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Book First Moment of Azimuthal Anisotropy in Au Au Collisions from the Beam Energy Scan at the Relativistic Heavy Ion Collider

Download or read book 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 published by . This book was released on 2016 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Book Kaon and Lambda Production at Intermediate Momentum

Download or read book Kaon and Lambda Production at Intermediate Momentum written by Paul Sorensen and published by LAP Lambert Academic Publishing. This book was released on 2010-09 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work Paul Sorensen has analyzed the production of mesons and baryons in heavy-ion collisions at Brookhaven s Relativistic Heavy Ion Collider (RHIC). In 2005, physicists at RHIC created the most perfect fluid in nature, called quark-gluon plasma, a hot, dense matter formed out of quarks and gluons that permeated the universe one microsecond after its birth. Sorensen s work plays a key role in elucidating that the flow of matter in the heavy-ion collisions is dominated by subatomic particles called quarks, indicating that quark-gluon plasma had been created. Sorensen s work helped discover quark number scaling in the elliptic flow of hadrons in nucleus-nucleus collisions, and he develops the interpretation showing the relevance of quark degrees of freedom in heavy ion interactions.

Book Anti P and anti Lambda Production in Si Au Collisions at the AGS

Download or read book Anti P and anti Lambda Production in Si Au Collisions at the AGS written by and published by . This book was released on 1996 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: {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.

Book 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

Download or read book 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 published by . This book was released on 2019 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Book Strangeness Production and Strange V0 Charged Hadron Correlation in Heavy ion Collisions

Download or read book Strangeness Production and Strange V0 Charged Hadron Correlation in Heavy ion Collisions written by Feng Zhao and published by . This book was released on 2014 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Book Phi Meson Production in Au Au Collisions at the Relativistic Heavy Ion Collider

Download or read book Phi Meson Production in Au Au Collisions at the Relativistic Heavy Ion Collider written by Eugene Toyonari Yamamoto and published by . This book was released on 2001 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Production of Strange Clusters in Relativistic Heavy Ion Collisions

Download or read book Production of Strange Clusters in Relativistic Heavy Ion Collisions written by and published by . This book was released on 1993 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Book Scaling Properties of Hyperon Production in Au Au Collisions at Sqrt SNN

Download or read book Scaling Properties of Hyperon Production in Au Au Collisions at Sqrt SNN written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the scaling properties of Lambda, Xi, and their anti-particles produced at mid-rapidity in Au+Au collisions at RHIC at psNN = 200 GeV. The yield of multi-strange baryons per participant nucleon increases from peripheral to central collisions more rapidly than the Lambda yield, which appears to correspond to an increasing strange quark density of matter produced. The value of the strange phase space occupancy factor gamma s, obtained from a thermal model fit to the data, approaches unity for the most central collisions. We also show that the nuclear modification factors, RCP, of Lambda and Xi are consistent with each other and with that of protons in the transverse momentum range2.0

Book Lambda Production in AuAu Collisions at 11 6 GeV c

Download or read book Lambda Production in AuAu Collisions at 11 6 GeV c written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: I present the first measurement at AGS energies of the rapidity and transverse mass distributions for A production with Au beam on Au target. The measurements cover the rapidity region of 2.0 to 3.2 and transverse momenta of 0.0 to 1.4 GeV/c. The results are compared with the predictions of two models.

Book A Measurement of Lambda hyperon Spin Polarization in Au Au Collisions at Sqrt s NN

Download or read book A Measurement of Lambda hyperon Spin Polarization in Au Au Collisions at Sqrt s NN written by Joseph R. Adams (Nuclear physicist) and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Non-central collisions of relativistic atomic nuclei contain enormous angular momentum, $I\vec{J}I\sim\mathcal{O}(10^0-10^2\frac{\rm{TeV\cdot~fm}}{c}\approx10^3-10^5\hbar)$ in the collision energy range spanned by the capabilities of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab (BNL). The energy densities that exist in the collision interaction region are sufficient to deconfine constituent quarks from their bound nucleon states and thereby facilitate the short-lived ($\mathcal{O}(1\mathrm{fm}/c)$) formation of the so-called Quark-Gluon Plasma (QGP), to which some of the net $\vec{J}$ is transferred. The Solenoid Tracker At RHIC (STAR) is a set of detectors working in unison to reconstruct collision information, and is an indispensable tool used to study the QGP. I present here work surrounding $\vec{J}$, ranging from detector construction for STAR in order to accurately measure $\hat{J}$, experimental analysis of phenomena driven by $\vec{J}$ usig the STAR detector, and theoretical calculations involving the direction of $\vec{J}$ affected by event-by-event fluctuations. The "Event-Plane Detector" (EPD), after years of prototyping and design, was largely constructed at Ohio State University in 2017-2018 and officially replaced its predecessor, the Beam Beam Counter (BBC), at STAR. While similar detectors have been constructed, including the BBC, unique challenges were faced in the construction of the EPD. Due to many factors, including careful construction, the EPD's performance was and remains phenomenal, providing experimentalists in the STAR collaboration with far-improved resolution on $\hat{J}$. The use of the EPD was essential for drastically reducing the statistical uncertainties on a number of analyses, including the spin alignment of $\Lambda$ hyperons with $\hat{J}$, $\PLambda$. In this thesis is detailed the process of extracting the $\vec{J}$-driven $\PLambda$ at the relatively low center-of-momentum nucleon-nucleon collision energy of $\sNN=3$~GeV. In order to achieve such a low $\sNN$, the lowest yet achieved by RHIC, a "beam" of Au ions was made to hit a fixed Au foil target instead of two oppositely moving ion beams colliding; however, this fixed-target setup introduced numerous nuanced complications in order to extract $\PLambda$. A new experimental method to measure $\PLambda$ is introduced in this work to deal with such complicating details. I present here the observation of the largest yet-observed $\PLambda$ at the lowest $\sNN$ yet studied, as well as its dependences on event and $\Lambda$-hyperon kinematic variables. An inconclusive search for the magnetic field sustained in the QGP, $I\BQGPI$, is also presented here. While $\vec{J}$ drives $\PLambda$ as well as that of its anti-particle the $\bar{\Lambda}$ hyperons, $\PLamBar$, $\BQGP$ drives an enhancement of $\PLamBar$ and a suppression of $\PLambda$, leading to $\PLamBar-\PLambda$ splitting. This splitting has been observed in previous studies across a wide range of $\sNN$, but without sufficient statistical significance. A high-statistics data set at $\sNN=27$~GeV was performed by RHIC and collected by STAR which served as a promising tool to see a statistically significant splitting. The effort to measure the splitting at $\sNN=27$~GeV is briefly described in this thesis, but ultimately numerous complicated problems with the collider facility and the STAR detector presented nuanced dependences of the splitting; sufficient confidence could not be gained that unaccounted-for systematic effects would not be present. Also studied in this thesis were the effects of event-by-event nucleon-position fluctuations on the orientation of $\hat{J}$. Theoretical models of heavy-ion collisions were used to describe the positions of nucleons at the momentum of impact, as well as the time evolution of the system. Unsurprisingly, the directions of angular momentum of the nucleons (and deconfined quarks) that participated in the collision, $\JpartHat$, and that of the "spectator" nucleons, $\JspecHat$, fluctuate on an event-by-event basis due to the randomness inherent in the system. Theoretical calculations of $\PLambda$ correlate the $\Lambda$-hyperon spin with the angular momentum direction of the system, $\JsystHat$, and the function form of $\PLambda$ used to extract the signal experimentally uses the measurable $\JspecHat$ as an approximation of $\JsystHat$; however, we discover an additional decorrelation between $\Jspec$ and $\Jpart$ driven by conservation of angular momentum. More importantly, we find a much more significant decorrelation between $\Jspec$ and $\Jpart$ when looking at the more restricted region of particles used for measuring $\PLambda$, driven by random fluctuations. We also find, importantly, that this decorrelation becomes larger with increasing $\sNN$ and therefore serves as a crucial correction to apply to the observable $\PLambda$.

Book Modification of K0s and Lambda AntiLambda Transverse Momentum Spectra in Pb Pb Collisions at sNN 2 76 TeV with ALICE

Download or read book Modification of K0s and Lambda AntiLambda Transverse Momentum Spectra in Pb Pb Collisions at sNN 2 76 TeV with ALICE written by Simone Schuchmann and published by Springer. This book was released on 2016-09-01 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis offers an excellent, comprehensive introduction to the physics of the quark–gluon plasma. It clearly explains the connection between theory and experiment, making the topic accessible to non-specialists in this field. The experimental work, which contributes significantly to our understanding of the quark–gluon plasma, is described in great detail. The results described in the final chapters of the thesis provide interesting new ideas about the connection between proton-proton and Pb-Pb collisions. Simone Schuchmann received the 'ALICE Thesis Award 2016' for this excellent work.

Book Relative Yields of Antiparticles to Particles in Au Au Collisions at 130 and 200 GeV Per Nucleon Pair

Download or read book Relative Yields of Antiparticles to Particles in Au Au Collisions at 130 and 200 GeV Per Nucleon Pair written by Kristján Herlache Gulbrandsen and published by . This book was released on 2004 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: Au+Au collisions at [square root of] [superscript]s nn = 130 and 200 GeV at the Relativistic Heavy Ion Collider have opened a new energy regime for studying nucleus-nucleus collisions. A search for the formation of a phase of matter in which quarks and gluons interact strongly over an extended deconfined volume is of primary importance. The PHOBOS detector was constructed to measure many observables at RHIC. The primary subsystem used in this analysis is the PHOBOS spectrometer. The spectrometer is a multiplane silicon pad detector which detects particles traversing its pads as they propagate through a strong magnetic field. The hit positions are used along with energy loss information in the silicon pads to determine both the momentum and velocity of the particles, allowing for the identification of the particle species. One of the most basic pieces of information to be determined is the baryochemical potential of the system. This information has been determined through the measurement of the relative yields of antiparticles to particles in RHIC collisions ... These values are compared to model predictions and are used to evaluate the contribution of baryon transport relative to particle production in determining the yields of baryon at midrapidity in central Au+Au collisions at RHIC energies.

Book Energy and Centrality Dependence of Mid rapidity Charged Particle Multiplicity in Relativistic Heavy ion Collisions

Download or read book Energy and Centrality Dependence of Mid rapidity Charged Particle Multiplicity in Relativistic Heavy ion Collisions written by Michał Patrick Decowski and published by . This book was released on 2002 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: The properties of quantum chromodynamics (QCD), the modern theory of the strong interaction, can be investigated through the study of relativistic nucleus-nucleus collisions. Recently, the Relativistic Heavy-Ion Collider (RHIC) was completed and started taking data at ten times higher center-of-mass energies than the previous most energetic heavy-ion collisions. This thesis presents some of the first measurements at RHIC from any experiment. The PHOBOS detector is used to measure the charged particle pseudo-rapidity density at mid-rapidity (i.e., in [eta]