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<font color="#000099"><b><font color="#3333ff">Physics Seminar<br>
</font></b></font><font color="#3333ff"><b>Aug.24, 2012<br>
11:00 AM<br>
CEBAF Center AUD.<br>
Cookies and Coffee 10:45AM<br>
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<b><font color="#cc0000">"Heavy Quarkonium Production at Hadron
Colliders"
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Prof. Guangda Chao<br>
Peking University, China
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Abstract: One of the long standing challenging problem in heavy
flavor physics is the production of heavy quarkonia at hadron
colliders. The J/psi and psi' production cross sections at high p_T
observed by CDF at the Tevatron are about two orders of magnitude
larger than conventional QCD predictions. In the framework of
nonrelativistic QCD (NRQCD), the color-octet gluon fragmentation
might increase the cross sections, but the predicted trasverse
polarizations of J/psi and psi' are in contradiction with the
measurements. We show that the next-to-leading order (NLO) QCD
corrections including both the color-singlet and color-octet
channels may essentially change the large p_T behavior of J/psi, and
that the predicted cross sections can be in good agreement with the
Tevatron data and the newly observed LHC data at large p_T.
Moreover, the J/psi polarization puzzle may also be explained.
However, we find that the long-distance matrix elements (LDMEs)
extracted from hadron colliders are not compatible with that
extracted from the e+e- annihilation data observed by Bell at the B
factory. Possible reasons for this disagreement are suggested.
Furhther theoretical investigation and experimental measurement are
also needed. Puzzles in the P-wave charmonium states chi_cJ are also
discussed.
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The seminar is based on the work: Phys.Rev.Lett.106,042002(2011),
Phys.Rev.D83,111503(2011), Phys.Rev.D84,114001(2011),
Phys.Rev.Lett.108,242004(2012), Phys.Rev.D85,114003(2012) as well as
some previous works.
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