THE ALICE EXPERIMENT AT CERN LHC: STATUS AND FIRST RESULTS

2011 ◽  
Vol 26 (03n04) ◽  
pp. 517-522
Author(s):  
◽  
ERMANNO VERCELLIN
Keyword(s):  
Data Analysis ◽  
Cosmic Rays ◽  
Dense Matter ◽  
Heavy Ion ◽  
Short Description ◽  
Alice Experiment ◽  
Ion Collisions ◽  
Physics Program ◽  
Accelerate Proton ◽  
First Results

The ALICE experiment is aimed at studying the properties of the hot and dense matter produced in heavy-ion collisions at LHC energies. In the first years of LHC operation the ALICE physics program will be focused on Pb - Pb and p - p collisions. The latter, on top of their intrinsic interest, will provide the necessary baseline for heavy-ion data. After its installation and a long commissioning with cosmic rays, in late fall 2009 ALICE participated (very successfully) in the first LHC run, by collecting data in p - p collisions at c.m. energy 900 GeV. After a short stop during winter, LHC operations have been resumed; the machine is now able to accelerate proton beams up to 3.5 TeV and ALICE has undertaken the data taking campaign at 7 TeV c.m. energy. After an overview of the ALICE physics goals and a short description of the detector layout, the ALICE performance in p - p collisions will be presented. The main physics results achieved so far will be highlighted as well as the main aspects of the ongoing data analysis.

scholarly journals JET AND HIGH PT MEASUREMENTS WITH THE ALICE EXPERIMENT

2011 ◽  
Vol 20 (07) ◽  
pp. 1533-1538
Author(s):  
◽  
CHRISTIAN KLEIN-BÖSING
Keyword(s):  
Particle Production ◽  
Center Of Mass ◽  
Heavy Ion ◽  
First Year ◽  
Alice Experiment ◽  
Elementary Reactions ◽  
Ion Collisions ◽  
New Energy ◽  
First Results ◽  
Medium Influence

Since the beginning of 2010 the LHC provides p + p collisions at the highest center of mass energies to date, allowing to study high p T particle production and jet properties in a new energy regime. For a clear interpretation and the quantification of the medium influence in heavy-ion collisions on high p T observables a detailed understanding of these elementary reactions is essential. We present first results on the observation of jet-like properties with the ALICE experiment and discuss the performance of jet reconstruction in the first year of data taking.

CHARMONIUM PRODUCTION IN Pb–Pb COLLISIONS AT ALICE: FROM SUPPRESSION TO REGENERATION?

2013 ◽  
Vol 28 (21) ◽  
pp. 1330018 ◽  
Author(s):  
ENRICO SCOMPARIN
Keyword(s):  
Phase Transition ◽  
Cross Sections ◽  
Short Review ◽  
Heavy Ion ◽  
Gluon Plasma ◽  
Alice Experiment ◽  
Model Calculations ◽  
Ion Collisions ◽  
Quark Production ◽  
History Of

Heavy quarkonium states are considered as one of the key observables for the study of the phase transition from a system made of hadrons towards a Quark–Gluon Plasma (QGP). In the last 25 years, experiments at CERN and Brookhaven have studied collisions of heavy ions looking for a suppression of charmonia/bottomonia, considered as a signature of the phase transition. After an introduction to the main concepts behind these studies and a short review of the SPS and RHIC results, I will describe the results obtained in Pb – Pb collisions by the ALICE experiment at the LHC. The ALICE findings will be critically compared to those of lower energy experiments, to CMS results, and to model calculations. The large cross-sections for heavy-quark production at LHC energies are expected to induce a novel production mechanism for charmonia in heavy-ion collisions, related to a recombination of [Formula: see text] pairs along the history of the collision and/or at hadronization. The occurrence of such a process at the LHC will be discussed. Finally, prospects for future measurements will be shortly addressed.

scholarly journals Kaon production from hot and dense matter formed in heavy-ion collisions

1991 ◽  
Vol 43 (4) ◽  
pp. 1881-1892 ◽  
Author(s):  
G. E. Brown ◽  
C. M. Ko ◽  
Z. G. Wu ◽  
L. H. Xia
Keyword(s):  
Heavy Ion Collisions ◽  
Dense Matter ◽  
Heavy Ion ◽  
Kaon Production ◽  
Ion Collisions

FRACTALS AND THE QUANTUM THEORY OF SPACETIME

1989 ◽  
Vol 04 (19) ◽  
pp. 5047-5117 ◽  
Author(s):  
LAURENT NOTTALE
Keyword(s):  
Fractal Dimension ◽  
Heavy Ion ◽  
Space Time ◽  
Curvilinear Coordinates ◽  
Fractal Structures ◽  
Ion Collisions ◽  
Principle Of Relativity ◽  
First Results ◽  
Fractal Space ◽  
Dimension 2

We review in this paper the first results obtained in an attempt at understanding quantum space-time based on a new extension of the principle of relativity and on the geometrical concept of fractals. We present methods for dealing with the nondifferentiability and the infinities of fractals, as a first step towards the definition and intrinsic description of a fractal space. After having recalled that the Heisenberg relations imply a transition of spatial coordinates of a particle to fractal dimension 2 about the de Broglie length λ = ħ/p, it is suggested that a similar transition occurs for temporal coordinates about the de Broglie time τ = ħ/E. We then investigate the hypothesis that the microstructure of space-time is of fractal nature, and that the observed properties of the quantum world at a given resolution result from the smoothing of curvilinear coordinates of such a spacetime projected into classical spacetime. Along this road, we successively study the link of fractal dimension 2 to spin, we give first hints on the expected behavior of families of fractal geodesics, and we exhibit a general class of fractal structures which is assumed to yield a lowest order description of the quantum vacuum. The links between the new approach and both special and general relativity are touched upon. We finally suggest that the anomalous peaks recently observed in the spectra of positrons from supercritical heavy ion collisions may be understood in this context.

scholarly journals Apparent and Actual Shifts in Mass and Width of ϕ Mesons Produced in Heavy-Ion Collisions

1997 ◽  
Vol 12 (02) ◽  
pp. 127-134 ◽  
Author(s):  
R. S. Bhalerao ◽  
S. K. Gupta
Keyword(s):  
Invariant Mass ◽  
Preliminary Data ◽  
Heavy Ion Collisions ◽  
Mass Spectra ◽  
Dense Matter ◽  
Heavy Ion ◽  
High Energy ◽  
Mass Shift ◽  
Ion Collisions ◽  
Invariant Mass Spectra

We present a method of analyzing invariant-mass spectra of kaon pairs resulting from decay of ϕ mesons produced in high-energy heavy-ion collisions. It can be used to extract the shifts in the mass and the width (ΔM and ΔΓ) of the ϕ mesons when they are inside the dense matter formed in these collisions. We illustrate our method with the help of available preliminary data. Extracted values of ΔM and ΔΓ are significantly larger than those obtained with an earlier method. Our results are consistent with the experimentally observed pT dependence of the mass shift. Finally, we present a phenomenological relation between ΔM and ΔΓ. It provides a useful constraint on theories which predict the values of these two quantities.

Sudden increase in the degrees of freedom in dense QCD matter

2021 ◽  
Author(s):  
Aditya Nath Mishra ◽  
Guy Paić ◽  
C. Pajares ◽  
R. P. Scharenberg ◽  
B. K. Srivastava
Keyword(s):  
Charged Particle ◽  
Energy Density ◽  
Heavy Ion Collisions ◽  
Degrees Of Freedom ◽  
Initial Temperature ◽  
Heavy Ion ◽  
Particle Multiplicity ◽  
Sudden Increase ◽  
Alice Experiment ◽  
Ion Collisions

In this paper, we analyzed charged particle transverse momentum spectra in high multiplicity events in proton–proton and nucleus–nucleus collisions at LHC energies from the ALICE experiment using the color string percolation model (CSPM). The color reduction factor and associated string density parameters are extracted for various multiplicity classes in [Formula: see text] collisions and centrality classes for heavy-ion collisions at various LHC energies to study the effect of collision geometry and collision energy. These parameters are used to extract the thermodynamical quantities temperature and the energy density of the hot nuclear matter. A universal scaling is observed in initial temperature when studied as a function of charged particle multiplicity scaled by transverse overlap area. From the measured initial energy density [Formula: see text] and the initial temperature T, a dimensionless quantity [Formula: see text] is constructed which is used to obtain the degrees of freedom (DOF) of the deconfined phase. A two-step behavior and a sudden increase in DOF of [Formula: see text]47 for the ideal gas, above the hadronization temperature (T [Formula: see text] 210[Formula: see text]MeV), are observed in case of heavy-ion collisions at LHC energies.

scholarly journals Correlation of Heavy and Light Flavors in Simulations

Universe ◽  
2019 ◽  
Vol 5 (5) ◽  
pp. 118
Author(s):  
Eszter Frajna ◽  
Róbert Vértesi
Keyword(s):  
Large Hadron Collider ◽  
Heavy Ion Collisions ◽  
Hadron Collider ◽  
D Meson ◽  
Heavy Ion ◽  
High Energy ◽  
Secondary Vertex ◽  
Alice Experiment ◽  
Ion Collisions ◽  
B Quarks

The ALICE experiment at the Large Hadron Collider (LHC) ring is designed to study the strongly interacting matter at extreme energy densities created in high-energy heavy-ion collisions. In this paper we investigate correlations of heavy and light flavors in simulations at LHC energies at mid-rapidity, with the primary purpose of proposing experimental applications of these methods. Our studies have shown that investigating the correlation images can aid the experimental separation of heavy quarks and help understanding the physics that create them. The shape of the correlation peaks can be used to separate the electrons stemming from b quarks. This could be a method of identification that, combined with identification in silicon vertex detectors, may provide much better sample purity for examining the secondary vertex shift. Based on a correlation picture it is also possible to distinguish between prompt and late contributions to D meson yields.

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