Introduction: Pentaquarks

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Kai-Thomas Brinkmann CAP 2005 June 6, 2005
Search for the Pentaquark(s)
www.frauenkirche-dresden .org

• Introduction Pentaquarks
• Experimental Evidence
• Experiments Searching for the T
• Other Pentaquark States
• Summary and Outlook

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Introduction Pentaquarks

• Quark model hadrons qq and qqq
• Other states not ruled out!
• Soliton model calculation antidecuplet set of
  5q states qqqqq
• New family of (exotic) baryons!

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Introduction Pentaquarks
T S 1 mass 1530 MeV/c2 small width G lt
15 MeV M.V. Polyakov et al., EPJA 9 (00)
115 G 2-4 MeV D. Diakonov, V.Petrov,
hep-ph/0505201 T ? K0p and Kn
MNK GeV/c2
Evidence from a number of experiments using
different combinations of targets and probes
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Experimental Evidence
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Experimental Evidence
Saphir
CLAS
Saphir, PLB572,127(03)
?p ? K0 ?? ? K0(n)K? M (15404 2) MeV G lt 25
MeV 4.8 s not seen in pK?
?d ? pK- ?? ? pK- (n)K? M (15425) MeV G lt 21
MeV 5.3 s
CLAS, PRL91,252001(03)
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Experimental Evidence
T(1530)
?(1520)
ZEUS, hep-ex/0404007 (YITP workshop, Kyoto,
Japan, Feb. 2004)
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Experimental Evidence
Gaussian statistical significance estimated
background fluctuation
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Experimental Evidence
A number of experiments do not see a signal

• BaBaR, Delphi, BES, CDF, HyperCP, E690, HERA-B,
  Aleph, Phenix
• very high statistics and excellent resolution
• high energy
• inclusive
• ee- or hadronic probes

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Experimental Evidence
BaBar upper limits on T and ?5 production (2
MeV mass resolution)
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Experimental Evidence
BaBar upper limits on T and ?5-- production
hep-ex/0502004
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Experimental Evidence
A number of experiments do not see a signal

• BaBaR, Delphi, BES, CDF, HyperCP, E690, HERA-B,
  Aleph, Phenix
• very high statistics and excellent resolution
• high energy
• inclusive
• ee- or hadronic probes

and, just recently, CLAS in ?p?K0K(n)
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?p?KK0(n)
Comparison between Saphir and new CLAS results,
see R. deVitas talk at the APS spring meeting,
TAMPA, 2005
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Indirect Evidence KN scattering
Haidenbauer, Krein (PRC68, 052201 (2003))
Workman, Arndt et al. (PRC70, 028201(04))
Scattering (and charge exchange) data suggest G lt
1 MeV
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Experiments Searching for the T
pp ? ST, T ? K0p / Kn
Production in pp with high cross
sections Strangeness tagging
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• 184 m circumference
• 1011 protons per filling
• _at_ 620 MeV (25 mA, T 600 ns)
• PcMAX 3,65 GeV
• ?p/p ? 10-4, ? ? mm mrad
• (1 mm Ø 0,18) beam cooling
• up to 80 polarization

• Extracted beam
• 105...109 protons /s in spill
• 1 s...gt2 min spill, 5 s inter-spill
• OR 2109 p in 200 ns
• Quasi-DC, polarized

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M. Fritsch, Ch. Hess, H.Koch, W. Meyer, E. Radke,
G. Reicherz, A.Wilms Institut für
Experimentalphysik, Ruhr-Universität Bochum,
D-44780 Bochum, Germany H. Dutz, A. Raccanelli,
A. Wagner Phys. Institut der Universität Bonn,
D-53115 Bonn K.-Th.Brinkmann, S.Dshemuchadse,
H.Freiesleben, R.Jäkel, L.Karsch, E.Kuhlmann,
M.Schulte-Wissermann, G.Y.Sun, W.
Ullrich Institut für Kern- und Teilchenphysik,
Technische Universität Dresden, D-01062 Dresden,
Germany W.Eyrich, J.Georgi, A. Lehmann, H.Mörtel,
L.Pinna, C.Pizzolotto, W.Schroeder, F.Stinzing,
A.Teufel, M.Wagner, St.Wirth Physikalisches
Institut, Universität Erlangen-Nürnberg, D-91058
Erlangen, Germany M.Abdel-Bary, S.Abdel-Samad,
M.Drochner, A.Gillitzer, K.Kilian, S.Marwinski,
H.P.Morsch, N.Paul, J. Ritman, E.Roderburg, S.
Schadmand, T.Sefzick, A.Ucar, P.Wintz,
P.Wüstner Institut für Kernphysik, FZ Jülich,
D-52425 Jülich, Germany and Zentral Labor für
Elektronik , FZ Jülich, D-52425 Jülich,
Germany A.Filippi, S.Marcello Dipartimento di
Fisica Sperimentale, University of Torino,
I-10125 Torino, Italy and INFN, Sezione di
Torino, I-10125 Torino, Italy H.Clement, E.
Doroshkevich, K. Ehrhardt, A. Erhardt, P.
Gonser, G.J.Wagner Physikalisches Institut,
Universität Tübingen, D-72076 Tübingen,
Germany P.Michel, K.Möller, L. Naumann Institut
für Kern- und Hadronenphysik, FZ Rossendorf,
D-01314 Dresden, Germany P. Zupranski, Soltan
Institut for Nuclear Studies, PL-00681
Warsaw supported by BMBF Verbundforschung FZ
Jülich (FFE), EU-LIFE Program
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The COSY-TOF experiment high-acceptance
Time-of-Flight spectrometer with vertex tracking
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The COSY-TOF experiment
COSY-TOF designed to identify strangeness
(pp ? pK?, pK0S, pKS0, nKS)

• Reaction identification
• primary track ? proton
• delayed decay V of KS ? ?? without start
  scintillators / Si
• decay of ?, kink
• time-of-flight of proton

pp ? pKSS Search for the T
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EXPERIMENT MODEL
pp ? pK? Resonances in strangeness production
PDG 2003
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pp ? pKSS Reaction identification
using geometry

• Ks decay V mass of pp-
• missing mass of track w/ kink (S) from event
  topology

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pp ? pK0S Search for the ??
COSY-TOF collaboration PLB595 (04) 27
Sum of two experiments (in 00 and 02) yields
about 1000 events of pp ? pKSS

• Excursion in K0p spectrum at
• mass (1530 5) MeV/c²
• width lt 18 MeV/c² (FWHM)
• compatible with detector resolution
• statistical significance of 4-6 s
• cross section (0.40.1stat0.1sys) µb

K0p
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pp ? pK0S Search for the ??
COSY-TOF collaboration PLB595 (04) 27
Sp
acceptance correction using phase space
K0p
K0p
K0p
K0S
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pp ? pK0S Search for the ??
? COSY-TOF beam time October / November 2004

• improved experimental setup
• 109 raw events taken to tape
• expect about factor 5 in pKs statistics over
  published result (gt 5000 pKs events, 300 in peak
  if signal persists)
• analysis ongoing and improved with respect to
• blind analysis ½ of the data to optimize
  analysis, rest for result
• independent analysis at several institutes in
  parallel with different codes, emphasis on
  different detector aspects
• systematics of Monte-Carlo treatment
• use of redundant information (ToF of proton and
  pions, energy losses, ...)
• common calibration database

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pp ? pK0S Search for the ??
? COSY-TOF beam time October / November 2004

• data on disk
• calibration method ready
• one-time cal. parameters done
• geometry implemented
• Monte Carlo all approaches compatible
• reconstruction software modifications in
  progress
• runwise calibration in progress
• data reconstruction next step

4 hours of running
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Experiments on the properties of the ??

• Measureable quantum numbers
• isospin ? look at other channels, e.g. Kp
• parity ? pp with double polarization

Hanhart et al., hep-ph0410293 PLB590(04)39
PLB606(05)67
K only
K only
K and K
pp?ST
P
(-)LSI -1
P
measure excitation function for ?? (3P0,1) 3sS
½s0(2AxxAyy) (and ?? (1S0) for
reference)
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Experiments Searching for the T
www.frauenkirche-dresden .org

• All running experiments in the field have started
  programs to prove the existence of the exotics.
• CLAS p and d target
• SPring8 higher statistics
• First results with high statistics from CLAS do
  not support the SAPHIR evidence on the proton.

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Other Pentaquark States
NA49
C. Alt et al., PRL92, 042003 (04)
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Other Pentaquark States
No signal seen in pK ? Isoscalar state
hep-ex/0411027, Pentaquark 2004 proceedings
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Other Pentaquark States
A. Aktas et al., PLB588,17 (04)
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Summary and Outlook
www.frauenkirche-dresden .org

• Several experiments have seen evidence for a
  manifestly exotic (S 1) T(1530) in the 5s
  range.
• If it exists, it likely is an isoscalar, spin ½
  (?) baryon of unknown parity.
• Experimental programs focussing on this object
  are under way.
• Hadroproduction will add usefull complementary
  information.