Download or read book Measurements of Lamba and Anti Lambda Polarization in Longitudinally Polarized Proton Proton Collisions at SQRT S NN written by and published by . This book was released on 2005 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: Preliminary results for the longitudinal polarization of A and hyperons in longitudinally polarized proton-proton collisions at √s = 200 GeV are presented. The [Lambda]({bar [Lambda]}) candidates are reconstructed at mid-rapidity (
Download or read book Longitudinal Spin Transfer to Lambda and Anti lambda Hyperons Produced in Polarized Proton proton Collisions at Center of Mass Energy written by Ramon Cendejas and published by . This book was released on 2012 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studies on the spin structure of the proton have been an active area of research; after the EMC experiment and subsequent experiments found that only about 30% of the total proton spin is carried by quark spins. The Relativistic Heavy Ion Collider (RHIC) is the world's first and only polarized proton collider. The Solenoidal Tracker At RHIC (STAR) has full azimuthal acceptance and is ideally suited to advance studies of the proton spin. The longitudinal spin transfer, DLL, of & lambda; and anti- & lambda; hyperons in longitudinally polarized proton-proton collisions is sensitive to quark and anti-quark polarization in the polarized proton; as well as to polarized fragmentation; and has been proposed as a possible probe of (anti- )strange quark polarization. The STAR collaboration has previously reported an initial proof-of-concept measurement of DLL of & lambda; and anti- & lambda; hyperons from a data sample obtained at sqr(s)=200 GeV in 2005. The data correspond to an integrated luminosity of 2 pb- with 50% beam polarization. Considerably larger data samples corresponding to 6.5 pb- and 25 pb- with beam polarizations of 57% at sqr(s)=200 GeV were obtained in 2006 and 2009 using an upgraded instrument. Improvements were made on the analysis procedure to reduce background contribution to the & lambda; + anti- & lambda; measurements. These new measurements of DLL form the main topic of this dissertation. The sample of hyperons residing within a jet that triggered the experiment are classified as near-side hyperons, and are analyzed separately from an away-side sample that has similar precision. In addition to DLL, the double longitudinal spin asymmetry, ALL, for the production of & lambda; and anti- & lambda; hyperons has been extracted. The dependences of DLL on pseudo-rapidity, pT, and the fragmentation ratio, z, are studied. The stated DLL from & lambda; and anti- & lambda; each disfavor one of the published model predictions for DLL for a combined & lambda; and anti- & lambda; sample, and are consistent with other predictions as well as with the preceding data. The disfavored model prediction is based on the assumption that up, down, and strange (anti- )quark spins contribute equally to polarized fragmentation into & lambda; + anti- & lambda; hyperons. Future data with improved statistical precision, including data at sqr(s)=500 GeV, are needed to discriminate between the other models.
Download or read book Longitudinal Spin Transfer to Lambda and Lambda Bar Hyperons in Polarized Proton Proton Collisions at Sqrt S written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The longitudinal spin transfer, D{sub LL}, from high energy polarized protons to [Lambda] and {bar [Lambda]} hypersons has been measured for the first time in proton-proton collisions at √s = 200 GeV with the STAR detector at RHIC. The measurements cover pseudorapidity, [eta], in the range.
Download or read book Longitudinal Spin Transfer in Inclusive Lambda and Lambda Barproduct Ion in Polarized Proton proton Collisions at Sqrt S written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This contribution reports on a proof-of-principle measurement of the longitudinal spin transfer D{sub LL} in inclusive [Lambda] and [Lambda] production in polarized proton-proton collisions at a center of mass energy √s = 200 GeV. The data sample consists of about 3 x 106 minimum bias events collected in the year 2005 by the STAR experiment at RHIC with proton beam polarizations of up to 50%. The [Lambda]({bar [Lambda]}) candidates are reconstructed at mid-rapidity (
Download or read book Global Polarization Measurement in Au Au Collisions written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The system created in non-central relativisticnucleus-nucleus collisions possesses large orbital angular momentum. Dueto spin-orbit coupling, particles produced in such a system could becomeglobally polarized along the direction of the system angular momentum. Wepresent the results of Lambda and anti-Lambda hyperon global polarizationmeasurements in Au+Au collisions at sqrt sNN=62.4 GeV and 200 GeVperformed with the STAR detector at RHIC. The observed globalpolarization of Lambda and anti-Lambda hyperons in the STAR acceptance isconsistent with zero within the precision of the measurements. Theobtained upper limit, lbar P Lambda, anti-Lambda rbar
Download or read book Anti Lambda Polarization in High Energy Pp Collisions WithPolarized Beams written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We study the polarization of the anti-Lambda particle in polarized high energy pp collisions at large transverse momenta. The anti-Lambda polarization is found to be sensitive to the polarization of the anti-strange sea of the nucleon. We make predictions using different parameterizations of the polarized quark distribution functions. The results show that the measurement of longitudinal anti-Lambda polarization can distinguish different parameterizations, and that similar measurements in the transversely polarized case can give some insights into the transversity distribution of the anti-strange sea of nucleon.
Download or read book Longitudinal Double spin Asymmetry and Cross Section for Inclusivejet Production in Polarized Proton Collisions at Sqrt s written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We report a measurement of the longitudinal double-spinasymmetry A_LL and the differential cross section for inclusivemidrapidity jet production in polarized proton collisions at sqrt(s)=200GeV. The cross section data cover transverse momenta 5
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 $\PLambda$.
Download or read book Measurement of the Longitudinal Double Spin Asymmetry for Dijet Production in Polarized Proton Proton Collisions at Sqrt s written by Daniel L. Olvitt and published by . This book was released on 2017 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding what contributes to the intrinsic angular momentum (spin) of the proton has been a major goal of the nuclear physics community. In the 1980s, it was discovered that quarks contribute 30% to the spin of the proton. This information led to a search to find other contributions to the spin of the proton. At STAR, the double spin asymmetry (ALL) is measured as it is sensitive to the polarized gluon distribution (Dg(x)). The STAR 2009 inclusive jet ALL at sqrt(s) = 200 GeV has been incorporated into two independent global fits. These fits show for the first time a statistically significant non-zero gluon contribution to the spin of the proton in the parton momentum fraction range x > 0.05. Dijet ALL is also measured at STAR. Dijets are advantageous since the parton momentum fraction (x) of the initial partons may be reconstructed to first order from final state measurements. In 2013 STAR collected an estimated 250 pb-1 of data at sqrt(s) = 510 GeV. The higher center of mass energy will allow STAR to probe Dg(x) at x values as low as 0.02. The large statistics will allow a reduction in the uncertainties. Once the data is incorporated into future global fits, it will allow for a more precise determination of Dg(x). The 2013 dijet ALL results will be presented. The results show good agreement with both global fits and previous STAR results dijet measurements.
Download or read book Measurement of Tranverse Polarization of Lambda Hyperons Produced at the Z0 Resonance written by Vincenzo Lia and published by . This book was released on 2000 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have performed a measurement of transverse polarization for A baryons produced after the collision of longitudinally polarized electrons and unpolarized positrons at the Z0 resonance. The measurement is based on 560,000 Z0 decays produced at the SLC and collected by the SLD collaboration at SLAC between 1993 and 1998. We define the axis of polarization as the cross product of the thrust axis direction and the [Lambda] momentum and we use the longitudinal polarization of the incoming electrons to sign the thrust axis according to the direction of the color field, thereby testing the Andersson-Gustavson-Ingelman model for [Lambda] transverse polarization. We find that if the mechanism responsible for [Lambda] transverse polarization is completely correlated with the color field direction -0.22% (P[Lambda])[perpendicular]
Download or read book Longitudinal Double Spin Asymmetry for Inclusive Jet Production in Polarized Proton proton Collisions at square Root Of S written by Julie Marie Millane and published by . This book was released on 2008 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the Inclusive Jet Longitudinal Double-Spin Asymmetry for polarized protons at \s = 200 GeV. The data were taken on the STAR experiment at RHIC during the 2005 run period and cover a jet transverse momentum range of 5
Download or read book Precision Measurement of the Longitudinal Double spin Asymmetry for Inclusive Jet Production in Polarized Proton Collisions at u221A s written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We report a new measurement of the midrapidity inclusive jet longitudinal double-spin asymmetry, ALL, in polarized pp collisions at center-of-mass energy √s = 200 GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep-inelastic scattering (DIS), semi-inclusive DIS, and RHIC pp data. Lastly, the measured asymmetries provide evidence at the 3? level for positive gluon polarization in the Bjorken-x region x > 0.05 .
Download or read book Longitudinal Double spin Asymmetry and Cross Section for Inclusive Neutral Pion Production in Polarized Proton Collisions at the Square Root of Sigma written by Alan Michael Hoffman and published by . This book was released on 2009 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: Twenty years of polarized lepton-nucleon scattering experiments have found that the contribution from quark spins (1/2[delta] [sigma]) to the spin of the proton is only ~ 35%. This has lead researchers to look elsewhere, specifically to gluon spin ([delta sigma]) for a large contribution to proton spin. [delta sigma] has been only loosely constrained in polarized DIS and SIDIS experiments. Polarized proton-proton collisions at RHIC provide sensitivity to [delta sigma] through measurements of the longitudinal double-spin asymmetry, ALL. This work presents a measurement of ALL for inclusive 7ro production in polarized proton-proton collisions using the STAR detector and data from RHIC Run 6. 7r0s are abundantly produced at mid-rapidity in proton-proton collisions, making them natural candidates for studies of [delta] [sigma]. Novel techniques for reconstructing 7ros at STAR are discussed, and a measurement of the unpolarized cross section presented. Finally, the measured ALL is compared to perturbative QCD predictions and from this comparison constraints are placed on [delta] [sigma].
Download or read book Dijet Production in Polarized Proton proton Collisions at the Square Root of Sigma written by Matthew Hsing Hung Walker and published by . This book was released on 2011 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polarized deep inelastic scattering (DIS) experiments indicate that quarks only carry approximately 30% of the proton spin, which led to interest in measuring the contributions of other components. Through polarized proton-proton collisions at the Relativistic Heavy Ion Collider (RHIC), the world's only polarized proton collider, it is possible to make an extraction of the polarized gluon distribution function [delta]g(x). This function describes the contribution of the gluon polarization to the proton spin. This thesis presents a measurement of the p + p ---> Jet + Jet + X (dijet) cross section from the 2005 RHIC running period and a measurement of the longitudinal double spin asymmetry ALL from the 2009 RHIC running period, both made using the Solenoidal Tracker at RHIC (STAR). The cross section is measured over the invariant mass range 20
Download or read book Measuring Transversity in Polarized P p Collisions with Di hadron Correlations at s written by Keith Landry and published by . This book was released on 2016 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: The transversity distribution, $h_1(x)$, of a transversely polarized proton describes the probability of partons with polarization parallel to the parent proton, carrying a momentum fraction $x$ of the parent proton. This distribution is fundamental for our understanding of the proton spin structure but still very much unknown for values of $x$ larger than about 0.15. We study transversely spin-polarized proton collisions at $\sqrt{s}=200$ GeV from STAR, because polarized p+p collisions at RHIC can access this $x$ region and, with a higher scale and transverse momentum, probe a different kinematic regime than SIDIS. We find sizable spin asymmetries in di-hadron correlations, which can be used to directly probe the transversity distribution of quarks inside protons because they arise from a transversely spin polarized quark fragmenting into two hadrons by the Interference Fragmentation Function.
Download or read book Polarization of Lambda0 and Anti Lambda0 Inclusively Produced by 610 GeV c Sigma and 525 GeV c Proton Beams written by and published by . This book was released on 2007 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have measured the polarization of?° and {bar?°} inclusively produced by 610 GeV/c?− and 525 GeV/c proton beams in the experiment SELEX during the 1996/7 fixed target run at Fermilab. The polarization was measured as a function of the? longitudinal momentum fraction x{sub F} and transverse momentum p{sub t}. For the?° produced by?− the polarization is increasing with x{sub F}, from slightly negative at x{sub F} ≈ 0 to about 15% at large x{sub F} ; it shows a non-monotonic behavior as a function of p{sub t}. For the proton beam, the {Lambda}° polarization is negative and decreasing as a function of x{sub F} and p{sub t}. The {bar {Lambda}°} polarization is compatible with 0 for both beam particles over the full kinematic range. The target dependence was examined but no statistically significant difference was found.
