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[bds 231] Physics effects of ILC parameters



Dear colleagues,

to get a first idea of effect the ILC parameters on physics I looked into the Higgs recoil mass measurement at 350 GeV. The attached file shows the sqrt{s} spectrum for nominal (solid) lowP (dashed) and highL (dotted) in the upper plot and the reconstructed recoil mass in the lower plot. The plot contains neither beam spread nor detector. However since, as you see, the additional smearing moves the events from the peak to far away, this doesn't matter for a crude estimate of the effect.

For lowP and highL there is a factor 0.7 less events in the peak for the same luminosity, so for zero background the statistical error gets larger by a factor 1/sqrt(0.7). Taking the TESLA TDR as reference and integrating over the relevant region the signal/background is about 1/1. Since the background should be little effected by the beam parameter also this value goes to 0.7/1. Since the statistical error in presence of background has to be divided by sqrt(purity) you need in the end a factor 1.8 more luminosity for lowP and highL compared to norm to arrive at the same statistical error. For the systematics you can only guess that it increases as well with the beamstrahlung.

Of course this applies to exactly this one analysis and has to be redone for every channel of interest. However the factor 0.7 comes from the number of events in the peak at nominal beam energy, so it should be roughly applicable for all channels where narrow resonances are involved.

        Best wishes,

                          Klaus

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         | Klaus  Moenig     e-mail: Klaus.Moenig@xxxxxxx |
         | DESY, Zeuthen         or: Klaus.Moenig@xxxxxxx |
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