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New parameter free calculations including a variety of necessary kinematic and dynamic effects show that the results of BNL $(p,2p)$ measurements are consistent with the expectations of color transparency.
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We apply the GLV reaction operator solution to the Vitev-Gunion-Bertsch (VGB) boundary conditions to compute the all-order in nuclear opacity non-abelian gluon bremsstrahlung of event-by-event fluctuating beam jets in nuclear collisions. We evaluate analytically azimuthal Fourier moments of single gluon, $v_n^M{1}$, and even number $2ell$ gluon, $v_n^M{2ell}$ inclusive distributions in high energy p+A reactions as a function of harmonic $n$, %independent target recoil cluster number, $M$, and gluon number, $2ell$, at RHIC and LHC. Multiple resolved clusters of recoiling target beam jets together with the projectile beam jet form Color Scintillation Antenna (CSA) arrays that lead to characteristic boost non-invariant trapezoidal rapidity distributions in asymmetric $B+A$ nuclear collisions. The scaling of intrinsically azimuthally anisotropic and long range in $eta$ nature of the non-abelian br leads to $v_n$ moments that are similar to results from hydrodynamic models, but due entirely to non-abelian wave interference phenomena sourced by the fluctuating CSA. Our analytic non-flow solutions are similar to recent numerical saturation model predictions but differ by predicting a simple power-law hierarchy of both even and odd $v_n$ without invoking $k_T$ factorization. A test of CSA mechanism is the predicted nearly linear $eta$ rapidity dependence of the $v_n(k_T,eta)$. Non-abelian beam jet br may thus provide a simple analytic solution to Beam Energy Scan (BES) puzzle of the near $sqrt{s}$ independence of $v_n(p_T)$ moments observed down to 10 AGeV where large $x$ valence quark beam jets dominate inelastic dynamics. Recoil br from multiple independent CSA clusters could also provide a partial explanation for the unexpected similarity of $v_n$ in $p(D)+A$ and non-central $A+A$ at same $dN/deta$ multiplicity as observed at RHIC and LHC.
A new variant of the effective pomeron exchange model is proposed for the description of the correlation, observed in $pp$ and $pbar{p}$ collisions at center-of-mass energy from SPS to LHC, between mean transverse momentum and charged particles multiplicity. The model is based on the Regge-Gribov approach. Smooth logarithmic growth with the collision energy was established for the parameter k, the mean rapidity density of charged particles produced by a single string. It was obtained in the model by the fitting of the available experimental data on charged particles rapidity density in $pp$ and $pbar{p}$ collisions. The main effect of the model, a gradual onset of string collectivity with the growth of collision energy, is accounted by a free parameter {beta} that is responsible in an effective way for the string fusion phenomenon. Another free parameter, t, is used to define string tension. We extract parameters {beta} and t from the available experimental results on <pt>-multiplicity correlation at nucleon collision energy $sqrt{s}$ from 17 GeV to 7 TeV. Smooth dependence of both {beta} and t on energy allows to make predictions for the correlation behavior at the collision energy of 14 TeV. The indications to the string interaction effects in high multiplicity events in $pp$ collisions at the LHC energies are also discussed.
We develop a Monte-Carlo event generator based on combination of a parton production formula including the effects of parton saturation (called the DHJ formula) and hadronization process due to the Lund string fragmentation model. This event generator is designed for the description of hadron productions at forward rapidities and in a wide transverse momentum range in high-energy proton-proton collisions. We analyze transverse momentum spectra of charged hadrons as well as identified particles; pion, kaon, (anti-)proton at RHIC energy, and ultra-forward neutral pion spectra from LHCf experiment. We compare our results to those obtained in other models based on parton-hadron duality and fragmentation functions.
We present a study of transverse momentum ($p_{T}$) spectra of unidentified charged particles in pp collisions at RHIC and LHC energies from $sqrt{s}$ = 62.4 GeV to 13 TeV using Tsallis/Hagedorn function. The power law of Tsallis/Hagedorn form gives excellent description of the hadron spectra in $p_{T}$ range from 0.2 to 300 GeV/$c$. The power index $n$ of the $p_T$ distributions is found to follow a function of the type $a+b/sqrt {s}$ with asymptotic value $a = 5.72$. The parameter $T$ governing the soft bulk contribution to the spectra remains almost same over wide range of collision energies. We also provide a Tsallis/Hagedorn fit to the $p_{T}$ spectra of hadrons in pPb and different centralities of PbPb collisions at $sqrt{s_{NN}}$ = 5.02 TeV. The data/fit shows deviations from the Tsallis distribution which become more pronounced as the system size increases. We suggest simple modifications in the Tsallis/Hagedorn power law function and show that the above deviations can be attributed to the transverse flow in low $p_T$ region and to the in-medium energy loss in high $p_T$ region.
We perform an analytic calculation of the color fields in heavy-ion collisions by considering the collision of longitudinally extended nuclei in the dilute limit of the Color Glass Condensate effective field theory of high-energy QCD. Based on general analytic expressions for the color fields in the future light cone, we evaluate the rapidity profile of the transverse pressure within a simple specific model of the nuclear collision geometry and compare our results to 3+1D classical Yang-Mills simulations.
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