φ-meson photoproductionNew results from LEPS/SPring-8
APPEAL SeminarSeptember 8th, 2004
Tsutomu Mibe
Ohio universityfor the LEPS collaboration
Ohio University and Jefferson lab.
Jefferson laboratoryNewport News, VA
Ohio UniversityAthens, OH
U.S.A
Outline
Physics motivationExperiment at LEPS/Spring-8Data analysisResults and discussionsSummary
Vector Meson Photoproduction
γ
pπ,η,σ・・・
ρ, ω
γ
p
ρ, ω,φ
uudPomeron
ρ, ω, φ (~ss)
γ
p uud???
Pomeron exchange
Meson exchange
0+ Glueball exchange ??
hep-ph/0302195,0211430
Glueball hunt by φ meson photoproduction
T. Nakano and H. Toki,(in proceedings of EXPAF’97)
( )⎟⎟
⎠
⎞
⎜⎜
⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛ −+⎟⎟
⎠
⎞⎜⎜⎝
⎛ −⎟⎟⎠
⎞⎜⎜⎝
⎛==→
δ
γ
φφγσ
0
16.0
0
2
22)0(
susa
sus
pp
Ctppdtd
Data from DESY(1978),Bonn(1974)
Pomeron + Daughter Pomeron
Pomeron only
Pomeron + Daughter Pomerona=0.63, δ =-3.46
Pomeron Glueball (Jp =2+)
Daughter Pomeron Glueball (Jp =0+) ??
γ+p →φ+p
Application of Regge phenomenology to Daughter pomeron trajectory.
γp →ρp
γp →φp
Ordinary meson exchange
M.A. Pichowsky and T.-S. H. LeePRD 56, 1644 (1997)
Prediction from Pomeron exchange
Prediction from meson exchange
Data from: LAMP2('83), DESY('76), SLAC('73), CERN('82),FNAL('79,'82), ZEUS('95,'96)
Polarization observables with linearly polarized photon
Decay Plane // γnatural parity exchange (-1)J
(Pomeron, 0+ glueball,Scalar mesons)
Photon Polarization
K+
K+
K-
Decay Plane γunnatural parity exchange -(-1)J
(Pseudoscalar mesons π,η)
εγ
εγ
Relative contributions from natural, unnatural parity exchanges
Decay angular distribution of φ meson
φ →K+K-
K-
Decay angular distribution of φ meson
θ
K+
K-
γ
p’
φ meson rest frame (Gottfried-Jackson(GJ) frame)
φ
K+
K-
εγ
ΦProduction
planez
Decayplane
z-axis
φ-Φ
φK+ - Φpol (degree)
SLAClinear pol. , Eγ=2.8,4.8 GeV(J. Ballam et al. PLD 7 (1972)3150)
53 events in Eγ=2.8,4.8 GeV
BonnUnpol, Eγ=2.0 GeV (NP B70(1974)257)
CLAS @J-labUnpol, Eγ=3.3-3.6 GeV (PRL85(2000)4862)
(hep-ex/0311024 )Unpol, linear pol. data at Eγ=1.6-2.5 GeV
SAPHIR @ELSA/BonnUnpol, Eγ=1.6-2.6 GeV (EPJ A17(2003)269)
Available data
New measurements near threshold at LEPS @SPring-8
linear pol. , Eγ=1.6-2.4 GeVHelicity frame
Super Photon ring-8 GeV SPring-8
• Third-generation synchrotron radiation facility• Circumference: 1436 m• 8 GeV• 100 mA• 62 beamlines
LEPS collaboration
Academia Sinica, TaiwanW.C. Chang, D.S. Oshuev, C.W. Wang, S.C. WangChiba University, JapanH. Kawai, T. Ooba, Y. ShiinoInternational Institute for Advanced Studies H. EjiriJAERI, JapanY. Asano, N. Muramatsu, A. I. Titov, R.G.T. ZegersJASRI, JapanS. Date, N. Kumagai, Y. Ohashi, H. Ookuma,H. Toyokawa, T. YoritaKonan University, JapanH. AkimuneKyoto University, JapanK. Imai, T. Ishikawa, M. Miyabe, M. Niiyama, M.
YosoiNagoya University, JapanY. Miyachi, A. WakaiUniversity of Minnesota
P. Shagin
Miyazaki University, JapanT. Matsuda, Y. ToiOhio University, U.S.K. Hicks, T. MibeOsaka University, JapanH. Nakamura, M. Nomachi, A. Sakaguchi,Y. Sugaya, M. SumihamaPusan National University, S.KoreaJ.K. Ahn, D.S. AhnRCNP, Osaka University, JapanH. Fujimura, M. Fujiwara, T. Hotta, K. Horie, K. Kino, H. Kohri, T. Matsumura, N. Matsuoka, M. Morita, T. Nakano, T. YoritaSaskatchewan University, CanadaC. RangacharyuluTohoku University, JapanH. ShimizuWakayama Med. University, JapanS. MakinoYamagata University, JapanT. Iwata
The LEPS facility
Linearly polarized photon
Ar ion laser (Coherent)Wavelength 336-351nm(multi-line)Power(typ.) 5W
λ/2 plate Polarizationrotator
Beam expander
To storage ring
Mirrors GeV photonIntensity(typ.) 106 /secLinear polarization 95% at 2.4 GeV
The tagging counter
Storage ring
Laser beam
GeV photon
Recoiled electron
Tagging counterplastic scintillators + 100µm-pich SSDTagging region 1.5 <Eγ<2.4 GeVEnergy resolution 15 MeV
Interaction region
Dipole magnet
Charged particle spectrometer
1m
TOF wall
MWDC 2MWDC 3
MWDC 1
Dipole Magnet (0.7 T)
Liquid Hydrogen Target
Start counter
Silicon VertexDetector
AerogelCerenkov(n=1.03)
γ
• Trigger condition : TAG*STA*AC*TOF• Run period
2000, Dec. – 2001, June (50mm-long LH2 target)2002, May – 2003, Apr (150mm-long LH2 target)2002, Oct. – 2003, June (150mm-long LD2 target)
• The first data set with 50mm-long LH2 target– Total number of trigger
1.83*108 trigger (48% Horizontal, 52% Vertical pol.)– Number of events with charged tracks
4.37*107 events
Summary of data taking
Charged particle identification
10
10 2
10 3
0
0.5
1
1.5
2
2.5
0.1 0.2 0.3 0.4 0.5 0.6 0.7
Mass(GeV)M
omen
tum
(GeV
)
K/π separation (positive charge)
K+π+
1
10
10 2
10 3
10 4
10 5
-1 -0.5 0 0.5 1 1.5 2 2.5
Mass/Charge (GeV)
Eve
nts
Reconstructed mass
d
pK+
K-
π+π-
σ(mass) = 30 MeV(typ.) for 1 GeV/c Kaon
Charged particle identification
•KKp mode•K+ track•K- track•proton track
•K+K- mode•K+ track•K- track
•K+p mode•K+ track•proton track
•K-p mode•K- track•proton track
LEPS spectrometer
K+
K-
p
p
γp φp K+K-p
K-
K+
0
10
20
30
40
50
60
70
80
90
0.6 0.8 1 1.2 1.40
200
400
600
800
1000
0.6 0.8 1 1.2 1.4
0
100
200
300
400
500
600
700
0 0.25 0.5 0.75 10
200
400
600
800
1000
1200
0 0.25 0.5 0.75 1
Missing mass (γ,K+K-) (GeV)
even
ts
Missing mass (γ,K+K-) (GeV)
even
ts
Missing mass (γ,K-p) (GeV)
even
ts
Missing mass (γ,K+p) (GeV)
even
ts
Missing mass distribution
KKp K+K-
K-p K+p
Reconstruction mode
Missing mass (γ, K+K-)X (GeV)
Missing mass (γ, Kp)X (GeV)
p p
K K
Backgrounds from hyperon resonances
Cut condition for KK modes
|M(γ,KK)-Mp|< 30 MeV
Cut condistion for Kp modes
|M(γ,Kp)-MK|< 30 MeV
Missing mass resolutionσ=10 MeV
cut cut cut cut
cut cut cut cut
0
20
40
60
80
100
1 1.025 1.05 1.075 1.10
200
400
600
800
1000
1200
1 1.025 1.05 1.075 1.1
0
20
40
60
80
100
120
140
160
180
1 1.025 1.05 1.075 1.10
25
50
75
100
125
150
175
200
1 1.025 1.05 1.075 1.1
Mass (K+K-) (GeV)
even
ts
Mass (K+K-) (GeV)ev
ents
Mass (K+K-) (GeV)
even
ts
Mass (K+K-) (GeV)
even
ts
KK invariant mass cut
KKp K+K-
K-p K+p
K+K- invariant mass (GeV)
K+K- invariant mass (GeV)
φ(1019)
Cut condistion for φselection
|MKK-1.019|< 10 MeV
cut cut cut cut
cut cut cut cut
1
10
10 2
Mass (K+K-) (GeV)
Mas
s (K
- p) (
GeV
)
1.4
1.5
1.6
1.7
1.8
1.9
2
1 1.1 1.2 1.3 1.4
Background subtraction
K+K- invariant mass (GeV)
K-p inva
rian
t mas
s (G
eV)
Nφ = (SA+SB) ‒α A ‒β B
MC
MCB
MC
MCA
BSAS
=
=
β
α
Sideband subtraction
BG outside of Λ(1520) cut
BG inside of Λ(1520) cut
Calculated fromKK invariant mass distribution In Monte Carlo simulation
AA
1.009 GeV1.039 GeV
SA
1.540 G
eV
1.500 G
eV
AA
BB
SA
SB
Λ(1520)
φ
Acceptance
0
0.1
0.2
0
0.1
0.2
-0.5 0
0
0.1
0.2
-0.5 0 -0.5 0
t+|t|min GeV2
Acc
epta
nce
• Monte Carlo simulation based on GEANT3• All materials and geometry information.• Detector efficiency and resolution• Realistic dσ/dt and decay angular distribution feedbacked from real data
2.373>Eγ >2.273 GeV 2.273>Eγ >2.173 GeV 2.173>Eγ >2.073 GeV
2.073>Eγ >1.973 GeV 1.973>Eγ >1.873 GeV 1.873>Eγ >1.773 GeV
1.773>Eγ >1.673 GeV 1.673>Eγ >1.573 GeV
Consistency between KK and Kp modes
KK modeKp mode
Good consistency between KK and Kp
modes
(1) Acceptance calculation,(2) Background subtraction
are working well.
0
10000
20000
0
10000
20000
0
10000
20000
-0.5 -0.25 0 -0.5 -0.25 0
t+|t|min(GeV2)
dσ/d
t (A
rbit
rary
Uni
t)
2.373>Eγ >2.273 2.273>Eγ >2.173 GeV 2.173>Eγ >2.073
2.073>Eγ >1.973 1.973>Eγ >1.873 1.873>Eγ >1.773 GeV
1.773>Eγ >1.673 GeV 1.673>Eγ >1.573 GeVYield (Arbitrary U
nit)
HZ and VT consistency
0
100
200
300
400
500
600
700
0 100 200 3000
100
200
300
400
500
600
700
0 100 200 300
φK+-Φ (degree)
even
ts
φK+-Φ (degree)
even
ts
0
100
200
300
400
500
600
700
0 100 200 3000
100
200
300
400
500
600
700
0 100 200 300
φK+-Φ (degree)
even
ts
φK+-Φ (degree)
even
ts
VT
VT
HZ
HZ
Eve
nts/30de
g.(w
/ acceptan
ce correction) Simultaneous fit to
distributions from VT and HZ data.
-0.2 < t+|t|min <0. GeV22.173<Eγ<2.373 GeV
1.973<Eγ<2.173 GeV
φ−Φ (degree)
Good consistency between HZ and VT data
Results
differential cross sections
Fitting function (dσ/dt) t+|t|min=0eb (t+|t|min))
Solid curve: Eγ independent slopeDashed curve: Eγ dependent slope
0
0.25
0.5
0.75
1
0
0.25
0.5
0.75
1
-0.4 -0.2 0 -0.4 -0.2 0 -0.4 -0.2 0 -0.4 -0.2 0
t+|t|min(GeV2)
dσ/d
t (µb
/GeV
2 )
2.273< Eγ<2.373 2.173< Eγ<2.273 2.073< Eγ<2.173 1.973< Eγ<2.073
1.873< Eγ<1.973 1.773< Eγ<1.873 1.673< Eγ<1.773 1.573< Eγ<1.673
Preliminary
Differential cross sections
0.03
0.04
0.05
0.06
0.07
0.080.09
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.80.9
1
-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0
t~ (GeV2)
dσ/d
t (µb
/GeV
2 )
0.03
0.04
0.05
0.06
0.070.080.090.1
0.2
0.3
0.4
0.5
0.6
0.70.80.9
1
-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0
t~ (GeV2)
dσ/d
t (µb
/GeV
2 )
0.03
0.04
0.05
0.06
0.07
0.080.09
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0
t~ (GeV2)
dσ/d
t (µb
/GeV
2 )
SAPHIRJ. Barth et al.EPJ A17(2003)269
CLASD. J. Tedeschi in Proceedings of the International Symposium“EMI2001”, Osaka, 2001
Preliminary
Differential cross section at t=-|t|min
0
1
2
dσ/d
t(t=
-|t| m
in)
(µb/
GeV
2 )
Eγ (GeV)
b (G
eV-2
)
0
5
2 3 4 5 6 7
Solid curve : Model (Pomeron + Pseudo scalar exchange) by A. Titov
• Peaking structure in dσ/dt at t+|t|min=0.
• Smaller t slope near threshold
Decay angular distributions at(1) 2.173<Eγ<2.373 GeV(2) 1.973<Eγ<2.173 GeV
Preliminary
Decay angular distribution
cosθK+
W(c
osθ)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Φ (degree)
2πW
(Φ)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 50 100 150 200 250 300 350
Φ (degree)
2πW
(Φ)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 50 100 150 200 250 300 350
φK++Φ (degree)
2πW
(φ+Φ
)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 50 100 150 200 250 300 350
φK++Φ (degree)
2πW
(φ+Φ
)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 50 100 150 200 250 300 350
φK+-Φ (degree)
2πW
(φ-Φ
)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 50 100 150 200 250 300 350
φK+-Φ (degree)
2πW
(φ-Φ
)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 50 100 150 200 250 300 350
φK+ (degree)
2πW
(φ)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 50 100 150 200 250 300 350
φK+ (degree)
2πW
(φ)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 50 100 150 200 250 300 350
cosθK+
W(c
osθ)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
2.173<Eγ<2.373 GeV
1.973<Eγ<2.173 GeV
cosθ φ φ−Φ φ+Φ Φ
WW
Curves are fit to the data.
•No energy dependence, except for φ distribution.
•Natural parity exchange is dominant.
-0.2 < t+|t|min <0. GeV2
Summary of LEPS measurement
• Differential cross section at t=-|t|min– Peaking structure around Eγ=2.0 GeV– Prediction from Regge theory:
• contribution from Pomeron increases with energy.– Meson and/or glueball exchange could be candidates to make
the bump.• Decay angular distribution
– Dominant contribution from helicity conserving amplitude.– Natural parity exchange (N) > Unnatural parity exchange (UN).– No energy dependence in polarization observables. Ratio
(N/UN) is energy independent.• The bump can not be explained by pseudo scalar
exchange only.• Possible presence of additional natural parity exchange.
Open questions
• What is origin of the peaking structure ?– Natural parity exchange– Signiture of 0+ glueball ?– A fit by simple model failed.
– Need for further theoretical studies.• Isospin symmetry ?
– Glueball should be “flavor blind”– LEPS Deuteron target data (2002-2003)– CLAS Deuteron data (g2, g10)
• Measurements at Eγ=2.4-3 GeV– near future plan at LEPS– Ongoing analysis for large |t| at CLAS (g1)
( )⎟⎟
⎠
⎞
⎜⎜
⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛ −+⎟⎟
⎠
⎞⎜⎜⎝
⎛ −⎟⎟⎠
⎞⎜⎜⎝
⎛==→
δ
γ
φφγσ
0
16.0
0
2
22)0(
susa
sus
pp
Ctppdtd
Summary
• New LEPS results for differential cross section of γp→ φp reaction and decay angular distribution near threshold.
• Non-monotonic rise of differential cross section at t=-|t|min with energy
• Dominant contribution from natural parity exchange, no energy dependence near the bump.
• A possible presence of additional natural parity exchange.
Acknowledgements
and many other persons.
This work was greatly supported by
Thank you very much
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