Norihito Muramatsu

1
Mini-Workshop on Kaon Experiments and Detectors,
5-7 Nov 2004, Mikata
Search for Pentaquark In Low Energy Kaon Beam

• Norihito Muramatsu
• RCNP, Osaka University

2
Pentaquark Search at E949

• Resonance formation reaction
• Kn?KS0p?pp-p
• -P(K)440 MeV/c
• -neutron in Sci. Tgt.
• pp-p detection
• at UTC (and others?)
• M(pp-)M(KS0)
• ? M(KS0p)M(T)
• pp- detection at UTC
• M(pp-)M(KS0)
• MM(K,pp-)M(p)
• ? M(Kn) with Fermi-correction

p
?P/P1.3
K beam 440 MeV/c s8.4 MeV
proton
p-
TOF ?v/v?t/t, vL/t, ?t200 psec ? L4 m is
equivalent to s8.4 MeV K/p separation 6 nsec
3
Toy MC simulation

• 440 MeV/c K beam in z-direction
• Fermi motion of neutron inside carbon by harmonic
  oscillator model.
• Breit-Wigner resonance
• M1540 MeV and G10 MeV
• Flat generation of KS0 and proton at CMS
• Flat generation of p and p- at KS0 rest frame
• Lorentz transformation to Lab frame

4
Kinematics in pp- detection mode
Backward production of KS0 at CMS are detected.
(26 mb for G1 MeV) vs. CEX BG is
forward peaked. (7 mb in PRD15 (1977) 1846)
p
p-
z0 cm
generated events
Polar Angle (rad)
z-20 cm
KS0
proton
z-10 cm
Momentum (GeV/c)
cos?(KS0) at CMS
5
Experimental Considerations

• Acceptance determination
• CMS energy resolution for mass measurement
• M(K and rest neutron) with Fermi corr. - true
  ECMS
• ? Validity check of Fermi corr.
• See initial works at http//www.phy.bnl.gov/e949/
• analysis/pentaquark

zlt25 cm
43.1 cm
X -10
X -20 target front edge
X 0 cm target center
z
UTC
6
Geometrical Acceptance Measurement

• In case that pp- or pp-p are detected at UTC
• two pions (KS0) two pions
  proton
• z 0 cm 0.12350.0023 0.00060.0002
• -10 cm 0.12420.0023 0.01820.0009
• -20 cm 0.10560.0021 0.06020.0017
• In case that P(K) resolution 8.4 MeV, UTC
  resolution 1.3 and RMS of beam dist. 4 cm
• two pions (KS0) two pions
  proton
• z 0 cm 0.12820.0023 0.00030.0001
• -10 cm 0.11920.0023 0.01800.0009
• -20 cm 0.10620.0021 0.06160.0017
• ? No big change in the realistic case

7
Acceptances with proton detection

• In case proton is detected at inner two layers of
  UTC.
• z-position at r30 cmlt 25 cm is assumed.
• P(K) resolution, UTC resolution and beam dist.
  are included.
• two pions proton
• z 0 cm 0.00450.0005
• -10 cm 0.04270.0014
• -20 cm 0.08310.0019 Slightly enhanced
• In case that proton Is detected at sci. target.
• ?proton lt 0.3 rad by assuming Rproton 20 cm
• two pions proton
• z 0 cm 0.04360.0004 How about resolution?
• -10 cm 0.01770.0009
• -20 cm 0.00130.0003
• Range counter instead of End-Cap?

8
Fermi Correction

• Analytical Formula
• But some approximations
• EfMnPf2/(2Mn) and neglect Pf2 terms
• cos?(K)/cos?(K-KS0)1
• ?Valid for backward KS0 productions (z0 cm)

z(r43.1 cm)lt 25 cm
All events
True CMS energy M(Kn)
cos?(K)/cos?(K-KS0)
MM(K,pp-)
9
CMS energy resolution

• No beam detector resolutions
• All fitting range
  -0.0150.015 GeV
• 11.110.12 8.310.12 MeV
• Changing beam res. with UTC res. 1.3
• 8.4 MeV 11.610.12 8.740.12 MeV
• 20 MeV 12.910.11 10.940.21 MeV
• 30 MeV 14.260.11 12.310.29 MeV
• 40 MeV 15.770.11 14.280.45 MeV
• 50 MeV 17.620.12 17.110.78 MeV
• Changing UTC res. with beam res. 8.4 MeV
• 1.3 11.610.12 8.740.12 5.070.17 MeV
• 3.0 13.000.12 10.310.18 10.790.46 MeV
• 4.5 14.910.13 12.450.31 15.650.83 MeV
• 6.0 17.290.15 14.800.51 22.881.35 MeV
• 10 MeV resolution is retained in the realistic
  case

Resolution of M(pp-p) meas. in case of
3-track detection at UTC. Compared with true CMS
energy.
10
Beam Momentum Setting

• P(K)442 MeV/c for M(T)1.540 GeV
• but
• P(K)417 MeV/c for M(T)1.530 GeV (world
  ave.)
• True CMS energy is spread by 50 MeV
• because of neutron Fermi motion
• Beam Momentum should be
• adjusted at several points
• in each 30-40 MeV/c

True CMS energy M(Kn)
11
Summary

• Existence of pentaquark can be confirmed by E949
• detector. (There are many null results in
  high energy
• experiments.)
• Two pion detection at UTC seems promising.
• (Geometrical acceptance 10)
• Two pion proton detection at UTC may be
  analyzed
• for z-20 cm.
• 10 MeV ECMS resolution can be achieved in the two
  
• pion detection mode with Fermi correction.
  (Nakano
• suggested MM(K,pp-)gt0.97 reduces ECMS res.
• to 6 MeV with a cost of some acc. loss and
  slight
• peak shift.) Note that energy resolution with
  two
• pions proton detection is 5 MeV.
• Beam momentum setting
• several points in each 30-40 MeV/c.