MEASUREMENT OF LONGITUDINAL SINGLE-SPIN ASYMMETRY FOR W± BOSON PRODUCTION IN POLARIZED PROTON-PROTON COLLISIONS AT STAR AT FORWARD RAPIDITY PDF Download

Author: Amani Kraishan
Publisher:
ISBN:
Category :
Languages : en
Pages : 117

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Author: Devika Sripali Gunarathne
Publisher:
ISBN:
Category :
Languages : en
Pages : 237

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Author: Ross Cameron Corliss
Publisher:
ISBN:
Category :
Languages : en
Pages : 169

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Understanding the structure of the proton is an ongoing effort in the particle physics community. Existing in the region of nonperturbative QCD, the various models for proton structure must be informed and constrained by experimental data. In 2009, the STAR experiment at Brookhaven National Lab recorded over 12 pb-1 of data from polarized p+p collisions at 500 GeV center-of-mass energy provided by the RHIC accelerator. This has offered a first look at the spin-dependent production of W+(-) bosons, and hence at the spin-flavor structure of the proton, where the main production mode is through d+u (u+d) annihilation. Using STAR's large Time Projection Chamber and its wide-acceptance electromagnetic calorimeters, it is possible to identify the e+ + v (e- + v) decay mode of the W bosons produced. This thesis presents the first STAR measurement of charge-separated W production, both the pseudorapidity-dependent ratio and the longitudinal single-spin asymmetry. These results show good agreement with theoretical expectations, validating the methods used and paving the way for the analysis of larger datasets that will be available soon. In the near future the range of this measurement will be augmented with the Forward GEM Tracker. A discussion of the design and implementation of this upgrade is also included, along with projections for its impact.

Author: Abraham Meles
Publisher:
ISBN:
Category : Collisions (Nuclear physics)
Languages : en
Pages : 348

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The contribution from the sea quarks to the proton spin have been poorly constrained mainly because of the limited knowledge we have on the fragmentation function in polarized Semi Inclusive Deep Inelastic Scattering (SIDIS) experments. The parity-violating longitudinal single spin asymmetry A[subscript L] in the production of W bosons in p + p collisions does not involve fragmentation function and is an alternative better way of exploring the polarization of sea quarks in the proton. The measurement will be useful especially in constraining ū and d̄ in the very backward and forward rapidities respectively. However, identifying the muons from the decay of the W is challenging due to a great background of hadronic in flight decays and other muon producing processes such as heavy flavor decays. In the forward and backward hemispheres of PHENIX at RHIC, the muon spectrometers have been recently upgraded in order to provide additional trigger and tracking information to suppress those backgrounds. One of those upgrades is the Forward Vertex (FVTX) detector, a silicon-strip tracker. In 2013, PHENIX accumulated the largest amount of polarized p + p collision data ever collected in the world (~ 240pb−1) at [square root symbol] s = 510 GeV with a beam polarization of 56%. The analysis techniques used to extract the signal from the data and the longitudinal single spin asymmetries A[subscript L] in RHIC 2013 run will be discussed.

Author:
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ISBN:
Category :
Languages : en
Pages :

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Author: Feng-kun Guo
Publisher: World Scientific
ISBN: 981121932X
Category : Science
Languages : en
Pages : 800

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This is the conference proceedings for the 18th International Conference on Hadron Spectroscopy and Structure (HADRON2019), held in Guilin, China. It is among the most important conference series in the field of hadron spectroscopy and structure. Collecting more than 130 contributions from this conference, the book spans over the topics of meson and baryon spectroscopy, exotic hadrons, hadron production and interactions, analysis tools, QCD and hadron structure, hadrons in nuclear environment and hypernuclei. Summaries of the recent discoveries from Belle, BESIII, LHCb and other high-energy experiments, as well as recent theoretical developments in the above mentioned topics, are contained in this volume, rendering it as a valuable resource for researchers working on hadron spectroscopy and structure.

Author: Alan Michael Hoffman
Publisher:
ISBN:
Category :
Languages : en
Pages : 126

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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].

Author:
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ISBN:
Category :
Languages : en
Pages :

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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 .

Author:
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ISBN:
Category :
Languages : en
Pages :

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In this paper, we present the measurement of the transverse single-spin asymmetry of weak boson production in transversely polarized proton-proton collisions at √s = 500 GeV by the STAR experiment at RHIC. The measured observable is sensitive to the Sivers function, one of the transverse-momentum-dependent parton distribution functions, which is predicted to have the opposite sign in proton-proton collisions from that observed in deep inelastic lepton-proton scattering. In conclusion, these data provide the first experimental investigation of the nonuniversality of the Sivers function, fundamental to our understanding of QCD.

Author: David William Kleinjan
Publisher:
ISBN: 9781303859892
Category : Heavy ion collisions
Languages : en
Pages : 161

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The measurement of transverse single spin asymmetries provides insight into the structure of the nucleon. Originally expected to be small, results from PHENIX and other experiments show significant asymmetries in the forward momentum direction of the polarized proton over a wide range of center-of-mass energies. Several mechanisms have been proposed that attempt to explain these asymmetries, which include initial and final state effects based on transverse momentum dependent distributions and perturbative Quantum Chromodynamic (pQCD) calculations at higher twist. Studying the species, and the kinematic dependencies of these transverse single spin asymmetries will help to disentangle the origin of the observed asymmetries. Using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC), the transverse single spin asymmetry (A N ) of inclusive eta mesons produced from transversely polarized proton-proton collisions at center of mass energy of 200 GeV at forward rapidity is measured. In addition, the predictive power of pQCD to explain this asymmetry is tested via the measurement of the eta meson Cross Section.