Today's Progress 21. Aug. 2006

(stoppedK^-, p) inclusive spectrum and its classification with reaction timing/DCA

Here, (stoppedK^-, p) inclusive momentum spectrum (energy-loss-corrected) and its classification is developed, with E549 100% statistics.

(stoppedK^-, p) inclusive spectrum

Here, definition of the term, inclusive , is

1. Triggerwise requirement - the Kstop-Charged trigger bit is "ON". We do not care about other bits(components).

2. BLC tracking is succeeded.

3. PDC tracking is succeeded. 1 track on at least PDC L or R. i.e. Possible proton number is up to 2 in an event.

4. Reaction vertex is within the target cell - fiducial volume selection.

5. Stopped kaon selection with Kstop ID function.

6. Proton selection on PB/NT with proton ID function.

(stoppedK^-, p) inclusive spectrum from each of PB segments.
(stoppedK^-, p) inclusive spectrum from L(black) and R(red) arms.
(stoppedK^-, p) inclusive spectrum.

DCA-gated spectra

Below, DCA-selected spectra are exhibitted. The black-colored spectrum is the one with DCA<5.0 mm, while the red-colored is the one with DCA > 5.0 mm. Note that the proton from

  • The primary proton of non-pionic absorption
  • Formation of tri-baryonic states
    • are tend to belong to the black-spectrum, while those from
  • secondary proton from Lambda/Sigma^+ decay
    • are to the red, although the selection power is not very strong by kinematical reason.

    The DCA spectrum for proton events from stop K^- on 4He same is shown below.

    Prompt-timing-gated spectra

    Now, we classify the 4He(stopped K^-, p) spectrum by the value of

    DeltaT(T0->PA) = Tpa - Tt0 - TOFkstop - TOFsec.

    The gate conditions are:

    A. DeltaT(T0->PA) < -0.3 - large in-flight contamination is expected (black)

    B. | DeltaT(T0->PA) | < 0.3 - events from primary reaction (red)

    C. 0.3 < DeltaT(T0->PA) < 0.8 - delayed events from long-lived atomic orbit or possibly Lambda decay (green)

    D. 0.8 < DeltaT(T0->PA) - delayed events from long-lived atomic orbit (sky-blue)

    .

    The resulting spectra are overlayed below. When prompt-gate-timing is selected (condition B - red), then the component from two-nucleon phase space looks emphasized.