scholarly journals Probing the interaction of semi-hard quarks and gluons with the underlying event in light- and heavy-flavor triggered proton-proton collisions

2021 ◽  
Vol 57 (10) ◽  
Author(s):  
Róbert Vértesi ◽  
Gyula Bencédi ◽  
Anett Misák ◽  
Antonio Ortiz
Keyword(s):  
B Mesons ◽  
String Model ◽  
Event Generator ◽  
Heavy Flavor ◽  
Underlying Event ◽  
Proton Proton ◽  
B Hadrons ◽  
Leading Particle ◽  
Quark Jets ◽  
Color Reconnection

AbstractWe study underlying-event observables in inelastic proton-proton (pp) collisions at a centre-of-mass energy of $$\sqrt{s} = 13$$ s = 13  TeV with identified light and heavy-flavor triggers using the PYTHIA  8 event generator. The study is performed as a function of the transverse momentum of the leading particle ($$p_\mathrm {T}^\mathrm{trigger}$$ p T trigger ). While at high $$p_\mathrm {T}^\mathrm{trigger}$$ p T trigger ($$>10$$ > 10  GeV/c) the underlying-event activity is independent of the leading particle species, at intermediate $$p_\mathrm {T}^\mathrm{trigger}$$ p T trigger ($$2<p_\mathrm {T}^\mathrm{trigger} <8$$ 2 < p T trigger < 8  GeV/c) it is larger in pion-triggered events than in events triggered with B mesons. Moreover, the underlying event in pion-triggered events, the majority of which are initiated by gluons, shows a stronger effect of color reconnection than events triggered with B-hadrons, that are mostly initiated by quark jets. The effect is observed at both hadronic and partonic level. Given that color reconnection affects the interaction among final partons before the hadronization, and that in the string model quarks (gluons) are connected to one (two) string piece(s), we conclude that the observed effect can be attributed to differences in the interactions of gluon and quark jets with the underlying event.

scholarly journals Forward backward multiplicity correlations: a tool to study properties of the proton-proton collisions

2018 ◽  
Vol 172 ◽  
pp. 05008 ◽  
Author(s):  
Edgar Dominguez-Rosas ◽  
Eleazar Cuautle Flores
Keyword(s):  
Experimental Data ◽  
Hadron Production ◽  
Event Generator ◽  
Proton Proton ◽  
Proton Collisions ◽  
Electron Positron ◽  
Color Reconnection ◽  
Proton Proton Collisions ◽  
Production Mechanisms ◽  
Reconnection Model

Forward-backward multiplicity correlations have been used to study hadron production mechanisms in electron-positron, proton-proton and more recently in leadlead collisions. The experimental results on this correlations and its comparison to different models reveals an incomplete agreement. In this work, we present an study of forward backward multiplicity correlations in proton-proton collisions using PYTHIA event generator, at LHC energies. Detailed analysis is presented in the case of soft and hard QCD processes, incorporating color reconnection model as part of hadronization mechanism and multiple parton interactions effects in the correlations. Our results and its comparison to available experimental data suggest that this kind of correlations are great tools to characterize the events and gives the possibility to disentangle phenomena in hard and soft QCD processes.

scholarly journals Development and validation of HERWIG 7 tunes from CMS underlying-event measurements

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
F. Ambrogi ◽  
...  
Keyword(s):  
Top Quark ◽  
W Boson ◽  
Parton Distribution Function ◽  
Event Generator ◽  
Event Shape ◽  
Minimum Bias ◽  
Leading Order ◽  
Underlying Event ◽  
Proton Proton ◽  
Positron Collisions

AbstractThis paper presents new sets of parameters (“tunes”) for the underlying-event model of the $${\textsc {herwig}} \,7$$ H E R W I G 7 event generator. These parameters control the description of multiple-parton interactions (MPI) and colour reconnection in $${\textsc {herwig}} \,7$$ H E R W I G 7 , and are obtained from a fit to minimum-bias data collected by the CMS experiment at $$\sqrt{s}=0.9$$ s = 0.9 , 7, and $$13 \,\text {Te}\text {V} $$ 13 Te . The tunes are based on the NNPDF 3.1 next-to-next-to-leading-order parton distribution function (PDF) set for the parton shower, and either a leading-order or next-to-next-to-leading-order PDF set for the simulation of MPI and the beam remnants. Predictions utilizing the tunes are produced for event shape observables in electron-positron collisions, and for minimum-bias, inclusive jet, top quark pair, and Z and W boson events in proton-proton collisions, and are compared with data. Each of the new tunes describes the data at a reasonable level, and the tunes using a leading-order PDF for the simulation of MPI provide the best description of the data.

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

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
Prabhakar Palni ◽  
Arvind Khuntia ◽  
Paolo Bartalini
Keyword(s):  
Hadron Production ◽  
Underlying Event ◽  
Proton Proton ◽  
Proton Collisions ◽  
Particle Ratios ◽  
Strange Hadron ◽  
Relative Production ◽  
Color Reconnection ◽  
Proton Proton Collisions ◽  
Insight Into

AbstractIn this work, the relative Underlying event (UE) transverse multiplicity activity classifier ($$R_\mathrm{{T}}$$ R T ) is used to study the strange and multi-strange hadron production in proton-proton collisions. Our study with $$R_\mathrm{{T}}$$ R T 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 $$\sqrt{s}~$$ s = 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 $$R_\mathrm{{T}}$$ R T . This enhancement is significant for the strange baryons as compared to mesons. In addition, the particle ratios as a function of $$R_\mathrm{{T}}~$$ R T 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.

scholarly journals Effect of color reconnection and rope formation on resonance production in p–p collisions in Pythia 8

2021 ◽  
Vol 81 (11) ◽  
Author(s):  
Ankita Goswami ◽  
Ranjit Nayak ◽  
Basanta Kumar Nandi ◽  
Sadhana Dash
Keyword(s):  
Gluon Plasma ◽  
Event Generator ◽  
Particle Multiplicity ◽  
Charged Particle Multiplicity ◽  
Resonance Production ◽  
Proton Proton ◽  
Strange Quarks ◽  
Enhanced Production ◽  
Color Reconnection ◽  
Proton Proton Collisions

AbstractResonance production in proton–proton collisions at $$\sqrt{s} = 7$$ s = 7 TeV and 13 TeV have been investigated using a Pythia 8 event generator within the framework of microscopic processes including color reconnection and rope hadronization. Specifically, the observable effects of different modes of color reconnections on the ratio of yields of mesonic and baryonic resonances with respect to their stable counterpart have been explored as a function of mean charged particle multiplicity. A suppression in the ratio is observed as a function of the mean number of charged particles for mesonic resonances. The $$\phi /\mathrm {K}$$ ϕ / K and $${\phi /\pi }$$ ϕ / π ratios show an enhancement for high-multiplicity events due to enhanced production of strange quarks via the microscopic process of rope hadronization in the partonic phase. The mechanism of the hadronization of color ropes together with the quark–gluon plasma (QCD)-based color reconnection of partons predicted an enhancement in the ratio for baryonic resonances to non-resonance baryons having similar quark content. The yield ratios of resonances are found to be independent of the collision energy and strongly dependent on event activity.

scholarly journals Soft-drop grooming for hadronic event shapes

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Jeremy Baron ◽  
Daniel Reichelt ◽  
Steffen Schumann ◽  
Niklas Schwanemann ◽  
Vincent Theeuwes
Keyword(s):  
Event Generator ◽  
Experimental Measurements ◽  
Event Shape ◽  
Matrix Elements ◽  
Underlying Event ◽  
Hadronic Event ◽  
Wide Range ◽  
Event Shapes ◽  
The Impact ◽  
Perturbative Corrections

Abstract Soft-drop grooming of hadron-collision final states has the potential to significantly reduce the impact of non-perturbative corrections, and in particular the underlying-event contribution. This eventually will enable a more direct comparison of accurate perturbative predictions with experimental measurements. In this study we consider soft-drop groomed dijet event shapes. We derive general results needed to perform the resummation of suitable event-shape variables to next-to-leading logarithmic (NLL) accuracy matched to exact next-to-leading order (NLO) QCD matrix elements. We compile predictions for the transverse-thrust shape accurate to NLO + NLL′ using the implementation of the Caesar formalism in the Sherpa event generator framework. We complement this by state-of-the-art parton- and hadron-level predictions based on NLO QCD matrix elements matched with parton showers. We explore the potential to mitigate non-perturbative corrections for particle-level and track-based measurements of transverse thrust by considering a wide range of soft-drop parameters. We find that soft-drop grooming indeed is very efficient in removing the underlying event. This motivates future experimental measurements to be compared to precise QCD predictions and employed to constrain non-perturbative models in Monte-Carlo simulations.

scholarly journals Dielectron Production in Proton–Proton Collisions at √s=7 TeV with ALICE

Proceedings ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 24
Author(s):  
Sebastian Scheid
Keyword(s):  
Cross Sections ◽  
Mass Range ◽  
Heavy Ion ◽  
Event Generator ◽  
Leading Order ◽  
Proton Proton ◽  
Total Cross Sections ◽  
Proton Collisions ◽  
Ion Collisions ◽  
Proton Proton Collisions

The ALICE Collaboration measured dielectron production as a function of the invariant mass ( m ee ), the pair transverse momentum ( p T , ee ) and the pair distance of closest approach ( DCA ee ) in pp collisions at s = 7 TeV. Prompt and non-prompt dielectron sources can be separated with the DCA ee , which will give the opportunity in heavy-ion collisions to identify thermal radiation from the medium in the intermediate-mass range dominated by contributions from open-charm and beauty hadron decays. The charm and beauty total cross sections are extracted from the data by fitting the spectra with two different MC generators, i.e., PYTHIA a leading order event generator and POWHEG a next-to-leading order event generator. Significant model dependences are observed, reflecting the sensitivity of this measurement to the heavy-flavour production mechanisms.

Baryon production at LHC experiments: average pt of hyperons versus energy

2020 ◽  
Vol 35 (13) ◽  
pp. 2050067
Author(s):  
Olga I. Piskounova
Keyword(s):  
Cosmic Ray ◽  
String Model ◽  
Baryon Production ◽  
Proton Antiproton ◽  
Proton Proton ◽  
Low Energies ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
The Difference ◽  
Proton Proton Collisions

This paper examines the transverse momentum spectra of baryons in the multiparticle production at modern colliders in the frameworks of Quark–Gluon String Model (QGSM). It discusses: (i) the difference in [Formula: see text] hyperon spectra at proton–antiproton versus proton–proton reactions on previous colliders; (ii) the difference in hyperon spectra between the experiments on colliders of low energies and the results from modern machines; (iii) the growth of average transverse momenta of [Formula: see text] hyperon with the energies of proton–proton collisions up to [Formula: see text] TeV of LHC experiments. This analysis of baryon spectra led to the following conclusions. First, the fragmentation of antidiquark–diquark side of one-pomeron diagram makes the major contribution to baryon production spectra in the asymmetric [Formula: see text] reaction. Second, the average [Formula: see text]’s of hyperons in [Formula: see text] collisions steadily grow with energy in the range from [Formula: see text] GeV to 7 TeV. The additional conclusion is the following: since no dramatic changes have been seen in the characteristics of baryon production, the hadroproduction processes do not cause the “knee” in the cosmic ray proton spectra at the energies between Tevatron collider and LHC.

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