Mid Rapidity Lambda And Anti Lambda Production In Au Au Collisions At The Relativistic Heavy Ion Collider
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Mid Rapidity Lambda And Anti Lambda Production In Au Au Collisions At The Relativistic Heavy Ion Collider
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Author : Hui Long
language : en
Publisher:
Release Date : 2002
Mid Rapidity Lambda And Anti Lambda Production In Au Au Collisions At The Relativistic Heavy Ion Collider written by Hui Long and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with categories.
High Energy Physics Index
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Author :
language : en
Publisher:
Release Date : 1990
High Energy Physics Index written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1990 with Nuclear physics categories.
Government Reports Annual Index
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Author :
language : en
Publisher:
Release Date : 199?
Government Reports Annual Index written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 199? with categories.
Government Reports Announcements Index
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Author :
language : en
Publisher:
Release Date : 1992-12
Government Reports Announcements Index written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1992-12 with Science categories.
Lambda And Anti Lambda Production In Relativistic Heavy Ion Collisions Of Au Au At 11 6a Gev C
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Author : Jeffrey M. Sheen
language : en
Publisher:
Release Date : 2001
Lambda And Anti Lambda Production In Relativistic Heavy Ion Collisions Of Au Au At 11 6a Gev C written by Jeffrey M. Sheen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
First Moment Of Azimuthal Anisotropy In Au Au Collisions From The Beam Energy Scan At The Relativistic Heavy Ion Collider
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Author : Prashanth Shanmuganathan
language : en
Publisher:
Release Date : 2016
First Moment Of Azimuthal Anisotropy In Au Au Collisions From The Beam Energy Scan At The Relativistic Heavy Ion Collider written by Prashanth Shanmuganathan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with Hadron interactions categories.
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.
Probing Quark Gluon Plasma And Chiral Effects In Heavy Ion Collisions Measurements Of Strangeness Omega And Phi Production And Identified Particle Correlation In Au Au Collisions At Star Rhic
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Author : Liwen Wen
language : en
Publisher:
Release Date : 2019
Probing Quark Gluon Plasma And Chiral Effects In Heavy Ion Collisions Measurements Of Strangeness Omega And Phi Production And Identified Particle Correlation In Au Au Collisions At Star Rhic written by Liwen Wen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
Ultra-relativistic heavy-ion collision produces an extremely hot and dense medium of de-confined quarks and gluons, which is called Quark-Gluon Plasma (QGP). The STAR detector at Relativistic Heavy Ion Collider (RHIC) provides powerful experimental capabilities to probe the properties of this new form of matter, as well as novel quantum effects induced by the restoration of fundamental symmetry in qauntum-chromdynamics (QCD). Towards these goals, two research projects have been carried out at STAR/RHIC and will be presented in this thesis: 1) Measurement of mid-rapidity ($|y|0.5$) multi-strangenss particle ($\Omega$ and $\phi$) production in Au+Au collisions at $\sqrt{s_{NN}}=14.5$ GeV; 2) A systematic search for chiral effects using identified particle correlation. Production mechanism for strange hadrons could be dramatically different in the presence of QGP compared to regular $pp$ collisions. Thus strangeness signal is used extensively in Beam Energy Scan I (BES-I) program at RHIC to map out the phase diagram of QCD matter. As a part of BES-I, gold nuclei are collided at $\sqrt{s_{NN}} = 14.5$ GeV and the productions of mid-rapidity $\Omega(sss)$ and $\phi(\bar{s}s)$ are measured for the collisions. The ratio of anti-omega ($\bar{\Omega}$) over omega ($\Omega^-$) is calculated and used to extract thermodynamics parameters ($\mu_B/T$ and $\mu_S/T$) of collision system via statistical model. Additionally, the transverse momentum ($p_T$) dependence of nuclear modification factor ($R_{cp}$) is measured for $\phi$ meson and the result shows similar feature to energies lower than 19.6 GeV. As a test of coalescence formation mechanism for strange hadrons, $\textrm{N}(\Omega^-+\bar{\Omega}^+)/2(\textrm{N}(\phi))$ as a function of $p_T$ is studied and the data from central collision is found to deviate from model calculation and higher energy ($\sqrt{s_{NN}}19.6$ GeV) results in $p_T$ range from $2.0-3.0$ GeV/c, which may imply a transition of created medium whose underlying dominant degrees of freedom change from quarks/gluons to hadrons as collision energy goes below 19.6 GeV. %whose underlying dominant degrees of freedom change from quarks/gluons to hadrons as... With excellent particle identification capability of STAR, a systematic search for the Chiral Magnetic Effect (CME) via measurements of $\gamma_{112}$ correlation and $\kappa_K$ parameter for identified particle pairs ($\pi\pi$, $pK$, $\pi K$, $pp$, $p\pi$) in Au+Au collisions has been conducted. The $\kappa_K$ results are compared to expectations from the \textit{A Multi-Phase Transport Model} (AMPT) simulations. Except $\pi\pi$ and $pp$ correlations, the CME signals from other particle pairs are consistent with background model. $\kappa_K$ from $\pi\pi$ shows higher values than background expectation, while the result for $pp$ is even lower than the background, which requires further investigation. %A study of $\gamma_{112}$ and $\delta$ correlations for $\Lambda p$ in Au+Au 27 GeV shows that in mid-central and mid-peripheral collisions, baryon numbers are separated across reaction plane, which is consistent with the Chiral Vortical Effect (CVE) expectation. To search for Chiral Vortical Effect (CVE), a measurement of $\gamma_{112}$ and $\delta$ correlations for $\Lambda p$ pairs in Au+Au collisions at $\sqrt{s_{NN}}=27$ GeV was carried out and the results show that the CVE induced baryon number separation may exist in mid-central and mid-peripheral collisions with little contamination from flowing resonance decay background. Future development of searches for the chirality effect in heavy ion collisions will also be discussed.
Strangeness Production And Strange V0 Charged Hadron Correlation In Heavy Ion Collisions
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Author : Feng Zhao
language : en
Publisher:
Release Date : 2014
Strangeness Production And Strange V0 Charged Hadron Correlation In Heavy Ion Collisions written by Feng Zhao and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
In relativistic heavy-ion collisions, experimental evidence indicates that a new form of matter with de-confined quarks and gluons named the Quark-Gluon Plasma(QGP) has been created. The Relativistic Heavy Ion Collider (RHIC) provides a unique opportunity to study the QGP matter. Strange hadron production is believed to be sensitive to parton dynamics in heavy-ion collisions. In particular, the strange quark production rate and its subsequent evolution in the dense partonic medium depend on the beam energy and the net baryon density. The productions of K0s, [Lambda], [Xi], [Omega] at mid-rapidity from Au+Au collisions at the beam energies of 7.7, 11.5, 19.6, 27, and 39GeV from the RHIC Beam Energy Scan Program are measured. We investigate the strangeness enhancement and ratios of anti-baryon to baryon yields as a function of beam energy at RHIC. Nuclear modification factors and ratios of baryon to meson yields are also studied. Implications on collision dynamics due to the increase in the baryon chemical potential at low beam energy and constraints on chemical freeze-out parameters will also be discussed in this thesis. Parity-odd domains are theorized to form inside the QGP and to cause electric charge separation with respect to the reaction plane in the relativistic heavy-ion collisions via the Chiral Magnetic Effect (CME). Such charge separation has been studied at RHIC and LHC via the difference in two particle correlation between the opposite charge and same charge hadrons. The [Lambda](Lambda) and K0s particles are charge-neutral, and are supposed to bear no charge separation effects due to CME. We study the correlation between the neutral particle and charged hadron to investigate background for charged hadron correlation. In addition, the large angular momentum in heavy-ion collisions is predicted to lead to the Chiral Vortical Effect (CVE) which induces a baryon number separation, in analogy with the electric charge separation caused by CME. We carried out a study of [Lambda] - p correlations to search for the CVE. We present measurements of correlations for [Lambda] - h±, K0s - p, [Lambda] - p, in Au+Au collisions at 39GeV and 200GeV, to study the electric charge and baryon number separations across the reaction plane.
Production Of Strange Clusters In Relativistic Heavy Ion Collisions
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Author :
language : en
Publisher:
Release Date : 1993
Production Of Strange Clusters In Relativistic Heavy Ion Collisions written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with categories.
We address a number of issues related to the production of strangeness in high energy heavy ion collisions, including the possibility that stable states of multi-strange hyperonic or quark matter might exist, and the prospects that such objects may be created and detected in the laboratory. We make use of events generated by the cascade code ARC to estimate the rapidity distribution dN/dy of strange clusters produced in Si+Au and Au+Au collisions at AGS energies. These calculations are performed in a simple coalescence model, which yields a consistent description of the strange cluster (d, [sup 3]HE, [sup 3]H, [sup 4]He) production at these energies. If a doubly strange, weakly bound [Lambda][Lambda] dibaryon exists, we find that it is produced rather copiously in Au+Au collisions, with dN/dy [approximately]0.1 at raid-rapidity. If one adds another non-strange or strange baryon to a cluster, the production rate decreases by roughly one or two orders of magnitude, respectively. For instance, we predict that the hypernucleus [sub [Lambda][Lambda]][sup 6]He should have dN/dy [approximately]5 [times] 10[sup [minus]6] for Au+Au central collisions. It should be possible to measure the successive [Lambda] [yields] p[pi][minus] weak decays of this object. We comment on the possibility that conventional multi-strange hypernuclei may serve as doorway states'' for the production of stable configurations of strange quark matter, if such states exist.
Anti P And Anti Lambda Production In Si Au Collisions At The Ags
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Author :
language : en
Publisher:
Release Date : 1996
Anti P And Anti Lambda Production In Si Au Collisions At The Ags written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996 with categories.
{Anti {ital p}} and {anti {Lambda}} production in central Si + Au collisions has been measured by E589 at the BNL-AGS. Preliminary {ital m}{sub {perpendicular}} spectra are presented for {anti {ital p}}'s and {anti {Lambda}}'s. The {ital dn/dy} distribution for {anti {ital p}}'s is also presented. Based on the {anti {ital p}} and {anti {Lambda}} measurements, {anti {Lambda}}/{anti {ital p}} ratios are calculated in the rapidity range of 1.1-1.5.