Mechanism of hadron production in high energyparticle collisions A. Bylinkin (Supervisor: A. Rostovtsev) XLI ITEP Winter School 12-19 February, 2013
Charge Particle Spectra and the Fit Function Differential Invariant Cross-Section pT – transverse momentum, y - rapidity Boltzmann exponent pQCD power-law The widely used approximation New Approach A sum of exponential & power-law terms
Why the new approach matches the data better? Systematic defects in the data description using traditional approach Experimental data divided over the values of the fit function in corresponding points UA1 630GeV RHIC 200GeV UA1 630GeV RHIC 200GeV ²/ndf = 288/44 ²/ndf = 87/25 ²/ndf = 54/42 ²/ndf = 22/23 The new parameterization shows much better approximation of the experimental data.
Qualitative model 2 Mechanisms of hadron production 1. Radiation of hadrons by valence quarks Theses partons exist long before the interaction and considered as a thermalized statistical state Boltzmann-like exponential distribution 2. Virtual partons exchanged between colliding partonic systems BFKL Pomeron exchange in QCD power-law spectrum (typical for pQCD) Power-law _ R = The model was discussed with Mihail Ryskin. Exp + Power-law
Type of produced particle QCD-fluctuations are democratic to quark flavour Prediction:Kaon spectra should have less exponential distribution then pion exponent power-law Power-law _ R = Exp + Power-law power-law No exponent
Dependence of the spectra shapeon multiplicity Charge multiplicity is proportional to the number of Pomerons involved Prediction: Exponential contribution will decrease with the increase of multiplicity STAR data Power-law _ R = Exp + Power-law
Energy of Collision The number of pomerons involved is increasing with the growth of the collision energy Prediction: Exponential contribution will decrease with the increase of √s ISR, UA1, CDF, LHC data Power-law _ R = Exp + Power-law
Dependence of the spectra shape on pseudorapidity In proton fragmentation region the role of valence quarks is more important Prediction: Dominance of exponential term in the high rapidity region Charge particle pseudorapidity distribution at √s ~ 630 Gev UA1 data Power-law _ R = Pomeron exchange Proton fragmentation Exp + Power-law
Dependence of the spectra shape on the type of colliding particles Exponential term is due to valence quarks Prediction:Spectra inγγ-collisions should have power-law term only Prediction: Inγp-collisions transition between two regimes of hadroproduction can be observed ep-collisions at HERA measured by the H1 experiment are the unique possibility to test this prediction Qualitative prediction of the model UA1 data L3 data Power-law _ R = Tracks measurable in H1 experiment at HERA (DESY, Hamburg) Exp + Power-law Measured data will be published soon!
Conclusion • Standard approximation was shown to provide poor description of the experimental data. • New better parameterization function was found. • Qualitative model of charge particle production was introduced. • Predictions of the model were tested. • An analysis of charge particle spectra in H1 experiment is proposed. Thank you for your attention!
References Systematic studies of hadron production spectra in collider experiments A.Bylinkin and A.Rostovtsev, arXiv:1008.0332 [hep-ph]. Anomalous behavior of pion production in high energy particle collisions A.Bylinkin andA.Rostovtsev,Eur.Phys.J.C72(2012)1961,arXiv:1112.5734 Comparative Analysis of Pion, Kaon and Proton Spectra Produced at PHENIX A.Bylinkin and A.Rostovtsev,arXiv:1203.2840 [hep-ph]. An analysis ofcharged particles spectra in events with different chargedmultiplicity. A.Bylinkin and A.Rostovtsev,arXiv:1205.4432 [hep-ph]. A variation of thecharged particle spectrum shape as function of rapidity inhigh energy pp collisions. A.Bylinkin and A.Rostovtsev,arXiv:1205.6382. [hep-ph]  Parametrization of the shape of hadron-production spectra in high-energy particle interactions A.A. Bylinkin, A.A. Rostovtsev, Phys.Atom.Nucl. 75 (2012) 999-1005, Yad.Fiz.75 (2012) 1060-1066 A photon-proton mariage A.A. Bylinkin, A.A. Rostovtsev. e-Print: arXiv:1209.0958 [hep-ph]
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
Correlation Between Parameters T and Te parameters in the power-law and exponential terms of the fit function are strongly correlated with each other Better approximation is not just a result of exceeding the number of parameters of the fit function
J/ψ Spectra J/ψ has no exponential term in its spectrum
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 and experimental data divided over the fit function obtained for the experimental spectrum MC generated spectrum for minimum bias events in pp-collisions at √s = 630GeV MC generators don’t reproduce the spectra shape of the experimental data
Dependence of the spectra shape on the type of produced particle QCD-fluctuations are democratic to quark flavour Prediction:Kaon spectra should have less exponential distribution then pion Phenix data p,pbar π± K± R = 0.72 R = 0.82 R = 0.25