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Register a new userThe effect of single-particle space-momentum angle distribution on two-pion HBT correlation in high-energy heavy-ion collisions
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Using several source models, we analyze the transverse momentum dependence of HBT radii in the relativistic heavy-ion collisions. The results indicate that the single-particle space-momentum angle distribution plays an important role in the transverse momentum dependence of HBT radii. In a cylinder source, we use several formulas to describe the transverse momentum dependence of HBT radii and the single-particle space-momentum angle distribution. We also make a numerical connection between them in the transverse plane.
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With the string melting version of a multiphase transport(AMPT) model, we analyze the transverse momentum dependence of HBT radius $R_{rm s}$ and the single-pion transverse angle distribution in central Au+Au collisions at $sqrt{S_{NN}}=19.6, 27, 39, 62.4, 200$ GeV. And base on a series of functions, a numerical connection between these two phenomena has been built. We can estimate the single-pion transverse angle distribution from the HBT analysis.
Two-particle rapidity (or pseudorapidity) correlation function $C(y_1, y_2)$ was used in analysing fluctuation of particle density distribution in rapidity in high-energy heavy-ion collisions. In our research, we argue that for a centrality window, some additional correlation may be caused by a centrality span, when the mean two- and single-particle densities over a centrality window are used directly in the calculation , just like $left<N(y_1, y_2) right> / left[left<N(y_1)right>left<N(y_2)right>right]$. We concentrate on removing the influence of collision-centrality span on correlation function, and two calculation methods are raised. In one method, correlation coefficients are considered to be the ratios of probabilities (not the particle density). In the other method, a relative multiplicity is introduced to unity the events of different centralities. For testing the methods, {sc ampt} model is used and a toy granular model is built to simulate the fluctuation of particle density in rapidity.
Momentum correlation functions at small relative momenta are calculated for light particles $left(n, p, d, tright)$ emitted from $^{197}$Au + $^{197}$Au collisions at different impact parameters and beam energies within the framework of the isospin-dependent quantum molecular dynamics model complemented by the $Lednickacute{y}$ and $Lyuboshitz$ analytical method. We first make sure our model is able to reproduce the FOPI data of proton-proton momentum correlation in a wide energy range from 0.4$A$ GeV to 1.5$A$ GeV. Then we explore more physics insights through the emission times and momentum correlations among different light particles. The specific emphasize is the effects of total pair momentum among different light particles, impact parameters and in-medium nucleon-nucleon cross section. Both two-deuteron and two-triton correlation functions are anti-correlation due to the final state interaction, and they are affected by in-medium nucleon-nucleon cross section for the higher total momentum of the particle pairs, but not for the lower ones. In addition, impact parameter and in-medium nucleon-nucleon cross section dependences of the emission source radii are extracted by fitting the momentum correlation functions. The results indicate that momentum correlation functions gating with total pair momentum is stronger for the smaller in-medium nucleon-nucleon cross section factor $left(etaright)$ or impact parameter $left(bright)$. Non-identical particle correlations ($np, pd, pt, $ and $dt$) are also investigated by the velocity-gated correlation functions which can give information of the particles emission sequence, and the result indicates that heavier ones $left(deuteron/tritonright)$ are, one the average, emitted earlier than protons, in the small relative momentum region.
In central Au-Au collisions at top RHIC energy, two particle correlation measurements with identified hadron trigger have shown attenuation of near side proton triggered jet-like yield at intermediate transverse momentum ($p{_T}$), 2$< p{_T} <$ 6 GeV/$it{c}$. The attenuation has been attributed to the anomalous baryon enhancement observed in the single inclusive measurements at the same $p{_T}$ range. The enhancement has been found to be in agreement with the models invoking coalescence of quarks as a mechanism of hadronization. Baryon enhancement has also been observed at LHC in the single inclusive spectra. We study the consequence of such an enhancement on two particle correlations at LHC energy within the framework of A Multi Phase Transport (AMPT) model that implements quark coalescence as a mode of hadronization. In this paper we have calculated the proton over pion ratio and the near side per trigger yield associated to pion and proton triggers at intermediate $p{_T}$ from String Melting (SM) version of AMPT. Results obtained are contrasted with the AMPT Default (Def.) which does not include coalescence. Baryon enhancement has been observed in AMPT SM at intermediate $p{_T}$. Near side jet-like correlated yield associated to baryon (proton) trigger in the momentum region where baryon generation is enhanced is found to be suppressed as compared to the corresponding yields for the meson (pion) trigger in most central Pb-Pb events. No such effect has been found in the Default version of AMPT.
The short-range correlation (SRC) induced by the tensor force in the isosinglet neutron-proton interaction channel leads to a high-momentum tail (HMT) in the single-nucleon momentum distributions n(k) in nuclei. Owing to the remaining uncertainties about the tensor force, the shape of the nucleon HMT may be significantly different from the dilute interacting Fermi gas model prediction $n(k) sim1/k^4$ similar to the HMT in cold atoms near the unitary limit. Within an isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck transport model incorporating approximately the nucleon HMT, we investigate hard photon emissions in $^{14}$N+$^{12}$C and $^{48}$Ca+$^{124}$Sn reactions at beam energies around the Fermi energy. Imprints of different shapes of the HMT on the energy spectrum, angular distribution and transverse momentum spectrum of hard photons are studied. While the angular distribution does not carry any information about the shape of the nucleon HMT, the energy spectra and especially the mid-rapidity transverse momentum spectra of hard photons are found to bare strong imprints of the shapes of nucleon HMTs in the two colliding nuclei.
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