Event classifiers based either on the charged-particle multiplicity or the event shape have been extensively used in proton-proton (<math><mi>p</mi><mi>p</mi></math>) collisions by the ALICE Collaboration at the LHC. The use of these tools became very instrumental since the observation of fluidlike behavior in high-multiplicity <math><mi>p</mi><mi>p</mi></math> collisions. In particular, the study as a function of the charged-particle multiplicity registered in the forward V0 ALICE detector allowed for the discovery of strangeness enhancement in high-multiplicity <math><mi>p</mi><mi>p</mi></math> collisions. However, one drawback of the multiplicity-based event classifiers is that requiring a high charged-particle multiplicity biases the sample towards hard processes like multijet final states. These biases make it difficult to perform jet-quenching searches in high-multiplicity <math><mi>p</mi><mi>p</mi></math> collisions. In this context, the present paper explores the use of the new event classifier, flattenicity; which uses the multiplicity calculated in the forward pseudorapidity region. To illustrate how this tool works, pp collisions at <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13.6</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> simulated with pythia 8 are explored. The sensitivity of flattencity to multipartonic interactions as well as to the “hardness” of the collision are discussed. pythia 8 predictions for the transverse momentum spectra of light- and heavy-flavored hadrons as a function of flattenicity are presented.

CERN

Antonio Ortiz

Czechia

Arvind Khuntia

United States

Omar Vázquez Rueda

Italy

Sushanta Tripathy

Hungary

Gyula Bencédi

India

Suraj Prasad

China

Feng Fan

Unveiling the effects of multiple soft partonic interactions in <math><mi>p</mi><mi>p</mi></math> collisions at <math><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>13.6</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math> using a new event classifier

Recent observations of QGP-like conditions in high-multiplicity pp collisions from ALICE experiment at the LHC warrant an introspection whether to use pp collisions as a baseline measurement to characterize heavy-ion collisions for the possible formation of a Quark-Gluon Plasma. A double differential study of the particle spectra and thermodynamics of the produced system as a function of charged-particle multiplicity and transverse spherocity in pp collisions would shed light on the underlying event dynamics. Transverse spherocity, one of the event shape observables, allows to separate the events in terms of jetty and isotropic events. We analyse the identified particle transverse momentum (<math id="M2"><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></math>) spectra as a function of charged-particle multiplicity and transverse spherocity using Tsallis nonextensive statistics and Boltzmann-Gibbs Blast-Wave (BGBW) model in pp collisions at <math id="M3"><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext>TeV</mtext></math> using PYTHIA8 event generator. The extracted parameters such as temperature (<math id="M4"><mi>T</mi></math>), radial flow (<math id="M5"><mi>β</mi></math>), and nonextensive parameter (<math id="M6"><mi>q</mi></math>) are shown as a function of charged-particle multiplicity for different spherocity classes. We observe that the isotropic events approach thermal equilibrium while the jetty ones remain far from equilibrium. We argue that, while studying the QGP-like conditions in small systems, one should separate the isotropic events from the spherocity-integrated events, as the production dynamics are different.

Raghunath Sahoo

Ashish Bisht

Poland

Malavika Panikkassery Salvan

Event Shape and Multiplicity Dependence of Freeze-Out Scenario and System Thermodynamics in Proton+Proton Collisions at Using PYTHIA8

In this work, the relative Underlying event (UE) transverse multiplicity activity classifier ( $$R_\mathrm{{T}}$$  <math> <msub> <mi>R</mi> <mi>T</mi> </msub> </math>  ) is used to study the strange and multi-strange hadron production in proton-proton collisions. Our study with  $$R_\mathrm{{T}}$$  <math> <msub> <mi>R</mi> <mi>T</mi> </msub> </math>   would allow to disentangle these particles, which are originating from the soft and hard QCD processes. We have used the PYTHIA 8 Monte-Carlo (MC) with a different implementation of color reconnection and rope hadronization models to demonstrate the proton-proton collisions data at  $$\sqrt{s}~$$  <math> <mrow> <msqrt> <mi>s</mi> </msqrt> <mspace width="3.33333pt"></mspace> </mrow> </math>  = 13 TeV. The relative production of strange and multi-strange hadrons are discussed extensively in low and high transverse activity regions. In this contribution, the relative strange hadron production is enhanced with increasing  $$R_\mathrm{{T}}$$  <math> <msub> <mi>R</mi> <mi>T</mi> </msub> </math>  . This enhancement is significant for the strange baryons as compared to mesons. In addition, the particle ratios as a function of  $$R_\mathrm{{T}}~$$  <math> <mrow> <msub> <mi>R</mi> <mi>T</mi> </msub> <mspace width="3.33333pt"></mspace> </mrow> </math>  confirm the baryon enhancement in new Color Reconnection (newCR), whereas the Rope model confirms the baryon enhancement only with strange quark content. Experimental confirmation of such results will provide more insight into the soft physics in the transverse region, which will be useful to investigate various tunes based on hadronization and color reconnection schemes.

Prabhakar Palni

Mexico

Paolo Bartalini

Evolution of strange and multi-strange hadron production with relative transverse multiplicity activity in underlying event

In this work, we have studied the isothermal compressibility (<math><msub><mi>κ</mi><mi>T</mi></msub></math>) as a function of temperature, baryon chemical potential, and center-of-mass energy (<math><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt></math>) using hadron resonance gas (HRG) and excluded-volume hadron resonance gas (EV-HRG) models. A mass cut-off dependence of isothermal compressibility has been studied for a physical resonance gas. Further, we study the effect of heavier resonances (<math><mrow><mo>&gt;</mo><mn>2</mn><mspace width="0.16em"></mspace><mi>GeV</mi></mrow></math>) on the isothermal compressibility by considering the Hagedorn mass spectrum, <math><mrow><mi>ρ</mi><mrow><mo>(</mo><mi>m</mi><mo>)</mo></mrow><mo>∼</mo><mrow><mo>exp</mo><mo>(</mo><mi>b</mi><mi>m</mi><mo>)</mo></mrow><mo>/</mo><msup><mrow><mo>(</mo><msup><mi>m</mi><mn>2</mn></msup><mo>+</mo><msubsup><mi>m</mi><mn>0</mn><mn>2</mn></msubsup><mo>)</mo></mrow><mrow><mn>5</mn><mo>/</mo><mn>4</mn></mrow></msup></mrow></math>. Here the parameters <math><mi>b</mi></math> and <math><msub><mi>m</mi><mn>0</mn></msub></math> are extracted after comparing the results of recent lattice QCD simulations at finite baryonic chemical potential. We find a significant difference between the results obtained in EV-HRG and HRG models at higher temperatures. The inclusion of the Hagedorn mass spectrum in the partition function for hadron gas has a large effect at a higher temperature. A higher mass cut-off in the Hagedorn mass spectrum takes the isothermal compressibility to a minimum value, which occurs near the Hagedorn temperature (<math><msub><mi>T</mi><mi>H</mi></msub></math>). We show explicitly that at the future low-energy accelerator facilities like FAIR (CBM), Darmstadt, and NICA, Dubna, the created matter would have higher compressibility compared to the high-energy facilities like the Relativistic Heavy Ion Collider and Large Hadron Collider.

Swatantra Kumar Tiwari

Pramod Sharma

Tapan K. Nayak

Effect of Hagedorn states on isothermal compressibility of hadronic matter formed in heavy-ion collisions: From NICA to LHC energies