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++ photoproduction with vector K* photoproduction with vector K*(including other recent results)

Seung-il Nam*1,2 Atsushi Hosaka1 Hyun-Chul Kim2

1.Research Center for Nuclear Physics (RCNP), Osaka Univ., Japan2.Nuclear physics & Radiation technology Institute (NuRI), Pusan Univ., Korea 　

RCNP & NuRI

Recent status of Theta

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Recent experiments for pentaquark baryonsRecent experiments for pentaquark baryons

New evidence for New evidence for ++ by LEPS at Spring-8 by LEPS at Spring-8

(1520) (=(1520) (=*) photoproduction revisited experimentally by LEPS*) photoproduction revisited experimentally by LEPS

++ ++ announced by STAR announced by STAR

No clear evidence for No clear evidence for ++ CLAS at JLAB CLAS at JLAB

Negative results from BABAR etcNegative results from BABAR etc

Controversial experimental situationsControversial experimental situations

Considering photoproduction of Considering photoproduction of ++, (LEPS and CLAS), (LEPS and CLAS)

Positive results out of neutron target vs. Negative results out of proton targetPositive results out of neutron target vs. Negative results out of proton target

Suppression of total cross section for proton? Suppression of total cross section for proton?

What is the suppression mechanism?What is the suppression mechanism?

Huang, talk given at Beijing (2005)Huang, talk given at Beijing (2005)

R.De Vita, talk given at APS (2005)R.De Vita, talk given at APS (2005)

talk given at Nara (2005)talk given at Nara (2005)T.Nakano, talk given at Beijing (2005)T.Nakano, talk given at Beijing (2005)

S.Ricciardi [BABAR], hep-ex/0507027S.Ricciardi [BABAR], hep-ex/0507027

Recent status of Theta

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Theoretical interests in this talkTheoretical interests in this talk

* photoproduction concerning * photoproduction concerning ++: new analysis: new analysis

Possible interpretation for CLAS result: Isospin asymmetry Possible interpretation for CLAS result: Isospin asymmetry

++ photoproduction with photoproduction with K*K*: reaction process analysis: reaction process analysis

Theoretical frameworkTheoretical framework

Effective Lagrangian approachEffective Lagrangian approach

The Born approximation at tree levelThe Born approximation at tree level

Phenomenological form factor maintaining the Ward-Takahashi identityPhenomenological form factor maintaining the Ward-Takahashi identity

Parameters estimated by phenomenological consideration and model calculationParameters estimated by phenomenological consideration and model calculation

Experimental data used for fixing cutoff Experimental data used for fixing cutoff

S.I.N et al.,Phys.Rev.D71,114012S.I.N et al.,Phys.Rev.D71,114012

S.I.N et al.,hep-ph/0505134, S.I.N et al.,hep-ph/0505134, submitted to Phys.Lett.Bsubmitted to Phys.Lett.B

S.I.N et al.,in preparationS.I.N et al.,in preparation

Photoproduction of Lambda*

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Strong correlation between Strong correlation between and and (1520)(1520)

New evidence of New evidence of + + by LEPS at Spring-8 using deuteron target by LEPS at Spring-8 using deuteron target

Simultaneous productions of Simultaneous productions of ++ and and * *

KK--

DD

++

pp

**

DD

++

<< 1<< 1

(1520) invariant mass K-p missing mass for

Photoproduction of Lambda*

++ photoproduction from deuteron target by LEPS photoproduction from deuteron target by LEPS

Only for Only for * resonant region, peak for * resonant region, peak for appears appears

Motivation: Is it possible for extracting information for Motivation: Is it possible for extracting information for via via *?*?

** KK--

DD++

pp

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Photoproduction of Lambda(1520)

Photoproduction of Photoproduction of (1520)(1520)

InteractionsInteractions

ParametersParameters

ggKNKN* * == 11 (Experiment)11 (Experiment)

ggK*NK*N* * =0,=0, 11 (Quark model)11 (Quark model)

Rarita-Schwinger vector-spinor fieldRarita-Schwinger vector-spinor field W.Rarita et al.,Phys.Rev.60,61W.Rarita et al.,Phys.Rev.60,61

No PS coupling scheme due toNo PS coupling scheme due to

= 0 and = 0 and = 0= 0

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Photoproduction of Lambda*

p p ++**: Proton target: Proton target

Qulitaively well reproduced experimental data; Cutoff Qulitaively well reproduced experimental data; Cutoff =750 MeV=750 MeV

Dominant contact term (Kroll-Ruderman) Dominant contact term (Kroll-Ruderman)

D.P.Barber [Daresbury],Z.Phys.C7,17D.P.Barber [Daresbury],Z.Phys.C7,17

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Photoproduction of Lambda*

n n 00**: Neutron target (No data for cross section): Neutron target (No data for cross section)

~30 times smaller ~30 times smaller nn than than pp

due to absence of the contact term due to absence of the contact term

Large asymmetry actually shown in the recent LEPS experimentLarge asymmetry actually shown in the recent LEPS experiment

No No K*K*

T.Nakano, talk given at Beijing (2005)T.Nakano, talk given at Beijing (2005)talk given at Nara (2005)talk given at Nara (2005)

No No K*K*

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3/23/2

3/23/2

3/23/21/21/2

1/21/2

1/21/2

ContactContact K(spin-0)-exchangeK(spin-0)-exchange K*(spin-1)-exchangeK*(spin-1)-exchange

Photoproduction of Lambda(1520)RCNP & NuRI

K*K*-dominance scenario proposed by experiments-dominance scenario proposed by experiments

In the experimental analysis, almost In the experimental analysis, almost (1520) decayed from its |S(1520) decayed from its |Szz|=3/2 state|=3/2 state

From this fact, From this fact, K*K*-exchange was believed as dominant contribution (-exchange was believed as dominant contribution (tt-channel)-channel)

Theoretical proof: Is this conclusion is correct?Theoretical proof: Is this conclusion is correct?

Natural consequences for Natural consequences for K K and and K*K*

Large |SLarge |Szz|=3/2|=3/2 contribution from the contact term not from contribution from the contact term not from K*K*

D.P.Barber [Daresbury],Z.Phys.C7,17D.P.Barber [Daresbury],Z.Phys.C7,17

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CLAS high statistics experiment

nKnK++ invariant M invariant M pKpK00 invariant M invariant M

ProtonProtonProtonProton

(1520)(1520)

g11 experiment CLAS @JLABg11 experiment CLAS @JLAB

Proton targetProton target

No obvious peak for No obvious peak for

Estimation: Estimation: pp//pp

< 0.2%< 0.2%

Corresponding to Corresponding to pp< 2 nb< 2 nb

The cross section from the proton suppressed?The cross section from the proton suppressed?

Positive evidence from the neutron target (LEPS)Positive evidence from the neutron target (LEPS)

Asymmetry between neutron and proton targets?Asymmetry between neutron and proton targets?

Hinted by Hinted by (1520) photoproduction (1520) photoproduction

If If (1520) and (1520) and ++ behave similarly in reaction processes: Spin-3/2 behave similarly in reaction processes: Spin-3/2 ++

R.De Vita, talk given at APS (2005)R.De Vita, talk given at APS (2005)

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RCNP & NuRI

CLAS high statistics experiment

Possible explanation for the null results of the CLAS Possible explanation for the null results of the CLAS

Taking a look at Feynman diagrams…Taking a look at Feynman diagrams…

00

nn (1520)(1520)e=0e=0

barbar00

pp ++(1540)(1540)

e=0e=0

++

pp (1520)(1520)e=1e=1

--

nn ++(1540)(1540)e=1e=1

n-p asymmetry for spin-3/2 n-p asymmetry for spin-3/2 photoproduction photoproduction

Suppression to the proton target!Suppression to the proton target!

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Photoproduction of Theta(3/2)

Photoproduction of Photoproduction of ++(3/2):(3/2): KbarKbar++(3/2) (3/2)

Analogous calculations to Analogous calculations to * photoproduction: Cutoff * photoproduction: Cutoff =750 MeV=750 MeV

Clear n-p asymmetries for two paritiesClear n-p asymmetries for two parities

= 1 MeV, = 1 MeV, gg=+1=+1K*NK*N==33ggKNKN and and gg=-1=-1

K*NK*N=1/=1/33ggKNKN (Quark model) (Quark model)

pp-wave (-wave (=+1) and =+1) and dd-wave (-wave (=-1) couplings=-1) couplings

=+1 =-1

NeutronNeutron

ProtonProton

NeutronNeutron

ProtonProton

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Photoproduction of Theta(3/2)

Photoproduction of Photoproduction of ++(3/2): (3/2): KbarKbar++(3/2) (3/2)

Clear n-p asymmetryClear n-p asymmetry

Our estimation with Our estimation with =1 MeV=1 MeV

pp < 2 nb and < 2 nb and nn

< 30 nb when 3/2< 30 nb when 3/2++

pp < 10 nb and < 10 nb and nn

< 240 nb when 3/2< 240 nb when 3/2--

pp< 5 nb and < 5 nb and nn

< 5 nb when 1/2< 5 nb when 1/2++

Possible explanation for the recent CLAS experimentPossible explanation for the recent CLAS experiment

Experimental data for neutron target is necessaryExperimental data for neutron target is necessary

VeryVery22 preliminary CLAS internal report: preliminary CLAS internal report: nn < 20 nb < 20 nb

Strong suppression for Strong suppression for the proton target the proton target }}

N.Baltzell, talk given at CLAS user meetingN.Baltzell, talk given at CLAS user meeting

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Photoproduction of Theta(3/2)RCNP & NuRI

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Photoproduction of Photoproduction of ++(3/2):(3/2): K*barK*bar++(3/2) (3/2)

Reaction Reaction N N + + including including N N **barbar++subprocess (planned at CLAS)subprocess (planned at CLAS)

Three vector meson coupling Three vector meson coupling *** * necessary for gauge invariancenecessary for gauge invariance

Including Including (800,0(800,0++) ) withwith ggNN = = ggKNKN and and ggK* K* = = ggKK*KK*

= 1 MeV, = 1 MeV, gg=+1=+1K*NK*N==33ggKNKN and and gg=-1=-1

K*NK*N=1/=1/33ggKNKN (QM) (QM)

Photoproduction of Theta(3/2)RCNP & NuRI

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Photoproduction of Photoproduction of K*barK*bar++(3/2): Positive parity (3/2): Positive parity

No obvious n-p asymmetryNo obvious n-p asymmetry

KK-exchange ~ contact term-exchange ~ contact term

Strong forward scatteringStrong forward scattering

Pho

ton

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asy

mm

etry

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asy

mm

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dd /d

t [nb

/GeV

/dt [

nb/G

eV22 ]]

Photoproduction of Theta(3/2)RCNP & NuRI

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Photoproduction of Photoproduction of K*barK*bar++(3/2): Negative parity (3/2): Negative parity

No obvious n-p asymmetryNo obvious n-p asymmetry

Strong forward scatteringStrong forward scattering

Rather different PBA from Rather different PBA from =+1=+1

Determination of the parity?Determination of the parity?dd

/dt [

nb/G

eV/d

t [nb

/GeV

22 ]]

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Photoproduction of Theta(1/2)RCNP & NuRI

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Photoproduction of Photoproduction of K*barK*bar++(1/2): Positive parity (1/2): Positive parity

No obvious n-p asymmetryNo obvious n-p asymmetry

Strong forward scatteringStrong forward scattering

Rather different PBA’sRather different PBA’s

Pho

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mm

etry

Pho

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mm

etry

Pho

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Pho

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etry 3/23/2++

Pho

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Pho

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etry 3/23/2--

Photoproduction of Theta(3/2)RCNP & NuRI

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Two polarizations: photon and Two polarizations: photon and K*K*

Looking at amplitudes….Looking at amplitudes….

When photon perpendicular to When photon perpendicular to scattering plane: scattering plane: K*K*-contribution -contribution disappearsdisappears

xxzz

yy

K*K*((kk22))

KK

y-z planey-z plane

////KK

NN·p·pK*K*

Photoproduction of Theta(3/2)RCNP & NuRI

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Polarizatios in Polarizatios in K*barK*bar++

//K*: : -exchange survives-exchange survives

K*: : KK-exchange survives-exchange survives

Parallel: //K* Perpendicular: K*

Due to the amplitude structuresDue to the amplitude structures}}

Summary and conclusionRCNP & NuRI

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(1520) photoproduction (1520) photoproduction

Strong correlation between Strong correlation between ++ and and * shown by recent LEPS exp.* shown by recent LEPS exp.

Qualitatively well reproduced data for proton targetQualitatively well reproduced data for proton target

Predictions for neutron target: much smaller cross sectionsPredictions for neutron target: much smaller cross sections

Dominant contact term contribution: n-p asymmetry or Isospin asymmetryDominant contact term contribution: n-p asymmetry or Isospin asymmetry

Experiments showed the asymmetry actuallyExperiments showed the asymmetry actually

Recent CLAS exp.Recent CLAS exp.

No obvious peak for No obvious peak for ++: basically proton-photon scattering: basically proton-photon scattering

New LEPS evidence from neutron target: What happened? New LEPS evidence from neutron target: What happened?

Strong suppression expected for proton targetStrong suppression expected for proton target

What is the suppression mechanism?What is the suppression mechanism?

Suggestion: if Suggestion: if + + spin-3/2, the suppression occurs? spin-3/2, the suppression occurs?

Summary and conclusionRCNP & NuRI

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++(3/2) photoproduction (3/2) photoproduction

Analougous calculations to those of Analougous calculations to those of (1520)(1520)

Obvious n-p asymmetry shown: Suppression to the proton targetObvious n-p asymmetry shown: Suppression to the proton target

pp < 2 nb and < 2 nb and nn

< 30 nb when 3/2< 30 nb when 3/2++ ; ; pp < 10 nb and < 10 nb and nn

< 240 nb when 3/2< 240 nb when 3/2--

Less dependent on Less dependent on K*K*-contribution than spin-1/2 -contribution than spin-1/2 ++

++(3/2) photoproduction with vector (3/2) photoproduction with vector K*barK*bar

scalar kaon scalar kaon (800)-exchange possible (800)-exchange possible

Two polarizations possible: incident photon and outgoing Two polarizations possible: incident photon and outgoing K*K*

Selection rule for interchanging kaon after fixing photon polarization Selection rule for interchanging kaon after fixing photon polarization

//K*: : -exchange survives ; -exchange survives ; K*: : KK-exchange survives-exchange survives

Also valid for spin-1/2 baryon photoproductionAlso valid for spin-1/2 baryon photoproduction

RCNP & NuRIW

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Thank you very muchThank you very much