RECORD
MT2-reconstructed invisible momenta as spin analizers, and an application to top polarization
High Energy Physics - Phenomenology · Submitted 9 Aug 2013
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim Our method thereby provides a novel approach towards the evaluation of these observables, and towards testing t-tbar production beyond the level of the total cross section.
The compiled record
The paper's own sentences, arranged. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
Open the compiled record
The abstract, sentence by sentence
Full event reconstruction is known to be challenging in cases with more than one undetected final-state particle, such as pair production of two states each decaying semi-invisibly. On the other hand, full event reconstruction would allow to access angular distributions sensitive to the spin fractions of the decaying particles, thereby dissecting their production mechanism. We explore this possibility in the case of Standard-Model t-tbar production followed by a leptonic decay of both W bosons, implying two undetected final-state neutrinos. We estimate the t and tbar momentum vectors event by event using information extracted from the kinematic variable MT2. The faithfulness of the estimated momenta to the true momenta is then tested in observables sensitive to top polarization and t-tbar spin correlations. Our method thereby provides a novel approach towards the evaluation of these observables, and towards testing t-tbar production beyond the level of the total cross section. While our discussion is confined to t-tbar production as a benchmark, the method is applicable to any process whose decay topology allows to construct MT2.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Full event reconstruction is known to be challenging in cases with more than one undetected final-state particle, such as pair production of two states each decaying semi-invisibly. | background 0.99 | 0.05 | 0.02 | asserted 1.00 |
| s1 | On the other hand, full event reconstruction would allow to access angular distributions sensitive to the spin fractions of the decaying particles, thereby dissecting their production mechanism. | background 0.87 | 0.05 | 0.05 | asserted 0.57 |
| s2 | We explore this possibility in the case of Standard-Model t-tbar production followed by a leptonic decay of both W bosons, implying two undetected final-state neutrinos. | contribution 0.80 | 0.51 | 0.04 | asserted 0.88 |
| s3 | We estimate the t and tbar momentum vectors event by event using information extracted from the kinematic variable MT2. | method 0.99 | 0.94 | 0.08 | asserted 0.97 |
| s4 | The faithfulness of the estimated momenta to the true momenta is then tested in observables sensitive to top polarization and t-tbar spin correlations. | method 0.89 | 0.91 | 0.10 | asserted 0.93 |
| s5 | Our method thereby provides a novel approach towards the evaluation of these observables, and towards testing t-tbar production beyond the level of the total cross section. | interpretation 0.59 | 0.82 | 0.67 | asserted 0.92 |
| s6 | While our discussion is confined to t-tbar production as a benchmark, the method is applicable to any process whose decay topology allows to construct MT2. | limitation 0.66 | 0.32 | 0.12 | asserted 0.79 |
What was examined, and what was not
- arXiv listing abstract v2
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
- T body sentences
- C citations
- R cross-paper relations
The paper
Original abstract
Full event reconstruction is known to be challenging in cases with more than one undetected final-state particle, such as pair production of two states each decaying semi-invisibly. On the other hand, full event reconstruction would allow to access angular distributions sensitive to the spin fractions of the decaying particles, thereby dissecting their production mechanism. We explore this possibility in the case of Standard-Model t-tbar production followed by a leptonic decay of both W bosons, implying two undetected final-state neutrinos. We estimate the t and tbar momentum vectors event by event using information extracted from the kinematic variable MT2. The faithfulness of the estimated momenta to the true momenta is then tested in observables sensitive to top polarization and t-tbar spin correlations. Our method thereby provides a novel approach towards the evaluation of these observables, and towards testing t-tbar production beyond the level of the total cross section. While our discussion is confined to t-tbar production as a benchmark, the method is applicable to any process whose decay topology allows to construct MT2.
Human review
How the literature uses it
10 arXiv papers cite this in 16 sentences
Papers citing it · 13 sentences without a confident label
Uses its method or tool 1 paper
-
While it is possible to use the $M_T2$ observable [ref] to address this issue [ref] , it is still useful to construct observables that do not rely on any such rest frame reconstruction.
Measuring Electroweak Quantum Numbers of Color Sextet Resonances at the LHC · Introduction · 0.81
Cites it as background 2 papers
-
Often the minimum of the function itself becomes a useful kinematic variable — some well-known examples include the Cambridge $M_T2$ variable [ref] and its variants [ref] , the $√(s)_min$ variable [ref] , a variety of constrained transverse mass variables [ref] , the $M_CT2$ variable [ref] , the $M_2C$ variable [ref] , the MAOS method [ref] , the $M_2$ class of variables [ref] , etc.
Kinematic Focus Point Method for Particle Mass Measurements in Missing Energy Events · Introduction · 0.87
-
In fact, it was precisely the diagram of Fig. [ref](d) which initially motivated a large number of now popular kinematic variables and techniques, including the Cambridge $M_T2$ variable [ref] and its variants [ref] , the contransverse mass $M_CT$ [ref] , the $M_CT2$ variable [ref] , the MAOS method [ref] , and many others.
Singularity Variables for Missing Energy Event Kinematics · Two decay chains, each with one two-body decay · 0.86
What it cites · 49 sentences without a confident label
Uses the method or tool of 7 papers
-
This error can be straightforwardly addressed by implementing the four ($2$-based) test variables proposed in [ref] .[ For another $2$-based technique to address the same problem see [ref] .] We find that the method correctly assigns the two $bℓ$ pairs in 83% of the events, before any cut.
Reducing combinatorial uncertainties: A new technique based on MT2 variables · Top polarization from angular variables · 1.00
-
This error can be straightforwardly addressed by implementing the four ($2$-based) test variables proposed in [ref] .[ For another $2$-based technique to address the same problem see [ref] .] We find that the method correctly assigns the two $bℓ$ pairs in 83% of the events, before any cut.
Revisiting Combinatorial Ambiguities at Hadron Colliders with MT2 · Top polarization from angular variables · 1.00
-
As a practical approximation to this basis, Ref. [ref] suggests to use the helicity (off-diagonal) basis in the $βγsinθ< 1$ ($> 1$) region.
Spin Correlation Effects in Top Quark Pair Production at the LHC · MAOS-reconstructed spin correlations in a boost-dependent basis · 0.89
Uses data or values from 3 papers
-
In this respect, it should be noted that, while for $βγsinθ< 1$ like-helicity $gg$ pairs clearly dominate the cross section ($gg_like : gg_unlike = 55% : 20%$), for $βγsinθ> 1$ unlike-helicity $gg$ pairs dominate the cross section only slightly ($gg_unlike : gg_like = 15% : 10%$) [ref] .
Spin Correlation Effects in Top Quark Pair Production at the LHC · MAOS-reconstructed spin correlations in a boost-dependent basis · 0.96
-
From the recent Atlas analysis [ref] , we conservatively take these cuts to be $p_ > 20$ GeV and $|η| < 2.5$, applied to all final states.[This choice is rather qualitative also because the analysis [ref] refers to 7 TeV data.
Observation of spin correlation in ttbar events from pp collisions at sqrt(s) = 7 TeV using the ATLAS detector · Top polarization from angular variables · 0.96
-
Most notably, this is true for the LHC that, in 2011 alone, has produced as many as $8 ·10^5$ $t t̅$ pairs per experiment [ref] .
Top Quark Physics at the LHC: A Review of the First Two Years · Introduction · 0.93
Cites as background 8 papers
-
Before this literature, the idea of $2$ as the boundary of the physical region in the $(m_X, m_Y)$ plane had been used more or less implicitly in [ref] . ] In other words, event momenta fulfilling this relation will correctly satisfy the available kinematic constraints.
Mass Determination of New States at Hadron Colliders · Introduction · 0.85
-
Before this literature, the idea of $2$ as the boundary of the physical region in the $(m_X, m_Y)$ plane had been used more or less implicitly in [ref] . ] In other words, event momenta fulfilling this relation will correctly satisfy the available kinematic constraints.
M_T2-assisted on-shell reconstruction of missing momenta and its application to spin measurement at the LHC · Introduction · 0.85
-
The $2$ variables calculated from systems other than the full system are usually referred to as sub-system $2$ [ref] .
Using Subsystem MT2 for Complete Mass Determinations in Decay Chains with Missing Energy at Hadron Colliders · MAOS momenta in di-leptonic $t t̅$ decays · 0.86
Discussion
Know something about this paper? Leave a comment, or highlight any passage above to comment on it.