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Search for Pentaquark in Low Energy Kaon Beam

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Search for Pentaquark. in Low Energy Kaon Beam. Norihito ... Mini-Workshop on Kaon Experiments and Detectors, 5-7 Nov 2004, Mikata. Pentaquark Search at E949 ... – PowerPoint PPT presentation

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Title: Search for Pentaquark in Low Energy Kaon Beam


1
Search for Pentaquark in Low Energy Kaon Beam
Mini-Workshop on Kaon Experiments and Detectors,
5-7 Nov 2004, Mikata
  • 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 at CMS (26 mb for G1 MeV)
vs. CEX BG (forward peaked, 7 mb in PRD15
(1977) 1846)
p
p-
All
z0 cm
Polar Angle (rad)
KS0
proton
z-20 cm
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 Not so 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
  • 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

pp-p detection at UTC
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 20 points
  • in each 10-20 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 two
    pion detection mode with Fermi correction.
    (Nakano suggested MM(K,pp-)gt0.97 reduced ECMS
    res. to 6 MeV with a cost of 80 acc. loss and
    slight peak shift.) Note that energy resolution
    with two pions proton detection is 5 MeV.
  • Beam momentum setting 20 points in each 10-20
    MeV/c.
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