scholarly journals First measurements of N-subjettiness in central Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 2.76 TeV

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
◽  
S. Acharya ◽  
D. Adamová ◽  
A. Adler ◽  
J. Adolfsson ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Jet Substructure ◽  
Centre Of Mass ◽  
Pp Collisions ◽  
Coincidence Technique ◽  
Inclusive Jets ◽  
Ion Collisions ◽  
Using Data

Abstract The ALICE Collaboration reports the first fully-corrected measurements of the N-subjettiness observable for track-based jets in heavy-ion collisions. This study is performed using data recorded in pp and Pb-Pb collisions at centre-of-mass energies of $$ \sqrt{s} $$ s = 7 TeV and $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 2.76 TeV, respectively. In particular the ratio of 2-subjettiness to 1-subjettiness, τ2/τ1, which is sensitive to the rate of two-pronged jet substructure, is presented. Energy loss of jets traversing the strongly interacting medium in heavy-ion collisions is expected to change the rate of two-pronged substructure relative to vacuum. The results are presented for jets with a resolution parameter of R = 0.4 and charged jet transverse momentum of 40 ≤ pT,jet ≤ 60 GeV/c, which constitute a larger jet resolution and lower jet transverse momentum interval than previous measurements in heavy-ion collisions. This has been achieved by utilising a semi-inclusive hadron-jet coincidence technique to suppress the larger jet combinatorial background in this kinematic region. No significant modification of the τ2/τ1 observable for track-based jets in Pb-Pb collisions is observed relative to vacuum PYTHIA6 and PYTHIA8 references at the same collision energy. The measurements of τ2/τ1, together with the splitting aperture angle ∆R, are also performed in pp collisions at $$ \sqrt{s} $$ s = 7 TeV for inclusive jets. These results are compared with PYTHIA calculations at $$ \sqrt{s} $$ s = 7 TeV, in order to validate the model as a vacuum reference for the Pb-Pb centre-of-mass energy. The PYTHIA references for τ2/τ1 are shifted to larger values compared to the measurement in pp collisions. This hints at a reduction in the rate of two-pronged jets in Pb-Pb collisions compared to pp collisions.

scholarly journals Highlights from ATLAS

2018 ◽  
Vol 182 ◽  
pp. 02012
Author(s):  
L. Bellagamba
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
New Physics ◽  
Atlas Collaboration ◽  
Centre Of Mass ◽  
Mass Energy ◽  
Pp Collisions ◽  
Ion Collisions

This report presents an overview of some of the most recent results obtained by the ATLAS Collaboration using pp and heavy-ion collisions at the LHC. The review is not intended to be comprehensive and includes recent updates on the Higgs boson properties, precision Standard Model measurements, as well as searches for new physics. Most of the results exploit the data collected in the last LHC run, providing pp collisions at a centre of mass energy of 13 TeV.

scholarly journals Energy and multiplicity dependence of hadronic resonance production with ALICE at the LHC

2020 ◽  
Vol 1643 (1) ◽  
pp. 012007
Author(s):  
Angela Badalà
Keyword(s):  
Transverse Momentum ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Pp Collisions ◽  
Alice Experiment ◽  
Ion Collisions ◽  
Scattering Effects ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Hadronic Resonances

Abstract The study of hadronic resonances plays an important role both in pp and in heavy-ion collisions. Since the lifetimes of short-lived resonances are comparable with the lifetime of the fireball formed in heavy-ion collisions, regeneration and re-scattering effects can modify the measured yields, especially at low transverse momentum. Measurements in pp collisions at different energies constitute a baseline for studies in heavy-ion collisions and provide constraints for tuning QCD-inspired event generators. Furthermore, high multiplicity pp collisions, where the density and the volume of the system are expected to be larger compared to minimum bias pp collisions, can help in the search for the onset of collective phenomena. Here we present recent results on short-lived hadronic resonances obtained by the ALICE experiment at LHC energies in different collision systems (pp, p–Pb and Pb–Pb) including new results obtained in Xe–Xe collisions. The ALICE results on transverse momentum spectra, yields and their ratios to long-lived particles will be discussed.

scholarly journals Vector boson tagged jets and jet substructure

2018 ◽  
Vol 172 ◽  
pp. 05006
Author(s):  
Ivan Vitev
Keyword(s):  
Transverse Momentum ◽  
Heavy Ion Collisions ◽  
Vector Boson ◽  
Heavy Ion ◽  
Gluon Plasma ◽  
Jet Substructure ◽  
Proton Proton ◽  
Jet Production ◽  
Ion Collisions ◽  
Jet Shapes

In these proceedings, we report on recent results related to vector boson-tagged jet production in heavy ion collisions and the related modification of jet substructure, such as jet shapes and jet momentum sharing distributions. Z0-tagging and γ-tagging of jets provides new opportunities to study parton shower formation and propagation in the quark-gluon plasma and has been argued to provide tight constrains on the energy loss of reconstructed jets. We present theoretical predictions for isolated photon-tagged and electroweak boson-tagged jet production in Pb+Pb collisions at √sNN = 5.02 TeV at the LHC, addressing the modification of their transverse momentum and transverse momentum imbalance distributions. Comparison to recent ATLAS and CMS experimental measurements is performed that can shed light on the medium-induced radiative corrections and energy dissipation due to collisional processes of predominantly quark-initiated jets. The modification of parton splitting functions in the QGP further implies that the substructure of jets in heavy ion collisions may differ significantly from the corresponding substructure in proton-proton collisions. Two such observables and the implication of tagging on their evaluation is also discussed.

scholarly journals Skewness of mean transverse momentum fluctuations in heavy-ion collisions

2021 ◽  
Vol 103 (2) ◽  
Author(s):  
Giuliano Giacalone ◽  
Fernando G. Gardim ◽  
Jacquelyn Noronha-Hostler ◽  
Jean-Yves Ollitrault
Keyword(s):  
Transverse Momentum ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Ion Collisions

scholarly journals Initial transverse-momentum broadening of Breit-Wheeler process in relativistic heavy-ion collisions

2020 ◽  
Vol 800 ◽  
pp. 135089 ◽  
Author(s):  
Wangmei Zha ◽  
James Daniel Brandenburg ◽  
Zebo Tang ◽  
Zhangbu Xu
Keyword(s):  
Transverse Momentum ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Relativistic Heavy Ion Collisions ◽  
Ion Collisions

scholarly journals Quarkonium measurements in heavy-ion collisions with the STAR experiment

2018 ◽  
Vol 171 ◽  
pp. 18015
Author(s):  
Xinjie Huang
Keyword(s):  
Transverse Momentum ◽  
Nuclear Matter ◽  
Heavy Ion Collisions ◽  
Theoretical Calculations ◽  
Heavy Ion ◽  
Matter Effects ◽  
Nuclear Modification ◽  
Ion Collisions ◽  
Star Experiment ◽  
Nuclear Modification Factors

In these proceedings, we present the latest measurements of J/ψ and ϒ by the STAR experiment. The J/ψ and ϒ production measured in p+p collisions provide new baselines for similar measurements in Au+Au collisions, while the measurements in p+Au collisions can help quantify the cold nuclear matter effects. The J/ψ υ2 is measured in both U+U and Au+Au collisions to place constraints on the amount of J/ψ arising from recombination of deconfined charm and anti-charm pairs. Furthermore, the nuclear modification factors for ground and excited ϒ states as a function of transverse momentum and centrality are presented, and compared to those measured at the LHC as well as to theoretical calculations.

scholarly journals Transverse momentum dependent decorrelation in Pb–Pb collisions at LHC

2020 ◽  
Vol 29 (08) ◽  
pp. 2050057
Author(s):  
De-Xian Wei
Keyword(s):  
Transverse Momentum ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Transverse Momentum Dependent ◽  
Model Simulations ◽  
Ion Collisions ◽  
Difference Formula ◽  
Multi Phase ◽  
Phase Transport ◽  
Different Order

Based on A Multi-Phase Transport (AMPT) model simulations, the transverse momentum dependent decorrelation has been studied in Pb–Pb collisions at [Formula: see text] and 5.02 TeV, respectively. It has been found that the mix-order factorization ratio [Formula: see text] value deviates significantly from unity in noncentral collisions. Such effect becomes stronger with an increase in the [Formula: see text] difference [Formula: see text]. These decorrelations are not only between the same order harmonic but also between the different order harmonic, which as a result of the initial fluctuations appear between the different phase spaces. It has also been found that the correlations involving higher powers of the flow vector yield stronger decorrelation, [Formula: see text], except for the weighted factorization ratio [Formula: see text]. The breaking phenomenon of these factorization ratios indicated that it provides a possible observation for studying the initial fluctuation properties of heavy-ion collisions.

RAPIDITY AND AZIMUTHAL CORRELATION PATTERNS IN NUCLEON-NUCLEON AND RELATIVISTIC HEAVY ION COLLISIONS AT $\sqrt{s} = 200\, {\rm GeV}$

2007 ◽  
Vol 16 (10) ◽  
pp. 3379-3385 ◽  
Author(s):  
MEIJUAN WANG ◽  
YUANFANG WU
Keyword(s):  
Heavy Ion Collisions ◽  
System Size ◽  
Heavy Ion ◽  
Nucleon Nucleon ◽  
Relativistic Heavy Ion Collisions ◽  
Production Mechanism ◽  
Azimuthal Correlation ◽  
Pp Collisions ◽  
Ion Collisions

Rapidity and azimuthal correlation patterns for nucleon and relativistic heavy ion collisions are systematically studied by using PYTHIA for pp collisions, RQMD and AMPT for Au − Au collisions at [Formula: see text], respectively. The results show that the measures are sensitive to the collision particles, system size and production mechanism of the system.

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