M. Stratmann - Univ. of Tuebingen

M. Stratmann
Are you M. Stratmann?

Claim your profile, edit publications, add additional information:

Contact Details

Name
M. Stratmann
Affiliation
Univ. of Tuebingen
City
Tübingen
Country
Germany

Pubs By Year

Pub Categories

 
High Energy Physics - Phenomenology (46)
 
High Energy Physics - Experiment (8)
 
Nuclear Experiment (7)
 
Nuclear Theory (6)
 
Physics - Materials Science (1)
 
Physics - Instrumentation and Detectors (1)
 
Physics - Accelerator Physics (1)

Publications Authored By M. Stratmann

We revisit the global QCD analysis of parton-to-kaon fragmentation functions at next-to-leading order accuracy using the latest experimental information on single-inclusive kaon production in electron-positron annihilation, lepton-nucleon deep-inelastic scattering, and proton-proton collisions. An excellent description of all data sets is achieved, and the remaining uncertainties in parton-to-kaon fragmentation functions are estimated and discussed based on the Hessian method. Extensive comparisons to the results from our previous global analysis are made. Read More

We give a detailed account of the phenomenology of all-order resummations of logarithmically enhanced contributions at small momentum fraction of the observed hadron in semi-inclusive electron-positron annihilation and the time-like scale evolution of parton-to-hadron fragmentation functions. The formalism to perform resummations in Mellin moment space is briefly reviewed, and all relevant expressions up to next-to-next-to-leading logarithmic order are derived, including their explicit dependence on the factorization and renormalization scales. We discuss the details pertinent to a proper numerical implementation of the resummed results comprising an iterative solution to the time-like evolution equations, the matching to known fixed-order expressions, and the choice of the contour in the Mellin inverse transformation. Read More

An Electron-Ion Collider (EIC) with center-of-mass energies sqrt(s_{eN}) ~ 20-100 GeV and luminosity L ~ 10^{34} cm^{-2} s^{-1} would offer new opportunities to study heavy quark production in high-energy electron or photon scattering on protons and nuclei. We report about an R&D project exploring the feasibility of direct measurements of nuclear gluon densities at large x (gluonic EMC effect, antishadowing) using open charm production at EIC. We describe the charm production rates and angle-momentum distributions at large x and discuss methods of charm reconstruction using next-generation detector capabilities (pi/K identification, vertex reconstruction). Read More

In this review, we discuss the results on the parton-to-pion fragmentation functions obtained in a combined NLO fit to data of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and lepton-nucleon deep-inelastic scattering. A more complete discussion can be found in Ref. [1]. Read More

We explore the feasibility of direct measurements of nuclear gluon densities using heavy-quark production (open charm, beauty) at a future Electron-Ion Collider (EIC). We focus on the regions x > 0.3 (EMC effect) and x ~ 0. Read More

2016Feb
Affiliations: 1BNL, 2U. Michigan, 3BNL, 4DESY, 5Kentucky U., 6Texas A&M, 7Los Alamos, 8Ohio State U., 9Baruch U., 10Iowa State U., 11BNL, 12Riken, 13Buenos Aires U., 14LBNL, 15Univ. of Tuebingen, 16UCLA, 17Univ. of Tuebingen, 18Indiana U., 19Univ. de Santiago de Compostela

The exploration of the fundamental structure of strongly interacting matter has always thrived on the complementarity of lepton scattering and purely hadronic probes. As the community eagerly anticipates a future electron ion collider (EIC) in the U.S. Read More

We present a first analysis of parton-to-pion fragmentation functions at next-to-next-to-leading order accuracy in QCD based on single-inclusive pion production in electron-positron annihilation. Special emphasis is put on the technical details necessary to perform the QCD scale evolution and cross section calculation in Mellin moment space. We demonstrate how the description of the data and the theoretical uncertainties are improved when next-to-next-to-leading order QCD corrections are included. Read More

We present a detailed assessment of how well a future Electron-Ion Collider could constrain helicity parton distributions in the nucleon and, therefore, unveil the role of the intrinsic spin of quarks and gluons in the proton's spin budget. Any remaining deficit in this decomposition will provide the best indirect constraint on the contribution due to the total orbital angular momenta of quarks and gluons. Specifically, all our studies are performed in the context of global QCD analyses based on realistic pseudo-data and in the light of the most recent data obtained from polarized proton-proton collisions at BNL-RHIC that have provided evidence for a significant gluon polarization in the accessible, albeit limited range of momentum fractions. Read More

2015Jan
Affiliations: 1BNL, 2BNL, 3DESY, 4Valparaiso U., 5BNL, 6Kentucky U., 7Texas A&M, 8Los Alamos, 9Ohio State U., 10Iowa State U., 11BNL, 12Milano U. & INFN, 13BNL, 14JLab, 15Buenos Aires U., 16Riken, 17LBNL, 18BNL, 19Temple U., 20Univ. of Tuebingen, 21Univ. of Tuebingen, 22Indiana U., 23Indiana U., 24LBNL

Time and again, spin has been a key element in the exploration of fundamental physics. Spin-dependent observables have often revealed deficits in the assumed theoretical framework and have led to novel developments and concepts. Spin is exploited in many parity-violating experiments searching for physics beyond the Standard Model or studying the nature of nucleon-nucleon forces. Read More

A polarized $ep/eA$ collider (Electron--Ion Collider, or EIC), with polarized proton and light-ion beams and unpolarized heavy-ion beams with a variable center--of--mass energy $\sqrt{s} \sim 20$ to $\sim100$~GeV (upgradable to $\sim 150$ GeV) and a luminosity up to $\sim 10^{34} \, \textrm{cm}^{-2} \textrm{s}^{-1}$, would be uniquely suited to address several outstanding questions of Quantum Chromodynamics, and thereby lead to new qualitative and quantitative information on the microscopic structure of hadrons and nuclei. During this meeting at Jefferson Lab we addressed recent theoretical and experimental developments in the spin and the three--dimensional structure of the nucleon (sea quark and gluon spatial distributions, orbital motion, polarization, and their correlations). This mini--review contains a short update on progress in these areas since the EIC White paper~\cite{Accardi:2012qut}. Read More

We present a new, comprehensive global analysis of parton-to-pion fragmentation functions at next-to-leading order accuracy in QCD. The obtained results are based on the latest experimental information on single-inclusive pion production in electron-positron annihilation, lepton-nucleon deep-inelastic scattering, and proton-proton collisions. An excellent description of all data sets is achieved, and the remaining uncertainties in parton-to-pion fragmentation functions are estimated based on the Hessian method. Read More

2014Sep
Affiliations: 1BNL, 2BNL, 3BNL, 4RBRC, 5BNL, 6BNL, 7BNL, 8BNL, 9BNL, 10BNL, 11BNL, 12BNL, 13BNL, 14BNL, 15BNL, 16BNL, 17BNL, 18BNL, 19BNL, 20BNL, 21BNL, 22BNL, 23BNL, 24BNL, 25BNL, 26BNL, 27BNL, 28BNL, 29BNL, 30BNL, 31BNL, 32BNL, 33Uni.-Tuebingen, 34LBNL, 35BNL, 36BNL, 37BNL, 38BNL, 39BNL, 40BNL, 41BNL, 42BNL, 43BNL, 44BNL, 45BNL, 46BNL, 47BNL

This document presents BNL's plan for an electron-ion collider, eRHIC, a major new research tool that builds on the existing RHIC facility to advance the long-term vision for Nuclear Physics to discover and understand the emergent phenomena of Quantum Chromodynamics (QCD), the fundamental theory of the strong interaction that binds the atomic nucleus. We describe the scientific requirements for such a facility, following up on the community-wide 2012 white paper, 'Electron-Ion Collider: the Next QCD Frontier', and present a design concept that incorporates new, innovative accelerator techniques to provide a cost-effective upgrade of RHIC with polarized electron beams colliding with the full array of RHIC hadron beams. The new facility will deliver electron-nucleon luminosity of 10^33-10^34 cm-1sec-1 for collisions of 15. Read More

We discuss the impact of recent high-statistics RHIC data on the determination of the gluon polarization in the proton in the context of a global QCD analysis of polarized parton distributions. We find clear evidence for a non-vanishing polarization of gluons in the region of momentum fraction and at the scales mostly probed by the data. Although information from low momentum fractions is presently lacking, this finding is suggestive of a significant contribution of gluon spin to the proton spin, thereby limiting the amount of orbital angular momentum required to balance the proton spin budget. Read More

Ultrathin passive films effectively prevent the chemical attack of stainless steel grades in corrosive environments; their stability critically depends on the interplay between structure and chemistry of the constituents Fe-Cr-Mo. In particular, nanoscale inhomogeneities along the surface can have a tremendous impact on material failure, but are yet barely understood. Addressing a stainless-type glass-forming Fe50Cr15Mo14C15B6 alloy and utilizing a combination of complementary high-resolution analytical techniques, we relate near-atomistic insight into different gradual nanostructures with time- and element-resolved dissolution behavior. Read More

We revive the idea of using physical anomalous dimensions in the QCD scale evolution of deep-inelastic structure functions and their scaling violations and present a detailed phenomenological study of its applicability. Differences with results obtained in the conventional framework of scale-dependent quark and gluon densities are discussed and traced back to the truncation of the perturbative series at a given order in the strong coupling. Read More

We present a detailed phenomenological study of charged-current-mediated deep-inelastic scattering off longitudinally polarized nucleons at a future Electron-Ion Collider. A new version of the event generator package DJANGOH, extended by capabilities to handle processes with polarized nucleons, is introduced and used to simulate charged current deep-inelastic scattering including QED, QCD, and electroweak radiative effects. We carefully explore the range of validity and the accuracy of the Jacquet-Blondel method to reconstruct the relevant kinematic variables from the measured hadronic final state in charged current events, assuming realistic detector performance parameters. Read More

2013Mar
Affiliations: 1BNL, 2BNL, 3RBRC, 4BNL, 5Kentucky, 6TAMU, 7Illinois, 8Iowa, 9Los Alamos, 10Ohio State, 11RBRC, 12Riken, 13Buenos Aires U., 14Riken, 15LBL, 16BNL, 17Tuebingen, 18Indiana, 19Indiana, 20LBL

This document summarizes recent achievements of the RHIC spin program and their impact on our understanding of the nucleon's spin structure, i.e. the individual parton (quark and gluon) contributions to the helicity structure of the nucleon and to understand the origin of the transverse spin phenomena. Read More

This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics and, in particular, the focused ten-week program on "Gluons and quark sea at high energies" at the Institute for Nuclear Theory in Fall 2010. Read More

We present a phenomenological study of charm quark photoproduction in longitudinally polarized lepton-hadron collisions at next-to-leading order accuracy of QCD. Our results are based on a recently developed, flexible parton-level Monte Carlo program for spin-dependent heavy flavor hadroproduction, which we extend to deal also with both direct and resolved photon contributions. The subsequent hadronization into charmed mesons is modeled in our calculations, which allows us to compare with data on double-spin asymmetries for D0 meson production taken by the COMPASS collaboration. Read More

We present a detailed assessment of uncertainties in parton-to-pion and parton-to-kaon fragmentation functions obtained in recent global QCD analyses of single-inclusive hadron production data at next-to-leading order accuracy. We use the robust Lagrange multiplier approach for determining uncertainties to validate the applicability of the simpler but approximate Hessian method. Extensive comparisons of the results obtained within both methods are presented for the individual parton-to-pion and kaon fragmentation functions. Read More

We present a quantitative assessment of the impact a future electron-ion collider will have on determinations of helicity quark and gluon densities and their contributions to the proton spin. Our results are obtained by performing a series of global QCD analyses at next-to-leading order accuracy based on realistic sets of pseudo-data for the inclusive and semi-inclusive deep-inelastic scattering of longitudinally polarized electrons and protons at different, conceivable center-of-mass system energies. Read More

We present a new global QCD analysis of nuclear parton distribution functions. In addition to the most commonly analyzed data sets for deep inelastic scattering of charged leptons off nuclei and Drell Yan di-lepton production, we include also measurements for neutrino-nuclei scattering as well as inclusive pion production in deuteron-gold collisions. The emerging picture is one of consistency, where universal nuclear modification factors for each parton flavor reproduce the main features of all data without any significant tension among the different sets. Read More

We present a new global QCD analysis of nuclear parton distribution functions and their uncertainties. In addition to the most commonly analyzed data sets for the deep-inelastic scattering of charged leptons off nuclei and Drell-Yan di-lepton production, we include also measurements for neutrino-nucleus scattering and inclusive pion production in deuteron-gold collisions. The analysis is performed at next-to-leading order accuracy in perturbative QCD in a general mass variable flavor number scheme, adopting a current set of free nucleon parton distribution functions, defined accordingly, as reference. Read More

We discuss some recent developments concerning the nucleon's helicity parton distribution functions: New preliminary data from jet production at RHIC suggest for the first time a non-vanishing polarization of gluons in the nucleon. SIDIS measurements at COMPASS provide better constraints on the strange and light sea quark helicity distributions. Single-longitudinal spin asymmetries in W-boson production have been observed at RHIC and will ultimately give new insights into the light quark and anti-quark helicity structure of the nucleon. Read More

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. Read More

2011Aug
Authors: D. Boer, M. Diehl, R. Milner, R. Venugopalan, W. Vogelsang, A. Accardi, E. Aschenauer, M. Burkardt, R. Ent, V. Guzey, D. Hasch, K. Kumar, M. A. C. Lamont, Y. Li, W. J. Marciano, C. Marquet, F. Sabatie, M. Stratmann, F. Yuan, S. Abeyratne, S. Ahmed, C. Aidala, S. Alekhin, M. Anselmino, H. Avakian, A. Bacchetta, J. Bartels, H. BC, J. Beebe-Wang, S. Belomestnykh, I. Ben-Zvi, G. Beuf, J. Blumlein, M . Blaskiewicz, A. Bogacz, S. J. Brodsky, T. Burton, R. Calaga, X. Chang, I. O. Cherednikov, P. Chevtsov, G. A. Chirilli, C. Ciofi degli Atti, I. C. Cloet, A. Cooper-Sarkar, R. Debbe, Ya. Derbenev, A. Deshpande, F. Dominguez, A. Dumitru, R. Dupre, B. Erdelyi, C. Faroughy, S. Fazio, A. Fedotov, J. R. Forshaw, R. Geraud, K. Gallmeister, L. Gamberg, J. -H. Gao, D. Gassner, F. Gelis, G. P. Gilfoyle, G. Goldstein, K. Golec-Biernat, V. P. Goncalves, M. Gonderinger, M. Guzzi, P. Hagler, H. Hahn, L. Hammons, Y. Hao, P. He, T. Horn, W. A. Horowitz, M. Huang, A. Hutton, B. Jager, W. Jackson, A. Jain, E. C. Johnson, Z. -B. Kang, L. P. Kaptari, D. Kayran, J. Kewisch, Y. Koike, A. Kondratenko, B. Z. Kopeliovich, Y. V. Kovchegov, G. Krafft, P. Kroll, S. Kumano, K. Kumericki, T. Lappi, T. Lautenschlager, R. Li, Z. -T. Liang, V. N. Litvinenko, S. Liuti, Y. Luo, D. Muller, G. Mahler, A. Majumder, S. Manikonda, F. Marhauser, G. McIntyre, M. Meskauskas, W. Meng, A. Metz, C. B. Mezzetti, G. A. Miller, M. Minty, S. -O. Moch, V. Morozov, U. Mosel, L. Motyka, H. Moutarde, P. J. Mulders, B. Musch, P. Nadel-Turonski, P. Nadolsky, F. Olness, P. N. Ostrumov, B. Parker, B. Pasquini, K. Passek-Kumericki, A. Pikin, F. Pilat, B. Pire, H. Pirner, C. Pisano, E. Pozdeyev, A. Prokudin, V. Ptitsyn, X. Qian, J. -W. Qiu, M. Radici, A. Radyushkin, T. Rao, R. Rimmer, F. Ringer, S. Riordan, T. Rogers, J. Rojo, T. Roser, R. Sandapen, R. Sassot, T. Satogata, H. Sayed, A. Schafer, G. Schnell, P. Schweitzer, B. Sheehy, J. Skaritka, G. Soyez, M. Spata, H. Spiesberger, A. M. Stasto, N. G. Stefanis, M. Strikman, M. Sullivan, L. Szymanowski, K. Tanaka, S. Taneja, S. Tepikian, B. Terzic, Y. Than, T. Toll, D. Trbojevic, E. Tsentalovich, N. Tsoupas, K. Tuchin, J. Tuozzolo, T. Ullrich, A. Vossen, S. Wallon, G. Wang, H. Wang, X. -N. Wang, S. Webb, C. Weiss, Q. Wu, B. -W. Xiao, W. Xu, B. Yunn, A. Zelenski, Y. Zhang, J. Zhou, P. Zurita

This report is based on a ten-week program on "Gluons and the quark sea at high-energies", which took place at the Institute for Nuclear Theory in Seattle in Fall 2010. The principal aim of the program was to develop and sharpen the science case for an Electron-Ion Collider (EIC), a facility that will be able to collide electrons and positrons with polarized protons and with light to heavy nuclei at high energies, offering unprecedented possibilities for in-depth studies of quantum chromodynamics. This report is organized around four major themes: i) the spin and flavor structure of the proton, ii) three-dimensional structure of nucleons and nuclei in momentum and configuration space, iii) QCD matter in nuclei, and iv) Electroweak physics and the search for physics beyond the Standard Model. Read More

Fragmentation functions for eta mesons are extracted at next-to-leading order accuracy of QCD in a global analysis of data taken in electron-positron annihilation and proton-proton scattering experiments. The obtained parametrization is in good agreement with all data sets analyzed and can be utilized, for instance, in future studies of double-spin asymmetries for single-inclusive eta production. The Lagrange multiplier technique is used to estimate the uncertainties of the fragmentation functions and to assess the role of the different data sets in constraining them. Read More

We present a detailed phenomenological analysis of single-inclusive hadron production at the CERN-LHC in both proton-proton and proton-lead collisions. First data from the LHC experiments on charged hadron spectra are compared to next-to-leading order QCD expectations, and predictions are made for identified pion, kaon, and proton distributions differential in transverse momentum and rapidity for LHC energies from 900 GeV to 14 TeV. The results are obtained with the latest sets of vacuum fragmentation functions based on global QCD analyses, and recently proposed medium modified fragmentation functions are used to model hadronization in proton-lead collisions assuming standard QCD factorization. Read More

We perform a detailed phenomenological analysis of how well hadronization in nuclear environments can be described in terms of effective fragmentation functions. The medium modified fragmentation functions are assumed to factorize from the partonic scattering cross sections and evolve in the hard scale in the same way as the standard or vacuum fragmentation functions. Based on precise data on semi-inclusive deep-inelastic scattering off nuclei and hadron production in deuteron-gold collisions, we extract sets of effective fragmentation functions for pions and kaons at NLO accuracy. Read More

We present a comprehensive phenomenological study of heavy flavor distributions and correlations in longitudinally polarized proton-proton collisions at BNL-RHIC. All results are obtained with a flexible parton-level Monte Carlo program at next-to-leading order accuracy and include the fragmentation into heavy mesons, their subsequent semi-leptonic decays, and experimental cuts. Next-to-leading order QCD corrections are found to be significant for both cross sections and double-spin asymmetries. Read More

We discuss preliminary results on medium-modified fragmentation functions obtained in a combined NLO fit to data on semi-inclusive deep inelastic scattering off nuclei and hadroproduction in deuteron-gold collisions. Read More

We discuss techniques and results for the extraction of the nucleon's spin-dependent parton distributions and their uncertainties from data for polarized deep-inelastic lepton-nucleon and proton-proton scattering by means of a global QCD analysis. Computational methods are described that significantly increase the speed of the required calculations to a level that allows to perform the full analysis consistently at next-to-leading order accuracy. We examine how the various data sets help to constrain different aspects of the quark, anti-quark, and gluon helicity distributions. Read More

We present the mini-proceedings of the workshop on ``Parton fragmentation in the vacuum and in the medium'' held at the European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT*, Trento) in February 2008. The workshop gathered both theorists and experimentalists to discuss the current status of investigations of quark and gluon fragmentation into hadrons at different accelerator facilities (LEP, B-factories, JLab, HERA, RHIC, and Tevatron) as well as preparations for extension of these studies at the LHC. The main physics topics covered were: (i) light-quark and gluon fragmentation in the vacuum including theoretical (global fits analyses and MLLA) and experimental (data from e+e-, p-p, e-p collisions) aspects, (ii) strange and heavy-quark fragmentation, (iii) parton fragmentation in cold QCD matter (nuclear DIS), and (iv) medium-modified fragmentation in hot and dense QCD matter (high-energy nucleus-nucleus collisions). Read More

We present a new analysis of the helicity parton distributions of the nucleon. The analysis takes into account the available data from inclusive and semi-inclusive polarized deep inelastic scattering, as well as from polarized pp scattering at RHIC. For the first time, all theoretical calculations are performed fully at next-to-leading order (NLO) of perturbative QCD, using a method that allows to incorporate the NLO corrections in a very fast and efficient way in the analysis. Read More

We compute the next-to-leading order QCD corrections to the ``direct'' part of the spin-dependent cross section for hadron-pair photoproduction. The calculation is performed using largely analytical methods. We present a brief phenomenological study of our results focussing on the $K$-factors and scale dependence of the next-to-leading order cross sections. Read More

2007Aug
Affiliations: 1Regensburg U, 2Regensburg U, 3Wako, RIKEN

We present a detailed phenomenological study of the prospects of open charm physics at the future $\bar{p}p$ and $pp$ facilities GSI-FAIR and J-PARC, respectively. In particular, we concentrate on differential cross sections and the charge and longitudinal double-spin asymmetries at next-to-leading order accuracy. Theoretical uncertainties for the proposed observables are estimated by varying the charm quark mass and the renormalization and factorization scales. Read More

We present new sets of pion, kaon, proton and inclusive charged hadron fragmentation functions obtained in NLO combined analyses of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and deep-inelastic lepton-proton scattering with either particles identified in the final state. At variance with all previous fits, the present analyses take into account data where hadrons of different electrical charge are identified, which allow to discriminate quark from anti-quark fragmentation functions. Read More

We present new sets of fragmentation functions for protons and inclusive charged hadrons obtained in combined NLO QCD analyses of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and deep-inelastic lepton-proton scattering. These analyses complement previous results for pion and kaon fragmentation functions with charge and flavor discrimination. The Lagrange multiplier technique is used to assess the uncertainties in the extraction of the new sets of fragmentation functions. Read More

We consider the photoproduction of two hadrons in polarized lepton-nucleon collisions in the framework of perturbative QCD at the next-to-leading order accuracy. After illustrating how to obtain the experimentally relevant observables, a phenomenological study of the photoproduction of hadron pairs at high transverse momenta is presented. We show theoretical predictions for the relevant cross sections at COMPASS and HERMES kinematics as well as theoretical uncertainties. Read More

We present new sets of pion and kaon fragmentation functions obtained in NLO combined analyses of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and deep-inelastic lepton-proton scattering with either pions or kaons identified in the final state. At variance with all previous fits, the present analyses take into account data where hadrons of different electrical charge are identified, which allow to discriminate quark from anti-quark fragmentation functions without the need of non trivial flavor symmetry assumptions. The resulting sets are in good agreement with all data analyzed, which cover a much wider kinematical range than in previous fits. Read More

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. Read More

We present a detailed phenomenological study of photoproduction of two hadrons, both with high transverse momentum, in longitudinally polarized lepton-nucleon collisions. We consistently include ``direct'' and ``resolved'' photon contributions and examine the sensitivity of the relevant spin asymmetries to the gluon polarization in the nucleon and to the completely unknown parton content of circularly polarized photons. Our results are relevant for the COMPASS and HERMES fixed-target experiments as well as for a possible future polarized lepton-proton collider like eRHIC at BNL. Read More

We report on a calculation of the next-to-leading order QCD corrections to the partonic cross sections contributing to single-inclusive high-p_T hadron production in collisions of transversely polarized hadrons. We give some predictions for the double spin asymmetry A_TT^\pi for the proposed experiments at RHIC and at the GSI. Read More

We present a calculation of the next-to-leading order QCD corrections to the partonic cross sections contributing to single-inclusive high-p_T hadron production in collisions of transversely polarized hadrons. We use a recently developed projection technique for treating the phase space integrals in the presence of the cos(2Phi) azimuthal-angular dependence associated with transverse polarization. Our phenomenological results show that the double-spin asymmetry A_TT^pi for neutral-pion production is expected to be very small for polarized pp scattering at RHIC and could be much larger for the proposed experiments with an asymmetric pbar-p collider at the GSI Read More

We present a detailed phenomenological study of spin-dependent single-inclusive high-p_T hadron photoproduction with particular emphasis on the kinematics relevant for the Compass and Hermes fixed-target experiments. We carefully examine the theoretical uncertainties associated with the only moderate transverse momenta accessible in such measurements and analyze the sensitivity of the relevant spin asymmetries to the gluon polarization in the nucleon as well as to the completely unknown parton content of circularly polarized photons. Read More

We present a technique to calculate the cross sections and spin asymmetries for transversely polarized $pp$ collisions at NLO in QCD and report on the use of this technique for the processes $p^{\uparrow} p^{\uparrow} \to \gamma X$, $p^{\uparrow} p^{\uparrow} \to \pi X$ and $p^{\uparrow} p^{\uparrow} \to l^+ l^- X$. Read More

2004Aug
Affiliations: 1Regensburg U., 2Brookhaven & RIKEN BNL, 3Regensburg U., 4Brookhaven & RIKEN BNL

The longitudinally polarized gluon density is probed sensitively in hard collisions of polarized protons under the condition that the dominant dynamics are perturbative and of leading twist origin. First data have recently been presented by Phenix on the double-spin asymmetry A_{LL}^{pi} for pi^0 production at moderate transverse momentum p_\perp \simeq 1 - 4 GeV and central rapidity. By means of a systematic investigation of the relevant degrees of freedom we show that the perturbative QCD framework at leading power in p_\perp produces an asymmetry that is basically positive definite in this kinematic range, i. Read More

We present a next-to-leading order QCD calculation for single-inclusive high-p_T jet production in longitudinally polarized pp collisions within the ``small-cone'' approximation. The fully analytical expressions obtained for the underlying partonic hard-scattering cross sections greatly facilitate the analysis of upcoming BNL-RHIC data on the double-spin asymmetry A_{LL}^{jet} for this process in terms of the unknown polarization of gluons in the nucleon. We simultaneously rederive the corresponding QCD corrections to unpolarized scattering and confirm the results existing in the literature. Read More

Recent preliminary PHENIX data are consistent with a negative and sizable longitudinal double-spin asymmetry A_LL^pi for pi^0 production at moderate transverse momentum p_perp \simeq 1 - 4 GeV and central rapidity. By means of a systematic investigation of the relevant degrees of freedom we show that the perturbative QCD framework at leading power in p_perp produces at best a very small negative asymmetry in this kinematic range. Read More