Hybrids and Glueballs in the light
of antiproton reactions
pBar Workshop
GSI, 5.4.2002
Klaus Peters
Ruhr-Universität Bochum
Light Mesons are complicated

naive quark-antiquarkpicture is wrong for
light mesons

“leading“ meson-term is
only the simplest of many
Fock-states

exception:
narrow states
(small mixing of states)
exotic quantum numbers
(reduced density of states)
5.4.2001
Klaus Peters - pBar Workshop - GSI
Spectroscopy of Light Mesons

No/small problem with
statistics

Interpretation biased by
models
(poles, couplings)

Problem: interpretation
of measured states
less precise predictions
density of states
width of states
mixing of states
5.4.2001
Klaus Peters - pBar Workshop - GSI
Exotic-Production via FSI
5.4.2001
Klaus Peters - pBar Workshop - GSI
LQCD-Potentials

Comparison between
quenched/unquenched
shows compatibility for
bbBar-Potentials

sfD(stat) = 1%
unquenched calc:
200 PCs for 3 months

Vital field
with large algorithmic
improvements and
improved systematic
corrections
5.4.2001
Klaus Peters - pBar Workshop - GSI
Gluonic Degrees of Freedom - Hybrids

Gluonic excitations of the
quark-antiquark-potential
may lead to bound states

LQCD:
mH ~ 4.2-4.5 GeV

Light charmed hybrids
could be as narrow as
 O(5-50 MeV)
selection rules
small # of charmed
final states (Zweig-Rule)
5.4.2001
Klaus Peters - pBar Workshop - GSI
Charmed Hybrids

Fluxtube  DD** , but if
mH<4,29 GeV  GH<50 MeV
CLEO-II BJ/yfK(S)(±)

Some exotics can decay
neither to DD nor to DD*

e.g.: JPC(H)=0+fluxtube allowed
J/yf2, J/y(pp)S,h1ch
fluxtube forbidden
cc0w,cc0f, cc2w,cc2f, hch1

Small # of final states with
small phasespace
5.4.2001
Klaus Peters - pBar Workshop - GSI
Density of states (e.g. for Vector Mesons)

Light mesons have
usually larger widths

Since NQ=3 for (uds)
combinatorics yields
very many states

Ideal: charm-Sector
with a much reduced
density of states
5.4.2001
Klaus Peters - pBar Workshop - GSI
Exotic Production in Proton-Antiproton

High production yields
for exotic mesons
(or with a large
fraction of it)
f0(1500)p  ~25 % in 3p0
f0(1500)p  ~25 % in 2hp0
p1(1400)p  >10 % in pp0h

Interference with other
(conventional) states is
mandatory for the phase
analysis

Exotics are present !
5.4.2001
Klaus Peters - pBar Workshop - GSI
Hybrid Formation in
in Proton-Antiproton

Gluon rich process creates
gluonic excitation directly
since ccBar requires the quarks to
annihilate (no rearrangement)
yields comparable to
production of excited charmonium

2 complementary techniques

Momentum for an complete
survey
p~15 GeV
Formation
(Broad- and Fine-Scans)
Production
(Fixed-Momentum)
5.4.2001
Klaus Peters - pBar Workshop - GSI
Mass regions and p momentum

Neccesary momentum
span is driven by the
charm-exotics

Hybrids (HC)
HC non-exotic JPC
Formation 10 GeV/c
HC exotic JPC
Production 15 GeV/c

Perfect
Resolution
+Recoil-Particle
+Phsp.
D(s)-Hybrids
DsDs+1 GeV/c ~12 GeV/c

Charmed Multiquarks (MC)
MCl+l- 15 GeV/c
5.4.2001
Klaus Peters - pBar Workshop - GSI
Gluonic Degrees of Freedom - Glueballs


Light gg/ggg-systems are
complicated to identify
Exotic heavy glueballs
m(0+-) = 4140(50)(200) MeV
m(2+-) = 4740(70)(230) MeV




Width unknown, but!
nature invests more likely in
mass than in momentum
Flavour-blindness predicts
decays into charmed final states
Same run period as hybrids
In addition:
scan m>2 GeV/c2
5.4.2001
Morningstar und Peardon, PRD60 (1999) 034509
Morningstar und Peardon, PRD56 (1997) 4043
Klaus Peters - pBar Workshop - GSI
4-Quark Formation with DiLepton-Tag

Proton-Antiproton
contains already a
4-Quark-System

Idea: Dilepton-Tag from
Drell-Yan-Production

Advantages
trigger
less JPC-Ambiguities
1200 E./day @ 12 GeV/c
300 E./day @ 5-8 GeV/c
antiproton-Beam
(for L=1032cm-2s-1)
5.4.2001
Klaus Peters - pBar Workshop - GSI
Lessons from LEAR
 Full solid angle
no missing particles (photons!)
 Low threshold
electromagnetic detector
 KS-Trigger
cosq
3p0
Emin Eg
 Kaon ID @ high Energies
5.4.2001
Klaus Peters - pBar Workshop - GSI
Annihilation in Flight – no longer a challenge!
Peters, NPA 692 (2001)295


Crystal Barrel has prooven
that the annihilation in
flight can be analyzed
unambiguously
Formation:
twobody decays, where at
least one particle carries spin!

Production:
integration of the production
process or
small recoil momenta may
reduce the available phsp. and
the contributing waves
dramatically
5.4.2001
Klaus Peters - pBar Workshop - GSI
Channels, Signatures, Potential Problems
 “Leading charmonia”
J/y, y‘, h(‘)c, ccj [DDbar] a.o.m.?
 DiLeptons
e+e- (Ecal,Trk) [c.m.:
m+m- (Trk,Hcal)
usually fast, but slow for 4-Quark-Tag]
 Photon-Pairs
gg from ccBar (Ecal,no-Trk)
gg from p0 and h (Ecal)
 f (f)-Tag
ff and recoil f (Trk,Cherenkov)
Most information needed on trigger level !
5.4.2001
Klaus Peters - pBar Workshop - GSI
Required Features
 “Usual” omni purpose features
 Forward spectrometry: cosq  1
for low multiplicity charged final states
[low and medium energy scans]
 Mandatory!
“Fast” particle id (guess) for trigger purposes
[hard and/or soft]
 Threshold Cherenkov?
In addition to a multi purpose device (DIRC)?
5.4.2001
Klaus Peters - pBar Workshop - GSI
Summary
 Exotics are present in
proton-antiproton reactions
 Light exotics are complicated
to measure and to classify
 Heavy exotics will show a clearer signature
 Charged and neutral tracking together with
efficient particle id e±/p± m±/p± and p±/K±
and V0-finder is mandatory
 Exclusiveness with flat efficieny
for the full solid angle
5.4.2001
Klaus Peters - pBar Workshop - GSI