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QCD Corrections in Transversely Polarized Scattering

Description: We discuss two recent calculations of higher-order QeD corrections to scattering of transversely polarized hadrons. A basic concept underlying much of the theoretical description of high-energy hadronic scattering is the factorization theorem, which states that large momentum-transfer reactions may be factorized into long-distance pieces that contain information on the structure of the nucleon in terms of its parton densities, and parts that are short-distance and describe the hard interactions of the partons. Two crucial points are that on the one hand the long-distance contributions are universal, i.e., they are the same in any inelastic reaction under consideration, and that on the other hand the short-distance pieces depend only on the large scales related to the large momentum transfer in the overall reaction and, therefore, may be evaluated using QCD perturbation theory. The lowest order for the latter can generally only serve to give a rough description of the reaction under study. It merely captures the main features, but does not usually provide a quantitative understanding. The first-order ('next-to-leading order' (NLO)) corrections are generally indispensable in order to arrive at a firmer theoretical prediction for hadronic cross sections, and in some cases even an all-order resummation of large perturbative corrections is needed. In the present paper we win discuss two calculations [1, 2] of higher-order QeD corrections to transversely polarized scattering.
Date: October 6, 2008
Creator: Vogelsang,W.
Partner: UNT Libraries Government Documents Department

Preliminary assessment of corrosion product transport in fusion reactors

Description: Corrosion which is tolerable from the standpoint of system mechanical integrity may cause substantial problems if the corrosion product is released and deposited at locations where it interferes with heat transfer or coolant flow. Furthermore, neutrons from the fusion reaction activate the corrosion product, causing radiation fields in maintenance areas near piping and components where the activated material deposits. Preliminary estimates suggest that formidable problems may occur in a lithium-cooled stainless steel primary circuit due to corrosion product deposition. If the estimated order of magnitude is confirmed in future studies, new concepts in corrosion control or corrosion product removal would need to be developed for lithium-cooled stainless steel CTR systems. Other fusion reactor system concepts and materials appear to offer alternatives which tend to minimize corrosion product transport. (auth)
Date: November 1, 1973
Creator: Johnson, A.B. Jr. & Vogelsang, W.F.
Partner: UNT Libraries Government Documents Department


Description: We discuss spin phenomena in high-energy hadronic scattering, with a particular emphasis on the spin physics program now underway at the first polarized proton-proton collider, RHIC. Experiments at RHIC unravel the spin structure of the nucleon in new ways. Prime goals are to determine the contribution of gluon spins to the proton spin, to elucidate the flavor structure of quark and antiquark polarizations in the nucleon, and to help clarify the origin of transverse-spin phenomena in QCD. These lectures describe some aspects of this program and of the associated physics.
Date: June 19, 2007
Partner: UNT Libraries Government Documents Department


Description: The determination of the polarized gluon distribution is a central goal of the RHIC spin program. Recent achievements in polarization and luminosity of the proton beams in RHIC, has enabled the RHIC experiments to acquire substantial amounts of high quality data with polarized proton beams at 200 and 62.4 GeV center of mass energy, allowing a first glimpse of the polarized gluon distribution at RHIC. Short test operation at 500 GeV center of mass energy has also been successful, indicating absence of any fundamental roadblocks for measurements of polarized quark and anti-quark distributions planned at that energy in a couple of years. With this background, it has now become high time to consider how all these data sets may be employed most effectively to determine the polarized parton distributions in the nucleon, in general, and the polarized gluon distribution, in particular. A global analysis of the polarized DIS data from the past and present fixed target experiments jointly with the present and anticipated RHIC Spin data is needed.
Date: October 8, 2007
Partner: UNT Libraries Government Documents Department


Description: We give an overview of the current status of investigations of the polarization of gluons in the nucleon. We describe some of the physics of the spin-dependent gluon parton distribution and its phenomenology in high-energy polarized hadronic scattering. We also review the recent experimental results.
Date: October 22, 2007
Partner: UNT Libraries Government Documents Department

QCD Spin Physics: Theoretical Overview

Description: We give an overview of some of the current activities and results in QCD spin physics. We focus on the helicity structure of the nucleon, where we highlight the results of a recent first global analysis of the helicity parton distributions, and on single-transverse spin asymmetries.
Date: November 9, 2008
Creator: Vogelsang,W.
Partner: UNT Libraries Government Documents Department


Description: We present theoretical predictions for the cross sections and spin asymmetries in dilepton pair production in transversely polarized pp and {bar p}p collisions. We use the available fixed-order corrections as well as the all-order resummation of threshold logarithms for the pair mass and rapidity distributions. Numerical results for pp collisions at {radical}s = 10 GeV at J-PARC and for {bar p}p collisions at {radical}s = 14.5 GeV at GSI-PAX are given.
Date: October 2, 2006
Partner: UNT Libraries Government Documents Department

Prompt Photon Production in Polarized Hadron Collisions.

Description: We consider spin asymmetries for prompt photon production in collisions of longitudinally polarized hadrons. This reaction will be a key tool at the BNL-RHIC {rvec p}{rvec p} collider for determining the gluon spin density in a polarized proton. We study the effects of QCD corrections, such as all-order soft-gluon ''threshold'' resummations.
Date: April 25, 2000
Creator: Vogelsang, W.
Partner: UNT Libraries Government Documents Department


Description: A comparison is given of the various recently published extractions of the Sivers functions from the HERMES and COMPASS data on single-transverse spin asymmetries in semi-inclusive deeply inelastic scattering.
Date: September 7, 2005
Creator: VOGELSANG, W.
Partner: UNT Libraries Government Documents Department

Global Analysis of Helicity PDFs: past - present - future

Description: We discuss the current status of the DSSV global analysis of helicity-dependent parton densities. A comparison with recent semi-inclusive DIS data from COMPASS is presented, and constraints on the polarized strangeness density are examined in some detail.
Date: April 11, 2011
Creator: de Florian, D.; Stratmann, M.; Sassot, R. & Vogelsang, W.
Partner: UNT Libraries Government Documents Department

Proceedings of RIKEN BNL Research Center Workshop: Brookhaven Summer Program on Nucleon Spin Physics

Description: Understanding the structure of the nucleon is of fundamental importance in sub-atomic physics. Already the experimental studies on the electro-magnetic form factors in the 1950s showed that the nucleon has a nontrivial internal structure, and the deep inelastic scattering experiments in the 1970s revealed the partonic substructure of the nucleon. Modern research focuses in particular on the spin and the gluonic structure of the nucleon. Experiments using deep inelastic scattering or polarized p-p collisions are carried out in the US at the CEBAF and RHIC facilities, respectively, and there are other experimental facilities around the world. More than twenty years ago, the European Muon Collaboration published their first experimental results on the proton spin structure as revealed in polarized deep inelastic lepton-nucleon scattering, and concluded that quarks contribute very little to the proton's spin. With additional experimental and theoretical investigations and progress in the following years, it is now established that, contrary to naive quark model expectations, quarks and anti-quarks carry only about 30% of the total spin of the proton. Twenty years later, the discovery from the polarized hadron collider at RHIC was equally surprising. For the phase space probed by existing RHIC experiments, gluons do not seem to contribute any to the proton's spin. To find out what carries the remaining part of proton's spin is a key focus in current hadronic physics and also a major driving force for the new generation of spin experiments at RHIC and Jefferson Lab and at a future Electron Ion Collider. It is therefore very important and timely to organize a series of annual spin physics meetings to summarize the status of proton spin physics, to focus the effort, and to layout the future perspectives. This summer program on 'Nucleon Spin Physics' held at Brookhaven National Laboratory (BNL) on July 14-27, ...
Date: August 2, 2011
Creator: Aschenauer, A.; Qiu, Jianwei; Vogelsang, W. & Yuan, F.
Partner: UNT Libraries Government Documents Department

Proceedings of RIKEN BNL Research Center Workshop: Progress in High-pT Physics at RHIC

Description: This volume archives the presentations at the RIKEN BNL Research Center workshop 'Progress in High-PT Physics at RHIC', held at BNL in March 2010. Much has been learned from high-p{sub T} physics after 10 years of RHIC operations for heavy-ion collisions, polarized proton collisions and d+Au collisions. The workshop focused on recent progress in these areas by both theory and experiment. The first morning saw review talks on the theory of RHIC high-p{sub T} physics by G. Sterman and J. Soffer, and on the experimental results by M. Tannenbaum. One of the most exciting recent results from the RHIC spin program is the first observation of W bosons and their associated single-spin asymmetry. The new preliminary data were reported on the first day of our workshop, along with a theoretical perspective. There also were detailed discussions on the global analysis of polarized parton distributions, including the knowledge on gluon polarization and the impact of the W-data. The main topic of the second workshop day were single-transverse spin asymmetries and their analysis in terms of transverse-momentum dependent parton distributions. There is currently much interest in a future Drell-Yan program at RHIC, thanks to the exciting physics opportunities this would offer. This was addressed in some of the talks. There also were presentations on the latest results on transverse-spin physics from HERMES and BELLE. On the final day of the workshop, the focus shifted toward forward and small-x physics at RHIC, which has become a cornerstone of the whole RHIC program. Exciting new data were presented and discussed in terms of their possible implications for our understanding of strong color-field phenomena in QCD. In the afternoon, there were discussions of nuclear parton distributions and jet observables, among them fragmentation. The workshop was concluded with outlooks toward the near-term (LHC, JLab) and longer-term ...
Date: March 17, 2010
Creator: Bazilevsky, A.; Bland, L. & Vogelsang, W.
Partner: UNT Libraries Government Documents Department


Description: The RHIC spin program is now fully underway. Several runs have been successfully completed and are producing exciting first results. Luminosity and polarization have improved remarkably and promising advances toward the higher RHIC energy of {radical}s = 500 GeV have been made. At this energy in particular, it will become possible to perform measurements of parity-violating spin asymmetries. Parity violation occurs in weak interactions, and in combination with the unique polarization capabilities at RHIC fascinating new opportunities arise. In particular, parity-violating single- and double-spin asymmetries give new insights into nucleon structure by allowing probes of up and down sea and anti-quark polarizations. Such measurements at RHIC are a DOE performance milestone for the year 2013 and are also supported by a very large effort from RIKEN. With transverse polarization, charged-current interactions may be sensitive to the Sivers effect. Parity-violating effects at RHIC have been proposed even as probes of physics beyond the Standard Model. With the era of measurements of parity-violating spin asymmetries at RHIC now rapidly approaching, we had proposed a small workshop that would bring together the main experts in both theory and experiment. We are very happy that this worked out. The whole workshop contained 17 formal talks, both experiment (10) and theory (7), and many fruitful discussions. The physics motivations for, the planned measurements were reviewed first. The RHIC machine prospects regarding polarized 500 GeV running were discussed, as well as the plans by the RHIC experiments for the vital upgrades of their detectors needed for the W physics program. We also had several talks on the topic of ''semi-inclusive deep-inelastic scattering'', which provides different access to related physics observables. On the theory side, new calculations were presented, for example in terms of QCD all-order resummations of perturbation theory. Also, new observables, such as jet and ...
Date: April 26, 2007
Partner: UNT Libraries Government Documents Department


Description: We present a recent study of the QCD corrections to dilepton production near partonic threshold in transversely polarized {bar p}p scattering, We analyze the role of the higher-order perturbative QCD corrections in terms of the available fixed-order contributions as well as of all-order soft-gluon resummations for the kinematical regime of proposed experiments at GSI-FAIR. We find that perturbative corrections are large for both unpolarized and polarized cross sections, but that the spin asymmetries are stable. The role of the far infrared region of the momentum integral in the resummed exponent and the effect of the NNLL resummation are briefly discussed.
Date: October 2, 2005
Partner: UNT Libraries Government Documents Department


Description: We present a calculation of the next-to-leading order QCD corrections to the partonic cross sections contributing to single-inclusive high-p{sub T} hadron production in collisions of transversely polarized hadrons. We use a recently proposed projection technique and give some predictions for the double spin asymmetry A{sub TT}{sup {pi}} for the proposed experiments at RHIC and at the GSI.
Date: September 7, 2006
Partner: UNT Libraries Government Documents Department