Data sample and selection criteria

In this study we used data taken with the HIGH_PT_ELECTRON18 trigger from Mar.2002 to Jul.2003 (Run# 141544 $\sim$ 163527) which correspond to an integrated luminosity of 127.7 $\pm$ 7.5 pb$^{-1}$. The trigger selection requires a high $E_T$ electron (18 GeV) in the central region ($\vert\eta\vert\le 1.1$) of the detector. To select a ``good central electron'' data sample we require that at least one electron in each event pass the tight electron cuts described in table 1.

To keep electron activity independent of any hard hadronic activity, the selected electron is required to be separated in space from the closest reconstructed jet such that $\Delta R = \sqrt{\Delta \eta^2 + \Delta\phi^2}\ge 0.52$. The physical motivation for this cut is to reduce the sensitivity of some of the electron identification variables to the jet activity in the $W\to e\nu$ events. To select a W boson each event is required to have a corrected missing transverse energy greater than 30 GeV. Finally an event veto is applied to reduce the $Z^0\to e^+ e^-$ contamination. After all these requirements the W sample contains 54,799 candidates with an estimated purity of about 95%. Events passing the W selection are then classified according to the jet multiplicity.

Jets are reconstructed with the cone algorithm (JetClu). The jet energy is corrected using the official CDF jet correctons to the parton energy. Jet are selected using the following criteria:

$$E_T \ge 15 ~GeV; ~~~\vert\eta_{det}\vert\le 2.4; ~~~R_{cone} = 0.4$$

Table 1: Number of events in each step of the W$\rightarrow$ $e\nu$ selection. (.ps)

Electron Cuts:	Events	fraction
Central Region ($\vert\eta_{D}\vert$ $<$ 1.1)	2,329,179	1.00
$\vert Z_{0}\vert$ $<$ 60 cm	2,206,974	0.947
Fiducial Region	2,053,448	0.881
$E_{T}$ $>$ 20 GeV	1,562,666	0.671
$P_{T}$ $>$ 10 GeV	1,420,638	0.610
Had/EM $<$ 0.055+0.00045 $\times$ E	1,088,553	0.467
E/P $<$ 2.0 or $E_{T}$ $>$ 50 GeV	775,879	0.333
-3.0 cm $<$ $Q_{e}$ $dx$ $<$ 1.5 cm	748,848	0.321
$\vert dz\vert$ $<$ 3.0 cm	716,019	0.307
Strip $\chi^{2}$ $<$ 10	559,756	0.240
$L_{shr}$ $<$ 0.2	509,420	0.219
Track segment	479,018	0.206
Isolation(0.4)	271,774	0.117
Conversion removal	152,399	0.065
$\Delta R_{ej}>0.52$	151,220	0.065
W selection Cuts:
Missing $E_{T}$ $>$ 30 GeV	55,304	0.025
Z removal (75 GeV $<$ $M_{ee}$ $<$ 105 GeV)	54,799	0.023
W candidates:	54,799	0.023

Table 2: Number of inclusive events in each jet multiplicity bin. The first row shows the event yield with the statistical error; in the last two rows is reported the systematic fluctuation due to the jet energy scale. (.ps)

Jet multiplicity	$\geq$ 0	$\geq$ 1	$\geq$ 2	$\geq$ 3	$\geq$ 4	$\geq$ 5	$\geq$ 6
Central	54799$\pm$ 234	11615$\pm$ 96	2680$\pm$ 50	602$\pm$ 24	145$\pm$ 12	36$\pm$ 6	12$\pm$ 3
syst. Up	--	+1818	+708	+236	+71	+23	+7
syst. Down	--	-1552	-519	-145	-43	-12	-5

Figure 1: Jet transverse energy distribution for all the jets found in the W$\to e\nu$ sample.

Figure 2: Jet transverse energy distribution for all the jets found in the W$\to e\nu$ sample.