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0005
0006 =============================
0007
0008 RecHitD
0009
0010 =============================
0011 author: Stoyan Stoynev, NU
0012
0013
0014 This rechit builder uses much of the code (a copy) from RecHitB.
0015 The substantial difference is that no Gatti fitting is applied
0016 for strip hit coordinate (and error) estimation. However the Gatti
0017 distribution is virtually used.
0018
0019 Step one:
0020 A position estimator called X_Florida is used for initial position
0021 estimation. Three charges from the three adjacent strips are the input.
0022 These are charges from three time bins summed. Besides, every charge
0023 in a time bin is XTalk corrected (see CSCXonStrip_MatchGatti::setupMatrix()).
0024 No negative charges are allowed after the XTalk correction!
0025 X_Florida = (RightCharge - LeftCharge)/(CentralCharge - min(Left, Right))
0026
0027 Step two:
0028 A correction to X_Florida is made. It depends on the strip width and
0029 X_Florida itself. These corrections are parametrized in
0030 HardCodedCorrectionInitialization.cc. A linear interpolation is applied
0031 between points.
0032 The corrections are obtained in the following way.
0033 The gatti distribution (induced charge distribution) is generated
0034 for specific strip width. Then for a given offset (simulating the
0035 hit offset from the center of the strip) the charges for the three strips are
0036 extracted and X_Florida is calculated. The initial offset is
0037 in fact X_Gatti (the maximum of the distribution is at X_Gatti
0038 by definition), i.e. the position within the strip as predicted by
0039 the Gatti distribution.
0040 The correction is Correction = X_Gatti - X_Florida (there are no
0041 ambiguities) or in other words - the correction that should be
0042 applied to X_Florida in order to obtain X_Gatti.
0043 Thus the corrected X_Florida is effectively X_Gatti.
0044 In reality various systematic factors make this only an approximation
0045 (which is also true when we use a real Gatti fitting!).
0046
0047 Step three:
0048 The uncertainty of the position is calculated by error propagation.
0049 Studies show that three factors play a role:
0050 Noise, XTalk asymmetry (or similar effects), constant term. These three
0051 factors should be obtained by studies.
0052
0053 Note: The theoretical Gatti distribution depends on chamber parameters
0054 (of course). For all but ME1/1 chambers the relevant parameters
0055 are practically the same. So there are two types of corrections:
0056 for ME1/1 chambers and for non-ME1/1 chambers. All are encoded in
0057 HardCodedCorrectionInitialization.cc.
0058
0059 <table border=0 width=100%>
0060 <tr>
0061 <td align=center><b>Status :</b></td>
0062 <td align=center>
0063 </td>
0064 </tr>
0065 </table>
