Study of double parton interactions in $\mathrm{diphoton}+\mathrm{dijet}$ events in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$

We use a sample of $\text{diphoton}+\text{dijet}$ events to measure the effective cross section of double parton interactions, which characterizes the area containing the interacting partons in proton-antiproton collisions, and find it to be ${\sigma }_{\text{eff}}=19.3\pm 1.4(\text{stat})\pm 7.8(\text{syst})\mathrm{mb}$. The sample was collected by the D0 detector at the Fermilab Tevatron collider in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ and corresponds to an integrated luminosity of $8.7{\mathrm{fb}}^{-1}$.

Figure 1

Schematic view of DP scattering processes producing $\gamma \gamma +\text{dijet}$ final state. The $\gamma \gamma$ process is shown for the $q\overline{q}$ scattering (above, light, blue) and box $gg$ diagram (below, light, blue). The additional dijet scattering is a darker diagram (red).

Figure 2

Fraction of the $gg\to \gamma \gamma$ contribution to the total direct cross section comprising the $q\overline{q}\to \gamma \gamma$ and $gg\to \gamma \gamma$ processes. $M_{\gamma \gamma }$ is the invariant mass of the diphoton.

Figure 3

Diagrams of $\gamma \gamma +\text{dijet}$ final state in the events with a single $p\overline{p}$ collision. (a) DP scattering with diphoton production overlaid with dijet production; (b) DP scattering with diphoton $+1$ jet production overlaid with dijet production, in which one of the two jets is lost (dotted line). They can also be used as an illustration of the two DI events if one assumes that the processes shown come from two distinct $p\overline{p}$ collisions.

Figure 4

A diagram illustrating the orientation of photon and jet transverse momenta vectors in $\gamma \gamma +\text{dijet}$ events. Vectors $q_T^1$ and $q_T^2$ are the $p_T$ imbalance vectors of diphoton and dijet pairs, respectively.

Figure 5

The fit of the 1VTX data $\mathrm{\Delta }S$ distribution with SP and DP templates to extract the DP fraction. The black points correspond to data, red boxes correspond to the DP signal MIXDP model normalized to the $f_{\mathrm{DP}}$ fraction obtained from the fit, and the blue triangles are the SP background template (SP1VTX) normalized to its fraction ($1-f_{\mathrm{DP}}$). The pink open boxes correspond to the sum of the signal and background (total).

Figure 6

Existing measurements of the effective cross section, ${\sigma }_{\text{eff}}$, compared to the result presented here (AFS: no uncertainty is reported; UA2: only a lower limit is provided). Results of the measurements are grouped by the final state.