the role of psidis data in qcd global fits

The role of pSIDIS data The role of pSIDIS data in QCD global fitsin QCD global fits

Rodolfo SassotRodolfo SassotUniversidad de Buenos AiresUniversidad de Buenos Aires

DIS06, Tsukuba April 22, 2006

R. Sassot DIS06R. Sassot DIS06 22

how SIDIS data help to constrain , and how SIDIS data help to constrain , and

lagrange multipliers to estimate uncertaintieslagrange multipliers to estimate uncertainties


In collaboration with In collaboration with

D. de Florian, G. Navarro and X. JiangD. de Florian, G. Navarro and X. Jiang

hep-ph/0602236, and references therein.hep-ph/0602236, and references therein.

based on Phys.Rev.D71, 094018 (2005), based on Phys.Rev.D71, 094018 (2005),


why do we use semi-inclusive data?



• polarized inclusive DIS (pDIS) data fail to constrain pPDFs.




• e.m. interactions can not discriminate quarks from antiquarks:





valence vs. sea quarks






• spin/flavour symmetry: model dependence to be tested







• polarized semi-inclusive (SIDIS) data







• polarized semi-inlcusive (SIDIS) data

SMC @ CERN: p, d h± HERMES @ DESY: p,d,He h±, π±, K± COMPASS @ CERN: …..

CLAS & E04-113 @ JLAB: …..


how do we deal with pSIDIS data?



W R. Mertig, W. L. van Neerven, Z.Phys.C70 637 (1996) W. Vogelsang, Phys.Rev.D54 2023 (1996)


D. de Florian et al. Nuc.Phys.B470 (1996) 195 M. Stratmann W.Vogelsang Phys.Rev.D64 (2001) 114007



NLO combined analysis:



pDIS can probe:



pDIS can probe:

pSIDIS give access to:



pDIS can probe:




pDIS can probe:


positivity relative to MRST02: A.D. Maritn et al. Eur.Phys.J.C28 (2002) 455


does it work?


does it work?

• consistency: pSIDIS data fix quarks without spoiling


does it work?



does it work?


478-20=458 d.o.f313 pDIS165 pSIDIS

combined λ=1


does it work?


478-20=458 d.o.f313 pDIS165 pSIDIS

pDIS λ=0combined λ=1


does it work?


478-20=458 d.o.f313 pDIS165 pSIDIS

pSIDIS

pDIScombined


does it work?


478-20=458 d.o.f313 pDIS165 pSIDIS

pSIDIS

pDIS

KRE: S. Kretzer Phys.Rev.D62 054001 (2000)

combined

3232

does it work?


478-20=458 d.o.f313 pDIS165 pSIDIS

pSIDIS

pDIS


KKP: B. A. Kniehl, G. Kramer, B. Potter, Nucl.Phys.B582 514 (2000)

combined


what do we get from pSIDIS data?



• do pSIDIS data actually constrain ?




J. Pumplin et al. Phys.Rev.D65 014011 (2002)


does it make sense?


(not included in the fit)


(not included in the fit) (not included in the fit)


what can we expect from pSIDIS in the future?



• JLAB E04-113 p,d h±, π±, K± (2008)

• CLAS p π± (inminent)

E04-113 proton

• COMPASS d h± (inminent)



• JLAB E04-113 p,d h±, π±, K± (2008)


E04-113 proton



Conclusions:


Conclusions:

• pSIDIS opens a window to sea quarks and helps to constrain other densities


Conclusions:


• overall picture combined NLO global fits:


Conclusions:



perfect consistency pDIS/pSIDIS


Conclusions:




improved constraints on pPDFs


Conclusions:




improved constraints on pPDFsbest fits favor SU(3) in the sea


Conclusions:





agreement with preliminary data on


Conclusions:


• next round: COMPASS, CLAS & E04-113



improved constraints on pPDFsbest fits favour SU(3) in the seaagreement with preliminary data on


Conclusions:







improved direct constraints on


Conclusions:








indirect constraints on


Conclusions:








indirect constraints on

flavour fragmentation


NLO combined analysis: data


Fragmentation functions input:



flavor separation:

the role of psidis data in qcd global fits

Documents

pdis data

semiinclusive data

sassot dis06why

inclusive sidis data

sassot dis06does

role of psidis data

psidis data fix quarks

vogelsang phys