×¥ + n  K 0 + › With decays: K 0 ...

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Proposal for an Experiment: Photoproduction of Neutral Kaons on Deuterium Spokespersons: D. M. Manley (Kent State University) W. J. Briscoe (The George Washington University) A. Starostin (UCLA). ץ + n  K 0 + Λ With decays: K 0  π 0 + π 0 Λ  π 0 + n - PowerPoint PPT Presentation

Transcript of ×¥ + n  K 0 + › With decays: K 0 ...

  • Proposal for an Experiment: Photoproduction of Neutral Kaons on Deuterium Spokespersons: D. M. Manley (Kent State University)W. J. Briscoe (The George Washington University)A. Starostin (UCLA)

    + n K0 +With decays: K0 0 + 0 0 + n 0 + Net reaction: + n 6 + n

  • The elementary strangeness photoproduction reactions

    + pK+ + + pK+ + 0 + pK0 + + + nK0 + + nK0 + 0 + nK+ + -

    Kaon photoproduction is a fundamental process and an important tool for gaining new insights into nucleon resonances. Focus of this proposal is reaction (4), which serves as an isospin filter for N* resonances. Until very recently, there have been no experimental studies of this reaction.

  • Integrated cross section for -pK0 as a function of c.m. energy WPrior PWAs and quark-model predictions suggest appreciable K couplings for S11(1650) and P11(1710).

    There is a possible hint of a narrow structure in the cross section near 1.7 GeV that merits investigation.

  • Isobar-model predictions for pK+ and nK0 using two different parameter sets(a) and (c): predicted angular distributions at E = 1.05 GeV

    (b) and (d): predicted total cross sections

    These calculations show the urgent need for nK0 data to constrain the models.

  • Theoretical considerationsThe nK0 reaction is expected to help clarify the strangeness production mechanism because of the following features:

    In contrast to pK+, the Born term in the t channel does not contribute to nK0 because no charge is involved.

    The strong coupling constants in the u channel for 0 and other isovector exchanges have the same value but are of opposite sign to those in pK+ because of isospin symmetry.

    The electromagnetic coupling constants of resonances in the s channel (e.g., gN*n) and in the t channel are different from those in pK+.

    The nK0 reaction excites only I= N* resonances in the s channel. At MAMI-C, we expect good statistics up to E = 1400 MeV, corresponding to a c.m. energy W = 1.85 GeV. Thus, we have full coverage of the second resonance region.

  • Prior measurementsUntil very recently, there were NO experimental investigations of nK0:

    2006 Data were measured in Fall 2006 as part of the g13 experiment at JLab for E = 0.4-1.9 GeV and 0.5-2.5 GeV using tagged photons with circular polarization; no results of analysis have yet been published. [E. Munevar, B.L. Berman, and P. Nadel-Turoski (CLAS Collaboration), AIP Conf. Proc. 947, 146 (2007).]

    2007 Quasifree production of neutral kaons on 12C was measured for E = 0.8-1.1 GeV using tagged photons at LNS of Tohoku University in Sendai, Japan. Momentum spectra and integrated cross sections were obtained, but d/d could not be obtained due to limited kinematical acceptance. [T. Watanabe et al., Phys. Lett. B 651, 269 (2007).]

    2008 First measurement of K0 photoproduction on deuterium was reported. Data were measured for E = 0.8-1.1 GeV using tagged photons at LNS of Tohoku University in Sendai, Japan. Extracted momentum spectra differed considerably in shape and magnitude from those predicted with Kaon-MAID. [K. Tsukada et al., Phys. Rev. C 78, 014001 (2008).]

  • Detector efficiency for nK0 calculated from MC simulation

  • Detector efficiency for background reaction pK0+

  • December 2007 Test Run at MAMI-CDuring 5-21 December 2007, 277 hours of beam time using unpolarized tagged photons incident on a LD2 target were obtained. Experimental parameters are listed below:

    Electron maximum beam energy: 1.508 GeVTagged photon energy range : 0.4 1.4 GeVBeam current: 10-20 nARadiator: 10 m CuDiameter of collimator: 4 mmTarget: Liquid deuteriumTarget cell length: 4.76 0.03 cmCB multiplicity: 2+

    Some results of our analysis of these data will now be presented using kinematic fitting for event selection.

  • Invariant mass of 2 from all 6-cluster events (no kinematic fitting)(Possible Combination of 6 to yield a 0 )+ = 0

  • Kinematic fit and confidence level

  • Z-vertex of primary interaction from kinematic fit

  • Distance travelled by K0 and

  • Invariant mass of 2 photons from pions produced in K0 decays in nK0 with kinematic fittingInvariant mass of 2 photons from decay KS 204 in events identified as from nK0.

  • Invariant mass of 4 photons in nK0Invariant mass of 4 photons fromdecay of KS in events identified as from nK0.

  • Missing mass of 4 photons in nK0Missing mass of 4 photons fromdecay of KS in events identified as from nK0.

  • Missing mass of 4 photons in pK0+Missing mass of 4 photons fromdecay of KS in events identified as from pK0+.

  • Summary and beam-time requestOur main objective is to measure d/d for nK0 with a precision of about 11%. We will also measure the recoil polarization.

    We need the maximum beam energy for MAMI-C, a 5-cm liquid deuterium target, and unpolarized (or circularly polarized) photons. We require a high multiplicity trigger.

    We will simultaneously measure d/d for pK0+, which will provide a check of systematics since there are published cross sections for this reaction with which to compare our results.

    Our requested beam time for data taking is 400 hours.