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Register a new userComparative Analysis of Pion, Kaon and Proton Spectra Produced at PHENIX
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The shapes of invariant differential cross section for identified pi,K, p and pbar production as function of transverse momentum measured in pp collisions by the PHENIX detector are analyzed. Simultaneous fit of these data to the sum of exponential and power-law terms show significant difference in the exponential term contributions. This effect qualitatively explains the observed shape of the experimental K/pi and p/pi yield ratios measured as function of transverse momentum of produced hadrons. A picture with two types of mechanisms for hadron production is given.
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We determine the leading Fock state light front wave functions (LFWFs) of the pion and kaon via light front projections of the covariant Bethe-Salpeter wave function. Using these LFWFs we study the multi-dimensional images of the valence quarks in the pion and kaon that are provided by their generalized parton distribution functions (GPDs) and transverse momentum dependent parton distribution functions (TMDs). Moments of the GPDs are taken to obtain the electromagnetic and gravitational form factors of the pion and kaon, and comparisons to available experimental and lattice data are made. Highlights from this study include predictions that the mean-squared impact parameter for the quarks in the pion and kaon are: $langle vec{b}_T^2rangle_{u}^pi=0.11$fm$^2$, $langle vec{b}_T^2rangle_{s}^K=0.08$fm$^2$, and $langle vec{b}_T^2rangle_{u}^K=0.13$fm$^2$, and therefore the $s$ quark in the kaon is much closer to the center of transverse momentum than the $u$ quark. From the electromagnetic and gravitational form factors we find that the light-cone energy radii are about 60% smaller than the light-cone charge radii for each quark sector in the pion and kaon. A quantitative measure of the importance of the leading Fock state is obtained via comparison with a full DSE calculation (containing an infinite tower of Fock states) for the pion form factor.
In the present work the Mott effect for pions and kaons is described within a Beth- Uhlenbeck approach on the basis of the PNJL model. The contribution of these degrees of freedom to the thermodynamics is encoded in the temperature dependence of their phase shifts. A comparison with results from $N_f = 2 + 1$ lattice QCD thermodynamics is performed.
We discuss a general diagrammatic description of n-point functions in the QCD instanton vacuum that resums planar diagrams, enforces gauge invariance and spontaneously broken chiral symmetry. We use these diagrammatic rules to derive the pion and kaon quasi-parton amplitude and distribution functions at leading order in the instanton packing fraction for large but finite momentum. The instanton and anti-instanton zero modes and non-zero modes are found to contribute to the quasi-distributions, but the latter are shown to drop out in the large momentum limit. The pertinent pion and kaon parton distribution amplitudes and functions are made explicit at the low renormalization scale fixed by the inverse instanton size. Assuming that factorization holds, the pion parton distributions are evolved to higher renormalization scales with one-loop DGLAP and compared to existing data.
The behavior of strange matter in the frame of the SU(3)Polyakov-loop extended Nambu-Jona-Lasinio model including $U_A(1)$ anomaly is considered. We discuss the appearance of a peak in the ratio of the number of strange mesons to non-strange mesons known as the horn. The PNJL model gives a schematic description of the chiral phase transition and meson properties at finite temperature and density. Using the model, we can show that the splitting of kaon and anti-kaon masses appears as a result of introduction of density. This may explain the difference in the $K^+/pi^+$ ratio and $K^-/pi^-$ ratio at low $sqrt{s_{NN}}$ and their tendency to the same value at high $sqrt{s_{NN}}$. We also show that the rise in the ratio $K^+/pi^+$ appears near CEP when we build the $K^+/pi^+$ ratio along the phase transition diagram and it can be considered as a critical region signal.
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