Lake Louise Winter Institute 2004 Alberta, Canada 15 – 21 February. Meson and Baryon Spectroscopy at HERA. McGill University DESY. Mauricio Barbi. Introduction Neutral Meson Spectroscopy K s K s resonances in DIS K s p resonances in DIS Summary. for. Collaborations.
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Lake Louise Winter Institute 2004
Alberta, Canada
15 – 21 February
Meson and Baryon Spectroscopy at HERA
McGill University DESY
Mauricio Barbi
for
Collaborations
mesons
baryons
q
q
q
q
q
Introduction
Lake Louise, Alberta, CA.
central rapidities
Inclusive Photoproduction of , 0, f0(980) and f2(1270)  H1
energy as at RHIC, but in light
hadron collisions.
an average photonproton CM energy
of 210 GeV
Lake Louise, Alberta, CA.
(LAr Calorimeter)
H1 preliminary
3<pT<8 GeV, y<1
dN/dM [1/GeV]
η
Fit with 1 gaussian + polynomial bkg
M [GeV]
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ö
G
m
m
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m
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3
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ç
÷
0
,
i
i
=
+
F
(
m
)
A
ç
÷
2

+
G
2
2
2
2
(
m
m
)
m
(
m
)
è
ø
Mγγ[GeV]
=
1
i
0
,
0
,
i
i
i
(
)
å
2


a

+
a
m
a
m
a
m
2
m
e
(Re
f
(
m
))
2
3
4
p
1
Invariant Mass Distribution
Rapidity limited to y<1
H1 preliminary
0, f0, f2+
(Central Jet Chamber)
ρ0
y<1
Comb bg
Fit with 3 relativistic BWs, a bkg function and reflection contribution mainly from and K*.
K*
f0
f2
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ρ0
f0
f2
η
Differential cross section as a function of rapidity (y) and PT
Differential cross sections
compatible with
thermodynamic
based approach.
H1 preliminary
H1 preliminary
d/dy [nb]
d /(dydpT2) [nb/GeV2]
y
pT [GeV]
Lake Louise, Alberta, CA.
H1 preliminary
1/(2j+1)d/(dydpT2) [nb/GeV2]
ρ0
f0
f2
η
+
(published)
m + pT [GeV]
Differential cross sections as a function of
( mass + PT )
support universality of longlived hadron production.
Lake Louise, Alberta, CA.
f0(1)
0
s
Scalar JPC=0++Nonet
K0(1430)
K0(1430)
0
+
f0(8)
0
f0(1370) ~ uu+dd
f0(1500) ~ ??
f0(1710) ~ ??
f0(8)
0
s
s
f0(1)
a0(????)

a0(????)
a0(????)
+
0
3 candidates for 2 spots
f0(1710)is a glueball candidate
K0(1430)
K0(1430)

0
K SK S resonances in Deep Inelastic Scattering (DIS) at HERA  ZEUS
Lake Louise, Alberta, CA.
0
0
s
s
SVTX
0
K
s
VTX
p
Kinematical region limited by event selection requirements and limit for HERA running with 920 GeV protons.
Integrated luminosity of 121 pb1 (19962000 data);
Use the ZEUS Central Tracker Detector
Q2= photon virtuality
x = Bjorken scaling variable
y = fraction of the lepton energy
transferred to the proton in
the proton rest frame
Take only K in the region of 10 MeV around the fitted K mass;
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Fit with 3 modified relativistic BreitWigners and a background function.
interference.
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0
s
Current
93% of the
KsKs pairs
are in the target region
Target
0
s
93% of the K K production is in a region where sizeable initial state gluon radiation may be expected.
Lake Louise, Alberta, CA.
mass
width
mass
width
PDG 2002 values (MeV)
f0(1710) :
f2’(1525) :
L3
Phys. Lett. B501 (2001) 173182
BELLE
hepex/0104024
BES
hepex/0307058
Confronting L3, BELLE, BES and ZEUS
ZEUS
Accepted by Phys. Lett. B
Hepex/0308006
1700 MeV mass region
L3: mass 1767±14 MeV; width 187±60 MeV
BELLE: mass 1768±9.6 MeV; width 323±29 MeV
BES: mass 1722±17 MeV; width 167 MeV
ZEUS: mass 1726±7 MeV; width 38 MeV
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Antidecuplet
1530 MeV
1710 MeV
1890 MeV
2070 MeV
Lake Louise, Alberta, CA.
K+n
resonances in inclusive
DIS, using 121 pb1 of
ZEUS data.
K0 reconstruction similar
to those in KsKs analysis.
Detector dE/dX to
select (anti)proton.
Preliminary
p
K±
p±
Lake Louise, Alberta, CA.
Preliminary
372±75 candidates
Peak at 1527±2(stat) MeV
Width of 10±2(stat) MeV
Significance of ~5s
Fit: Gaussian + P3 (free parameters)
Lake Louise, Alberta, CA.
S(1480)???
S(1480)???
126±50 candidates
Peak at 1529±3(stat) MeV
Width of 7±3(stat) MeV
Preliminary
Preliminary
393±86 candidates
Peak at 1523±3(stat) MeV
Width of 16±3(stat) MeV
Lake Louise, Alberta, CA.
Experiment
M (MeV)
Significance
G (MeV)
SPring8 1540 10 5 < 25 (4.6s)
DIANA 1539 2 “few” < 9 (4.4s)
CLAS (d) 1542 2 5 21 (5.3s)SAPHIR 1540 4 2 < 25 (4.8s)
ITEP (v’s) 1533 5 < 20 (6.7s)
CLAS (p) 1555 1 10 26 7 (4.3s)
HERMES 1528 2.6 2.1 19 5 2 (5.6s)
ZEUS (Prel.) 1527±2 10±2 (5.0s)
Lake Louise, Alberta, CA.
Three results were reported in hadron spectroscopy:
f0(1710)(glueball candidate). More stat. is needed to establish its width;
consistent with the predicted Q+ pentaquark;
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Extras….. KsKs final state
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Summary
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0
s
0
s
Lake Louise, Alberta, CA.
Lake Louise, Alberta, CA.
0
s
0
0
s
s
K SK S resonances in Deep Inelastic Scattering (DIS) at HERA  ZEUS
Some production processes at HERA
Quark jets
Odderon exchange
Radiative VM decay
Gluon ladder
Lake Louise, Alberta, CA.
ZEUS Detector
RCAL
CTD
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Q2= photon virtuality
x = Bjorken scaling variable
y = fraction of the lepton energy transferred to the proton in the proton rest frame
p
DIS variables
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0
0
s
s
SVTX
0
K
s
VTX
Lake Louise, Alberta, CA.
0
0
s
s
K
K
0
0
0
0
0
0
0
0
s
s
s
s
s
s
s
s
K K system does not open at threshold
meson fJ
Remove enhancement at K K invariant mass threshold due to the presence of the f0(980)/a0(980) state.
2553 K K candidates found in the range
0.995 < M(K K ) < 2.795 GeV
Lake Louise, Alberta, CA.
Current region in DIS is
equivalent to an e+e hemisphere
Breit Frame
Current
93% of the
KsKs pairs
are in the target region
Target
0
0
s
Pz(KsKs)<0
s
93% of the K K production is in a
region where sizeable initial state gluon
radiation may be expected.
Pz(KsKs)>0
Lake Louise, Alberta, CA.
PDG 2002 values (MeV)
mass
width
mass
width
ZEUS fit values (MeV)
2/N
width
events
mass
width
events
mass
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central values of rapidity
H1prel. Data vs MC (selected events)
Inclusive photoproduction of
neutral hadronic resonances:
, 0, f0(980) and f2(1270)
Ntrack
θtrack
Ecluster [GeV]
Rtransv [cm]
Dtrackcluster [cm]
cos α
Test universality of hadroproduction
Lake Louise, Alberta, CA.
good agreement
ρ0
ρ0
f0
f0
f2
η
f2
+
η
H1
Differential photoproduction cross sections
H1 preliminary
1/(2j+1)d/(dydpT2) [nb/GeV2]
d/dy [nb]
d /(dydpT2) [nb/GeV2]
(published)
y
pT [GeV]
meson mass + pT [GeV]
2000 data: 39 pb1
ylab < 1
<Wp> = 210 GeV
Same behaviour as for light, longlived hadrons
Lake Louise, Alberta, CA.
Quark Model
(u,d,s)
Scalars
JPC = 0++
S=1
I=0
S
q
q
L=1
JPC = 2++
I
Tensors
P = (1)x(+1)x(1)L = (1)L+1
C = (1)L+S
J = 0 or 2
Masses 12 GeV, scalar and tensor mesons much heavier than the pseudoscalars
Lake Louise, Alberta, CA.
QCD: richer than Quark Model, predicts gluon states with JPC = 0++,2++, I=0
Is this a qq state?
mix
g
f0(1370)
f0(1500)
f0(1710)
Observed States
Ks: has S=L=0, P=1, C=+1
KsKs: has P=+1, C=+1 g J=even
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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TensorJPC=2++ Nonet
f2(1270) ~ uu+dd
f2(1525) ~ ss
f2(8)
K2(1430)
K2(1430)
0
+
f2(1)
f2(8)
f2(1)
a2(1320)

a2(1320)
a2(1320)
+
0
K2(1430)
K2(1430)

0
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Odderon
Exchange
Gluon poor processes
VM Radiative
decays
Gluon rich processes
In quark Jets
In gluon jets
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ArmenterosPodolanski variables
Photon conversion
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2/N
width
width
events
mass
width
events
mass
widh
events
mass
events
mass
PDG 2002 values (MeV)
Lake Louise, Alberta, CA.
Current region in DIS is
equivalent to an e+e hemisphere
Breit Frame
78% of the
KsKs pairs
have xp>1
Increasing
xp
More gluons
Pz(KsKs)<0 (7%)
Pz(KsKs)>0 (93%)
High xpcorresponds to production in a
region where sizeable initial state gluon
radiation may be expected.
Lake Louise, Alberta, CA.
KS0KS0 final state in DIS
Several states have been observed in the 2GeV region (see PDG02)
f0(980)/a0(980) gives Ks pair with very small opening angle in the lab.
We would like to remove collinear Ks pairs and then fit the spectrum.
Threshold Enhancement
due to f0(980)/a0(980)
Fit 3 BreitWigner and a backg. function:
Problematic
region
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Observation of J=even meson resonances in ep
cosKK < 0.92 cut
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KS0KS0 final state in DIS
Fit with 4 BreitWigner
Þ Attempt to include the 1980 MeV mass region
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It is less than 1% likely that a smooth
distribution describes the data.
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If f(1710) is a glueball it should have small coupling to gg
Lake Louise, Alberta, CA.