# Anomalous Pion Production in High Energy Particle Collisions Alexander Bylinkin, Andrey Rostovtsev XV Moscow School of Physics XXXX ITEP Winter School.

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Anomalous Pion Production in High Energy Particle Collisions Alexander Bylinkin, Andrey Rostovtsev XV Moscow School of Physics XXXX ITEP Winter School 14-21 February, 2012

Introduction Motivation: There exists a large body of experimental data on hadron production in various experiments. During its analysis different collaborations treat their data separately. It is interesting to analyze this data altogether! Analyzed Data: Charged pion, kaon, proton and antiproton spectra produced in: Collision typeEnergy √sExperiment pp 53 – 7000 GeV ISR, UA1, CDF, STAR, CMS, ALICE γγ, γp 100-200 GeV H1, Opal AuAu 200 GeV PHENIX

Charge Particle Spectra and the Fit Function Differential Invariant Cross-Section p T – transverse momentum, y - rapidity Boltzmann exponent pQCD power-law A sum of exponential & power-law terms The widely used approximation New Approach

Why Our Approach is Better? The new parameterization shows much better approximation of the experimental data. UA1 630GeV RHIC 200GeV Experimental data divided over the values of the fit function in corresponding points Defects in the fit with a standard function

Anomalies in Pion Production Spectra The relative contribution R of the exponential and power-law terms can be calculated by formula: The sizeable exponential term contribution exists only in pion spectra produced in pp and heavy ion collisions Spectra shapes of pions, kaons and protons Relative contributions of the exponential and power-law terms R = Power-law _ Exp + Power-law No exponent power-law exponent

Relation with Previous Experiments Particles in hadronic decays of Z-boson are produced with a probability described by an exponential function of the hadron mass squared Probability divided over the exponential function: The pion production is 3 times larger than it is expected The ratio R for pions in our analysis equals to ~0.25 which means that the contribution of the exponential term is 3 times larger than of the power-law These effects may have the common nature! π±π± π±π±

Summary Charged particle spectra produced in various experiments were analyzed Anomalous behavior in pion production was observed Only pion spectra produced in pp and heavy ion collisions have the sizeable exponential term Connection with previous experiments was discussed Are anomalous behavior found in our analysis and the excess in pion production from previous experiments related to each other? Thank you for your attention!

Comparison with MC Data Hypothesis: production of pions via multiple cascade decays results in the transformation of their spectra into an exponential distribution. Statement: decay processes are described quite accurately in Pythia MC generators don’t reproduce the spectra shape of the experimental data MC generated spectrum for minimum bias events in pp-collisions at √s = 630GeV MC and experimental data divided over the fit function obtained for the experimental spectrum

Correlation Between Parameters Better approximation is not just a result of exceeding the number of parameters of the fit function T and T e parameters in the power-law and exponential terms of the fit function are strongly correlated with each other

R Value The relative contribution of exponential and power-law terms can be calculated by integrating each term by transverse momentum from 0 to the upper bound of the kinematical region

J/ψ Spectra J/ψ has no exponential term in its spectrum

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