Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userImproved Comparison of Measurements and Calculations of $hat{q}L$ via transverse momentum broadening in Relativistic Heavy Ion Collisions using di-hadron correlations
175
0
0.0
(
0
)
Authors
M. J. Tannenbaum
Ask ChatGPT about the research
No Arabic abstract
The renewed interest in analyzing RHIC data on di-hadron correlations as probes of final state transverse momentum broadening as shown at Quark Matter 2018[1] by theoretical calculations[6] compared to experimental measurements[4,5] led me to review the quoted theoretical calculations and experimental measurements because the theoretical calculation[6] does not show the PHENIX measurements[4] as published. The above references were checked and fits were performed to the published measurements[4,7] to determine $hat{q}L$ from the measured azimuthal broadening to compare with the theoretical calculation[6]. The new results will be presented in addition to some corrections to the previous work[3]. The measured values of $hat{q}L$ show the interesting effect of being consistent with zero for larger values of associated $p_{Ta}geq3$ GeV/c which is shown to be related to well known measurements of the ratio of the Au+Au to p+p associated $p_{Ta}$ distributions for a given trigger $p_{Tt}$ called $I_{AA}$[23,25]. Di-jets rather than di-hadrons are proposed as an improved azimuthal broadening measurement to determine $hat{q}L$ and possibly $hat{q}$.
rate research
Read More
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.
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 also predicts 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 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 A$+$A collisions. This idea is applied to a recent STAR di-hadron measurement in Au$+$Au at $sqrt{s_{NN}}$=200 GeV, [Phys. Lett. B760 (2016) 689], with result $<{hat{q}L}>=2.1pm 0.6$ GeV$^2$. This is more precise but in agreement with a theoretical calculation of $<{hat{q}L}>=14^{+42}_{-14}$ GeV$^2$ using the same data. Assuming a length $<{L}>approx 7$ fm for central Au$+$Au collisions the present result gives $hat{q}approx 0.30pm 0.09$ GeV$^2$/fm, in fair agreement with the JET collaboration result from single hadron suppression of $hat{q}approx 1.2pm 0.3$ GeV$^2$/fm at an initial time $tau_0=0.6$ fm/c in Au$+$Au collisions at $sqrt{s_{NN}}=200$ GeV. There are several interesting details to be discussed: for a given $p_{Tt}$ the $<{hat{q}L}>$ seems to decrease then vanish with increasing $p_{Ta}$; the di-jet spends a much longer time in the medium ($approx 7$ fm/c) then $tau_0=0.6$ fm/c which likely affects the value of $hat{q}$ that would be observed.
Results from Relativistic Heavy Ion Collider Physics in 2018 and plans for the future at Brookhaven National Laboratory are presented.
We calculate the cross section and transverse-momentum ($P_{bot}$) distribution of the Breit-Wheeler process in relativistic heavy-ion collisions and their dependence on collision impact parameter ($b$). To accomplish this, the Equivalent Photon Approximation (EPA) was generalized in a more differential way compared to the approach traditionally used for inclusive collisions. In addition, a lowest-order QED calculation with straightline assumption was performed as a standard baseline for comparison. The cross section as a function of $b$ is consistent with previous calculations using the equivalent one-photon distribution function. Most importantly, the $P_{bot}$ shape from this model is strongly dependent on impact parameter and can quantitatively explain the $P_{bot}$ broadening observed recently by RHIC and LHC experiments. This broadening effect from the initial QED field strength should be considered in studying possible trapped magnetic field and multiple scattering in a Quark-Gluon Plasma (QGP). The impact-parameter sensitive observable also provides a controllable tool for studying extreme electromagnetic fields.
Transverse-mass spectra, their inverse slopes and mean transverse masses in relativistic collisions of heavy nuclei are analyzed in a wide range of incident energies 2.7 GeV $le sqrt{s_{NN}}le$ 39 GeV. The analysis is performed within the three-fluid model employing three different equations of state (EoSs): a purely hadronic EoS, an EoS with the first-order phase transition and that with a smooth crossover transition into deconfined state. Calculations show that inverse slopes and mean transverse masses of all the species (with the exception of antibaryons within the hadronic scenario) exhibit a step-like behavior similar to that observed for mesons and protons in available experimental data. This step-like behavior takes place for all considered EoSs and results from the freeze-out dynamics rather than is a signal of the deconfinement transition. A good reproduction of experimental inverse slopes and mean transverse masses for light species (up to proton) is achieved within all the considered scenarios. The freeze-out parameters are precisely the same as those used for reproduction of particles yields in previous papers of this series. This became possible because the freeze-out stage is not completely equilibrium.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
