Optimization of the reconstruction of B0 -> D*+ pi- and D*+ -> D0 pi+ decays with the ALICE detector

Abstract

Quantum Chromodynamics (QCD) predicts that if quarks and gluons are at very high temperatures and/or densities they become asymptotically free and form what is called a quark gluon plasma (QGP). The ALICE detector at the Large Hadron Collider (LHC) is used to study matter at conditions hot and dense enough to produce a QGP. To study the properties of the QGP, we look at mesons which traverse the QGP containing the heavy quarks charm and beauty. This is done by colliding two ionized lead atoms. The same mesons are produced and measured in proton-proton collisions. The difference in their properties, after normalization, tells us more about the properties of the QGP.

In addition to a statistical error, conclusions drawn from data from ALICE have systematic errors. By varying the methods used in the yield extraction of D*+ mesons in lead-lead collisions at 30-50% centrality we found that the systematic uncertainties of the yield extraction are in general below 10%.

In 2015 the LHC will be upgraded to collide lead ions at 5.1 instead of 2.76 TeV and to collide protons at 13 instead of 7 TeV. To prepare for the planned beauty measurements we performed Monte Carlo simulations of proton-proton collisions at 13 TeV. We are interested in the decay chain: b -> B0 -> D*+ pi- -> D0 pi- pi+ -> K- 2pi+ pi-. In these simulations we will focus on the decay B0 -> D*+ pi-. The event generator PYTHIA is used to perform the simulations. We mainly look at what cuts could be applied and estimate how many particles ALICE will be able to detect in 2015. Among other results we found that at low transverse momenta (pt) almost twice as many B0 -> D*+ pi- decays as B0 -> D*+ and other decays occur. At high pt values there are up to 2.5 times as many B0 -> D*+ and other decays as B0 -> D*+ pi- decays. In the B0 -> D*+ pi- decay 20-30% more pions than D*+ mesons are in the acceptance region of the ALICE detector. In general particles with higher velocities are more likely to be in acceptance of the ALICE detector.