Searching for Finding the 1 exotic meson

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Searching for (Finding ? ) the 1- exotic meson
Adam Szczepaniak Indiana University
Theoretical expectations Existing candidates
Previous (E852) hp and hp analysis Meson-meson
interactions Results of new analysis
Collaborators Alex Dzierba Scott Teige Maciej
Swat (PhD thesis)
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JPC 0 0 1 1 2
Normal mesons
JPC 0 0 1 2
Exotic mesons
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Light exotic meson
Lattice predictions
Lacock Schilling

• JPC 1- lowest state
• Higher masses difficult to resolve
• Chiral extrapolations 100-200 MeV

AW Thomas, AS (01)
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Decays

• Normal widths !

In large NC same as for ordinary mesons O(1/NC)
T. Cohen (98)

• Unusual decay modes !

Isgur, Kokosy, Paton (85) Page, Swanson, AS (99)

• Low lying states expected
• below string breaking !

Juge, Kuti, Morningstar (99) Bali (00)
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Quantum Numbers for Hybrid Mesons
Excited Flux Tube
Quarks
Hybrid Meson
like
like
So only parallel quark spins lead to exotic JPC
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M.Swat, AS
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p- (18GeV) p ? X p ? h p- p
? h p- p
30 000 events
Nevents N(s, t, Mhp , W)

• Measure Nevents/bin
• Correct for detector acceptance
• Fit theory

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S0, PM, DM Partial Wave Amplitudes
HLM Moments
PWA are ambiguous Moments are not
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• Goals
• 1. Understand the mass dependence of the produced
  hp and hp
• Is there a P wave 1- exotic quantum
  numbers
• Is it resonant
• Compare with existing resoances in S and D
  waved
• 2. Understand the production mechanisms
  (t-dependence)

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Global features of the hp0, hp-, hp-
production
hp0 (Maciek)
Mass dependence
t-dependence
Relevant partial waves S D0 D- Po P-
(unnatural) D P (natural)
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Previous (E852) analysis (hp-)
M1,0
PM
h
p-
Assume a P-wave BW resonance is produced
po
p
n
but look only P (PM1 PM-1) wave
combination !
However, even if other M-combinations of the
resonance have different production mechanisms
(t-dependence, intensity), if nonzero (data
would tell us that) should have the same mass and
width !
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Apply previous assumptions to the hp0 data
p1(1400) with G 200 400 MeV emerges (just
like in hp-)
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E852 hp- analysis
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Assume BW resonance in all, M1,0, P-waves
p1(900 5GeV) emerges
Intensity in the weak P-waves is strongly
affected by the a2(1320), strong wave due to
acceptance corrections
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Summary of hp0 and hp- experimental results

• The a0(980) and a2(1320) are clearly seen.
• The Breit-Wigner parameterization reproduces
  PDG values
• and production mechanisms are well understood.

The question remains what is the nature of
this wave.
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Meson-meson interactions and QCD resonances
A pole of the S-matrix (far less a BW resonance)
in general cannot be dirrectly identified with
a quark state.

• Strong inter-channel coupling shift masses
• Non-resonant backgrounds may produce poles

Use phenomenology (QCD, symmetries)
constraints (analyticity, unitarity)
to trace the dynamical origin of S-matrix
singularities
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The model
Use c-symmetry guided low-energy expansion
QCD states
Residual interactions
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Illustration pp (SI0)
pp
2 Resonaces _at_ 1.3, 1.5 GeV
ppKK
pp only (no KK, no resonances)
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hp and hp (I1)
J 0 a0(980), a0(1400) ? KK, hp,hp
chiral coupled channels
1 resonance ( a0(1400)
) J 1 exotic ? ? hp,hp
chiral coupled channels
0 or 1 resonance J 2
a2(1320) ? KK, hp,hp chiral
coupled channels
1 resonance ( a2(1320) )

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hp
Mhp
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Conclusions
Out of three exotic meson candidates two can be
accounted for as backgrounds gtgt hp(1400),
hp(1600) The exotic p1(1600) in rp will be
reanalyzed gtgt 100 times more data at hand
It could be weakly present in the hp(1600)
channel gtgt t-dependence
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hp
hp
fP-fD
P2