# Presentation: 868934

##  K. Kadija 
for the NA49 Collaboration

**for the NA49 Collaboration**
** **
** **

- Observation of pentaquark states at NA49 

## Outline

- 1

-   Pentaquark models
-   NA49 experiment
-   Analysis
-    and  invariant mass spectra
-   Preliminary (1530)0  spectra
-   Conclusion

## Models: Chiral Soliton

**D. Diakonov, V. Petrov, M. Polyakov, Z.Phys. A 359 (1997) 305**

********(1530)

- (1890)

- (2070)

- Suggested anti-decuplet of baryons: *J****P******=1/2******+***

**(ududs)**

**(dsdsu)**

**(ususd)**

********

********

- 

****

- ≤ 15 MeV)

-     42 MeV)

- N(1710)

- Input

******m **** **** ****~ 180 MeV**

- ~

**~**

- ~

****

**!**

## Models: Correlated quarks

**R. Jaffe and F. Wilczek, arXiv:hep-ph/0307341**

**************(ud)****2****S**** ******

******ud)(su)d>**

******************us)****2****d>**

- Suggested 10**f       **8**f** of baryons: *J****P******=1/2******+***

**************ds)****2****u>******

****

******Input**
**(the Roper)**

****

**N **** ****|(ud)****2****d>**

******Input**

- 

- 

**M*************MeV /c******2***

**M*************MeV /c******2***

**M*************MeV /c******2***

**M*************MeV /c******2***

******S********ud)(su)s>**

******S********(su)****2****s>**

**M*************MeV /c******2***

**M*************MeV /c******2***

- S

- S

- 

- ~

- ~

**3**

**3**

**3**

**3**

- O

- O

**8****f**** + 10****f**

**3**

**1****-****   1/2****-**** = 1/2****+ ****, 3/2****+**

- O

**Note that the ************and ************have the same mass**

****************
****************

****************
********************

## Models

- PARITY

- +

- -

- Chiral soliton model

- Uncorrelated quarks

- SPECTRUM

- Chiral soliton model:
- Heavy exotic cascades

- Quarks:
- Light exotic cascades

- 10

- 10 + 8

- Lattice QCD

**??**

**More pentaquarks and their properties needed to determine correct  model**

- Correlated quarks

****

********

****

****

****

****************

******s**

**N****s**

**N**

**N**

**Mass (arbitrary units)**

**quarks**

**soliton**

## NA49 Experiment

- dp/p2 =  7 x (0.3) 10-4  (GeV/c)-1

- VTPC-1 (VTPC-2+MTPC)

- 3-6 %   dE/dx resolution

- Trig= 28.1 mb

**Only charged tracks detected**

## Data Sample

-         Before vertex cut     After Vertex  Cut
- 1999          1.2 M                   0.66 M
- 2000          2.7 M                   1.5   M
- 2002          2.9 M                   1.6   M
- Total          6.8 M                   3.76 M
-          Main vertex cuts:
-           1.)   fit converged
-           2.)    x2+y2< 1 cm2
-           3.)   -590.5 cm <  z < -572.5 cm

- p+p at        =17.2 GeV

**i.e. within target**

## V0 and  Invariant Mass Spectra

- 1640 events

- |M1.32131| < 0.015 GeV

- 551 events

- V0 and  Invariant Mass Spectra

**************peak**

**	**

**************peak**

******peak**

******peak**

##  

- position at main vertex (bx , by):
-             |bx|  <  1.0 cm
-             |by|  <  0.5 cm
- # of point cut  > 10

-  

- Primary pion selection

- 

##  -  Invariant Mass Distribution

-  -  Invariant Mass Distribution

********

**Structure at 1.86**

**Very small systematic error**

##  +  Invariant Mass Distribution

-  +  Invariant Mass Distribution

**No clear structures at 1.86 GeV/c****2**

********

##  Primary cuts : opening angle

-  lab. angle between and

- 

- Background

- Signal

-  Primary cuts : opening angle

********

********

****

##  Primary  cuts: dE/dx and momentum

- Negative tracks

- Positive tracks

-  events

-  events

- e-

- 

- K

- P

-  Primary  cuts: dE/dx and momentum

**large proton and K****+ ****contamination**

**Purify with momentum and asymmetric dE/dx cut **

##                     -                                   +

- cos() < 0.997  (4.5)

-                     -                                   +
- -         -1.5  < dbb < 1.5             -1.5  < dbb < 1.5 
- +      -0.5 < dbb < 1. 5            -1.5  < dbb < 1.5 
-              p >  3 GeV/c                       p >  3 GeV/c

-  Summary of additional primary  cuts

- 

- 

- 

- 

## FinalInvariant Mass Distributions

**C. Alt et al., hep-ex/0310014**

**Accepted by PRL**

************

**********or  ******** 1/2******

**0**

**0**

**********or  ******** 1/2******

**0**

**0**

********************

##  Summed spectra

-  Summed spectra

## 5  search

****

- 5  search

**Distance to Bethe- Bloch  curve: ****|d****bb****| < 3 ******
**|M(p********-****)  - 1.115683| < 0.015 MeV**
** ****Z ********- Z****main_vtx****  > 12 cm**
** ******** ****-****  position at main vertex (b****x ****, b****y****):**
**            ****|b****x****|  <  2 cm**
**            ****|b****y****| **** ****<  1 cm**
********** ****(from ******** ****-**** decay) position at main vertex **
**            ****|b****y****|****  ****> 0.5 cm**** **

- selection:

**could also be the **************

##  Mass and width determination

- M = 1.862 ± 0.002 GeV/c2

- M = 1.864± 0.005 GeV/c2

- M = 1.862 ± 0.002 GeV/c2

- ≤ 18  MeV/c2

-  Mass and width determination

## Search for  and via decay

- Search for  and via decay

## 

- What do we expect  in (1530)0 ?

********

********

****

****

********************

****************

****************

****************

********

**R. Jaffe and F. Wilczek, hep/ph/0312369**

## (1530)0 - :  PRELIMINARY

- (1530)0 - :  PRELIMINARY

**Entries / 7.5 MeV/c****2**** **

******0**

**M=1.855 ****± 0.003 GeV/c****2**

************

** ****octet member**

**R. Jaffe and F. Wilczek**

## (1530)0  PRELIMINARY

- (1530)0  PRELIMINARY

****************

****************

****************

****************

*No cuts*

- p*GeV/c*

**- 0.5 ********< d****bb**** < 1.5 ******

- 

- +

- No evidence for to decay

- No evidence for to decay

## Conclusion I

-        at  M = 1.862 ± 0.002 GeV/c2  ( ≤ 18 MeV/c2) is observed
-   At  the same mass a peak is observed in the   spectrum
-   The corresponding antibaryon spectra show  enhancement at
-       the same mass

- Conclusion I

********

****

********************

**0**

**0**

##  Conclusion II 

-   There is no indication  for a resonance

-  Conclusion II

********

****

********************

**0**

**0**

****************

**-**

## Preliminary Conclusion 

- 

- ?

**correlated quark**

**Soliton/Skyrme**

-  Existence of the  octet member supports the diquark model,           and seems to contradict the standard soliton model
-  There is a possibility to add an octet to the anti-decouplet in the soliton model, but there seems to be no reason to expect, as is observed, similar masses for the and states
- In the diquark model, the  and naturally lie at the same mass

## Outlook 

**NA49**

-  Spin is unknown
-  Parity is unknown
-  Width ?
-  Production mechanism?

- Outlook

- Further improvement of experimental resolution
- Data sample increase by up to ~ 30%
- Search for s0(-) S)

-  (3-6) • 107  p+p events  (new DAQ system)
-  Neutral  pions

**Open Questions**

**NA49’ Project**

**(Expression of Interest CERN-SPSC-2003-038)**

**In particular :**

## The NA49 Collaboration

- 1