Direct Photon Pair Production Research Articles

NNLO+PS Monte Carlo simulation of photon pair production with MiNNLOPS

We present a NNLO QCD accurate event generator for direct photon pair production at hadron colliders, based on the MiNNLOPS formalism, within the Powheg Box Res framework. Despite the presence of the photons requires the use of isolation criteria, our generator is built such that no technical cuts are needed at any stage of the event generation. Therefore, our predictions can be used to simulate kinematic distributions with arbitrary fiducial cuts. Furthermore, we describe a few modifications of the MiNNLOPS formalism in order to allow for a setting of the renormalization and factorization scales more similar to that of a fixed-order computation, thus reducing the numerical impact of higher-order terms beyond the nominal accuracy. Finally, we show several phenomenological distributions of physical interest obtained by showering the generated events with Pythia8, and we compare them with the 13 TeV data from the ATLAS Collaboration.

Measurement of the differential cross sections for isolated direct photon pair production in [formula omitted] collisions at [formula omitted

We present measurements of direct photon pair production cross sections using 8.5 fb−1 of data collected with the D0 detector at the Fermilab Tevatron pp¯ collider. The results are presented as differential distributions of the photon pair invariant mass dσ/dMγγ, pair transverse momentum dσ/dpTγγ, azimuthal angle between the photons dσ/dΔϕγγ, and polar scattering angle in the Collins–Soper frame dσ/d|cosθ⁎|. Measurements are performed for isolated photons with transverse momenta pTγ>18(17) GeV for the leading (next-to-leading) photon in pT, pseudorapidities |ηγ|<0.9, and a separation in η–ϕ space ΔRγγ>0.4. We present comparisons with the predictions from Monte Carlo event generators diphox and resbos implementing QCD calculations at next-to-leading order, 2γnnlo at next-to-next-to-leading order, and sherpa using matrix elements with higher-order real emissions matched to parton shower.

DØ Results on Diphoton Direct Production and Photon + b and c Jet Production

In this note we present measurements of the direct photon pair production cross sections using 8.5 fb −1 of data collected with the DO detector at the Fermilab Tevatron p ¯ p collider at √ s = 1.96 TeV. The results are shown as differential distributions with respect to the photon pair mass , pair transverse momentum, azimuthal angle, and polar scattering angle in the Collins- Soper frame. We also present measurements of the differential cross section dσ/d p γ T for the inclusive production of a photon in association with a b- or c-quark jet. The results are based on 8.7 fb −1 of data, and the measured cross sections are compared with next-to-leading order perturbative QCD calculations using different sets of parton distribution functions as well as to pre dictions based on the kT-factorization QCD approach, and those from various Monte Carlo event generators.

Measurement of direct photon pair production cross sections in [formula omitted] collisions at [formula omitted

We present a measurement of direct photon pair production cross sections using 4.2 fb−1 of data collected with the D0 detector at the Fermilab Tevatron pp¯ Collider. We measure single differential cross sections as a function of the diphoton mass, the transverse momentum of the diphoton system, the azimuthal angle between the photons, and the polar scattering angle of the photons. In addition, we measure double differential cross sections considering the last three kinematic variables in three diphoton mass bins. The results are compared with different perturbative QCD predictions and event generators.

Direct photon pair production at the LHC to [formula omitted] in TeV scale gravity models

The first results on next-to-leading order QCD corrections to production of direct photon pairs in hadronic collisions in the extra dimension models — ADD and RS are presented. Various kinematical distributions are obtained to order α s in QCD by taking into account all the parton level subprocesses. Our Monte Carlo based code incorporates all the experimental cuts suitable for physics studies at the LHC. We estimate the impact of the QCD corrections on various observables and find that they are significant. We also show the reduction in factorization scale uncertainty when O ( α s ) effects are included.

A full next-to-leading order study of direct photon pair production in hadronic collisions

We discuss the production of photon pairs in hadronic collisions, from fixed target to LHC energies. The study which follows is based on a QCD calculation at full next-to-leading order accuracy, including single and double fragmentation contributions, and implemented in the form of a general purpose computer program of "partonic event generator" type. To illustrate the possibilities of this code, we present the comparison with observables measured by the WA70 and D0 collaborations, and some predictions for the irreducible background to the search of Higgs bosons at LHC in the channel $h \to \gamma \gamma$. We also discuss theoretical scale uncertainties for these predictions, and examine several infrared sensitive situations which deserve further study.

Direct photon pair production from pions and protons at 200 GeV/ c

We present results from a direct photon pair search performed with the NA3 spectrometer, using incident positive and negative beams at 200 GeV/ c interacting with a carbon target. The experiment is sensitive to photons with p T >1.8 GeV/ c and −0.4⩽y ∗⩽1.0 , one in each arm of the apparatus. A 3 standard deviation signal is seen in τ − and p interactions. The cross section is higher than the second order QCD calculations, but systematic errors are large.

Direct-photon pair production

Direct-photon pair production in high-energy hadron collisions is considered. After discussing general aspects of such reactions and giving a brief historical survey of the subject, we present some calculations on the contributions from $q\overline{q}$ and $\mathrm{gg}$ collisions (the latter via the quark box) to the $\ensuremath{\gamma}\ensuremath{\gamma}$ continuum, and on possible resonant contributions. Finally, an estimation of the indirect-photon background (mainly due to ${\ensuremath{\pi}}^{0}$ and $\ensuremath{\eta}$ decay, and to quark bremsstrahlung) is given for colliding-beam conditions at high energy; assuming both photons to be measured at 90\ifmmode^\circ\else\textdegree\fi{} with equal and opposite momenta, and (within experimental limits) unaccompanied by any hadrons or additional photons, it is shown that this background can be sharply reduced.

Direct-photon pair production in hadron collisions as a check of QCD

Reactions hh→γγX are computed, assuming both photons to be omitted, with equal and opposite momenta, at 90° in the overall c.m. frame. Contributions of qq̄ and gg interactions are considered. Such measurements might provide a check of gluon distribution functions.