First Year of BABAR/PEP-II - Harvard University Laboratory for ...
First Year of BABAR/PEP-II - Harvard University Laboratory for ...
First Year of BABAR/PEP-II - Harvard University Laboratory for ...
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Inclusive J/ψ Reconstruction<br />
<strong>First</strong> step: Find J/ψ →l + l − decays.<br />
1.Select b-like events with R 2 < 0.5. (Fox-Wolfram moment ratio W 2 /W 0 )<br />
2. Combine 2 oppositely-charged tracks.<br />
3. Form a vertex with P(χ 2 ) > 1%.<br />
4. Very loose lepton ID.<br />
Monte Carlo signal: σ(m) = 11 MeV/c 2 .<br />
Candidates / 10 MeV/c 2<br />
100<br />
75<br />
50<br />
J/ψ → e + e - m(e + e - )<br />
e + e −<br />
<strong>BABAR</strong><br />
Candidates / 10 MeV/c 2<br />
150<br />
100<br />
J/ψ → µ + µ -<br />
µ + µ −<br />
<strong>BABAR</strong><br />
25<br />
50<br />
0<br />
2.6 2.8 3 3.2 3.4<br />
m(e + e - )<br />
GeV/c 2<br />
0<br />
2.6 2.8 3 3.2 3.4<br />
m(µ + µ - )<br />
GeV/c 2<br />
◆ Large tail in the e + e − channel due to bremstrahlung.<br />
<strong>First</strong> <strong>Year</strong> <strong>of</strong> BaBar/<strong>PEP</strong>-<strong>II</strong> Masahiro Morii SLAC
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