Observations%20of%20PentaQuarks:

1
Observations of PentaQuarks A Mini-Review
By A. Dolgolenko and M. Kubantsev
2
Content

• Introduction
• Observations of the T(1540) state year of 2003
  
• 
  
• 2004 results (up to mid-May)
• Other possible exotic baryons.
• Further studies, summary and outlook

First evidence from photo production (Spring-8)
Low energy
kaon beam (ITEP)

Photo/electro-production (JLAB, ELSA, HERMES)
over 200 citations!
Neutrino beam (ITEP-CERN-FNAL)
High energy electro-production (ZEUS) Low energy
proton beam (COSY) High energy hadron beams
(Serpukhov, Dubna, Fermilab,CERN, RICK) e e-
-collisions at BES and LEP
3
Introduction
All well established baryon states can be
understood as combinations of three valence
quarks u, d, s.These combinations are grouped in
SU(3) singlets, octets and decuplets
4
Why is the Baryon State called Exotic?
Any baryons that can not be made with this
triplet are to be considered as exotic. The
simplest configuration might consist of four
quarks plus anti-quark QQQQQ.
This state is called a
pentaquark. Truly exotic
states has Q with other flavor then other four
quarks
uudds (S 1, Q 1)
ssuud (S -2, Q 1)
ssddu (S -2, Q -2)

Other states can mix with standard baryons.
(No heavy flavors considered in this talk (see H1
talk)

5
Indeed, history of S 1 system search was not
encouraging
6
Prediction of narrow and exotic light baryons
In 1997 D. Diakonov, V. Petrov and M. Polyakov
proposed, on basis of a chiral soliton model, a
low-mass anti-decuplet of pentaquarks (qqqqq).
Predicted lower mass,
s1 state has mass of 1530 MeV/c2 and narrow
width lt15 MeV/c2. Three
baryons in the triangle corners are exotic.
They have been bold
enough to persuade experimentalists to look
for these states, so in the beginning of 2003
Z(1530), later T(1530)
nK or pK0 uudds
S 1
N(1710)
0
-3/2
I
-1/2
1/2
3/2
-1
1
S(1890)
-1
?(2070)
-2
uussd ?0 p or SK0
ddssu ?- p- or S-K-
7
LEPS at SPRING-8 FIRST OBSERVATION
?
K-
K
T
n
n
S 1 baryon resonance in K- missing mass
spectrum of ?n KK-n reaction on carbon was
found Mass of 1540 10 Mev/c2. Peak
significance is 4.6 s Peak width is lt 25 MeV/c2
8
DIANA BC at ITEP(MOSCOW)
The peak near
1540 MeV/c2 of
total 73 events has estimated background of 44
events, resulting in statistical significance of
4.4 s Gaussian fit of
the peak yields
M 1539 2 MeV/c2 G lt9MeV/
c2 (compatible with instrumental resolution)
9
CLAS with D target at JLAB
10
SAPHIR at ELSA

• T signal(fit)
• NT 6313 events
• M 1540 4 2 MeV/c2
• G lt 25 MeV/c2 Significance 5.2 s
• s(T) s(?0(1520)) 115
• No signal in T Kp
• suggests isoscalar state

11
Observation of T in neutrino interactionsITEP-F
NAL-CERN
Neon plus Deuterium
A.E.Asratyan et al.,hep-ex/0309042 Phys.
Atom.Nucl. 67,682(2004)
Re-analysis of data from FNAL (E180,E632) and
CERN(WA21, WA25,WA59) bubble chambers with H, D,
Ne fills. Signal is seen only on D and Ne.
Mass1533 5 MeV/c2 Width lt20MeV/c2
26 events with 15 events of the
background significance of 6.7 s.
12
CLAS with p-target at JLAB
V. Kubarovsky et al., hep-ex/0311046 Phys.
Rev.Lett.92,032001(2004)
NT 4110 events M 1555
10 MeV/c2 G 26 7 MeV/c2
Significance 7.8 1 s
No signal in pK system, so T is possibly
isoscalar
13
DubnaC-C interactions at 4.2 GeV/nucleon
R. Togoo et al., Proc. Mongolian Acad.Sci.,4(2003)
,2
Propane 2-meter bubble chamber in heavy ion beam
(C) of Dubna accellerator. The signal is
impressive 9 s effect(!?)
14
HERMES(eD) at DESY

• Airapetian et al., hep-ex/0312044,
• Phys.Lett.B585,213(2004)

e(27.6 GeV)D K0(pp-)pX
NT 56 events M 1528 2.6 2.1 MeV/c2
G 19 5 2 MeV/c2 Significance 4 6 s
15
SVD(pA) at Serpukhov
A.Aleev et al., hep-ex/0401024
NT 50 events M 1526 3.1 MeV/c2 G lt24
MeV/c2 Significance 4 6 s Production cross
section for XF gt 0 (30-120) mkb
16
COSY -TOF
M 1530 5 MeV
17
Evidence from e-p collider experiment ZEUS
S. Chekanov for ZEUS hep-ex/0405013(latest
update)
ep _at_ 300-318 GeV C.M.S. energy with integrated
luminosity 121 pb-1 NT 221 48 events
M 1522 3.1 MeV/c2 G 8 4 MeV/c2
Significance 4.6 s No T observed isoscalar(?)
18
Preliminary results from STAR(p-p collisions)
pp _at_ 200 GeV C.M.S. energy with 8 million events
Possible bump _at_ 1520 Mev/c2
S.Salur for STAR at RHIC hep-ex/0403009
19
Summary of observations
Average 153134
20
Summary of observations (supplemental)
21
The unclaimed Q(1540) ?
CERN Kp ? pK0X Bubble Chamber Data

• Berthon, et al.,
• Nucl. Phys. B63, 54 (1973)

Presented by V.D.Burkert at Penta-Quark 2003.
22
Estimation of T width (summary)

Direct high resolution width measurements are
under way now.
23
Estimation of T width (summary,cont.) Kaon
experiments

• Direct observation(DIANA)
  lt 9 MeV
• R. Cahn and G.Trilling (DIANA re-analysis)
  0.9 MeV
• S. Nussinov (Kn and Kd)
  lt6 MeV
• R. Arndt et al (Kn and Kd)
  lt1.5 MeV
• I.Strakovsky et al PWA for Kn(I0) with P01
  (Jp3/2) lt1-2 Mev
• Other partial waves S01(Jp1/2-) and P03(Jp
  3/2 ) are not conclusive
• W.R. Gibbs (Kd cross section re-analysis)
  0.90.2 Mev
• (nucl-th/0405024, May 9 2004)
• Data from T. Bowen et al. Phys.Rev.
  D2,2599(1970), A.S. Carrol et al. Phys. Lett.45B,
  531(1973)
• Masses 1520 -1550 are peferable for S01 and P01

24
NA49(pp)at CERN SPS
Experiment NA49 at CERN study proton-proton
interactions on at v s 17.2 GeV with large
acceptance (-0.2 ltxF lt0.2)
Possible two candidates for members in the
anti-decuplet with strangeness -2 and possible
isospin 3/2 are observed ?--3/2 ?- p-
- an exotic state ?03/2 ? p - a
non-exotic state
?(?!)
25
NA49(pp)at CERN SPS
pp ? pX
C.Alt et al., hep-ex/0310014, Phys.Rev.Lett.92,
042003(2004)
?- p-
Decay ?--3/2 ?- p- of the exotic
state with mass M 1862 2 MeV/c2 G 18
Mev/c2 Significance 4 s At the same mass the
non-exotic state decay is observed ?03/2 ?
p Corresponding antiparticles spectra show
enhancements at the same place.
?- p
?- p-
?- p
26
H1 Narrow anti-charm baryon state
M3.099 0.006 GeV
H1 Collaboration, submitted to Phys. Lett. B (Mar
2004)
27
However, not all experiments NOW looking for
pentaquarks see the signal (after 2003)
28
Summary of 2004 non-observations(by May)
Summary of Observations 2004(May)
Where Reaction Mass interval Limit Comment
BES e e-?J/? ? KNX 1520-1560 lt10-5 (branching) Azimov lt 10-5
HERA-B pA? K0p X 15 N/A vs NA49,SVD
PHENIX dAu? Kn X 1500-1600 N/A vs STAR, Dubna
CDF pp ?Z? K0p X 15251545 lt87(79) events vs ZEUS, STAR
ALEPH e e-?Z? K0p X 15251545 lt.003 (events) No D-events (K-L)
DELPHI e e-?Z? K0p X 15001750 lt.006(events) No D-events (K-L)
ZEUS ep? ? p X 1840-1880 N/A vs NA49
CDF pp? ? p X 1840-1880 126/? vs NA49
FOCUS gA ? Dp X N/A N/A vs H1
WA89 S-A? ? p X 1840-1880 N/A vs NA49
29
All previous experiments were not designed for
pentaquark search(except LEPS(03) and
DIANA).Several high statistics dedicated
experiments are now in progress
LEPS(04) is a dedicated experiment for
pentaquark search. Preliminary results are
presented by T.Nakano on March 24 and K. Hicks
on May 4. Jefferson Lab has an pentaquark
experimental program (V.D. Burkert) CLAS-G11 gt
20X increase of statistics (March-April) PQE(Jlab
04-012) gt high resolution study(running) Several
Jlab experiments are under preparation.
30
LEPS new deuterium results
New LEPS experiment (2004) ?D ? KK-n

• Preliminary data (not yet published)
• Higher statistics (5-10 times more)
• Minimal cuts on the data
• Particle ID of K, K-
• Missing mass Nucleon mass
• Remove f-meson production events
• Further cuts
• Photon energy
• Remove events with more than 2 tracks
• Remove L(1520)

31
New LEPS experiment (2004) ?D ? KK-n
Ken Hicks (Ohio University) Denver APS
Meeting May 2, 2004
LEPS gd remove L(1520)
Preliminary!
T-peak 2003 18 events 2004 100 events (x5-10
fold statistics)
32
Last news CLAS-G11(2004)
CLAS Neutron peak has about 10 times the
statistics of the earlier CLAS data.
Ken Hicks (Ohio University) Denver APS
Meeting May 2, 2004
Preliminary!
This data set will provide a high-statistics test
of the Q.
MM(KK-p)
33
AFTER COFEE BREAK

• Continue