04.09.2003 Yuri Gouz (IHEP Protvino)

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Study of the reaction p-p ? ?p0n at the VES
spectrometer. Yu. Gouz (VES collaboration)
VES collaboration D.Amelin, Yu.Gavrilov,
Yu.Gouz, V.Dorofeev, R.Dzhelyadin, I.Kachaev,
V.Kabachenko, A.Karyukhin, Yu.Khokhlov,
A.Konoplyannikov, V.Konstantinov, V.Kostyuhin,
V.Matveev, V.Nikolaenko, A.Ostankov, B.Polyakov,
D.Ryabchikov, A.Solodkov, O.Solovianov,
E.Starchenko, A.Zaitsev, A.Zenin.

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• The final states ?p and ?p are mostly
  interesting for the P-waves, which have exotic
  quantum numbers JPC1- .
• It was noticed in that P-waves in ?p and ?p
  are essentially different in ?p they mainly
  belong to SU(3)-octet (hybrid, ), while in
  ?p they belong to higher SU(3) representations
  and can be interpreted as 4-quark states.
• The ?(?)p can be produced in diffraction and
  charge exchange reactions. The diffraction
  reactions p- A ? ?pA and p- A ? ?pA and charge
  exchange reaction p- p ? ?p0 n are studied here
  is the first study of p- p ? ?p0 n.

S.U.Chung, E.Klempt, J.G.Körner, SU(3)
classification of P wave ?? and ?? systems,
Eur.Phys.J.A15539-542,2002, hep-ph/0211100

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• The events of the reaction p- p ? ?p0 n were
  selected in the decay mode ? ? pp?, ?
  ? ??, p0 ? ??.
• The reaction p-p ? ?p0 n was also studied, for
  normalizations and comparisons, in the decay mode
  ? ? ppp0, p0 ? ??.

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?p0 event selection

• Selection criteria
• 2 tracks, for p and p, and 4 photons
• 0.105ltM(?1?2)lt0.165 MeV (p0)
• 0.478lt M(?3?4)lt0.618 MeV (?)
• the 4? should not satisfy the p0 p0 hypothesis
• 0.938ltM(pp?)lt0.978 MeV (?)
• the ppp0 should not satisfy the ? hypothesis
• the side bands around ? were used for the
  background evaluation and subtraction
• 2630 signal and 1415 background events were
  selected for the analysis.

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?p0 distributions

• The a2(1320) peak seen in the ?p0 mass spectrum
• The t-distribution peaks at 0

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?p0 distributions (contd)

• Significant asymmetry in the cos?GJ distribution
• The fTY spectrum shows the dominance of negative
  exchange naturality waves

The asymmetry in cos?GJ is not coming from the
acceptance the background distribution is flat.
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?p0 event selection

• Selection criteria
• 2 tracks, for p and p, and 4 photons
• 0.105ltM(?1?2), M(?3?4)lt0.165 MeV (p0)
• 0.528ltM(ppp0)lt0.568 MeV (?)
• the side bands around ? were used for the
  background evaluation and subtraction
• 18547 signal and 8436 background events were
  selected for the analysis.

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?p0 distributions

• a0(980) and a2(1320) are seen in the mass
  spectrum
• asymmetry in the cos?GJ distribution
• The fTY distribution shows significant fraction
  of positive exchange naturality waves
• In agreement with previous studies of the ?p0
  system .

• D.Alde et al (GAMS collaboration), Phys. At.
  Nucl. Vol. 62 No. 3 (1999), p 421
• A.R.Dzierba et al, Phys. Rev. D67, 094015 (2003)

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a2(1320) in ?p0 and ?p0
The mass distributions are acceptance corrected
agrees with previous measurements (VES, E852)
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?p0 PWA
The conventional PWA of the ?p0 system, with S0,
P0, P-, D0, D- waves in the unnatural parity
exchange sector and P and D in the natural
parity exchange sector, was performed. The
results are also in agreement with results of
GAMS and E852.
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?p reminder
The exotic wave is dominant in the natural parity
exchange sector (P wave). It forms a bump at
1.6 GeV, and is most intensive above a2(1320),
1.45ltMlt1.9 GeV.
G.M.Beladidze et al (VES collaboration),
Phys.Lett.B313(1993) 276
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?p reminder
Here the D wave is dominant. The P wave is the
most intensive among P waves. It forms a broad
bump at 1.4 GeV.
G.M.Beladidze et al (VES collaboration),
Phys.Lett.B313(1993) 276
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?p0 at 1.45ltMlt1.9 GeV/c2

• The fTY spectrum is almost flat
• still significant asymmetry in cos?GJ
• t distribution peaks at 0
• ? JPC1- seems to be mainly produced in
  unnatural parity exchange (P0 wave)

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?p0 at 1.45ltMlt1.9 GeV/c2

• These spectra show that positive exchange
  naturality waves dominate
• significant asymmetry in cos?GJ
• fTY distribution is almost cos2
• t distribution has a dip at 0

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PWA in big bin (1.451.9 GeV) ?p0
The PWA of both ?p0 and ?p0 was performed for
events in the whole interval of 1.451.9 GeV
there are no rapid acceptance variations for the
two processes, neither rapid phase variations (in
?p0). The analysis included usual wave set S0,
P0, P-, D0, D-, P, D.

• Here ?p0 is shown.
• The D0 wave is dominant
• S0 and P0 are significant
• P and D are small

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PWA in big bin (1.451.9 GeV) ?p0
In ?p0 the P and D are dominant.
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We can evaluate the ratio of matrix elements
squared for the production of P wave in ?p0 and
?p0 systems taking into account branching
ratios of ? and ? and phase space factors, we
obtain
So the P wave in ?(?) p0 systems is produced in
the decuplet state (see SU(3) classification
). Given the P wave production in this
reaction is dominated by the ? trajectory
exchange, we can conclude that the coupling of
hybrid 1- states to ?p channel is suppressed.
This agrees with the VES result of
non-observation the bump at 1.6 GeV in the 1-
(?p) wave (I.Kachaev, talk at HADRON01). In
contrary, for the P0 wave the ratio of matrix
elements squared is higher, 0.70.3. The P0
wave production is dominated by the b1 trajectory
exchange, so the octet (hybrid) 1- state is
connected to the b1 p channel. Indeed, in VES
data the bump at 1.6 GeV was seen in the 1-
wave in b1 p (V.Dorofeev, talk at HADRON01).
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Conclusion

• The reactions p-p ? ?p0 n and p-p ? ?p0 n were
  studied at the VES setup
• The ratio of branchings for the a20 meson was
  determined Ra20.0470.019, in agreement with
  measurements in the ?p and ?p final states.
• The P waves were studied in ?p0 and ?p0 systems
  in the region of 1.451.9 GeV, where the P wave
  production in the ?p systems is most intensive.
  
• It was found that in this mass interval in the
  ?p0 system the P wave production is small, and,
  in particular, much smaller than in the ?p0
  system. From the other hand, the P0 wave
  intensity in the ?p0 system is comparable with
  that in the ?p0 system. This means that the
  coupling of hybrid JPC1 states to the ?p
  channel is significantly suppressed with respect
  to the b1 p channel.

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?p0 PWA (for the completeness)
The ?p0 statistics is not sufficient for PWA
here an attempt in 100 MeV bin is shown.