Difference between revisions of "Invisible decay"
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<td>[[File:Ratio of no photon all events.png|thumb|600px|left|Ratio of the events of no photon detected to all events (red) and expected events to all events (blue)]]</td> | <td>[[File:Ratio of no photon all events.png|thumb|600px|left|Ratio of the events of no photon detected to all events (red) and expected events to all events (blue)]]</td> | ||
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| + | <td>[[File:Missing mass of proton all 2014822.png|thumb|400px|left|Compare the events of no photon detected with expected from acceptance for all events with PART bank]]</td> | ||
| + | <td>[[File:Ratio of no photon all 2014822.png|thumb|400px|left|Ratio of the events of no photon detected to all events (red) and expected events to all events (blue) with PART bank]]</td> | ||
| + | </tr> | ||
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| + | <td>[[File:Missing mass of proton 5 2014822.png|thumb|400px|left|Compare the events of no photon detected with expected from acceptance larger than 50% with PART bank]]</td> | ||
| + | <td>[[File:Ratio of no photon 5 2014822.png|thumb|400px|left|Ratio of the events of no photon detected (red) and expected events (blue) to acceptance larger than 50% with PART bank]]</td> | ||
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Revision as of 12:28, 22 August 2014
Idea
B(inivisible)/B(normalization)={N(upper limit)/efficiency(invisible)}/{N(normalization)/efficiency(normalization)} * {1/(1-sigma)}
- B(inivisible): branching ratio of the invisible decay
- B(normalization): branching ratio of the reference channel
- N(upper limit): upper limit of the yield of the invisible decay
- N(normalization): yield of the reference channel
- efficiency(invisible): acceptance of the invisible decay
- efficiency(normalization): acceptance of the reference channel
- sigma: systematic uncertainty
What applies here:
The channel we are using is : gamma p -> p eta_prime -> p pi+ pi－ （eta). The invisible decay of eta is eta -> xx. x is something like U boson, which could be dark photon or heavy photon.
B(normalization) is 1 when we obtain eta by requiring the missing mass.
efficiency(invisible)=efficiency(normalization) * efficiency (invisible decay of eta). efficiency(normalization) is the detection efficiency of p pi+ pi-. efficiency(invisible) is the product of efficiency(normalizaiton) and efficiency(invisible decay of eta). efficiency(invisible decay) is the detection efficiency of at least one photon from eta decay.
photon detection efficeincy
procedure
- collection events of p, pi+, pi- and one or two photons
- requiring the missing mass of p pi+ pi- to be pi0
- requiring the missing mass of p to be eta or omega
- events passing the above three conditions are called "all" events
- two-photon events are called "good" events
- the ratio of "good" events to "all" events is the detection efficiency of photon
- the ratio is binned in energy, theta, and phi angle in lab frame
result
Eta acceptance
partial statistics
The following is from 2% of the data.
Different efficiency
Compare expected and no-photon detected
Reference
arxiv:1209.2469
