Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy Transversi ty (transverse spin and transverse motion) Transversity distributions – (some) theory Transversity distributions - experiments Transverse Single Spin Asymmetries (how to test a Quantum Field Theory) Spin and k ┴ dependent parton distributions (TMD)
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Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy Transversity (transverse spin and transverse motion) Transversity distributions.
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Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy
Transversity (transverse spin and transverse motion)
Transversity distributions – (some) theory
Transversity distributions - experiments
Transverse Single Spin Asymmetries (how to test a Quantum Field Theory)
Spin and k┴ dependent parton distributions (TMD)
Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy
Parton distributions
are fundamental leading-twist quark distributions
quark distribution – well known
quark helicity distribution – known
transversity distribution – unknown
all equally important
related to
positivity bound
qq , and 1h (or ) , qq T
qqq
qqq
qqqT
q qq 5
chiral-even
qT qq 5 related to chiral-odd
qqqT ||2
ggg gluon helicity distribution – poorly known
Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy
+–– –
++ +
+ +
+ =),( 2Qxq),( 2Qxq
+– =),( 2Qxq
),( 2QxqT
|| 2
1 iin helicity basis
–+
+ – ),( 2
1 Qxh decouples from DIS
Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy
Helicity conservation in pQCD or QED
qq ,
qq ',
qqqq E
mO q
''
Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy
h1 must couple to another chiral-odd function. For example: D-Y, pp → l+l– X, and SIDIS, l p → l π X, processes
++ –
++
–
+ –
–– +
–
+ –
h1 x h1
h1 x Collins function
J. Ralston and D.Soper, 1979 J. Cortes, B. Pire, J. Ralston, 1992
J. Collins, 1993
Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy
Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy
D. De Florian, G.A. Navarro and R. Sassot, hep-ph/0506326
Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy
–+
+1 –1
2 g
1
No gluon contribution to h1
simple Q2 evolution
Q2 = 25 GeV2 Q02
= 0.23 GeV2
V. Barone, T. Calarco, A. Drago
Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy
Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy
Predictions for K production at HERMES
Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy
SSA in p↑p → π X
fit to AN with Sivers effects alone
maximized value of AN
with Collins effects alone
E704 data, E = 200 GeV
U. D’Alesio, F. Murgia M.A, M. Boglione, U. D’Alesio, E. Leader, F. Murgia
Mauro Anselmino, Prague, August 1, 2005 Hadron Structure and Hadron Spectroscopy
The spin story goes on .......
Polarization data has often been the graveyard of fashionable theories. If theorists had their way, they might just ban such measurements altogether out of self-protection.