Transverse Momentum Cross Section Research Articles

Transverse momentum cross section ofe+e−pairs in theZ-boson region frompp¯collisions ats=1.96 TeV

The transverse momentum cross section of $e^+e^-$ pairs in the $Z$-boson mass region of 66-116 GeV/$c^2$ is precisely measured using Run II data corresponding to 2.1 fb$^{-1}$ of integrated luminosity recorded by the Collider Detector at Fermilab. The cross section is compared with quantum chromodynamic calculations. One is a fixed-order perturbative calculation at ${\cal O}(\alpha_s^2)$, and the other combines perturbative predictions at high transverse momentum with the gluon resummation formalism at low transverse momentum. Comparisons of the measurement with calculations show reasonable agreement. The measurement is of sufficient precision to allow refinements in the understanding of the transverse momentum distribution.

Properties of jets measured from tracks in proton-proton collisions at center-of-mass energys=7 TeVwith the ATLAS detector

Jets are identified and their properties studied in center-of-mass energy sqrt(s) = 7 TeV proton-proton collisions at the Large Hadron Collider using charged particles measured by the ATLAS inner detector. Events are selected using a minimum bias trigger, allowing jets at very low transverse momentum to be observed and their characteristics in the transition to high-momentum fully perturbative jets to be studied. Jets are reconstructed using the anti-kt algorithm applied to charged particles with two radius parameter choices, 0.4 and 0.6. An inclusive charged jet transverse momentum cross section measurement from 4 GeV to 100 GeV is shown for four ranges in rapidity extending to 1.9 and corrected to charged particle-level truth jets. The transverse momenta and longitudinal momentum fractions of charged particles within jets are measured, along with the charged particle multiplicity and the particle density as a function of radial distance from the jet axis. Comparison of the data with the theoretical models implemented in existing tunings of Monte Carlo event generators indicates reasonable overall agreement between data and Monte Carlo. These comparisons are sensitive to Monte Carlo parton showering, hadronization, and soft physics models.

State-selective charge exchange from Na(3s) and Na*(3p) by highly charged ions

State-selective charge exchange cross sections and momentum spectra are calculated for collisions of Xe18+ and Xe54+ ions with Na(3s) and Na*(3p) over the energy range of 0.1–10.0 keV/amu. The classical trajectory Monte Carlo method is used which includes all two-body interactions. The n-level cross sections are found to be rather insensitive to collision energy below 1 keV/amu. In contrast, the transverse momentum cross sections for specific n-levels change rapidly with energy. However, this latter variation in energy is found to be in general agreement with simple scaling rules. Experimental state-selective data are available for Xe18+ over a limited energy range; they are found to be in reasonable accord with the calculations.

Transverse momentum and total cross section of e(+)e(-) pairs in the Z-boson region from p&pmacr; collisions at sqrt

The transverse momentum and total cross section of e(+)e(-) pairs in the Z-boson region of 66<M(ee)<116 GeV/c(2) from p&pmacr; collisions at sqrt[s] = 1.8 TeV are measured using 110 pb(-1) of collisions taken by the Collider Detector at Fermilab during 1992-1995. The total cross section is measured to be 248+/-11 pb. The differential transverse momentum cross section is compared with calculations that match quantum chromodynamics perturbation theory at high transverse momentum with the gluon resummation formalism at low transverse momentum.

The transverse momentum distribution of Drell-Yan pairs in perturbation theory

We calculate, in lowest-order perturbation theory, the cumulative transverse momentum cross section for the Drell-Yan process in the regime m 2⪡ p T 2⪡ q 2, keeping both single and double logarithmic terms. We verify that this distribution takes the proposed form of a product of structure functions evaluated at p T 2 and the square of the Sudakov form factor S( p T 2/ q 2), evaluated to subleading order.