Tetraquarks - Evidence Grows!

Ahmed Ali (DESY)
Building 1b, Seminar Room 4a/b: 17:00

The idea that diquarks and antidiquarks play a fundamental role
in hadron spectroscopy leading to bound tetraquark states goes
back well over thirty years. However, it is only during the last
several years that experimental evidence and theoretical
reasoning gathered renewed momentum. There exists now
a prima facie case for the exotic hadrons X(3872), Y(4660)
(and some others) being tetraquarks. We briefly discuss them
but concentrate on the recent interpretation of the Belle anomaly
observed at the KEK-B factory in the processes
e+e− → Υ(1S)π+π− and e+e− → Υ(2S)π+π− in terms of the
bound b ̄b tetraquarks Yb. The anomalously large
rates and dipion invariant mass distributions measured by Belle,
which defy conventional QCD, are naturally explained in the
tetraquark framework. Some consequences for experiments
at the B factories and hadron colliders, Tevatron and the LHC,
will be discussed.

application/pdf DESY Seminar_Ali.pdf (9.8 MB)
DESY Seminar_Ali.pdf