Properties of photon plus two-jet events inp¯pcollisions ats=1.8

Abstract

We present the first general measurements (invariant-mass, transverse-energy, and angular distributions) of the process, (p) over bar p-->gamma+2 jets + X, using data collected by the CDF at Fermilab. We compare the data with predictions from a tree-level QCD calculation and the PYTHIA shower Monte Carlo program. Our data sample is particularly sensitive to contributions from initial-and final-state radiation of photons and jets. Using the PYTHIA Monte Carlo program, we contrast the kinematical distributions for direct photon production with those for initial-and final-state photon radiation (bremsstrahlung). Based on the angular distributions, we find that our data favor a mixture of bremsstrahlung and direct photon production, as predicted, over either process alone

Measurement of the triple-differential cross section for photon + jets production in proton-proton collisions at $ \sqrt{s} $ = 7 TeV

“…x 0.4 and 1600 ≤ Q 2 ≤ 9 × 10 4 GeV 2 , and extends the kinematic regions of photon p T covered by earlier measurements [14][15][16][17][18][19][20][21][22][23][24]. Measurements of the differential cross sections and ratios of the differential cross sections for different angular configurations are compared to theoretical predictions.…”

Measurement of the production cross section of an isolated photon associated with jets in proton-proton collisions ats=7 TeVwith the ATLAS detector

“…0) or opposite-sign ( y jet < 0), and the results are compared to next-toleading order (NLO) perturbative QCD theoretical predictions. Separating the selected phase space into these six different angular configurations allows the comparison between data and theoretical predictions in configurations where the relative contribution of the fragmentation component to the total cross section is different, and in different ranges of x, which in the leading-order approximation is equal to x ¼ T Þ 2 1:6 Â 10 5 GeV 2 , thus extending the kinematic reach of previous photon þ jet measurements at hadron [16][17][18][19] and electron-proton [20][21][22][23] colliders.…”

Azimuthal decorrelations and multiple parton interactions inγ+2jet andγ+3jet events inpp¯

“…The ∆φ distribution in γ + 2 jet events has been used to estimate the DP fraction by the CDF Collaboration [33]. The p T spectrum for jets from dijet events falls faster than that for jets, resulting from ISR and FSR in γ + jet events, and thus the DP fractions should depend on the jet p T [1, 3-6, 9, 24].…”

“…These cross sections are sensitive to the contributions from jets originating from additional parton hard interactions (beyond the dominant one) and can be used to improve existing MPI models, and to estimate the fractions of such events [21,24,33]. The cross section measurements are performed at the particle level, which means that the jets' four-momenta represent the real energy and direction of the jet of stable particles resulting from the hadronization process following the pp interaction [34].…”