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Register a new userScale dependence of heavy quark production in pp and $bar{mathbf{p}}$p collisions - transverse momentum dependence
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The dependence of the differential cross section ${mathrm{d}sigma}/{mathrm{d}p_{perp}}$ of inclusive heavy quark production in pp and $bar{mathrm{p}}$p collisions on the renormalization and factorization scales is investigated. The implications of our results for experiments at TEVATRON and LHC are discussed. In particular, it is shown that the NLO QCD predictions for $bar{t}t$ production at the LHC based on the Principle of Minimal Sensitivity are by 30-50% higher than the standard ones.
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We discuss and compare different approaches to include gluon transverse momenta for heavy quark-antiquark pair production. The correlations in azimuthal angle and in heavy quark, heavy antiquark transverse momenta are studied in detail. The results are illustrated with the help of different unintegrated gluon distribution functons (UGDF) from the literature. We compare results obtained with on-shell and off-shell matrix elements and kinematics and quantify where these effects are negligible and where they are essential. We concentrate on the region of asymmetric transverse momenta of charm quark and charm antiquark. Most of UGDFs lead in this corner of the phase space to almost full decorellation in azimuthal angle. We propose correlation observables to be best suited in order to test the existing models of UGDFs.
We study the impact parameter dependence of inelasticity in the framework of an updated geometrical model for multiplicity distribution. A formula in which the inelasticity is related to the eikonal is obtained. This framework permits a calculation of the multiplicity distributions as well as the inelasticity once the eikonal function is given. Adopting a QCD inspired parametrization for the eikonal, in which the gluon-gluon contribution dominates at high energy and determines the asymptotic behavior of the cross sections, we find that the inelasticity decreases as collision energy is increased. Our results predict the KNO scaling violation observed at LHC energies by CMS Collaboration.
The calculation of inclusive spectra of pions produced in $pp$ and $AA$ collisions as a function of rapidity $y$ is presented within the self-similarity approach. It is shown that at not large rapidities $y$ one can obtain the analytical form of the self-similarity function $Pi(y,p_t)$ dependent of $y$ and hadron transverse momentum $p_t$. A satisfactory description of data on the rapidity spectra at $|y|leq$ 0.3 is illustrated within a good agreement. The universal energy dependence of these spectra is also shown.
Cross sections for semi-inclusive electroproduction of charged pions ($pi^{pm}$) from both proton and deuteron targets were measured for $0.2<x<0.5$, $2<Q^2<4$ GeV$^2$, $0.3<z<1$, and $P_t^2<0.2$ GeV$^2$. For $P_t<0.1$ GeV, we find the azimuthal dependence to be small, as expected theoretically. For both $pi^+$ and $pi^-$, the $P_t$ dependence from the deuteron is found to be slightly weaker than from the proton. In the context of a simple model, this implies that the initial transverse momenta width of $d$ quarks is larger than for $u$ quarks and, contrary to expectations, the transverse momentum width of the favored fragmentation function is larger than the unfavored one.
In the present work, we study the recent collision energy and multiplicity dependence of the charged particle transverse momentum spectra as measured by the ALICE collaboration in $pp$ collisions at $sqrt{s}$ = 5.02 and 13 TeV using the non-extensive Tsallis distribution and the Boltzmann-Gibbs Blast Wave (BGBW) model. A thermodynamically consistent form of the Tsallis distribution is used to extract the kinetic freeze-out parameters from the transverse momentum spectra of charged particles at mid-rapidity. In addition, a comprehensive study of fitting range dependence of transverse momentum spectra on the freeze-out parameters is done using Tsallis statistics. The applicability of BGBW model is verified by fitting the transverse momentum spectra of the bulk part ($sim 2.5~ {rm GeV}/c$)for both 5.02 and 13 TeV energies and also in different multiplicity classes. The radial flow, $<beta>$ is almost independent of collision energy and multiplicity whereas the behavior of kinetic freeze-out temperature significantly depends on multiplicity classes. It is found that the Tsallis distribution generally leads to a better description for the complete transverse momentum spectra whereas the BGBW model explains the bulk part of the system.
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