Upload
zane-kinman
View
214
Download
0
Embed Size (px)
Citation preview
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
1
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
2
•Introduction
•Observations of the Θ+(1540) state: year of 2003:
•2004 results (up to mid-May):
• Other possible exotic baryons.
• Further studies, summary and outlook
Content
First evidence from photo production (Spring-8) Low energy kaon beam (ITEP) Photo/electro-production (JLAB, ELSA, HERMES)
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
Neutrino beam (ITEP-CERN-FNAL)
} over 200 citations!
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
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:
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
4
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)
Why is the Baryon State called Exotic?
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
5
Indeed, history of S = +1 system search was not encouraging:
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
6
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, s=+1 state has mass of 1530 MeV/c2 and narrow width <15 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…
-1
Z+(1530), later Θ+(1530)
S = +1
N(1710)
Σ(1890)
Ξ(2070)
nK+ or pK0
uudds
uussdΞ0 π+ or Σ+K0ddssu
Ξ- π- or Σ-K-
Prediction of narrow and exotic light baryons
0
-2
-3/2 I-1/2 1/2 3/2-1 1
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
7
LEPS at SPRING-8: FIRST OBSERVATION
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
γ K-
K+
nn Θ+
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
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 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
9
CLAS with D target at JLAB
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
10
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
SAPHIR at ELSA
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
11
26 events with ~15 events of the background;significance of 6.7 σ.
Neon plus Deuterium
Mass=1533 ± 5 MeV/c2
Width <20MeV/c2
Observation of Θ+ in neutrino interactions:ITEP-FNAL-CERN
A.E.Asratyan et al.,hep-ex/0309042Phys. Atom.Nucl. 67,682(2004)
Re-analysis of data from FNAL (E180,E632) and CERN(WA21,WA25,WA59) bubble chamberswith H, D, Ne fills.
Signal is seen only on D and Ne.
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
12
CLAS with p-target at JLAB
V. Kubarovsky et al., hep-ex/0311046Phys. Rev.Lett.92,032001(2004)
NΘ+= 41±10 events
M = 1555 ± 10 MeV/c2 Γ = 26 ± 7 MeV/c2 Significance: 7.8 ± 1 σNo signal in pK+ system, so
Θ+ is possibly isoscalar
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
13
Propane 2-meter bubble chamber in heavy ion beam (C) of Dubna accellerator.
The signal is impressive: ~ 9 σ effect(!?)
R. Togoo et al., Proc. MongolianAcad.Sci.,4(2003),2
Dubna:C-C interactions at 4.2 GeV/nucleon
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
14
A. Airapetian et al., hep-ex/0312044,Phys.Lett.B585,213(2004)
HERMES(e+D) at DESY
NΘ+= 56 events
M = 1528 ± 2.6 ± 2.1 MeV/c2
Γ = 19 ± 5 ± 2 MeV/c2
Significance: 4 – 6 σ
e+(27.6 GeV)D K0(π+π-)pX
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
15
SVD(pA) at SerpukhovA.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
16
COSY -TOF
M =1530 ± 5 MeV
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
17
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(?)
Evidence from e-p collider experiment ZEUS
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
18
S.Salur for STAR at RHIC:hep-ex/0403009
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
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
19
Average 1531±3±4
Summary of observations
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
20
Summary of observations (supplemental)Reaction and energy (GeV) Θ++ signal
Production cross-
section, μbCollaboration
γd→ K-p K+n (2.5<Pγ<3.1)
γp→ K0
S K+n ( Pγ<2.6)
γp→ π+ K- K+n (3<Pγ<5)
ed→ pKSX (Pe=27.6)
ep→ KS p()X (√s=300-318)
pA→ pKSX (Pp=70)
pp→Σ+K0p (Pp=2.95)
Not seen
Not seen
Not seen
Not seen
Not seen
N/A
N/A
N/A
0.03-0.04
N/A
N/A
N/A
30-120
0.4±0.1±0.1
CLAS
SAPHIR
CLAS
HERMES
ZEUS
SVD
TOF-COSY
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
21
CERN: K+p pK0X Bubble Chamber Data
1.54 GeVA. Berthon, et al., Nucl. Phys. B63, 54 (1973)
The unclaimed (1540) ?
Presented by V.D.Burkert at Penta-Quark 2003.
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
22
Estimation of Θ+ width (summary)
Direct high resolution width measurements are under way now.
Experimental Θ width(upper limits or values with errors)
259
2125
2026
208
1024
2622
LEPSDIANA
CLAS(D)CLAS(p)ITEP(ν)
SAPHIRHERMES
ZEUSNA-49
SVDDubna(CC)COSY-TOF
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
23
Estimation of Θ+ width (summary,cont.)Kaon experiments
Direct observation(DIANA): < 9 MeV
R. Cahn and G.Trilling (DIANA re-analysis) 0.9 MeVS. Nussinov (K+n and K+d) <6 MeVR. Arndt et al (K+n and K+d) <1.5 MeVI.Strakovsky et al: PWA for K+n(I=0) with P01 (J
p=3/2+) <1-2 MevOther partial waves: S01(J
p=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) :
• Masses 1520 -1550 are peferable for S01 and P01
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
24
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– π+ - a non-exotic state
Ξ(?!)
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)
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
25
Decay Ξ--
3/2 Ξ- π-
of the exotic state with mass M = 1862 ± 2 MeV/c2
Γ = 18 Mev/c2 Significance ~ 4 σAt the same mass the non-exoticstate decay is observed:Ξ0
3/2 Ξ– π+
Corresponding antiparticles spectrashow enhancements at the same place.
Ξ- π-
Ξ- π-
Ξ- π+
Ξ- π+
NA49(pp)at CERN SPS
C.Alt et al., hep-ex/0310014,Phys.Rev.Lett.92, 042003(2004)
pp Ξ πX
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
26
H1 Collaboration, submitted to Phys. Lett. B (Mar 2004)
M=3.099± 0.006 GeV uuddc
H1: Narrow anti-charm baryon state
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
27
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
28
Summary of Observations 2004(May)
Where Reaction Mass interval
Limit Comment
BES e+ e-J/ψ KNX 1520-1560
<10-5 (branching)
Azimov: < 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 A Dp X N/A N/A vs H1
WA89 Σ-A Ξ π X 1840-1880
N/A vs NA49
Summary of 2004 non-observations(by May)
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
29
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.
All previous experiments were not designed for pentaquark
search(except LEPS(03) and DIANA).Several high statistics
dedicated experiments are now in progress:
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
30
LEPS: new deuterium results• 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 -meson production events
• Further cuts:– Photon energy– Remove events with more than 2
tracks– Remove (1520)
New LEPS experiment (2004) : γD K+K-n
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
31
New LEPS experiment (2004) : γD K+K-n
LEPS d: remove (1520)
Ken Hicks (Ohio University)
Denver APS Meeting
May 2, 2004
Θ-peak: 2003: 18 events2004: ~100 events(x5-10 fold statistics)
Preliminary!
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
32
Last news: CLAS-G11(2004)
CLAS: Neutron peak has about 10 timesthe statistics of the earlierCLAS data.
This data setwill provide a high-statisticstest of the +.
MM(K+K-
p)
Ken Hicks (Ohio University)
Denver APS Meeting
May 2, 2004 Preliminary!
M.Kubantsev ITEP,Moscow/NWU
HSQCD-2004,St.Petersburg, Repino,Russia, May 21 2004
33
AFTER COFEE BREAK…
Continue…