological models Q-PYTHIA and PYTHIA to produce (?)= 200GeVAu-Au collisions,p-p collisions and(?)= 5.5TeVPb-Pb collisions,p-p collisions,then to pre-research the physi-cal results of Pb-Pb collisions in coming in di-hadron correlation method. Firstly, by analyzing the nuclear modification factor of(?)= 200GeVAu-Au collisions,p-p collisions, compared with nuclear modification factor in RHIC, discovery that it also has a suppression factor of order 5 at pT> 6GeV/c; Secondly, analyse the di-hadron correlation distribution of(?)= 5.5TeV Pb-Pb collisions and p-p collisions the results of di-hadron azimuth correlation in Q-PYTHIA is observed broadening at the two peaks compared with PYTHIA at low transverse momentum region, but do not show "di-hump" and "ridge" phenomena, which may be affected by the model restrictions.There is obvious suppression in the peak of away-side at high transverse momentum region. In addition, we also analyze the medium modification of near-side and away-side(Jaa)and the hadron-triggered fragmentation function(D((?)T))。...