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Measurement of $hat{q}$ in Relativistic Heavy Ion Collisions using di-hadron correlations

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 نشر من قبل Michael J. Tannenbaum
 تاريخ النشر 2017
  مجال البحث
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 تأليف M. J. Tannenbaum




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The azimuthal width of the di-hadron correlations in p$+$p collisons, beyond the fragmentation transverse momentum, $j_T$, is dominated by $k_T$, the so-called intrinsic transverse momentum of a parton in a nucleon, which can be measured. The predicted azimuthal broadening in A$+$A collisions should produce a larger $k_T$ than in p$+$p collisions. The present work introduces the observation 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 both the trigger and away parent partons when comparing to the $k_T$ measured with the same di-hadron $p_{Tt}$ and $p_{Ta}$ in Au$+$Au collisions. This idea is applied to a recent STAR di-hadron measurement, with result $langle{hat{q}L}rangle=2.1pm 0.6$ GeV$^2$. This is more precise but in agreement with a theoretical calulation of $langle{hat{q}L}rangle=14^{+42}_{-14}$ GeV$^2$ using the same data. Assuming a length $langle{L}rangleapprox 7$ fm for central Au$+$Au collisions the present result gives $hat{q}=0.30pm 0.09$ GeV$^2$/fm, in fair agreement with the JET collaboration result of $hat{q}approx 1.2pm 0.3$ GeV$^2$/fm at initial time $tau_0=0.6$ fm/c in Au+Au collisions at $sqrt{s_{NN}}=200$ GeV.



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120 - M. J. Tannenbaum 2018
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