^{*}

^{†}

pranjal.sarma@cern.ch

Corresponding author: buddhadeb.bhattacharjee@cern.ch

^{3}.

Nonstatistical fluctuation in pseudorapidity (

Understanding the particle production mechanism is one of the primary goals of high-energy

To gather any meaningful information about the particle production mechanism, it is therefore important to disentangle and analyze these anomalous fluctuations arising out of some dynamical processes, from that of noise arising due to the finite number of available particles in the final state. The scaled factorial moment (SFM) technique, as proposed by Bialas and Peschanski

Indications of the existence of a new state of deconfined matter, called quark-gluon plasma (QGP), have been provided for

The PYTHIA Monte Carlo event generator is a general purpose perturbative-QCD based event generator. It uses a factorized perturbative expansion for the hard parton-parton interaction, combined with parton showers, and details models for hadronization and multiple parton interactions. It has been extensively used to describe

Further, in PYTHIA, color reconnection (CR), a string fragmentation model, has been implemented where the final partons are considered to be color connected in such a way that the total string length becomes as short as possible

Even though the technique of estimation of the scaled factorial moment is a well-established mathematical tool of high-energy nuclear collision studies and is described in detail in a number of works

Let us consider the distribution of the charged particles in the pseudorapidity

Such moments for a particular bin are first calculated for all events and then averaged over all events. This average moment is then calculated for all bins and again averaged over all bins. This averaging procedure is called vertical averaging

On the other hand, if the factorial moment is first calculated for a bin and then averaged over all bins and this averaged moment is then calculated for all events and again averaged over all events, then this method of estimation of scaled factorial moments is called horizontal averaging

The expression for the vertically averaged scaled factorial moment is given by

Here, it is worth mentioning that the horizontal scaled factorial moment technique has the limitation of its dependence on the shape of the single particle density distribution spectra. However, the shape dependence of the horizontally averaged SFM can be eliminated by converting the distribution of the particles in pseudorapidity space to a distribution of a new cumulative variable

For power law type dependence of

A total of approximately

The pseudorapidity distributions of the primary charged particles within the acceptance of ALICE detector, for both minimum-bias (MB) and high-multiplicity (

Pseudorapidity distribution of the primary charged particles for PYTHIA Monash (default) generated data (a) compared with experimental data of ALICE in minimum-bias

Figure

Horizontally averaged scaled factorial moments

In Fig.

The intermittent pattern in the emission source of the particle in high-energy nuclear collisions may be different in different phase space, depending on the nature of the emission spectra. To realize the (a)symmetric nature of the intermittent pattern in

The

Values of the intermittency index

It was pointed out by Ochs

To study the fluctuation in two-dimensional pseudorapidity-azimuthal (

The

Values of the intermittency index

The anomalous dimension

Variation of

Bialas and Zalewski

The variations of

Variation of

In PYTHIA, color reconnection (CR) is a string fragmentation model where final partons are considered to be color connected in such a way that the total string length becomes as short as possible

Color reconnection in PYTHIA is introduced through a parameter called reconnection range (RR). In the default PYTHIA Monash model RR is taken to be equal to 1.8. To investigate the effect of color reconnection in our scaled factorial moment estimation in

From the above observation, it is evident that color reconnection plays a significant role in the observed intermittency in the PYTHIA Monash (default) generated data set at

The

The anomalous dimension

Variation of (a)

The intermittent pattern in the emission spectra of the primary charged particles produced in high-multiplicity

Variation of intermittency index

The authors thank Prof. Rudolph C. Hwa of the University of Oregon for his valuable comments and careful reading of the manuscript. P.S. thanks his colleague Nur Hussain for providing help in generating PYTHIA events. The authors thankfully acknowledge the Department of Science and Technology (DST), Government of India, for providing funds via Project No. SR/MF/PS-01/2014-GU(C) to develop a high-performance computing cluster (HPCC) facility for the generation of the Monte Carlo events for this work.