Transcript Document

Observations of PentaQuarks:
A Mini-Review
By A. Dolgolenko and M. Kubantsev
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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Content
•Introduction
•Observations of the Θ+(1540) state: year of 2003:
First evidence from photo production (Spring-8)
} over 200 citations!
Low energy kaon beam (ITEP)
Photo/electro-production (JLAB, ELSA, HERMES)
Neutrino beam (ITEP-CERN-FNAL)
•2004 results (up to mid-May):
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
• Other possible exotic baryons.
• Further studies, summary and outlook
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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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:
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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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)
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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Indeed, history of S = +1 system
search was not encouraging:
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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Prediction of narrow and
exotic light baryons
In 1997 D. Diakonov, V. Petrov and
Z+(1530), later Θ+(1530)
M. Polyakov proposed, on basis of nK+ or pK0
S = +1
uudds
a chiral soliton model, a low-mass
anti-decuplet of pentaquarks
(qqqqq).
Predicted
0 N(1710)
lower mass, s=+1 state has mass of
1/2 1 3/2 I
1530 MeV/c2 and narrow width -3/2 -1 -1/2
Σ(1890)
<15 MeV/c2.
Three
-1
baryons in the triangle corners are
exotic.
They
Ξ(2070)
have been bold enough to persuade
-2
experimentalists to look for
uussd
ddssu
these states, so in the beginning of
Ξ0 π+ or Σ+K0
Ξ π or Σ K
2003…
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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LEPS at SPRING-8: FIRST OBSERVATION
γ
K-
K+
n
Θ+
n
S = +1 baryon resonance in
K- missing mass spectrum of
γn K+K-n reaction on
carbon was found:
Mass of 1540 ± 10 Mev/c2.
Peak significance is 4.6 σ
Peak width is < 25 MeV/c2
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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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 σ
Gaussian fit of the peak
yields:
M = 1539 ± 2 MeV/c2
Γ <9MeV/ c2
(compatible with
instrumental resolution)
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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CLAS with D target at JLAB
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ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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SAPHIR at ELSA
Θ+ signal(fit):
NΘ+= 63±13 events
M = 1540 ± 4 ± 2 MeV/c2
Γ < 25 MeV/c2
Significance: 5.2 σ
•σ(Θ+): σ(Λ0(1520))= 1:15
•No signal in Θ++ K+p
suggests isoscalar state
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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Observation of Θ+ in neutrino
interactions:ITEP-FNAL-CERN
A.E.Asratyan et al.,hep-ex/0309042
Phys. Atom.Nucl. 67,682(2004)
Neon plus Deuterium
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.
Mass=1533 ± 5 MeV/c2
Width <20MeV/c2
M.Kubantsev
ITEP,Moscow/NWU
26 events with ~15 events
of the background;
significance of 6.7 σ.
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CLAS with p-target at JLAB
V. Kubarovsky et al., hep-ex/0311046
Phys. Rev.Lett.92,032001(2004)
NΘ+= 41±10 events
M = 1555 ± 10 MeV/c2
Γ = 26 ± 7 MeV/c2
Significance: 7.8 ± 1 σ
No signal in pK+ system, so
Θ+ is possibly isoscalar
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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Dubna:C-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 σ effect(!?)
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ITEP,Moscow/NWU
~
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HERMES(e+D) at DESY
A. Airapetian et al., hep-ex/0312044,
Phys.Lett.B585,213(2004)
e+(27.6 GeV)D
K0(π+π-)pX
NΘ+= 56 events
M = 1528 ± 2.6 ± 2.1 MeV/c2
Γ = 19 ± 5 ± 2 MeV/c2
Significance: 4 – 6 σ
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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SVD(pA) at Serpukhov
A.Aleev et al., hep-ex/0401024
NΘ+= 50 events
M = 1526 ± 3.1 MeV/c2
Γ <24 MeV/c2
Significance: 4 – 6 σ
Production cross section
for XF > 0 (30-120) mkb
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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COSY -TOF
M =1530 ± 5 MeV
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ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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Evidence from e-p collider
experiment ZEUS
S. Chekanov for ZEUS:
hep-ex/0405013(latest update)
ep @ 300-318 GeV
C.M.S. energy with
integrated luminosity 121
pb-1
NΘ+= 221 ± 48 events
M = 1522 ± 3.1 MeV/c2
Γ = 8 ± 4 MeV/c2
Significance: 4.6 σ
No Θ++ observed:
isoscalar(?)
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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Preliminary results from STAR(p-p collisions)
pp @ 200 GeV C.M.S. energy
with 8 million events
Possible bump @ ~1520 Mev/c2
M.Kubantsev
ITEP,Moscow/NWU
S.Salur for STAR at RHIC:
hep-ex/0403009
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Summary of observations
Average
M.Kubantsev
ITEP,Moscow/NWU
1531±3±4
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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Summary of observations (supplemental)
Reaction and energy (GeV)
Θ++ signal
Production crosssection, μb
Collaboration
N/A
CLAS
γd→ K-p K+n
(2.5<Pγ<3.1)
γp→ K0S K+n
( Pγ<2.6)
Not seen
0.03-0.04
SAPHIR
γp→ π+ K- K+n
(3<Pγ<5)
Not seen
N/A
CLAS
ed→ pKSX
(Pe=27.6)
Not seen
N/A
HERMES
(√s=300-318)
Not seen
N/A
ZEUS
ep→ KS p()X
Not seen
pA→ pKSX
(Pp=70)
N/A
30-120
SVD
pp→Σ+K0p
(Pp=2.95)
N/A
0.4±0.1±0.1
TOF-COSY
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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The unclaimed Q+(1540) ?
CERN: K+p  pK0X
Bubble Chamber Data
A. Berthon, et al.,
Nucl. Phys. B63, 54 (1973)
1.54 GeV
Presented by V.D.Burkert at Penta-Quark 2003.
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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Estimation of Θ+ width (summary)
Experimental Θ width(upper limits or values with errors)
COSY-TOF
Dubna(CC)
SVD
NA-49
ZEUS
HERMES
SAPHIR
ITEP(ν)
CLAS(p)
CLAS(D)
DIANA
LEPS
22
26
24
10
8
20
26
20
25
21
9
25
Direct high resolution width measurements are under way now.
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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Estimation of Θ+ width (summary,cont.)
Kaon experiments
Direct observation(DIANA):
< 9 MeV
R. Cahn and G.Trilling (DIANA re-analysis)
0.9 MeV
S. Nussinov (K+n and K+d)
<6 MeV
R. Arndt et al (K+n and K+d)
<1.5 MeV
I.Strakovsky et al: PWA for K+n(I=0) with P01 (Jp=3/2+) <1-2 Mev
Other partial waves: S01(Jp=1/2-) and P03(Jp =3/2+ ) are not conclusive
W.R. Gibbs (K+d cross section re-analysis)
0.9±0.2 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) :
1.
Masses 1520 -1550 are peferable for S01 and P01
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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NA49(pp)at CERN SPS
Experiment NA49 at CERN study
proton-proton interactions on at
√ s = 17.2 GeV with large
acceptance (-0.2 <xF <0.2)
Possible two candidates for members in
the anti-decuplet with strangeness -2
and possible isospin 3/2 are observed:
Ξ--3/2
Ξ- π- - an exotic state
Ξ03/2
Ξ(?!)
Ξ– π+ - a non-exotic state
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
24
NA49(pp)at CERN SPS
C.Alt et al., hep-ex/0310014,
Phys.Rev.Lett.92, 042003(2004)
Decay
Ξ--3/2
Ξ- πof the exotic state with mass
M = 1862 ± 2 MeV/c2
Γ = 18 Mev/c2
Significance ~ 4 σ
At the same mass the non-exotic
state decay is observed:
Ξ03/2 Ξ– π+
Corresponding antiparticles spectra
show enhancements at the same place.
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
pp
Ξ πX
Ξ- π-
Ξ- π+
Ξ- π-
Ξ- π+
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H1: Narrow anti-charm baryon state
M=3.099± 0.006 GeV
uuddc
H1 Collaboration, submitted to Phys. Lett. B (Mar 2004)
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
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However,
not all experiments NOW
looking for
pentaquarks see the signal
(after 2003)
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
27
Summary of 2004 non-observations(by May)
Summary of Observations 2004(May)
Where
Reaction
Mass
interval
BES
e+ e-J/ψ  KNX 1520-1560
Limit
Comment
<10-5
Azimov:
(branching)
<
10-5
HERA-B pA K0p X
15
N/A
vs NA49,SVD
PHENIX dAu K+n X
1500-1600
N/A
vs STAR, Dubna
CDF
pp Z K0p X
1525–1545
<87(79) events
vs ZEUS, STAR
ALEPH
e+ e-Z K0p X
1525–1545
<.003 (events)
No D-events (K-L)
DELPHI
e+ e-Z K0p X
1500–1750
<.006(events)
No D-events (K-L)
ZEUS
ep Ξ π X
1840-1880
N/A
vs NA49
CDF
pp Ξ π X
1840-1880
126/?
vs NA49
FOCUS
gA  Dp X
N/A
N/A
vs H1
WA89
Σ-A Ξ π X
1840-1880
N/A
vs NA49
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
28
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 –> 20X increase of statistics (March-April)
PQE(Jlab 04-012) –> high resolution study(running)
Several Jlab experiments are under preparation.
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
29
new deuterium
New LEPS:
LEPS experiment
(2004) : γresults
D  K+K-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)
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
30
New LEPS experiment
(2004)
: γD

K+K-n
Ken Hicks (Ohio University)
Denver APS Meeting
May 2, 2004
LEPS gd: remove
L(1520)
Preliminary!
Θ-peak:
2003: 18 events
2004: ~100 events
(x5-10 fold statistics)
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
31
Last news: CLAS-G11(2004)
Ken Hicks (Ohio University)
Denver APS Meeting
May 2, 2004
Preliminary!
CLAS: Neutron peak
has about 10 times
the statistics
of the earlier
CLAS data.
This data set
will provide a
high-statistics
test of the Q+.
MM(K+K-p)
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
32
AFTER COFEE BREAK…
Continue…
M.Kubantsev
ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg,
Repino,Russia, May 21 2004
33