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Author: Mahmoud Rateb Publisher: ISBN: Category : Anisotropy Languages : en Pages : 0
Book Description
Abstract: Anisotropic flow in high energy heavy-ion collisions is taken as a key evidence for the formation of QGP for brief seconds right after the collisions. Hydrodynamic models including QGP formation are accurate at predicting the azimuthal anisotropy of the produced particles at low transverse momenta. At high momenta however, hydrodynamic models predict no azimuthal anisotropy for particles of different masses and quark-flavors; the logic being that because of their high momenta, the particles pass through the media without having any time to have any reactivity. This is contrary to results from experiments where measurements of particles of different quark flavors show non-zero elliptic flow. To study this deviation, we run PYTHIA simulation of proton-proton collisions at center- of-mass energies equivalent to those at RHIC and LHC; 200 GeV and 13 TeV. Since in PYTHIA simulations no QGP if formed, and there is no final-state interaction, results in our simulation would act as probes to be compared to the results of elliptic flow from real experiments. Our results showed non-zero results for the elliptic flow of pions, heavy mesons and direct photons. Those results are evident of the possible bias in the way the reaction plane is calculated, since all the other factors are controlled for in the PYTHIA simulations. To make up for this inherent bias, the results from PYTHIA should be subtracted from the results of elliptic flow in real experiments, to end up with unbiased results for elliptic flow from the different colliders.
Author: Mahmoud Rateb Publisher: ISBN: Category : Anisotropy Languages : en Pages : 0
Book Description
Abstract: Anisotropic flow in high energy heavy-ion collisions is taken as a key evidence for the formation of QGP for brief seconds right after the collisions. Hydrodynamic models including QGP formation are accurate at predicting the azimuthal anisotropy of the produced particles at low transverse momenta. At high momenta however, hydrodynamic models predict no azimuthal anisotropy for particles of different masses and quark-flavors; the logic being that because of their high momenta, the particles pass through the media without having any time to have any reactivity. This is contrary to results from experiments where measurements of particles of different quark flavors show non-zero elliptic flow. To study this deviation, we run PYTHIA simulation of proton-proton collisions at center- of-mass energies equivalent to those at RHIC and LHC; 200 GeV and 13 TeV. Since in PYTHIA simulations no QGP if formed, and there is no final-state interaction, results in our simulation would act as probes to be compared to the results of elliptic flow from real experiments. Our results showed non-zero results for the elliptic flow of pions, heavy mesons and direct photons. Those results are evident of the possible bias in the way the reaction plane is calculated, since all the other factors are controlled for in the PYTHIA simulations. To make up for this inherent bias, the results from PYTHIA should be subtracted from the results of elliptic flow in real experiments, to end up with unbiased results for elliptic flow from the different colliders.
Author: Fareha G. A. Atetalla Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
At the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL), Long Island, NY, the main goal of research into heavy-ion collisions has been to understand Quantum Chromo Dynamics (QCD) in conditions of extreme temperature and energy density. At ordinary temperatures, the quarks and gluons are confined within particles like protons and neutrons, but at very high temperatures and densities, a new deconfined phase of quarks and gluons is created. This new phase is known as Quark Gluon Plasma (QGP).Quarks with the quantum numbers "charm" and "bottom" are relatively massive and are produced only rarely, and this category is called heavy flavor. Heavy-flavor measurements deepen our understanding of the properties and nature of the excited QGP state. Heavy-flavor particles are unique probes for studies of the hot and dense QGP medium created in high-energy collisions, as they are produced early in the evolution of the collision.STAR (Solenoidal Tracker At RHIC) is now the last operational detector at the RHIC facility, and was constructed and is operated by a large international collaboration. The STAR collaboration is composed of 68 institutions from 14 countries, with a total of 743 collaborators. In 2014, STAR employed a new silicon pixel technology detector named the Heavy Flavor Tracker (HFT). The HFT has separate layers of silicon to guide tracks reconstructed in the main tracking detector of STAR (the Time Projection Chamber) down to a spatial resolution of around 30 [mu]m in the region near the center of STAR where the collisions occur, which allows particles with very short lifetimes (notably heavy flavor particles) to be identified.In this dissertation, I use the HFT to measure particles with the charm quantum number. This work also involves using a pair of calorimeter detectors at a polar angle of zero degrees to estimate the azimuthal angle of the reaction plane in each collision. About 2.2 billion collisions are in the dataset being studied. These measurements allow the azimuthal anisotropy (flow) of charmed particles to be studied. The results are compared to similar studies involving light quarks and the predictions of several theoretical models. My results show a surprisingly large first Fourier harmonic in the anisotropy for particles with charm compared with particles with lighter flavors (strange, up, down). Specifically, the signal for charm is about 30 times larger, and no model comes anywhere close to predicting this pattern.
Author: Vladimir Vladislavovich Anisovich Publisher: World Scientific ISBN: 9812794921 Category : Science Languages : en Pages : 547
Book Description
This is an updated version of the book published in 1985. QCD-motivated, it gives a detailed description of hadron structure and soft interactions in the additive quark model, where hadrons are regarded as composite systems of dressed quarks. In the past decade it has become clear that nonperturbative QCD, responsible for soft hadronic processes, may differ rather drastically from perturbative QCD. The understanding of nonperturbative QCD requires a detailed investigation of the experiments and the theoretical approaches. Bearing this in mind, the book has been rewritten paying special attention to the interplay of soft hadronic collisions and the quark model. It is at the crossroads of these domains that peculiar features of strong QCD reveal themselves. The book discusses constituent quarks, diquarks, the massive effective gluons and the problem of scalar isoscalar mesons. The quark-gluonium classification of meson states is also given. Experimentally observed properties of hadrons are presented together with the corresponding theoretical interpretation in the framework of the composite hadron structure. The text includes a large theoretical part, which shows how to treat composite systems (including relativistic ones) with a technique based on spectral integration. This technique provides the possibility of handling hadrons as weakly bound systems of quarks and, at the same time, takes into account confinement. Attention is focused on the composite structure revealing itself in high energy hadron collisions. Fields of applicability of the additive quark model are discussed, as is colour screening in hadronic collisions at high and superhigh energies. Along with a detailed presentation of hadronOCohadron collisions, a description of hadronOConucleus collisions is given. Sample Chapter(s). Chapter 1: Introduction (1,047 KB). Contents: High Energy Hadron Interactions; Composite Systems; High Energy Interactions of Composite Systems; Hadron Zoology and Static Features of Hadrons; Binary Processes in the Quark Model; Multiparticle Production in the Quark Model: Hadron Collisions at Moderately High Energies; HadronOCoNucleus Collisions. Readership: Graduate students and researchers in particle and nuclear physics."
Author: Nele Boelaert Publisher: Springer Science & Business Media ISBN: 3642245978 Category : Science Languages : en Pages : 176
Book Description
This thesis is based on the first data from the Large Hadron Collider (LHC) at CERN. Its theme can be described as the classical Rutherford scattering experiment adapted to the LHC: measurement of scattering angles to search for new physics and substructure. At the LHC, colliding quarks and gluons exit the proton collisions as collimated particle showers, or jets. The thesis presents studies of the scattering angles of these jets. It includes a phenomenological study at the LHC design energy of 14 TeV, where a model of so-called large extra dimensions is used as a benchmark process for the sensitivity to new physics. The experimental result is the first measurement, made in 2010, by ATLAS, operating at the LHC start-up energy of 7 TeV. The result is compatible with the Standard Model and demonstrates how well the physics and the apparatus are understood. The first data is a tiny fraction of what will be accumulated in the coming years, and this study has set the stage for performing these measurements with confidence as the LHC accumulates luminosity and increases its energy, thereby probing smaller length scales.
Author: Brandon Kyle Schmoll Publisher: ISBN: Category : Heavy ion collisions Languages : en Pages : 175
Book Description
Heavy flavor quarks are produced early in heavy ion collisions and will experience the full evolution of the Quark Gluon Plasma (QGP). Measurements at forward rapidity may be influenced as much, or more, by the cold nuclear matter effects as by the hot nuclear matter effects associated with a QGP. As the medium evolves, the initial spatial anisotropy of participants is converted to an azimuthal anisotropy in the momentum space of outgoing particles. Therefore, the momentum spectra modification and anisotropy parameters provide useful information about the heavy quark interaction with the bulk medium. Asymmetric heavy ion collisions, such as Cu+Au, provide a unique geometry with which to study the dynamics of the heavy quarks, relative to that in symmetric collisions. In particular, asymmetries in the yields between the Cu-going and Au-going directions may help unentangle the so-called cold nuclear matter effects from the hot nuclear matter effects indicative of a QGP. In addition, the parameters v2 and v3 in asymmetric collisions may be modified relative to the symmetric collisions due to the unique geometry provided in mid-central Cu+Au collisions. This dissertation presents the measurement of the yield and azimuthal anisotropy of single muons originating from heavy flavor decays in [square root of]SNN [center-of-mass energy per nucleon] = 200 GeV Cu+Au collisions.
Author: Publisher: ISBN: Category : Languages : en Pages : 27
Book Description
The azimuthal anisotropy of charged particles in PbPb collisions at nucleon-nucleon center-of-mass energy of 2.76 TeV is measured with the CMS detector at the LHC over an extended transverse momentum (pt) range up to approximately 60 GeV. The data cover both the low-pt region associated with hydrodynamic flow phenomena and the high-pt region where the anisotropies may reflect the path-length dependence of parton energy loss in the created medium. The anisotropy parameter (v2) of the particles is extracted by correlating charged tracks with respect to the event-plane reconstructed by using the energy deposited in forward-angle calorimeters. For the six bins of collision centrality studied, spanning the range of 0-60% most-central events, the observed v2 values are found to first increase with pt, reaching a maximum around pt = 3 GeV, and then to gradually decrease to almost zero, with the decline persisting up to at least pt = 40 GeV over the full centrality range measured.
Author: Prashanth Shanmuganathan Publisher: ISBN: Category : Hadron interactions Languages : en Pages : 128
Book Description
Excited nuclear matter at high temperature and density results in the creation of a new state of matter called Quark Gluon Plasma (QGP). It is believed that the Universe was in the QGP state a few millionths of a second after the Big Bang. A QGP can be experimentally created for a very brief time by colliding heavy nuclei, such as gold, at ultra-relativistic energies. The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory consists of two circular rings, 3.8 km in circumference, which can accelerate heavy nuclei in two counter-rotating beams to nearly the speed of light (up to 100 GeV per beam). STAR (Solenoidal Tracker At RHIC) is one of two large detectors at the RHIC facility, and was constructed and is operated by a large international collaboration made up of more than 500 scientists from 56 institutions in 12 countries. STAR has been taking data from heavy ion collisions since the year 2000. An important component of the physics effort of the STAR collaboration is the Beam Energy Scan (BES), designed to study the properties of the Quantum Chromodynamics (QCD) phase diagram in the regions where a first-order phase transition and a critical point may exist. Phase-I of the BES program took data in 2010, 2011 and 2014, using Au+Au collisions at a center-of-mass energy per nucleon pair of 7.7, 11.5, 14.5, 19.6, 27 and 39 GeV. It is by now considered a well-established fact that the QGP phase exists. However, all evidence so far indicates that there is a smooth crossover when normal hadronic matter becomes QGP and vice versa in collisions at the top energy of RHIC (and likewise at the Large Hadron Collider at the CERN laboratory in Switzerland). At these very high energies, the net density of baryons like nucleons is quite low, since there are almost equal abundances of baryons and antibaryons. It is known that net-baryon compression increases as the beam energy is lowered below a few tens of GeV. Of course, if the beam energy is too low, then the QGP phase cannot be produced at all, so it has been proposed that there is an optimum beam energy, so far unknown, where phenomena like a first-order phase transition and a critical point might be observed. On the other hand, there also exists the possibility that a smooth crossover to QGP occurs throughout the applicable region of the QCD phase diagram. Experiments are needed to resolve these questions. In this dissertation, I focus on one of the main goals of the BES program, which is to search for a possible first-order phase transition from hadronic matter to QGP and back again, using measurements of azimuthal anisotropy. The momentum-space azimuthal anisotropy of the final-state particles from collisions can be expressed in Fourier harmonics. The first harmonic coefficient is called directed flow, and reflects the strength of the collective sideward motion, relative to the beam direction, of the particles. Models tell us that directed flow is imparted during the very early stage of a collision and is not much altered during subsequent stages of the collision. Thus directed flow can provide information about the early stages when the QGP phase exists for a short time. A subset of hydrodynamic and nuclear transport model calculations with the assumption of a first-order phase transition show a prominent dip in the directed flow versus beam energy. I present directed flow and its slope with respect to rapidity, for identified particle types, namely lambda, anti-lambda and kaons as a function of beam energy for central, intermediate and peripheral collisions. The production threshold of neutral strange particles requires them to be created earlier, and these particles have relatively long mean free path. Thus these particles may probe the QGP at earlier times. In addition, new Lambda measurements can provide more insight about baryon number transported to the midrapidity region by stopping process of the nuclear collision. It is noteworthy that net-baryon density (equivalent to baryon chemical potential) depends not only on beam energy but also on collision centrality. The centrality dependence of directed flow and its slope are also studied for all BES energies for nine identified particle types, lambda, anti-lambda, neutral kaons, charged kaons, protons, anti-protons, and charged pions. These detailed results for many particle species, where both centrality and beam energy are varied over a wide range, strongly constrain models. The measurements summarized above pave the way for a new round of model refinements and subsequent comparisons with data. If the latter does not lead to a clear conclusion, the BES Phase-II program will take data in 2019 and 2020 with an upgraded STAR detector with wider acceptance, greatly improved statistics, and will extend measurements to new energy points.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The Fourier coefficients v[2] and v[3] characterizing the anisotropy of the azimuthal distribution of charged particles produced in PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV are measured with data collected by the CMS experiment. The measurements cover a broad transverse momentum range, pt= 1-100 GeV. The analysis focuses on pt> 10 GeV range, where anisotropic azimuthal distributions should reflect the path-length dependence of parton energy loss in the created medium. Results are presented in several bins of PbPb collision centrality, spanning the 60x% most central events. The v[2] coefficient is measured with the scalar product and the multiparticle cumulant methods, which have different sensitivities to the initial-state fluctuations. The values of both methods remain positive up to pt ~ 70 GeV, in all examined centrality classes. The v[3] coefficient, only measured with the scalar product method, tends to zero for pt>~ 20 GeV. Comparisons between theoretical calculations and data provide new constraints on the path-length dependence of parton energy loss in heavy ion collisions and highlight the importance of the initial-state fluctuations.
Author: Mahmoud Rateb
Author: Mahmoud Rateb
Author: Michael Richard Lomnitz
Author: Yang Wu
Author: Fareha G. A. Atetalla
Author: Vladimir Vladislavovich Anisovich
Author: Nele Boelaert
Author: Brandon Kyle Schmoll![Azimuthal Anisotropy of Charged Particles at High Transverse Momenta in PbPb Collisions at Sqrt(s[NN] PDF](https://books.google.com/books/content/images/frontcover/ygnEwQEACAAJ?fife=w80-h100)
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Author: Prashanth Shanmuganathan
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