arXiv subjects

Karoly Urmossy

Publications and source records attributed to Karoly Urmossy.

11 recordsLinked to original sources

arXiv2023

Scale dependence of the q and T parameters of the Tsallis distribution in the process of jet fragmentation

The dependence of the $q$ and $T$ parameters of the Tsallis-distribution-shaped fragmentation function (FF) on the fragmentation scale (found to be equal to the jet mass) is calculated via the resummation of the branching process of jet fragmentation in the leading-log appriximation (LLA) in the $ϕ^3$ theory. Jet and hadron spectra in electron-positron ($e^+e^-$) annihilations with 2- and 3-jet final states are calculated using virtual leading partons. It is found that jets, produced earlier in the branching process, are more energetic, and the energy, angle and multiplicity distributions of hadrons stemming from them are broader. It is also found that replacing the LL resummation in the branching process by a single splitting provides good approximation for the jet energy distribution in 2-jet events. Furthermore, a micro-canonical statistical event generator is presented for the event-by-event calculation of hadron momenta in $e^+e^-$ annihilations.

hep-ph↗

arXiv2019

Long-range Correlations in Massive Jets

We calculate the azimuthal anisotropy $v_2$ extracted from the large $Δy$ region of two particle $Δy-Δϕ$ correlations in a two-jet system, in which, the masses of the jets are not negligible compared to their energies. As the virtualities of the leading partons, initiating these jets are not negligible either, we use a recently developed, off-shell fragmentation model for the description of hadron production in the jets. We present the effect of the variation of jet mass and hadron multiplicity on the shape of the $v_2$ curve, and reproduce the low-multiplicity data set measured in proton-proton collisions at $\sqrt s = 13$ TeV.

hep-ph↗

arXiv2017

Off-shell Fragmentation

A new framework is sketched for the treatment of the hadronisation of a highly-virtual quark and anti-quark jet pair created in electron-positron annihilations. As in such a case, factorization theorem does not work, a new scale-evolution equation is proposed for the fragmentation functions. In this approach, the virtuality of the leading parton (taken to be equal to the mass of the jet it induces) is used as fragmentation scale.

hep-ph↗

arXiv2017

Jet mass fluctuations and fragmentation functions

The effect of jet mass fluctuations on the fragmentation process is examined in the framework of a statistical hadronisation model. In this model, the fragmentation scale Q is taken to be the virtuality of the leading parton, and jet mass fluctuations are accounted for through this quantity. The scale evolution of the model is treated in the phi^3 theory with leading-order splitting function and one-loop coupling.

hep-ph↗

arXiv2017

Jet Mass Dependence of Fragmentation in Positron-Proton Collisions

We propose the characterization of fragmentation functions by the energy fraction x, a hadron takes away from the energy of the jet measured in the frame co-moving with the jet. Besides, we propose the usage of the jet mass as the fragmentation scale Q. We show that these two Lorentz-invariant variables emerge naturally in a microcanonical ensemble with conserved fourmomentum. Then, we construct a statistical hadronisation model, in which, two features of the hadronic final states in various high-energy reactions (power law spectra and negative-binomial multiplicity distributions) can be connected simply. Finally, we analyse the scale dependence of the parameters of the model (power of the spectrum and mean energy per hadron) in the phi^3 theory. Fitting fragmentation functions in diffractive positron-proton collisions, we obtain a prediction for the jet mass dependence of the hadron multiplicity distribution inside jets.

hep-ph↗

arXiv2016

Three-dimensional Statistical Jet Fragmentation

We reproduce the distribution of the longitudinal and transverse components of momenta of charged hadrons stemming from jets created in proton-proton collisions at s^1/2 = 7 TeV by a statistical fragmentation model. Our hadronization model is based on microcanonical statistics and negative binomial multiplicity fluctuations. We describe the scale dependence of the fit parameters of the model with formulas obtained by approximating the exact solution of the DGLAP equation in the phi^3 theory with leading order splitting function and 1-loop coupling.

hep-ph↗

arXiv2015

Fragmentation in the phi^3 Theory and the LPHD Hypothesis

We present analytic solution of the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) equation at leading order (LO) in the phi^3 theory in 6 space-time dimensions. If the phi^3 model was the theory of strong interactions, the obtained solution would describe the distribution of partons in a jet. We point out that the local parton-hadron duality (LPHD) conjecture does not work in this hypothetical situation. That is, treatment of hadronisation of shower partons is essential for the description of hadron distributions in jets stemming from proton-proton (pp) collisions at \sqrt{s} = 7 TeV and from electron-positron (e+e-) annihilations at various collision energies. We use a statistical model for the description of hadronisation.

hep-ph↗

arXiv2014

Statistical Power Law due to Reservoir Fluctuations and the Universal Thermostat Independence Principle

Certain fluctuations in particle number at fixed total energy lead exactly to a cut-power law distribution in the one-particle energy, via the induced fluctuations in the phase-space volume ratio. The temperature parameter is expressed automatically by an equipartition relation, while the q-parameter is related to the scaled variance and to the expectation value of the particle number. For the binomial distribution q is smaller, for the negative binomial q is larger than one. These results also represent an approximation for general particle number distributions in the reservoir up to second order in the canonical expansion. For general systems the average phase-space volume ratio expanded to second order delivers a q parameter related to the heat capacity and to the variance of the temperature. However, q differing from one leads to non-additivity of the Boltzmann-Gibbs entropy. We demonstrate that a deformed entropy, K(S), can be constructed and used for demanding additivity. This requirement leads to a second order differential equation for K(S). Finally, the generalized q-entropy formula contains the Tsallis, Renyi and Boltzmann-Gibbs-Shannon expressions as particular cases. For diverging temperature variance we obtain a novel entropy formula.

cond-mat.stat-mech↗

arXiv2014

Disentangling Soft and Hard Hadron Yields in PbPb Collisions at $\sqrt{s_{NN}}$ = 2.76 ATeV

We demonstrate that charged pion spectra in central and peripheral PbPb collisions at $\sqrt{s}$ = 2.76 ATeV obtained via perturbative quantum chromodynamics improved parton model calculations [17] can be approximated by the Tsallis distribution for transverse momenta $p_T \geq$ 4 GeV/c. Then, we propose a model in which, hadrons produced in heavy-ion collisions stem either from "soft" or "hard" processes, and are distributed according to the Tsallis distribution in both types of yields. We describe transverse spectra as well as azimuthal anisotropy ($v_2$) of charged hadrons stemming from various centrality PbPb collisions at $\sqrt{s}$ = 2.76 ATeV [40,41,42] analytically. In addition, we find that the anisotropy decreases for more central collisions.

hep-ph↗

arXiv2011

Pion Production Via Resonance Decay in a Non-extensive Quark-Gluon Medium with Non-additive Energy Composition Rule

Resonance production and decay into pion pairs is simulated in a non-extensive quark matter with multi-particle interactions. Final state pion spectra are found to take the form of the Tsallis distribution, in accordance with measurements. It has also been shown that, if a large number of particles with these multi-particle interactions are constrained to a constant energy hyper-surface in phase space, the one-particle distribution is the Tsallis distribution.

hep-ph↗

arXiv2008

Non-Extensive Approach to Quark Matter

We review the idea of generating non-extensive stationary distributions based on abstract composition rules for the subsystem energies, in particular the relativistic generalized Boltzmann equation method. The thermodynamical behavior of such systems is investigated and hadron spectra stemming from relativistic heavy ion collisions are calculated by assuming quark coalescence.

hep-ph↗