QCD Spectroscopy

1
QCD Spectroscopy a.k.a. Hadron Spectroscopy
Why is it interesting? What can we measure? How
can we measure those things? Hadron
classes Event classes Uniqueness of CDF
2
QCD is the theory of strong interactions Testable
directly only for where
, perturbative At small many
approaches, with limits and approximations Latti
ce Gauge Theory LGT Small volumes ( hadron
size) Discrete spacetime, take limit l ? 0,
computation intensive String models flux
between qs collapses to tube ? string Potential
models etc (bags, solitons, skyrmions,...)
LGT probably best we have for hadron masses
3

• What is interesting to measure ( we can)?
• find new states (and there are many)
• measure masses as precisely as possible
• measure widths/lifetimes
• study decay modes
• study production features

4
CDF Unique
Highest energy Particle ID Good mass
resolution High statistics possible
TOF
dE/dx
5
How? Large numbers of stable states to combine
with charge conjugates and different Q
combinations large matrices
Some seem particularly interesting
We can search for partners, e.g. Dmitry Litvintsev
But also consider broad sweep (just computer
time?)
6
Those with heavy quarks are particularly CDF
territory Also more amenable to LGT
calculations Picking quarks out of the bag
Many exotics, some hard to see, but with high
statistics ??
7
Stringy Hadrons
Mesons, Hybrid, Glueball, Baryon,
Antibaryon Baryonium 2 types? Exotics e.g.
Pentaquarks
Meson Hybrid Glueball Baryons
Baryonium Pentaquarks ?
8
Exotic Baryons
Even without b-hadrons
There are many baryons with strange and charmed
quarks. Many not yet seen (ccc) To say nothing
of the bs bcs, bbc, bbb Can you think of any
better way of producing and studying these than
CDF with gt 109 events? Not just stamp
collecting, hadrons test non-perturbative
QCD (Lattice or otherwise)
9
Hyperons Y and heavy flavor baryons
Nice hyperon signals in Run 2 data with 2-track
trigger. High p_T ... small acceptance. Looking
now in 0-bias data. Best hope of finding most
exotic states Measure masses, lifetimes, BRs
SELEX doubly charmed baryons ?
10
CLAS (JLabI)
SPRing-8
CLAS (JLabI)
SAPHIR
HERMES
DIANA
11
Thin evidence, but think of the environment!
12
Tetraquarks scalar nonet
13
Beautiful in exclusive DPE, but anyway
Interesting Channel
only new qs
Initial state must be glue
FNAL E690 800 GeV/c p PWA 2 waves, 0
2
Lindenbaum et al, BNL Claim 3 states, all 2
14
Event Classes
Looking for (eg) peaks in can use all
CDF events Probably want to subdivide
(0-biasmin-bias) (high pT/other) There are
also special regions of phase space eg Hadron
cluster between two rapidity gaps gt 3 (glue
rich) Leading hadrons in jet (in principle, but
no ID and poor dM) Low pT (lt 1GeV) vs high pT
(gt 1 GeV)
Probably good to start with all 0-biasmin-bias
15
Remarks
There are perhaps many new hadrons waiting to be
discovered This physics had a strong revival in
2003 It is very relevant for understanding
strong interactions We should try to be first
not second This might be a great field for good
undergraduates/students