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NLO QCD fits to polarized DIS & SIDIS data. Rodolfo Sassot Universidad de Buenos Aires. Global Analysis Workshop, BNL October 8, 2007. why spin?. indispensable tool for unveiling hadron structure,. spin & unexpected physics. why polarized DIS?. - PowerPoint PPT Presentation
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NLO QCD fits to polarized NLO QCD fits to polarized DIS & SIDIS data DIS & SIDIS data
Rodolfo SassotRodolfo SassotUniversidad de Buenos AiresUniversidad de Buenos Aires
Global Analysis Workshop, BNL October 8, 2007
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 22
why spin? • indispensable tool for unveiling hadron
structure,
why polarized DIS?
• historical benchmark for hadron structure,
• spin & unexpected physics.
• 90’s experimental programs.
• QCD improved description for spin dependent processes• LO vs. NLO
why NLO QCD global fits?
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 33
• flavor and quark-antiquark discriminatrion,
what do we get from data?
• fits to inclusive/semi-inclusive polarized data. • uncertainties in pPDFs: Δq, Δg.
how can we improve the present picture?• further constraints from forthcoming data.
• fragmentation functions.
¯
• impact “direct” Δg measurements.
• increasead statistics, new/forthcoming data
why polarized SIDIS?
• sea quarks and flavor dependence in hadronization.
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 44
The case for pSIDIS: pDIS flavor decomposition
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 55
The case for pSIDIS: Flavor decomposition in pSIDIS
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 66
DNS NLO combined analysis: parameterizations
pDIS can probe:
pSIDIS give access to:
positivity relative to MRST02: 20 parameters
A.D. Maritn et al. Eur.Phys.J.C28 (2002) 455
D. de Florian, G. Navarro , R.S. Phys.Rev.D71 094018 (2005)
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 77
DNS NLO combined analysis: data
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 88
Fragmentation functions input in DNS:
KRE: S. Kretzer Phys.Rev.D62 054001 (2000)
KKP: B. A. Kniehl, G. Kramer, B. Potter, Nucl.Phys.B582 514 (2000)
flavor separation:
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 99
DNS Results:
478-20=458 d.o.f313 pDIS165 pSIDIS
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 1010
Uncertainties:
J. Pumplin et al. Phys.Rev.D65 014011 (2002)
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 1111
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 1212
Consistency with independent measurements: G. Navarro , R.S. PRD74 011502 (2006)
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 1313
STAR Coll., PRL97, 252001, (2006)
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 1414
Next steps:
DSS FFs: kaon fragmentation, h+/h-
MSTW PDFs: positivity constraints, evolution
New Compass SIDIS data: flavor at low x
Compass/Hermes DIS data (Q2-bin): gluon shape?
RHIC data: ALL , jets: Δg
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 1515
New “DSSV” pPDFs: pre-pre-pre-pre-preliminary….
NEW
NEW
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 1616
New “DSSV” pPDFs: pre-pre-pre-pre-preliminary
from Daniel’s talk
why has Δs changed??
old FFs were overestimated
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 1717
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 1818
Conclusions:
• pPDFs have evolved dramatically:
• pSIDIS opens a window to sea quarks and helps to constrain other densities
• dependence on FFs as a caveat:
• future prospects:
successfull experimental programs
tools for the analysis (NLO)
from ‘scenarios’ to ‘constraints’
• overall picture combined NLO global fits:
consistency pDIS/pSIDIS
improved constraints on pPDFsbest fits favor small Δg and SU(3)?
needs improvement!
encouraging!
new polarized data: RHIC, COMPASS, JLAB, eRHIC?
new generation of FFs
most exciting in the spin saga: the unexpected…
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 1919
Acknowledgments:
A. Deshpande, W. Vogelsang
RIKEN-BNL, hospitality and support.
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 2020
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 2121
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 2222
R. Sassot BNL, October 8, 2007R. Sassot BNL, October 8, 2007 2323
Results:
478-20=458 d.o.f313 pDIS165 pSIDIS
Interplay between pDIS and pSIDIS
D. de Florian, G. Navarro , R.S. Phys.Rev.D71 094018 (2005)
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