# Presentation: 102185

## Two Kaon Photoproduction and (1520) and (1540)

- Yongseok Oh and K. Nakayama
- (University of Georgia)
- T.-S.H. Lee
- (Argonne)

- New Theoretical Tools for Nucleon Resonance Analysis

- Aug. 29 – Sep. 2, 2005, Argonne National Laboratory

- Blue: positive experimental results
- Red: negative experimental results

## Outline

- Introduction
- Double kaon photoproduction
- Radiative decays of (1520)
- Pentaquarks: expt. and theory (soliton model)
- The                      reaction: model
- Results
- Radiative decay of (1520)
- Exotic (1540) production
- Summary

## 1.Introduction

-                         reaction at low energies
- Provides a tool to study various hadron productions
- In          channel
- vector meson (especially  meson) production
- In          channel
- hyperons (especially (1520)) production
- In          channel
- exotic pentaquarks, if any.    [putative (1540)]
- First experiment which claimed the observation of (1540)
- Difficulties
- Many resonances in each channel
- Lots of parameters are introduced
- Experimental data are not enough
- Most of the limited data show the mass distribution in an arbitrary unit
- Gauge invariance, Complicated rescattering processes

## Previous theoretical works
K. Nakayama, K. Tsushima, PLB 583 (2004)
A.R. Dzierba et al., PRD 69 (2004)
W. Roberts, PRC 70 (2004)
A.I. Titov et al., PRC 71 (2005)
In this work, (hep-ph/0412363) we consider
Kaon background diagrams
Vector meson production
Tensor meson production
Intermediate S=-1 hyperons and S=+1 (1540)
Form factors are included. Charge conservation is restored by extending the conventional method, i.e., by introducing contact diagrams.
Exp. data are used to constrain the cutoff parameters.

- Previous theoretical works
- K. Nakayama, K. Tsushima, PLB 583 (2004)
- A.R. Dzierba et al., PRD 69 (2004)
- W. Roberts, PRC 70 (2004)
- A.I. Titov et al., PRC 71 (2005)
- In this work, (hep-ph/0412363) we consider
- Kaon background diagrams
- Vector meson production
- Tensor meson production
- Intermediate S=-1 hyperons and S=+1 (1540)
- Form factors are included. Charge conservation is restored by extending the conventional method, i.e., by introducing contact diagrams.
- Exp. data are used to constrain the cutoff parameters.

## Radiative decay of (1520)

- Various model predictions for the radiative decay of (1520)
- Show strong model dependence
- Radiative decays into (1405) and * are suppressed
- Experimental measurements
- Very limited and uncertain
- Recent measurements
- SPHINX: measure ((1520)(1116)) from pNKPLB 604, 2004
- CLAS:  measure ((1520)(1116)) from pK  (PRC71, 2005)
- Larger values than most model predictions
- Motivation: What we can distinguish model predictions for (1520) decay in double kaon photoproduction.

## Status of (1405) decay (in keV)

| Model |  |  |  |  |
| --- | --- | --- | --- | --- |
| NRQM(Darewych et al. PRD 28) | 96 | 74 | 0.2 | ~0 |
| MIT bag(Kaxiras et al., PRD 32) | 46 | 17 | 0.1 | 3.6 |
| SU(3) broken NRQM(Kaxiras et al., PRD 32) | 156 | 55 | 0.7 | 0.07 |
| RCQM(Warns et al., PLB 258) | 215 | 293 |  |  |
| Chiral bag(Umino & Myhrer, NPA 554) | 32 | 51 |  |  |
| Algebraic model(Bijker et al., AP 284) | 85 | 180 |  |  |
| SPHINX (EPJA 21, 2004) | 159 +/- 33 |  |  |  |
| CLAS (PRC71, 2005) | 167 +/- 43 |  |  |  |
| PDG (PLB 592, 2004) |  | 304 +/- 53* | *: not measured directly |  |
| Bertini (NPB 279, 1987) | 33 +/- 11 | 47 +/- 17* |  |  |
| Mast et al. (PRL 21, 1968) | 134 +/- 23 |  |  |  |

## Exotic baryons

- Exotic hadrons
- Normal hadrons: minimal quark contents are          for baryons and         for mesons
- Exotic hadrons: not normal ones
- Pure exotic: can be distinguished by unique quantum numbers
- Cryptoexotic: whose quantum numbers can be generated by       or
- Pentaquark exotic baryons: made of four quarks and one antiquark
- (1540): observed first by LEPS at Spring-8anti-strangeness, mass ~ 1540 MeV, width ~ 1 MeV (Particle Data Group)
- (1862): exotic S=-2, I=3/2 baryon (NA49)
- c(3099): anti-charmed baryon (H1)

## Exotic baryons (II)

- Fact or Fiction?  Experiment review by K. Hicks (hep-ex/0504027)Do they really exist?
- Positive resultsLEPS, DIANA, CLAS, SAPHIR, ITEP, HERMES, ZEUS, COSY-TOF, SVD,NA49, H1, etc
- Negative resultsBES, BaBar, Belle, LEP, HERA-B, SPHINX, HyperCP, CDF, FOCUS, PHENIX, WA89, etc
- If exists, then
- Low mass, narrow width
- hidden structure in baryons?
- Quantum numbers: spin & parity?
- Splitting in the multiplets – Where are the other members?      Who are they?
- Production mechanisms – Why can they be seen only in some places?

## Exotic baryons (III)

-  Recent results from JLab (JLab News, April 28, 2005)
- (g11) Similar expt. as SAPHIR but 2 orders of magnitude better statistics
-                                   no evidence of the +
- (g10) the original expt. with higher statistics. (deuteron target)                                   coming soon
-  Recent SPring-8 experiment (on deuteron target)    confirms the  peak (T. Nakano: Pentaquark 2004, QCD 2005)
-  ++(?)  by STAR Collaboration (Huang: QCD 2005)

- Existence problem: experimental work

## History

- Earlier experiments for pentaquark 
-                              J. Tyson et al. PRL 19, 255 (1967)
-                              R.J. Abrams et al., PRL 19, 259 (1967), etc
-          E.W. Anderson et al., PL 29B, 136 (1969)

- Found peaks for ,
- but concluded no resonance.

-  Many crypto-exotic resonances were reported earlier, e.g.
-  Hirose et al. Nuovo Cim. 50A (1979)          Amirzadeh et al. Phys. Lett. 89B (1979)  Aref’ev et al. Yad. Fiz. 51 (1990)                 Karnaukhov et al. Phys. Lett. B 281 (1992)
-  most of them were found to have narrow widths, but their existence was not confirmed by later expt.
-  SPHINX: X(1810),  X(2050),  X(2400) ~                         Yad. Fiz. 65 (2002)

## Early Expt. (p reaction)

- Peaks at 1590 and 1950 MeV in p  K with 8 GeV beam : interpreted as kinematic reflection due to higher meson (spin-2 and 3) resonances since the peaks move to 1500 and 1800 MeV with 6 GeV beams.E.W. Anderson et al., Phys. Lett. 29B, 136 (1969)
-  A.R. Dzierba et al., PRD 69, 051901 (2004)
- Claims that the peak observed at 1540 MeV in N reaction may be kinematic reflection coming from tensor mesons.

- 8 GeV beam

- 6 GeV beam

## Models for pentaquarks

- Diakonov et al. (chiral soliton model, 1997)
- Equal spacing rule for antidecuplet (group theoretic relation)
- Identify N(1710) as antidecuplet and m=180 MeV (by fitting the parameters to the other baryons), which gives  at 1530 MeV
- But                      is not allowed
- Bound state model of soliton-meson (Callan and Klebanov, 1985)
- Treat the strangeness sector differently from the light (u,d) quark sector
- Repulsive interaction for KN (S=+1 channel)
- Recent works: Itzhaki et al. (2004)
- Park, Rho, Min (2004): consider the system of soliton, K, K*
- test the formation of (1540) vs a (KSRF parameter,                           )
- possible resonance at a~1 (a~2 in the real world)

## Models for pentaquarks

- Heavy pentaquarks
- Quark models: Lipkin (PLB 195, 1987), Gignoux et al. (PLB 193,1987)
- Pentaquarks with anti-charm and strange quark may be bound
- Fleck et al., Stancu etc: more sophisticated quark model
- Heavy pentaquarks in Skyrme model
- Riska-Scoccola (PLB 299, 1993)
- apply the Callan-Klebanov model to anti-charmed pentaquark
- Bottom-up approach (chiral Lagrangian + symmetry breaking)
- Bound states of soliton- where  means heavy pseudoscalar meson (like D, B)
- Bound nonstrange heavy pentaquarks (mass smaller than DN threshold)
- Does not show heavy quark symmetry in a transparent way

## Models for pentaquarks

- Heavy quark symmetry
- J = SQ + SL, SL = Sq + L  hadron with J = SL +/ 1⁄2should be degenerate in infinite heavy quark mass limit
- In mesons, pseudoscalar () and vector (*) mesons (M = 400  140  45 in MeV)
- In baryons, Q and Q*  (M = 190  65  ? in MeV)
- Soliton-meson bound state model for heavy (exotic) baryonsOh, Park, Min (PLB 331, 1994; PRD 50, 1994)
- Start from the infinite mass limit   (top-down approach)
- Treat the heavy pseudoscalar and heavy vector mesons on equal footing

- SQ: heavy quark spin
- Sq: light quark spin
- L: orbital ang. mom.

- Heavy-qaurk symmetric& chirally invariant

## Models for pentaquarks

- Lowest heavy pentaquark (Qqqqq) states in the infinite heavy quark mass limit

- Oh, Park, Min (PLB 331, 1994; PRD 50, 1994)

- Shows heavy quark symmetry

- Lesson: do not integrate out heavy vector meson degrees of freedom in the heavy quark sector in favor of heavy pseudoscalar mesons

## Models for pentaquarks

- Two expansion parameters
- 1/Nc: soliton
- 1/mQ: heavy quark mass
- 1/Nc only.  Msol = O(Nc),   mQ = O(Nc0)
- We may estimate 1/m corrections in the soliton-fixed frame. (Oh, Park, PRD 51, 1995)

- Heavy quark partners

- Substantial 1/m corrections

- Before quantization

## Models for pentaquarks

- In nature, mQ >> Msol
- Spectrum for the heavy-meson—soliton system in the heavy-meson fixed frame(Oh, Park, ZPA 359, 1997)

- c(1/2+)

- c(1/2) and c(3/2)

- Only one bound state for (nonstrange) heavy pentaquark states
-  pentaquark states depend on the details of the model

- c(1/2+)

## Model for double kaon photoproduction: Diagrams (I)

- V = 
- T = a2(1320), f2(1275)

- (1) Kaon background diagrams

- (2) Vector meson & tensor meson productions

- M: mesons

## Vector meson production

- , , and  mesons
- Considered diagrams include
- Pomeron exchange
- Pseudoscalar meson exchange
- f2 meson exchange
- Nucleon diagrams
- All parameters are fixed by the experimental data for vector meson photoproduction.

-  meson photoproduction

## Tensor meson production

- Tensor meson photoproductions
- a2+ and a2**** productions: pion exchange is the dominant process.- consistent with the data.
- a20 and f2 productions: pion exchange is not allowed by C-parityC(a2) = C(0) = +1, C(0) = ****1vector meson exchange is expected to be the dominant mechanism at low energies.Odderon exchange at high energies(?)- expt. data: very limited and very uncertain (cf. Dzierba et al. used one-pion-exchange for neutral tensor meson photoproductions.)

- pa2+(1320)n

## Diagrams (II)

- (3) Intermediate S=-1 hyperons
-   baryons   (1116), (1405), (1520)
-   baryons   (1193), (1385)
-  photo-transitions such as   N and YY’ (such as , *, *, etc)
-  couplings
-  exp. information is used if available.
-  otherwise, quark model and SU(3) relations are used

## Diagrams (III)

- (4) Intermediate mass: 1540 MeV,   width: 1 MeV

- (5) Form factorscharge conservation (            )  is restored by adding contact terms.In effect, e.g.,

- Isospin = 0 (antidecuplet) can be formed in                        and

## (1540) production

-                   studied by various groups
- SU(3) symmetric interactions of pentaquarks (Oh, Kim, PRD 70, 2004)
- Total and differential cross sections (Oh, Kim, Lee, PRD 69; NPA 745, 2004)

## 3. Results 

- Total cross sections of 4 processes in  N  K K N, where the isospin of the nucleon is not changed.

- Form factors
- Fit the cutoff parameter of the form factors;  = 0.9 GeV
- Expt. data are for pK+K-p
- Erbe et al., Phys. Rev. 188 (1969)Ballam et al., Phys. Rev. D5 (1972)

- red solid:
- blue dot-dashed:
- red dashed:
- blue dotted:

## Results for N  KKN

-                        main contribution comes from (1520) production.Study the properties of (1520), e.g. radiative decay of (1520)  into  and 

## (1520)

| Model |  |  |  |  |
| --- | --- | --- | --- | --- |
| SU(3) broken NRQM(Kaxiras et al., PRD 32) | 156 | 55 | 0.7 | 0.07 |
| RCQM(Warns et al., PLB 258) | 215 | 293 |  |  |

- Red line: 

- Red line: 

## (1520)

## Other hyperons (PDG)

-  resonances            in MeV
- (1600) 1/2+ ***   50-250
- (1670) 1/2- ****   25-50
- (1690) 3/2- ****   50-70
- (1800) 1/2- ***    200-400
-  resonances
- (1560) Bumps **
- (1580) 3/2- **
- (1620) 1/2- **
- (1660) 1/2+ ***     40-200

- LAMP2 Collab. Z. Phys. C 7, 17 (1980)

- (1620) ?

## Results for N  KKN

-                                               : reactions where  can be formed
-                  : reaction with CLAS data (cf. data are not normalized. compare the shape only)

- positive parity 

- negative parity 

- without  and 

- E = 2.3 GeV

## Results for N  KKN

- Vector & tensor meson contributions

- vector & tensor mesons only

- tensor mesons only

- KK invariant mass distributionat E = 2.3 GeV

- KN invariant mass distribution

## Differential cross sections for n  K+K-n

- Differential cross section at E=2.3 GeV and MKN=1.54 GeV as a function of the angle of K- in the CM frame

- with positive parity (1540)

- without (1540)

- with negative parity (1540)

## Spin asymmetries for n  K+K-n

- Single photon beam asymmetry x and beam-target double asymmetry CBT
- blue lines: without (1540)black lines: with positive parity (1540)red lines: with negative parity (1540)

- At E = 2.3 GeV and MKN = 1.54 GeV

- At E = 2.3 GeV for a given angle

## 4. Summary  

- We studied N  KKN reactions in a model including kaon backgrounds, vector and tensor meson productions, intermediate hyperon states for studying the production and the parity of (1540).
- Form factor parameters are fitted to the total cross section data for p K+K****p.
- Dominant contributions come from (1520) and (1020).
- Tensor meson part is small in the considered kinematic region.
- It is difficult to make a conclusion about the peak observed in experiments.
- Spin asymmetries would be useful to study the formation (and the parity) of (1540): however, model-dependence is unavoidable.
- More precise and accurate experimental data are required. (JLab, Spring-8, etc)