Exclusive Vector Meson Production and

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Exclusive Vector Meson Production and Inclusive
K0SK0S Final State in DIS at HERA
Photon2003, Frascati 07-11/04

• Outline
• Exclusive vector meson production
• Summary
• First observation of resonances in inclusive
• KS0KS0 final state in DIS
• Summary

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At HERA
VM r, w, f, J/y , y(2S), etc
q
VM
VM (MVM)
P
soft
hard
x1/W2
Gluon from fit to F2 scaling violation ?
At low t ?
Transv. size of the interaction region
Small size. No W dependence.
3
A first look

• Fit s µ Wd
• 0.22 for r0, w, f
• 0.8 for J/y

4
J/? Photoprod. in bins of W and comparison to LLA
calculations
Looking at high MVM (consistent with hard regime
? previous slide)
Leading Log. Approx. (LLA) pQCD with different
gluon parametrisations
Models sensitive to input parametrisation of the
gluon density
Indeed, MVM is a hard scale
5
Can Q2 provide a hard scale?
And the power-law W? dependence? ?
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Can Q2 provide a hard scale?
J/y already steep at Q2 0

• Data fitted with Wd
• pQCD models consistent
• with data

Q2 also provides a hard scale.
7
Photoproduction of proton-dissoc. VM at high t
What about t?
?p ? ?Y
?p ? ?Y
?p ? J/?Y
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Summary

• Q2 , MVM2 and t set a hard scale.
• Perturbative QCD predictions agree with data

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• QCD predicts the existence of hadrons made up by
  gluons (glueballs). From Lattice QCD
  calculations, the lightest glueball has JCP0
  with a mass 1730100 MeV.
• KS0KS0 couples to meson states with JCP(even)

Tensor JCP2 Nonet
K2(1430)
K2(1430)
0

f2(8)
f2(1)
a2(1320)
a2(1320)
-

a2(1320)
0
K2(1430)
K2(1430)
-
0
3 candidates for 2 spots
Scalar JCP0 Nonet
K0(1430)
K0(1430)
0

f0(8)
f0(1)
a0(????)
a0(????)
-

a0(????)
0
f0(1710) is a glueball candidate
K0(1430)
K0(1430)
-
0
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Þ A total luminosity of 121 pb-1 was used Þ
Only events with at least 2 KS0 were selected Þ
Clean KS0 sample
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• First observation of JCP(even) in DIS. Two
  states are observed
• a state consistent with f2(1525)
• X(1726) (is this the f0(1710) ?)
• A third state is observed in the (problematic)
  1300 MeV mass region, consistent with the
  f2(1270)/a2(1320) interference

Several states have been observed in the 2GeV
region (see PDG02)
M. Barbi
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Þ KS0KS0 in the Breit-frame
Increasing xp More gluons
Pz(KsKs)lt0 (7) Pz(KsKs)gt0 (93)
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Summary

• First observation of resonances in KS0KS0
  final state
• in DIS was reported
• Two states are observed in the 1300 MeV, 1500
  MeV
• mass region consistent with
  f2(1270)/a2(1320) and f2(1525)
• Another state X(1726) is observed, probably
• the f0(1710) (a glueball candidate)
• States are produced in a gluon rich environment

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e'
e'
e
e
g
g
VM
VM (MVM)
Wgp
P
P
p'
p
p
Y (MY)
Elastic
Proton Dissociative
Q2 g virtuality Q2 lt 100 GeV2 Wgp
gp CMS energy 20 lt Wgp lt 290 GeV t
4-mom. transf. squared t lt 20 GeV2 VM r,
w, f, J/y , y', U R 1/ z(1-z) Q2 mq21/2
z Eq / Eg
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Photon transversally polarized low Q2 or t
( Donnachie-Landshoff )
( Shrinkage )

• s rising weakly with W

At low t, t lt 1.5 GeV2 d 0.22

• s steep exponential t dependence (shrinkage)

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Photon mainly longitudinally polarized Large Q2 ,
MVM or t qq system is small, probes
the proton
Two-gluon-exchange approach at LO
Gluon ladder (LLA approach)
Gluon from F2 scaling violations
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Dependence at large t not exponential
J/y
Þ indication that large t may provide a
hard scale to apply perturbative QCD
Forshaw and Poludniowski fitted the ZEUS data for
p-dissociative photoproduction of r0, f and J/y
mesons (hep-ph/0107068)
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Þ QCD models FKS and MRT(CTEQ5M) are in good
agreement with data
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-gt Cross-section suppressed with respect to that
of J/y -gt Steeper W dependence
y(2S) wavefunction has a node
-gt Overall R 0.166 consistent with pQCD
prediction -gt Fit WDd ? Dd 0.24 consistent
with W dependence for
y(2S)
21
J/y already steep at Q2 0
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Extras.. KsKs final state
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Scalar and Tensor Mesons
Quark Model (u,d,s)
Scalars
JPC 0
S1
I0
S
q
q
L1
JPC 2
I
Tensors
P (-1)x(1)x(-1)L (-1)L1 C (-1)LS J 0
or 2
Masses 1-2 GeV, scalar and tensor mesons much
heavier than the pseudoscalars
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QCD richer than Quark Model, predicts gluon
states with JPC 0,2, I0
Is this a qq state?
mix
g
f0(1370) f0(1500) f0(1710)
Observed States
Ks has SL0, P-1, C1 KsKs has P1, C1 g
Jeven
KsKs final state couples only to JPC(even) and
it is CLEAN. This is the golden channel (given
statistics) to look for scalar and tensor meson
resonances
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Production mechanisms in DIS
Odderon Exchange
Gluon poor processes
VM Radiative decays
Gluon rich processes
In quark Jets
In gluon jets
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Fit 3 Breit-Wigner and a backg. function
Problematic region
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Observation of Jeven meson resonances in ep
cosKK lt 0.92 cut
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Þ Attempt to include the 1980 MeV mass region
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How well a smooth background describes the data
It is less than 1 likely that a
smooth distribution describes the data.
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ee-ggggKsKs
If f(1710) is a glueball it should have small
coupling to gg