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eta_c results with event mixing [message #12852]

Fri, 09 December 2011 13:37

Dima Melnychuk
Messages: 213
Registered: April 2004
Location: National Centre for Nucle...

first-grade participant

From: *fuw.edu.pl

Hi,

With available "mixed data" 391 subjobs by 250 events, i.e. around 100 k I have the following results for eta_c reconstruction.

Starting with multiplicity of reconstructed tracks, it's obviously higher than for signal only.

index.php?t=getfile&id=6744&private=0

Invariant mass for eta_c and phi without cuts.
index.php?t=getfile&id=6745&private=0

Here eta_c peak seats on large combinatorial background.

After all the cuts mass looks like:
index.php?t=getfile&id=6746&private=0

Efficiency of eta_c reconstruction 11.6% vs 27.3% for signal only and 19.1% for signal plus clean-up. Resolution sigma(eta_c)=18.6 MeV and sigma(phi)=4.20 MeV is close to the "non-mixed" case.

Another question arises how results look like without MC PID and how PID is relevant for this study.

Final invariant mass plot:
index.php?t=getfile&id=6747&private=0

Here phi mass distribution has much higher tails from combinatoric and eta_c reconstruction efficiency is 9.6% vs 11.6% applying MC PID.

Dima

Attachment: etac_ncharged_stt_mix.png
(Size: 11.89KB, Downloaded 858 times)
Attachment: etac_m_nocuts_stt_mix.png
(Size: 13.18KB, Downloaded 839 times)
Attachment: etac_m_final_vtx_stt_mix.png
(Size: 13.77KB, Downloaded 883 times)
Attachment: etac_m_final_vtx_stt_mix_nopid.png
(Size: 13.11KB, Downloaded 995 times)

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