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

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30

40

50

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90

0.6 0.8 1 1.2 1.40

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1000

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0 0.25 0.5 0.75 10

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1200

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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

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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

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-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

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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

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0.75

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-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

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0.080.09

0.1

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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

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0.3

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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