Mass methods
From Wiki Les Houches 09
Variable/Method | Reference(s)/Code | Realm of Applicability | Precision | Good for | Fails for | Unknown/Future directions |
---|---|---|---|---|---|---|
MT | (ancient) | one missing particle | ||||
Meff | hep-ph/9610544[1], hep-ph/0006276[2] | Discovery of NP with massive particles. | Bad, quoted to be 20%-50% on masses in references, but needs to be interpreted in a specific model. | Discovery above SM contribution and estimating mass scale of particles with dominant cross section. | Does not identify process, but gives some information on particle content of dominant topologies. | |
HT | always | does not identify process in any way | ||||
Edges | hep-ph/9610544[3] (lots) | Cascade decay chains. Gives one relationship between NP masses per pair of visible final state particles. | Quoted as 4% on LSP in fast simulation pheno study of SPS1a, hep-ph/0410303 [4] | Mass differences in leptonic decays. | Dependence on absolute mass scale is weak. Can be fooled by false solutions. | Intermediate 3-body decays? Combinatoric (other side) jets not considered. Calorimeter nonlinearity? |
MT2 | hep-ph/9906349[5] | |||||
MT2 kink ("stransverse" mass) | arXiv:0709.0288[6] | 4-body final state, 2 missing | large mass differences and large pT | small mass differences or no pT | ||
MTn | 4-body final state, n missing | |||||
MTgen | arXiv:0708.1028[7] | |||||
M2C | arXiv:0712.0943[8] | |||||
M3C | arXiv:0811.2138[9] | |||||
arXiv:0812.1042[10] | ||||||
Exactly-constrained Polynomials | arXiv:0707.0030[11] | 4 on-shell intermediate resonances, 2 missing | Apply to squark-neutralino2-slepton-neutralino1 cascade where other side is squark-neutralino1. | |||
Multi-event Polynomial intersection | arXiv:0802.4290[12] | 5 or more on-shell intermediate resonances, 2 missing | Statistics of histograms created with n-event subsets; If mass differences are fixed and the masses are increased, what happens? (Sabine Kraml); Develop methods for asymmetric chains and < 6 intermediate resonances. | |||
"Wedgebox" techniques | arXiv:0802.0022 |
- How can we define "Precision" in a manner that lets us meaningfully compare different methods? A lot of process-specific assumptions and backgrounds usually enter the application of each method.
- In general, all methods need to be systematically tested in cases where the assumptions needed for the method are not satisfied.
- Appropriate consideration of ISR/FSR jets is not usually considered. Requires 2->3 matrix elements where the hard scattering process includes a possible extra hard quark/gluon radiation.
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Outcome
- Models to be studied
SUSY at SPS1a (Sezen), UED at SPS1a (Tommaso), U(1)_B-L (Lorenzo) for event generation
- Signatures
3 lepton + MET
2 lepton + MET
2 lepton + 2 jets + MET
2 lepton + 4 jet (+ MET) OR 4 lepton + 2 jets + MET
4 lepton + MET
- Methods
polynomial: Sezen, (Bob)
MT2: Chris + Monoranjan
Meff + sqrt(s)_min: Jean-Raphael + Asesh
Edges: Tania
MT: Lorenzo
- Event samples
- Parton level, no shower, no hadronization, no detector
- Parton level, no shower, no hadronization, no detector, 1 extra hard jet
- Parton level + shower + hadronization + detector
- Data storage
at Cern (people at Cern)
- Deadlines (preliminary)
data generation until mid august
results mid november