LHCb-light Meeting –June, 18th 2002 Frédéric MACHEFERT1

Laboratoire de l’Accélérateur Linéaire (IN2P3-CNRS) Orsay, France

Effect of M1-thicknessEffect of M1-thickness

LHCb-light meetingTuesday, June 18th 2002

LHCb-light Meeting –June, 18th 2002 Frédéric MACHEFERT2

Laboratoire de l’Accélérateur Linéaire (IN2P3-CNRS) Orsay, France

14.4 % X14.4 % X00• MC Sample

• Figures based on 17000 B0 0

• LHCb-light as of v241• Brunel v9r1

• 0 MC considered: pt(0)>500MeV and no merged case

• selection• :

• pt()>200MeV• EPRS > 4 MeV• ESPD veto

• 0 Rec : pt(0)>500MeV0 0 e+e- 0 e+e-

(zconversion > 8m)

# 0 30944 (42.3%)

36365 (45.5%)

Not seen

14.4% 76.7% 51.9%

Seen 85.6 23.3% 48.1%Efficienc

y17.6% 17.2% 17.9%

Purity 14.2% 2.8% 2.8%

(P( e+e- )~35 %)• e+e- :

• pt(e+e-)>200MeV• EPRS > 10 MeV• ESPD

Out of the sweeping region:0 : =21.1% =19.4% 0 e+e-: =20.1%

=5.8%

LHCb-light Meeting –June, 18th 2002 Frédéric MACHEFERT3

Laboratoire de l’Accélérateur Linéaire (IN2P3-CNRS) Orsay, France

Signal - NoiseSignal - Noise

49.5%

30%

42.3%

45.5%

65% 55%

0 0 e+e-

Efficiency Evolution with respect to X0

LHCb-light Meeting –June, 18th 2002 Frédéric MACHEFERT4

Laboratoire de l’Accélérateur Linéaire (IN2P3-CNRS) Orsay, France

X0 variationsX0 variations