Determination of the number of light neutrino species

1
Determination of the number of light neutrino
species

• Takahiro Honda

2
AlEPH in LEP
3
ALEPH???

• Z????????????????????
• ????
• ??????
• ??????
• TPC
• ????????
• ??????
• ??????????
• ??????????

4
???????

• ??????
• ???????????
• ??????
• ??????????????????????
• TPC(Time Projection Chamber)
• ?????????
• ????????
• ??????????????
• ??????????
• ?????????????
• ??????????
• ??????????

5
??????

• Performance
• s_rF 150 µm
• s_z7 cm

6
Time Projection Chamber

• Performance
• rF resolution 180µm
• z resolution 1.2mm (wires) ,0.8mm (pads)
• dE/dx resolution 4.5
• Momentum resolution
• TPC only 1.2x10-3 (c/GeV)
• ITC TPC 0.8x10-3 (c/GeV)

7
????????

• Gas
• Xe,CO2 (80 20)
• Performance
• Energy resolution s/E 0.010.18/vE(GeV)
• Angular resolution s_F0.322.7/vE mrad

8
??????????

• Gas
• Ar, CO2, Isobutane (12.5 56.5 30)
• Performance
• Energy resolution s/E 84/vE

9
TPC???

• r ??????????????????????????????????????????
• F ????????????????????????????????????
• Z ???????????Z??????.
• ?????? ?????????????????????????????????????????
  ?????????dE/dx???????

10
TPC??????

• TPC?????????????????????????????????
• ??????(dE/dx)????????????????????????????????????
  ????
• ??????????????dE/dx???????????????????????????????
  ?????
• ???????????????????????????????????????????

11
???????

• TPC(????????)
• ?????5
• ??????????????????10
• Polar angle ?18.2??
• ??????(????t????)
• ?????????20GeV??
• ECAL??????????????6GeV???????????????1.5GeV??
• ??????????????

12
Z?????????????

• LEP??????????????????????Z??????????????????
• ??????Z????????????????????TPC????????????????????
  ????????
• Z????????Z?????????????????????????????
• ??Z???????????????????????????????????????????

13
???

• ???????????4???????98???????????????????????3????
  ????????
• ???????????????????????Z?1/2??????????????????????
  ?4???????????????????????

14
sphericity

• ?????????????????????????????

I1
Jet???? ???????????????????
I3
???????????????????????????????Imin????
I2
S0?????????S1??????????????????