The First Harmonic Anisotropy of Charmed Mesons in 200 GeV Au+Au Collisions PDF Download
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Author: Fareha G. A. Atetalla
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Languages : en
Pages : 0
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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: Fareha G. A. Atetalla
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ISBN:
Category :
Languages : en
Pages : 0
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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: Ayman I.A. Hamad
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Category :
Languages : en
Pages : 0
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Quantum Chromodynamics (QCD), the theory of the strong interaction between quarks and gluons, predicts that at extreme conditions of high temperature and/or density, quarks and gluons are no longer confined within individual hadrons. This new deconfined state of quarks and gluons is called Quark-Gluon Plasma (QGP). The Universe was in this QGP state a few microseconds after the Big Bang. The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) on Long Island, NY was built to create and study the properties of QGP.Due to their heavy masses, quarks with heavy flavor (charm and bottom) are mainly created during the early, energetic stages of the collisions. Heavy flavor is considered to be a unique probe for QGP studies, since it propagates through all phases of a collision, and is affected by the hot and dense medium throughout its evolution. Initial studies, via indirect reconstruction of heavy flavor using their decay electrons, indicated a much higher energy loss by these quarks compared to model predictions, with a magnitude comparable to that of light quarks. Mesons such as D0 could provide information about the interaction of heavy quarks with the surrounding medium through measurements such as elliptic flow. Such data help constrain the transport parameters of the QGP medium and reveal its degree of thermalization.Because heavy hadrons have a low production yield and short lifetime (e.g. ct = 120μm for D0), it is very challenging to obtain accurate measurements of open heavy flavor in heavy-ion collisions, especially since the collisions also produce large quantities of light-flavor particles. Also due to their short lifetime, it is difficult to distinguish heavy-flavor decay vertices from the primary collision vertex; one needs a very high precision vertex detector in order to separate and reconstruct the decay of the heavy flavor particles in the presence of thousands of other particles produced in each collision.The STAR collaboration built a new micro-vertex detector and installed it in the experiment in 2014. This state-of-the-art silicon pixel technology is named the Heavy Flavor Tracker (HFT). The HFT was designed in order to perform direct topological reconstruction of the weak decay products from hadrons that include a heavy quark. The HFT consists of four layers of silicon, and it improves the track pointing resolution of the STAR experiment from a few mm to around 30 ℗æm for charged pions at a momentum of 1 GeV/c.In this dissertation, I focus on one of the main goals of the HFT detector, which is to study the elliptic flow v2 (a type of azimuthal anisotropy) for D0 mesons in Au+Au collisions at vsNN = 200 GeV. My analysis is based on the 2014 data set (about 1.2 billion collisions covering all impact parameters) that include data from the HFT detector. There are two new and unique analysis elements used in this dissertation. First, I performed the analysis using a Kalman filter algorithm to reconstruct the charmed-meson candidates. The standard reconstruction is via a simple helix-swim method. The advantage of using the Kalman algorithm is in the use of the full error matrix of each track in the vertex estimation and reconstruction of the properties of the heavy-flavor parent particle. Second, I also used the Tool for Multivariate Analysis (TMVA), a ROOT-environment tool, to its full potential for signal significance optimization, instead of the previous approach based on a set of fixed cuts for separating signal from background.This dissertation presents the elliptic component (v2) of azimuthal anisotropy of D0 mesons as a function of transverse momentum, pT . The centrality (impact parameter) dependence of D0 v2(pT) is also studied. Results are compared with similar studies involving light quarks, and with the predictions of several theoretical models.
Author: Michael Richard Lomnitz
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Category : Heavy ion collisions
Languages : en
Pages : 189
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Author: Mohammed Muniruzzaman
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Category : Collisions (Nuclear physics)
Languages : en
Pages : 544
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Author: Joseph A. Vanfossen (Jr)
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Category :
Languages : en
Pages : 0
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This research work is in the field of experimental nuclear physics, more specifically, the analysis of data taken with the Solenoidal Tracker at RHIC (STAR) apparatus at the Relativistic Heavy Ion Collider (RHIC) located at Brookhaven National Laboratory (BNL). There, we accelerate and collide beams of heavy ions (e.g. gold nuclei) at relativistic velocities. The collisions of heavy nuclei in the STAR Experiment compress nuclear matter to high densities, and heat it to extreme temperatures, over one trillion degrees Celsius. Under such conditions, Lattice QCD and other phenomeno- logical models predict a phase transition in nuclear matter, a transition, where quarks and gluons become deconfined, i.e. they freely move throughout the interaction volume and are no longer confined to individual nucleons, forming Quark Gluon Plasma (QGP), a new state of nuclear matter. The study of QGP, its properties and dynamics, will provide a better understanding of QCD, the strong force, and of the history of the early universe.Mesons containing heavy flavor (charm and bottom) quarks can be used in QGP searches. Heavy quarks are produced mainly in the early stages of a collisions via energetic parton-parton interactions; heavy flavor production in QGP or during hadronization is suppressed due to the high masses of the quarks. Heavy quarks can therefore be used to probe the whole evolution of the system and as a calibrated tool to better understand the nature of the early, hot matter formed in the collisions.A key finding by the experiments at RHIC is the anomalously low production of heavy flavor at high transverse momentum values. This was found by measuring the yields of the decay electrons from mesons containing either charm or bottom quarks. These measurements suffer from very large combinatorial backgrounds and conceal the parent's kinematic properties. A suppression of particle production at high transverse momenta is likely caused by their interaction with the hot and dense surrounding medium, as the quarks traverse it. Such suppression is an indicator that the medium generated in relativistic heavy-ion collisions is strongly interacting. Theoretical models were successful in describing the suppression of light quarks but under-predicted the observed heavy-flavor suppression. The data triggered a new effort in modeling where theorists started taking into account the energy loss due to elastic collisions between the traversing parton and the surrounding medium. To fully understand the interplay between elastic and inelastic collision mechanisms of light and heavy partons and the hot medium, we needed precise data on heavy flavor production. Also, in order to be able to access the parent's kinematic information, one needs to perform a full topological reconstruction of the parent's decay. This will also allow for the separation of charm and bottom mesons. The study of D0 mesons, the lightest mesons with a charm quark, can be used to study the properties of the medium created in collisions, such as the density, flow, and thermalization of the medium.This dissertation presents an attempt to measure D0/D0bar ratios and D0 meson production in Au+Au collisions at sqrt(s_NN) = 200 GeV from fully reconstructed decays. For this purpose, we used a silicon tracker in STAR consisting of the Silicon Vertex Tracker (SVT) and the Silicon Strip Detector (SSD), along with the Time Projection Chamber (TPC) in a special run in the year 2007. We have developed new calibration and microvertexing techniques in the data analysis. We performed full secondary vertex reconstruction, to topologically reconstruct the secondary vertex of the D0 meson in the decay channel D0 -> K- + pi+ (B.R. = 3.89% and ct = 123 μm) and then performed a standard invariant mass analysis. At the same time we used a new tool (TMVA) in high energy physics for optimizing the signal to background ratio.However, precise measurements of open heavy flavor are difficult to obtain with the SVT due to a) the low yields and short lifespan of heavy hadrons, b) the huge combinatorial background, c) the poor statistics in the final data sample and d) the poor resolution of the SVT. STAR proposed and built a new generation vertex tracker, the Heavy Flavor Tracker (HFT). The HFT made its debut during the 2014 year's run and has vastly improved the experiment's heavy flavor capabilities making STAR an ideal detector to study the hot and dense matter created in heavy ion collisions. Taking advantage of the greatly improved pointing resolution from a dedicated microvertex detector, it is possible to directly track and reconstruct weak decay products from hadrons comprised of heavy `charm' and `bottom' quarks with low background. The HFT consists of three sub-detectors: PIXEL (PXL), the Intermediate Silicon Tracker (IST), and the Silicon Strip Detector (SSD) with 4 separate layers of silicon to guide tracks reconstructed in the Time Projection Chamber down to a pointing resolution of around 30 ℗æm for 1 GeV/c pions, a requirement to distinguish between an event's primary vertex and the position of a hadron's decay.In this Dissertation we present the details of our SVT work, data analysis and results, and briefly show and discuss the recent results obtained with the HFT.
Author: Dmitri Vladimirovitch Kotchetkov
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ISBN:
Category : Collisions (Nuclear physics)
Languages : en
Pages : 522
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![Production of [phi] Mesons in Au+Au Collisions at 11.7 A. GeV/c PDF](https://books.google.com/books/content/images/frontcover/I67XpYkFfpwC?fife=w80-h100)
Author: Hong Xiang
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Category : Heavy ion collisions
Languages : en
Pages : 322
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Author: Yang Wu
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Category : Anisotropy
Languages : en
Pages : 0
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![Measurement of [phi] Meson Production in Cu+Cu Collisions at 200 GeV Using the PHOBOS Detector at RHIC PDF](https://books.google.com/books/content/images/frontcover/Dh1HmAEACAAJ?fife=w80-h100)
Author: Siarhei S. Vaurynovich
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Category :
Languages : en
Pages : 275
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Strong enhancement of production of strange particles, and in particular of [phi] mesons, in heavy ion collisions of sufficiently high energies has been predicted to be an indication of a formation of a new state of matter, composed of deconfined quarks and gluons and having a property of chiral symmetry, called Quark Gluon Plasma (QGP). Studying production of [phi] mesons is of special interest due to their small cross-section of interaction with non-strange hadrons and due to their long lifetime, which should allow [phi] mesons to decouple from the strongly interacting medium produced in heavy ion collisions early in time and to escape the medium before decaying, thereby preserving information about the conditions in which the mesons were produced. In addition, the decay properties of [phi] mesons have been predicted to be modified in a hadronic gas medium. The [phi] -> K+K~ decay is of particular interest since the mass of a [phi] meson in vacuum is very close to the mass of two charged kaons, and consequently, even a small change in the mass or the width of [phi] mesons or in the mass of kaons would have a strong effect on the decay properties. Measurement of [phi] meson production using the PHOBOS detector at the Relativistic Heavy Ion Collider (RHIC) has proven to be especially challenging due to a small acceptance of the PHOBOS spectrometer and due to a much lower than predicted yield of [phi] mesons in heavy ion collisions at the highest RHIC energy. The measurement required a development of a new tracking algorithm, specifically tailored to reconstruct charged kaons with a high efficiency in a high hit density environment, keeping at the same time the necessary computing time within feasible limits. Results of a measurement of [phi] meson invariant yield in the rapidity interval 0 y
Author: Steven S. Sherman
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Category :
Languages : en
Pages : 194
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