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Improved measurement of double helicity asymmetry in inclulsive midrapidity<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup></mml:math>production for polarized<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi><mml:mo>+</mml:mo><mml:mi>p</mml:mi></mml:math>collisions at<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msqrt><mml:mi>s</mml:mi></mml:msqrt><mml:mo>=</mml:mo><mml:mn>200</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>GeV</mml:mi></mml:math>

S. S. AdlerBrookhaven National Laboratory, Upton, New York 11973-5000, USAS. AfanasievJoint Institute for Nuclear Research, 141980 Dubna, Moscow Region, RussiaC. AidalaColumbia University, New York, New York 10027, USA and Nevis Laboratories, Irvington, New York 10533, USAN. N. AjitanandChemistry Department, Stony Brook University, Stony Brook, SUNY, New York 11794-3400, USAY. AkibaRIKEN, The Institute of Physical and Chemical Research, Wako, Saitama 351-0198, JapanA. Al-JamelNew Mexico State University, Las Cruces, New Mexico 88003, USAJ. AlexanderChemistry Department, Stony Brook University, Stony Brook, SUNY, New York 11794-3400, USAK. AokiKyoto University, Kyoto 606-8502, JapanL. AphecetcheSUBATECH (Ecole des Mines de Nantes, CNRS-IN2P3, Université de Nantes) BP 20722 - 44307, Nantes, FranceR. ArméndarizNew Mexico State University, Las Cruces, New Mexico 88003, USAS. H. AronsonBrookhaven National Laboratory, Upton, New York 11973-5000, USAR. AverbeckDepartment of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794, USAT. C. AwesOak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USAB. AzmounBrookhaven National Laboratory, Upton, New York 11973-5000, USAV. BabintsevIHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, RussiaA. BaldisseriDirection des EnergiesK. N. BarishUniversity of California - Riverside, Riverside, California 92521, USAP. D. BarnesLos Alamos National Laboratory, Los Alamos, New Mexico 87545, USAB. BassalleckUniversity of New Mexico, Albuquerque, New Mexico 87131, USAS. BatheInstitut für Kernphysik, University of Muenster, D-48149 Muenster, GermanyS. BatsouliColumbia University, New York, New York 10027, USA and Nevis Laboratories, Irvington, New York 10533, USAV. BaublisPNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, RussiaF. BauerUniversity of California - Riverside, Riverside, California 92521, USAA. BazilevskyBrookhaven National Laboratory, Upton, New York 11973-5000, USAS. BelikovIowa State University, Ames, Iowa 50011, USAR. BennettDepartment of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794, USAY. BerdnikovSaint Petersburg State Polytechnic University, St. Petersburg, RussiaM. T. BjorndalColumbia University, New York, New York 10027, USA and Nevis Laboratories, Irvington, New York 10533, USAJ. G. BoissevainLos Alamos National Laboratory, Los Alamos, New Mexico 87545, USAH. BorelDapnia, CEA Saclay, F-91191, Gif-sur-Yvette, FranceK. BoyleDepartment of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794, USAM. L. BrooksLos Alamos National Laboratory, Los Alamos, New Mexico 87545, USAD. S. BrownNew Mexico State University, Las Cruces, New Mexico 88003, USAN. BrunerUniversity of New Mexico, Albuquerque, New Mexico 87131, USAD. BucherInstitut für Kernphysik, University of Muenster, D-48149 Muenster, GermanyH. BueschingInstitut für Kernphysik, University of Muenster, D-48149 Muenster, GermanyV. BumazhnovIHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, RussiaG. BunceBrookhaven National Laboratory, Upton, New York 11973-5000, USAJ. M. Burward-HoyLos Alamos National Laboratory, Los Alamos, New Mexico 87545, USAS. ButsykDepartment of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794, USAX. CamardSUBATECH (Ecole des Mines de Nantes, CNRS-IN2P3, Université de Nantes) BP 20722 - 44307, Nantes, FranceS. CampbellDepartment of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794, USAJ.-S. ChaiKAERI, Cyclotron Application Laboratory, Seoul, South KoreaP. ChandBhabha Atomic Research Centre, Bombay 400 085, IndiaW. C. ChangInstitute of Physics, Academia Sinica, Taipei 11529, TaiwanS. ChernichenkoIHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, RussiaC. Y.Columbia University, New York, New York 10027, USA and Nevis Laboratories, Irvington, New York 10533, USAJ. ChibaKEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, JapanM. ChiuColumbia University, New York, New York 10027, USA and Nevis Laboratories, Irvington, New York 10533, USAI. J. ChoiYonsei University, IPAP, Seoul 120-749, KoreaR. K. ChoudhuryBhabha Atomic Research Centre, Bombay 400 085, IndiaT. ChujoBrookhaven National Laboratory, Upton, New York 11973-5000, USAV. CiancioloOak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USAC. R. ClevenGeorgia State University, Atlanta, Georgia 30303, USAY. CobigoDirection des EnergiesB. ColeColumbia University, New York, New York 10027, USA and Nevis Laboratories, Irvington, New York 10533, USAM. P. CometsIPN-Orsay, Universite Paris Sud, CNRS-IN2P3, BP1, F-91406, Orsay, FranceP. ConstantinIowa State University, Ames, Iowa 50011, USAM. CsanádELTE, Eötvös Loránd University, H - 1117 Budapest, Pázmány P. s. 1/A, HungaryT. CsörgőKFKI Research Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences (MTA KFKI RMKI), H-1525 Budapest 114, POBox 49, Budapest, HungaryJ. P. CussonneauSUBATECH (Ecole des Mines de Nantes, CNRS-IN2P3, Université de Nantes) BP 20722 - 44307, Nantes, FranceD. d’EnterriaColumbia University, New York, New York 10027, USA and Nevis Laboratories, Irvington, New York 10533, USAT. DahmsDepartment of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794, USAK. DasFlorida State University, Tallahassee, Florida 32306, USAG. DavidBrookhaven National Laboratory, Upton, New York 11973-5000, USAF. DeákELTE, Eötvös Loránd University, H - 1117 Budapest, Pázmány P. s. 1/A, HungaryH. DelagrangeLaboratoire de Physique Subatomique et des Technologies AssociéesA. DenisovIHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, RussiaA. DeshpandeDepartment of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794, USAE. J. DesmondBrookhaven National Laboratory, Upton, New York 11973-5000, USAA. DevismesDepartment of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794, USAO. DietzschUniversidade de São Paulo, Instituto de Física, Caixa Postal 66318, São Paulo CEP05315-970, BrazilA. DionDepartment of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794, USAJ. L. DrachenbergAbilene Christian University, Abilene, Texas 79699, U.S., USAO. DrapierLaboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS-IN2P3, Route de Saclay, F-91128, Palaiseau, FranceA. DreesDepartment of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794, USAA. K. DubeyWeizmann Institute, Rehovot 76100, IsraelA. DurumIHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, RussiaD. DuttaBhabha Atomic Research Centre, Bombay 400 085, IndiaV. DzhordzhadzeUniversity of Tennessee, Knoxville, Tennessee 37996, USAY. V. EfremenkoOak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USAJ. EgdemirDepartment of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, New York 11794, USAA. EnokizonoHiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, JapanH. En’yoRIKEN, The Institute of Physical and Chemical Research, Wako, Saitama 351-0198, JapanB. EspagnonInstitut National de Physique Nucléaire et de Physique des ParticulesS. EsumiInstitute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305, JapanD. E. FieldsUniversity of New Mexico, Albuquerque, New Mexico 87131, USAC. FinckNantes UniversitéF. FleuretÉcole PolytechniqueS. FokinRussian Research Center “Kurchatov Institute”, Moscow, RussiaB. ForestierLPC, Université Blaise Pascal, CNRS-IN2P3, Clermont-Fd, 63177 Aubiere Cedex, FranceB. D. FoxRIKEN BNL Research CenterZ. FraenkelWeizmann Institute, Rehovot 76100, IsraelJ. E. FrantzColumbia University, New York, New York 10027, USA and Nevis Laboratories, Irvington, New York 10533, USAA. FranzBrookhaven National Laboratory, Upton, New York 11973-5000, USAA. D. FrawleyFlorida State University, Tallahassee, Florida 32306, USAY. FukaoKyoto University, Kyoto 606-8502, JapanS.-Y. FungUniversity of California - Riverside, Riverside, California 92521, USAS. GadratUniversité Clermont AuvergneF. GastineauLaboratoire de Physique Subatomique et des Technologies Associées

2006lv

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Annotatsiya

We present an improved measurement of the double helicity asymmetry for ${\ensuremath{\pi}}^{0}$ production in polarized proton-proton scattering at $\sqrt{s}=200\text{ }\text{ }\mathrm{GeV}$ employing the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The improvements to our previous measurement come from two main factors: Inclusion of a new data set from the 2004 RHIC run with higher beam polarizations than the earlier run and a recalibration of the beam polarization measurements for the earlier run, which resulted in reduced uncertainties and increased beam polarizations. The results are compared to a Next to Leading Order (NLO) perturbative Quantum Chromodynamics (pQCD) calculation with a range of polarized gluon distributions.

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DOI: 10.1103/physrevd.73.091102

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