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In the BDMPSZ model, the energy loss of an outgoing parton in a medium$-dE/dx$ is the transport coefficient $\hat{q}$ times $L$ the length traveled.This results in jet quenching, which is well established. However BDMPSZ alsopredicts an azimuthal broadening of di-jets also proportional to $\hat{q}L$which has so far not been observed. The broadening should produce a larger$k_T$ in A$+$A than in p$+$p collisions. This presentation introduces theobservation that the $k_T$ measured in p$+$p collisions for di-hadrons with$p_{Tt}$ and $p_{Ta}$ must be reduced to compensate for the energy loss of boththe trigger and away parent partons when comparing to the $k_T$ measured withthe same di-hadron $p_{Tt}$ and $p_{Ta}$ in A$+$A collisions. This idea isapplied to a recent STAR di-hadron measurement in Au$+$Au at$\sqrt{s_{NN}}$=200 GeV, [Phys. Lett. B760 (2016) 689], with result$<{\hat{q}L}>=2.1\pm 0.6$ GeV$^2$. This is more precise but in agreement with atheoretical calculation of $<{\hat{q}L}>=14^{+42}_{-14}$ GeV$^2$ using the samedata. Assuming a length $<{L}>\approx 7$ fm for central Au$+$Au collisions thepresent result gives $\hat{q}\approx 0.30\pm 0.09$ GeV$^2$/fm, in fairagreement with the JET collaboration result from single hadron suppression of$\hat{q}\approx 1.2\pm 0.3$ GeV$^2$/fm at an initial time $\tau_0=0.6$ fm/c inAu$+$Au collisions at $\sqrt{s_{NN}}=200$ GeV. There are several interestingdetails to be discussed: for a given $p_{Tt}$ the $<{\hat{q}L}>$ seems todecrease then vanish with increasing $p_{Ta}$; the di-jet spends a much longertime in the medium ($\approx 7$ fm/c) then $\tau_0=0.6$ fm/c which likelyaffects the value of $\hat{q}$ that would be observed.

Measurement of $\hat{q}$ in RHI collisions using di-hadron correlations