Using sorted invariant mass variables to evade combinatorial ambiguities in cascade decays
The classic method for mass determination in a SUSYlike cascade decay chain relies on measurements of the kinematic endpoints in the invariant mass distributions of suitable collections of visible decay products. However, the procedure is complicated by combinatorial ambiguities: e.g., the visible final state particles may be indistinguishable (as in the case of QCD jets), or one may not know the exact order in which they are emitted along the decay chain. In order to avoid such combinatorial ambiguities, we propose to treat the nal state particles fully democratically and consider the sorted set of the invariant masses of all possible partitions of the visible particles in the decay chain. In particular, for a decay to N visible particles, one considers the sorted sets of all possible nbody invariant mass combinations (2≤ n≤ N) and determines the kinematic endpoint m _{(n,r)} ^{max} of the distribution of the rth largest nbody invariant mass m _{(n,r)} for each possible value of n and r. For the classic example of a squark decay in supersymmetry, we provide analytical formulas for the interpretation of these endpoints in terms of the underlying physical masses. We point out that these measurements can be used to determinemore »
 Authors:

^{[1]};
^{[1]};
^{[2]}
 Univ. of Florida, Gainesville, FL (United States). Physics Dept.
 Inst. of Basic Science, Daejeon (Korea, Republic of). Center for Theoretical Physics of the Universe
 Publication Date:
 Grant/Contract Number:
 SC0010296; PHY0969510
 Type:
 Accepted Manuscript
 Journal Name:
 Journal of High Energy Physics (Online)
 Additional Journal Information:
 Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2016; Journal Issue: 2; Journal ID: ISSN 10298479
 Publisher:
 Springer Berlin
 Research Org:
 Univ. of Florida, Gainesville, FL (United States)
 Sponsoring Org:
 USDOE Office of Science (SC); National Science Foundation (NSF)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Deep Inelastic Scattering (Phenomenology)
 OSTI Identifier:
 1327246
Kim, Doojin, Matchev, Konstantin T., and Park, Myeonghun. Using sorted invariant mass variables to evade combinatorial ambiguities in cascade decays. United States: N. p.,
Web. doi:10.1007/JHEP02(2016)129.
Kim, Doojin, Matchev, Konstantin T., & Park, Myeonghun. Using sorted invariant mass variables to evade combinatorial ambiguities in cascade decays. United States. doi:10.1007/JHEP02(2016)129.
Kim, Doojin, Matchev, Konstantin T., and Park, Myeonghun. 2016.
"Using sorted invariant mass variables to evade combinatorial ambiguities in cascade decays". United States.
doi:10.1007/JHEP02(2016)129. https://www.osti.gov/servlets/purl/1327246.
@article{osti_1327246,
title = {Using sorted invariant mass variables to evade combinatorial ambiguities in cascade decays},
author = {Kim, Doojin and Matchev, Konstantin T. and Park, Myeonghun},
abstractNote = {The classic method for mass determination in a SUSYlike cascade decay chain relies on measurements of the kinematic endpoints in the invariant mass distributions of suitable collections of visible decay products. However, the procedure is complicated by combinatorial ambiguities: e.g., the visible final state particles may be indistinguishable (as in the case of QCD jets), or one may not know the exact order in which they are emitted along the decay chain. In order to avoid such combinatorial ambiguities, we propose to treat the nal state particles fully democratically and consider the sorted set of the invariant masses of all possible partitions of the visible particles in the decay chain. In particular, for a decay to N visible particles, one considers the sorted sets of all possible nbody invariant mass combinations (2≤ n≤ N) and determines the kinematic endpoint m(n,r)max of the distribution of the rth largest nbody invariant mass m(n,r) for each possible value of n and r. For the classic example of a squark decay in supersymmetry, we provide analytical formulas for the interpretation of these endpoints in terms of the underlying physical masses. We point out that these measurements can be used to determine the structure of the decay topology, e.g., the number and position of intermediate onshell resonances.},
doi = {10.1007/JHEP02(2016)129},
journal = {Journal of High Energy Physics (Online)},
number = 2,
volume = 2016,
place = {United States},
year = {2016},
month = {2}
}