# Mass methods

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]
$\sqrt{s}_{min}$ arXiv:0812.1042[10] See also Eq.5 of arXiv:0902.4864 and Eq.53 of hep-ph/0508097 which may be the same. (thanks K.C. Kong)
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.

###### ============================================================================================================================

Outcome

• Models to be studied

SUSY at SPS1a (Sezen), UED at SPS1a (Tommaso), U(1)_B-L (Lorenzo) for event generation

Technicolor (Sasha; see separate point below)

• 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 (S.Moretti and A.Belyaev are happy to collaborate)

• 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

question 1): which generator should be used for 2->3 ?? herwig cannot do this

question 2): what about delphes validation ?? sezen works on it

• Parton level cuts (open to discussion)

- Pt: Generic Pt > 20 GeV on all objects including EtMiss

- Eta: eta cut is usually very detector dependent. Which part of the detector can be trusted for which object, excluding "crack region", ... There is also how close to beam pipe you can detect things. So to keep thing simple I would vote to have only a cut on Eta max independently of the objects.

• Data storage

at Cern (people at Cern)

data generation until mid august

results mid november

• Technicolor model

by A. Belyaev

possible signatures (partly in accordance w above):

A) 1 lepton + ETmiss

B) 1 lepton + ETmiss + jets

C) 2 leptons + ETmiss

D) 2 leptons + ETmiss + jets

E) 3 leptons + ETmiss

F) 4 leptons + ETmiss

Sasha plans to apply basically all methods on this model by himself but is happy to share data and knowledge